EP2834478A2

EP2834478A2 - Device for power generation according to a rankine cycle

Info

Publication number: EP2834478A2
Application number: EP13717206.0A
Authority: EP
Inventors: Luc MAÎTREJEAN
Original assignee: Equitherm Sarl
Current assignee: Equitherm Sarl
Priority date: 2012-04-03
Filing date: 2013-04-02
Publication date: 2015-02-11
Also published as: CA2869061A1; WO2013150018A3; US20150082793A1; WO2013150018A2; WO2013150018A9

Abstract

A device for power generation according to a Rankine cycle, in particular according to an organic Rankine cycle (ORC), comprises a turbine (16), for expanding a vapour of a working fluid, and at least one heat exchanger (18, 20, 22), through which the expanded vapour has to flow. The turbine (16) and the heat exchanger(s) (18, 20, 22) are contained in a vapour tight container (10). The turbine (16) is a radial-outward-flow type turbine having a shaft that is led in a sealed manner out of said container (10), an axial vapour inlet port arranged opposite the shaft and located inside the container (10), and a stator exhaust ring with stator exhaust blades defining peripheral vapour exhaust openings for discharging the expanded vapour directly into the vapour tight container (10), in which the expanded vapour flows through the heat exchanger(s) (18, 20, 22).

Description

DEVICE FOR POWER GENERATION ACCORDING TO A RANKINE CYCLE

Technical Field:

[0001] The present invention generally relates to a device for power generation according to a Rankine Cycle, in particular to an Organic Rankine Cycle (ORC).

Background Art:

[0002] Due to the general necessity to reduce CO2 emissions and to the loss of trust in nuclear power plants, devices for producing electricity with low temperature sources are gaining of importance. Such low temperature sources include e.g. industrial waste heat, low temperature geothermal heat sources, low temperature biomass energy and low temperature solar energy, but also novel low temperature heat generators based on chemical or nuclear reactions.

[0003] Such devices generally work according to a so-called Organic Rankine Cycle (ORC), i.e. a Rankine cycle in which the working fluid is an organic fluid. The working principle underlying the ORC is basically the same as that of the classical Rankine cycle in which the working fluid is water. The main difference is that the ORC uses as working fluid an organic fluid with lower evaporation temperatures than water. It follows that for the same pressure, the evaporation of the organic fluid takes place at a lower temperature than the evaporation of water in a classical Rankine cycle. It follows that the external heat source in an ORC may be in a lower temperature range than the external heat source in a Rankine cycle working with water.

[0004] A basic ORC comprises following main steps. A condensate pump pressurizes in a liquid phase the condensed organic working fluid collected at a condenser. The pressurized organic working fluid is heated and evaporated in an evaporator, by heat exchange with an external heat source. It will be noted that the evaporation temperature in an ORC is generally lower than 200°C, most often in the range of 100°C to 160°C, and that the vapour is generally no super-heated. The vapour produced in the evaporator flows through an expansion machine, wherein its expansion generates a torque for driving an electrical generator. At the exhaust of the expansion machine, the vapour is condensed in the condenser, which is cooled by heat exchange with an external cold source. The condensate collected at the condenser is again pressurized in the condensate pump and pumped back into the evaporator.

[0005] Today, devices for power generation according to an ORC are commercially available mainly in a range starting with 0.3 MW electric power output, but there is an increasing need for such devices with a smaller electric power output too. In particular for the range of 25 kW to 250 kW electric (corresponding to a thermal recuperation range of about 150 kW to 1 ,5 MW), there seem to be interesting applications for producing electricity with low temperature sources using an ORC. However, with a decreasing nominal power of the device used for power generation, the investment costs per kW installed strongly increase and the efficiency of power generation decreases.

[0006] It is known that the efficiency of an ORC can be increased by using a so- called regenerator, i.e. a counter-current heat exchanger, which is arranged between the turbine outlet and the condenser inlet. Indeed, if the organic fluid is a "dry fluid", i.e. if it has a positive or isentropic saturation vapour curve, the vapour of the organic fluid has not reached the two-phase state when it leaves the turbine. It follows that the temperature of the expanded vapour is still considerably higher than the condensing temperature in the condenser. In the regenerator, this temperature difference is used to preheat the pressurized condensate before it enters into the evaporator.

[0007] If the external heat source is connected into the ORC with a heat carrier medium, which has to be cooled down in an evaporator working as counter-current heat exchanger, it is also known to operate an ORC with more than one evaporator. Each evaporator then works at a different evaporation pressure, i.e. with a different evaporation temperature, in combination either with a separate expansion machine for each evaporator or with a single multi-stage expansion machine, in which the vapour produced in each additional evaporator, is injected into an intermediate stage of the multi-stage expansion machine. Due to the fact that the heat transfer is split between evaporators working at different evaporation temperatures, one can work with a more important temperature differential on the side of the heat carrier medium, i.e. transform more heat into power. For power generation in the kW-range, such solutions are however considered to be a priori too expensive.

[0008] ORC systems with more than one evaporator are e.g. described in DE 10 2007 044 625 A1. According to a first embodiment, the system comprises several separate ORCs, each of these ORCs comprising an evaporator, a turbine, a condenser and a condensate pump. With regard to the heat carrier fluid, the evaporators are basically connected in series. With each evaporator is associated a turbine comprising its own housing with a nozzle system and blade wheels. These turbines are regrouped in pairs, wherein the blade wheels of a turbine pair have a common shaft. The parallel shafts of two turbine pairs are interconnected by a gear system to drive an electrical generator. According to a second embodiment described in DE 10 2007 044 625 A1 , the system comprises two evaporators associated with a two-stage turbine. This two-stage turbine comprises a rotor carrying two axially spaced blade rings, wherein the first blade ring has a smaller diameter than the second blade ring. A first steam flow (i.e. high pressure steam produced by a high pressure evaporator) radially enters into the turbine housing through a high pressure inlet and flows through a first annular channel radially into a first annular nozzle ring, which deflects the flow in an axial direction into the first blade ring, i.e. the blade ring with the smaller diameter. A second steam flow (low pressure steam produced by a low pressure evaporator) radially enters into the turbine housing through a low pressure inlet and flows through a second annular steam channel into a second nozzle ring, which deflects the flow in an axial direction into the second blade ring, i.e. the blade ring with the bigger diameter. The two stages are designed so as to achieve the same end pressure at the outlet of the first and second blade ring, wherein the exhaust streams are only merged in an outlet diffuser of the turbine. It is obvious that such a turbine has a rather low efficiency, when compared e.g. to a typical induction type turbine, i.e. a multi-stage axial turbine in which low pressure steam is induced into the main vapour stream at an intermediate turbine stage and both streams are thereafter commonly expanded. However, for power generation with an ORC in the kW- range, known induction type turbines are considered to be too expensive. [0009] The choice of the expansion machine has a major impact on the performance of the ORC, but also on the costs and therefore on the pay-back time of the power generation device. This is in particular true for power generation in the kW-range. The use of turbo-machines, generally axial flow turbines, seems to be limited to power ranges above 0.3 MW. Below 0.3 MW, displacement type machines, most often derived from existing frigorific compressors, are commonly used. Examples of displacement type machines used in ORCs at lower power ranges are e.g.: reciprocating piston machines, volumetric spiral turbines (also called scroll turbines) and screw-type machines. All these displacement type machines have a poor efficiency and generally involve lubrication problems. Furthermore, displacement type machines often cause problems due to a limited tightness.

[0010] For making power generation with an ORC in the kW-range a really interesting solution, it would be interesting to implement the ORC in a "black box", i.e. a preassembled ORC circuit that is integrated in a closed container and ready to be connected to the heat carrier fluid and the cooling fluid.

[001 1] Integrated heat exchanger systems for ORC applications have already been proposed. EP 1426565 A1 proposes e.g. an integrated thermal exchanger group for an ORC comprising a regenerator and a condenser, both arranged in a mainly cylindrical container with a horizontal axis. DE 10 2008 038 241 A1 proposes a similar arrangement. These integrated heat exchangers still require that the turbine and the evaporator are installed as separate components.

[0012] US 5,219,270 describes a recovery assembly for recovering energy from a wet oxidation. The assembly comprises a bulky reaction barrel with rocket nozzles mounted in a vacuum chamber equipped with tubular cooling elements.

[0013] GB 1 ,027,223 describes a multi-stage turbine, wherein a separate condenser is associated with each turbine stage. The turbine stages are axially spaced along a common shaft. Each turbine stage discharges the expanded vapour directly into a chamber containing its separate condenser. The turbine itself is not further described.

[0014] DE 10 2007 037 889 A1 describes a generator, a turbine, an evaporator and a condenser all mounted in a common housing. The turbine is of a mechanically rather complicated and thermodynamically rather inefficient design, generating for example high pressure drops in the steam circuit.

Summary of invention:

[0015] A device for power generation according to a Rankine cycle (RC), in particular according to an organic Rankine cycle (ORC), comprises a turbine for expanding a vapour of a working fluid and at least one heat exchanger, such as a regenerator and/or a condenser, through which the expanded vapour has to flow. In accordance with the invention, the device further comprises a vapour tight container containing the turbine and the at least one heat exchanger. The turbine is a radial-outward-flow type turbine having: a shaft that is led in a sealed manner out of the container; an axial vapour inlet port arranged opposite the shaft so as to be located inside the container; and a stator exhaust ring with stator exhaust blades defining peripheral vapour exhaust openings for discharging the expanded vapour directly into the vapour tight container, in which the expanded vapour flows through the at least one heat exchanger. It will be appreciated that the invention combines in a very efficient way, a very compact, but very efficient radial-outward- flow type turbine and at least one heat exchanger, which is to be traversed by the vapour expanded in the turbine, in a common vapour tight containment. The axial vapour inlet port is hereby arranged opposite the shaft and located inside the container, where it can be very easily connected to an internal vapour generator. The direct peripheral expanded vapour discharge through the stator exhaust ring with its stator exhaust blades into the common container substantially reduces pressure losses between the turbine and the at least one heat exchanger. The common container also reduces the risk of (organic) vapour losses to the atmosphere. The fact that a separate, vapour tight turbine housing is not necessary, reduces the costs and makes an up-sizing or down-sizing of the turbine much easier.

[0016] In a preferred embodiment, the container has the form of a vertical cylinder with a top end and a bottom end. In this case, the turbine is advantageously centred in the top end of the container, and the at least one heat exchanger is located below the turbine. It will be appreciated that this design provides ideal flow conditions for the expanded vapour between the exhaust of the turbine and the at least one heat exchanger.

[0017] A preferred embodiment of the turbine is a radial-outward-flow type multistage turbine with vapour induction in at least one intermediary stage. In this embodiment, an annular vapour inlet port advantageously surrounds the axial vapour inlet port, and is arranged in the turbine so as to annularly induce, in an intermediary stage of the turbine, a vapour stream from a second evaporator into an already partially expanded vapour stream from a first evaporator. It will be appreciated that the proposed radial-outward-flow type, multi-stage turbine can be very easily configured as an induction type turbine, wherein the manufacturing costs for the induction type turbine are not much higher than for a turbine with a single vapour inlet.

[0018] In a preferred embodiment, the device further includes a first evaporator and, optionally, a second evaporator. The first evaporator and, if present, the second evaporator are advantageously arranged in the container, axially below the axial vapour inlet port of the turbine. The at least one heat exchanger is then advantageously arranged annularly around the first evaporator and, if the second evaporator is present, annularly around the first and second evaporator. With such an arrangement, the device gets particularly compact. Furthermore, the intergration of the evaporator(s) into a common container with the turbine and at least one heat exchanger located downstream of the turbine, further reduces the risk of (organic) vapour losses to the atmosphere. Arranging the the evaporator(s) axially below the axial vapour inlet port of the turbine also alows to reduce pressure and heat losses between the evaporator(s) and the turbine. It remains to be noted that the evaporator that is arranged in the common container may also be a vapour generator comprising an internal heat source, e.g. a novel type of low temperature heat source, which is based on chemical or nuclear reactions.

[0019] A preferred embodiment of the device further comprises a first vapour drum that is located in axial extension of the axial vapour inlet port and directly connected to the latter without any intermediate piping. If the turbine is a multistage turbine with vapour induction in an intermediary stage, this embodiment further comprises a second vapour drum that is located in axial extension of the annular vapour inlet port and directly connected to the latter without any intermediate piping. In this case, the second vapour drum is a compartment inside the first vapour drum, or the first vapour drum is a compartment inside the second vapour drum. In such an embodiment, the axial vapour inlet port is advantageously formed by a first tubular vapour inlet connection, which is engaged in a sliding and sealed manner by the first vapour drum; and the annular vapour inlet port, if present, is advantageously formed by a second tubular vapour inlet connection surrounding the first tubular vapour inlet connection, wherein the second tubular vapour inlet connection is advantageously engaged in a sliding and sealed manner by the second vapour drum. If the first evaporator and second evaporator are— in this preferred embodiment— arranged axially below the axial vapour inlet port of the turbine, the first vapour drum and/or the second vapour drum are advantageously supported by the first evaporator and/or second evaporator or by a support structure associated with the first evaporator and/or second evaporator. Such combined low and high pressure vapour drums, which are connected without any intermediate piping and, preferably, with sliding connections to the turbine vapour inlets, reduce pressure losses at the vapour inlet(s) of the turbine, allow to easily achieve a superheating of the low pressure vapour by the high pressure vapour, thereby increasing efficiency of the Rankine cycle, make the device more compact, facilitate its assembling and reduce its costs.

[0020] In a preferred embodiment, the at least one heat exchanger includes a first regenerator that is arranged in the container so that the exhaust vapour of the turbine flows directly through it; this first regenerator being connected to a fluid inlet port of a first evaporator, so as to reheat the fluid with heat extracted from the exhaust vapour flowing through the first regenerator. The at least one heat exchanger may further include a second regenerator that is arranged in the container so that the vapour having crossed the first regenerator flows through it; this second regenerator being connected to a fluid inlet port of a second evaporator, so as to reheat the fluid with heat extracted from the vapour flowing through the second regenerator. Such a double-stage regeneration allows to significantly increase the efficiency of the Rankine cycle. [0021] The at least one heat exchanger may also include a condenser in which the expanded vapour is condensed, wherein, if present, the first regenerator, the second generator and the condenser are arranged below the turbine, vertically one above the other. This configuration is not only very compact. It also provides nearly ideal flow conditions for the vapour between the exhaust of the turbine, the regenerators and the condenser.

[0022] In a preferred embodiment, the device further includes a first evaporator connected to an axial vapour inlet port of the turbine, a second evaporator working at a lower evaporation pressure than the first evaporator and connected to an annular vapour inlet port of the turbine for inducing lower pressure vapour into an intermediary stage of the turbine; for the first evaporator, a first heat carrier fluid inlet port and a first heat carrier fluid outlet port; for the second evaporator, a second heat carrier fluid inlet port and a second heat carrier fluid outlet port; a connection pipe connecting the first heat carrier fluid outlet port to the second heat carrier fluid inlet port; and optionally, a bypass-valve connected between the second heat carrier fluid inlet port and the second heat carrier fluid outlet port, for adjusting the flow rate of the heat carrier fluid in the second evaporator. Such a configuration allows to further optimize the RC, and in particular the ORC.

[0023] In a preferred embodiment, the at least one heat exchanger includes a condenser, and a condensate collector is arranged under the condenser in the container. In this embodiment: a condensate outlet port is advantageously connected to the condensate collector; a first condensate inlet is advantageously connected either directly or through a first regenerator to a first evaporator; a second condensate inlet is advantageously connected, either directly or through a second regenerator, to a second evaporator; and a condensate pump is advantageously connected with its suction side to the condensate collector, and with its pressure side via a first valve to the first condensate inlet and via a second valve to the second condensate inlet. Such a configuration allows to further optimize the RC, and in particular the ORC.

[0024] In an alternative embodiment, the device includes an air-cooled condenser arranged outside the container connected to the container by means of a large diameter vapour pipe. The at least one heat exchanger then includes at least one regenerator arranged in the container so that the expanded vapour flows through it before being channelled through the large diameter pipe into the air-cooled condenser. It will be appreciated that even with an external air-cooled condenser, the device can remain very compact.

[0022] A preferred embodiment of the turbine comprises: a substantially plate- shaped first turbine housing part including the axial vapour inlet port; a set of stator rings with stator blades, the stator rings having increasing diameters and being prefereably fixed with screws onto the first turbine housing part; a stator exhaust ring with stator exhaust blades, the stator exhaust ring radially surrounding the stator ring with the biggest diameter and being preferably fixed with screws onto the first turbine housing part, the stator exhaust blades defining the vapour exhaust openings for discharging the expanded vapour into the container; a substantially plate-shaped second turbine housing part including a shaft outlet neck; the second turbine housing part being preferably fixed with screws onto the stator exhaust ring; a turbine shaft rotatably supported within the shaft outlet neck; a rotor disk supported in a cantilever manner by the turbine shaft between the first turbine housing part and the second turbine housing part; for each stator ring, a rotor ring with rotor blades, the rotor ring radially surrounding the corresponding stator ring and being fixed with screws onto the rotor disk. A main advantage of such a turbine design is that the turbine may be easily up-sized or down-sized, and that it may be easily fine-tuned to specific working parameters. Hence, an optimal turbine efficiency may nearly always be warranted.

[0025] The turbine advantageously includes an annular vapour inlet port formed in the first turbine housing part as a ring-zone with through-holes, the ring-zone separating a first ring-shaped flange, which supports a first set of stator rings, from a second ring-shaped flange, which supports a second set of stator rings. A vapour induction port may thus be added to the turbine with very simple means and at very low costs.

[0026] In a preferred embodiment, the turbine is an induction turbine comprising: a first turbine housing part including the axial vapour inlet port; a set of stator rings with stator blades supported by the first turbine housing part; a turbine shaft supporting in a cantilever manner a rotor disk; for each stator ring, a rotor ring with rotor blades, the rotor ring radially surrounding the corresponding stator ring and being supported by the rotor disk; an annular vapour inlet port formed in the first turbine housing part as a ring-zone with through-holes. These through-holes advantageously open onto an outer rim of one of the rotor rings, this outer rim having a width decreasing towards its periphery, and forming an annular, preferably concave, surface, which defines with an annular, preferably convex, surface on the next stator ring, a ring-shaped converging nozzle, for annularly inducing, into the next stator ring, a vapour stream from the through-holes into a vapour stream flowing through the preceding rotor ring. Thus, vapour induction is fluidically optimized at relatively low costs.

[0027] In a preferred embodiment of the turbine, the first turbine housing part supports an end-cap, which forms a vapour inlet deflection surface opposite the axial vapour inlet port; this vapour inlet deflection surface being a revolution surface centred on the central axis of the turbine; wherein a first stator ring is integrated into the end-cap.

[0028] In a preferred embodiment, the second turbine housing part is mounted in a sealed manner in an opening of the container, so that a shaft outlet neck of the second turbine housing part is located outside the container. In this embodiment, the turbine adavantageously further includes: rolling contact bearings in the shaft outlet neck for supporting and locating the turbine shaft therein; and a shaft sealing device located adjacent to the rolling contact bearings, so that the rolling contact bearings are sealed from the vapour in the turbine. Hence, the shaft bearings may be rather standard rolling contact bearings, which are easilly accessible outside the common container for monitoring and maintenance purposes.

Brief description of drawings:

[0029] The afore-described and other features, aspects and advantages of the invention will be better understood with regard to the following description of an embodiment of the invention and upon reference to the attached drawings, wherein: FIG. 1 : is a block diagram schematically illustrating how different components of a preferred device for power generation according to an improved organic Rankine cycle (ORC) are interconnected;

FIG. 2: is a schematic sectional view of a multi-stage turbine, in which low pressure vapour is induced at a low pressure turbine stage, the section plane containing the central axis of the turbine;

FIG. 3: is an enlarged detail of FIG. 2;

FIG. 4: is a schematic sectional view of a turbine as shown in FIG. 2, the section plane being this time perpendicular to the central axis of the turbine;

FIG. 5: is a schematic sectional view of the turbine as in FIG. 2, further schematically showing a first arrangement of a high pressure vapour drum and a low pressure vapour drum directly connected to the turbine;

FIG. 6: is a schematic sectional view as in FIG. 5, showing a slightly modified embodiment;

FIG. 7: is a schematic sectional view as in FIG. 5, showing a further possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine;

FIG. 8: is a schematic sectional view as in FIG. 5, showing an additional possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine;

FIG. 9: is a schematic sectional view of a device in accordance with the invention, the section plane being a vertical plane; and

FIG. 10: is a schematic sectional view of as indicated by line 9-9' in FIG. 9;

FIG. 9: is a schematic sectional view of a device in accordance with the invention, which is equipped with an air cooled condenser.

Detailed description of an embodiment of the invention

[0030] It will be understood that the following description and the drawings to which it refers describe by way of example preferred embodiments of the claimed subject matter for illustration purposes. The description and drawings shall not further limit the scope, nature or spirit of the claimed subject matter.

[0031] FIG. 1 is a block diagram schematically illustrating how different components of device for power generation according to an improved Organic Rankine Cycle (ORC) are interconnected. This device comprises following main components arranged within a closed vapour tight container 10: a first or high pressure evaporator 12, a second or low pressure evaporator 14; a turbine 16; a condenser 18 and two regenerators 20, 22. It further comprises a condensate pump 24 and an electrical generator 26, which are preferably arranged outside of the container 10.

[0032] The preferred device comprises moreover following fluid inlet and outlet ports:

- a first heat carrier fluid inlet port 30, respectively outlet port 30', connected to the heat carrier fluid inlet, respectively the heat carrier fluid outlet of the first evaporator 12;

- a second heat carrier fluid inlet port 32, respectively outlet port 32', connected to the heat carrier fluid inlet, respectively the heat carrier fluid outlet of the second evaporator 14;

- a cooling fluid inlet port 34, respectively outlet port 34' connected to the cooling fluid inlet, respectively the cooling fluid outlet of the condenser 18;

- a condensate outlet port 36;

- a first condensate inlet port 38; and

- a second condensate inlet port 40.

[0033] Reference number 42 identifies an external heat transfer circuit, associated e.g. with a low temperature external heat source. In this external heat transfer circuit 42 circulates a heat carrier fluid, such as a heat-transfer-oil, which transports the heat energy to be transformed by the ORC in mechanical energy. The heat carrier fluid enters through the first heat carrier fluid inlet port 30 into the first evaporator 12, traverses the latter, thereby heating and evaporating an organic working fluid flowing through the first evaporator 12. Thereafter, the heat carrier fluid leaves the container 10 through the first heat carrier fluid outlet port 30', to be channelled through an external connection conduit 44 to the second heat carrier fluid inlet port 32. Through this second heat carrier fluid inlet port 32, the heat carrier fluid enters into the second evaporator 14, traverses the latter, thereby heating and evaporating the organic working fluid flowing through the second evaporator 14. Thereafter, the heat carrier fluid definitively leaves the container 10 through the second heat carrier fluid outlet port 32'.

[0034] As an alternative to the external connection conduit 44, it is possible to foresee an internal connection conduit (not shown) located within the container 10, which would eliminate the first heat carrier fluid outlet port 30' and the second heat carrier fluid inlet port 32. However, the solution with the external first heat carrier fluid outlet port 30' and the second heat carrier fluid inlet port 32 warrants a greater flexibility. Thus, instead of connecting the first and second evaporator 12, 14 in series with regard to the heat carrier fluid, it is e.g. possible to connect the first evaporator 12 to a first heat transfer circuit (not shown), and the second evaporator 14 to a separate second heat transfer circuit (not shown).

[0035] In the embodiment shown in FIG. 1 , a bypass-valve 45 is moreover connected between the second heat carrier fluid inlet and outlet ports 32, 32'. This bypass-valve 45 allows limiting the flow of heat carrier fluid through the second evaporator 14, thereby limiting the At of the heat carrier fluid between the ports 30 and 32'. The more the bypass-valve 45 is opened, the higher the outlet temperature of the heat carrier fluid at port 32' and, consequently, the lower the At of the heat carrier fluid between the ports 30 and 32' will be.

[0036] The organic fluid vapour produced in the first evaporator 12, called hereinafter high pressure vapour, is channelled into a high pressure vapour drum 46, which is directly, i.e. without any intermediate piping, connected to a high pressure inlet of the turbine 16. The organic vapour produced in the second evaporator 14, which has a lower pressure than the organic vapour produced in the first evaporator 12 and is therefore called low pressure vapour, is channelled into a low pressure vapour drum 48, which is directly, i.e. without any intermediate piping, connected to a low pressure inlet of the turbine 16. In the turbine 16, both vapour streams are expanded to generate a torque for driving the generator 26 coupled to the turbine 16. [0037] To protect the turbine 16 against damage by organic fluid droplets impacting onto the turbine blades, the ORC cycle is generally designed so that the vapour at the turbine exhaust has not yet reached a two-phase state (to achieve this aim the organic fluid should preferably be a "dry" ORC working fluid, i.e. it should have a positive or isentropic saturation vapour curve). It follows that the temperature of the vapour at the outlet of the turbine 16 is still much higher than the condensing temperature in the condenser 18. In the two regenerators 20 and 22, this temperature difference is efficiently used to preheat the condensate before it enters into evaporator 12 or 14. More particularly, the first regenerator 20, which is heated directly with the exhaust vapour of the turbine 16, preheats the condensate stream pumped through the first evaporator 12, which works at a higher pressure and consequently also with a higher evaporating temperature than the second evaporator 14. The second regenerator 22, which is heated with the vapour already cooled down in the first regenerator 20, preheats the condensate stream pumped through the second evaporator 14, which works at a lower evaporating temperature. It will be appreciated that this two-stage regeneration allows a more efficient heat exchange in the regenerators 20, 22 and the evaporators 12, 14 than a single-stage regeneration.

[0038] In the condenser 18, the organic working fluid is condensed by means of an external cooling circuit 50 connected to the cooling fluid inlet port 34 and outlet port 34' of the condenser 18. Such an external cooling circuit 50 may e.g. comprise a dry or a wet cooling tower (not shown).

[0039] The condensate pump 24 pressurizes the condensed organic working fluid collected at the condenser 18 and pumps it through the regenerators 20, 22 to the two evaporators 12, 14. More particularly, at the outlet of the condensate pump 24, the pressurized condensate is split in two separate condensate streams. A first condensate stream is pumped through a first valve 52, which is connected to the first condensate inlet port 38. This first condensate stream flows through the first regenerator 20, wherein it is pre-heated by the exhaust vapour of the turbine 16, into the first evaporator 12. A second condensate stream is pumped through a second valve 54, which is connected the second condensate inlet port 40. This second condensate stream flows through the second regenerator 22, wherein it is pre-heated by the expanded vapour, into the second evaporator 14. The first and second valve 52, 54 allow to adjust the pressures in the evaporator 12 and 14 independently from one another. Alternatively, two separate condensate pumps can be used, one for pumping the first condensate flow through the first regenerator 20 into the first evaporator 12, and the other for pumping the second condensate flow through the second regenerator 22 into the second evaporator 14.

[0040] It will be understood that the pressures and temperatures depend on the characteristics of the heat carrier circuit 42, on the type of organic working fluid used in the ORC, on the characteristics of the available cooling circuit 50, and on the dimensioning of the heat exchangers 12, 14, 18, 20, 22, the turbine 16, and the condensate pump 24. Following values are listed for illustrating the ORC presented with a realistic example:

Heat carrier fluid in the external heat transfer circuit 42:

Type: customary heat-transfer-oil

Inlet temperature at 30: 180°C

Outlet temperature at 32': 75°C organic working fluid:

Type: Solkane® 365mfc produced by SOLVAY

First evaporation temperature:

Second evaporation temperature:

Vapour outlet temperature of the turbine 16:

Vapour outlet temperature of the first regenerator 20:

Vapour outlet temperature of the second regenerator 22:

Condensate temperature at the outlet of condenser 18:

Condensate temperature at the inlet of first evaporator 12:

Condensate temperature at the inlet of second evaporator 14

The efficiency of this two-stage ORC is about 15% for a At of 100°C, but about 1 1 % of the available energy in the heat carrier fluid is converted into mechanical energy. Without the low pressure circuit (i.e. without the second evaporator 14, the second regenerator 22, the low pressure vapour drum 48 and the low pressure vapour inlet of the turbine 16), the efficiency of the single stage ORC would be about 21 %, but only about 7% of the available energy in the heat carrier fluid would be converted into mechanical energy.

[0041] Typical temperature ranges for the heat carrier fluid are e.g.:

Inlet temperature of the heat carrier fluid: 140°C to 350°C

Outlet temperature of the heat carrier fluid: 66 to 150°C

[0042] In an alternative embodiment (not shown), the circuit of FIG. 1 only comprises the first regenerator 20, i.e. the second condensate inlet port 40 is directly connected to the second evaporator 14, without passing by a regenerator. In certain cases it may moreover be interesting to work without any regenerator. In this case, the first condensate inlet port 40 is directly connected to the first evaporator 14, and the second condensate inlet port 40 is directly connected to the second evaporator 14, without passing by a regenerator.

[0043] In a further embodiment (not shown), the circuit comprises in addition to the high pressure evaporator 12 more than one low pressure evaporator, each of these low pressure evaporators supplying the turbine 16 with vapour at a different intermediate pressure, which is induced into the turbine at a stage in which the pressure of the expanded vapour is about equal to the pressure of the induced vapour. In this multi-induction embodiment, a regenerator can be associated with each evaporator or only with one or more selected evaporators.

[0044] Finally, if the possible or desired At for the heat carrier fluid is rather small, it is also possible to work solely with the high pressure evaporator 12 and a turbine without low pressure inlet.

[0045] FIG. 2 is a schematic cross-section through an embodiment of the turbine 16 that is particularly suited for being used in an ORC as described above. It will first be noted that the turbine 16 is a multi-stage (here a three-stage) radial- outward-flow type turbine, i.e. the vapour axially enters into the turbine 16 and then flows in a radial direction outward through the different stages of the turbine 16, which are substantially concentric. The turbine is furthermore of the induction type, i.e. a secondary flow of low pressure vapour is induced at a low pressure stage into the turbine 16. Finally, the turbine is of the impulse type, i.e. the vapour is mainly expanded as it passes through the stator of the turbine 16.

[0046] As best seen in the cross-section of FIG. 4, each of the three turbine stages comprises a stator ring 56i, 562, 563, with increasing diameter and curved stator blades 58i, 582, 583, and a rotor ring 6Ο1, 6Ο2, 6Ο3, with increasing diameter and curved rotor blades 62i, 622, 623. The inlet stator ring 56i and the first rotor ring 6Ο1 form the first stage of the turbine 16. The second stator ring 562 and the second rotor ring 6Ο2 form the second stage of the turbine 16. The third stator ring

563 and the third rotor ring 6Ο3 form the third stage of the turbine 16. A fourth ring

56₄ surrounds the third or last stage of the turbine 16, to form a stator exhaust ring 56₄, with stator exhaust blades 58₄. It will of course be understood that the turbine 16 may also be designed with 4 stages or more, by adding one or more pairs of stator and rotor rings.

[0047] Referring now to FIG. 2, it will be noted that the rotor rings 6Ο1, 6Ο2, 6Ο3 are supported by a rotor disk 64, which is fixed to a free end of a turbine shaft 66. The turbine shaft 66 with the rotor disk 64 is rotatably supported in a cantilever fashion in a shaft outlet neck 72 by means of a bearing arrangement, preferably built up with rolling contact bearings. Reference number 68 points to a schematic representation of such a rolling contact bearing. Reference number 70 identifies a schematic representation of a sealing device, which seals the shaft 66 in the shaft outlet neck 72, between the rotor disk 64 and the bearing arrangement.

[0048] Reference number 74 identifies the central axis of the turbine shaft 66, which is also the central axis of all rotor rings 6Ο1, 6Ο2, 6Ο3 (and of all stator rings 56i, 562, 563, 56₄), since all these rings are coaxial with the turbine shaft 66. It will be noted that the rotor disk 64 is axially secured to the turbine shaft 66, e.g. by means of a nut 75 or a screw (not shown), and that the torque is transmitted from the rotor disk 64 to the turbine shaft 66 by means of a form-fit or keyed assembly (not shown). The rotor rings 6Ο1, 6Ο2, 6Ο3 are fixed with screws 76 to the rotor disk 64, so that they are easily exchangeable.

[0049] Still referring to FIG. 2, the stator rings 56i, 562, 563 are fixed with screws 78 to a plate-shaped first turbine housing part 80. This first turbine housing part 80 comprises a first and a second tubular vapour inlet connection 82, 84, a first and a second ring-shaped flange 88, 90 and a perforated ring zone 92. The first tubular vapour inlet connection 82 is centred on the central axis 74 of the turbine 16. The second tubular vapour inlet connection 84 surrounds the first tubular vapour inlet connection 82, so as to define with the latter an annular space 86, wherein the perforated ring zone 92 is contained in this annular space 86. The first ring-shaped flange 88 forms a shoulder around the first tubular vapour inlet connection 82. The second ring-shaped flange 90 forms a shoulder around the second tubular vapour inlet connection 84. The perforated ring zone 92 joins the first flange 88 and the second ring-shaped flange 90 and is provided with through-holes 94.

[0050] It will be noted that instead of being integral with the first turbine housing part 80, the first and/or second tubular vapour inlet connection 82, 84 could also be flanged to the first turbine housing part 80. In this case, the first turbine housing part 80 mainly consists of the first ring-shaped flange 88, the second ring-shaped flange 90 and the perforated ring zone 92, which joins the first and the second ring-shaped flange 88, 90. In this embodiment, the first ring-shaped flange 88 advantageously comprises a first connection means for flanging a removable first vapour inlet connection thereto, and the second ring-shaped flange 90 advantageously comprises a second connection means for flanging a removable second vapour inlet connection thereto (not shown in the drawings).

[0051] The first ring-shaped flange 88 supports the first and the second stator ring 56i, 562. The first stator ring 56i is advantageously part of an end-cap 96, which forms a vapour inlet deflection surface 98 at the end of the first tubular vapour inlet connection 82. This vapour inlet deflection surface 98 is a revolution surface centred on the central axis 74 of the turbine 16, so as to annularly deflect the axial vapour stream in the first tubular vapour inlet connection 82 by 90° into the first stator ring 56i.

[0052] The second ring-shaped flange 90 supports the third stator ring 563, as well as the exhaust stator ring 56₄. By means of the exhaust stator ring 56₄, the first turbine housing part 80 is fixed to a plate-shaped second turbine housing part 100. The rotor disk 64 with the rotor rings 6Ο1, 6Ο2, 6Ο3 is hereby located axially between the first housing part 80 and the second housing part 100. In the radial direction, the first rotor ring 6Ο1 is located between the first and the second stator ring 56i and 562; the second rotor ring 6Ο2 is located between the second and the third stator ring 562 and 563; and the third rotor ring 6Ο3 is located between the third stator ring 563 and the exhaust stator ring 56₄. It will be appreciated that— with this sandwich design— the height of the stator blades 58i , 582, 583 and rotor blades 62i , 622, 623 can be modified, by simply exchanging the removable stator rings 56 and rotor rings 60. Consequently, with one size for the first and second turbine housing part 80 and 100, the rotor disk 64 and the turbine shaft 66, one may already cover a large range of pressures and flow rates. Thus, it will be e.g. be possible to cover the electric power range of 25 kW to 100 kW with one unique size for the first and second turbine housing part 80 and 100, the rotor disk 64 and the turbine shaft 66. In most cases it will even not be necessary to change the form of the rotor and stator blades 58, 62. A broad electric power range may be covered by simply changing the height of the rotor and stator blades 58, 62, all other geometric characteristics of the rotor and stator rings 56, 60 and blades 58, 62 remaining unchanged. Furthermore, if the available heat energy increases or decreases during lifetime of the turbine, the latter may be easily reconfigured for the new operating conditions by simply exchanging its rotor and stator rings 56, 60.

[0053] As is best seen in FIG. 3, each of the three stator rings 56i , 562, 563 includes at its base an annular shoulder 102i , 1022, 1023, which forms a labyrinth joint 106 with an opposite grooved surface located on an annular outer rim 104i , 1042, 1043 of the corresponding rotor ring 6Ο1, 6Ο2, 6Ο3. Similarly, each of the first two rotor rings 6Ο1, 6Ο2 includes at its base an annular shoulder I O81, I O82, which forms a labyrinth joint 1 12 with an opposite grooved surface located on an annular outer rim HO2, 1 103 of the corresponding stator ring 562, 563. Thus, vapour tightness in the radial direction between the rotating and stationary parts is solely achieved by easily machinable surfaces on the removable stator rings 56i , 562, 563 and rotor rings 6Ο1, 6Ο2, and necessitates neither complicated machining on the turbine housing parts 80, 100 or the rotor disk 64, nor separate sealing elements. Furthermore, if the removable rotor and stator rings 56, 60 are replaced, all sealing surfaces in the turbine are replaced too. Alternatively, the removable stator rings 56i , 562, 563 and rotor rings 6Ο1, 6Ο2, may be designed without the aforementioned annular shoulder, wherein the outer rims 104i , 1042, 1043 of the rotor rings 6O1, 6Ο2, 6Ο3 and the outer rims H O2, 1 103 of the stator rings 562, 563 cooperate directly with corresponding annular surfaces on the housing part 80 and the rotor disk 64 to form labyrinth joints.

[0054] It will further be noted that the annular shoulder 1022 of the second stator ring 562 is smaller than the other two annular shoulders 102i, 1023, thereby leaving uncovered the through-holes 94 in the perforated ring zone 92 of the first turbine housing part 80. The width of the annular outer rim 1042 of the second rotor ring 6Ο2, which is located just behind the perforated ring zone 92, decreases towards its periphery, so as to define with the opposite surface of the third stator ring 563 a ring-shaped converging nozzle 1 14, which is delimited, on one side, by an annular concave surface 1 16 defined by the second rotor ring 6Ο2 and, on the other side, by an annular convex surface 1 18 defined by the third stator ring 563. This ring-shaped nozzle 1 14 deflects the low pressure vapour stream, which flows from the annular space 86 in an axial direction through the through-holes 94, by an angle of 90° into the third stator ring 563. In this third stator ring 563, this low pressure vapour stream is induced into the main vapour stream that has already been expanded in the first and second stage of the turbine 16, so that both vapour streams have substantially the same pressure when they merge in the third stator

[0055] Referring simultaneously to FIG. 2 and FIG. 4, it will be noted that the expansion of the vapour in the second stator ring 562 and the third stator ring 563 is mainly achieved by increasing the height of the stator blades 58 in the radial direction (i.e. the height of these blades at the outlet is considerably higher than their height at the inlet of the stator ring). Thus, the expansion of the vapour in these stator rings 562 and 563 is mainly determined by the increasing height of their blades. Consequently, for adapting the turbine to a different vapour throughput or a different inlet pressure in the turbine 16, it will not be necessary to entirely change the geometry of the rotor or stator blades 58, 62. It will most often simply be sufficient to change the height of the rotor and stator blades 58, 62, all other geometric characteristics of the rotor and stator rings 56, 60 and blades 58, 62 remaining basically unchanged. [0056] It will be appreciated that the turbine as described hereinbefore may achieve an isentropic efficiency as high as 90%. Its rotation speed will preferably be limited to 18,000 rpm, so to be capable of working with rolling contact bearings and common shaft sealing devices.

[0057] FIG. 5 schematically shows a first arrangement of the high pressure vapour drum 46 and the low pressure vapour drum 48, both directly located under the turbine 16 and directly connected to latter without any intermediate piping. The high pressure vapour drum 46 is a cylindrical vessel directly flanged to the first turbine housing part 80. The low pressure vapour drum 48 forms an annular compartment within the high pressure vapour drum 46. This annular compartment is outwardly delimited by a cylindrical external wall 120 of the high pressure vapour drum 46 and inwardly delimited by a cylindrical internal wall 122. This cylindrical internal wall 122 engages the first tubular vapour inlet connection 82 of the turbine 16 in a sealed fit, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the cylindrical internal wall 122 and the first tubular vapour inlet connection 82. The high pressure vapour flows through the axial passage delimited by the cylindrical internal wall 122 into the first tubular vapour inlet connection 82 of the turbine. The low pressure vapour flows directly from the annular low pressure vapour drum 48 into the annular space 86 delimited between the first tubular vapour inlet connection 82 and the second tubular vapour inlet connection 84 of the turbine. Reference number 124 points to a high pressure vapour inlet pipe connected laterally to the high pressure vapour drum 46, whereas reference number 126 points to a low pressure vapour inlet pipe connected laterally to the low pressure vapour drum 48.

[0058] The arrangement of FIG. 6 distinguishes over the arrangement of FIG. 5 mainly in that the low pressure vapour inlet pipe 126' traverses the high pressure vapour drum 46 to leave the latter through its bottom wall. This design necessitates that the low pressure vapour inlet pipe 126 and the high pressure vapour drum 46 may freely expand relative to one another. This can e.g. be achieved by connecting the low pressure vapour inlet pipe 126 by means of a bellow expansion joint (not shown) to the closed end of the high pressure vapour drum 46. [0059] FIG. 7 shows a further arrangement of the high pressure vapour drum 46 and the low pressure vapour drum 48 connected to the turbine 16. The low pressure vapour drum 48 is a cylindrical vessel flanged to the first turbine housing part 80. The high pressure vapour drum 46 forms a cylindrical compartment within the low pressure vapour drum 48, separated from the outer wall of the latter by an annular space 130. It is vertically supported by a support flange 132, which is welded into the low pressure vapour drum 48. Through-openings 134 in the support flange 132 allow the intermediate pressure vapour to pass from an inlet compartment 136 of the low pressure vapour drum 48 into the annular space 130. The high pressure vapour drum 46 engages the first tubular vapour inlet connection 82 of the turbine 16 in a sealed way, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the high pressure vapour drum 46 and the first tubular vapour inlet connection 82. Similarly as for the pipe 126' in the embodiment of FIG. 6, the passage of the pipe 124 through the bottom wall of the low pressure vapour drum 48 is designed for allowing a relative axial expansion of both components.

[0060] It will be noted that in FIG. 5, 6 and 7, the outer vessel is flanged to the first turbine housing part 80 of the turbine 16, and must consequently be able to axially expand away from the turbine 16. In FIG. 8, the outer vessel 140 is no longer flanged to the first turbine housing part 80 of the turbine 16. It simply engages the second tubular vapour inlet connection 84 of the turbine 16 in a sealed way, wherein this sealed fit is designed (e.g. with O-rings) to allow a relative axial movement of the outer vessel 140 and the second tubular vapour inlet connection 84. In this embodiment, the outer vessel 140 (which may be the high pressure vapour drum 46 as in FIG. 5 or 6, or the low pressure vapour drum 48 as in FIG. 7) can be vertically supported by a separate vertical support means 142. Thus, the outer vessel 140 may e.g. be directly supported on the first or second evaporator 12, 14, when the latter are axially arranged under the outer vessel 140. It will consequently be appreciated that in the embodiment of FIG. 7, the turbine 16 must not support the whole weight of the two vapour drums 46, 48.

[0061] It will be appreciated that in all three arrangements, the low pressure vapour is slightly superheated by contact with one or more walls of the high pressure vapour drum 46, which may be advantageous for the efficiency of the low pressure cycle. This superheating-effect is more important for the embodiment of FIG. 7 and may be further amplified by providing the outer wall of the inner cylinder 46 in FIG. 7 with fins.

[0062] FIG. 9 and 10 show a compact device for electric power generation according to an improved ORC, more particularly, to an ORC working with two evaporators 12, 14, two regenerators 20, 22 and an induction turbine 16, so as illustrated with the circuit of FIG. 1. The container 10 is a vertical vapour tight cylinder supported on support feet 150. The turbine 16 is located inside the vertical cylinder 10, near the top end of the latter. The central axis 74 of the turbine is aligned with the central axis of the container 10. Referring back to FIG. 2, it will be noted that the second turbine housing part 100 is fixed with in a sealed manner to a head-plate 152, which is a part of the upper container wall. The shaft outlet neck axially protrudes out of an opening 153 of the head-plate 152. Alternatively, the second turbine housing part 100 may include an annular flange (not shown) with which it is fixed in a sealed manner onto a flange surrounding an axial opening (not shown) in the head of the container 10. In this case the entire second turbine housing part 100 is located outside the container 10. A generator 154 is arranged on the top of the vertical cylinder 10 and is coupled to the vertical shaft of the turbine 16. It will be appreciated that with this arrangement, the bearing arrangement 68 of the turbine shaft 66 is located completely outside the container 10, which greatly facilitates the design of its lubrication system, but also its maintenance.

[0063] The high pressure vapour drum 46 and the low pressure vapour drum 48 are arranged axially directly under the turbine 16. Both vapour drums 46, 48 are advantageously connected to the first and second tubular vapour inlet connection 82, 84 of the turbine 16 as described e.g. with reference to FIG. 5 or 6 and FIG. 8. The first evaporator 12 and the second evaporator 14 are arranged axially directly under the two vapour drums 46, 48, which can be vertically supported by the two evaporators 12, 14, as described with reference to FIG. 8. These two evaporators 12, 14 are preferably enclosed in a separate cylindrical compartment 156. The first and second regenerator 20, 22 are arranged annularly around the two vapour drums 46, 48, wherein the second regenerator 22 is arranged directly under the first regenerator 20. The condenser 18 is arranged annularly around the two evaporators 12, 14. The bottom part of the vertical cylinder 10 forms a condensate collector 158.

[0064] The turbine 16, which is preferably conceived substantially as described hereinbefore, radially discharges the expanded vapour through the stator exhaust ring 56₄ directly into the upper part of the vertical cylinder 10. An annular deflector (not shown) may be used to deflect the radially discharged vapour axially downwards. This annular deflector may be incorporated into the turbine 16 or be installed as a separate element into the container 10. The expanded vapour then passes downwards through the first and second regenerator 20, 22, to be finally condensed in the condenser 18. The condensate is collected in the condensate collector 158 at the bottom of the vertical cylinder 10.

[0065] The pipe connections 30, 30', 32, 32', 34, 34', 36 and 38 shown in FIG. 9 correspond to the inlet/outlet ports with the same reference numbers shown in FIG. 1.

[0066] FIG. 10 is a horizontal cross-section of the device shown in FIG. 9. This FIG. 10 shows that the annular heat-exchangers 18, 20, 22 do not occupy the whole annular space around the separate cylindrical compartment 156 in which the evaporators 12, 14 are arranged. The free space, here an angular segment of about 40°, is used for arranging therein piping and auxiliary equipment, which is only schematically represented in FIG. 10 and identified therein with reference number 160.

[0067] FIG. 1 1 shows an alternative embodiment with an air-cooled condenser 170 installed outside the container 10, which still contains the evaporators 12, 14, the regenerators 20, 22, the vapour drums 46, 48, and the turbine 16, which are advantageously arranged in this container 10 as described hereinbefore with reference to FIG. 9. The bottom half of the container 10, which was occupied by the condenser 18 in the embodiment of FIG. 9, is now empty and connected via a large diameter pipe 172 to the air-cooled condenser 170. The latter includes a central chimney 174 with a closed end 176, which is connected to at least one upper vapour collector 178. From this upper vapour collector 178 the vapour streams through at least one air-cooled condensing heat exchanger 180, which condenses the vapour. The condensate is collected in at least one lower condensate collector 182 and evacuated back into the condensate collector 158 in the container 10 through a condensate line 184. Condensate that is already formed in the central chimney 174 flows back into the condensate collector 158 in the container 10 through the large diameter pipe 172. Reference number 186 identifies a fan for creating an air flow 188 through the condensing heat exchanger(s) 180 and along the outer wall of the chimney 174, which may be equipped with cooling fins too.

Reference signs list

10 container 561, first stator ring,

12 first evaporator 562, second stator ring,

14 second evaporator 563 third stator ring

16 turbine 56₄ stator exhaust ring (58)

18 condenser 581, curved stator blades (58) of 56i 20 first regenerator 582, curved stator blades (58) of 562 22 second regenerator 583 curved stator blades (58) of 563 24 condensate pump 58₄ stator exhaust blades

26 electrical generator 6Ο1, first rotor ring,

30 first heat carrier fluid inlet port of 6Ο2, second rotor ring,

12 6Ο3 third rotor ring

30' second heat carrier fluid inlet 621, curved rotor blades of 6Ο1

port of 12 622, curved rotor blades of 6Ο2

32 first heat carrier fluid inlet port of 623 curved rotor blades of 6Ο3

12 64 rotor disk

32' second heat carrier fluid inlet 66 turbine shaft

port of 14 68 bearing

34 cooling fluid outlet port of 18 70 sealing device

34' cooling fluid outlet port of 18 72 shaft outlet neck

36 condensate outlet port 74 central axis of 16

38 first condensate inlet port 75 nut

40 second condensate inlet port 76 screws for rotor rings

42 external heat transfer circuit in 78 screws for stator rings (56) which circulates a heat carrier 80 first turbine housing part (80) fluid 82 first tubular vapour inlet

44 external connection conduit connection

45 bypass-valve 84 second tubular vapour inlet

46 high pressure vapour drum connection

48 low pressure vapour drum 86 annular space (between 82 and 50 external cooling circuit of 18 84)

52 first valve (connected to 38) 88 first ring-shaped flange (on 82)

54 second valve (connected to 40) 90 second ring-shaped flange (on 122 cylindrical internal wall 84) 124 high pressure vapour inlet pipe

92 perforated ring zone 126 low pressure vapour inlet pipe

94 through-holes in 92 130 annular space

96 end-cap 132 support flange

98 vapour inlet deflection surface 134 through openings in 132

100 second turbine housing part 136 inlet compartment

(100) 140 outer vessel

1021, annular shoulder on 56i, 562, 142 vertical support means

102₂, 56₃ 150 support feet

102₃ 154 generator

104i, annular outer rim on 6Ο1 , 6Ο2, 156 separate cylindrical

104_2> 60s compartment

104₃ 158 condensate collector

106 labyrinth joint 160 piping and auxiliary equipment

I O81 , annular shoulder on 6Ο1 , 6Ο2 170 air-cooled condenser

I O82 172 large diameter pipe

H O2, annular outer rim on 562, 563 174 central chimney

1 103 176 closed end of 174

1 12 labyrinth joint 178 upper vapour collector

1 14 ring-shaped nozzle 180 condensing heat exchanger

1 16 annular concave surface defined 182 lower condensate collector by 6Ο2 184 condensate line

1 18 annular convex surface defined 186 fan

120 cylindrical external wall

Claims

1. A device for power generation according to a Rankine cycle, in particular

according to an organic Rankine cycle (ORC), comprising:

a turbine (16) for expanding a vapour of a working fluid; and

at least one heat exchanger (18, 20, 22) through which the expanded vapour has to flow; and

a vapour tight container (10) containing said turbine (16) and said at least one heat exchanger (18, 20, 22),

wherein said turbine (16) has a shaft (66) that is led in a sealed manner out of said container (10) and discharges the expanded vapour directly into said vapour tight container (10), in which the expanded vapour flows through said at least one heat exchanger (18, 20, 22);

characterized in that

said turbine (16) is a radial-outward-flow type turbine having:

an axial vapour inlet port (82) arranged opposite said shaft and located inside the container (10); and

a stator exhaust ring (56₄) with stator exhaust blades (58₄) defining peripheral vapour exhaust openings for discharging the expanded vapour directly into said vapour tight container (10).

2. The device as claimed in claim 1 , wherein:

said container (10) has the form of a vertical cylinder with a top end and a bottom end;

said turbine (16) is centred in said top end of said container (10); and said at least one heat exchanger (18, 20, 22) is located below said turbine.

3. The device as claimed in claim 1 or 2, wherein:

said turbine (16) is a radial-outward-flow type multi-stage turbine with vapour induction in at least one intermediary stage, with an annular vapour inlet port (84) surrounding said axial vapour inlet port (82), said annular vapour inlet port (84) being arranged in said turbine (16) so as to annularly induce, in an intermediary stage of said turbine (16), a vapour stream from a second evaporator (14) into an already partially expanded vapour stream from a first evaporator (12).

4. The device as claimed in anyone of claims 1 to 3, including a first evaporator (12) and, optionally, a second evaporator (12), wherein:

said first evaporator (12) and, if present, said second evaporator (14) are arranged in said container (10), axially below said axial vapour inlet port (82) of said turbine (16); and

said at least one heat exchanger (18, 20, 22) is arranged annularly around said first evaporator (12) and, if said second evaporator (14) is present, annularly around said first and second evaporator (14).

5. The device as claimed in anyone of claims 1 to 4, further comprising:

a first vapour drum (46) that is located in axial extension of said axial vapour inlet port (82) and directly connected to the latter without any intermediate piping; and

if said turbine is a multi-stage turbine with vapour induction in an intermediary stage, a second vapour drum that is located in axial extension of said annular vapour inlet port (84) and directly connected to the latter without any

intermediate piping, wherein said second vapour drum (48) is a compartment inside said first vapour drum (46), or said first vapour drum (46) is a

compartment inside said second vapour drum (48).

6. The device as claimed in claim 5, wherein:

said axial vapour inlet port is formed by a first tubular vapour inlet connection (82), which is engaged in a sliding and sealed manner by said first vapour drum (46); and

said annular vapour inlet port, if present, is formed by a second tubular vapour inlet connection (84) surrounding said first tubular vapour inlet connection; said second tubular vapour inlet connection is engaged in a sliding and sealed manner by said second vapour drum (48), and, if said first evaporator (12) and second evaporator (14) are arranged axially below said axial vapour inlet port (82) of said turbine (16), said first vapour drum (46) and/or said second vapour drum (48) are supported by said first evaporator (12) and/or second evaporator (14) or by a support structure associated with said first evaporator (12) and/or second evaporator (14).

7. The device as claimed in anyone of claims 1 to 6, said at least one heat exchanger (18, 20, 22) includes:

a first regenerator (20) that is arranged in said container (10) so that the exhaust vapour of said turbine (16) flows directly through it, said first regenerator (20) being connected to a fluid inlet port of a first evaporator (12), so as to reheat said fluid with heat extracted from the exhaust vapour flowing through said first regenerator (20); and

optionally, a second regenerator (22) that is arranged in said container (10) so that the vapour having crossed said first regenerator (20) flows through it, said second regenerator (22) being connected to a fluid inlet port of a second evaporator (14), so as to reheat said fluid with heat extracted from the vapour flowing through said second regenerator (22); and/or

a condenser (18) in which said expanded vapour is condensed;

wherein, if present, said first regenerator (20), said second generator (22) and said condenser (18) are arranged below said turbine (16), vertically one above the other.

8. The device as claimed in anyone of the preceding claims, further including: a first evaporator (12) connected to an axial vapour inlet port (82) of said turbine (16);

a second evaporator (14) working at a lower evaporation pressure than said first evaporator (12) and connected to an annular vapour inlet port (84) of said turbine (16) for inducing lower pressure vapour into an intermediary stage of said turbine;

for said first evaporator (12), a first heat carrier fluid inlet port (30) and a first heat carrier fluid outlet port ;

for said second evaporator (14), a second heat carrier fluid inlet port (32) and a second heat carrier fluid outlet port ;

a connection pipe (44) connecting said first heat carrier fluid outlet port to said second heat carrier fluid inlet port (32); and

optionally, a bypass-valve (45) connected between said second heat carrier fluid inlet port (32) and said second heat carrier fluid outlet port , for adjusting the flow rate of the heat carrier fluid in said second evaporator (14).

9. The device as claimed in claim 8, wherein:

said at least one heat exchanger (18, 20, 22) includes a condenser (18);

a condensate collector (158) is arranged under said condenser (18) in said container (10);

a condensate outlet port (36) is connected to said condensate collector;

a first condensate inlet (38) is connected either directly or through a first regenerator (20) to a first evaporator (12);

a second condensate inlet (40) is connected either directly or through a second regenerator (22) to a second evaporator (14); and

a condensate pump (24) is connected with its suction side to said condensate collector (36), and with its pressure side via a first valve (52) to said first condensate inlet (38) and via a second valve (54) to said second condensate inlet (40).

10. The device as claimed in anyone of the preceding claims, including:

an air-cooled condenser (170) arranged outside said container (10) and connected to said container (10) by means of a large diameter pipe (172); wherein said at least one heat exchanger (18, 20, 22) includes at least one regenerator (20, 22) arranged in said container (10) so that the expanded vapour flows through it before being channelled through said large diameter pipe (172) into said air-cooled condenser (170).

1 1. The device as claimed in anyone of the preceding claims, wherein said turbine (16) comprises:

a substantially plate-shaped first turbine housing part (80) including said axial vapour inlet port (82);

a set of stator rings (56) with stator blades (58), said stator rings (56) having increasing diameters and being fixed with screws onto said first turbine housing part (80);

said stator exhaust ring (56₄) radially surrounding the stator ring with the biggest diameter and being fixed with screws onto said first turbine housing part (80), said stator exhaust blades defining said vapour exhaust openings for discharging the expanded vapour into said container (10);

a substantially plate-shaped second turbine housing part (100) including a shaft outlet neck (72); said second turbine housing part (100) being fixed with screws onto said stator exhaust ring (58);

a turbine (16) shaft rotatably supported within said shaft outlet neck (72);

a rotor disk (64) supported in a cantilever manner by said turbine (16) shaft between said first turbine housing part (80) and said second turbine housing part (100);

for each stator ring (56), a rotor ring (60) with rotor blades (62), said rotor ring (60) radially surrounding the corresponding stator ring (56) and being fixed with screws onto said rotor disk (64).

12. The device as claimed in claim 1 1 , wherein:

said turbine (16) includes an annular vapour inlet port (84) formed in said first turbine housing part (80) as a ring-zone (92) with through-holes (94), said ring- zone (92) separating a first ring-shaped flange (88), which supports a first set of stator rings (56), from a second ring-shaped flange (90), which supports a second set of stator rings (56).

13. The device as claimed in anyone of the preceding claims, wherein said turbine (16) comprises:

a first turbine housing part (80) including said axial vapour inlet port (82);

a set of stator rings (56) with stator blades (58) supported by said first turbine housing part (80);

a turbine (16) shaft supporting in a cantilever manner a rotor disk;

for each stator ring (56), a rotor ring (60) with rotor blades (62), said rotor ring (60) radially surrounding the corresponding stator ring (56) and being supported by said rotor disk (64);

an annular vapour inlet port (84) formed in said first turbine housing part (80) as a ring-zone (92) with through-holes (94);

wherein said through-holes (94) open onto an outer rim (1042) of one of said rotor rings (60), said outer rim (1042) having a width decreasing towards its periphery, and forming an annular, preferably concave, surface, which defines with an annular, preferably convex, surface on the next stator ring (56), a ring- shaped converging nozzle (1 14), for annularly inducing, into said next stator ring (56), a vapour stream from said through-holes (94) into a vapour stream flowing through the preceding rotor ring (60).

14. The device as claimed in anyone of claims 1 1 to 13, wherein said first turbine housing part (80) supports an end-cap (96), which forms a vapour inlet deflection surface (98) opposite said axial vapour inlet port (82), said vapour inlet deflection surface (98) being a revolution surface centred on said central axis (74) of the turbine (16), wherein a first stator ring (56i) is integrated into said end-cap (96).

15. The device as claimed in anyone of claims 10 to 14, wherein said second

turbine housing part (100) is mounted in a sealed manner in an opening of said container (10), so that a shaft outlet neck (72) of said second turbine housing part (100) is located outside said container (10), and said turbine (16) further includes:

rolling contact bearings in said shaft outlet neck (72) for supporting and locating said turbine (16) shaft therein; and

a shaft sealing device located adjacent to said rolling contact bearings, so that said rolling contact bearings are sealed from the vapour in the turbine (16).