GB2526090A

GB2526090A - Turbine generator

Info

Publication number: GB2526090A
Application number: GB1408393.5A
Authority: GB
Inventors: Pierre Bernard French; Mark Bargent
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2014-05-12
Filing date: 2014-05-12
Publication date: 2015-11-18
Anticipated expiration: 2034-05-12
Also published as: GB201408393D0; GB2526090B

Abstract

A turbine generator 100 comprising a shaft 110 mounted to rotate about an axis 99, and two or more turbine wheels 120 130, which are rotatably driven by separate fluid flows. The turbine wheels are coupled to the shaft 110 such that the rotation of the turbine wheels rotates the shaft 110 about its axis 99. The turbine generator further comprising an electrical generator 140 having a rotor 141 and a stator 142, the shaft 110 being coupled to the rotor 141 such that the rotation of the shaft rotates the rotor relative to the stator to generate electricity. The separate fluid flows that drive the turbine wheels may be from the exhaust gas from an internal combustion engine 10 and/or from a flow of working fluid of a waste heat recovery system 150 of an engine system. The use of two turbine wheels driven by separate fluid flows to power a single generator allows for a less complex and more compact overall design.

Description

Turbine Generator The present invention relates to a turbine generator and particularly, but not exclusively, relates to a turbine generator that forms part of an engine system. The present invention also relates to an engine system comprising a turbine gcnerator.

Turbine generators are well known and comprise a turbine wheel that is arranged to be driven by a fluid. The turbine wheel is connected to a rotor of an electrical generator via a shaft which is supported for rotation by one or more bearings. A stator of the electrical generator is arranged around the rotor so that movement of the rotor induces an electromotive force in the stator.

A turbine generator may form part of an engine system. The engine system may for example comprise an internal combustion engine and a turbine generator.

It is an object of the invention to provde a turbine generator that at least partially addresses one or more problems or disadvantages present in the prior art.

According to a first aspect of the present invention there is provided a turbne generator comprising a shaft mounted to rotate about an axis; two or more turbine wheels, wherein each of the two or more turbine wheels is arranged to be rotatably driven by a separate flow of fluid and is coupled to the shaft such that the rotation of the turbine wheel rotates the shaft about its axis; and an electrical generator comprising a rotor and a stator, the shaft being coupled to the rotor such that the rotation of the shaft rotates the rotor relative to the stator to generate electricity.

The present invention allows two or more turbine wheels that are driven by separate flows of fluid to driveably rotate a single shaft and drive a single electrical generator.

This provides an apparatus which is less complex and more compact than would be the case if two or more separate electrical generators with respective turbine wheels and shafts were to be used to generate electricity using separate flows of fluid.

One or more of the turbine wheels may be so coupled to the shaft by being mounted directly on the shaft. Each of the two or more turbine wheels may be so coupled to the shaft by being mounted directly on the shaft. Advantageously, this may alow the shaft and two or more turbine wheels to be more easily balanced.

Alternatively, or additionally, one or more of the turbine wheels may be so coupled to the shaft by a mechanical transmission. In this case, the one or more of the turbine wheels may be mounted on a respective turbine shaft that is different to said shaft of the turbine generator.

The mechanical transmission may include any suitable mechanical gearing arrangement. In this respect, one or more of the turbine wheels may be driveably connected to a gear that is engageable with a complementary gear that is driveably connected to the shaft.

Where one or more of the turbine wheels is coupled to the shaft by a mechanical transmission, the one or more of the turbine wheels may be arranged to selectively driveably rotate the shaft.

In this respect, the one or more of the turbine wheels may be provided with a mechanism for switching between an engaged position in which rotation of the one or more of the turbine wheels rotates the shaft and a unengaged position in which rotation of the one or more of the turbine wheels does not rotate the shaft. The mechanism for switching the one or more of the turbine wheels between the engaged position and the unengaged position may comprise a clutch arranged to couple the one or more of the turbine wheels and the shaft. Alternatively, or additionally, the one or more turbine wheels may be movable such that in the engaged position it is in contact with the shaft, or a mechanical coupling connected to the shaft, and in the unengaged position it is not in contact with the shaft, or a mechanical coupling connected to the shaft.

One or more of the turbine wheels may be arranged to be driven by a flow of exhaust gas from an internal combustion engine of an engine system.

One or more of the turbine wheels may be arranged to be driven by a flow of a working fluid of a waste heat recovery system of an engine system. The waste heat recovery system may be a closed loop system. The waste heat recovery system may operate on the basis of the Rankine cycle. Alternatively, or additionally, the waste heat recovery system may operate on the basis of any other suitable type of thermodynamic cycle, including the Carnot or Brayton thermodynamic cycles. The working fluid may be a refrigerant.

The waste heat recovery system may be selectively adjustable between an operating state in which the working fluid flows around the system and a non-operating state in which the working fluid does not flow around the system. In the non-operating state the working fluid may not drive the one or more turbine wheels.

The two or more turbine wheels may comprise a first turbine wheel arranged to be driven by a flow of exhaust gas from an internal combustion engine and a second turbine wheel is arranged to be driven by a flow of a working fluid of a waste heat recovery system.

The first turbine wheel may be disposed between the second turbine wheel and the electrical generator. Alternatively, the second turbine wheel may be disposed between the first turbine wheel and the electrical generator.

The electrical generator may be disposed between the first and second turbine wheels.

Advantageously this facilitates an arrangement of the first and second turbine wheels such that the respective flows of fluid that drive the turbines are exhausted without impeding each other.

Each turbine wheel may be mounted within a respective turbine housing for rotation about an axis, wherein the turbine housing defines an inlet fluidly connected to an outlet, with the turbine wheel rotatably mounted between the inlet and the outlet such that the respective flow of fluid passes through the inlet to the turbine wheel, driveably rotates the turbine wheel and passes from the turbine wheel to the outlet.

The inlet and outlet of each turbine may be fluidly connected to the turbine wheel by an inlet and outlet passage respectively.

The outlet passage may be substantially axial relative to the axis of rotation of the turbine wheel.

One or more of the turbine wheels may be a radial turbine wheel. In this respect, the inlet passage may be substantially radial relative to the axis of rotation of the turbine wheel.

One or more of the turbine wheels may be an axial turbine wheel. In this respect, the inlet passage may be substantially axial relative to the axis of rotation of the turbine wheel.

The outlet passages of the turbines may extend from the respective turbne wheels in substantially opposite axial directions.

The shaft may be rotatably mounted, to rotate about said axis, on a support structure.

The support structure may comprise a bearing housing and a bearing assembly provided between the shaft and the bearing housing so as to allow for rotation of the shaft relative to the bearing housing. The bearing assembly may comprse inner and outer races, mounted to the shaft and bearing housing respectively, radially separated by at least one bearing element.

The at least one bearing element may be any suitable type of bearing element, including a roller element bearing, a journal bearing, etc. The support structure may be disposed between the first and second turbine wheels.

The turbine generator may comprise a plurality of said support structures, axially spaced along the shaft. This is advantageous in that it allows the shaft to be supported at different axial positions along the shaft, thereby reducing wear on the shaft and/or the support structure.

Where the first turbine wheel is disposed between the second turbine wheel and the electrical generator, or the second turbine wheel is disposed between the first turbine wheel and the electrical generator, optionally a first said bearing assembly is provided between the first and second turbine wheels and a second said bearing assembly is provided between the electrical generator and the first or second turbine wheels respectively.

Where the electrical generator is disposed between the first and second turbine wheels, optionally the a first said bearing assembly is disposed between the first turbine wheel and the electrical generator and the second turbine wheel is disposed between the electrical generator and the second turbine wheel.

The turbine generator may further comprise a load which is coupled to the shaft so that rotation of the shaft drives the load to rotate.

The load may comprise a compressor wheel coupled to the shaft so that rotation of the shaft rotates the compressor wheel.

The compressor wheel may be so coupled to the shaft by being mounted directly on the shaft.

Alternatively, the compressor wheel may be so coupled to the shaft by a mechanical transmission. In this case, the compressor wheel may be mounted on a respective compressor shaft that is different to said shaft of the turbine generator.

The mechanical transmission may include any suitable mechanical gearing arrangement. In this respect, the compressor wheel may be driveably connected to a gear that is engageable with a complementary gear that is driveably connected to the shaft.

In this regard, the turbine generator may comprise a compressor comprising said compressor wheel rotatably mounted within a compressor housing for rotation about an axis, wherein the compressor housing defines an inlet fluidly connected to an outlet, with the compressor wheel rotatably mounted between the inlet and the outlet such that rotation of the compressor wheel draws air in through the inlet, compresses the air and forces the compressed air out through the outlet. The outlet of the compressor may be for connection to an intake manifold of an engine.

The inlet and outlet of the compressor may be fluidly connected to the compressor wheel by an inlet and outlet passage respectively.

The inlet passage of the compressor may be substantially axial relative to the axis of rotation of the compressor wheel.

The compressor may be a radial compressor. In this respect, the outlet passage of the compressor housing may be substantialy radial relative to the axis of rotation of the compressor wheel.

The compressor may be an axial compressor. In this respect, the outlet passage of the compressor housing may be substantially axial relative to the axis of rotation of the compressor wheel.

The compressor wheel may form part of a turbocharger.

The compressor wheel may be disposed between the electrical generator on one side and the first and second turbine wheels on the other side. Alternatively, the compressor wheel may be located at different position along the shaft, including between the first and second turbine wheels.

The stator may be arranged around the shaft. It will be appreciated that the stator may have any suitable arrangement with the rotor and/or the shaft such that rotation of the shaft rotates the rotor relative to the stator to generate electricity.

One or more of the turbine wheels may be provided with a fluid flow regulation mechanism that is operable to adjust the volume and/or rate of the flow of fluid that it is arranged to be rotatably driven by.

The fluid flow regulation mechanism may be operable to direct at least some of the flow of fluid so that it bypasses that turbine wheel. The fluid flow regulation mechanism may comprise a bypass valve. The bypass valve may be a wastegate valve.

One or more of the turbine wheels may be mounted within a respective turbine housing for rotation about a turbine axis, an annular inlet passageway extending radially inwards towards the turbine wheel, the annular inlet passageway being defined between a surface of a movable wall member and a facing wall of the turbine housing, the movable wall member being movable in the axial direction so as to vary the size of the annular inlet passageway. The movable wall member and the facing wall of the housing may be a nozzle ring and a shroud plate respectively, or vice-versa. The nozzle ring may be provided with a pluraUty of guide vanes, distributed circumferentially about the nozzle ring and wherein the shroud plate comprises an annular wall provided with a plurality of slots, each slot being arranged to receive a respective guide vane of the nozzle ring as the nozzle ring is moved axially relative to the shroud.

The turbine generator may form part of an engine system.

According to a second aspect of the present invention there is provided an engine system comprising: an internal combustion engine and a turbine generator according to the first aspect of the present invention.

Where one or more of the turbine wheels is arranged to be driven by a flow of exhaust gas from an internal combustion engine of an engine system, the engine system may comprise a turbine inlet path that fluidly connects an exhaust manifold of the internal combustion engine to the one or more turbine wheel such that, in use, at least a portion of exhaust gas from the internal combustion engine passes from the exhaust manifold, along the turbine inlet path, to the one or more turbine wheel and driveably rotates the one or more turbine wheel.

Where the one or more of the turbine wheels is provided with said fluid flow regulation mechanism comprising a bypass valve, that is operable to direct at least a portion of the flow of fluid so that it bypasses that turbine wheel, the engine system may comprise a bypass path that fluidly connects the turbine inlet path to an exhaust path such that flow passing from the turbine inlet path, along the bypass path to the exhaust path, bypasses the one or more turbine wheel and wherein the bypass valve fluidly connects the turbine inlet path and the bypass path and is arranged to selectively vary the portions of exhaust gas passing from the exhaust manifold to the one or more turbine wheel and to the bypass path respectively.

It will be appreciated that the bypass path may be fluidly connected to the turbine inlet path either directly or indirectly, for example via an inlet passage of a turbine. Similarly, it will be appreciated that the bypass valve may connect the turbine inlet path and the bypass path directly or indirectly. For example the bypass valve may connect the bypass path to the turbine inlet path via an inlet passage of a turbine.

The one or more turbine wheel may be fluidly connected to the exhaust path such that exhaust gas from the one or more turbine wheel passes to the exhaust path. The exhaust path may be fluidly connected tc the external atmosphere by an exhaust port.

The bypass valve may be continuously variable. An engine control unit may be operatively connected to the bypass valve, so as to control the bypass valve to selectively vary the portions of exhaust gas passing from the exhaust manifold to the one or more of the turbine wheels and to the bypass path respectively.

Where one or more of the turbine wheels is arranged to be driven by a flow of a working fluid of a waste heat recovery system of an engine system, the engine system may comprise a waste heat recovery system comprising a heat exchanger arranged to absorb heat from a heat source, a pump, a condenser and the one or more turbine wheel, fluidly connected within a heat exchanger circuit, the heat exchanger circuit being arranged such that, in use, working fluid within the heat exchanger circuit is heated by the heat exchanger, thereby causing the working fluid to expand and pass from the heat exchanger to the one or more turbine wheel such that the working fluid driveably rotates the one or more turbine wheel.

The heat source may be at least a portion of exhaust gas from the internal combustion engine, for example from the exhaust manifold. Alternatively, or additionally, the heat source may be a different source of heat in the engine system. Such a source of heat may include exhaust gas leaving one of the turbines, the internal combustion engine, a cooling jacket for the internal combustion engine, compressed gas leaving a compressor of the engine system, etc. The heat exchanger circuit may be a closed 1oop circuit. The working fluid may be a refrigerant. It will be appreciated that any suitable working fluid may be used. The waste heat recovery system may operate on the basis of the Rankine cycle.

Alternatively, or additionally, the waste heat recovery system may operate on the basis of any other suitable type of thermodynamic cycle, including the Carnot or Brayton thermodynamic cycles.

Where the turbine generator comprises said compressor, the compressor outlet may be fluidly connected to an intake manifold of the internal combustion engine such that the air compressed by the compressor is supplied to the engine intake manifold.

Embodments of the present invention will now be described, by way of example only, with reference to the accompanying figures, of which: Figure 1 is a schematic representation of an engine system including a turbine generator according to a first embodiment of the invention; Figure 2 is a schematic representation of an engine system including a turbine generator according to a second embodiment of the invention; and Figure 3 is a schematic representation of an engine system including a turbine generator according to a third embodiment of the invention; An engine system is schematically illustrated in Figure 1. The engine system comprises a turbine generator 100 according to a first embodiment of the invention, an internal combustion engine 10, and a waste heat recovery system 150.

The turbine generator 100 comprises a first turbine 122 and a second turbine 132 connected by a shaft 110.

The shaft 110 passes through, and is supported for rotation about an axis 99, by a support structure 170 comprising a bearing housing 41 and a bearing assembly 102 provided between the shaft and the bearing housing so as to allow for rotation of the shaft 110 relative to the bearing housing 41. The bearing assembly 102 comprises inner and outer races, mounted to the shaft 110 and bearing housing 41 respectively, radially separated by roller element bearings (not shown).

Lubricating fluid, in the form of oil, is fed to the bearing assembly 102 under pressure from an oil system of the engine system via an oil inlet, gallery and passages (not shown).

The first and second turbines 122, 132 comprise respective first and second turbine wheels 120, 130 that are each coupled to the shaft 110, such that the rotation of the turbine wheel 120, 130 rotates the shaft 110 about its axis 99, by being directly mounted on the shaft 110 to rotate with the shaft 110. In this respect, each turbine wheel 120, 130 is coaxial with the shaft and is arranged to rotate about the shaft axis 99.

Mounting the turbine wheels 120, 130 directly on the shaft 110 is advantageous in that, it may allow the combined rotatable system of shaft 110 and turbine wheels 120, 130 to be more easily balanced.

The first and second turbine wheels 120, 130 are mounted on opposite axial sides of the support structure 170.

Each turbine wheel 120, 130 is mounted within a respective housing 121, 131 between an intake 107, 108 and an outlet port 109, 111 defined by the housing 121, 131. The turbine wheel 120, 130 is fluidly connected to the intake 107, 108 by an inlet passage 81, 82. The turbine wheel 120, 130 is fluidly connected to the outlet port 109, 111 by an outlet passage 83, 84. As explained below, a separate flow of fluid is provided to each turbine wheel 120, 130 to rotatably drive the turbine wheel 120, 130. The first and second turbines 122, 132 are radial turbines. In this respect, each inlet passage 81, 82 extends generally in a radial direction, relative to the shaft axis 99. Each outlet passage 83, 84 extends generally in the axial direction 99.

The intake 107 of the first turbine 122 is fluidly connected to an exhaust manifold ba of the internal combustion engine 10 by a turbine inlet path 144 such that, in use, at least a portion of exhaust gas from the internal combustion engine 10 passes out of the exhaust manifold ba and along the turbine inlet path 144 to the intake 107. The exhaust gas flows through the intake 107, through the inlet passage 81 to the first turbine wheel 120 and driveably rotates the first turbine wheel 120 about the shaft axis 99, before passing through the outlet passage 83 and out through the outlet port 109.

The rotation of the turbine wheel 120 driveably rotates the shaft 110 about its axis 99.

The exhaust manifold ba of the internal combustion engine 10 is fluidly connected to the exhaust port 98 by an engine outlet path 116 which passes through a heat exchanger 153 (see below) to the exhaust path 11.

The outlet port 109 of the first turbine 122 is fluidly connected to an exhaust port 98, through which the exhaust gas exits to the atmosphere, via an outlet path 115, the engine outlet path 116, the heat exchanger 153 and the exhaust path 11.

In this respect, the outlet port 109 of the first turbine 122 is fluidly connected, by the outlet path 15, to the engine outlet path 116 at a point between the heat exchanger 153 and the exhaust manifold iDa. The heat exchanger 153 is fluidly connected to the exhaust port 98 by the exhaust path 11.

The heat exchanger 153 is arranged to extract heat from the exhaust gas passing through itto the exhaust port 98. The exhaust gas is from the outlet port 109 of the first turbine 122 and from the exhaust manifod 1 Oa of the internal combustion engine 10.

The first turbine 122 includes a bypass valve 104, in the form of a wastegate valve, that connects the inlet passage 81 to a bypass path 105. The bypass path 105 bypasses the turbine wheel 120 and passes from the bypass valve 104 to the outlet path 115.

In this respect, the inlet passage 81 is fluidly connected to an inlet of the bypass valve 104 and the bypass path 105 is fluidly connected to an outlet of the bypass valve 104.

The bypass path 105 passes from the outlet of the valve 104 to the outlet path 115.

The bypass valve 104 is selectively adjustable so as to vary the portions of exhaust gas passing from the exhaust manifold 1 Oa to the intake 107 of the first turbine 122 and to the bypass path 105 respectively.

In this respect, when the bypass valve 104 is in a first position, all of the exhaust gas leaving the exhaust manifold passes through the inlet passage 81 to the first turbine wheel 120. When the bypass valve 104 is in a second position, all of the exhaust gas leaving the exhaust manifold passes to the bypass path 105, thereby bypassing the first turbine wheel 120.

When the bypass valve 104 is between its first and second positions, respective portions of exhaust gas pass from the exhaust manifold ba to the first turbine wheel and to the bypass path 105. The bypass valve 104 is continuously variable between its first and second positions so as to continuously vary the portions of exhaust gas passing from the exhaust manifold 1 Oa to the first turbine wheel 12 and to the bypass path 105 respectively.

An engine control unit (not shown) is operatively connected to control the bypass valve 104, so as to control the position of the bypass valve 104.

Accordingly, the bypass valve 104 allows the flow capacity of the first turbine 122 to be varied whilst enabling control of the rotational speed of the turbine wheel 120 and therefore the shaft 110. For example, as the speed of the internal combustion engine increases, the bypass valve 104 may be moved from its first position to its second position, or to a position between its first and second positions, to allow all or some of the exhaust gas to bypass the first turbine wheel 120. This serves to increase the flow capacity of the first turbine 122 whilst lim ting the rotational speed of the shaft 110.

The waste heat recovery system 150 comprises a condenser 151, a pump 152, the heat exchanger 153 and the second turbine 132 fluidly connected within a closed loop circuit. A working fluid, in the form of a refrigerant, circulates in the closed loop circuit and driveably rotates the second turbine wheel 130.

The waste heat recovery system 150 is arranged to operate on the basis of a Rankine cycle. It will be appreciated that the second turbine 132 forms part of both the waste heat recovery system 150 and the turbine generator 100.

In more detail, the outlet port 111 of the second turbine 132 is fluidly connected to the condenser 151 by an outlet path 118. The condenser 151 is fluidly connected to the heat exchanger 153 by a first path 119. The pump 152 is provided in the first path 119 between the condenser 151 and the heat exchanger 153. The intake 108 of the second turbine 132 is fluidly connected to the heat exchanger 153 by an inlet path 123.

Accordingly, the waste heat recovery system 150 forms a closed loop system.

In use, the refrigerant enters the condenser 151 in gaseous form, is cooled and thereby condensed to liquid form. The refrigerant liquid is pumped, by the pump 152, from the condenser 151 to the heat exchanger 153. As the refrigerant liquid passes through the heat exchanger 153 it is heated by the heat absorbed from the exhaust gases passing through the heat exchanger 153 from the exhaust manifold ba of the engine 10 and from the outlet port 109 of the first turbine 122 (as described above).

The effect of this heating of the refrigerant is to cause the refrigerant to expand and vaporise to a vapour which is heated to a high temperature, for example between around 200°C and around 250°C. The refrigerant liquid then passes to the intake 108 of the second turbine 132 via the inlet path 123.

The refrigerant liquid passes from the intake 108 through the inlet passage 82 to the second turbine wheel 130, whereby the expanded refrigerant liquid driveably rotates the second turbine wheel 130, about the shaft axis 99, before exiting through the outlet port 111.

The rotation of the second turbine wheel 130 driveably rotates the shaft 110 about its axis 99.

Refrigerant exiting the second turbine housing 130, through the outlet port 111, returns to the condenser 151 via the outlet path 118 and the cycle begins again.

The waste heat recovery system 150 is selectively adjustable between an operating state in which working the refrigerant liquid flows around the system and a non- operating state in which refrigerant liquid does not flow around the system. In the non-operating state the refrigerant liquid does not drive the second turbine wheel 130. The pump 152 is turned on and off to adjust the waste heat recovery system 150 between its operating and non-operating states.

The turbine generator 100 also comprises an electrical generator 140. The electrical generator 140 comprises a rotor 141 and a stator 142. The rotor 141 is directly mounted to the shaft 110 to rotate with the shaft 110, about the axis 99.

The stator 142 is radially spaced from the rotor 141 and extends circumferentially around the shaft 110. The rotation of the shaft 11 0 causes the rotor 141 to rotate relative to the stator 142. This generates electrical energy by inducing an electromotive force, causing a current to flow through the stator 142. This electrical energy may be used for any desired purpose and may augment energy output by another power source.

The electrical generator 140 is disposed at one end of the shaft 110, the second turbine wheel 130 is disposed at the opposite end of the shaft 110 and the first turbine wheel 120 is disposed between the electrical generator 140 and the second turbine wheel 130. The first turbine wheel 120 is disposed between the support structure 170 and the electrical generator 140.

The turbine generator 100 allows two turbine wheels (or more-see below) 120, 130 that are driven by separate flows of fluid to driveably rotate a single shaft 110 and thereby drive a single electrical generator 140. This advantageously provides an arrangement which is less complex and more compact than would be the case if two separate electrical generators with associated turbine wheels and shafts were to be used to generate electricity using separate flows of fluid.

Referring to Fig. 2, there is shown an engine system including a turbine generator 200 according to a second embodiment of the invention. The turbine generator 200 of the second embodiment is identical to that of the first embodiment except in that the ordering of the first and second turbine wheels 120, 130 and the electrical generator 140 along the shaft 110 is different. The engine system of this embodiment is identical to that of the first embodiment except for the differences of the turbine generator 200.

In the following description, only the differences between the turbine generators 100, of the first and second embodiments will be described in detail. Corresponding features of the turbine generators 100, 200 of the first and second embodiments, and of the engine system, are given the same reference numerals.

In this second embodiment, the first turbine wheel 120 is disposed at one end of the shaft 110, the second turbine wheel 130 is disposed at the opposite end of the shaft and the electrical generator 140 is disposed between the first and second turbine wheels 120, 130. Advantageously, this allows for an arrangement in which the flows of the respective fluids in the outlet passages 83, 84 do not impede each other.

In this regard, the outlet passages 83, 84 of the turbines 122, 132 extend from the turbine wheels 120, 130 in substantially opposite axial directions. This is advantageous in that the flows of the respective fluids in the outlet passages 83, 84 do not impede each other.

In this embodiment there is a pair of said support structures 170 axially spaced along the shaft 110. The support structures 170 are disposed on opposite sides of the electrical generator 140, between each turbine wheel 120, 130 and the electrical generator 140.

The provision of more than one support structures 170 allows the shaft 110 to be supported at multiple axial positions along the shaft 110. This acts to better support the shaft 110 across its axial length, thereby reducing wear on the shaft 110 and/or the bearing assemblies of the support structures 170.

Referring to Fig. 3, there is shown an engine system including a turbine generator 300 according to a third embodiment of the invention. The turbine generator 300 of the third embodiment is identical to that of the first embodiment except in that it further comprises a compressor 301. The engine system of this embodiment is identical to that of the first embodiment except for the differences of the turbine generator 300. In the following description, only the differences between the turbine generators 100, 300 of the first and third embodiments will be described in detail. Corresponding features of the turbine generators 100, 300 of the frst and third embodiments, and of the engine system, are given the same reference numerals.

The compressor 301 comprises a compressor wheel 160 rotatably mounted within a compressor housing 161 between an intake 303 and an outlet port 304 defined by the housing 161. The compressor wheel 160 is fluidly connected to the intake 303 by an inlet passage 310. The compressor wheel 160 is fluidly connected to the outlet port 304 by an outlet passage 311.

The compressor 301 is a radial compressor. The inlet passage 310 extends generally in the axial direction 99 and the outlet passage 311 extends generally in the radial direction, relative to the shaft axis 99.

The compressor wheel 160 is disposed between the electrical generator 140 on one side and the first and second turbine wheels 120, 130 on the other side.

The compressor wheel 160 is directly mounted on the shaft 110 such that rotation of the shaft 110 driveably rotates the compressor wheel 160 about the shaft axis 99. The compressor 301 is arranged such that the rotation of the compressor wheel 160 draws air in through the intake 303, through the inlet passage 310 to the compressor wheel 160, which compresses the air and then passes the compressed air out through the outlet port 304 via the outlet passage 311.

The outlet port 304 is fluidly connected to an intake manifold lOb of the internal combustion engine 10 by an outlet path 305. The compressor 301 therefore supplies air to the intake lOb of the internal combustion engine 10 at pressures above atmospheric (boost pressures), thereby increasing engine power.

Accordingly, the rotation of the first and second turbine wheels 120, 130, driven by their respective fluid flows, acts to driveably rotate the compressor wheel 160 (as well as the rotor 141 of the electrical generator 140). In this regard, the first and second turbine wheels 120, 130 and the compressor wheel 160 form a turbocharger serving the internal combustion engine 10.

The turbine generator 300 allows two turbine wheels (or more-see below) 120, 130 that are driven by separate flows of fluid to driveably rotate a single shaft 110 and thereby drive a compressor wheel 160 and a single electrical generator 140. This advantageously provides an arrangement which is less complex and more compact than would be the case if two separate compressor wheels and/or electrical generators with associated turbine wheels and shafts were to be used to generate electricity using separate flows of fluid.

Numerous modifications and variations may be made to the exemplary design described above without departing from the scope of the invention as defined in the claims.

For example, in the described embodments the turbine generator 100, 200, 300 comprises two turbines 122, 132. It will be appreciated that the turbine generator may have more than two turbines where the turbine wheel of each turbine is arranged to be rotatably driven by a separate flow of fluid and is coupled to the shaft such that the rotation of the turbine wheel rotates the shaft about its axis.

In the described embodiment the turbine wheels 120, 130 of each turbine 122, 132 are coupled to the shaft by being mounted directly on the shaft. Alternatively, or additionally, one or more of the turbine wheels may be coupled to the shaft by a mechanical transmission. In this case, the one or more of the turbine wheels may be mounted on a respective turbine shaft that is different to the shaft of the turbine generator.

In the described embodiments, the first turbine wheel 120 is arranged to be driven by a flow of exhaust gas from the internal combustion engine 10 of the engine system and the second turbine wheel 130 is arranged to be driven by a flow of a working fluid of the waste heat recovery system 150 of the engine system. It will be appreciated that either or both of the first and second turbine wheels 120, 130 may be arranged to be driven by a flow of exhaust gas from the internal combustion engine 10 or by a flow of a working fluid of the waste heat recovery system 150 of the engine system.

Furthermore, where the turbine generator comprises more than two turbine wheels, each turbine wheel may be may be arranged to be driven by a flow of exhaust gas from the internal combustion engine 10 or by a flow of a working fluid of the waste heat recovery system 150 of the engine system.

In the described embodiments, the waste heat recovery system operates on the basis of the Rankine cycle. Alternatively, or additionally, the waste heat recovery system may operate on the basis of any other suitable type of thermodynamic cycle, including the Carnot or Brayton thermodynamic cycles.

The turbine wheels 120, 130, the electrcal generator 140 and the compressor wheel may have any ordering on the shaft 110.

In the described embodiments the turbine wheels 120, 130 are radial turbine wheels.

One or more of the turbine wheels 120, 130 may be axial turbine wheels. In this respect, the inlet of the turbine housing of the one or more of the turbine wheels may be substantially axial relative to the axis of rotation of the turbine wheel.

In the described embodiments the bearing assembly 102 comprises inner and outer races, mounted to the shaft 110 and bearing housing 41 respectively, radially separated by roller element bearings (not shown). It will be appreciated than any suitable type of bearing element may be used, including a roller element bearing, a journal bearing, etc. The support structure(s) may have different axial locations on the shaft 110.

In the described embodiment the compressor wheel 160 is coupled to the shaft 110 by being mounted directly on the shaft.

Alternatively, the compressor wheel may be coupled to the shaft by a mechanical transmission. In this case, the compressor wheel may be mounted on a shaft that is different to the shaft of the turbine generator.

In the described third embodiment, the turbine generator 300 comprises a load in the form of a compressor wheel 160 which is coupled to the shaft 110 so that rotation of the shaft 100 drives the load to rotate. Alternatively, or additionally, the load may comprise any other type of load which is coupled to the shaft so that rotation of the shaft drives the load to rotate.

In the described third embodiment, the compressor 301 is a radial compressor.

Alternatively, the compressor may be an axial compressor. In this respect, the outlet of the compressor housing may be substantially axial relative to the axis of rotation of the compressor wheel.

In the described third embodiment, the compressor wheel 160 is disposed between the electrical generator on one side and the first and second turbine wheels 120, 130 on the other side. Alternatively, the compressor wheel 160 may be located at a different position along the shaft, including between the first and second turbine wheels 120, 130.

In the described embodiment the stator 142 is arranged around the shaft 110. It will be appreciated that the stator 142 may have any suitable arrangement with the rotor 141 and/or the shaft 110 such that rotation of the shaft 110 rotates the rotor 141 relative to the stator 142 to generate electricity.

Where the first and second turbine whees are mounted on shafts different to that of the shaft 110, the electrical generator may comprise a plurality of rotors, each of which is attached to a different one of said shafts.

The first and/or second turbine wheels 120, 130 may be mounted within a respective turbine housing for rotation about a turbine axis, an annular inlet passageway extending radially inwards towards the turbine wheel 120, 130, the annular inlet passageway being defined between a surface of a movable wall member and a facing wall of the turbine housing, the movable wall member being movable in the axial direction so as to vary the size of the annular inlet passageway.

The movable wall member and the facing wall of the housing may be a nozzle ring and a shroud plate respectively, or vice-versa. The nozzle ring may be provided with a plurality of guide vanes, distributed circumferentially about the nozzle ring and wherein the shroud plate comprises an annular wall provided with a plurality of slots, each slot being arranged to receive a respective guide vane of the nozzle ring as the nozzle ring is moved axially relative to the shroud.

Claims

CLAIMS1. A turbine generator comprising a shaft mounted to rotate about an axis; two or more turbine wheels, wherein each of the two or more turbine wheels is arranged to be rotatably driven by a separate flow of fluid and is coupled to the shaft such that the rotation of the turbine wheel rotates the shaft about its axis; and an electrical generator comprising a rotor and a stator, the shaft being coupled to the rotor such that the rotation of the shaft rotates the rotor relative to the stator to generate electricity.
2. A turbine generator according to claim 1 wherein one or more of the turbine wheels is so coupled to the shaft by being mounted directly on the shaft.
3. A turbine generator according to any preceding claim wherein one or more of the turbine wheels is arranged to be driven by a flow of exhaust gas from an internal combustion engine of an engine system.
4. A turbine generator according to any preceding claim wherein one or more of the turbine wheels is arranged to be driven by a flow of a working fluid of a waste heat recovery system of an engine system.
5. A turbine generator according to claim 4 when dependent on clam 3 wherein the two or more turbine wheels comprise a first turbine wheel arranged to be driven by a flow of exhaust gas from an internal combustion engine and a second turbine wheel is arranged to be driven by a flow of a working fluid of a waste heat recovery system.
6. A turbine generator according to claim 5 wherein the first turbine wheel is disposed between the second turbine wheel and the electrical generator, or the second turbine wheel is disposed between the first turbine wheel and the electrical generator.
7. A turbine generator according to claim 5 wherein the electrical generator is disposed between the first and second turbine wheels.
8. A turbine generator according to any preceding claim wherein each turbine wheel is mounted within a respective turbine housing for rotation about an axis, the turbine housing defines an inlet fluidly connected to an outlet, with the turbine wheel rotatably mounted between the inlet and the outlet such that the respective flow of fluid passes through the inlet to the turbine wheel, driveably rotates the turbine wheel and passes from the turbine wheel to the outlet.
9. A turbine generator according to any preceding claim wherein the shaft is rotatably mounted, to rotate about said axis, on a support structure comprising a bearing housing and a bearing assembly provided between the shaft and the bearing housing so as to allow for rotation of the shaft relative to the bearing housing.
10. A turbine generator according to claim 9 wherein the bearing assembly comprises inner and outer races, mounted to the shaft and bearing housing respectively, radially separated by at least one bearing element.
11. A turbine generator according either of claims 9 or 10 when dependent on claim 5, or any a! claims 6 to 8 when dependent on claim 5, wherein the support structure is disposed between the first and second turbine wheels.
12. A turbine generator according any of claims 9 to 11 wherein the turbine generator comprises a plurality of said support structures, axially spaced along the shaft.
13. A turbine generator according to any preceding claim wherein the turbine generator comprises a load which is coupled to the shaft so that rotation of the shaft drives the load to rotate.
14. A turbine generator according to claim 13 wherein the load comprises a compressor wheel coupled to the shaft so that rotation of the shaft rotates the compressor wheel.
15. A turbine generator according to claim 14 wherein the compressor wheel is so coupled to the shaft by being mounted directly on the shaft.
16. A turbine generator according to either of claims 14 or 15 wherein the turbine generator comprises a compressor comprising said compressor wheel, the compressor wheel being rotatably mounted within a compressor housing for rotation about an axis, wherein the compressor housing defines an inlet fluidly connected to an outlet, with the compressor wheel rotatably mounted between the inlet and the outlet such that rotation of the compressor wheel draws air in through the inlet, compresses the air and forces the compressed ar out through the outlet.
7. A turbine generator according to any preceding claim wherein one or more of the turbine wheels is provided with a fluid flow regulation mechanism that is operable to adjust the volume and/or rate of the flow of fluid that t is arranged to be rotatably driven by.
18. A turbine generator according to claim 17 wherein the fluid flow regulation mechanism is operable to direct at least some of the flow of fluid so that it bypasses that turbine wheel.
19. A turbine generator according to claim 18 wherein the fluid flow regulation mechanism comprises a bypass valve.
20. An engine system comprising an internal combustion engine and a turbine generator according to any preceding claim.
21. An engine system according to claim 20 wherein the turbine generator is a turbine generator according to claim 3, or any of claims 4 to 19 when dependent on claim 3, wherein the engine system comprises a turbine inlet path that fluidly connects an exhaust manifold of the internal combustion engine to the one or more turbine wheel such that, in use, at least a portion of exhaust gas from the internal combustion engine passes from the exhaust manifold, along the turbine inlet path, to the one or more turbine wheel and driveably rotates the one or more turbine wheel.
22. An engine system according to claim 21 wherein the turbine generator is a turbine generator according to claim 19 and wherein the engine system comprises a bypass path that fluidly connects the turbine inlet path to an exhaust path such that flow passing from the turbine inlet path, along the bypass path to the exhaust path, bypasses the one or more turbine wheel and wherein the bypass valve fluidly connects the turbine inlet path and the bypass path and is arranged to selectively vary the portions of exhaust gas passing from the exhaust manifold to the one or more turbine wheel and to the bypass path respectively.
23. An engine system according to either of claims 21 or 22 and wherein the turbine generator is a turbine generator according to claim 4, or any of caims 5 to 19 when dependent on claim 4, wherein the engine system comprises a waste heat recovery system comprising a heat exchanger arranged to absorb heat from a heat source, a pump, a condenser and the one or more turbine wheel, fluidly connected within a heat exchanger circuit, the heat exchanger circuit being arranged such that, in use, working fluid within the heat exchanger circuit is heated by the heat exchanger, thereby causing the working fluid to expand and pass from the heat exchanger to the one or more turbine wheel such that the working fluid driveably rotates the one or more turbine wheel.
24. An engine system according to any of claims 21 to 23 wherein the turbine generator is a turbine generator according to claim 16, or any of claims 17 to 19 when dependent on claim 16, wherein the compressor outlet is fluidly connected to an intake manifold of the internal combustion engine such that the air compressed by the compressor is supplied to the engine intake manifold.
25. A turbine generator substantially as described herein with reference to the accompanying drawings.
26. An engine system substantially as described herein with reference to the accompanying drawings.