Turbocharger

Abstract

A turbocharger for an internal combustion engine is provided. The turbocharger comprises a compressor, a turbine and a bearing section. The compressor is configured to compress intake gas of the internal combustion engine. The turbine is configured to receive exhaust gas of the internal combustion engine. The bearing section is arranged between the compressor and the turbine. The compressor comprises a diffuser portion. The diffuser portion comprises a compressor-side diffuser portion having a first surface and a bearing-side diffuser portion having a second surface located opposite the first surface of the compressor-side diffuser portion. The compressor-side diffuser portion and the bearing-side diffuser portion are spaced apart to define a diffuser passage for intake gas which has been compressed by the compressor. The compressor-side diffuser portion defines a first cooling passage located adjacent to the first surface of the compressor-side diffuser portion, the first cooling passage configured to receive a flow of fluid to cool the first surface of the compressor-side diffuser portion. The bearing-side diffuser portion defines a second cooling passage located adjacent to the bearing-side diffuser portion, the second cooling passage configured to receive a flow of fluid to cool the second surface of the bearing-side diffuser portion.

Description

[0001] Turbocharger

[0002] Field of the disclosure

[0003] The present disclosure relates to internal combustion engines. In particular, the present disclosure relates to turbochargers for internal combustion engines.

[0004] Background

[0005] A turbocharger may be provided as part of an internal combustion engine. In general, a turbocharger typically comprises a turbine section which is configured to extract energy from exhaust gasses of the internal combustion engine. The turbocharger also comprises a compressor. The compressor is configured to compress intake gas to the internal combustion engine, in order to allow the internal combustion engine to generate more power. Typically, the turbocharger comprises a central bearing section which connects the turbine to the compressor. Thus, turbocharger extracts energy from the exhaust gas using the turbine in order to drive the compressor.

[0006] US-A-2019 / 226501 discloses one example of a turbocharger known in the art.

[0007] Against this background, an improved, or at least commercially relevant alternative, turbocharger is provided.

[0008] Summary

[0009] According to a first aspect of the disclosure, a turbocharger for an internal combustion engine is provided. The turbocharger comprises: a compressor configured to compress intake gas of the internal combustion engine; a turbine configured to receive exhaust gas of the internal combustion engine; and a bearing section arranged between the compressor and the turbine; wherein the compressor comprises a diffuser portion, the diffuser portion comprising: a compressor-side diffuser portion having a first surface; and a bearing-side diffuser portion having a second surface located opposite the first surface of the compressor-side diffuser portion, wherein the compressor-side diffuser portion and the bearing-side diffuser portion are spaced apart to define a diffuser passage for intake gas which has been compressed by the compressor, the compressor-side diffuser portion defines a first cooling passage located adjacent to the first surface of the compressor-side diffuser portion, the first cooling passage configured to receive a flow of fluid to cool the first surface of the compressor-side diffuser portion; and the bearing-side diffuser portion defines a second cooling passage located adjacent to the bearing-side diffuser portion, the second cooling passage configured to receive a flow of fluid to cool the second surface of the bearing-side diffuser portion.

[0010] The turbocharger of the first aspect comprises a diffuser portion having first and second surfaces which define a diffuser passage for intake gas which has been compressed by the compressor. During use, the first and second surfaces of the diffuser portion may become heated due to the compressed intake gas flowing through the diffuser portion. If the first and second surfaces become excessively heated, particulate (e.g. oil particles) in the intake gas may be more likely to settle on the first and second surfaces. This fouling (or coking) of the diffuser portion may lead to reduced performance of the turbocharger.

[0011] The turbocharger of the first aspect includes first and second cooling passages which are configured to cool the first and second surfaces of the diffuser portion respectively. By cooling both sides of the diffuser portion, the turbocharger may reduce or eliminate fouling of the diffuser portion, even when the intake gas comprises a high amount of particulate.

[0012] In particular, the turbocharger of the first aspect may be particularly suitable for use in an internal combustion engine having a closed crankcase ventilation circuit (closed breather circuit). In such internal combustion engines, gas present in a crankcase of the internal combustion engine may be recirculated by the closed crankcase ventilation circuit to an intake of the compressor. While such closed crankcase ventilation circuits are important for reducing emissions from an internal combustion engine, the recirculation of crankcase gas also means that the intake gas compressed by the compressor comprises a relatively high amount of particulate (e.g. engine oil particles). The cooling passages of the first aspect may help to reduce or eliminate fouling of the compressor when a closed crankcase ventilation circuit is utilised. According to a second aspect of the disclosure an internal combustion engine is provided. The internal combustion engine comprises the turbocharger of the first aspect, wherein the internal combustion engine is configured to supply fluid to the first and second cooling passages.

[0013] The internal combustion engine is configured to supply the fluid used to cool the diffuser portion of the turbocharger. Thus, the internal combustion engine may provide cooling of the diffuser portion in an economic and efficient manner.

[0014] Brief discussion of the figures

[0015] Embodiments of the disclosure will now be described with reference to the following nonlimiting figures in which:

[0016] Fig. 1 is a block diagram of an internal combustion engine 1;

[0017] Fig. 2 is a cross-sectional diagram of a turbocharger according to an embodiment of the disclosure;

[0018] Fig. 3 is a detailed view of the compressor of the turbocharger of Fig. 2;

[0019] Fig. 4 is a wireframe diagram of the compressor of Fig. 2;

[0020] Fig. 5 is a wireframe diagram of the compressor of Fig. 2 viewed from the bearing side;

[0021] Fig. 6 is a side view of the turbocharger of Fig. 2; and Fig. 7 is a sectional view of the turbocharger of Fig. 2.

[0022] Detailed description

[0023] According to an embodiment of the disclosure, a turbocharger 10 for an internal combustion engine 1 is provided. Fig. 1 shows a schematic system diagram of the turbocharger 10 and the internal combustion engine 1.

[0024] The turbocharger 10 comprises a compressor 20, a bearing section 30, and a turbine 40.

[0025] As shown in the system diagram of Fig. 1, the compressor 20 of the turbocharger 10 may be configured to receive an intake gas from an air intake filter 12 and / or a closed crankcase ventilation circuit 14. The compressor 20 of the turbocharger 10 may output the compressed intake gas directly to the internal combustion engine 1, or as shown in Fig. 1, via an aftercooler 16. The turbine 40 of the turbocharger 10 may be configured to receive gas from the internal combustion engine 1. The flow of various gasses to and from the internal combustion engine 1 are indicated in Fig. 1 using dashed lines.

[0026] As shown schematically in Fig. 1, the turbine 40 comprises a turbine blade assembly 42 and the compressor 20 comprises a compressor impeller 22. The turbine blade assembly 42 is connected to the compressor impeller 22 via a bearing 32 of the bearing section 30.

[0027] Fig. 2 shows a cross-sectional view of a turbocharger 10 according to an embodiment of the disclosure. The cross-sectional view of the turbocharger 10 is taken through a central axis of the turbocharger 10 which is aligned with a central axis of the compressor impeller 22, bearing 32, and turbine blade assembly 42.

[0028] As shown in Fig. 2, the compressor 20 comprises a compressor housing 23. The compressor housing 23 defines a conduit for intake gas which flows from an inlet 24 of the compressor housing to an outlet 25 of the compressor housing 23. Along the conduit, the intake gas is compressed by the compressor impeller 22.

[0029] The conduit of the compressor 20 comprises a plurality of portions. Each portion of the conduit may be defined by a part of the compressor housing 23 and the sealing wall 76 which separates the compressor 20 from the bearing section 30. As shown in Fig. 2, the compressor housing 23 may define, at least in part, an inlet portion 50 of the conduit, an impeller portion 60 of the conduit, a diffuser portion of the conduit 70 and a scroll portion 80 of the conduit. The sealing wall 76 may also define at least part of the impeller portion 60, the diffuser portion 70 and the scroll portion 80.

[0030] The inlet portion 50 of the conduit extends from the inlet 24 to the impeller portion 60 of the conduit. The inlet portion 50 has a generally frustoconical shape such that a diameter of the conduit decreases along the axial length of the conduit from the inlet 24 towards the bearing section 30. The generally frustoconical shape of the inlet portion 50 may be provided by an internal surface of the compressor housing 23 as shown in Fig. 2. As shown in Fig. 2, a central axis of the frustoconical inlet portion 50 is aligned with the central axis of the compressor impeller 22. The impeller portion 60 of the conduit is the region of the conduit in which the compressor impeller 22 is located. The impeller portion 60 of the conduit has a generally cylindrical shape. The generally cylindrical shape of the impeller portion 60 may be provided by an internal surface of the compressor housing 23 as shown in Figs. 2 and 3. A central axis of the cylindrical portion 60 is aligned with the central axis of the compressor impeller 22. Intake gas flows from the impeller portion 60 of the conduit into the diffuser portion 70 of the conduit.

[0031] As will be understood by the skilled person, the compressor impeller 22 is configured to rotate in the impeller portion 60 of the conduit in order to compress the intake gas. Rotation of the impeller 22 is driven by rotation of the turbine 42.

[0032] The diffuser portion 70 is configured to direct the compressed intake gas from the impeller portion 60 to a scroll portion 80 of the compressor 20. As shown in Fig. 2, the diffuser portion 70 generally encircles the impeller portion 60 such that the compressed intake gas flow radially outward from the central axis of the impeller portion 60 through the diffuser portion 70. As such, the diffuser portion 70 of the conduit may have a generally annular shape.

[0033] Fig. 3 shows a detailed view of the impeller portion 60, diffuser portion 70, and scroll portion 80 of the compressor 20. As shown in Fig. 3, the diffuser portion 70 comprises a compressor-side diffuser portion 72, and a bearing-side diffuser portion 74 which together define the conduit of the diffuser portion 70.

[0034] The compressor side diffuser portion 72 has a first surface 73. That is to say, a first surface 73 of the diffuser portion 70 is provided by the compressor side diffuser portion 72. As shown in Fig. 3, the first surface 73 may be provided by part of the compressor housing 23. The first surface 73 of the compressor-side diffuser portion 72 may have a generally annular shape. As such, a central region of the annular shape accommodates the compressor impeller 22. Compressed intake gas then flows radially outward past the generally annular shape of the first surface 73.

[0035] In the embodiments of Fig. 3, the first surface 73 of the diffuser portion is a generally planar surface. The first surface 73 is arranged in the diffuser portion 70 such that the planar first surface 72 extends in a radial direction (i.e. in a direction transverse to the central axis of the compressor 20). Thus, the intake gas which enters the compressor 20 in a generally axial direction, is compressed by the compressor and then flows generally radially outward through the diffuser portion 70.

[0036] The bearing-side diffuser portion 74 has a second surface 75 located opposite the first surface 73 of the compressor-side diffuser portion 72. The bearing-side diffuser portion 74 may be provided as part of a 76 sealing wall provided between compressor 20 and bearing section 30. The sealing wall 76 may be a part which seals the compressor conduit from the bearing section 30 of the turbocharger 10. As such, the bearing-side diffuser portion 76 is configured to separate the compressor 20 from the bearing section 30.

[0037] As shown in Figs. 2 and 3, the sealing wall 76 may have a central axis which is aligned with the central axis of the compressor 20. A central region of the sealing wall 76 may be provided which is configured to accommodate the impeller 22. The second surface 75 of the bearing-side diffuser portion 74 may be provided as a generally annular shaped surface which surrounds the central region of the sealing wall 76 on the compressor-side of the sealing wall 76.

[0038] As shown in Figs. 2 and 3, the second surface 75 may be a generally planar surface. The second surface 75 may extend in a generally radial direction (i.e. a transverse direction).

[0039] The compressor-side diffuser portion 72 and the bearing-side diffuser portion 74 are spaced apart to define a diffuser passage of the conduit for intake gas which has been compressed by the compressor 20. As shown in Figs. 2 and 3, the first and second surfaces 73, 75 are spaced apart in a direction generally aligned with the central axis of the compressor 20. As such, a thickness of the diffuser passage may be generally uniform through the diffuser portion 70 of the conduit. In other embodiments, a thickness of the diffuser portion 70 of the conduit may vary in the radial direction. For example, a thickness of the diffuser portion may reduce from the an opening thickness proximal to the impeller to a mid-section thickness of the diffuser portion 70. The opening thickness (in the axial direction) may be reduced by about 50 % at the middle of the diffuser portion 70, for example as shown in Figs. 2 and 3.

[0040] The diffuser portion 70 provides a channel for compressed intake gas to flow through to a scroll portion 80 of the conduit. The scroll portion 80 of the compressor comprises a scroll outlet 82 which is connected to a pipe 84 which directs the compressed intake gas onto the internal combustion engine 1 via aftercooler 16. In some embodiments, the pipe 85 may directed the compressed intake gas directly to the internal combustion engine 1.

[0041] The scroll portion 80 of the conduit is a generally annular shapes conduit which surrounds the annular shaped diffuser portion 70. The scroll portion 80 is configures to allow the compressed intake gas to circulate around the scroll portion to the scroll outlet 82. As shown in Figs. 2 and 3, the scroll portion 80 may be formed in part from the compressor housing 23 and the sealing wall 76.

[0042] In use, the compression of intake gas increases the thermal energy of the intake gas, and thus the internal surfaces of the turbocharger 10 are heated by the compressed intake gas. In particular, the first and second surfaces 73, 75 of the diffuser portion 70 may be heated by the compressed intake gas. Where the first and second surfaces 73, 75 are heated to a sufficiently high temperature, the first and second surfaces 73, 75 of the diffuser portion 70 may be prone to fouling (e.g. coking) as a result of particulate present in the intake gas.

[0043] In some embodiments, the internal combustion engine 1 may comprise a closed crankcase ventilation circuit 14. The closed crankcase ventilation circuit 14 may be configured to recirculate crankcase gas of the internal combustion engine to the compressor 20, such that the intake gas may include gas from the crankcase. Such gas may comprise a relatively high amount of particulate matter, thereby increasing the likelihood and / or severity of the fouling of the diffuser portion 70.

[0044] Thus, embodiments of this disclose may seek to reduce the temperature of the first and second surfaces 73, 75 of the diffuser portion 70 in order to reduce or prevent the fouling of the diffuser portion 70.

[0045] Accordingly, as shown in Fig. 1, the compressor-side diffuser portion 72 defines a first cooling passage 77 located adjacent to the first surface 73 of the compressor-side diffuser portion 72, the first cooling passage 77 configured to receive a flow of fluid to cool the first surface 73 of the compressor-side diffuser portion 72. As shown in the cross-sections of Figs. 2 and 3, the first cooling passage 77 generally encircles the central axis of the compressor 20. As such, the first cooling passage 77 is generally aligned with the annular shape of the first surface 73. In the embodiment of Figs. 2 and 3, the first cooling passage 77 is defined by the compressor housing 23. That is to say, the first cooling passage 77 is provided as passages which extends internally thought the compressor housing adjacent to the first surface 73.

[0046] As will be appreciated, the first cooling passage 77 is configured to cool the first surface 73 of the compressor-side diffuser portion 72. Accordingly, the first cooling passage 77 may be located adjacent to the first surface 73 such that heat may be efficiently transferred from the first surface 73 to the fluid circulating within the first cooling passage 77. For example, the first cooling passage 77 may be located at a position which is closer to the first surface 73 than any other internal surface of the compressor housing 23. For example, the first cooling passage may be located such that it is closer to first surface 73 than the internal surface of the impeller portion 60. In the embodiment of Figs. 2 and 3, the first cooling passage 77 is offset from the first surface in the axial direction by a first offset distance.

[0047] The first offset distance may be about the same distance as the spacing between the first and second surfaces 73, 75 of the diffuser portion 70.

[0048] In the embodiment of Figs. 2 and 3, the compressor-side diffuser portion 72 defines a first cooling passage 77 having a first end 77a and a second end 77b, wherein the first cooling passage 77 extends from the first end to the second end around the annular shape of the compressor-side diffuser portion 72 by at least 300°. That is to say, the first cooling passage extends around a sector of at least 300° of the annular diffuser portion 70. In other embodiments, the first cooling passage 77 may define a bifurcated cooling passage from an inlet to an outlet located on opposing sides of the diffuser passage (e.g. the inlet and outlet may be 180° apart). Fig. 4 is a schematic wireframe diagram of the turbocharger 10 viewed from the compressor end which shows the first cooling passage 77 extending around the central axis of the impeller 60 according to an embodiment of the disclosure.

[0049] In some embodiments, the first cooling passage 77 may have a cross-sectional shape which is generally circular, elliptical, square, rectangular, or any other form of polygon (regular or irregular). In the embodiment of Figs. 2-4, the first cooling passage 77 may have a nominal cross-sectional shape (nominally circular in Fig. 2) and include heattransfer features 90, 92. The heat transfer features 90, 92 may cause the cross-section of the first cooling passage 77 to deviate from the nominal (circular) shape, such that the length of the perimeter of the cross-section is increased. As such, the cross-section of the internal surface of the first cooling passage 77 may comprise a plurality of concave heat transfer features 90 and a plurality of convex heat transfer features 92. In effect, the internal surface area of the first cooling passage 77 may be increased by the concave and convex heat transfer features 90, 92 in order to improve the efficiency of heat transfer from the first surface 73 to the first cooling passage 77. It will be appreciated that various shapes may be used for the heat transfer features 90, 92 and / or the nominal shape of the first cooling passage 77.

[0050] Thus, the first cooling passage 77 may be provided in order to cool the first surface 73 of the diffuser portion 70.

[0051] As shown in Figs. 2 and 3, the bearing-side diffuser portion 74 defines a second cooling passage 78 located adjacent to the bearing-side diffuser portion 74. The second cooling passage 78 may be configured to receive a flow of fluid to cool the second surface 75 of the bearing-side diffuser portion 74. Accordingly, the second cooling passage 78 may be located adjacent to the second surface 75 such that heat may be efficiently transferred from the second surface 75 to the fluid circulating within the second cooling passage 78. For example, the second cooling passage 78 may be located at a position which is closer to the second cooling passage 78 than any other internal surface of the compressor 20. In the embodiment of Figs. 2 and 3, the second cooling passage 78 may be offset from the second surface 75 in the axial direction by a second offset distance. The second offset distance may be similar to distance of the spacing between the first and second surfaces 73, 75 of the diffuser portion 70.

[0052] In the embodiment of Figs. 2 and 3, the bearing-side diffuser portion 74 defines a second cooling passage 78 having a first end (not shown in Fig. 2) and a second end (not shown in Fig. 2), wherein the second cooling passage 78 extends from the first end to the second end around the annular shape of the bearing-side diffuser portion 74 by at least 300°. That is to say, the second cooling passage 78 extends around a sector of at least 300° of the annular diffuser portion 70. In other embodiments, the second cooling passage 78 may define a bifurcated cooling passage from an inlet to an outlet located on opposing sides of the diffuser passage (e.g. the inlet and outlet may be 180° apart). Fig. 5 shows a schematic wireframe view of the compressor 20 from the bearing-side of the compressor 20. The second cooling passage 78 is highlighted in the diagram and arrows indicate the direction of fluid flow from the first end 78a of the second cooling passage 78 to the second end 78b.

[0053] In some embodiments, the second cooling passage 78 may have a cross-sectional shape which is generally circular, elliptical, square, rectangular, or any other form of polygon (regular or irregular). In the embodiment of Figs. 2 and 3, the second cooling passage 78 has a nominal cross-sectional shape (nominally rectangular, or an elongated ellipse in Fig. 2) and includes heat-transfer features 90, 92. The heat transfer features 90 cause the cross-section of the second cooling passage 78 to deviate from the nominal (rectangular) shape, such that the length of the perimeter of the cross-section is increased. As such, the cross-section of the internal surface of the second cooling passage 78 comprises a plurality of concave heat transfer features 90 and a plurality of convex heat transfer features 92. In effect, the internal surface area of the second cooling passage 78 is increased by the concave and convex heat transfer features 90, 92 in order to improve the efficiency of heat transfer from the second surface 75 to the second cooling passage 78. It will be appreciated that various shapes may be used for the heat transfer features 90, 92 and / or the nominal shape of the second cooling passage 78.

[0054] In some embodiments, the first and second cooling passages 77, 78 may be supplied with a fluid (i.e. a cooling liquid) which is configured to cool the first and second surfaces 73, 75 of the diffuser portion 70. For example, the fluid may be water or air, or any other suitable cooling fluid or cooling liquid (i.e. a fluid at a lower temperature than the first and second surfaces 73, 75).

[0055] In order to supply fluid to the first and second cooling passages 77, 78, the first and second cooling passages 77, 78 may each be connected to a supply of fluid. Fig. 6 shows a further view of the turbocharger 10 which shows a common coolant feed pipe 100 and a common coolant drain pipe 110 for the turbocharger 10. The common coolant feed pipe 100 may comprise an inlet 102 configured to receive a flow of fluid from the supply of fluid. The common coolant feed pipe 100 may be configured to direct the flow of fluid to the first and second cooling passages 77, 78. As such, the common coolant feed pipe 100 may bifurcate at a point downstream from the inlet into a first feed pipe 103 which is connected to the inlet 102 of the first cooling passage 77, and a second feed pipe 105 (not shown in Fig. 4) which is connected to the inlet 104 of the second cooling passage 78. The common coolant drain pipe 110 may be configured to receive the flow of fluid from the first and second cooling passages 77, 78 in respective first and second outlet pipes 113, 115 and to provide a common outlet 117 for the flow of fluid from the first and second cooling passages 77, 78. As such, the first and second cooling passages 77, 78 may be connected to a supply of fluid via the common inlet and may return the fluid for recirculation via the common outlet in a straightforward manner.

[0056] In some embodiments, for example a shown in Fig. 1, the first and second cooling passages 77, 78 may be cooled by a lubricant. In particular, the first and second cooling passages 77, 78 may be cooled by a lubricant which is also used to lubricate the bearing section 30 of the turbocharger 10. As such, the first and second cooling passages may be configured to receive a flow of lubricant from the internal combustion engine 1 to cool the compressor-side diffuser portion 72 and the bearing-side diffuser portion 74.

[0057] As shown in Figs. 1, 6, and 7, the bearing section 30 may comprise a lubricant feed pipe 34 configured to receive a supply of lubricant from the internal combustion engine 1. The lubricant feed pipe may also be configured to direct the supply of lubricant to the bearing section 30 in order to lubricate the bearing 32. The bearing section may also comprise a lubricant drain pipe 36 configured to receive lubricant from the bearing section 30 and to provide an outlet for lubricant from the turbocharger 10. As such, the lubricant drain pipe 36 may be connected to a lubricant reservoir (not shown) of the internal combustion engine 1.

[0058] By using the lubricant for the bearing 32 of the turbocharger 10 to also cool the first and second surfaces 73, 75, the diffuser portion 70 may be cooled in an efficient manner which does not require any additional fluid connections to be made to the turbocharger 10 when fitting the turbocharger 10.

[0059] For example, as shown in Fig. 1, the common coolant feed pipe 100 may be connected to the lubricant feed pipe 34, wherein the common coolant feed pipe 100 is configured to receive a flow of lubricant from the lubricant feed pipe 34. Similarly, the common coolant drain pipe 110 may be connected to the lubricant drain pipe 36, wherein the common coolant drain pipe 110 is configured to outlet lubricant to the lubricant drain pipe 36. Thus, in accordance with the above description, it will be appreciated that the first and second cooling passages 77, 78 may be configured to receive a flow of lubricant from the internal combustion engine 1 to cool the compressor-side diffuser portion 72 and the bearing-side diffuser portion 74.

[0060] In accordance with the above description, it will be appreciated that the internal combustion engine 1 may also comprise a supply of lubricant for lubricating the internal combustion engine 1. The internal combustion engine 1 may be configured to supply lubricant from the internal combustion engine 1 to the first and second cooling passages 77, 78 and to the bearing section 30 of the turbocharger 10.

[0061] Industrial applicability

[0062] According to embodiments of the disclosure, a turbocharger 10 and an internal combustion engine 1 are provided. The internal combustion engine 1 may be a diesel engine, a petrol engine, or may be an internal combustion engine 1 configured for any other suitable fuel type. The turbocharger 10 includes a diffuser portion 70 having first and second surfaces 73, 75 which define a diffuser passage 70 for intake gas which has been compressed by the compressor 20. During use, the first and second surfaces 73, 75 of the diffuser portion 70 may become heated due to the compressed intake gas flowing through the diffuser portion 70. If the first and second surfaces 73, 75 become excessively heated, particulate (e.g. oil particles) in the intake gas may be more likely to settle on the first and second surfaces 73, 75. This fouling (or coking) of the diffuser portion 70 may lead to reduced performance of the turbocharger 10.

[0063] The turbocharger 10 of the first aspect includes first and second cooling passages 77, 78 which may be configured to cool the first and second surfaces 73, 75 of the diffuser portion 70 respectively. By cooling both sides of the diffuser portion 70, the turbocharger 10 may reduce or eliminate fouling of the diffuser portion 70, even when the intake gas comprises a high relatively amount of particulate.

[0064] In particular, the turbocharger 10 may be particularly suitable for use in an internal combustion engine 1 having a closed crankcase ventilation circuit 14 (closed breather circuit). In such internal combustion engines 1, gas present in a crankcase of the internal combustion engine 1 may be recirculated by the closed crankcase ventilation circuit 14 to an intake of the compressor 20. While such closed crankcase ventilation circuits 14 are important for reducing emissions from an internal combustion engine 1, the recirculation of crankcase gas also means that the intake gas compressed by the compressor 20 comprises a relatively high amount of particulate (e.g. engine oil particles). The cooling passages 77, 78 may reduce or eliminate fouling of the compressor 20 when a closed crankcase ventilation circuit 14 is utilised.

[0065] Further, in some embodiments, the first and second cooling passages 77, 78 may be configured to receive a flow of lubricant from the internal combustion engine 1 to cool the compressor-side diffuser portion 72 and the bearing-side diffuser portion 74. In particular, the flow of lubricant may be received from the lubricant feed pipe 34 configured to receive a supply of lubricant to direct the supply of lubricant to the bearing section 30. Similarly, lubricant may be returned to the internal combustion engine 1 via the lubricant drain pipe 36. As such, the turbocharger 10 may be provided with a single lubricant inlet and a single lubricant outlet, which allows lubricant to be circulated to the bearing 32 and the first and second cooling passages 77, 78. Thus, the cooling of the diffuser portion 70 may be implemented on an internal combustion engine, or retrofitted to an existing internal combustion engine 1 without requiring any addition connections or an additional supply of coolant.

Claims

CLAIMS:

1. A turbocharger for an internal combustion engine, the turbocharger comprising: a compressor configured to compress intake gas of the internal combustion engine; a turbine configured to receive exhaust gas of the internal combustion engine; and a bearing section arranged between the compressor and the turbine; wherein the compressor comprises a diffuser portion, the diffuser portion comprising: a compressor-side diffuser portion having a first surface; and a bearing-side diffuser portion having a second surface located opposite the first surface of the compressor-side diffuser portion, wherein the compressor-side diffuser portion and the bearing-side diffuser portion are spaced apart to define a diffuser passage for intake gas which has been compressed by the compressor, the compressor-side diffuser portion defines a first cooling passage located adjacent to the first surface of the compressor-side diffuser portion, the first cooling passage configured to receive a flow of fluid to cool the first surface of the compressor-side diffuser portion; and the bearing-side diffuser portion defines a second cooling passage located adjacent to the bearing-side diffuser portion, the second cooling passage configured to receive a flow of fluid to cool the second surface of the bearing-side diffuser portion.

2. A turbocharger according to claim 1 , wherein the first and second cooling passages are configured to receive a flow of lubricant from the internal combustion engine to cool the compressor-side diffuser portion and the bearing-side diffuser portion.

3. A turbocharger according to claim 1 or claim 2, further comprising a common coolant feed pipe, the common coolant feed pipe configured to receive the flow of fluid and to direct the flow of fluid to the first and second cooling passages; and / or a common coolant drain pipe, the common coolant drain pipe configured to receive the flow of fluid from the first and second cooling passages and to provide a common outlet for the flow of fluid from the first and second cooling passages.

4. A turbocharger according to claim any of claims 1 to 3, wherein the bearing section comprises: a lubricant feed pipe configured to receive a supply of lubricant to direct the supply of lubricant to the bearing section; and a lubricant drain pipe configured to receive lubricant from the bearing section to provide an outlet for lubricant from the turbocharger.

5. A turbocharger according to claim 4 when dependent on claim 3 and claim 2, wherein the common coolant feed pipe is connected to the lubricant feed pipe such, wherein the common coolant feed pipe is configured to receive a flow of lubricant from the lubricant feed pipe; and / or the common coolant drain pipe is connected to the lubricant drain pipe, wherein the common coolant drain pipe is configured to outlet lubricant to the lubricant drain pipe.

6. A turbocharger according to any of claims 1 to 5, wherein the compressor-side diffuser portion has annular shape, wherein a central portion of the annular shape is configured to receive intake gas of the compressor.

7. A turbocharger according to claim 6, wherein the compressor-side diffuser portion defines a first cooling passage having a first end and a second end, wherein the first cooling passage extends from the first end to the second end around the annular shape of the compressor-side diffuser portion by at least 300°.

8. A turbocharger according to any of claims 1 to 7, wherein a cross-section of an internal surface of the first cooling passage comprises a plurality of concave heat transfer features and a plurality of convex heat transfer features.

9. A turbocharger according to any of claims 1 to 8, wherein the bearing-side diffuser portion is configured to separate the compressor from the bearing section.

10. A turbocharger according to any of claims 1 to 9, whereinthe second surface of the bearing-side diffuser portion has an annular shape.

11. A turbocharger according to claim 10, wherein the bearing-side diffuser portion defines a second cooling passage having a first end and a second end, wherein the second cooling passage extends from the first end to the second end around the annular shape of the bearing-side diffuser portion by at least 300°.

12. A turbocharger according to claim 10 or claim 11, wherein a cross-section of an internal surface of the second cooling passage comprises a plurality of concave heat transfer features and a plurality of convex heat transfer features.

13. An internal combustion engine comprising the turbocharger of any of claims 1 to 12, wherein the internal combustion engine configured to supply fluid to the first and second cooling passages.

14. An internal combustion engine according to claim 13, further comprising a supply of lubricant for lubricating the internal combustion engine, wherein the internal combustion engine is configured to supply lubricant from the internal combustion engine to the first and second cooling passages and to the bearing section of the turbocharger.

15. An internal combustion engine according to claim 13 or claim 14, further comprising a closed crankcase ventilation circuit configured to recirculate crankcase gas of the internal combustion engine to the compressor.

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