Turbocharger with twin scroll turbine housing

Abstract

A turbocharger has a turbine housing scroll that is radially divided into a first and a second scroll. A nozzle ring disposed in the turbine nozzle has an array of circumferentially spaced first guide vanes and an array of circumferentially spaced second guide vanes. First guide vane passages between the first guide vanes are configured to blow exhaust gas onto turbine blade leading edges. Similarly, the second guide vane passages are configured to blow exhaust gas onto the turbine blade leading edges. The first and second guide vanes are circumferentially staggered relative to each other so that the turbine blade leading edges receive exhaust gas from the first and second vane passages in an interlaced manner around the circumference of the turbine wheel.

Description

Technical Field

[0001] The present disclosure relates to turbochargers wherein the turbine of the turbocharger is driven by exhaust gas from a reciprocating engine. The present invention more particularly relates to a turbine housing partitioned into a plurality of substantially separate sections each fed by a separate exhaust system. Background Art

[0002] An exhaust-driven turbocharger is a device that is used in conjunction with an internal combustion engine to increase the power output of the engine by compressing air delivered to the air intake of the engine for mixing with fuel and burning in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and there is also another center housing connected between the turbine housing and the compressor housing for accommodating the bearings of the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle leading from the chamber to the turbine wheel. Exhaust gas flows from the chamber through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. Thus, the turbine extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through the inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

[0003] In multi-piston reciprocating engines, it is known to design the exhaust system in a manner that exploits the pressure pulses that occur in the exhaust flow. In particular, it is known to employ so-called "pulse separation," in which the cylinders of the engine are divided into a plurality of groups, and the pulses from each cylinder group are substantially isolated from those of the other groups by having separate exhaust passages for each group. To fully exploit pulse separation, it is desirable to minimize the communication or "cross talk" between the separate cylinder groups. Thus, in the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way into the turbine of the turbocharger. Thus, the turbine housing into which the exhaust gas is fed is typically divided into a plurality of substantially separate components.

[0004] There are two basic ways to partition a turbine housing: (1) sectoral partitioning, and (2) meridian partitioning. In a sectoral partitioned turbine housing, a generally annular chamber is divided into angular sectors, each of which occupies only a portion of the circumference, so that the passages are successive to one another in the circumferential direction, as described, for example, in U.S. Pat. No. 6,260,358. Figure 2 The sector division of the turbine housing is advantageous from a flow separation point of view, but out-of-phase exhaust pulses from the two sectors may induce undesirable turbocharger shaft motions.

[0005] In a meridionally divided turbine housing, the scroll or chamber surrounding the turbine wheel and into which the exhaust gas is fed is divided into a plurality of scrolls successive to one another in the axial direction, each scroll occupying substantially the entire circumference, such as that of U.S. Pat. No. 4,027,994. Figure 4 Meridian separation of the turbine housing is advantageous from a shaft motion point of view, but the exhaust flow from each scroll does not impinge on the full axial width of the turbine blade leading edge, which negatively affects turbine efficiency due to mixing losses.

[0006] The present disclosure relates to a turbocharger having a turbine housing of a radially split type. Summary of the invention

[0007] The present disclosure describes embodiments of a turbocharger having meridionally separated scrolls, but wherein each scroll blows exhaust gas across the entire axial width of the turbine wheel.

[0008] According to an embodiment of the invention described and illustrated herein, a turbocharger comprises:

[0009] a compressor wheel mounted within the compressor housing;

[0010] a turbine wheel mounted within a turbine housing;

[0011] The turbine housing defines a meridionally divided scroll including first and second scrolls for receiving separate exhaust gas flows, each of the first and second scrolls extending around substantially the entire circumference of the turbine housing, the second scroll following the first scroll in the axial direction of the turbocharger;

[0012] the turbine housing defining a nozzle for directing exhaust gas from the meridianally divided volute onto the turbine wheel;

[0013] a turbine wheel including a hub and a plurality of turbine blades coupled to the hub, each turbine blade defining a blade leading edge; and

[0014] a nozzle ring disposed in the nozzle, the nozzle ring comprising a first ring of first vanes circumferentially spaced about a circumference of the nozzle ring and a second ring of second vanes circumferentially spaced about the circumference of the nozzle ring, the first ring defining first vane passages between circumferentially consecutive first vanes, the second ring defining second vane passages between circumferentially consecutive second vanes, wherein the first vane passages are positioned to receive exhaust gas only from the first scroll, and wherein respective outlets of the first vane passages direct a plurality of first exhaust gas jets over a leading edge of a turbine blade, wherein the second vane passages are positioned to receive exhaust gas only from the second scroll, and wherein respective outlets of the second vane passages direct a plurality of second exhaust gas jets over a leading edge of a turbine blade, and wherein the first vane passages are circumferentially staggered relative to the second vane passages such that the first exhaust gas jets are interleaved with the second exhaust gas jets around the circumference of the turbine wheel.

[0015] Since each of the two scrolls blows exhaust gas on the turbine wheel all the way around its circumference, and the jets from the first and second guide vane passages interweave around the circumference, the present invention can alleviate the shaft motion and mixing loss problems that may affect some prior art turbines of the sectoral and meridian separation types. The present invention can maintain good flow isolation between the two exhaust gas flows all the way to the turbine wheel, thereby taking full advantage of the use and separation of the exhaust manifold pressure pulses.

[0016] In some embodiments, there may be symmetry between the first and second guide vane passages in that they have approximately equal respective flow areas. However, in other embodiments, the flow area of ​​the first guide vane passage may be different than the flow area of ​​the second guide vane passage, such that one scroll contributes a greater portion of the total exhaust flow than the other scroll, while the volumes of the first and second scrolls may optionally be equal.

[0017] In some embodiments, the first guide vane passage may be configured such that each first exhaust jet impinges over the entire extent of the turbine blade leading edge, and similarly, the second guide vane passage may be configured such that each second exhaust jet impinges over the entire extent of the turbine blade leading edge. In other embodiments, each of the first and second guide vane passages may be configured such that the first and second exhaust jets impinge less than the entire extent of the leading edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Having thus generally described the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0019] Figure 1 is an axial cross-sectional view of a turbocharger according to an embodiment of the present invention;

[0020] Figure 2 is an axial cross-sectional view of a turbine housing, a turbine wheel, and a nozzle ring according to an embodiment of the present invention;

[0021] Figure 3 It is along Figure 2 A cross-sectional view taken along line 3-3 in FIG.

[0022] Figure 4 It is along Figure 2 A cross-sectional view of line 4-4 in FIG.

[0023] Figure 5 is an isometric view of a nozzle ring and a turbine wheel according to an embodiment of the present invention;

[0024] Figure 6 is similar to Figure 5 view, but with the turbine wheel removed;

[0025] Figure 7 is similar to Figure 6 , but in which the nozzle ring has been sectioned along an r-θ plane (i.e., a constant z plane) passing through the second ring;

[0026] Figure 8 Similar to Figure 7 , the nozzle ring has been sectioned along an r-θ plane passing through the first ring; and

[0027] Fig. 9 is a diagrammatic view of a leading edge portion of a turbine wheel in an expanded view showing intertwining first and second exhaust jets. DETAILED DESCRIPTION

[0028] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the invention are shown. In fact, these inventions can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided so that the present disclosure will satisfy applicable legal requirements. Throughout the text, like reference numerals refer to like elements. References herein to "radial", "circumferential" and "axial" (or equivalently, to cylindrical coordinates r, θ, z, respectively) are relative to the turbocharger axis of rotation, with the axial direction being along or parallel to the axis of rotation, the radial direction extending perpendicularly from the axis of rotation, and the circumferential direction surrounding the axis of rotation.

[0029] A turbocharger 10 according to an embodiment of the present invention is shown in FIG. Figure 1The turbocharger includes a compressor wheel or impeller 14 housed in a compressor housing 16 and mounted on one end of a rotatable shaft 18. The shaft is supported in a bearing 19 mounted in a center housing 20 of the turbocharger. The shaft 18 is rotated by a turbine wheel 22 mounted on the other end of the shaft 18 from the compressor wheel, thereby rotatably driving the compressor wheel, which compresses air drawn in through the compressor inlet and delivers the compressed air to a volute 21 which collects the compressed air for supply to the intake of an internal combustion engine (not shown) for enhancing the performance of the engine.

[0030] The turbocharger also includes a turbine housing 24 that houses the turbine wheel 22. As previously described, in a reciprocating internal combustion engine having a plurality of cylinders, it is advantageous to design the exhaust system in a manner that exploits the pressure pulses that occur in the exhaust stream discharged from the cylinders. In particular, it is advantageous to employ so-called "pulse separation," in which the cylinders of the engine are divided into a plurality of groups, and the pulses from each cylinder group are substantially isolated from those of the other groups by having separate exhaust passages for each group. To fully exploit pulse separation, it is desirable to minimize the communication or "crosstalk" between the separate cylinder groups. In the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way into the turbine of the turbocharger. For this purpose, the turbine housing typically has a separated scroll, including two separate scrolls that each receive a separate exhaust stream.

[0031] Therefore, if Figure 1 As shown in FIG. 2 , the turbine housing 24 defines a meridionally divided scroll member, including a first scroll member 26a and a second scroll member 26b, which are separated from each other by a partition wall 27. The second scroll member is connected to the first scroll member in the axial direction of the turbocharger, and each scroll member receives exhaust gas via a separate exhaust inlet defined by the turbine housing. According to the present invention, the two exhaust gas flows are isolated from each other all the way to the turbine wheel 22 via a nozzle ring 30 that guides the two exhaust gas flows to the turbine wheel respectively. The nozzle ring is arranged in the turbine housing 24 adjacent to the center housing 20.

[0032] refer to Figure 2-8, the nozzle ring 30 defines a first ring 40 of first vanes 42 circumferentially spaced about the circumference of the nozzle ring, and a second ring 50 of second vanes 52 circumferentially spaced about the circumference of the nozzle ring. The first ring 40 defines first vane passages 44 between circumferentially consecutive first vanes 42. Similarly, the second ring 50 defines second vane passages 54 between circumferentially consecutive second vanes 52. The first vane passages 44 are circumferentially staggered relative to the second vane passages 54. In other words, the second vane array is circumferentially "clocked" relative to the first vane array about the nozzle ring axis by an angular amount that is less than the angular spacing between adjacent first vanes. In the illustrated embodiment, the second vane passages are circumferentially staggered with the first vane passages in the circumferential direction by approximately half of the circumferential spacing between the leading edge of one first vane 42 and the leading edge of the next first vane 42. Fluid isolation of the two sets of guide vane passages 44 and 54 is achieved by a separator 48 comprising a generally annular wall, with the end of the first guide vane 42 coupled to one face of the separator 48 and the end of the second guide vane 52 coupled to the opposite face of the separator.

[0033] The nozzle ring 30 may include a first end wall 46 and a second end wall 56. The first end wall 46 is axially spaced from the separator 48, and the end of the first guide vane 42 opposite the separator is coupled to the first end wall. The second end wall 56 is axially spaced on the other side of the separator, and the end of the second guide vane 52 opposite the separator is coupled to the second end wall. To prevent the nozzle ring from rotating relative to the turbine casing 24, the nozzle ring may be provided with an anti-rotation feature or multiple such features. In one non-limiting embodiment, the anti-rotation feature may include one or more pins 32. The nozzle ring may define a receiver 58 in the second end wall 56 (or alternatively, in the first end wall 46) that is aligned with a corresponding receiver in the turbine casing 24, and each pair of aligned receivers is maintained in alignment by one of the anti-rotation pins 32 ( Figure 2 ). In the illustrated embodiment, there are three such anti-rotation pins spaced circumferentially around the circumference of the nozzle ring. Other types of anti-rotation features are possible in the practice of the present invention, examples of which include (but are not limited to) radially oriented pins that engage in holes or slots in the turbine housing, integral features (e.g., protrusions) formed on the nozzle ring for engaging corresponding slots or indentations in the turbine housing, and the like.

[0034] The radially innermost end of the partition wall 27 of the turbine housing 24 is adjacent to the radial outer periphery of the nozzle ring 30, such as Figure 2The interface between the dividing wall and the nozzle ring may be sealed with a seal (e.g., an O-ring or any other suitable type of seal). Alternatively, however, in certain circumstances it may be desirable to have a defined gap between the dividing wall and the nozzle ring, the size of the gap being selected to adjust the degree of fluid isolation between the two exhaust gas flows.

[0035] like Figure 2 and Figure 5 As best seen in FIG. 2 , the turbine wheel 22 includes a hub 22h to which a plurality of turbine blades 23 are attached. Each turbine blade 23 has a blade leading edge BLE. The blade leading edge is the first portion of the blade to be struck by the exhaust gas jets emanating from the guide vane passages 44 and 54. Figure 2 As shown in , the first guide vane passage 44 is positioned to receive exhaust gas only from the first scroll 26a, and the outlet of each first guide vane passage 44 directs the first exhaust gas jet onto the turbine blade leading edge BLE. Similarly, the second guide vane passage 54 is positioned to receive exhaust gas only from the second scroll 26b, and the outlet of each second guide vane passage 54 directs the second exhaust gas jet onto the turbine blade leading edge. In the illustrated embodiment, each of the first and second exhaust gas jets impinges on the entire width W of the turbine blade leading edge.

[0036] refer to Fig. 9 Due to the circumferential offset between the two sets of guide vanes 42 and 52, the turbine blade leading edge BLE receives the first and second exhaust jets J1 and J2 from the first and second blade passages 44 and 54, respectively, in an interlaced manner around the circumference of the turbine wheel. That is, one circumferential sector of the wheel receives the first exhaust jet J1 from the first guide vane passage, the adjacent circumferential sector receives the second exhaust jet J2 from the second guide vane passage, the next circumferential sector receives the first exhaust jet J1 from the next adjacent first guide vane passage, and so on, in an alternating or interlaced manner around the entire circumference of the wheel.

[0037] As previously described, nozzle rings according to embodiments of the present invention are able to mitigate some of the disadvantages of both the prior art meridional-separated and sector-separated turbine housing designs. For a sector-separated turbine housing, out-of-phase pulses directed toward the turbine wheel from two 180-degree sectors can induce undesirable turbocharger shaft motion. In contrast, the nozzle ring of the present invention evenly distributes the out-of-phase pulses around the circumference of the turbine wheel, thereby often reducing or eliminating this excessive shaft motion. For a meridional-separated turbine housing, since each vortex feeds the exhaust gas only to about half of the width of the leading edge of the turbine blade, significant mixing losses may occur, thereby adversely affecting turbine efficiency. The nozzle ring according to an embodiment of the present invention can mitigate both the shaft motion problem and the mixing loss problem because the two vortexes feed the exhaust gas alternately around the entire circumference (i.e., in an interlaced manner) (and in some embodiments, the exhaust gas can also be blown over the entire range of the leading edge of the turbine blade).

[0038] The present invention provides the ability to control the flow split between the two scroll members. For example, by forming the guide vane passage of one scroll member to be smaller than the guide vane passage of the other scroll member, an uneven or asymmetric flow split can be achieved. In this case, it may be advantageous to make the scroll members have equal volumes.

[0039] The shapes of the inlet and outlet sides of the guide vane channels 44 and 54 can be selected by the designer. In some embodiments, the guide vane channel outlet can be roughly rectangular; in other embodiments, it can be oval. The inlet of a given guide vane channel does not necessarily have to have a shape similar to the shape of the outlet of the channel. For example, the guide vane channel inlet can be rectangular, and the outlet can be circular or oval, or vice versa. In the above case where the guide vane channel of one scroll is smaller than the guide vane channel of another scroll, the shape of the guide vane channel outlet can be different between the two scrolls. As a non-limiting example, the guide vane channel outlet of one scroll can be rectangular, and the guide vane channel outlet of another scroll can be oval and smaller in flow area than the rectangular outlet.

[0040] In the illustrated embodiment, the second guide vane passages 54 are circumferentially staggered relative to the first guide vane passages 44 such that there is no circumferential overlap (eg, between a given second exhaust jet J2 and an adjacent first exhaust jet J1) . Fig. 9). However, the invention is not limited in this sense, and in other (not shown) embodiments, the guide vanes may be configured such that there is some circumferential overlap between the respective first exhaust jets J1 and second exhaust jets J2. Additionally, in other (not shown) embodiments, each of the first and second guide vane rings may blow exhaust gas less than the entire width W or extent of the turbine blade leading edge, and in this case, there may be overlap in the axial direction (and optionally, also in the circumferential direction) between the first and second exhaust jets.

[0041] exist Figure 5-8 In the embodiment of the invention shown in , the nozzle ring 30 comprises two end walls 46 and 56. However, alternatively, the end walls 46 and 56 may be omitted, so that the nozzle ring comprises only a separator 48 and two sets of guide vanes 42 and 52 coupled thereto. In this case, the function of the end walls may be performed by parts of the turbine housing 24.

[0042] Many modifications and other embodiments of the inventions set forth herein will come to mind to those skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing description and the associated drawings. For example, in the illustrated embodiment, the turbine is of the radial inflow type, but the invention is also applicable to other turbine types, such as mixed flow and axial inflow turbines. Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A turbocharger, comprising: a compressor wheel mounted within the compressor housing; a turbine wheel mounted within a turbine housing; The turbine housing defines a meridionally divided scroll including first and second scrolls for receiving separate exhaust gas flows, each of the first and second scrolls extending around substantially the entire circumference of the turbine housing, the second scroll following the first scroll in the axial direction of the turbocharger; the turbine housing defining a nozzle for directing exhaust gas from the meridianally divided volute onto the turbine wheel; as well as a nozzle ring disposed in the nozzle, the nozzle ring comprising a first ring of first vanes circumferentially spaced about a circumference of the nozzle ring and a second ring of second vanes circumferentially spaced about the circumference of the nozzle ring, the first ring defining first vane passages between circumferentially consecutive first vanes, the second ring defining second vane passages between circumferentially consecutive second vanes, wherein the first vane passages are positioned to receive exhaust gas only from the first scroll, and wherein respective outlets of the first vane passages direct a plurality of first exhaust gas jets over a leading edge of a turbine blade, wherein the second vane passages are positioned to receive exhaust gas only from the second scroll, and wherein respective outlets of the second vane passages direct a plurality of second exhaust gas jets over a leading edge of a turbine blade, and wherein the first vanes are equal in number to the second vanes, and the first vane passages are circumferentially staggered relative to the second vane passages such that the first exhaust gas jets are interleaved with the second exhaust gas jets around the circumference of the turbine wheel.

2. The turbocharger according to claim 1, wherein: The turbine housing includes a partition wall separating the first and second scroll members from each other, and wherein a radially inner end of the partition wall is adjacent to a radially outer periphery of the nozzle ring.

3. The turbocharger according to claim 1, wherein: The nozzle ring includes a separator fluidly isolating the first and second vane passages from each other, an end of the first vane is coupled to one side of the separator, and an end of the second vane is coupled to an opposite side of the separator.

4. The turbocharger according to claim 3, wherein: The nozzle ring includes a first end wall and a second end wall, wherein the first end wall is spaced apart from the one side of the separator and an end of the first guide vane opposite the separator is coupled to the first end wall, and wherein the second end wall is spaced apart on the opposite side of the separator and an end of the second guide vane opposite the separator is coupled to the second end wall. 5 . The turbocharger of claim 1 , further comprising an anti-rotation feature to prevent the nozzle ring from rotating relative to the turbine housing.

6. The turbocharger according to claim 1, wherein: The first scroll member and the second scroll member have equal volumes.

7. The turbocharger according to claim 1, wherein: The first scroll member and the second scroll member have unequal volumes.

8. The turbocharger according to claim 1, wherein: The first guide vane passage is equal in flow area to the second guide vane passage.

9. The turbocharger according to claim 1, wherein: The first guide vane passage is not equal to the second guide vane passage in flow area.

10. The turbocharger according to claim 1, wherein: The first guide vane is configured such that each first exhaust gas jet impinges over the entire axial extent of the turbine blade leading edge, and the second guide vane is configured such that each second exhaust gas jet impinges over the entire axial extent of the turbine blade leading edge.

11. The turbocharger according to claim 1, wherein: The first guide vane is configured such that each first exhaust jet does not impinge over the entire axial extent of the turbine blade leading edge, and the second guide vane is configured such that each second exhaust jet does not impinge over the entire axial extent of the turbine blade leading edge.

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