Turbocharger and fuel cell system

Abstract

A turbocharger (fig.1,2), suitable for a fuel cell system, has a compressor wheel (fig.1,10) rotationally connected to a turbine wheel (fig.1,20), such as a radial or mixed-flow turbine, via a shaft (

Description

Fuel cells are alternative sources of power to internal combustion engines for vehicular propulsion. Fuel cells generate electricity by combining a fuel with an oxidant. The electricity generated by such fuel cells can be used for any electrical purpose, for example to power homes and electronic devices, as well as being used to power machinery and vehicles via the use of electric motors. Typically, the fuel employed in such fuel cells is Hydrogen (H2), however alkanes such as Methane (CH4) or alcohols such as Methanol (CH3OH) can be used instead. Likewise, Oxygen (02) is typically used as the oxidant, however any oxygen-containing gas mixture, such as atmospheric air (a mixture of Nitrogen N2 and Oxygen 02) may be used as an alternative. Proton-exchange membrane (PEM) fuel cells, also called polymer electrolyte membrane fuel cells, are a type of fuel cell that is often used for vehicular propulsion. PEM fuel cells comprise an anode and a cathode separated by a polymer electrolyte membrane in a layered structure. The anode and cathode are connected to one another via an electrical load. During use, Hydrogen (the fuel) is delivered to the anode side of the cell and atmospheric air (the oxidant) is delivered to the cathode side of the cell. The anode is provided with a platinum catalyst which acts to reduce the Hydrogen so that it is positively charged, by “stripping” it of its single electron. The Hydrogen ions and electrons formed at the catalyst are able to react with the Oxygen component of the air to which the cathode is exposed, and are thereby attracted to the Oxygen by their electrical charges. In order to reach the Oxygen, the Hydrogen ions take a direct path from the anode side to the cathode side of the cell by permeating through the polymer electrolyte membrane. However, the polymer electrolyte membrane is configured to exclude the passage of electrons therethrough. Unable to pass through the membrane, the electrons pass from the anode to the cathode via the attached electrical load, thereby producing electrical power that can be extracted for useful purposes. Once the Hydrogen ions and electrons reach the cathode, both react with the Oxygen component of the air to which the cathode is exposed, thus creating water (H2O). In PEM fuel cells of the kind described above, the Hydrogen is typically supplied from a high pressure storage tank and therefore further compression of the Hydrogen before delivery to the anode side of the cell is unnecessary. However, the pressure of the atmospheric air supplied to the cathode side of the cell may be increased by using a compressor. By increasing the pressure of the intake air, the mass of Oxygen within the cathode chamber can be increased. With more Oxygen available at the cathode, a greater number of combination reactions on the cathode side can be supported, leading to higher electrical potential across the cell and the production of more power. It is known to provide fuel cell systems with turbochargers in order to compress the intake air supplied to the fuel cell cathode. Such turbochargers comprise a compressor connected to the intake side of the fuel cell cathode, and a turbine connected to the exhaust side of the fuel cell anode. The compressor and turbine are mounted to a common shaft, such that work extracted by the turbine from the anode exhaust can be used to drive the compressor. However, the available power in the exhaust gas leaving the anode is usually lower than the power required by the compressor to compress the intake air. In order to address the imbalance between the turbine and the compressor wheels, turbochargers in fuel cell systems typically comprise a motor that is able to increase the power available to the compressor by using electro-magnetic forces to rotate the shaft. Moreover, due to the different power requirements of the compressor and the turbine, as a result, the required size of compressor wheel is normally larger than that of the turbine wheel. The requirement to use a compressor wheel results in a large axial thrust load along the shaft acting towards the compressor, due to the pressure applied by the compressed intake air on the back face of the compressor wheel. To react such axial loading, fuel cell turbochargers typically comprise one or more thrust bearings. However, bearing systems that use oil are not compatible with fuel cell systems due to the risk of contamination of the intake air, which can damage the fuel cell. Therefore, turbochargers within fuel cell systems typically employ gas-lubricated bearing systems that use non-contaminating working fluids, such as air. However, gas-lubricated bearing systems are unable to support high axial thrust loads. Reducing the size of the compressor wheel relative to the turbine wheel reduces the axial thrust load. However, this requires the motor to rotate the compressor faster in order to produce the same pressure ratio and thereby provide adequate compression for the fuel cell. Of course, increasing the rotational speed of the compressor also increases the rotational speed of the turbine wheel, as the two are rotationally fixed in relation to one another. Turbine wheel efficiency varies as a function of the dimensionless ratio of the blade tip speed U to the velocity C of the incoming working fluid. In particular, C is the velocity the expanding gas would achieve if it was expanded isentropically in an ideal nozzle / turbine over the same pressure ratio (i.e. Piniet / Poutiet). When the value of U / C is too low or high, the efficiency of the turbine decreases. Therefore, whilst the higher rotational speed for the compressor can be achieved by providing more electrical power to the motor, rotating the shaft too quickly increases U / C and thereby reduces the efficiency of the turbine wheel, meaning less work is extracted from the fuel cell exhaust. This increases the amount of electricity that is required to maintain the compressor at the required rotational speed. In light of the above, it is an object of the invention to provide a turbocharger for a fuel cell system that exhibits reduced axial thrust loading whilst maintaining optimum turbocharging efficiency. It is a further object of the invention to obviate or mitigate one or more disadvantages of the prior art, whether identified herein or elsewhere. Summary According to a first aspect of the invention there is provided a turbocharger for a fuel cell system, the turbocharger comprising: a shaft supported for rotation about a central axis (A); a compressor wheel rotationally connected to the shaft; a turbine wheel rotationally connected to the compressor via the shaft; a motor electro-magnetically connected to the shaft for rotationally driving the shaft; and a gas-lubricated thrust bearing arranged to react a resultant axial load applied to the shaft by the compressor wheel and the turbine wheel; wherein the turbine wheel comprises a blade defining a leading edge, the leading edge defining a blade incline angle (cp) being inclined relative to a radial direction (r) originating from the central axis (A) in a positive angular direction relative to the direction of rotation (w) of the turbine during use. By “positive angular direction” it is meant the same direction as the direction of rotation of the turbine wheel during use. This causes the pressure surface of the blade to be inclined generally away from the incoming fluid stream. Therefore, such arrangements may be referred to as a “backswept” arrangement of the leading edge of the blade (in contrast to a “forward-swept” arrangement, in which the pressure surface would be inclined towards the incoming fluid stream). Because the leading edge of the blade is inclined in the positive angular direction (i.e. is backswept), the angle of incidence between the oncoming working fluid and the blade at high rotational speeds (i.e. high U / Q is reduced. This increases the rotational speed at which peak turbine efficiency occurs. Accordingly, the compressor wheel can be reduced in diameter and driven at higher speeds by the motor to meet the required degree of compression for the fuel and to match the most efficient operating speeds of the turbine wheel. With the size of the compressor wheel reduced in relation to the turbine wheel, the net thrust force applied on the shaft by the oppositely acting turbine and compressor wheels is also reduced. Because the net thrust load is reduced, the thrust applied to the shaft can be reacted by the gas-lubricated thrust bearings, which do not risk contamination of the fuel cell. Therefore, in summary, by using a backswept turbine wheel in a fuel cell turbocharger system, adequate compression of the fuel cell intake air can be provided whilst limiting axial thrust forces and maintaining optimum efficiency. The turbine wheel may comprise a hub. The blade may define a tip extending between the leading edge and the trailing edge. All points on the leading edge may define a local blade incline angle relative to the radial direction. All local blade incline angles on the leading edge may be inclined in the positive angular direction. Because all local blade incline angles are inclined in the positive direction, the turbine wheel is better suited for use at higher rotational speeds. All local blade incline angles on the leading edge may be inclined relative to the radial direction by around 10 ° to around 80 °, or more preferably by around 25 ° to around 65 °, or more preferably around 40 ° to around 50 °, or most preferably may be around 45 Increasing the blade incline angles increases the rotational speed (i.e. U / C) at which peak efficiency occurs by decreasing the relative angle of incidence between the oncoming fluid and the rotating blade. It has been found that a minimum blade incline angle of 10° in the positive direction provides a sufficient increase in the rotational speed at which peak turbine efficiency occurs ((p^max) to enable the use of a compressor wheel of a significant enough reduction in size to reduce the thrust forces produced on the shaft. A maximum blade incline angle of 80 0 in the positive direction ensures that the rotational speed at which peak turbine efficiency occurs is not sufficiently large so as to require the compressor wheel to be sized too small or to be operated at unsafe or inefficient rotational speeds in order to provide adequate compression. However, it has been found that the range of around 25 0 to around 65 °, provides a good trade off between the two factors above, and that the range of around 40 0 to around 50 or more preferably 45 °, provides an optimum balance between said factors. All local blade incline angles on the leading edge may be within around ±5 ° of a mean blade incline angle. Because the local blade incline angles on the leading edge are within ±5 0 of the mean angle of incidence, this ensures that the blade incline angles do not significantly diverge from one another. Accordingly, the profile of the blade is roughly constant from the hub to the tip. Such geometry exhibits lower internal stresses and is easier to manufacture. All local blade incline angles on the leading edge may be substantially the same. When all of the local blade incline angles are the same, this ensures that the profile of the blade is constant from the hub to the tip. Such geometry exhibits lower internal stresses and is easier to manufacture. The leading edge may define a substantially straight profile between the hub and the tip. Because the leading edge is substantially straight from the hub to the tip, the profile of the leading edge leads to reduced internal stresses under high centrifugal loading as compared to non-straight leading edge profiles. The leading edge may extend between the hub and the tip in a direction substantially parallel to the central axis. The term “substantially parallel” encompasses the leading edge being exactly parallel to the central axis or being inclined relative to the central axis by up to around 5 °. The compressor wheel may define a compressor wheel outer diameter (D1) and the turbine wheel defines a turbine wheel outer diameter (D2), and wherein the ratio of the compressor wheel outer diameter to the turbine wheel outer diameter (D1 / D2) at most 1.5, and more preferably is between around 1.2 to around 1.5, or most preferably is between around 1.3 to around 1.5. Because the compressor wheel outer diameter (D1) is less than 1.5 times the turbine wheel outer diameter (D2), this limits the net axial thrust produced by the compressor back face upon the shaft. In such arrangements, the use of a backswept turbine wheel is able to provide increased efficiency to match the increased rotational speeds required by the compressor wheel to achieve adequate compression of the intake air. The degree of back-sweeping of the leading edge may increase with decreasing ratio of compressor wheel outer diameter to turbine wheel outer diameter (D1 / D2). The blade incline angle (<p) may be selected based upon the formula: DI (p = 185 — 100 x The blade may comprise a pressure surface defining a profile according to the parameters in Table 1. The turbine wheel may be a radial or mixed-flow turbine wheel. Accordingly, the turbine may therefore be a radial or mixed-flow turbine. According to a second aspect of the invention there is provided a fuel cell system comprising: a fuel cell; and a turbocharger according to the fist aspect of the invention. Brief Description of the Drawings A brief description of the invention is set out below with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional schematic view through a turbocharger according to the present invention for a fuel cell system; Figure 2 is a perspective view of a turbine wheel for use within the turbocharger of the present invention; Figure 3 is a side view of the turbine wheel of Figure 2; Figure 4 is a cross-sectional plan view of the turbine wheel taken through the line X-X of Figure 3; Figure 5 is a schematic meridional view of a blade of the turbine wheel according to the present invention; and Figure 6 is a further perspective view of the turbine wheel illustrating an angular position of a pressure surface of the turbine wheel. Detailed Description Figure 1 shows a schematic view of a turbocharger 2 for a fuel cell system. The turbocharger 2 comprises a compressor 4 and a turbine 6 connected via a shaft 8 supported for rotation about an axis A. The compressor 4 comprises a compressor wheel 10 mounted to the shaft 8. The compressor wheel 10 is contained within a compressor housing 11. The compressor wheel 10 comprises a plurality of compressor blades 12. The blades 12 impart a compressive force on the intake air so as to move the intake air from a compressor inlet 14 to a compressor outlet 16. The compressor wheel 10 comprises a back face 18 and defines a diameter D1 with respect to the axis A. The turbine 6 comprises a turbine wheel 20 mounted to an opposite end of the shaft 8 to the compressor wheel 10. The turbine 6 comprises a turbine housing 22 within which the turbine wheel 20 is positioned. The turbine housing 22 defines a turbine inlet 24 and a turbine outlet 26. The turbine wheel 20 comprises a plurality of turbine blades 28 distributed around the axis A. The turbine blades 28 extract work from exhaust gas received from the turbine inlet 24, causing rotation of the shaft 8 so as to provide rotational energy to the compressor wheel 10. The turbine wheel 20 comprises a back face 30 and defines a diameter D2 with respect to the axis A. The diameter D1 is approximately 1.5 times the size of the diameter D2. The turbocharger 2 further comprises a motor 36 positioned between the compressor 4 and the turbine 6. The motor 36 comprises a housing 37 containing an inductor portion 38. The inductor portion 38 contains a plurality of coils of electrically conducting wire configured to produce and / or receive a magnetic field surrounding the shaft 8. The motor 36 further comprises a permanent magnet portion 40. The permanent magnet portion 40 is housed within the shaft 8. In particular, the permanent magnet portion 40 may be integrally formed with the shaft 8. Accordingly, the inductor portion 38 acts as a stator of the motor 36 whilst the permanent magnet portion 40 acts as a rotor of the motor 36. During use, an electric current provided to the inductor portion 38 produces a magnetic field that drives rotation of the shaft 8 in the same direction as the rotation produced by the turbine 6. Accordingly, the turbine 6 and the motor 36 act in tandem to meet the rotational power requirements of the compressor 4. It will be appreciated that in alternative embodiments substantially any suitable construction of motor 36 may be employed provided that this enables the shaft 8 to be driven using electrical energy. During use, the pressure of the compressed intake air acts on the back face 18 resulting in an axial force acting in the direction from the turbine 6 towards the compressor 4 (i.e. from right to left in Figure 1). Likewise, the pressure of the exhaust gas in the turbine inlet 24 acts on the back face 30 resulting in an axial force acting in the direction from the compressor 4 towards the turbine 6 (i.e. from left to right in Figure 1). However, because the diameter D1 of the compressor wheel 10 is greater than the diameter D2 of the turbine wheel 20, the resultant force produced by the compressor wheel 10 is larger than the resultant force produced by the turbine wheel 20. Accordingly, this results in a net thrust load acting along the axis A in the direction from the turbine 6 towards the compressor 4 (i.e. right to left in Figure 1). In order to react the axial thrust load and maintain the compressor wheel 10, shaft 8, and turbine wheel 20 in the correct axial position, the turbocharger 2 further comprises a thrust bearing 32 configured to prevent movement of the shaft 8 towards the compressor 4. In particular, the thrust bearing 32 comprises a rotor portion 34 connected to the shaft 8 and a stator portion 36 connected to the housing 37 of the motor 36. Because the turbocharger 2 is for use with a fuel cell system, it is imperative that contamination of the intake air within the compressor outlet 16 is avoided, as this may damage the membranes of the fuel cell. Accordingly, the thrust bearing 32 is, in particular, a gas-lubricated thrust bearing. Such gas-lubricated thrust bearings use gaseous aerodynamic forces rather than liquid lubrication to provide a low-friction bearing between the stator portion 36 and the rotor portion 34. Such gas lubrication is achieved using the intake air already present within the compressor outlet 16. Figure 2 shows a perspective view of the turbine wheel 20. The turbine wheel 20 comprises a hub 42 surrounding an axis B about which the plurality of blades 28 are distributed. During use, the axis B is substantially aligned with I the same as the axis A of the shaft 8. Each blade 28 defines a leading edge 44, a trailing edge 46, a root 48 and a tip 50. The leading edge 44 defines the most upstream portion of the blade 28 with respect to the working fluid. The trailing edge 46 defined the most downstream portion of the blade 28 with respect to the working fluid. The root 48 defines the join between the blade 28 and the hub 42. The tip 50 defines the terminal extent of the blade 28 relative to the hub 42, and runs between the leading edge 44 and the trailing edge 46. During use, the turbine wheel 20 rotates in an anti-clockwise direction from the perspective shown in Figure 2 and denoted by the arrow labelled w, such that each blade 28 defines a pressure surface 52 and a suction surface 54. Figure 3 shows a side view of the turbine wheel 20 showing a section line X-X running perpendicular to the axis B at a point approximately half way along the leading edges 44 of the blades 28. Figure 4 shows a cross-sectional plan view taken through the section line X-X of Figure 3 and looking towards the trailing edges 46. As shown in Figure 3, the leading edges 44 of each blade 28 define a blade incline angle <p. The blade incline angle cp is the angle subtended between a radius r originating from the axis B and a tangent 56 of the pressure surface 52 taken at the leading edge 44. The blade incline angle (p is said to be positive in the same angular direction as the direction of rotation w (i.e. clockwise from the perspective shown in Figure 4). Because the blade incline angle (p is positive, this causes the pressure surface 52 of the blade to be inclined generally away from the incoming fluid stream. Accordingly, positively-inclined blade angles q> are said to define so-called “back-swept” blades 28. As described above, the thrust load reacted by the thrust bearing 32 is a product of the difference in size between the diameter D1 of the compressor wheel 10 and the diameter D2 of the turbine wheel 20. If the compressor wheel 10 is too large in comparison to the turbine wheel 2, the axial thrust produced may be too high to be reacted under gas-lubrication. Accordingly, it has been found that the ratio of the compressor wheel outer diameter to the turbine wheel outer diameter D1 / D2 should be at most 1.5, or more preferably between around 1.2 to around 1.5, or most preferably between around 1.3 to around 1.5. Moreover, as previously discussed, the turbine 6 and the motor 36 act in tandem to meet the rotational power requirements of the compressor 4. In particular, the compressor 4 must be operated so that the intake air compressed reaches a desired compression pressure. It has been found that when the compressor wheel 10 and turbine wheel 20 are relatively sized within the ranges above, the rotational speed that the compressor wheel 10 requires in order to meet the desired output pressure is relatively high. Accordingly, the ratio of the blade speed U to the velocity C of the incoming working fluid experienced by the turbine wheel 20 increases. However, because the blade incline angle ¢) is positive, the angle of incidence between the oncoming working fluid and the blade 28 at high rotational speeds (i.e. high U / C) is reduced. This reduces the occurrence of boundary-layer separation over the leading edge 44 and the formation of turbulence on the suction surface 54. As a result, the rotational speed <p at which the optimum efficiency of the turbine wheel 20 occurs is increased, so that this better matches the increased rotational speed required by the compressor wheel 10 to reach the desired compression pressure. In the illustrated embodiment, the blade incline angle (p is substantially constant for all points on the leading edge 44. However, it will be appreciated that in alternative embodiments each point on the leading edge 44 made define a local blade incline angle may vary between the root 48 and the tip 50. However, it will be appreciated that in order to provide the above described advantages, all local blade incline angles (p should be positive (i.e. inclined in the positive angular direction). Nevertheless, it is generally preferable if the local blade incline angles cp are tightly grouped. In particular, it has been found that the local blade incline angles <p along the leading edge 44 should be within ±5 0 of a mean local blade incline angle <p. The blade incline angle in the embodiment shown in Figures 2 to 4 is around 45 °. However, it will be appreciated that the blade incline angle may be varied in dependence upon the relative size difference between the turbine wheel 20 and the compressor wheel 10. In particular, the blade incline angle <p may be determined based upon the formula: DI (O = 185 - 100 x — >m where D1 is the compressor wheel 10 diameter and D2 is the turbine wheel 20 diameter. Nevertheless, in general terms, it has been found that the blade incline angle (p should be within the range of around 10 ° to around 80 °, around 25 0 to around 65 or around 40 ° to around 50 °. Figure 5 shows a schematic meridional view of a pressure surface 52 of a blade 28 of the turbine wheel 20. The pressure surface 52 defines a parameterised co-ordinate system comprising a span-wise parameter u and a chord-wise parameter v. The spanwise parameter u extends across the span of the blade from the hug 42 to the tip 50. The span-wise parameter u is said to be 0 at the blade root 48 and is said to be 1 at the tip 50. The chord-wise parameter v extends along the meridional profile of the blade 28 from the leading edge 44 to the trailing edge 46. The chord-wise parameter v is said to be 0 at the leading edge 44 and is said to be 1 at the trailing edge 46. Figure 6 shows the same view of the turbine wheel 20 as Figure 2 describe above, and depicts a third component of the co-ordinate system. The third component is the angular surface position 0. The angular surface position 0 is said to be 0 ° at the intersection of the root 48 and the leading edge 44. The angular surface position 0 is measured in absolute terms, and in the present case is measured in degrees. The angular surface position 0 is positive in the direction of rotation w. The angular surface position 0 of the pressure surface 52 of the blade 28 at each parameter u, v may be defined by the values set out in Table 1 set out below: 0 span-wise parameter u 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 chord-wise parameter v 0 0 0 0 0 0 0 0 0 0 0 0 0.1 -10 -9 -9 -8 -8 -7 -7 -7 -6 -6 -6 0.2 -18 -17 -16 -15 -15 -14 -13 -13 -12 -12 -11 0.3 -24 -23 -22 -22 -21 -20 -19 -19 -18 -18 -17 0.4 -28 -28 -27 -27 -26 -26 -25 -25 -24 -23 -22 0.5 -32 -32 -32 -32 -32 -31 -31 -30 -30 -29 -28 0.6 -36 -37 -37 -37 -37 -37 -37 -37 -36 -36 -35 0.7 -43 -43 -44 -44 -44 -44 -44 -44 -44 -43 -43 0.8 -52 -52 -52 -53 -53 -53 -53 -52 -52 -52 -52 0.9 -65 -64 -64 -63 -63 -63 -63 -63 -62 -62 -62 1 -80 -78 -77 -76 -76 -75 -75 -74 -74 -74 -73 Table 1 With reference to Figure 3, it can be seen that the leading edge 44 defines a substantially straight profile relative to the axis B. In particular, the leading edge 44 runs substantially parallel to the axis B. However, in alternative embodiments the leading edge 44 may be inclined relative to the axis B by up to around 5 Because the 10 profile of the leading edge 44 is straight and approximately parallel to the axis B, this leads to reduced internal stresses under high centrifugal loading as compared to nonstraight leading edge profiles. Although the turbine wheel 20 described above is illustrated as a radial flow turbine 15 wheel in which the incoming working fluid has little or no axial momentum, it will be appreciated that in alternative embodiments the turbine wheel 20 may be a mixed-flow turbine wheel, in which the incoming working fluid has some degree of axial momentum.

Claims

1. A turbocharger for a fuel cell system, the turbocharger comprising:a shaft supported for rotation about a central axis (A);a compressor wheel rotationally connected to the shaft;a turbine wheel rotationally connected to the compressor via the shaft;a motor electro-magnetically connected to the shaft for rotationally driving the shaft; anda gas-lubricated thrust bearing arranged to react a resultant axial load applied to the shaft by the compressor wheel and the turbine wheel;wherein the turbine wheel comprises a blade defining a leading edge, the leading edge defining a blade incline angle (<p) being inclined relative to a radial direction (r) originating from the central axis (A) in a positive angular direction relative to the direction of rotation (co) of the turbine during use.

2. A turbocharger according to claim 1, wherein:the turbine wheel comprises a hub;the blade defines a tip extending between the leading edge and the trailing edge; andwherein all points on the leading edge define a local blade incline angle relative to the radial direction, and wherein all local blade incline angles on the leading edge are inclined in the positive angular direction.

3. A turbocharger according to claim 2, wherein all local blade incline angles on the leading edge are inclined relative to the radial direction by around 10 ° to around 80 °, or more preferably by around 25 ° to around 65 °, or more preferably around 40 ° to around 50 or most preferably are around 45 °.

4. A turbocharger according to claims 2 or 3, wherein all local blade incline angles on the leading edge are within around ±5 ° of a mean blade incline angle.

5. A turbocharger according to any of claims 2 to 4, wherein all local blade incline angles on the leading edge are substantially the same.

6. A turbocharger according to any of claims 2 to 5, wherein the leading edge defines a substantially straight profile between the hub and the tip.

7. A turbocharger according to claim 6, wherein the leading edge extends between the hub and the tip in a direction substantially parallel to the central axis.

8. A turbocharger according to any preceding claim, wherein the compressor wheel defines a compressor wheel outer diameter (D1) and the turbine wheel defines a turbine wheel outer diameter (D2), and wherein the ratio of the compressor wheel outer diameter to the turbine wheel outer diameter (D1 / D2) at most 1.5, and more preferably is between around 1.2 to around 1.5, or most preferably is between around 1.3 to around 1.5.

9. A turbocharger according to claim 8 wherein the blade incline angle (q>) is selected based upon the formula:DI (p = 185 — 100 x10. A turbocharger according to any preceding claim, wherein the blade comprises a pressure surface defining a profile according to the parameters in Table 1.

11. A turbocharger according to any preceding claim, wherein the turbine wheel is a radial or mixed-flow turbine wheel.

12. A fuel cell system comprising:a fuel cell; anda turbocharger according to any preceding claim.Application No: GB2314197.1Examiner: Mr Keir HoweClaims searched: 1-12Date of search: 27 February 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance Y 1-12 WO 2019 / 087970 Al (IHI CORP) See figure 2 for example, noting turbocharger, suitable for a fuel cell, with compressor wheel 31, turbine wheel 21, shaft 4, motor 5 and gas-lubricated thrust bearings 8. Y 1-12 WO 2017 / 168766 Al (MITSUBISHI HEAVY IND LTD) See figure 3 for example, noting turbocharger turbines may have positive blade lean angles. Y 1-12 EP 3771802 Al (GARRETT TRANSP I INC) See figure 12, for example, noting turbocharger turbines may have positive blade lean angles. Y 1-12 Shar et al., Journal of Applied Fluid Mechanics, published 2016, ppi 791-98, Vol 9 No.4, "Study of Flow Patterns in Radial and Back Swept Turbine Rotor under Design and Off-Design Conditions", Available from: https: / / pdfs.semanticscholar.org / dl4c / de9201337f84a72e8ccl74450602 92131019.pdf See whole document, noting use of turbines with backswept blade angles in turbochargers.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From F02C 0006 / 12 01 / 01 / 2006 F01D 0005 / 04 01 / 01 / 2006 F01D 0005 / 14 01 / 01 / 2006 HO IM 0008 / 04111 01 / 01 / 2016

Images