WO2010058356A2

WO2010058356A2 - Valves for gas-turbines and multipressure gas-turbines, and gas-turbines therewith

Info

Publication number: WO2010058356A2
Application number: PCT/IB2009/055154
Authority: WO
Inventors: David Lior
Original assignee: Etv Motors Ltd.
Priority date: 2008-11-20
Filing date: 2009-11-18
Publication date: 2010-05-27
Also published as: WO2010058356A3; US20110262269A1; IL212740A0

Abstract

Disclosed are multiport valves for use with a gas-turbine configured for operation according to both Brayton-cycle and inverse-Brayton cycle, comprising movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port (152), an ambient inlet port (151), a heat-exchanger cold-stream inlet outlet port (162), an exhaust outlet port (163), and a fifth port.

Description

VALVES FOR GAS-TURBINES AND MULTIPRESSURE GAS-TURBINES, AND

GAS-TURBINES THEREWITH

RELATED APPLICATION

The present application gains priority from U.S. Provisional Patent Application No. 61/116,394 filed 20 November 2008 which is included by reference as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments, relates to the field of gas-turbines, and more particularly, but not exclusively, to gas-turbines operable in both high-pressure (Brayton cycle) and low-pressure (inverse Brayton cycle) modes. The present invention, in some embodiments, relates to the field of gas-turbines, and more particularly, but not exclusively, to gas-turbines operable in low-pressure mode (inverse Brayton cycle).

Gas-turbines are known for being lightweight, reliable and requiring little maintenance compared to alternative work-producing motors, e.g. an internal combustion engine (ICE). Above all, gas-turbines are known for efficiently converting chemical energy stored in a combustible fuel to mechanical energy when working at an optimum work point. However, in spite of their potential, gas-turbines are currently not well known in applications requiring work-producing motors - for example ground vehicles such as cars and trucks - for several reasons.

One reason is that a given gas-turbine may generate a certain power at high efficiency for a prescribed load, but is less efficient at part load, particularly if turbine speed is maintained. Many applications, vehicular applications in particular, generally have changing power demands, for instance requiring more power for rapid acceleration or climbing hills, and requiring less power when driving in traffic.

A second reason is "turbine lag": it takes a noticeably long time for a given gas-turbine to speed-up to produce more power, e.g., for acceleration. Thus, if turbine speed is reduced when power demand is low, a sudden increased power demand can be met only after a noticeable time lag. A third reason is that the lifetime of gas-turbines is severely limited by startup/shutdown events. Unlike an ICE, it is not practical to shut down a gas-turbine when idling

A fourth reason is that the power requirements for many applications, e.g. ground vehicles, are low compared to the power gas-turbines efficiently produce. Although large gas- turbines are relatively efficient, the efficiency of a gas-turbine decreases with smaller size (less than 300 kW) for various reasons including leakage around the periphery of the turbine which is increasingly significant with smaller turbine size.

Commonly, gas-turbines are operated according to either a high-pressure Brayton 5 cycle or a low-pressure inverse Brayton cycle. A gas-turbine operating according to the inverse Brayton cycle efficiently produces less power than a similar-sized gas-turbine operating according to the Brayton cycle. In Figure IA a gas-turbine 2 in a typical Brayton cycle operation, and in Figure IB a gas-turbine 4 in a typical inverse Brayton cycle operation, are schematically depicted. Both gas-turbines 2 and 4 comprise a compressor 20 and a turbine

10 22, together mounted on a common rotatable shaft 24 constituting a spool, a combustor 26, an air inlet 28 and an exhaust outlet 30. One end of shaft 24 constitutes the rotor of a generator 32. Gas-turbines 2 or 4 and generator 32 together with other components such as a fuel-supply unit 34 and a gas-turbine controller 36 constitute a power generation unit 38.

In typical high-pressure (Brayton-cycle) operation, Figure IA, ambient air is drawn

15 through air inlet 28 into a compressor inlet (low-pressure port) 40, and forced by compressor 20 through a compressor outlet (high-pressure port) 42 into a combustor inlet 44. In combustor 26, the air is mixed with fuel and the mixture combusted. The hot exhaust gases resulting from the combustion are directed through a combustor outlet 46 into a turbine inlet 48. The hot exhaust gases expand through and rotate turbine 22, consequently rotating shaft

20 24 and compressor 20 before exiting turbine 22 through a turbine outlet 50, to be released to the surroundings through exhaust outlet 30.

In typical low-pressure (inverse Brayton-cycle) operation, Figure IB, ambient air is drawn into combustor 26 through air inlet 28 and through combustor inlet 44. In combustor 26 the air is mixed with fuel and the mixture combusted. The hot exhaust gases resulting from

25 the combustion are directed into turbine 22 through turbine inlet 48. The hot exhaust gases expand through and rotate turbine 22, consequently rotating shaft 24 and compressor 20. The hot exhaust gases are then drawn into compressor inlet 40 and forced by compressor 20 through compressor outlet 42 and through exhaust outlet 30 to be released to the surroundings.

30 In both the Brayton cycle and inverse Brayton cycle, the rotation of shaft 24 by exhaust gases expanding through turbine 22 provides usable mechanical work, e.g. for generation of electric power by generator 32. Gas-turbines such as 2 or 4 typically include gas-turbine controller 36 that monitors and controls the gas-turbine, including by regulating the amount of fuel supplied to combustor 26 by fuel- supply unit 34.

To increase thermal efficiency, gas-turbines such as 2 or 4 typically include a heat- exchanger 52, such as a recuperator or regenerator. Heat-exchanger 52 includes a cold- stream conduit 54 and a hot-stream conduit 56, both having inlets 58 and 60, respectively, and outlets 62 and 64, respectively. Heat-exchanger 52 increases the thermal efficiency of a gas-turbine by recovering heat from hot exhaust gases passing through hot-stream conduit 56 to preheat air passing through cold-stream conduit 54 prior to entering combustor 26. In US Patent Nos. 6,526,757 and 6,606,864 both of McKay are provided multipressure mode gas-turbines, gas-turbines with valving having two configurations. In a first valving configuration the gas-turbine operates in a high-pressure mode according to a Brayton cycle. In a second valving configuration the gas-turbine operates in a low-pressure mode according to an inverse Brayton cycle. The gas-turbine is toggled between the two modes by the synchronized switching of a plurality of valves between the two valving configurations changing the pressure and therefore the mass flow through the gas-turbine while maintaining a constant temperature and shaft speed, allowing two substantially equally efficient power outputs, where the power output during low-pressure mode operation is less than during high- pressure mode operation.

SUMMARY OF THE INVENTION

Aspects of the invention relate to valves suitable for use with gas-turbines that, in some embodiments, allow switching between high-pressure and low-pressure operation modes of a gas-turbine. Aspects of the invention relate to gas-turbines that are configured to operate in both high-pressure and low-pressure modes.

Aspects of the invention relate to valves suitable for use with gas-turbines that, in some embodiments, allow switching between high-pressure, low-pressure and intermediate- pressure operation modes of a gas-turbine. Aspects of the invention relate to gas-turbines that are configured to operate in high-pressure, low-pressure and intermediate-pressure modes. Aspects of the invention relate to valves that allow simple and efficient varying of the pressure and power output of a gas-turbine, that in some embodiments is substantially continuous. Aspects of the invention relate to gas-turbines that are configured to efficiently operate in different pressure modes, allowing different power outputs at substantially similar efficiencies. According to an aspect of some embodiments of the invention, there is provided a gas-turbine configured for operation according to both Brayton-cycle and inverse-Brayton cycle, comprising: a) a multiport valve including movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port, and a fifth port; b) a compressor-outlet of a compressor of the gas-turbine in fluid communication with the compressor-outlet inlet port; and c) a heat-exchanger cold-stream inlet of a heat-exchanger of the gas-turbine in fluid communication with the heat-exchanger cold-stream inlet outlet port; wherein during Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the exhaust outlet port, and a valve member blocks fluid communication between the ambient inlet port and the heat-exchanger cold- stream inlet outlet port; and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the heat-exchanger cold- stream inlet outlet port.

According to an aspect of some embodiments of the invention there is also provided a multiport valve suitable for use with a gas-turbine and allowing switching the mode of operation of a gas-turbine between a high-pressure mode according to a Brayton cycle and a low-pressure mode according to an inverse Brayton cycle, the valve comprising: a) a valve body defining a void in the form of a plurality of fluid conduits; b) at least five ports leading to the void of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold- stream inlet outlet port, an exhaust outlet port and a fifth port; c) a first valve member inside the valve body movable between at least two positions, a first position and a second position; and d) a second valve member inside the valve body movable between at least two positions, a first position and a second position. where the position of the first valve member and the position of the second valve member (together) define fluid communication between the inlet ports and the outlet ports through the void.

According to an aspect of some embodiments of the invention, there is also provided a gas-turbine, configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising a multiport valve as described herein. In some embodiments, the gas-turbine is also configured to switch to an intermediate pressure mode between the high-pressure operation mode and the low-pressure operation mode. Aspects of the invention relate to gas-turbines operating in low-pressure mode that have reduced NOx emissions. Thus, according to an aspect of some embodiments of the invention, there is also provided a method of operating a gas-turbine according to an inverse Brayton cycle, comprising: a) providing a conduit allowing fluid communication between a compressor of the gas-turbine and a cold-stream inlet of a heat-exchanger of the gas-turbine; and b) during inverse Brayton cycle operation of the gas-turbine, directing fluid from the compressor to the heat-exchanger cold-stream inlet through the conduit so that a portion of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. As a result, inlet air is mixed with a portion of the oxygen-depleted exhaust from the compressor, decreasing oxygen content of the combustible mixture in the combustor, reducing the amount of NOx produced in the combustor and emitted by the gas-turbine.

According to an aspect of some embodiments of the invention, there is also provided a gas-turbine comprising, when operating according to an inverse Brayton cycle, a) an air inlet configured to direct fluid into a cold-stream conduit of a heat-exchanger through a cold- stream inlet; b) conduits to direct fluid from the cold-stream conduit to a combustor, from the combustor to a turbine, from the turbine to a hot- stream conduit of the heat-exchanger, from the hot- stream conduit to a compressor, and from the compressor to an exhaust outlet port; and c) a conduit allowing passage of fluid from the compressor into the cold-stream inlet of the heat-exchanger. In some embodiments, the gas-turbine is configured to operate only according to the inverse Brayton cycle. In some embodiments, the gas-turbine is a multi- power gas-turbine configured to operate according to both the Brayton cycle and the inverse Brayton cycle. According to an aspect of some embodiments of the invention, there is also provided a motor vehicle (e.g., an automobile, a light truck, a truck, a bus) comprising a gas-turbine substantially as described herein.

As used herein, the term "high-pressure mode" refers to operation of a gas-turbine where compressor inlet pressure is close to atmospheric (~1 x ambient) and compressor outlet (exhaust) pressure is superatmospheric (typically ~3 x ambient pressure).

As used herein, the term "low-pressure mode" refers to operation of a gas-turbine where compressor inlet pressure is subatmospheric (-0.3 x ambient pressure) and compressor outlet (exhaust) pressure is close to atmospheric (~1 x ambient pressure).

As used herein, the term "intermediate pressure mode" refers to operation of a gas- turbine where compressor inlet pressure is subatmospheric (between above 0.3 x ambient pressure to ~1 x ambient pressure) and compressor outlet (exhaust) pressure is higher than atmospheric (between above 1 x ambient pressure to ~3 x ambient pressure). Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the patent specification, including definitions, will control.

As used herein, the terms "comprising", "including", "having" and grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. These terms encompass the terms "consisting of" and

"consisting essentially of".

As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention are described herein, with reference to the accompanying figures The description, together with the figures, makes apparent how embodiments of the invention may be practiced to a person having ordinary skill in the art. The figures are for the purpose of illustrative discussion of embodiments of the invention and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, objects depicted in the figures are not drawn to scale.

In the Figures: FIGS. IA and IB are schematic depictions of a Brayton cycle gas-turbine (IA) and an inverse Brayton cycle gas-turbine (IB);

FIGS. 2A and 2B are schematic depictions of an embodiment of a 5-port valve suitable for use with a gas-turbine in two configurations allowing the gas-turbine to operate in a high-pressure operation mode and in a low-pressure operation mode, respectively;

FIGS. 3 A and 3B are schematic depictions of an embodiment of a gas-turbine including an embodiment of a 5-port valve of Figures 2 where the valve is in two configurations so that the gas-turbine operates in a high-pressure operation mode and in a low-pressure operation mode, respectively; FIG. 4 is of a conceptual graph qualitatively showing thermal efficiency as a function of power output of various embodiments of gas-turbines described herein;

FIGS. 5 A and 5B are schematic depictions of an embodiment of a gas-turbine including an embodiment of a 5-port valve where the valve is in two configurations allowing the gas-turbine to operate in a high-pressure operation mode and in a low-pressure operation mode, respectively;

FIGS. 6 A and 6B are schematic depictions of an embodiment of a 6-port valve suitable for use with a gas-turbine in two configurations allowing the gas-turbine to operate in a high-pressure operation mode and in a low-pressure operation mode, respectively;

FIGS. 7 A and 7B are schematic depictions of an embodiment of a gas-turbine including an embodiment of a 6-port valve of Figures 6 where the valve is in two configurations so that the gas-turbine operates in a high-pressure operation mode and in a low-pressure operation mode, respectively;

FIGS. 8 A and 8B are schematic depictions of an embodiment of a 6-port valve suitable for use with a gas-turbine in two configurations allowing the gas-turbine to operate in a high-pressure operation mode and in a low-pressure operation mode, respectively;

FIGS. 9A and 9B are schematic depictions of an embodiment of a gas-turbine including an embodiment of a 6-port valve of Figures 8 where the valve is in two configurations so that the gas-turbine operates in a high-pressure operation mode and in a low-pressure operation mode, respectively; FIG. 10 is a schematic depiction of an embodiment of a valve suitable for use with a gas-turbine, allowing the gas-turbine to operate in at least one intermediate pressure operation mode in addition to a low-pressure operation mode and a high-pressure operation mode; FIG 11 is a schematic depiction of an embodiment of a gas-turbine including an embodiment of a valve of Figure 10, where the valve is set so that the gas-turbine operates in an intermediate pressure operation mode;

FIG. 12 is a schematic depiction of an embodiment of a gas-turbine including an embodiment of a six -port valve similar to the valve depicted in Figure 10;

FIGS. 13A and 13B are schematic depictions of an embodiment of a 5-port valve useful for continuously varying the mass flow to the combustor of a gas-turbine in a high- pressure operation mode, in high and low-mass flow rate configurations, respectively;

FIGS. 14A and 14B are schematic depictions of an embodiment of a 5-port valve useful for continuously varying the mass flow to the combustor of a gas-turbine in a low- pressure operation mode, in high and low mass flow rate configurations, respectively;

FIGS. 15 A, 15B and 15C are schematic depictions of embodiments of valves useful for continuously varying the mass flow to the combustor of a gas-turbine high and low- pressure operation modes; FIG. 16 is a gas-turbine including a valve suitable for switching the gas-turbine between at least two pressure level operation modes and useful for reducing NOx emissions of the gas-turbine when in low-pressure operation mode; and

FIGS. 17 A and 17B are two embodiments of a permeable section in a multiport valve suitable for use in a gas turbine and useful for reducing NOx emissions of the gas-turbine as described herein.

DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

Some embodiments of the invention relate to multiport valves that allow switching between high-pressure operation (Brayton cycle) and low-pressure operation (inverse Brayton cycle) modes of a gas-turbine.

Some embodiments of the invention relate to multiport valves that allow operation of a gas-turbine in high-pressure, low-pressure and intermediate pressure modes.

Some embodiments of the invention relate to multiport valves that allow operation of a gas-turbine at a variable power output in high-pressure modes and/or low-pressure modes at relatively high efficiency by varying the mass flow through the gas-turbine. Some embodiments of the invention relate to valves that allow simple and efficient varying of the pressure, mass flow and power output of a gas-turbine, that in some embodiments is substantially continuous. Some embodiments of the invention relate to gas-turbines operating in a low-pressure mode (inverse Brayton mode) having reduced NOx emissions as well as valves useful for such gas-turbines.

The principles, uses and implementations of the teachings of the invention may be better understood with reference to the accompanying description and Figures. Upon perusal of the description and figures present herein, one skilled in the art is able to implement the teachings of the invention without undue effort or experimentation, including by consulting US Patent No. 6,526,757 ', which is included by reference as if fully set forth herein. In the Figures, like reference numerals refer to like parts throughout. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth herein. The invention is capable of other embodiments or of being practiced or carried out in various ways. The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting.

As noted in the introduction, in US Patent Nos. 6,526,757 and 6,606,864 are disclosed gas-turbines provided with valving that allow the gas-turbines to switch between high- pressure operation with efficient high-power output and low-pressure operation with efficient low-power output. However, a problem with the gas-turbines as described in US Patent Nos. 6,526,757 and 6,606,864 is that of complexity: the valving system of a simplest embodiment includes six separate on-off valves that must be operated synchronously to toggle between the two modes. Furthermore, in order to achieve additional, intermediate pressure - and thus intermediate power - turbine operation modes, even more complex embodiments which include more than one spool and many separate valves, must be employed. It has been found that it is possible to simplify the valving system necessary to allow a gas-turbine to switch between high-pressure and low-pressure operation.

Thus, according to an aspect of some embodiments of the invention, there is provided a gas-turbine configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising: a) a multiport valve including movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port, and a fifth port; b) a compressor outlet of a compressor of the gas-turbine in fluid communication with the compressor-outlet inlet port; and c) a heat-exchanger cold- stream inlet of a heat-exchanger of the gas-turbine in fluid communication with the heat-exchanger cold-stream inlet outlet port; wherein during Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the exhaust outlet port and a valve member blocks fluid communication between the ambient inlet port and the heat- exchanger cold-stream inlet outlet port; and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port.

In some embodiments, the fifth port is a compressor-inlet outlet port in fluid communication with an inlet of the compressor of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the ambient inlet port and the compressor-inlet outlet port. In some such embodiments, the gas-turbine further comprises an additional valve functionally associated with the hot-stream outlet of the heat-exchanger, wherein during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot- stream outlet of the heat-exchanger to an inlet of the compressor. In some such embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger to an exhaust outlet of the gas-turbine. An exemplary such embodiment is depicted in Figures 3 A and 3B.

In some embodiments, the fifth port is a heat-exchanger hot-stream outlet inlet port in fluid communication with a hot- stream outlet of the heat-exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the heat-exchanger hot- stream outlet inlet port and the exhaust outlet port. In some such embodiments, the gas-turbine further comprises an additional valve functionally associated with a hot-stream outlet of the heat-exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot- stream outlet of the heat-exchanger to an inlet of the compressor. In some embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from ambient to an inlet of the compressor. An exemplary such embodiment is depicted in Figures 5 A and 5B. In some embodiments, the multiport valve includes six ports, of which three are inlet ports and three are outlet ports.

In some such embodiments where the multiport valve includes six ports, the fifth port is a compressor-inlet outlet port in fluid communication with an inlet of the compressor, and during inverse Brayton-cycle operation of the gas-turbine a valve member blocks fluid communication between the ambient inlet port and the compressor-inlet outlet port; and the multiport valve further includes a sixth port, a heat-exchanger hot-stream outlet inlet port in fluid communication with a hot-stream outlet of the heat-exchanger of the gas-turbine.

In some embodiments including such a six-port valve, the gas-turbine further comprises an additional valve functionally associated with a hot-stream outlet of the heat- exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat- exchanger of the gas-turbine to an inlet of the compressor of the gas-turbine. In some such embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger of the gas-turbine to an exhaust outlet of the gas-turbine through the heat-exchanger hot-stream outlet inlet port. In some such embodiments, the gas-turbine further comprises a component functionally associated with the heat-exchanger hot-stream outlet inlet port, allowing flow of fluid from the hot-stream outlet of the heat-exchanger through the heat-exchanger hot-stream outlet inlet port and blocking flow of fluid from the multiport valve to the hot-stream outlet of the heat- exchanger through the heat-exchanger hot-stream outlet inlet port. In some such embodiments, the component is a undirectional valve that is part of the multiport valve. An exemplary such embodiment is depicted in Figures 7 A and 7B.

In some such embodiments where the multiport valve includes six ports, the multiport valve further comprising a bypass conduit bypassing the valve void, providing fluid communication between the heat-exchanger hot-stream outlet inlet port and the compressor- inlet outlet port, wherein during Brayton-cycle operation of the gas-turbine, a valve member blocks the fluid communication between the heat-exchanger hot-stream outlet inlet port and the compressor-inlet outlet port through the bypass conduit. An exemplary such embodiment is depicted in Figures 9 A and 9B.

According to an aspect of some embodiments of the invention there is also provided a multiport valve suitable for use with a gas-turbine and allowing switching the mode of operation of a gas-turbine between a high-pressure mode according to a Brayton cycle and a low-pressure mode according to an inverse Brayton cycle, the valve comprising: a) a valve body defining a void in the form of a plurality of fluid conduits; b) at least five ports leading to the void of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat- exchanger cold- stream inlet outlet port, an exhaust outlet port and a fifth port; c) a first valve member inside the valve body movable between at least two positions, a first position and a second position; and d) a second valve member inside the valve body movable between at least two positions, a first position and a second position where the position of the first valve member and the position of the second valve member (together) define fluid communication between the inlet ports and the outlet ports through the void.

In some embodiments, the first valve member and the second valve member are configured to cooperatively move between the first positions and the second positions. In some embodiments, the first valve member and the second valve member are configured to move independently between the first positions and the second positions.

In some embodiments, in the first position the first valve member is in contact with a first valve seat and in the second position in contact with a second valve seat. In some embodiments, in the first position the second valve member is in contact with a third valve seat and in the second position in contact with a third valve seat. As detailed hereinbelow, in some embodiments, in a first or second position a given valve member blocks fluid communication between specific ports. By blocking fluid communication is meant that the fluid communication between the ports is blocked to a sufficient degree to achieve the desired purpose (e.g., operating an associated gas-turbine in a desired mode), although there may be some leakage, for example as described below. As detailed hereinbelow, in some embodiments, in a first or second position a given valve member contacts a specific valve seat. By contacting a valve seat is meant contacting to a sufficient degree to achieve a desired purpose as described immediately herein above, for example, in some embodiments is meant "sealing contact".

In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the ambient inlet port and the fifth port, a compressor inlet outlet port; and the second valve member in the first position blocks fluid communication (through the void) between the compressor-outlet inlet port and the exhaust outlet port and in the second position blocks fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is valve 100 depicted in Figures 2 and 3.

In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the compressor-outlet inlet port and the exhaust outlet port and in the second position blocks fluid communication (through the void) between the fifth port, a heat-exchanger hot-stream outlet inlet port, and the exhaust outlet port; and the second valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold- stream inlet outlet port and in the second position blocks fluid communication (through the void) between the compressor- outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in Figures 5.

In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the ambient inlet port and the fifth port, a compressor inlet outlet port; and the second valve member in the first position blocks fluid communication (through the void) between a sixth port, a heat-exchanger hot-stream outlet inlet port, and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in Figures 6 and 7. In some embodiments, the valve further comprises a component functionally associated with the heat- exchanger hot- stream outlet inlet port , allowing flow of fluid into the void through the heat- exchanger hot-stream outlet inlet port and blocking flow of fluid from the void out through the heat-exchanger hot-stream outlet inlet port. In some such embodiments the component is a unidirectional valve (e.g., a check valve, in some embodiments located inside the valve body) configured to allow fluid to flow into the void of the valve body through the heat- exchanger hot- stream outlet inlet port but to block the flow of fluid from the valve body out through the heat-exchanger hot-stream outlet inlet port. In some embodiments, the valve further comprises a bypass conduit providing fluid communication bypassing the valve void between the heat-exchanger hot-stream outlet inlet port and the compressor inlet outlet port, and a third valve member inside the valve body movable between at least two positions, a first position and a second position, wherein in the first position the third valve member blocks fluid communication through the bypass conduit between the heat-exchanger hot-stream outlet inlet port and the compressor inlet outlet port through the bypass conduit and in the second position the third valve member blocks fluid communication through the void between the heat-exchanger hot-stream outlet inlet port and the exhaust outlet port. In some embodiments, in the first position the third valve member is in contact with a fifth valve seat and in the second position the third valve member is in contact with a sixth valve seat. An exemplary such embodiment is depicted in Figures 8. In some such embodiments, the first valve member, the second valve member and the third valve member are configured to cooperatively move between the first positions and the second positions. In some such embodiments, at least one of the first valve member, the second valve member and the third valve member is configured to move between the first position and the second position independently of at least one other of the valve members.

In some embodiments of the multiport valve at least one of the valve members is movable to at least one intermediate position between a respective first position and respective second position, thereby allowing fluid communication (through the void) between an inlet port and at least two outlet ports. In some such embodiments, at least one valve member is fashioned as an airfoil having an aerodynamic profile (generally predefined aerodynamic profile) configured to direct the flow of fluid as desired through the fluid conduits of the valve body.

In some embodiments, the second valve member is movable to at least one intermediate position, providing fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port and the exhaust outlet port. Exemplary such embodiments include valve 100, valve 102 and valve 103 depicted in Figures 10 and 11. In some such embodiments, the second valve member is movable to a plurality of such intermediate positions, allowing variation of the relative size of the path between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port to the relative size of the path between the compressor-outlet inlet port and the exhaust outlet port.

In some embodiments, the first valve member is movable to an intermediate position, providing fluid communication between the ambient inlet port and the heat-exchanger cold- stream inlet outlet port and the compressor-inlet outlet port. Exemplary such embodiments include valve 100, valve 102 and valve 103 depicted in Figures 10 and 11. In some such embodiments, the first valve member is movable to a plurality of such intermediate positions, allowing variation of the relative size of the path between the ambient inlet port and the heat- exchanger cold-stream inlet outlet port to the relative size of the path between the ambient inlet port and the compressor inlet outlet port.

In some embodiments comprising a third valve member, the third valve member is movable to an intermediate position, providing fluid communication between the heat- exchanger hot-stream outlet inlet port and the exhaust outlet port and the compressor-inlet outlet port. An exemplary such embodiment is valve 103 depicted in Figures 10 and 11. In some such embodiments, the third valve member is movable to a plurality of such intermediate positions, allowing variation of the relative size of the path between the heat- exchanger hot-stream outlet inlet port and the exhaust outlet port to the relative size of the path between the heat-exchanger hot-stream outlet inlet port and the compressor-inlet outlet port.

In some embodiments, at least one valve member is configured to vary a size of a fluid path between an inlet port and an outlet port while the valve member in the first position and/or the second position. In some embodiments, the second valve member is configured to vary a size of a fluid path between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port when in the first position. An exemplary such embodiment is depicted in Figures 13.

In some embodiments, the first valve member is configured to vary a size of a fluid path between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port when in the second position. An exemplary such embodiment is depicted in Figures 14.

In some embodiments, the multiport valve further comprises an additional valve member movable inside the valve body and, the additional valve member configured to vary a size of a fluid path between the compressor-outlet inlet port and the heat-exchanger cold- stream inlet outlet port. An exemplary such embodiment is depicted in Figure 15A and 15C. In some embodiments, the multiport valve further comprises an additional valve member movable inside the valve body and configured to vary a size of a fluid path between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in Figure 15B and 15C.

In some embodiments, the valve further comprises a permeable section between a first region and a second region of the void in the valve body, providing fluid communication between the first region and the second region. Such a permeable section may be implemented in any suitable way including a conduit, slits, pores and the like. The utility of such a permeable section is described hereinbelow. In some such embodiments, the first region is in proximity of the exhaust outlet port and in some such embodiments between the second valve member and the exhaust outlet port. In some such embodiments, the second region is in proximity of the heat-exchanger cold-steam inlet outlet port and in some such embodiments between the second valve member and heat-exchanger cold- stream inlet outlet port. In some such embodiments, the permeable section is unidirectional, allowing passage of fluid from the first region to the second region, and blocking passage of fluid from the second region to the first region. Such a unidirectional permeable section may be implemented in any suitable way including with the help of a unidirectional valve, a check valve (a unidirectional valve that functions automatically without an external control, e.g. variants of a swing check valve or reed valve) or a pump. In some embodiments, the permeable section is part of the second valve member.

According to an aspect of some embodiments of the invention, there is also provided a gas-turbine, configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising a multiport valve as described herein. In some embodiments, the gas-turbine is also configured to switch to an intermediate pressure mode between the high-pressure operation mode and the low-pressure operation mode.

Embodiment of 5-port valve suitable for use with a gas-turbine

Figures 2A and 2B depict an embodiment of a valve 100, suitable for use with a gas- turbine, in side cross-section. Valve 100 comprises a valve body 110 defining a single void in the form of a plurality of fluid conduits 120. Valve 100 further includes two inlet ports and three outlet ports: an ambient inlet port 151, a compressor-outlet inlet port 152, a compressor- inlet outlet port 161, a heat-exchanger cold-stream inlet outlet port 162 and an exhaust outlet port 163, the five ports in fluid communication one with the other through fluid conduits 120. Valve 100 further includes a first valve member 171 and a second valve member 181. First valve member 171 is movable inside valve body 110 between at least two positions: a first position, depicted in Figure 2A, in contact with a first valve seat 172 in valve body 110 blocking fluid communication between ambient inlet port 151 and heat-exchanger cold- stream inlet outlet port 162 and a second position, depicted in Figure 2B, in contact with a second valve seat 173 in valve body 110 blocking fluid communication between ambient inlet port 151 and compressor- inlet outlet port 161. Second movable valve member 181 is movable inside valve body 110 between at least two positions: a first position, depicted in Figure 2A, in contact with a third valve seat 182 in valve body 110 blocking fluid communication between compressor-outlet inlet port 152 and exhaust outlet port 163 and a second position, depicted in Figure 2B, in contact with a fourth valve seat 183 in valve body 110 blocking fluid communication between compressor-outlet inlet port 152 and heat- exchanger cold-stream inlet outlet port 162.

First movable valve member 171 is movable between the first and second positions by rotating around a first valve member axis 174. Second movable valve member 181 is movable between the first and second positions by rotating around a second valve member axis 184.

When valve members 171 and 181 are in the respective first position depicted in Figure 2A (configuration "1"), valve 100 allows an associated gas-turbine to operate in high- pressure operation mode, as is described further below. When valve members 171 and 181 are in the respective second position depicted in Figure 2B (configuration "2"), valve 100 allows an associated gas-turbine to operate in low-pressure operation mode.

In some embodiments, valve members 171 and 181 are configured for cooperative movement, that is to say both valve members move together between the first position (Figure 2A) and the second position (Figure 2B). In some embodiments, valve members 171 and 181 are independently operable. For example, in such embodiments valve member 171 may be in contact with first valve seat 172 (first position, Figure 2A), while second movable valve member 181 is in contact with fourth valve seat 183 (second position, Figure 2B).

In some embodiments valve members 171 and 181 are configured for positioning in at least one intermediate position, between the first positions and the second positions, allowing fluid from a given inlet port to flow to two outlet ports. Specifically, a portion of the fluid entering valve 100 from ambient inlet port 151 is directed to compressor-inlet outlet port 161, and another portion is directed to heat-exchanger cold-stream inlet outlet port 162. Similarly, a portion of the fluid entering through compressor-outlet inlet port 152 is directed to heat- exchanger cold- stream inlet outlet port 162 and another portion is directed to exhaust outlet port 163. The utility of some such intermediate positions is described hereinbelow.

Gas-turbine with 5-port valve 100

Figures 3 schematically depict an exemplary embodiment of a gas-turbine 10, comprising a valve 100 (as described above) operable in a Brayton cycle (Figure 3A) and in an inverse Brayton cycle (Figure 3B). Gas-turbine 10 further includes compressor 20 and turbine 22, together mounted on a common rotatable shaft 24 constituting a spool, combustor 26 and heat-exchanger 52. Gas-turbine 10 also includes a 3-way valve 220 having an inlet 224 and two outlets, 221 and 222. Valve 220 may be positioned as depicted in Figure 3A to providing fluid communication between inlet 224 and outlet 221, or as depicted in Figure 3B providing fluid communication between inlet 224 and outlet 222.

Valve 100 is configured to switch gas-turbine 10 between a high-pressure operation mode (Brayton cycle) depicted in Fig 3 A, and a low-pressure operation mode (inverse Brayton cycle) depicted in Fig 3B.

In Fig 3A (configuration " 1") both valve members 171 and 181 of valve 100 are in a first position (as in Figure 2A) directing fluid entering through ambient inlet port 151 to compressor-inlet outlet port 161, and fluid entering through compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port 162. Ambient air is drawn through ambient inlet port 151 past compressor-inlet outlet port 161 into compressor 20, pass through compressor-outlet inlet port 152 and heat-exchanger cold- stream inlet outlet port 162 of valve 100 into cold-stream conduit 54 of heat-exchanger 52, to combust in combustor 26. The combusted gases expand through turbine 22, and exit turbine 22 into hot- stream conduit 56 of heat-exchanger 52. 3-way valve 220 is set so that the combusted gases exit gas-turbine 10 through exhaust outlet 30 after exiting heat-exchanger 52.

In Fig 3B (configuration "2") both valve members 171 and 181 of valve 100 are in a second position (as in Figure 2B) directing fluid incoming through ambient inlet port 151 to heat-exchanger cold-stream inlet outlet port 162, and fluid coming through compressor-outlet inlet port 152 to exhaust outlet port 163. Ambient air is drawn through ambient inlet port 151 past heat-exchanger cold-stream inlet outlet port 162 into cold-stream conduit 54 of heat- exchanger 52 and combusts in combustor 26. The combusted gases exit turbine 22 into hot- stream conduit 56 of heat-exchanger 52. 3-way valve 220 is set to directing the combusted gases into compressor 20. The combusted gases exit compressor 20 and pass through compressor-outlet inlet port 152 to exit gas-turbine 10 through exhaust outlet port 163 of valve 100.

It is important to note that generally the flow directions through the various conduits including fluid conduits 120 of valve 100 are the same in both high-pressure operation mode and low-pressure operation mode, and do not change when switching gas-turbine 10 from one mode to the other. In Figure 4, the relation of thermal efficiency as a function of power output for gas- turbine 10 configured with valve 100 as described above is illustrated. Curve 410 is the thermal efficiency of gas-turbine 10 operating in the low-pressure operation mode (Figure 3B) and curve 412 is the thermal efficiency of gas-turbine 10 operating in the high-pressure operation mode (Figure 3A). Further embodiments of gas -turbine with 5-port valve 100

In some embodiments, a gas-turbine comprises an embodiment of a valve similar to valve 100 of Figures 2A and 2B, where the valve is integrated in the gas-turbine in "reverse". In such an embodiment, valve 100 includes three inlet ports and two outlet ports: an ambient 5 inlet port 151, a compressor-outlet inlet port 152, a heat-exchanger hot-stream outlet inlet port 153, a heat-exchanger cold-stream inlet outlet port 162 and an exhaust outlet port 163. Figures 5 depict an exemplary embodiment of a gas-turbine 11, comprising a valve 100, and operable according to a Brayton cycle (Figure 5A) and an inverse Brayton cycle (Figure 5B). Gas-turbine 11 further includes compressor 20 and turbine 22, together mounted on common

10 rotatable shaft 24, combustor 26 and heat-exchanger 52. Gas-turbine 11 also includes a 3-way valve 225 having two inlets, 226 and 227, and an outlet 228. Valve 225 may be positioned as depicted in Figure 5A providing fluid communication between inlet 226 and outlet 228, or as depicted in Figure 5B providing fluid communication between inlet 227 and outlet 228.

Valve 100 is configured to switch gas-turbine 11 between a high-pressure operation

15 mode in configuration " 1" depicted in Figure 5 A, and a low-pressure operation mode in configuration "2" depicted in Figure 5B.

In configuration " 1 " (Figure 5A) both valve members 171 and 181 of valve 100 are in a first position directing fluid from compressor-outlet inlet port 152 to heat-exchanger cold- stream inlet outlet port 162 and from heat-exchanger hot- stream outlet inlet port 153 to

20 exhaust outlet port 163. Ambient air is drawn through inlet 28 of gas-turbine 11 and through inlet 226 and outlet 228 of valve 225 into compressor 20, pass through compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port 162 of valve 100 into cold- stream conduit 54 of heat-exchanger 52, and combusts in combustor 26. The combusted gases expand through turbine 22 and pass through hot- stream conduit 56 of heat-exchanger

25 52. From heat-exchanger 52 the combusted gases pass through heat-exchanger hot-stream outlet inlet port 153 of valve 100, and are discharged through exhaust outlet port 163 to the surroundings.

In configuration "2" (Figure 5B) both valve members 171 and 181 of valve 100 are in a respective second position. Ambient air is drawn through ambient inlet port 151 and heat-

30 exchanger cold-stream inlet outlet port 162 of valve 100 into cold-stream conduit 54 of heat- exchanger 52, and combusts in combustor 26. The combusted gases expand through turbine 22, exiting into hot-stream conduit 56 of heat-exchanger 52. The combusted gases from heat- exchanger 52 pass through 3-way valve 225 to compressor 20, pass through compressor- outlet inlet port 152 and through exhaust outlet port 163 to exit gas-turbine 11. Embodiment of ^'6-port valve suitable for use with gas-turbine

In some embodiments described above, exhaust exits gas-turbine 10 through two different outlets. In some embodiments described below the exhaust exits a gas-turbine through a single exhaust outlet. Figures 6A and 6B depict a valve 102, suitable for use with a gas-turbine, in side cross-section. Valve 102 comprises a valve body 110 defining a single void in the form of a plurality of fluid conduits 120. Valve 102 further includes an ambient inlet port 151, a compressor-outlet inlet port 152, a heat-exchanger hot-stream outlet inlet port 153, a compressor-inlet outlet port 161, a heat-exchanger cold-stream inlet outlet port 162 and an exhaust outlet port 163, the six ports being in fluid communication one with the other through fluid conduits 120.

Valve 102 further includes a first valve member 171 and a second valve member 181. First valve member 171 is movable inside valve body 110 having at least two positions: a first position, depicted in Figure 6A, in contact with a first valve seat 172 in valve body 110 blocking fluid communication between ambient inlet port 151 and heat-exchanger cold- stream inlet outlet port 162; and a second position, depicted in Figure 6B, in contact with a second valve seat 173 in valve body 110 blocking fluid communication between ambient inlet port 151 and compressor- inlet outlet port 161. Second movable valve member 181 is movable inside valve body 110 having at least two positions: a first position, depicted in Figure 6 A, in contact with a third valve seat 182 in valve body 110 blocking fluid communication between compressor-outlet inlet port 152 and exhaust outlet port 163; and a second position, depicted in Figure 6B, in contact with a fourth valve seat 183 in valve body 110 blocking fluid communication between compressor-outlet inlet port 152 and heat- exchanger cold-stream inlet outlet port 162. Valve 102 also includes a check valve 130 operable as a unidirectional valve and configured in valve body 110 to allow fluid flowing from heat-exchanger hot- stream outlet inlet port 153 to any of the outlet ports 161, 162 or 163 of valve 102, and to block fluid flowing from any of the outlet ports of valve 102 out through heat-exchanger hot-stream outlet inlet port 153. As discussed with reference to valve 100, in some embodiments, valve members 171 and 181 of valve 102 are configured for cooperative movement, that is to say both valve members move together between the first position (Figure 6A) and the second position (Figure 6B). In some embodiments, valve members 171 and 181 are independently operable. For example, in such embodiments valve member 171 is in contact with first valve seat 172 (first position, Figure 6A), while second movable valve member 181 is in contact with fourth valve seat 183 (second position, Figure 6B).

As discussed with reference to valve 100, in some embodiments valve members 171 and 181 of valve 102 are configured for positioning in at least one intermediate position, between the first positions and the second positions, thereby allowing fluid from a given inlet port to flow to two outlet ports. The utility of some such intermediate positions is described hereinbelow.

Gas-turbine comprising 6-port valve 102 Figures 7 depict an exemplary embodiment of a gas-turbine 12 comprising an embodiment of valve 102, and operable in a Brayton cycle (Figure 7A) and in an inverse Brayton cycle (Figure 7B). Gas-turbine 12 also includes 3-way valve 220. An outlet 221 of valve 220 is connected to heat-exchanger hot-stream outlet inlet port 153 of valve 102 so that exhaust gas is discharged through exhaust outlet port 163 of valve 102. Valve 102 is configured to switch gas-turbine 12 between a high-pressure operation mode depicted in Figure 7 A, and a low-pressure operation mode depicted in Figure 7B

In Figure 7A both valve members 171 and 181 of valve 102 are in a respective first position. Ambient air is drawn through ambient inlet port 151 and compressor-inlet outlet port 161 of valve 102 into compressor 20, pass through compressor-outlet inlet port 152 and heat-exchanger cold- stream inlet outlet port 162 of valve 102 into cold- stream conduit 54 of heat-exchanger 52 to combust in combustor 26. The combusted gases expand through turbine 22, and exit turbine 22 into hot-stream conduit 56 of heat-exchanger 52. The combusted gases are directed by 3-way valve 220 to heat-exchanger hot- stream outlet inlet port 153 of valve 102. In valve 102, the combusted gases pass through check valve 130 and are then discharged to the surroundings through exhaust outlet port 163.

In Figure 7B both valve members 171 and 181 of valve 102 are in a respective second position. Ambient air is drawn through ambient inlet port 151 and through heat-exchanger cold-stream inlet outlet port 162 of valve 102 into cold-stream conduit 54 of heat-exchanger 52 to combust in combustor 26. The combusted gases expand through turbine 22 into hot- stream conduit 56 of heat-exchanger 52. 3-way valve 220 directs the gases into compressor 20, to exit compressor 20, and pass through compressor-outlet inlet port 152 of valve 102 and exit gas-turbine 12 through exhaust outlet port 163 of valve 102. Check valve 130 blocks the exhaust gases from flowing back through heat-exchanger hot-stream outlet inlet port 153 of valve 102 towards 3-way valve 220. Additional embodiment of ^'6-port valve suitable for use with gas-turbine

Figures 8A and 8B depict a valve 103, suitable for use with a gas-turbine, in side cross-section. Valve 103 comprises a valve body 110 defining a single void in the form of a plurality of fluid conduits 120. Valve 103 further includes an ambient inlet port 151, a compressor-outlet inlet port 152, a heat-exchanger hot-stream outlet inlet port 153, a compressor-inlet outlet port 161, a heat-exchanger cold-stream inlet outlet port 162 and an exhaust outlet port 163, the six ports being in fluid communication one with the other through fluid conduits 120. Valve 103 further comprises a bypass conduit providing fluid communication between heat-exchanger hot- stream outlet inlet port and compressor-inlet outlet port.

Valve 103 further includes three valve members, 171, 181 and 191. First valve member 171 is movable inside valve body 110 having at least two positions: a first position as depicted in Figure 8 A in contact with a first valve seat 172 in valve body 110, and a second position, depicted in Figure 8B, in contact with a second valve seat 173 in valve body 110. In the first position first valve member 171 in said first position blocks fluid communication between ambient inlet port 151 and heat-exchanger cold-stream inlet outlet port 162 and in the second position (Figure 8B) blocks fluid communication between ambient inlet port 151 and compressor inlet outlet port 161.

Second valve member 181 is movable inside valve body 110 having at least two positions: a first position, depicted in Figure 8 A, in contact with a third valve seat 182 in valve body 110, and a second position, depicted in Figure 8B, in contact with a fourth valve seat 183 in valve body 110. In the first position (Figure 8A), second valve member 181 blocks fluid communication between heat-exchanger hot-stream outlet inlet port 153, and heat-exchanger cold-stream inlet outlet port 162 and in the second position (Figure 8B) blocks fluid communication between compressor-outlet inlet port 152 and heat-exchanger cold-stream inlet outlet port 162.

Third valve member 191 is movable inside valve body 110 having at least two positions: a first position, depicted in Figure 8 A, in contact with a fifth valve seat 192 in valve body 110, and a second position, depicted in Figure 8B, in contact with a sixth valve seat 193 in valve body 110. In the first position (Figure 8A) third valve member 191 blocks fluid communication between heat-exchanger hot- stream outlet inlet port 153 and compressor inlet outlet port 161 through the bypass conduit and in the second position (Figure 8B) third valve member 191 blocks fluid communication between heat-exchanger hot-stream outlet inlet port 153 and exhaust outlet port 163. Analogously to the discussed above with reference to valves 100 and 102, in some embodiments, two or three valve members 171, 181 and 191 are configured for cooperative movement. Analogously to the discussed above with reference to valves 100 and 102, in some embodiments, one or more valve members 171, 181 and 191 are independently operable.

Gas-turbine comprising 6-port valve 103

Figures 9 depict an exemplary embodiment of a gas-turbine 13 comprising an embodiment of a valve 103, operable according to a Brayton cycle (Figure 9A) and according to an inverse Brayton cycle (Figure 9B)

Valve 103 is configured to switch gas-turbine 13 between a high-pressure operation mode depicted in Figure 9 A, and a low-pressure operation mode depicted in Figure 9B.

In Figure 9A, valve members 171, 181 and 191 of valve 103 are in a respective first position. Ambient air is drawn through ambient inlet port 151 and compressor-inlet outlet port 161 of valve 103 into compressor 20, and pass through compressor-outlet inlet port 152 and heat-exchanger cold- stream inlet outlet port 162 of valve 103 into cold- stream conduit 54 of heat-exchanger 52 to combust in combustor 26. The combusted gases expand through turbine 22 and exit through hot-stream conduit 56 of heat-exchanger 52 and through heat- exchanger hot-stream outlet inlet port 153, to be discharged through exhaust outlet port 163 to the surroundings.

In Fig 9B all three valve members 171, 181 and 191 of valve 103 are in a respective second position. Ambient air is drawn through ambient inlet port 151 and heat-exchanger cold-stream inlet outlet port 162 of valve 103 into cold-stream conduit 54 of heat-exchanger 52 to combust in combustor 26. The combusted gases enter turbine 22 and exit turbine 22 into hot-stream conduit 56 of heat-exchanger 52. Exiting hot-stream conduit 56, the combusted gases are drawn through heat-exchanger hot-stream outlet inlet port 153, through the bypass conduit to compressor-inlet outlet port 161 of valve 103 into compressor 20. From compressor 20, the combusted gases pass through compressor-outlet inlet port 152 of valve 103 to be discharged from gas-turbine 13 through exhaust outlet port 163 of valve 103. In general terms, in some embodiments a gas-turbine such as 13 is switched between a high-pressure operation mode and a low-pressure operation mode as is described above, using a six -port valve, having three inlet ports designated "X" (ambient inlet port 151), "Y" (compressor-outlet inlet port 152) and "Z" (heat-exchanger hot-stream outlet inlet port 153), and three outlet ports designated "x" (compressor- inlet outlet port 161), "y" (heat-exchanger cold-stream inlet outlet port 162) and "z" (exhaust outlet port 163). In a first configuration, the valve provides fluid communication exclusively between inlet port "X" and outlet port "x", between inlet port "Y" and outlet port "y" and between inlet port "Z" and outlet port "z". In a second configuration, the valve provides fluid communication exclusively between inlet port "X" and outlet port "y", between inlet port "Y" and outlet port "z" and between inlet port "Z" and outlet port "x". Providing flow communication exclusively between the specified pairs of inlet and outlet ports means that only fluid communication which is explicitly described between the specified ports is provided, and there is no fluid communication between the ports which is not explicitly described.

Multi-power single-spool gas-turbine

Aspects of the invention relate to multiport valves suitable for use with gas-turbines that allow switching between high-pressure, low-pressure and at least one intermediate- pressure operation modes of a gas-turbine. According to such embodiments, a valve is configured and operable to be in at least one intermediate configuration, in addition to the high-pressure (Brayton cycle) configuration " 1 " and low-pressure (inverse Brayton cycle) configuration "2" discussed above, for example in Figures 8A and 8B. Such an intermediate configuration allows a gas-turbine to work in a pressure mode intermediate between the high and low-pressure operation modes. Figure 10 depicts an embodiment of a valve 103 in an exemplary intermediate configuration, valve members 171, 181 and 191 being in an intermediate position, between the respective first position and second position. In such an intermediate configuration, fluid from a given inlet port is directed to flow to two outlet ports. Specifically, a portion of the fluid entering valve 103 from ambient inlet port 151 is directed to compressor-inlet outlet port 161, and another portion to heat-exchanger cold-stream inlet outlet port 162. Similarly, a portion of the fluid entering through compressor-outlet inlet port 152 is directed to heat- exchanger cold- stream inlet outlet port 162 and another portion is directed to exhaust outlet port 163. A portion of the fluid entering valve 103 from heat-exchanger hot-stream outlet inlet port 153 is directed to exhaust outlet port 163 and another portion is directed to compressor-inlet outlet port 161.

In some embodiments, a mixing region 126 within fluid conduits 120 is configured to function as jet pump ejector. In some embodiments, such configuration includes fashioning at least one of valve members 171, 181 as an airfoil having a pre-defined aerodynamic profile. When mixing region 126 is configured as a jet pump ejector, the pressure of fluid flowing from compressor-outlet inlet port 152 to heat-exchanger cold- stream inlet outlet port 162 drops, producing a suction zone (for example, through the Bernoulli effect). The suction zone sucks fluid from ambient inlet port 151 into valve 103 and to heat-exchanger cold-stream inlet outlet port 162.

5 Figure 11 depicts an exemplary embodiment of a gas-turbine 13, configured with a valve 103 and operable in an intermediate pressure operation mode in addition to a high- pressure operation mode (configuration "1", Figure 8A) and a low-pressure operation mode (configuration "2", Figure 8B). During operation in the intermediate pressure operation mode when valve members 171, 181 and 191 are positioned as depicted in Figure 10, compressor

10 20 generates a low-pressure region around compressor-inlet outlet port 161 of valve 103, so a portion of ambient air is drawn from ambient inlet port 151 into compressor-inlet outlet port 161. Additionally, a portion of the gas coming from heat-exchanger 52 into heat-exchanger hot-stream outlet inlet port 153 is drawn into compressor 20 through compressor-inlet outlet port 161.

15 Compressed fluid coming from compressor 20 flows into compressor-outlet inlet port

152 at high-pressure and is directed to both heat-exchanger cold-stream inlet outlet port 162 and to exhaust outlet port 163, the exact ratio dependent, inter alia, on the position of valve member 181.

Thus, in some embodiments when one or more of valve members 171, 181 and 191

20 are positioned in an intermediate position, for example as depicted in Figure 11, a gas-turbine 13 is operable in a mode where the pressure is between the highest and lowest pressures and consequently the power output is between the highest and lowest power outputs. In such embodiments, in all three modes the thermal efficiency of the gas-turbine is relatively high (see curve 414 in Figure 4).

25 In some embodiments an intermediate pressure operation mode of a gas-turbine such as 13 is obtained by positioning only one valve member 171, 181 or 191 in a respective intermediate position while the other two valve members are positioned in either a first or second position. In some embodiments, an intermediate pressure operation mode of gas- turbine 13 is obtained by positioning two valve members in a respective intermediate

30 position, while the remaining valve member is positioned in either a first or a second position.

In some embodiments, a gas-turbine such as gas-turbine 13 comprising a valve with three valve members as described herein such as valve 103, is switched to an intermediate pressure operation mode by positioning a first valve member 171 and a second valve member 181 in an intermediate position, substantially as is described above, and positioning a third valve member 191 in a first position or in a second position.

Analogously, in some embodiments, a gas-turbine such as gas-turbine 10 of Figures 3 or gas-turbine 11 of Figures 5, comprising a valve with two valve members as described herein, such as valve 100, is switched to an intermediate pressure operation mode by positioning a first valve member 171 and a second valve member 181 of the valve in an intermediate position. Similarly, in some embodiments a gas-turbine such as gas-turbine 12 of Figures 7 is switched to an intermediate pressure operation mode by positioning a first valve member 171 and a second valve member 181 of a valve such as valve 102 in an intermediate position. In some such embodiments, a mixing region analogue to mixing region 126 of valve 103 is formed in the respective two-valve member valve (e.g., 100 or 102) to function as jet pump ejector. In some embodiments of gas-turbines such as 10, 11 and 12, a continuity of intermediate pressure operation modes is obtained by positioning valve members 171 and 181 of respective valves such as 100 and 102 in a continuity of positions. In some embodiments, the position of at least one valve member is not continuously variable. That is to say, one or a series of intermediate pressure operation modes of gas- turbine 13 is obtained by maintaining at least one valve member in a fixed position while varying the position of the remaining valve members. In some embodiments, valve members 171, 181 and 191 are moveable between two endpoints, and may be maintained at a specific intermediate position between the endpoints. In such embodiments, valve 103 has at least three configurations, and gas-turbine 13 comprising valve 103 may be efficiently operated in at least three different pressure operation modes.

Returning to Figure 4, the relation of thermal efficiency as a function of power output for gas-turbine 13 including valve 103 as described above is schematically depicted, where curve 410 corresponds to a single spool gas-turbine operating in the low-pressure operation mode (as is described in Figure 9B), curve 412 corresponds to gas-turbine 13 operating in a high-pressure operation mode (as is described in Figure 9A), and curve 414 corresponds to gas-turbine 13 operating in one exemplary intermediate pressure operation mode as described above in Figure 11, where mixing region 126 is configured as a jet pump ejector.

Valves for substantially continuous efficient power output

In some embodiments, a valving system is provided that allows high-pressure operation mode and/or low-pressure operation mode of a gas-turbine (including, inter alia, a combustor and a heat-exchanger) at a continuously varying power output at relative high efficiency. Such a valving system operates by reducing the mass flow of fluid to the combustor through the heat-exchanger. Such mass flow reduction is similar to the achieved by inlet throttling, for example with the use of variable inlet guide vanes.

In the art, variable inlet guide vanes are often used with large gas-turbines. Such guide

5 vanes are unsuitable for use with small turbines due to high expense and technical complexity at small sized. Further, as there is a need for matching between the whirl caused by the guide vanes and the compressor blades, the guide vanes can be varied only by about 15% which allows a change of about 20% in power output at reasonable efficiencies.

Figures 13 show an embodiment of a valve 104, suitable for use with a gas-turbine,

10 schematically depicted in side cross-section. In valve 104, valve member 181 is configured to have a continuity of positions when in the first position in contact with valve seat 182, allowing a gas-turbine including valve 104 and operating in a high-pressure operation mode to operate in a continuity of output power levels. Specifically, valve member 181 is relatively thick and valve seat 182 appropriately configured so that valve member 181 has a range of

15 motion defining a continuity of positions in continuous contact with valve seat 182 thereby blocking fluid communication through valve seat 182. Through the continuity of positions in the first position, the varying bulk of valve member 181 located in the fluid path between compressor-outlet inlet port 152 and heat-exchanger cold-stream inlet outlet port 162, allows the size of the fluid path to be controllably varied.

20 Figures 13A and 13B show two exemplary such positions where valve member 181 is in the first position 1 in contact with valve seat 182, but the exact position of valve member 181 varies the size of a fluid path 127 inside valve 104, between compressor-outlet inlet port 152 and heat-exchanger cold-stream inlet outlet port 162, thereby varying the gas-turbine output power level. For example, when valve member 181 is in position as depicted in Figure

25 13 A, fluid path 127 is wide, allowing for a high flow rate of fluid from compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port 162 so that the gas-turbine generates a relatively high output power level; and when valve member 181 is in a position as depicted in Figure 13B, fluid path 127 is narrow, allowing for a low flow-rate of fluid, so that the gas-turbine generates a relatively low output power level.

30 It is understood that valve 104 allows a gas-turbine to operate in a high-pressure operation mode in a continuity of configurations as described above, since valve member 181 is continuously in contact with valve seat 182, in the described continuity of positions, substantially blocking flow of fluid from compressor-outlet inlet port 152 to exhaust outlet port 163. Further, when valve 104 is in a high-pressure mode configuration as described above, valve member 171 is maintained in contact with valve seat 172, substantially blocking flow from ambient inlet port 151 to heat-exchanger cold-stream inlet outlet port 162.

Analogously to valve 100 as depicted in Figure 2B, valve 104 further allows an associated gas-turbine to operate in a low-pressure operation mode when valve members 171 and 181 are in a second position (not shown). Specifically, valve 104 is in a low-pressure mode configuration when valve members 171 and 181 are in contact with valve seats 173 and 183, respectively. Thus, analogously to valve 100 in gas-turbine 10 of Figures 3, valve 104 is operable to switch a gas-turbine between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output power level in the high-pressure operation mode. Similarly, in a gas-turbine such as gas-turbine 11 depicted in Figures 5, multiport valve 104 is operable to switch the gas-turbine between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output power level in the high-pressure operation mode. Figures 14A and 14B depict an embodiment of a valve 105, suitable for use with a gas-turbine, schematically depicted in side cross-section. In valve 105, valve member 171 is configured to have a continuity of positions when in the second position in contact with valve seat 173, allowing a gas-turbine including valve 105 and operating in a low-pressure operation mode, to operate in a continuity of output power levels. Analogously to the described with reference to Figures 13, in Figures 14 valve member 171 is relatively thick and valve seat 173 is appropriately configured so that valve member 171 has a range of motion defining a continuity of positions in continuous contact with valve seat 173 thereby blocking fluid communication through valve seat 173. Through the continuity of positions in the second position, the varying bulk of valve member 171 located in the fluid path between ambient inlet port 151 and heat-exchanger cold-stream inlet outlet port 162, allows the size of the fluid path to be controllably varied.

Figures 14A and 14B depict two exemplary such positions where valve member 171 is in the second position in contact with valve seat 173, but the exact position of valve member 171 effects the gas-turbine output power level by varying the size of path 128 inside valve 105, between ambient inlet port 151 and heat-exchanger cold-stream inlet outlet port 162. For example, when valve member 171 is in position as depicted in Figure 14A, fluid path 128 is wide, allowing for a high flow rate of air from ambient inlet port 151 to heat- exchanger cold-stream inlet outlet port 162, thereby generating a high output power level; and when valve member 171 is in position as depicted in Figure 14B, fluid path 128 is narrow allowing for a low flow rate of fluid so that the gas-turbine generates a low output power level.

It is understood that valve 105 allows a gas-turbine to operate in a low-pressure operation mode in a continuity of configurations as described above, since valve member 171 5 is continuously in contact with valve seat 173 in the described continuity of positions, substantially blocking flow of fluid from ambient inlet port 151 to compressor-inlet outlet port 161. Further, when valve 105 is in such a low-pressure mode configuration as described above, valve member 181 is maintained in contact with valve seat 183, substantially blocking flow from compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port

10 162.

Analogously to valve 100 as depicted in figure 2A, valve 105 further allows an associated gas-turbine to operate in a high-pressure operation mode when valve members 171 and 181 are in a first position (not shown). Specifically, valve 105 is in a high-pressure mode configuration when valve members 171 and 181 are in contact with valve seats 172 and 182,

15 respectively. Thus, analogously to valve 100 in gas-turbine 10 of Figures 3, valve 105 is operable to switch a gas-turbine between a high-pressure operation mode according to a

Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output power level in the low-pressure operation mode.

In some embodiments, a valve includes two separate valve members that allow both

20 switching of an associated gas-turbine between a high-pressure and a low-pressure operation mode, and varying continuously the size of the path to the heat-exchanger. Referring to Figures 15A, 15B, and 15C, valves 106, 107 and 108, respectively, are schematically depicted. Valves 106, 107 and 108 are suitable for use with a gas-turbine and configured for switching a gas-turbine comprising valves 106, 107 or 108 between a high-pressure and a

25 low-pressure operation modes. Valves 106, 107 and 108 are also configured for continuously varying output power level of an associated gas-turbine by allowing a continuous varying of the size of the fluid path to the heat-exchanger.

In valve 106 depicted in Figure 15 A, a movable valve member 281 is rotatably moveable around valve member axis 184, sharing an axis of rotation with valve member 181.

30 While valve member 171 maintains contact with valve seat 172 and valve member 181 maintains contact with valve seat 182 (so that valve 106 is in a high-pressure mode configuration) valve member 281 is moveable through a continuity of positions allowing variation of the size of fluid path 127, thereby varying the output power level of the associated gas-turbine. Thus, analogously to valve 100 in gas-turbine 10 of Figures 3, valve 106 is operable to switch a gas-turbine between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output power level in the high-pressure operation mode.

5 A similar variation in the size of the fluid path is implementable in a multiport valve analogous to the depicted in Figures 5.

In valve 107 depicted in Figure 15B, a valve member 271 is movable around valve member axis 174 thereby operable to vary the size of fluid path 128 from ambient inlet port 151 to the heat-exchanger (not shown) through heat-exchanger cold-stream inlet outlet port

10 162, while valve members 171 and 181 maintain contact with valve seats 173 and 183 respectively, so that valve 107 is in a low-pressure configuration. Thus, analogously to valve 100 in gas-turbine 10 of Figures 3, valve 107 is operable to switch a gas-turbine between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output

15 power level in the low-pressure operation mode.

In valve 108 depicted in Fig 15C, two valve members, 171 and 271, both movable around first valve member axis 174, and two valve members 181 and 281, both movable around second valve member axis 184, allow the size of fluid paths 127 and 128, respectively, to be continuously varied while valve 108 is set in high-pressure configuration

20 and in low-pressure configuration. Analogously to valve 100 of Figures 3, valve 108 is operable to switch a gas-turbine between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, and in addition to varying the gas-turbine output power level in the low-pressure operation mode and in the high-pressure operation mode. A similar variation in the size of the fluid path is

25 implementable in a multiport valve analogous to the depicted in Figures 5.

Returning to Figure 4, the relationship of thermal efficiency to power output for a gas- turbine including a valve as described in Figures 13 A, 13B, 14A, 14B, 15A 15B and 15C is schematically depicted. Curve 412 corresponds to a gas-turbine operating in the high-pressure operation mode, for example with a valve 100 of Figures 2A, while curve 416 corresponds to

30 a gas-turbine operating in high-pressure operation mode with a valve of Figures 12A, 12B 14A or 14C. Curve 410 corresponds to a gas-turbine operating in the low-pressure operation mode, for example with a valve 100 of Figures 2B, while curve 418 corresponds to the gas- turbine operating in low-pressure operation mode with a valve of Figures 14A, 14B 15B or 15C. In the embodiments described above, the valve members are substantially plates configured to rotatably move between the different positions around a single axis close to or at an edge of the valve member. Generally, the teachings herein may be implemented using any suitable type of valve member. For example, in some embodiments valve members used include suitably-configured butterfly valves (especially tricentric butterfly valves), ball valves or rotary valves.

Gas-turbines using valves as described herein may be of any desired power capacity. That said, in some embodiments, a gas-turbine is configured for producing up to about 100 kW. In some embodiments, a gas-turbine is configured for producing from about 14 kW to about 40 kW of power. In some embodiments, a gas-turbine is configured for producing from about 7 kW to about 36 kW of power. Such low powers are useful, for example, for powering a small motor vehicle, such as a light truck or an automobile.

Reduced NOx emission inverse-Brayton cycle gas-turbine Aspects of the invention relate to gas-turbines operating in a low-pressure operation mode according to an inverse Brayton cycle that have reduced NOx emissions. Due to poor mixing and vaporization at low power operation which create local high temperature zones, gas-turbine NOx emissions are higher under partial load. In some embodiments of the invention, inlet air is mixed with a portion of exhaust and is directed into the combustor, thereby decreasing the oxygen content of the combustible mixture in the combustor, and as a result, reducing the amount of NOx emissions.

Thus, according to an aspect of some embodiments of the invention, there is provided a method of operating a gas-turbine according to an inverse Brayton cycle, comprising: a) providing a conduit allowing fluid communication between a compressor of the gas-turbine and a cold-stream inlet of a heat-exchanger of the gas-turbine; and b) during inverse Brayton cycle operation of the gas-turbine, directing fluid from the compressor to the heat-exchanger cold-stream inlet through the conduit so that a portion of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. In some embodiments, between about 30% and about 70% (in some embodiments, between about 40% and about 60%, in some embodiments between about 45% and about 55%) by mass of the fluid entering the heat-exchanger cold- stream inlet is from the compressor. In one specific preferred embodiment, approximately 50% by mass of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. In some embodiments, the method further comprises: adjusting a size of the conduit so as to control an amount of fluid entering the cold-stream inlet from the compressor.

According to an aspect of some embodiments of the invention there is also provided a gas-turbine comprising, when operating according to an inverse Brayton cycle, a) an air inlet configured to direct fluid into a cold-stream conduit of a heat-exchanger through a cold- stream inlet; b) conduits to direct fluid from the cold-stream conduit to a combustor, from the combustor to a turbine, from the turbine to a hot- stream conduit of the heat-exchanger, from the hot-stream conduit to a compressor, and from the compressor to an exhaust outlet; and c) a conduit allowing passage of fluid from the compressor into the cold-stream inlet of the heat-exchanger.

In some embodiments, the gas-turbine is configured to operate only according to an inverse Brayton cycle.

In some embodiments the gas-turbine is configured to optionally operate according to a Brayton cycle, for example as described herein. In some such embodiments, the gas-turbine is configured so that during operation according to a Brayton cycle, the conduit is substantially blocked preventing passage of fluid between the compressor and the cold- stream inlet.

In some embodiments, the conduit allowing passage of fluid from the compressor into the cold-stream inlet is of fixed size. In some embodiments, the size of the conduit allowing passage of fluid from the compressor into the cold-stream inlet is adjustable, for example allowing varying an amount of fluid passing from the compressor into the cold-stream inlet.

In some embodiments, the conduit allowing passage of fluid from the compressor into the cold- stream inlet is configured so that during operation according to an inverse Brayton cycle between about 30% and about 70% (in some embodiments, between about 40% and about 60%, in some embodiments 45% and about 55%) by mass of the fluid entering the heat-exchanger cold-stream inlet is from the compressor.

In some embodiments, the conduit allowing passage of fluid from the compressor into the cold- stream inlet of the heat-exchanger is passive, that is to say, occurs due to the pressure differential between the two regions without investment of any additional work. In some embodiments, the conduit is active, that is to say, comprises a component such as a pump that performs work to direct fluid from the compressor to the cold-stream inlet of the heat-exchanger. Figure 16 depicts an exemplary embodiment of a gas-turbine 19 including a valve 109 suitable for use with a gas-turbine and useful for reducing the amount of NOx emissions of the gas-turbine in low-pressure operation mode. In the embodiment depicted in Figure 16, valve 109 comprises five ports and two valve members in a configuration similar to valve 5 100 depicted in Figures 2. In the embodiment depicted in Figure 16, valve 109 further comprises a permeable section 140 of valve body 110 between regions 121 and 122 of fluid conduits 120, allowing passage of fluid from region 121 to region 122.

In the embodiment depicted in Figure 16, region 121 is up-stream from valve member 181, between valve member 181 and exhaust outlet port 163 while region 122 is up-stream

10 from valve member 181, between valve member 181 and heat-exchanger cold-stream inlet outlet port 162. Permeable section 140 is unidirectional, only allowing passage of fluid from region 121 to region 122 if the pressure in region 121 is higher than the pressure in region 122 (e.g., during inverse Brayton cycle operation of gas-turbine 19), but blocking passage of fluid from region 122 into region 121 (e.g., during Brayton cycle operation of gas-turbine

15 19).

Depending on the positions of valve members 171 and 181, gas-turbine 19 may be set in configurations analagous to the configurations depicted in for gas-turbine 10 in Figures 3A and 3B. In Figure 16, gas-turbine 19 is depicted in a configuration analogous to configuration "2" (Figure 2B), consequently operating in a low-pressure operation mode according to an

20 inverse Brayton cycle. As a result, the pressure in region 121 is higher than the pressure in region 122 so a portion of the exhaust gas passes from region 121 through permeable section 140 into region 122. The portion of exhaust gas that passes through permeable section 140 to region 122 mixes with the ambient air coming into gas-turbine 19, reducing oxygen content in the fluid entering the combustor and consequently reducing NO'x content in the combusted

25 gas of turbine 19.

Some such embodiments are superficially similar to reversed circulation methods implemented in internal combustion engines, where a significant amount of power is invested in recompressing exhaust into a high-pressure combustion chamber, reducing thermal efficiency but reducing NOx emissions. In contrast, in some embodiments of the invention

30 advantage is taken of the fact that in a gas-turbine operating according to an inverse Brayton cycle the pressure in heat-exchanger cold-stream inlet is lower than at the compressor outlet, so that little if any power is used to bring the exhaust into the heat-exchanger cold-stream inlet. Additionally, in some embodiments, the thermal efficiency of the gas-turbine is increased by the mixing incoming ambient air with the hot exhaust. Figure 17A depicts an exemplary embodiment of permeable section 140 in valve 109, including a check valve 141, operable as a unidirectional valve (e.g., a reed valve) and configured to allow fluid passage from region 121 to region 122 of fluid conduits 120 of valve 109, and to block passage of fluid in the opposite direction from region 122 to region

5 121.

Figure 17B depicts another exemplary embodiment of permeable section 140 of valve 109 integrated in valve member 181.

Valve member 181 includes a unidirectional valve 186 (e.g., a reed valve) allowing fluid passage from region 121 to region 122 and to block fluid passage from region 121 to

10 122. Specifically, valve member 181 comprises conduit 185 providing fluid communication from a face 188 to a face 189 of valve member 181. Unidirectional valve 186 is disposed inside conduit 185. When the pressure in region 122 is greater than the pressure in region

121, valve 186 is closed, sealing conduit 185. When the pressure in region 121 is greater than the pressure in region 122, valve 186 opens allowing fluid (e.g., exhaust gas from

15 compressor-outlet inlet port 152) to pass from region 121 to region 122.

Generally, the size of holes 185 determines the amount of exhaust gas mixed and therefore the oxygen content of the gas entering a combustor 26. In some embodiments, the amount of exhaust gas mixed can be controlled, for example, by changing the number or size of holes. It is understood that embodiments of permeable section 140 are not limited to the 20 examples described above and permeable section 140 can comprise holes, slits, pores and the like, allowing passage of fluid from region 121 to region 122 of fluid conduits 120 valve 109.

The reduction of NOx emissions in a gas-turbine operating in low-pressure (inverse

Brayton mode) is described with reference to embodiments depicted in Figures 16, 17A and

17B where the conduit directing exhaust from the compressor outlet to mix with air entering

25 the combustor of a gas-turbine is part of or associated with a valve as described herein that allows operation of a gas-turbine in both high and low-pressure modes.

In some embodiments any of the valves of the invention described herein, e.g. valve 100, can be utilized to reduce NOx emission by permitting a portion of the oxygen-depleted exhaust gas to mix with incoming ambient air in low-pressure operation mode of a gas- 30 turbine, by positioning valve member 181 close to, but not in contact with, valve seat 183, when operating the gas-turbine in low-pressure operation mode. Thus, when valve member 181 allows for fluid passage between compressor-outlet inlet port 152 and heat-exchanger cold-stream inlet outlet port 162 in low-pressure operation mode, exhaust gas is forced into the flow of incoming ambient air, where the amount of such exhaust passage is controlled by the exact positioning of valve member 181 with respect to valve seat 183.

In some embodiments, a gas-turbine configured for multipressure operation, e.g., such as described in US patents 6,526,757 and 6,606,864, includes an additional valve (or an existing valve is modified) that allows passage of exhaust from the compressor outlet to mix with air entering the combustor during low-pressure (inverse Brayton) operation, thereby reducing NOx emissions.

In some embodiments, a gas-turbine configured for multipressure operation, e.g., such as described hereinabove, includes an additional valve (not associated with the valve that allows switching between high and low-pressure operation) defining a conduit that allows passage of exhaust from the compressor outlet to mix with air entering the combustor during low-pressure (inverse Brayton) operation, thereby reducing NOx emissions. In some embodiments, such an extra valve has two configurations: closed (blocking passage of exhaust) and open (allowing passage of exhaust) defining a fixed conduit size. In some embodiments, the valve is adjustable, allowing the size of the conduit to be adjusted to allow varying the amount of exhaust passing to mix with the air entering the combustor.

In some embodiments, a gas-turbine configured for low-pressure (inverse Brayton cycle) operation, e.g. such as known in the art, includes a valve defining a conduit that allows passage of exhaust from the compressor outlet to mix with air entering the combustor, thereby reducing NOx emissions. In some embodiments, such a valve has two configurations: closed (blocking passage of exhaust) and open (allowing passage of exhaust). In some embodiments, the valve is adjustable, allowing variation of the amount of exhaust passing to mix with the air entering the combustor.

In the above, oxygen-depleted exhaust is mixed with ambient air prior to entering the heat-exchanger of the gas-turbine. In some embodiments, the exhaust is mixed with the air after exiting the heat-exchanger cold-stream outlet and prior to entering the combustor. However, such embodiments are usually considered less advantageous as lowering combustor inlet temperature reduces thermal efficiency of the gas-turbine.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.

Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.

Claims

CLAIMS:

1. A gas-turbine configured for operation according to both Brayton-cycle and inverse- Brayton cycle, comprising: a) a multiport valve including movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port (152), an ambient inlet port (151), a heat-exchanger cold-stream inlet outlet port (162), an exhaust outlet port (163), and a fifth port; b) a compressor outlet (42) of a compressor (20) in fluid communication with said compressor-outlet inlet port (152); and c) a heat-exchanger cold-stream inlet (58) of a heat-exchanger (52) in fluid communication with said heat-exchanger cold- stream inlet outlet port (162); wherein during Brayton-cycle operation of the gas-turbine: a said valve member blocks fluid communication between said compressor-outlet inlet port (152) and said exhaust outlet port (163), and a said valve member blocks fluid communication between said ambient inlet port (151) and said heat-exchanger cold- stream inlet outlet port (162); and during inverse Brayton-cycle operation of the gas-turbine: a said valve member blocks fluid communication between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162).

2. The gas-turbine of claim 1, wherein said fifth port is a compressor- inlet outlet port (161) in fluid communication with an inlet (40) of said compressor (20), wherein during inverse Brayton-cycle operation of the gas-turbine, a said valve member blocks fluid communication between said ambient inlet port (151) and said compressor-inlet outlet port (161).

3. The gas-turbine of claim 2, further comprising an additional valve (220) functionally associated with a hot-stream outlet (64) of said heat-exchanger (52), wherein during inverse Brayton-cycle operation of the gas-turbine, said additional valve (220) allows fluid communication from said hot-stream outlet (64) of said heat-exchanger (52) to an inlet (40) of said compressor (20).

4. The gas-turbine of claim 3, wherein during Brayton-cycle operation of the gas- turbine, said additional valve (220) allows fluid communication from said hot-stream outlet (64) of said heat-exchanger (52) to an exhaust outlet (30) of the gas-turbine.

5. The gas-turbine of claim 1, wherein said fifth port is a heat-exchanger hot-stream outlet inlet port (153) in fluid communication with a hot-stream outlet (64) of said heat- exchanger (52), and wherein during inverse Brayton-cycle operation of the gas-turbine, a said valve member blocks fluid communication between said heat-exchanger hot- stream outlet inlet port (153) and said exhaust outlet port (163).

6. The gas-turbine of claim 5, further comprising an additional valve (225) functionally associated with a hot-stream outlet (64) of said heat-exchanger (52),wherein during inverse Brayton-cycle operation of the gas-turbine, said additional valve (225) allows fluid communication from said hot-stream outlet (64) of said heat-exchanger (52) to an inlet (40) of said compressor (20).

7. The gas-turbine of claim 6, wherein during Brayton-cycle operation of the gas- turbine, said additional valve (225) allows fluid communication from ambient to an inlet (40) of said compressor (20).

8. The gas-turbine of claim 1, wherein said fifth port is a compressor- inlet outlet port (161) in fluid communication with an inlet (40) of said compressor (20), and wherein during inverse Brayton-cycle operation of the gas-turbine a said valve member blocks fluid communication between said ambient inlet port (151) and said compressor-inlet outlet port (161); and said multiport valve further includes a sixth port, a heat-exchanger hot-stream outlet inlet port (153) in fluid communication with a hot-stream outlet (64) of said heat- exchanger (52).

9. The gas-turbine of claim 8, further comprising an additional valve (220) functionally associated with a hot-stream outlet (64) of said heat-exchanger (52), wherein during inverse Brayton-cycle operation of the gas-turbine, said additional valve (220) allows fluid communication from said hot-stream outlet (64) of said heat-exchanger (52) to an inlet (40) of said compressor (20).

10. The gas-turbine of claim 9, wherein during Brayton-cycle operation of the gas- turbine, said additional valve (220) allows fluid communication from said hot-stream outlet (64) of a heat-exchanger (52) to an exhaust outlet (30) of the gas-turbine through said heat- exchanger hot-stream outlet inlet port (153).

11. The gas-turbine of any of claims 8 to 10, further comprising a component functionally associated with said heat-exchanger hot-stream outlet inlet port (153), allowing flow of fluid from said hot-stream outlet (64) of said heat-exchanger (52) through said heat-exchanger hot- stream outlet inlet port (153) and blocking flow of fluid from said multiport valve to said hot- stream outlet (64) of said heat-exchanger (52) through said heat-exchanger hot-stream outlet inlet port (153).

12. The gas-turbine of claim 11, wherein said component is a undirectional valve (130) that is part of said multiport valve.

13. The gas-turbine of claim 8, said multiport valve further comprising a bypass conduit providing fluid communication between said heat-exchanger hot-stream outlet inlet port (153) and said compressor-inlet outlet port (161), and wherein during Brayton-cycle operation of the gas-turbine, a said valve member blocks said fluid communication between said heat- exchanger hot-stream outlet inlet port (153) and said compressor-inlet outlet port (161) through said bypass conduit.

14. A multiport valve suitable for use with a gas-turbine allowing switching of a mode of gas-turbine operation between a Brayton cycle and an inverse Brayton cycle, comprising: a) a valve body (110) defining a void in the form of a plurality of fluid conduits (120); b) at least five ports leading to said void of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port (152), an ambient inlet port (151), a heat- exchanger cold-stream inlet outlet port (162), an exhaust outlet port (163) and a fifth port; c) a first valve member (171) inside said valve body movable between at least two positions, a first position and a second position; and d) a second valve member (181) inside said valve body movable between at least two positions, a first position and a second position where a position of said first valve member (171) and a position of said second valve member (181) together define fluid communication between said inlet ports and said outlet ports through said void.

15. The valve of claim 14, said first valve member and said second valve member configured to cooperatively move between said first positions and said second positions.

16. The valve of claim 14, said first valve member and said second valve member configured to move independently between said first positions and said second positions.

17. The valve of any of claims 14 to 16, wherein: said first valve member (171) in said first position blocks fluid communication between said ambient inlet port (151) and said heat-exchanger cold-stream inlet outlet port (162) and in said second position blocks fluid communication between said ambient inlet port (151) and said fifth port, a compressor inlet outlet port (161); and said second valve member (181) in said first position blocks fluid communication between said compressor-outlet inlet port (152) and said exhaust outlet port (163) and in said second position blocks fluid communication between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162).

18. The valve of any of claims 14 to 16, wherein: said first valve member (171) in said first position blocks fluid communication between said compressor-outlet inlet port (152) and said exhaust outlet port (163) and in said second position blocks fluid communication between said fifth port, a heat- exchanger hot-stream outlet inlet port (153), and said exhaust outlet port (163); and said second valve member (181) in said first position blocks fluid communication between said ambient inlet port (151) and said heat-exchanger cold-stream inlet outlet port (162) and in said second position blocks fluid communication between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162).

19. The valve of any of claims 14 to 16, wherein: said first valve member (171) in said first position blocks fluid communication between said ambient inlet port (151) and said heat-exchanger cold-stream inlet outlet port (162) and in said second position blocks fluid communication between said ambient inlet port (151) and said fifth port, a compressor inlet outlet port (161) and said second valve member (181) in said first position blocks fluid communication between a sixth port, a heat-exchanger hot-stream outlet inlet port (153), and said heat-exchanger cold-stream inlet outlet port (162) and in said second position blocks fluid communication between said compressor-outlet inlet port (152) and said heat- exchanger cold- stream inlet outlet port (162).

20. The valve of claim 19, further comprising a component functionally associated with said heat-exchanger hot-stream outlet inlet port (153), allowing flow of fluid into said void through said heat-exchanger hot-stream outlet inlet port (153) and blocking flow of fluid from said void out through said heat-exchanger hot-stream outlet inlet port (153).

21. The valve of claim 20, wherein said component is a unidirectional valve (130).

22. The valve of claim 19, further comprising a bypass conduit providing fluid communication between said heat-exchanger hot-stream outlet inlet port (153) and said compressor inlet outlet port (161), and a third valve member (191) inside said valve body movable between at least two positions, a first position and a second position, wherein in said first position said third valve member (191) blocks fluid communication between said heat-exchanger hot-stream outlet inlet port (153) and said compressor inlet outlet port (161) through said bypass conduit; and in said second position said third valve member (191) blocks fluid communication between said heat-exchanger hot-stream outlet inlet port (153) and said exhaust outlet port (163).

23. The valve of claim 22, said first valve member, said second valve member and said third valve member configured to cooperatively move between said first positions and said second positions.

24. The valve of claim 22, wherein at least one of said first valve member, said second valve member and said third valve member is configured to move between said first position and said second position independently of at least one other said valve member.

25. The valve of any of claims 14 to 24, wherein at least one of said valve members is movable to at least one intermediate position between a respective said first position and respective said second position, thereby allowing fluid communication between a said inlet port and at least two said outlet ports.

26. The valve of any of claims 14 to 25 wherein at least one valve member is fashioned as an airfoil having an aerodynamic profile.

27. The valve of any of claims 25 to 26, wherein said second valve member (181) is movable to at least one said intermediate position, providing fluid communication between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162) and said exhaust outlet port (163).

28. The valve of any of claims 25 to 27, wherein said first valve member (171) is movable to a said intermediate position, providing fluid communication between said ambient inlet port (151) and said heat-exchanger cold- stream inlet outlet port (162) and a compressor outlet port (161).

29. The valve of any of claims 25 to 28, comprising a said third valve member (191), wherein said third valve member (191) is movable to a said intermediate position, providing fluid communication between a heat-exchanger hot-stream outlet inlet port (153) and said exhaust outlet port (163) and a said compressor-inlet outlet port (161).

30. The valve of any of claims 14 to 29, wherein at least one valve member is configured to vary a size of a fluid path between a said inlet port and a said outlet port while said valve member in a said first position and/or a said second position.

31. The valve of claim 30, wherein said second valve member (181) is configured to vary a size of a fluid path between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162) when in said first position.

32. The valve of any of claims 30 to 31, wherein said first valve member (171) is configured to vary a size of a fluid path between said ambient inlet port (151) and said heat- exchanger cold-stream inlet outlet port (162) when in said second position.

33. The valve of any of claims 30 to 32, further comprising an additional valve member (281) movable inside said valve body and configured to vary a size of a fluid path between said compressor-outlet inlet port (152) and said heat-exchanger cold-stream inlet outlet port (162).

34. The valve of any of claims 14 to 33, further comprising an additional valve member (271) movable inside said valve body and configured to vary a size of a fluid path between said ambient inlet port (151) and said heat-exchanger cold-stream inlet outlet port (162).

35. The valve of any of claims 14 to 34, further comprising a permeable section (140, 185) between a first region (121) and a second region (122) of said void, providing fluid communication between said first region and said second region.

36. The valve of claim 35, wherein said permeable section is unidirectional, allowing passage of fluid from said first region to said second region, and blocking passage of fluid from said second region to said first region.

37. A gas-turbine configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising a valve of any of claims 14 to 36.

38. The gas-turbine of claim 37, further configured to switch to an intermediate pressure mode between said high-pressure operation mode and said low-pressure operation mode.

39. A method of operating a gas-turbine according to an inverse Brayton cycle, comprising: a. providing a conduit allowing fluid communication between a compressor of the gas-turbine and a cold-stream inlet of a heat-exchanger of the gas-turbine; and b. during inverse Brayton cycle operation of the gas-turbine, directing fluid from said compressor to said heat-exchanger cold- stream inlet through said conduit so that a portion of the fluid entering said heat-exchanger cold-stream inlet is from said compressor.

40. The method of claim 39, further comprising: adjusting a size of said conduit so as to control an amount of fluid entering said cold-stream inlet from said compressor.

41. The method of any of claims 39 to 40, wherein between about 30% and about 70% by mass of the fluid entering the cold-stream inlet is from said compressor.

42. A gas-turbine comprising, when operating according to an inverse Brayton cycle, a. an air inlet configured to direct fluid into a cold-stream conduit of a heat- exchanger through a cold- stream inlet; b. conduits to direct fluid from said cold-stream conduit to a combustor, from said combustor to a turbine, from said turbine to a hot- stream conduit of said heat- exchanger, from said hot-stream conduit to a compressor, and from said compressor to an exhaust outlet ; and c. a conduit allowing passage of fluid from said compressor into said cold-stream inlet of said heat-exchanger.

43. The gas-turbine of claim 42, wherein said conduit allowing passage of fluid from said compressor into said cold-stream inlet is of fixed size.

44. The gas-turbine of any of claims 42 to 43, wherein a size of said conduit allowing passage of fluid from said compressor into said cold-stream inlet is adjustable.

45. The gas-turbine of any of claims 42 to 44, wherein said conduit allowing passage of fluid from said compressor into said cold-stream inlet is configured so that during operation of the gas-turbine according to an inverse Brayton cycle between about 30% and about 70% by mass of the fluid entering said cold-stream inlet is from said compressor.