Turbocharger with a meridian-divided turbine housing

Abstract

The turbocharger has a meridionally divided vortex including a first vortex and a second vortex. A partition wall separating the two vortices from each other has an evolving thickness distribution that varies according to the angular position around the axis of rotation of the turbine. In an embodiment, the partition wall has a V-shape, and the angle of the V-shaped partition wall varies from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°. Therefore, the thickness of the partition wall varies accordingly from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°.

Description

Technical Field

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

[0002] An exhaust-driven turbocharger is a device used in conjunction with an internal combustion engine to increase the power output of the engine by compressing air that is 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 containing bearings for 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 that leads 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 draws 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 such a way as to take advantage of the pressure pulsations that occur in the exhaust gas 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 group of cylinders are substantially isolated from the pulses from the other groups by having a separate exhaust passage for each group. In order to best exploit pulse separation, it is desirable to minimize the communication or "crosstalk" between the separate groups of cylinders. Thus, in the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way to the turbine entering the turbocharger. Thus, the turbine housing into which the exhaust gas is fed is typically divided into a plurality of substantially separate sections.

[0004] There are two basic ways to divide the turbine housing: (1) meridian division and (2) sector division. In a meridian-divided turbine housing, the vortex or chamber surrounding the turbine wheel and into which the exhaust gas is fed is divided into a plurality of channels in the meridian plane so that each channel occupies approximately the entire circumference and the channels succeed each other in the axial direction, such as shown in FIG. 4 of U.S. Patent No. 4,027,994.

[0005] In a sectored turbine housing, a substantially annular chamber is divided into angular sectors, each of which occupies only a portion of the circumference, so that the passages succeed each other in the circumferential direction, such as in U.S. Pat. No. 6,260,358. Figure 2 The '358 patent also discloses stationary guide vanes located just radially inward from the chamber and directing flow into the turbine wheel.

[0006] The present disclosure relates to a turbocharger having a meridianally divided turbine housing. Summary of the invention

[0007] The present disclosure describes an embodiment of a turbocharger having a meridian-divided turbine housing. According to an embodiment of the present invention, the turbocharger comprises:

[0008] a compressor including a compressor housing and a compressor impeller mounted in the compressor housing and connected to a rotatable shaft for rotation therewith;

[0009] a turbine including a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith;

[0010] the turbine housing defining a first inlet and a separate second inlet into which separate first and second exhaust gas flows are received, respectively;

[0011] a center housing connected between the compressor housing and the turbine housing and containing bearings for the shaft;

[0012] The turbine housing defines a meridianally divided vortex around the turbine wheel, the first and second inlets are combined with the meridianally divided vortex at positions defined as a 0° angular position relative to a circumferential direction around the turbine wheel, the meridianally divided vortex extending generally from the 0° angular position to a 360° angular position in the circumferential direction, the meridianally divided vortex defining a first vortex receiving a first exhaust gas flow from the first inlet and a separate second vortex receiving a second exhaust gas flow from the second inlet;

[0013] a nozzle opening generally radially inwardly from the meridianally divided vortex path to the turbine wheel; and

[0014] wherein the turbine housing defines a partition wall that meridianally divides the first vortex path from the second vortex path, wherein the partition wall has a thickness T in any axial-radial cross-sectional plane passing through the turbine housing and through the axis of rotation of the turbine impeller, the thickness T being 1 / 200 mm in the cross-sectional plane at a mean radius R of the partition wall. avg The thickness T varies from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°.

[0015] In one embodiment of the invention, the partition wall in the axial-radial cross section has a V-shape with an angle β varying from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Having generally described the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0017] Figure 1 is an axial cross-sectional view of a turbocharger according to one embodiment of the present invention;

[0018] Figure 2 yes Figure 1 A portion of which is enlarged to illustrate in more detail the partition wall according to an embodiment of the present invention; and

[0019] Figure 3 is a schematic depiction of a meridionally divided vortex passage viewed in the axial direction, on which is superimposed a series of axial-radial cross-sectional views through the vortex passage at various angular positions about the turbine wheel axis. DETAILED DESCRIPTION

[0020] The present disclosure will now be described in more detail with reference to the above-mentioned drawings, which depict some but not all embodiments of the invention(s) to which the present disclosure belongs. These inventions may be implemented in various forms, including forms not explicitly described herein, and these inventions should not be construed as being limited to the specific exemplary embodiments described herein. In the following description, similar reference numerals refer to similar elements throughout.

[0021] Figure 1 A turbocharger 10 according to one embodiment of the present invention is illustrated. The turbocharger includes a compressor wheel or impeller 14 disposed 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 17, which collects the compressed air for supply to the intake of an internal combustion engine (not shown) for improving the performance of the engine.

[0022] The turbocharger also includes a turbine housing 24 that houses the turbine wheel 22. As previously noted, in a reciprocating internal combustion engine having a plurality of cylinders, it is advantageous to design the exhaust system in such a way as to exploit the pressure pulsations that occur in the exhaust streams 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 group of cylinders are substantially isolated from the pulses from the other groups by having separate exhaust passages for each group. In order to best exploit pulse separation, it is desirable to minimize the communication or "crosstalk" between the separate groups of cylinders. Thus, in the case of a turbocharged engine, it is advantageous to maintain separate exhaust passages all the way to the turbine that enters the turbocharger. Thus, in an embodiment of the present invention, the turbine housing defines a first inlet 25a for receiving a first exhaust stream from a subset of the engine cylinders and a separate second inlet 25b for receiving a second exhaust stream from another subset of the engine cylinders. The turbine housing also defines a meridionally divided vortex 26 formed as two completely separate first and second vortices 26a and 26b, each of which extends approximately 360 degrees around the turbine wheel 22. The first vortex 26a receives exhaust gas from the first inlet 25a, and the second vortex 26b receives exhaust gas from the second inlet 25b. The exhaust gas from the vortices 26a and 26b is fed into the turbine wheel 22 by the nozzle 28 for driving the turbine wheel, which in turn drives the compressor wheel 14.

[0023] The first and second inlets 25a, 25b are combined with the meridian-divided scroll 26 at a position defined as the 0° angular position relative to the circumferential direction around the turbine wheel. The meridian-divided scroll extends substantially from the 0° angular position to the 360° angular position in the circumferential direction.

[0024] The turbine housing includes a dividing wall 24d which divides the scroll into two separate scrolls. The dividing wall extends substantially 360° around the turbine. The present invention relates to a particular configuration of the dividing wall which has been found to be beneficial in reducing thermal stresses which may cause the dividing wall to crack over time.

[0025] refer to Figure 2 , the partition wall 24d in the illustrated embodiment has a V-shape, which tapers from a relatively large thickness at the radially outer end of the partition wall (also referred to herein as the "root end") to a relatively small thickness at the radially inner end (also referred to herein as the "tip end"). The taper angle or included angle is denoted herein as β. The parameter R is used in this specification. avg , which is defined as the average of the radius of the dividing wall at its root end (from the axis of rotation A of the turbine) and the radius of the dividing wall at its tip end. The dividing wall has the average radius R avg The thickness at is denoted as T, such as Figure 2 The thickness T is measured perpendicular to an imaginary line that bisects the partition wall into two equal half thicknesses. Thus, for example, when the length direction of the partition wall is not completely radially oriented but also has some axial component (e.g. Figure 2 ), the thickness is not measured entirely in the axial direction, but rather along a direction that also has some radial component. Another way of stating this is that the thickness is measured along a line that forms the same angle α with each of the two opposing faces of the dividing wall. It will be appreciated that α and β are related by β = 180° - 2α.

[0026] According to an embodiment of the present invention, the distribution of the thickness T in the circumferential direction is an evolving thickness distribution, which changes from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°. Figure 3 is a schematic view illustrating the evolving thickness distribution. A schematic depiction of a meridionally divided vortex 26 is shown in an axial view. The vortex extends helically around the axis of rotation A of the turbine wheel. The angular position denoted TT is the position where the vortex begins, i.e., the inlet 25a, 25b ( Figure 1 ) is combined with the vortex 26, and this angular position is defined as the 0° angular position. As the vortex advances around the axis of rotation of the turbine impeller, the vortex generally decreases in radius and flow area, and ends approximately at the 360° angular position. Superimposed on the schematic depiction of the vortex is a series of axial-radial cross-sectional views through the vortex, respectively, taken at a series of angular positions around the axis of rotation of the turbine impeller. Therefore, the vortex section is shown at 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°. These are merely representative angular positions that do not have special significance, and the important concept is that the thickness of the partition wall changes from the maximum value at the 0° position to the minimum value at the 360° position. In the illustrated embodiment, there is a V-shaped partition wall, and the angle β decreases accordingly from the 0° position to the 360° position. Therefore, as a non-limiting example, the angle at the 0° position is 20°, and the angle at the 315° position is 5°. These values ​​of the included angle are merely exemplary, and the present invention is not limited to any particular value of the included angle.

[0027] The evolving thickness distribution of the dividing wall according to the present invention can facilitate numerous advantages compared to a dividing wall of constant thickness. One such benefit is improved thermodynamic and thermomechanical properties of the turbine housing. The present invention is particularly beneficial for turbines that operate continuously at high exhaust gas temperatures (e.g., greater than 1000°C) where the turbine housing is constructed of high-grade materials.

[0028] Those skilled in the art will recognize on the basis of this disclosure that modifications and other embodiments of the invention described herein may be made without departing from the inventive concepts described herein. For example, although the illustrated embodiment has a V-shaped partition wall, the invention is not limited to any particular shape, and partition walls of other shapes (e.g., parabolic or hyperbolic shapes) may be used instead. Specific terms used herein are for explanatory purposes rather than for limiting purposes. Therefore, 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.

Claims

1. A turbocharger, comprising: a compressor including a compressor housing and a compressor impeller mounted in the compressor housing and connected to a rotatable shaft for rotation therewith; a turbine including a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith; the turbine housing defining a first inlet and a separate second inlet into which separate first and second exhaust gas flows are received, respectively; a center housing connected between the compressor housing and the turbine housing and containing bearings for the shaft; The turbine housing defines a meridianally divided vortex around the turbine wheel, the first inlet and the second inlet are combined with the meridianally divided vortex at a position defined as a 0° angular position relative to a circumferential direction around the turbine wheel, the meridianally divided vortex extends substantially from the 0° angular position to a 360° angular position in the circumferential direction, the meridianally divided vortex defines a first vortex receiving a first exhaust gas flow from the first inlet and a separate second vortex receiving a second exhaust gas flow from the second inlet; a nozzle opening generally radially inwardly from the meridianally divided vortex path to the turbine wheel; and wherein the turbine housing defines a partition wall that meridianally divides the first vortex path from the second vortex path, wherein the partition wall has a thickness T in any axial-radial cross-sectional plane passing through the turbine housing and through the axis of rotation of the turbine impeller, the thickness T being 1 / 200 mm in the cross-sectional plane at a mean radius R of the partition wall. avg The thickness T varies from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°.

2. The turbocharger according to claim 1, wherein: The partition wall in the axial-radial cross section has an angle β V-shaped, angle β It varies from a maximum value at an angular position of 0° to a minimum value at an angular position of 360°.

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