Patent Application
20160265379
The present disclosure relates generally to a turbocharger, and more particularly, to a turbocharger with a turbine shroud.
Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines employ turbochargers to deliver compressed air for combustion in the engine. A turbocharger compresses air flowing into the engine, helping to force more air into the combustion chambers of the engine. The increased supply of air allows increased fuel combustion in the combustion chambers of the engine, resulting in increased power output from the engine.
A typical turbocharger includes a shaft, a turbine wheel attached to one end of the shaft, a compressor impeller connected to the other end of the shaft, and bearings to support the shaft. Often a turbine housing surrounds the turbine wheel and a separate compressor housing surrounds the compressor impeller. In addition, the turbocharger may include a bearing housing that surrounds the bearings and includes features that help prevent leakage of bearing lubrication oil into the turbine housing or the compressor housing. The turbine housing, the compressor housing, and the bearing housing are attached to each other via fasteners or other clamping mechanisms.
Hot exhaust from the engine flows through the turbine housing and expands over the turbine wheel, rotating the turbine wheel and the shaft connected to the turbine wheel. The shaft in turn rotates the compressor impeller. Relatively cool air from the ambient flows through the compressor housing where the compressor impeller compresses the air and drives the compressed air into the combustion chambers of the engine.
Because the exhaust from the engine is significantly hotter than the ambient air, the turbine wheel and the turbine housing can experience temperatures significantly higher than the other components of the turbocharger, such as the bearing housing and the compressor housing. Also, the turbine wheel may have a relatively smaller mass and may be symmetric, whereas the turbine housing may have a relatively larger mass and may be asymmetric. As a result, the turbine housing may increase in temperature more slowly than the turbine wheel, thereby resulting in thermal lag compared to the turbine wheel. Also, both the turbine housing and the turbine wheel may experience thermal expansion, but, because the turbine housing may be asymmetric, the turbine housing may expand asymmetrically. Asymmetric expansion may cause a tip clearance between the turbine wheel and the turbine housing to vary around the turbine wheel so that there may be relatively larger tip clearances in some locations around the turbine wheel, which may reduce the efficiency of the turbocharger.
One attempt to address some of the problems described above is disclosed in U.S. Pat. No. 8,322,978 issued to Dilovski et al. on Dec. 4, 2012 (“the '978 patent”). In particular, the '978 patent discloses a turbocharger including a guide vane cage clamped between a turbine housing and a bearing housing of the turbocharger without fixedly connecting the guide vane cage to either one of the two housings. The guide vane cage may be directly exposed to hot exhaust gases and may be subject to thermal expansion. An axial gap may be formed between the guide vane cage and the turbine housing so that the hot exhaust gas may flow around the guide vane cage, which may allow the guide vane cage to be heated generally uniformly, which may reduce the temperature gradient in the guide vane cage.
Although the turbocharger disclosed in the '978 patent attempts to reduce the temperature gradient in the guide vane cage surrounding the turbine wheel, the disclosed turbocharger may still be less than optimal. For example, the geometry of the turbine wheel and the guide vane cage may not provide tip clearances that are sufficiently small enough to achieve efficient turbocharger performance. Also, the clamping of the guide vane cage between the turbine housing and the bearing housing may not sufficiently isolate the guide vane cage from the turbine housing and may not allow the guide vane cage to respond fast enough to temperature changes, which may cause the blades of the turbine wheel to expand and rub against the guide vane cage.
The turbocharger of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.
In one aspect, the present disclosure is directed to a turbine assembly including a turbine housing and a turbine wheel disposed within the turbine housing. The turbine wheel includes a first end opposite a second end and a rotational axis extending between the first end and the second end. The turbine wheel also includes a plurality of blades. The turbine assembly includes a turbine shroud disposed between the turbine housing and the turbine wheel along a radial direction. The turbine shroud is separate from the turbine housing. The turbine shroud includes an annular portion extending generally in an axial direction with respect to the rotational axis, and at least a portion of the plurality of blades is disposed in at least a portion of the annular portion. The turbine shroud also includes a plate portion intersecting the annular portion to form a convex curved surface. Each of the plurality of blades of the turbine wheel includes a leading edge and a tip portion. Each leading edge is angled with respect to the rotational axis, and each tip portion forms a concave portion that curves around the curved surface of the turbine shroud.
In another aspect, the present disclosure is directed to a turbocharger including a compressor housing having a compressor wheel and a turbine housing having a turbine wheel. The turbine wheel includes a first end opposite a second end and a rotational axis extending between the first end and the second end. The turbocharger also includes a shaft attached at a first end to the compressor wheel and attached at a second end to the turbine wheel. The turbocharger further includes a bearing housing connecting the compressor housing to the turbine housing, and a turbine shroud disposed between the turbine housing and the turbine wheel along a radial direction. The turbine shroud is separate from the turbine housing. The turbocharger also includes a heat shield radially attached to the bearing housing by a plurality of pins extending along the radial direction, and the heat shield is disposed between the bearing housing and the turbine wheel.
In another aspect, the present disclosure is directed to a turbine assembly including a turbine housing and a turbine wheel disposed within the turbine housing. The turbine wheel includes a first end opposite a second end and a rotational axis extending between the first end and the second end. The turbine wheel also includes a plurality of blades. The turbine assembly includes a turbine shroud disposed between the turbine housing and the turbine wheel along a radial direction. The turbine shroud is separate from the turbine housing. The turbine shroud includes an annular portion extending generally in an axial direction with respect to the rotational axis. At least a portion of the plurality of blades is disposed in at least a portion of the annular portion. The turbine shroud also includes a nozzle portion connected to an end of the annular portion. The nozzle portion includes a plurality of nozzle vanes configured to receive a flow of exhaust from the turbine housing. The turbine shroud is formed integrally as a single-piece component.
Reference will now be made in detail to exemplary embodiments, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The compressor assembly 12 may include a fixed geometry compressor impeller or wheel 20 disposed in a compressor housing 22. The compressor wheel 20 and the compressor housing 22 may be disposed around a rotational axis 18 of the shaft 16. The compressor wheel 20 may be attached to the shaft 16 and configured to compress air received at an ambient pressure level before the air enters the engine for combustion. Air may enter the compressor housing 22 via a compressor inlet 24 and exit the compressor housing 22 via a compressor outlet 26. As air moves through the compressor assembly 12, the compressor wheel 20 may force compressed air into the engine.
Bearings 30 may support the shaft 16. The bearings 30 may be disposed in a bearing housing 32. Although
The turbine assembly 14 may include a turbine wheel 40, a turbine housing 80, a turbine shroud 110, and a heat shield 140. The turbine wheel 40 may be attached to the shaft 16 and may be disposed in the turbine housing 80. The shaft 16 may extend from the compressor housing 22 to the turbine housing 80, and the bearing housing 32 may connect the compressor housing 22 to the turbine housing 80. The turbine wheel 40 and the turbine housing 80 may be disposed around the rotational axis 18 of the shaft 16.
The turbine wheel 40 may rotate about a rotational axis 42, which may be collinear with the rotational axis 18 of the shaft 16. The turbine wheel 40 may include a first end 44, a second end 46 located opposite the first end 44, and the rotational axis 42 may extend between the first end 44 and the second end 46. An end of the shaft 16 may attach to the second end 46 of the turbine wheel 40. The shaft 16 may extend through the bearing housing 32 to connect to the compressor wheel 20 and the turbine wheel 40 at opposite ends of the shaft 16. The turbine wheel 40 may include a nose 48 located at the first end 44, a back wall 50 located at the second end 46, and a hub 52 extending along the rotational axis 42 between the nose 48 and the back wall 50. A plurality of blades 60 of the turbine wheel 40 may be disposed around the hub 52.
In the embodiment shown in
As shown in
The turbine housing 80 may be asymmetric with respect to the rotational axis 42 of the turbine wheel 40. The turbine housing 80 may include at least one volute 86 that receives a flow of exhaust from the engine via the turbine inlet 82. The turbine housing 80 shown in
The inner surface of the turbine housing 80 may include one or more surfaces that are configured to receive and align with outer surfaces of the turbine shroud 110. For example, the inner surface of the turbine housing 80 may include a stepped surface 90 that corresponds to the outer surface of the turbine shroud 110, as described below. In an embodiment and as shown in
The turbine shroud 110 may be disposed between the turbine housing 80 and the turbine wheel 40 along the radial direction. The turbine shroud 110 may be separate from the turbine housing 80 such that a gap 106 may be formed between at least a portion of the turbine shroud 110 and the turbine housing 80. As shown in
As shown in
The nozzle portion 114 may include a plate portion 116 connected to an end of the annular portion 112. The plate portion 116 may extend generally in the radial direction and may be generally ring-like, as shown in
As shown in
The channel 88 in the turbine housing 80 may fluidly connect the volute 86 in the turbine housing 80 to the nozzle vanes 118. As shown in
Alternatively, the nozzle portion 114 may be omitted from the turbine shroud 110. The turbine shroud 110 may include the plate portion 116 connected to a plurality of struts or spacer elements, rather than the nozzle vanes 118, and one or more of the struts or spacer elements may attach the plate portion 116 to the heat shield 140.
In an embodiment, the plate portion 116 may intersect the annular portion 112 to form a curved surface 124 facing inward towards the turbine wheel 40. The curved surface 124 may be convex such that the concave portion 72 of each of the blades 60 of the turbine wheel 40 may curve around the curved surface 124, as shown in
The inner surface of the turbine shroud 110 may create a relatively small gap or clearance (tip clearance) with the blades 60 of the turbine wheel 40. The gap may be defined at three or more points along each of the blades 60. For example, the curved surface 124 may include a first point 126 such that a first gap 128 is formed between the first corner 68 of the blades 60 and the first point 126. In an embodiment, the first point 126 may be the closest point on the turbine shroud 110 to the first corner 68. The curved surface 124 may also include a second point 130 such that a second gap 132 is formed between the intermediate point 74 of the tip portion 66 and the second point 130. In an embodiment, the intermediate point 74 may be located at the “knee” of the curve formed by the tip portion 66, e.g., where the slope of the tip portion 66 relative to the rotational axis 42 of the turbine wheel 40 increases from horizontal (e.g., parallel to the rotational axis 42). Alternatively, the intermediate point 74 may be the point on the tip portion 66 that is the midpoint between the first corner 68 and the second corner 70. The second point 130 may be the closest point on the turbine shroud 110 to the intermediate point 74. The second point 130 may be located at the “knee” of the curve formed by the turbine shroud 110, e.g., where the slope of the surface of the turbine shroud 110 relative to the rotational axis 42 of the turbine wheel 40 increases from horizontal (e.g., parallel to the rotational axis 42). The inner surface of the annular portion 112 may include a third point 134 such that a third gap 136 is formed between the second corner 70 of the blades 60 and the third point 134. In an embodiment, the third point 134 may be the closest point on the turbine shroud 110 to the second corner 70. For example, the first gap 128, the second gap 132, and/or the third gap 136 may be less than about 0.020 inches or less than about 0.025 inches during the operation of the turbine assembly 14.
As shown in
In the embodiment shown in
In the embodiment shown in
The disclosed turbine assembly and turbocharger find potential application in relation to any turbocharger. The disclosed turbine assembly and turbocharger find particular applicability in relation to a turbocharger associated with an internal combustion engine. One skilled in the art will recognize, however, that the disclosed turbine assembly and turbocharger could be utilized in relation to other systems that may or may not be associated with a turbocharger associated with an internal combustion engine.
Several advantages over the prior art may be associated with the turbine assembly and turbocharger described above. For example, the turbine shroud 110 may be formed separate from the turbine housing 80. Also, the turbine shroud 110 may have less mass and/or may be formed of thinner walls than the turbine housing 80. As a result, during operation of the turbocharger 10 (e.g., when hot exhaust gases are flowing from the turbine housing 80 through the turbine shroud 110 and around the turbine wheel 40), there may be less thermal mismatch between the turbine shroud 110 and the turbine wheel 40. The turbine shroud 110 may increase in temperature and expand at a rate that may be closer to the temperature increase and rate of expansion of the turbine wheel 40 (e.g., relative to the temperature increase and rate of expansion of the turbine housing 80). The turbine shroud 110 may not experience as much thermal lag as may be experienced by the turbine housing 80. With less thermal mismatch or lag, it may be possible to reduce the tip clearance between the blades 60 of the turbine wheel 40 and the inner surface of the turbine shroud 110, which may result in better efficiency of the turbocharger 10. Also, the turbine shroud 110 may be generally symmetric, which may also reduce the variation in tip clearance around the turbine wheel 40. This may also allow the tip clearance to be reduced and may improve the performance of the turbocharger 10.
In addition, the heat shield 140 may increase in temperature to a higher temperature (e.g., about 700 degrees Celsius) while the bearing housing 32 may remain at a lower temperature (e.g., about 400 degrees Celsius). The temperature differential may cause the heat shield 140 to expand more than the bearing housing 32. The pins 144 radially attaching the heat shield 140 to the bearing housing 32 may allow the heat shield 140 to expand while remaining generally concentric with the bearing housing 32. As a result, the turbine shroud 110, which is attached to the heat shield 140 by the fasteners 122, may remain generally concentric to the bearing housing 32 and the turbine wheel 40. Therefore, there may be less variation in tip clearance around the turbine wheel 40, which may also allow the tip clearance to be reduced and may improve the performance of the turbocharger 10.
The turbine shroud 110 may also be disposed in the turbine housing 80 so that the turbine shroud 110 may expand radially outward away from the turbine wheel 40, which may reduce the likelihood that the turbine wheel 40 may contact the turbine shroud 110 during operation of the turbocharger 10.
Further, rotation of the turbine housing 80 relative to the bearing housing 32, or “clocking” of the turbocharger 10, may be desired to orient the turbine housing 80 relative to the bearing housing 32. The turbine housing 80 may be attached to the bearing housing 32 to allow rotation of the turbine housing 80 around the rotational axis 42 of the turbine wheel 40 relative to the bearing housing 32. The heat shield 140 may be radially attached to the bearing housing 32, and the turbine shroud 110 may be fastened to the heat shield 140 by the fasteners 122. Therefore, the turbine housing 80 may also be rotatable with respect to the heat shield 140 and the turbine shroud 110. Further, the weight of the turbine housing 80 may be isolated from the turbine shroud 110 and may not affect the tip clearance or the centering of the turbine shroud 110.
In addition, the turbine wheel 40 may be a mixed-flow turbine wheel, e.g., the leading edge 62 may be angled with respect to the rotational axis 42. As a result, the turbocharger 10 may provide better efficiency in certain applications.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed turbine assembly and turbocharger. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed turbine assembly and turbocharger. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
