GB2503276A

GB2503276A - Magnetic coupling with fluid cooled barrier

Info

Publication number: GB2503276A
Application number: GB1211054.0A
Authority: GB
Inventors: John Michael Bywater
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2012-06-22
Filing date: 2012-06-22
Publication date: 2013-12-25
Anticipated expiration: 2032-06-22
Also published as: GB201211054D0; GB2503276B

Abstract

A turbine 52 comprises a turbine wheel 62 connected to a turbine shaft 63 provided with a magnetic coupling 73, 74 to an output shaft 54. A barrier 73 is provided between the halves of the magnetic coupling 73, 74. The barrier 73 has one or more conduits 69 which allow coolant into and from the barrier 73 to remove heat. This arrangement allows heat from the working fluid, or generated by windage, to be removed. The output shaft 54 may be replaced by generator stator windings, to allow electricity to be produced directly. The turbine 52 may be used in a waste heat recovery system for an internal combustion (e.g. diesel) engine. The waste heat recovery system may operate on an organic Rankine cycle (figure 1).

Description

Turbine The present invention relates to a turbine and to an engine assembly which includes a waste heat recovery system.

An engine assembly may comprise an internal combustion engine and may further comprise a turbocharger. A waste heat recovery system may be used to recover heat from the engine assembly and convert the recovered heat into usable power. The waste heat recovery system may be used to recover heat from engine exhaust gas and from an engine charge air cooler. Power derived from the waste heat recovery system may be used to generate electricity and/or to augment power output from the internal combustion engine.

A conventional waste heat recovery system uses a refrigerant fluid which is pumped around a closed loop. A heat exchanger is used to transfer heat from the engine (e.g. from exhaust gas) to the refrigerant, which is initially in liquid form. This heat causes the refrigerant liquid to vaporise. The refrigerant vapour passes to an expansion turbine and drives a turbine wheel of the expansion turbine to rotate. Power is derived from the rotation of the turbine wheel. The refrigerant vapour passes from the expansion turbine to a condenser which is configured to cool and condense the refrigerant so that it returns to liquid form. The refrigerant liquid is then passed to the heat exchanger, where the heat recovery cycle begins again.

The turbine wheel of the waste heat recovery system is mounted on a shaft which is held in a housing. In some cases the turbine wheel shaft may be provided with a gear or other power transfer apparatus which is used to augment the output of an internal combustion engine to which the waste heat recovery system is connected. In some cases the turbine wheel shaft may be indirectly connected to a second shaft, the second shaft being provided with the gear or other power transfer apparatus. The indirect connection may for example comprise a magnetic coupling between the turbine wheel shaft and the second shaft.

It is an object of the present invention to provide a turbine and an engine assembly which obviates or mitigates one or more disadvantages present in the prior art.

According to a first aspect of the invention there is provided a turbine comprising a turbine wheel connected to a turbine shaft provided with a first magnetic coupling and further comprising an output shaft provided with a second magnetic coupling, the first and second magnetic couplings being arranged such that rotation of the first magnetic coupling induces rotation of the second magnetic coupling, wherein a barrier is provided between the first and second magnetic couplings, the barrier being provided with one or more conduits which are configured to allow coolant to be delivered into the barrier and to allow the coolant to be removed from the barrier.

The conduits may comprise an inlet conduit and one or more conduits which are connected to the inlet conduit and extend within a wall of the barrier.

The conduits may comprise an outlet conduit and one or more conduits which are connected to the outlet conduit and extend within a wall of the barrier.

Each of the one or more conduits may be connected to a chamber which is located within the barrier.

The barrier may include a substantially cylindrical portion.

The substantially cylindrical portion may be closed by a wall and wherein the chamber is located within the wall.

The barrier may include an annular flange and the inlet conduit may extend around substantially half of the annular flange.

The outlet conduit may extend around substantially half of the annular flange, the inlet conduit and the outlet conduit each being provided in a different half of the annular flange.

The chamber may be located at an opposite end of the barrier from the inlet and outlet conduits.

The conduits may be connected to and arranged to receive fluid from a waste heat recovery system.

The barrier may be formed from plastic.

According to a second aspect of the invention there is provided an engine assembly comprising the turbine of the first aspect of the invention, and further comprising an internal combustion engine and a waste heat recovery system.

According to a third aspect of the invention there is provided a turbine comprising a turbine wheel connected to a turbine shaft provided with a magnetic coupling and further comprising a stator, the magnetic coupling and the stator being arranged such that rotation of the magnetic coupling generates electricity, wherein a barrier is provided between the first and second magnetic couplings, the barrier being provided with one or more conduits which are configured to allow coolant to be delivered into the barrier and to allow the coolant to be removed from the barrier.

According to a fourth aspect of the invention there is provided a method of transferring power from a turbine shaft to an output shaft, the method comprising using a first magnetic coupling provided on the turbine shaft to drive a second magnetic coupling provided on the output shaft, wherein a barrier is provided between the first and second magnetic couplings, and the method further comprises delivering coolant into one or more conduits provided in the barrier such that the coolant flows through the conduits in the barrier and receives heat from the barrier, then removing heated coolant from the barrier.

According to a fifth aspect of the invention there is provided a method of using a turbine shaft to generate electricity, the method comprising using driving the turbine shaft and a magnetic coupling provided on the turbine shaft to rotate relative to a stator, wherein a barrier is provided between the magnetic coupling and the stator, and the method further comprises delivering coolant into one or more conduits provided in the barrier such that the coolant flows through the conduits in the barrier and receives heat from the barrier, then removing heated coolant from the barrier.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Figure 1 schematically depicts an engine assembly according to an embodiment of the invention; Figure 2 is a cross-sectional view of a turbine according to an embodiment of the invention which forms part of the engine assembly; Figure 3 schematically depicts a barrier which forms part of the turbine shown in figure 2; and Figure 4 is a series of cross sectional views of the barrier shown in Figure 3.

An engine assembly is shown schematically in Figure 1. The engine assembly comprises an internal combustion engine 20, a turbocharger 3 and a waste heat recovery system 22. The internal combustion engine 20 may for example be a diesel engine.

A compressor 2 of the turbocharger 3 is arranged to draw in air (represented by a dashed arrow) and to push out air at high pressure (represented by a second dashed arrow). An outlet of the compressor 2 is connected to a charge air cooler 24 which is in turn connected to an intake manifold 26 of the internal combustion engine 20 (the passage of the compressed air is represented by dashed arrows). The charge air cooler 24 is a heat exchanger which is configured to transfer heat from the compressed air to ambient air, the ambient air being drawn through the charge air cooler by a mechanical fan 28. The charge air cooler 24 cools the compressed air, thereby increasing its density, before the compressed air is delivered to the intake manifold 26.

Exhaust gas from the internal combustion engine 20 passes out of an exhaust manifold 28. An outlet from the exhaust manifold 28 is connected to the turbine 1, and an outlet from the exhaust manifold is connected to a heat exchanger 32.

Exhaust gas which passes to the turbine 1 drives the turbine to rotate. Rotation of the turbine 1 causes rotation of the compressor 2 via the shaft 8. The compressor draws in air and compresses it for delivery to the intake manifold 26, as explained above. An outlet from the turbine 1 is connected to an after-treatment system 34 which applies an after-treatment to the exhaust gas. The after-treatment may for example be removal of particulates and/or nitrous oxide from the exhaust gas. The after-treatment system 34 is connected to an exhaust gas control valve 36. The exhaust gas control valve 36 has a first output connection which is directly connected to an exhaust 39 and has a second output connection which is connected to the exhaust via a heat exchanger 38. The heat exchanger 38 is hereafter referred to as the turbine exhaust gas boiler 38. The exhaust gas control valve 36 may be used to direct some or all of the exhaust gas through the turbine exhaust gas boiler 38. The turbine exhaust gas boiler 38 transfers heat from the exhaust gas to a refrigerant liquid of the waste heat recovery system, and may heat the refrigerant liquid to a temperature which is at or close to the boiling point of the refrigerant liquid.

As mentioned above, exhaust gas which does not pass to the turbine 1 passes to the heat exchanger 32. This heat exchanger 32 is hereafter referred to as the superheater 32. In the superheater 32 heat is transferred from the exhaust gas to the refrigerant fluid of the waste heat recovery system. This may increase the temperature of the refrigerant fluid to a temperature which is above the boiling point of the refrigerant.

The exhaust gas then passes from the superheater 32 into another heat exchanger 40.

This heat exchanger 40 is hereafter referred to as the engine exhaust gas boiler 40. In the engine exhaust gas boiler 40 heat is transferred from the exhaust gas to the refrigerant fluid of the waste heat recovery system. The refrigerant fluid will have a lower temperature in the engine exhaust gas boiler 40 than in the superheater 32. The refrigerant fluid may be heated in the engine exhaust gas boiler 40 to a temperature which is at or close to the boiling point of the refrigerant liquid.

The exhaust gas passes from the engine exhaust gas boiler 40 to a control valve 42, which is hereafter referred to as the exhaust gas recirculation valve 42. When the exhaust gas recirculation valve 42 is open, exhaust gas passes via the exhaust gas recirculation valve to the intake manifold 26 of the internal combustion engine 20.

When the exhaust gas recirculation valve 42 is closed, exhaust gas is not passed to the intake manifold 26 (the circulation of exhaust gas through the superheater 32 and engine exhaust gas boiler 40 is prevented).

Heat which is extracted from the exhaust gas via the superheater 32, the turbine exhaust gas boiler 38 and the engine exhaust gas boiler 40 is transferred to the refrigerant fluid. The waste heat recovery system 22 derives usable power from the refrigerant fluid. The waste heat recovery system 22 is a closed loop system, conduits of the closed loop being indicated by solid arrows in Figure 1. The refrigerant fluid of the closed loop system undergoes a phase transition from liquid to gaseous form at operating temperatures of the waste heat recovery system, as is explained further below.

The waste heat recovery system 22 is a Rankine cycle system. The closed loop of the waste heat recovery system 22 may be considered to begin at a condenser cooler 44.

Refrigerant fluid is cooled in the condenser cooler 44 by ambient air which is drawn through the condenser cooler by the mechanical fan 28. The refrigerant fluid, which enters the condenser cooler 44 in gaseous form is thereby condensed to liquid form.

The refrigerant liquid is pumped from the condenser cooler 44 by a pump 46 and passes to a recuperator 48. The function of the recuperator 48 is described further below. The refrigerant liquid then passes via a control valve 50 to either or both of the turbine exhaust gas boiler 38 or the engine exhaust gas boiler 40. Refrigerant liquid which passes to the turbine exhaust gas boiler 38 is heated by the exhaust gas in the exhaust gas boiler and is then passed to the engine exhaust gas boiler 40. The refrigerant fluid is heated further in the engine exhaust gas boiler 40 by exhaust gas.

Refrigerant liquid which is passed directly to the engine exhaust gas boiler 40 by the control valve 50 is also heated by exhaust gas. The refrigerant passes from the engine exhaust gas boiler 40 to the superheater 32 where it is heated further by exhaust gas.

The cumulative effect of this heating of the refrigerant is to cause the refrigerant to vaporise to a vapour which is heated to a high temperature, for example between around 20000 and around 25000. The heated refrigerant vapour is passed via a conduit to a turbine 52 of the waste heat recovery system 22. The turbine is an expansion turbine, meaning that the refrigerant vapour is expanded through the turbine. The vapour drives a turbine wheel of the turbine 52 to rotate, thereby allowing usable power to be derived (as explained further below).

The refrigerant vapour passes from an outlet of the turbine 52 to the recuperator 48.

The recuperator 48 is a form of heat exchanger, heat being transferred in the recuperator from the heated refrigerant vapour to refrigerant liquid which is being pumped by the pump 46 to the control valve 50. The temperature of the refrigerant vapour is thus reduced, although the refrigerant remains in a gaseous form. The refrigerant vapour passes from the recuperator 48 to the condenser cooler 44, where it is condensed to liquid form. The pump 46 then once again pumps the liquid refrigerant to the recuperator 48.

The turbine exhaust gas boiler 38, engine exhaust gas boiler 40, and superheater 32 are all examples of heat exchangers. In alternative configurations the waste heat recovery system may comprise one or more heat exchangers which may be provided at any suitable location(s) to recover heat generated by the internal combustion engine.

A shaft 54 extends from the turbine 52. The shaft 54 is connected to the turbine wheel of the turbine 52 and thus rotates with the turbine wheel. Usable power may be derived from the shaft 54 in a variety of different ways. For example, the shaft 54 may be connected to an output of the internal combustion engine 20, thereby augmenting the power output from the internal combustion engine. This transfer of power is indicated schematically in Figure 1 by hollow arrows. Mechanical gearing 56 may be provided between the shaft 54 and the output of the internal combustion engine 20.

The mechanical gearing 56 may be configured to reduce the speed of rotation of the shaft 54 to a speed which corresponds with the speed of rotation of the output of the internal combustion engine 20.

In alternative example, the shaft 54 may be connected to an electricity generator. For example the shaft 54 may be connected to a rotor of an electric generator (not shown) which generates electricity when the shaft 54 is driven to rotate by the turbine 52. In general, the shaft 54 may be connected to any suitable load, which may for example be electrical, mechanical or hydraulic.

Although a particular waste heat recovery system 22 is shown in Figure 1, embodiments of the invention may comprise other waste heat recovery systems (e.g. other waste heat recovery systems which use the Rankine cycle).

In an embodiment, high pressure air which is pushed out of the compressor 2 may be passed through a heat exchanger (not shown) which forms part of the closed loop of the waste heat recovery system 22. The heat exchanger may be used to transfer heat from the high pressure air (which has been heated by the action of the compressor 2) to the refrigerant. The heat may be combined with heat transferred to the refrigerant from the exhaust gas, the heated refrigerant being used to drive the turbine 52.

In an embodiment, the waste heat recovery system 22 may allow exhaust gas passing out of the turbocharger to pass into the atmosphere without recovering heat from it. In this embodiment heat may be recovered from exhaust gas which is being recirculated to the intake manifold 26. Heat may also be recovered from high pressure air which is pushed out of the compressor (in the manner explained above).

Figure 2 shows in cross-section the expansion turbine 52 of Figure 1. The expansion turbine 52 comprises a turbine wheel 62 fixed to a shaft 63 (hereafter referred to as the turbine shaft 63). The turbine shaft 63 is mounted such that it is free to rotate within a shaft housing 70. An inlet 64 is arranged to receive heated refrigerant from a heat exchanger (e.g., super heater 32 shown in Figure 1) and direct the refrigerant to an annular chamber 65. Vanes 66 are located between the annular chamber 65 and the turbine wheel 62. A refrigerant outlet 67 is located on an opposite side of the turbine wheel 62 from the vanes 66. The refrigerant outlet 67 may be connected to a recuperator 48 (shown in Figure 1). In use, heated refrigerant passes via the inlet 64 to the annular chamber 65 and is directed towards the turbine wheel 62 by the vanes 66.

The passage of the refrigerant over the turbine wheel 62 causes the turbine wheel to rotate thereby causing the turbine shaft 63 to rotate. The turbine 52 is an axial turbine, i.e., the flow of refrigerant across the turbine wheel 62 is in a substantially axial direction.

A bearing 71 is provided between the turbine shaft 63 and the shaft housing 70, the bearing being arranged to allow the shaft to rotate freely within the shaft housing. The bearing may have any suitable construction. A lubricant fluid is provided to the bearing via a lubricant inlet 78. A labyrinth seal 68 is located between the turbine wheel 62 and the bearing 71. The labyrinth seal may, for example, comprise a helical groove formed in a component which extends around a collar of the turbine wheel 62. The component has a clearance from the collar of the turbine wheel 62, thereby allowing the turbine wheel 62 to rotate freely within the component. The clearance is sufficiently small that the passage of fluid between the component and the turbine wheel collar is restricted.

A barrier 73 is provided at an opposite end of the shaft housing 70 from the turbine wheel 62. The barrier 73 in this embodiment includes a substantially cylindrical portion.

The barrier 73 is closed at one end by a wall and includes a flange 76 at an opposite end. The barrier 73 may be said to resemble a top hat. In alternative embodiments the barrier may have any suitable shape.

The flange 76 extends outwardly from an open end of the barrier 73 and allows the barrier to be securely connected to the shaft housing 70. An 0-ring 77 held in a support which is connected to the shaft housing 70 presses against an internal surface of the barrier 73. The 0-ring 77 provides a seal which isolates the interior of the barrier 73 from the exterior of the barrier.

Conduits (labelled generally as 69) are provided within the barrier 73, the conduits being configured to allow coolant to be delivered into the barrier and to allow the coolant to be removed from the barrier. The conduits 69 may be connected to conduits which pass through the shaft housing 70, and which may be used to deliver and remove the coolant from the barrier 73. One or more seals (not shown) may be provided between the conduits 69 in the barrier 73 and the conduits 85 in the shaft housing 70.

The lubricant which is used to lubricate the bearing 71 may flow into an interior space which is sealed at one end by the barrier 73, has a generally cylindrical wall formed by the shaft housing 70 and has the labyrinth seal 68 at an opposite end. The 0-ring 77 prevents the refrigerant from passing to the exterior of the barrier 73. The labyrinth seal restricts the passage of fluid between the interior space and the turbine wheel 62.

However, because some fluid will pass through the labyrinth seal the interior space may be said to be connected to the turbine wheel 62 and hence to the refrigerant loop of the waste heat recovery system 22 (see Figure 1). The refrigerant loop of the waste heat recovery system may be at a high pressure, for example in the range 20-30 bar.

Some pressure may be communicated through the labyrinth seal to the interior space around the bearing 71 (the pressure may depend upon the effectiveness of the labyrinth seal and expansion of the refrigerant by the turbine). The pressure in the interior space may for example be in the range 2-6 bar.

An opposite end of the turbine shaft 63 from the turbine wheel 62 has an increased diameter. This end of the turbine shaft 63 is formed from magnetic material, and is referred to hereafter as the inner magnetic coupling 72. The inner magnetic coupling 72 may for example comprise a plurality of magnetic poles which are arranged as an alternating series. The magnetic poles may be distributed around a circumference which is centered on an axis of rotation of the turbine shaft 63. A recess 80 extends axially into the inner magnetic coupling 72. The magnetic poles of the inner magnetic coupling 72 are arranged such that when the turbine shaft 63 rotates a rotating magnetic field rotates about the axis of rotation of the turbine shaft 63.

The turbine 52 further comprises a shaft 54 which is coaxial with the turbine shaft 63.

This shaft is referred to hereafter as the output shaft 54. The output shaft 54 is held in a shaft housing 75, a bearing 76 bearing provided between the shaft and the shaft housing to allow the shaft to rotate freely within the housing. The shaft housing 75 of the output shaft 54 is secured to the shaft housing 70 of the turbine shaft 63 using bolts which extend through flanges of the housings.

An end of the output shaft 54 which is furthest from the turbine wheel 62 may be provided with a pinion gear 79 or some other apparatus which may be used to couple power from the turbine 52. An end of the output shaft 54 which is closest to the turbine wheel 62 has an increased diameter and is provided with an axial recess 81 which is sufficiently wide to accommodate pad of the barrier 73. The output shaft 54 thus extends around (and may be considered to encircle) part of the barrier 73. This end of the output shaft 54 is formed from magnetic material, and may be referred to hereafter as the outer magnetic coupling 74. The outer magnetic coupling 74 comprises a plurality of magnetic poles which are arranged as an alternating series. The magnetic poles may be distributed around a circumference which is centered on an axis of rotation of the output shaft 54. The poles of the outer magnetic coupling 74 are arranged such that when the inner magnetic coupling 72 rotates the outer magnetic coupling is induced to rotate. Thus, rotation of the turbine shaft 63 induces rotation of the output shaft 54, thereby allowing power generated via the turbine wheel 62 to be coupled out of the turbine 52.

A space 82 is provided between the outer magnetic coupling 74 and the shaft housing 75. This space 82 may be connected to the atmosphere via suitable conduits (not shown). The pressure in the space 82 may thus for example be around 1 bar. The barrier 73 isolates the pressurised lubricant which is on an interior side of the barrier from the space 82 on the exterior side of the barrier, thereby preventing the leakage of lubricant into the space 82.

The barrier 73 is formed from a material which is magnetically permeable in order to allow coupling between the inner magnetic coupling 72 and the outer magnetic coupling 74 to occur. The barrier 73 may for example be formed from plastic. The radial distance between the inner magnetic coupling 72 and the outer magnetic coupling 74 affects the amount of torque that can be transmitted between them (the amount of torque being greater when the radial distance is small and being smaller when the radial distance is large). For this reason the inner magnetic coupling 72 may be located relatively close to the barrier 73, and similarly the outer magnetic coupling 74 may be located relatively close to the barrier. The separation between the inner magnetic coupling 72 and the barrier 73 may for example be of the order of 1-2 mm.

Similarly, the separation between the outer magnetic coupling 74 and the barrier 73 may for example be of the order of 1-2 mm. The turbine shaft 63 and output shaft 54, and associated magnetic couplings 72, 74, may rotate at high speeds, for example of the order of 10,000s revolutions per minute. This may cause viscous friction in fluids on either side of the barrier 73 (sometimes referred to as windage), which may cause heating of the barrier. The separation between the magnetic couplings 72, 74 and the barrier may be selected to reduce windage. Nevertheless, some windage will remain and thus some heating of the barrier 73 will occur. If the barrier 73 were to become too hot then it would melt, thereby causing failure of the isolation between the pressurised lubricant and the space 82.

Figure 3 shows schematically in cross-section the barrier 73 viewed from one side.

The barrier 73 is provided with conduits 69 which form a cooling system. The barrier 73 has a generally cylindrical shape and includes a flange 76 at its lowermost end. A coolant inlet conduit 82 of the cooling system is provided on one side of the flange, and a coolant outlet conduit 83 of the cooling system is provided on an opposite side of the flange. A first set of conduits 90 extend from the coolant inlet conduit 82 to a chamber which is located within the barrier 73. A second set of conduits 91 extend from the chamber 95 to the coolant outlet conduit 83.

Figure 4A shows the barrier 73 in cross-section viewed from above at plane AA, Figure 4B shows the barrier in cross-section viewed from above at plane RB, and Figure 4C shows the barrier in cross-section viewed from above at plane CC. Each of planes AA, BR and CC are indicated in Figure 3.

Referring to Figure 4A in combination with Figure 3, the coolant inlet conduit 82 is provided on one side of the flange 76 and is arranged to allow coolant to flow into the barrier 73. The coolant outlet conduit 83 is provided on an opposite side of the barrier 73 and is arrange to allow coolant to flow out of the barrier. The coolant inlet conduit 82 includes a substantially semi-circular portion 84 which extends around substantially half of the flange 76. The coolant outlet conduit 83 similarly includes a semi-circular portion 86 which extends around substantially half of the flange 76. The semi-circular portions 84, 86 stop short of each other. That is, barriers 87 are present between them. The barriers 87 prevent coolant from flowing directly from the coolant inlet conduit 82 to the coolant outlet conduit 83.

Referring to Figure 4B in combination with Figure 3, the first and second sets of conduits 90, 91 extend from the base of the barrier 73 towards the top of the barrier (the base of the barrier may be considered to be the end of the barrier at which the flange 76 is provided, and the top of the barrier may be considered to be an opposite end of the barrier). The first set of conduits 90 is in communication with the semi-circular portion 84 of the inlet conduit 82. These conduits 90 are thus considered to be on an inlet side of the cooling system of the barrier 73. The second set of conduits 91 is in communication with the semi-circular portion 86 of the outlet conduit 83. These conduits 91 are thus considered to be on an outlet side of the cooling system of the barrier 73.

Referring to Figure 4C in combination with Figure 3, the top of the barrier 73 comprises upper and lower surfaces 93, 94 which are spaced apart from one another and thereby define a chamber 95. The chamber 95 is generally disk-shaped, although a pillar 96 is located at the centre of the chamber 95. The first and second sets of conduits 90, 91 are in fluid communication with the chamber 95.

In use, coolant liquid is introduced into the inlet conduit 82 (e.g., from a supply of coolant fluid which is not shown). The coolant flows into the semi-circular portion 84 of the inlet conduit 82 and then into the first set of conduits 90. The coolant flows through the first set of conduits 90 into the chamber 95. In the chamber 95 coolant which has travelled through different conduits 90 mixes together.

Having crossed the chamber 95, the coolant flows out of the second set of conduits 91 and into the semi-circular portion 86 of the outlet conduit 83. The coolant then flows from the outlet conduit 83. The coolant absorbs heat from the barrier 73 and carries that heat out of the outlet conduit. The coolant may, for example, pass to a heat exchanger (not shown) which removes heat from the coolant. The heat exchanger may be a condenser. Once heat has been removed from the coolant, the coolant may be reintroduced at the coolant inlet conduit 82.

The passage of the coolant through the barrier 73 transfers heat from the barrier, thereby cooling the barrier. The coolant may thus prevent the barrier 73 from overheating, thereby preventing damage being caused to the barrier by overheating.

This is advantageous because damage to the barrier 73 could cause failure of the turbine 52, for example with the barrier melting onto one of the magnetic couplings 72, 74 and preventing them from rotating.

In an embodiment, a heat exchanger which is used to remove heat from the coolant may transfer at least some of that heat to refrigerant used by the waste heat recovery system 22 (see Figure 1).

Although the barrier 73 has a particular arrangement of coolant conduits, any suitable arrangement of conduits may be used to deliver coolant to the barrier and to remove heated coolant from the barrier. For example, two of the conduits 90 on the inlet side of the cooling system may be connected together to form a conduit which is elongate in cross-section. For example, three or more of the conduits 90 on the inlet side of the cooling system may be connected together to form a conduit which has a longer elongate cross-section. Similarly, two or more of the conduits 91 on the outlet side of the cooling system may be connected together to form a conduit which has an elongate cross-section. In an embodiment, a single conduit may be used to cool the barrier 73.

In an alternative arrangement, instead of conduits extending directly between the flange 76 and the chamber 95, one or more conduits may extend indirectly between the flange and the chamber. For example, one or more conduits may double-back on themselves one or more times (e.g. forming one or more serpentine shapes). For example, one or more conduits may be curved.

The coolant conduits 90, 91 and chamber 95 provide a considerable degree of cooling at the point where the conduits meet the chamber. This may be advantageous because the windage heating may be particularly pronounced at this location. Other conduit arrangements may also be arranged to provide a considerable degree of cooling at the point where the conduits meet the chamber.

The barrier 73 may be formed as a single component, for example using injection moulding. Alternatively, the barrier 73 may be formed as a plurality of pieces which are connected together One or more of the pieces may for example be formed using injection moulding. One or more pieces may for example be formed using extrusion.

Embodiments in which the conduits 90, 91 are elongate in cross-section may be easier to fabricate than embodiments in the which the conduits are cylindrical in cross-section.

A substantially cylindrical portion of the barrier 73 may for example be formed using injection moulding.

The coolant may be any suitable fluid. The coolant may for example be a refrigerant which provides evaporative cooling in the barrier 73. A refrigerant which undergoes a phase transition from liquid to vapour at the operating temperature of the barrier 73 maybe used. The refrigerant may for example be R245Fa refrigerant, available from Honeywell of New Jersey, USA. Any other suitable refrigerant may be used. The coolant may be same as the coolant which is used by the waste heat recovery system 22 (see Figure 1). The coolant may be supplied from, and reintroduced into, the loop of the waste heat recovery system. Thus, conduits of the cooling system may be connected to the loop of the waste heat recovery system.

The coolant may be the same fluid that is used to lubricate the bearing 71 of the turbine shaft and within which the inner magnetic coupling 72 rotates. The fluid used to lubricate the bearing 71 may be coolant which is used in the loop of the waste heat recovery system.

In an embodiment in which the outer magnetic coupling 74 rotates in a fluid which may be used as a coolant, the coolant used to cool the barrier 73 may be that fluid The barrier may be formed from plastic. The barrier may be formed using injection moulding, extrusion or any other suitable technique. RF welding may be used to assemble component pieces of the barrier together.

In the illustrated embodiment a pillar 96 is provided within the chamber 95. The pillar may help to keep opposite walls of the chamber 95 separated from one another.

However, it is not essential that a pillar be provided in the chamber.

Although the illustrated embodiment of the barrier 73 includes an annular flange 76, it is not essential that the barrier have an annular flange. The barrier may be provided with a flange having any suitable shape. It is not essential that conduits extend through a flange of the barrier. The barrier may have no flange. Brackets or any other suitable attachment apparatus may be used to attach the barrier to the shaft housing 70.

The barrier 73 may have any suitable shape. Although the top of the barrier is shown as being flat, the top of the barrier might not be flat. The top of the barrier may for

example be curved.

The illustrated sets of conduits 90, 91 in the barrier are arranged to cause coolant to flow in an axial direction along the substantially cylindrical portion of the barrier 73.

Other configurations of conduits may be arranged to cause coolant to flow in a substantially axial direction along the substantially cylindrical portion of the barrier.

In the illustrated embodiment the inner magnetic coupling 72 is arranged to drive the outer magnetic coupling 74. However, in an alternative embodiment, the outer magnetic coupling may be replaced with a stator. Where this is the case, electricity will be generated by the rotation of the inner magnetic coupling 72 relative to the stator.

Although in the illustrated embodiment the magnetic coupling driven by the turbine wheel 62 is an inner magnetic coupling, in an embodiment the magnetic coupling driven by the turbine wheel may be an outer magnetic coupling (the inner magnetic coupling may be connected to an output shaft).

Although the expansion turbine shown in Figure 2 has an axial inflow, the expansion turbine may alternatively have a radial inflow. A mechanism to adjust the flow of vapour to the expansion turbine may be provided, the mechanism acting to broaden the operating map width of the expansion turbine. The mechanism may for example comprise a variable nozzle, or may comprise a plurality of inlets with different diameters which may be selected to provide flows of vapour.

The waste heat recovery system 22 may for example be a sub-critical Rankine cycle system, or may for example be a super-critical Rankine cycle system.

The waste heat recovery system 22 may be an organic Rankine cycle system, i.e. the refrigerant fluid used by the waste heat recovery system may be an organic fluid (e.g. having a high molecular mass). The organic fluid may have a liquid-vapour phase change, or boiling point, which occurs at a lower temperature than the water-steam phase change.

The engine assembly may be used to power a truck or some other vehicle. The truck may for example be a heavy duty diesel truck (e.g. class 7 or class 8 under the US Federal Highway Administration classification). In applications such as this the turbine 52 may be connected via gearing 56 to an output of the internal combustion engine 20 (which may for example be a diesel engine).

Alternatively, the engine assembly may be used in a static environment, for example to generate electricity. Where this is the case, the power derived from the waste heat recovery system may be converted to electricity which supplements the output from the engine.

Claims

CLAIMS: 1. A turbine comprising a turbine wheel connected to a turbine shaft provided with a first magnetic coupling and further comprising an output shaft provided with a second magnetic coupling, the first and second magnetic couplings being arranged such that rotation of the first magnetic coupling induces rotation of the second magnetic coupling, wherein a barrier is provided between the first and second magnetic couplings, the barrier being provided with one or more conduits which are configured to allow coolant to be delivered into the barrier and to allow the coolant to be removed from the barrier.
2. The turbine of claim 1, wherein the conduits comprise an inlet conduit and one or more conduits which are connected to the inlet conduit and extend within a wall of the barrier.
3. The turbine of claim 1 or claim 2, wherein the conduits comprise an outlet conduit and one or more conduits which are connected to the outlet conduit and extend within a wall of the barrier.
4. The turbine of claim 2 and claim 3, wherein each of the one or more conduits is connected to a chamber which is located within the barrier.
5. The turbine of any preceding claim, wherein the barrier includes a substantially cylindrical portion.
6. The turbine of claim 4 and claim 5, wherein the substantially cylindrical portion is closed by a wall and wherein the chamber is located within the wall.
7. The turbine of claim 2 or any claim which depends therefrom, wherein the barrier includes an annular flange and wherein the inlet conduit extends around substantially half of the annular flange.
8. The turbine of claim 7, wherein the outlet conduit extends around substantially half of the annular flange, the inlet conduit and the outlet conduit each being provided in a different half of the annular flange.
9. The turbine of claim 4 or any claim which depends therefrom, wherein the chamber is located at an opposite end of the barrier from the inlet and outlet conduits.
10. The turbine of any preceding claim, wherein the conduits are connected to and arranged to receive fluid from a waste heat recovery system.
11. The turbine of any preceding claim, wherein the barrier is formed from plastic.
12. An engine assembly comprising the turbine of claim 1, and further comprising an internal combustion engine and a waste heat recovery system.
13. A turbine comprising a turbine wheel connected to a turbine shaft provided with a magnetic coupling and further comprising a stator, the magnetic coupling and the stator being arranged such that rotation of the magnetic coupling generates electricity, wherein a barrier is provided between the first and second magnetic couplings, the barrier being provided with one or more conduits which are configured to allow coolant to be delivered into the barrier and to allow the coolant to be removed from the barrier.
14. A method of transferring power from a turbine shaft to an output shaft, the method comprising: using a first magnetic coupling provided on the turbine shaft to drive a second magnetic coupling provided on the output shaft, wherein a barrier is provided between the first and second magnetic couplings, and the method further comprises delivering coolant into one or more conduits provided in the barrier such that the coolant flows through the conduits in the barrier and receives heat from the barrier, then removing heated coolant from the barrier.
15. A method of using a turbine shaft to generate electricity, the method comprising: using driving the turbine shaft and a magnetic coupling provided on the turbine shaft to rotate relative to a stator, wherein a barrier is provided between the magnetic coupling and the stator, and the method further comprises delivering coolant into one or more conduits provided in the barrier such that the coolant flows through the one or more conduits in the barrier and receives heat from the barrier, then removing heated coolant from the barrier.