Dual volute turbocharger with asymmetric tongue-wheel spacing

Abstract

The present invention relates to a housing (60) for a turbocharger exhaust turbine (32) that includes a first volute (61) and a second volute (62), each terminating in a respective first and second guide tongue (64, 66) and turbine wheel. The asymmetry of the tongues allows for control of pulse amplitudes emitted when turbine wheel blades pass over the respective tongues. Furthermore, durability requirements can be met by increasing the wheel-to-tongue distance of the second guide tongue (66). [Selected Figure] Figure 1

Description

Technical Field

[0001] In a multi-cylinder internal combustion engine in which cylinders are sequentially combusted, exhaust ports for supplying energy to drive a turbine wheel are opened at different times. When an exhaust port is first opened, a gas surge is discharged from the cylinder. This high-energy short-term pulse is very valuable for driving the turbine of an exhaust gas turbocharger. Next, when the exhaust port closes, the pressure in the manifold decreases. In an engine equipped with a single manifold, a high-energy pulse from one cylinder moving under the manifold can meet and combine with a low-pressure wave from another cylinder to remove the pressure pulse. The reduction in the amplitude of this peak pulse pressure reduces the turbine driving efficiency.

[0002] Improved technology for driving a turbine wheel is Pulse Charging (pulse charging) is known. The engine exhaust system is divided into two or more exhaust manifolds, each exhaust manifold is connected to a different set of cylinders, and these independent manifolds are supplied to a turbine housing divided internally. Thereby, at least first and second flow streams induced from different groups of cylinders are kept separated from the cylinder exhaust port to the turbine wheel, and the high-energy pulse in one manifold is not reduced by interaction with the low-pressure wave of another manifold.

[0003] The housing divided inside the dual-volute turbine forms channels, and each channel is terminated by a so-called tongue. It must be considered that this tongue at least partially prevents the optimal flow with respect to the turbine wheel. The tongue hides a part of the turbine wheel and it is not possible to direct the flow directly towards this part of the turbine wheel. In the case of two channels, there are two such tongues that have an adverse effect on the optimal flow with respect to the turbine wheel. Although it might seem desirable to form tongues with elongated tips for aerodynamic purposes, there is a counteracting requirement for a thickness sufficient to ensure a certain level of durability strength.

[0004] Another problem is the pulse Charging The turbocharger turbine wheel is exposed to very unstable aerodynamics, causing significant blade vibration. The main cause of high-cycle fatigue of the turbine wheel of a turbocharger turbine is the aerodynamic blade excitation force.

[0005] Yet another problem is the noise generated by the turbine blades passing through the nozzle vanes. The amplitude of the pulse released when the blades of the turbine wheel pass through the tongue can be converted into noise. This pulse energy can also introduce stress to the tongue. The tongue is a feature of the turbine housing where cracks and breakages due to thermal stress and high-cycle fatigue are likely to occur, and these pressure pulses can introduce additional forces to accelerate the fatigue failure of the tongue.

[0006] International Publication WO2015 / 179353 (BorgWarner) teaches that normally, the tip of the tongue of the first channel is arranged with a circumferential offset of 180° from the tip of the tongue of the second channel, while in the present invention, the risk of blade fatigue failure can be reduced by shortening the circumferential angular offset by at least 5°. However, the problem of nozzle or tongue breakage is not solved, and further improvement of the turbine wheel life is required.

[0007] The object of the present invention is to embody an exhaust gas turbocharger that enables pulses, is compact at the same time, and can be used in passenger cars and commercial vehicles, together with cost-effective production and low-maintenance operation. Charging

Summary of the Invention

[0008] According to the present invention, the above problems are solved by providing a turbocharger having at least first and second separate flow paths and terminating with first and second guide tongues. The gap between the first guide tongue and the turbine wheel is smaller than the gap between the second guide tongue and the turbine wheel. Due to this asymmetry of the tongues, the pulse amplitude released when the blades of the turbine wheel pass through the respective tongues can be controlled.

[0009] The thermodynamic performance of the radial and mixed-flow turbine stages can not only reduce the flow leakage around the turbine wheel, but also utilize more energy peaks from the pulsation of the flow discharged by the engine. Therefore, it increases when the distance between the tongue and the wheel at the first guide tongue becomes smaller. To maximize the thermodynamic performance, the first guide tongue is arranged as close as possible to the turbine wheel.

[0010] To improve the durability of the turbine wheel, the distance between the second guide tongue and the turbine wheel is larger than that of the first guide tongue, thereby preventing a synchronous response or otherwise a sympathetic response in the turbine wheel due to the wheel passing through each tongue and rotating.

[0011] By increasing the distance from the wheel to the tongue only for the second guide tongue, the durability requirements can be met, while the performance of the first volute terminating at the first tongue will not be unduly affected.

[0012] The two tongues of the dual-volute turbine can be used as-cast or machined to their final shape and placement. The distance from the wheel to the tongue of the second tongue can be changed directly from the as-cast shape of the first tongue or through a finishing machining operation.

[0013] Accordingly, the present invention relates to the design of a low-cost turbine flow control device that can maintain exhaust gas velocity and pulse energy. A low-cost turbocharger matches low-flow conditions and provides an optimized turbo (and thus engine) over-response for low flow while supplying the high flow required by the engine under other conditions than low-flow conditions in the same cost-effective turbocharger.

Brief Description of the Drawings

[0014] The present invention is shown by way of example and is not limited to the accompanying drawings, where like reference numerals indicate like parts.

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] Pulse ChargingTurbochargers are well known. U.S. Patent No. 8,621,863 (Kretschmer et al.) shows a schematic view of an internal combustion engine with a turbocharger attached in FIG. 5, the disclosure of which is incorporated herein by reference. In principle, the internal combustion engine can be a diesel, SI or diesel / SI engine; in the illustrated embodiment, it has six cylinders, with a first set of three of these cylinders combined to form a first cylinder group and a second set of three cylinders combined to form a second cylinder group. Two exhaust gas lines are assigned to each cylinder group, with the first exhaust gas line connected to the first spiral passage of a turbocharger designed as a partial volute via a suitable manifold, while the second exhaust gas line is coupled to a second spiral passage designed as a full volute.

[0016] FIG. 1 of the present application is modified from FIG. 2 of U.S. Patent Application Publication No. 2016 / 0025044, the disclosure of which is incorporated herein by reference. FIG. 1 shows an overview of the exhaust gas flow to the exhaust turbine 32 of a turbocharger. The internal combustion engine 12 system includes an intake passage 18 and an exhaust manifold 20. The intake passage 18 is in fluid communication with the combustion chamber 16 to supply intake air to the combustion chamber 16. The exhaust manifold 20 is in fluid communication with the combustion chamber 16 to receive exhaust gas that is discharged outside the combustion chamber 16 through an exhaust port.

[0017] The exhaust flows from cylinders #1, #2, and #3 of the combustion chamber 16 are physically separated from the exhaust flows from cylinders #4, #5, and #6 of the combustion chamber 16. In particular, the exhaust gases from cylinders #1, #2, and #3 of the combustion chamber 16 flow into the first exhaust pipe 21, while the exhaust gases from cylinders #4, #5, and #6 of the combustion chamber 16 flow into the second exhaust pipe 22. During operation of the engine 12, the exhaust gas pulses P1 - P6 generated when the exhaust valves open and close propagate from cylinders #1, #2, #3, #4, #5, and #6, respectively. Exhaust pulse interference typically occurs when an exhaust gas pulse from one cylinder meets a low - pressure wave from another cylinder. As described above, by separating the exhaust gases from cylinders #1, #2, #3, #4, #5, and #6 into the first and second exhaust pipes 21 and 22, the exhaust turbine 32 can efficiently utilize the exhaust scavenging technique, thereby improving the performance of the turbine system and reducing turbo lag.

[0018] The exhaust turbine 32 of the turbocharger has a turbine housing 60 having a first volute 61, a second volute 62, and a turbine wheel receiving bore 63 (also known as the base circle). The first volute 61 has a first volute exhaust gas inlet 61a having a cross-sectional area A1. Here, the first volute exhaust gas inlet 61a receives a stream of mixed exhaust gas from cylinders #1, #2, and #3. The first volute 61 has a first exhaust gas outlet 61b having a cross-sectional area A1' at the starting portion of the first exhaust gas outlet 61b, which, as shown in FIG. 1, extends in the counterclockwise direction from the tip or free end of the first tongue 64 to the tip or free end of the second tongue 66. The second volute 62 has a second exhaust gas inlet 62a having a cross-sectional area A2. Here, the second exhaust gas inlet 62a receives a stream of mixed exhaust gas from cylinders #4, #5, and #6. The second volute 62 has a second exhaust gas outlet 62b having a cross-sectional area A2' at the starting portion of the second exhaust gas outlet 62b, which, as shown in FIG. 1, extends circumferentially in the counterclockwise direction from the tip of the second tongue 66 to the tip of the first tongue 64. The cross-sectional areas A1 and A2 of the first and second volutes 61, 62 can be made substantially the same. Alternatively, the cross-sectional area A2 of the second volute 62 can be made smaller than the cross-sectional area A1 of the first volute 61.

[0019] As shown diagrammatically in FIG. 1, the first exhaust gas outlet 61b is opened circumferentially along 180 degrees of the turbine receiving bore 63, while the second exhaust gas outlet 62b is opened circumferentially along the remaining 180 degrees of the turbine receiving bore 63.

[0020] According to the present invention, the turbocharger is provided with at least first and second separate flow paths, which terminate at the first and second guide tongues. The gap between the first guide tongue and the turbine wheel is smaller than the gap between the second guide tongue and the turbine wheel. This asymmetry of the tongues makes it possible to control the pulse amplitude released when the blades of the turbine wheel pass through the respective tongues.

[0021] The turbine housing consists of a plurality (two or more) of volutes 61, 62 configured such that the outlet of each volute is arranged around the base circle of the turbine housing. The volutes cumulatively send the exhaust to the outer periphery 2 of the turbine wheel 1 as shown in FIG. 3.

[0022] A common way to define the tongue gap is the ratio of the closest point wheel - tongue gap divided by the diameter of the wheel (measured at the radially outer tip of the turbine wheel). For example, a 3 mm gap divided by a 53 mm wheel diameter = 3 / 53 = 5.6% or 0.056 as the ratio of the tongue gap (TGR). As the tongue gap increases, the dual - volute pulse effect decreases. The TGR for a larger gap is in the range of 0.15 to 0.04, preferably in the range of 0.1 to 0.05, more preferably in the range of 0. 0 8 to 0.05, most preferably in the range of 0. 0 7 to 0. 0 6 and is selected in this range. The TGR for a closer gap is in the range of 0. 0 8 to 0. 0 1, preferably in the range of 0. 0 7 to 0. 0 2, more preferably in the range of 0. 0 6 to 0. 0 3, most preferably in the range of 0. 0 5 to 0. 0 4 and can be selected in this range. The ratio of the larger TGR to the smaller TGR can be 1.5 to 4, preferably 2 to 3.

[0023] An asymmetric tongue spacing can be used in a turbocharger with a symmetric or asymmetric volute. It can be used in an EGR turbocharger. It can be used in a turbocharger having a variable turbine geometry (VTG). The essential feature of the present invention is the asymmetric tongue-wheel spacing. This can be used in a dual entry turbine, where an actuator is used to selectively control the flow of exhaust gas from the inlet to the second scroll while maintaining such gas flow in the first scroll, as disclosed, for example, in U.S. Patent No. 4,389,845 (Koike). Refer to FIG. 9B where the actuator controls a valve that controls the flow rate into the first or second and first volutes formed by a solid partition wall. The asymmetric tongue spacing can also be used with a radial flow turbine or a "mixed flow" radial / axial turbine (see US2007 / 0180826).

[0024] As an alternative to varying the distance from the tongue to the wheel between the first tongue and the second tongue, it is also possible to vary the nozzle width of the first volute with respect to the second volute.

[0025] This asymmetric method, which includes varying the nozzle width of the first volute from the second volute, enables adjustment of the flow rate between both volutes. This method can be used to equalize the turbine inlet pressures of both cylinder groups. This can be used to prevent the asymmetry found in the design of the cylinder head. For example, in a situation where the nozzle widths of the first volute and the second volute are equal, the turbine inlet pressure can be measured at each volute (and each cylinder pairing). In this embodiment, the pressure flowing into the second volute is below the target for engine operation. The nozzle width of the second volute can be decreased to reduce the flow rate through the second volute and increase the turbine inlet pressure.

[0026] Reducing the flow rate in one volute can be useful for increasing the low-end torque and over-performance potential of a turbine stage. A lower flow rate turbine stage provides more power by the compressor stage at low engine flow rate and engine RPM, enabling more aggressive low end torque and over-actuation.

[0027] This method can be used to create unequal flow between cylinder groups that create unequal turbine inlet pressures across each volute. In a situation where the nozzle width of the first volute and the nozzle width of the second volute are symmetric, the turbine inlet pressure can be measured and confirmed to be equal across each volute (and each cylinder pairing). To drive HP-EGR, the nozzle width of the second volute can be decreased to increase the turbine inlet pressure ahead of the second volute. Increasing the turbine inlet pressure of the second volute allows the turbo / engine system to drive HP-EGR without affecting the pumping loop / VE of the cylinder group of the first volute.

[0028] Thus, the description of the present invention ends.

Claims

1. A turbocharger turbine housing (60) in the form of a spiral casing having at least first and second volutes (61, 62) defining separate flow paths to a turbine wheel bore (63), wherein said turbine wheel bore (63) is adapted to receive a turbine wheel (1) having a turbine wheel outer periphery (2), said flow paths ending in first and second guide tongues (64, 66), and a gap between said first guide tongue (64) and the turbine wheel outer periphery (2) is smaller than a gap between said second guide tongue (66) and the turbine wheel outer periphery (2), wherein a tongue-gap ratio (TGR) of said second guide tongue (66), measured as the wheel-tongue gap at the closest point divided by the diameter of said turbine wheel (1), is selected from the range of 0.15 to 0.04, the TGR of the first guide tongue (64) is selected in the range of 0.08 to 0.01, and a ratio of the larger TGR to the smaller TGR is selected from the range of 1.5 to 4, A turbocharger turbine housing.

2. The turbocharger turbine housing according to claim 1, wherein the TGR of said second guide tongue (66) is selected from the range of 0.1 to 0.

05.

3. The turbocharger turbine housing according to claim 1, wherein the TGR of said second guide tongue (66) is selected from the range of 0.08 to 0.

05.

4. The turbocharger turbine housing according to claim 1, wherein the TGR of said second guide tongue (66) is selected from the range of 0.07 to 0.

06.

5. The turbocharger turbine housing according to claim 1, wherein the TGR of said first guide tongue (64) is selected from the range of 0.07 to 0.

02.

6. The turbocharger turbine housing according to claim 1, wherein the TGR of said first guide tongue (64) is selected from the range of 0.06 to 0.

03.

7. The turbocharger turbine housing according to claim 1, wherein the TGR of said first guide tongue (64) is selected in the range of 0.05 to 0.

04.

8. The turbocharger turbine housing according to claim 1, wherein a ratio of the larger TGR to the smaller TGR is selected from the range of 2 to 3.

9. The turbocharger turbine housing according to claim 1, wherein the first and second volutes are asymmetric.

10. The turbocharger turbine housing according to claim 9, wherein one of the first volute and the second volute is connected to an exhaust gas recirculation line.

11. The turbocharger turbine housing according to claim 1, wherein the turbine housing houses a variable geometry turbine.

12. The turbocharger turbine housing according to claim 1, wherein the first and second guide tongues (64, 66) have first and second tongue tips, and the first guide tongue tip is offset 180° in the circumferential direction from the second guide tongue tip.

13. The turbocharger turbine housing according to claim 1, wherein the first and second guide tongues (64, 66) have first and second tongue tips, and the first guide tongue tip is offset 165° to 177° in the circumferential direction from the second guide tongue tip.

14. A turbocharger comprising a turbine housing (60) in the form of a spiral casing having at least first and second volutes (61, 62) defining individual flow paths to a turbine wheel bore (63), wherein the turbine wheel bore (63) is adapted to accommodate a turbine wheel (1) having a turbine wheel outer periphery (2), the flow paths ending at first and second guide tongues (64, 66), and a gap between the first guide tongue (64) and the turbine wheel outer periphery (2) is smaller than a gap between the second guide tongue (66) and the turbine wheel outer periphery (2), wherein a tongue-gap ratio (TGR) of the second guide tongue (66), measured as the wheel-tongue gap at the closest point divided by the diameter of the turbine wheel (1), is selected from the range of 0.15 to 0.04, the TGR of the first guide tongue (64) is selected in the range of 0.08 to 0.01, and a ratio of the larger TGR to the smaller TGR is selected from the range of 1.5 to 4. Turbocharger.

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