WO2008137410A2

WO2008137410A2 - Variable turbine geometry turbocharger

Info

Publication number: WO2008137410A2
Application number: PCT/US2008/061875
Authority: WO
Inventors: Paul Anschel; David G. Grabowska
Original assignee: Borgwarner Inc.
Priority date: 2007-05-04
Filing date: 2008-04-29
Publication date: 2008-11-13
Also published as: WO2008137410A3; BRPI0810328A8; CN101663472B; BRPI0810328A2; CN101663472A; US20100104424A1

Abstract

A turbocharger is provided having a turbine wheel (4, 4') with a plurality of extended tips (400, 400'); and a variable turbine geometry assembly in fluid communication with the turbine wheel and having a nozzle ring (6) with a plurality of vanes (7) movably attached thereto. One or more of the extended tips are non-parallel with an edge of one or more of the plurality of vanes. The incidence angle can vary and can be from 1 to 60 degrees. The extended tips can extend into an inlet of the vane space housing the vanes.

Description

VARIABLE TURBINE GEOMETRY TURBOCHARGER

FIELD OF THE INVENTION

[0001] This invention is directed to a turbocharging system for an internal combustion engine and more particularly to variable turbine geometry of a turbocharging system.

BACKGROUND OF THE INVENTION

[0002] Turbochargers are a type of forced induction system. They compress the air flowing into an engine, thus boosting the engine's horsepower without significantly increasing weight. Turbochargers use the exhaust flow from the engine to spin a turbine, which in turn drives an air compressor. Since the turbine spins about 30 times faster than most car engines and it is hooked up to the exhaust, the temperature in the turbine is very high. Additionally, due to the resulting high velocity of flow, turbochargers are subjected to noise and vibration. Such conditions can have a detrimental effect on the components of the turbocharger, particularly on the rotating parts such as the turbine rotor, which can lead to failure of the system.

[0003] Turbochargers are widely used on internal combustion engines and, in the past, have been particularly used with large diesel engines, especially for highway trucks and marine applications. More recently, in addition to use in connection with large diesel engines, turbochargers have become popular for use in connection with smaller, passenger car power plants. The use of a turbocharger in passenger car applications permits selection of a power plant that develops the same amount of horsepower from a smaller, lower mass engine. Using a lower mass engine has the desired effect of decreasing the overall weight of the car, increasing sporty performance, and enhancing fuel economy. Moreover, use of a turbocharger permits more complete combustion of the fuel delivered to the engine, thereby reducing the overall emissions of the engine, which contributes to the highly desirable goal of a cleaner environment. The design and function of turbochargers are described in detail in the prior art, for example, U.S. Pat. Nos. 4,705,463, 5,399,064, and 6,164,931, the disclosures of which are incorporated herein by reference.

[0004] Turbocharger units typically include a turbine operatively connected to the engine exhaust manifold, a compressor operatively connected to the engine air intake manifold, and a shaft connecting the turbine and compressor so that rotation of the turbine wheel causes rotation of the compressor impeller. The turbine is driven to rotate by the exhaust gas flowing in the exhaust manifold. The compressor impeller is driven to rotate by the turbine, and, as it rotates, it increases the air mass flow rate, airflow density and air pressure delivered to the engine cylinders.

[0005] As the use of turbochargers finds greater acceptance in passenger car applications, three design criteria have moved to the forefront. First, the market demands that all components of the power plant of either a passenger car or truck, including the turbocharger, must provide reliable operation for a much longer period than was demanded in the past. That is, while it may have been acceptable in the past to require a major engine overhaul after 80,000-100,000 miles for passenger cars, it is now necessary to design engine components for reliable operation in excess of 200,000 miles of operation. It is now necessary to design engine components in trucks for reliable operation in excess of 1,000,000 miles of operation. This means that extra care must be taken to ensure proper fabrication and cooperation of all supporting devices.

[0006] The second design criterion that has moved to the forefront is that the power plant must meet or exceed very strict requirements in the area of minimized NO_x and particulate matter emissions. Third, with the mass production of turbochargers, it is highly desirable to design a turbocharger that meets the above criteria and is comprised of a minimum number of parts. Further, those parts should be easy to manufacture and easy to assemble, in order to provide a cost effective and reliable turbocharger. Due to space within the engine compartment being scarce, it is also desirable that the overall geometric package or envelope of the turbocharger be minimized. [0007] U.S. Patent No. 6,877,955 to Higashimori shows a turbocharger with a radial flow to the turbine. As shown in FIG. 1, the radial turbine is provided with the rotor blade unit 100 attached to a rotation axis and a scroll 102 having a shape similar to a snail. The rotor blade unit 100 has a hub 101 and a plurality of blades 103 arranged on the hub 101 in a radial direction. A nozzle 104 is interposed between the scroll 102 and a rotating region of the blades 103. A gas flows from the scroll 102 into the nozzle 104, and is accelerated and given rotation force by the nozzle 104 to produce high velocity flow 105, which flows into the direction of the rotor axis. The flow energy of the high velocity flow 105 is converted into the rotation energy by the blades 103 arranged on the hub 101. The blades 103 exhaust the gas 107 having lost the energy into the direction of the rotation axis.

[0008] The Higashimori radial flow system suffers from the drawback of providing only radial flow to the turbine wheel which would not operate efficiently over a wide range of incident angles. The application of only radial flow would cause a drop in efficiency at required engine operating conditions in such a design.

[0009] Thus, there is a need for a turbocharger system, and method of manufacturing such a system, that effectively and efficiently controls application of exhaust gas to the turbine wheel.

SUMMARY OF THE INVENTION

[0010] The exemplary embodiments of the turbocharger drive the turbine wheel utilizing both an axial flow component and a radial flow component of the exhaust gas in a variable turbine geometry (VTG) environment. The mixed flow can be provided by a number of techniques including extended tips of the turbine wheel, secondary flow and leakage flow.

[0011] In one aspect of the invention, a turbocharger is provided having a turbine wheel with a plurality of extended tips; and a variable turbine geometry assembly in fluid communication with the turbine wheel and having a nozzle ring with a plurality of vanes movably attached thereto. One or more of the extended tips are non-parallel with an edge of one or more of the plurality of vanes.

[0012] In another aspect, a the method is provided that involves providing an exhaust gas flow to a turbine wheel of a variable turbine geometry turbocharger, wherein the exhaust gas flow is a mixed flow having both a radial component and an axial component. The mixed flow is formed by at least one of leakage gas, secondary flow and a non-parallel incidence angle of the turbine wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is illustrated by way of example and not limitation in the accompanying drawings in which like reference numbers indicate similar parts, and in which:

[0014] FIG. 1 is a schematic representation of a contemporary turbocharger system with a radial flow to the turbine wheel;

[0015] FIG. 2 is a cross-sectional view of a portion of a turbocharger in accordance with an exemplary embodiment of the invention;

[0016] FIG. 3 is a cross-sectional view of a portion of the turbocharger of FIG. 2;

[0017] FIG. 4 is a cross-sectional view of a portion of a turbocharger in accordance with another exemplary embodiment of the invention;

[0018] FIG. 5 is another cross-sectional view of the turbocharger of FIG. 4; and

[0019] FIG. 6 is a cross-sectional view of portion A of the turbocharger of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiments of the invention are directed to mixed flow along a turbine wheel in a turbocharger for driving a compressor for delivery of a compressed fluid to an internal combustion engine. Aspects of the invention will be explained in connection with a turbine section having a particular turbine wheel geometry, but the detailed description is intended only as exemplary. Exemplary embodiments of the invention are shown in FIGS. 2-6, but the present invention is not limited to the illustrated structure or application.

[0021] Referring to FIGS. 2-3, a turbocharger 1 has a turbine housing 2, a center housing 3 and a compressor housing 3a connected to each other and positioned along an axis of rotation R. The turbine housing 2 has an outer guiding grid of guide vanes 7 over the circumference of a support ring 6. The guide vanes 7 may be pivoted by pivoting shafts 8 inserted into bores of the support ring 6 so that each pair of vanes define nozzles of selectively variable cross-section according to the pivoting position of the vanes 7. This allows for a larger or smaller amount of exhaust gases to be supplied to a turbine rotor 4.

[0022] The exhaust gases are provided to the guide vanes 7 and rotor 4 by a supply channel 9 having an inlet 99. The exhaust gases are discharged through a central short feed pipe 10, and the rotor 4 drives the compressor wheel, impeller or rotor 21 fastened to the shaft 20 of the wheel. The present disclosure also contemplates one or more of turbine housing 2, center housing 3 and compressor housing 3a being integrally formed with each other.

[0023] In order to control the position of the guide vanes 7, an actuation device 11 can be provided having a control housing 12, which controls an actuation movement of a pestle member 14 housed therein, whose axial movement is converted into a rotational movement of an adjustment or control ring 5 situated behind the support ring 6. By this rotational movement, the guide vanes 7 may be displaced from a substantially tangential extreme position into a substantially radially extending extreme position. In this way, a larger or smaller amount of exhaust gases from a combustion motor supplied by the supply channel 9 can be fed to the turbine rotor 4, and discharged through the axial feed pipe 10. [0024] Between the vane support ring 6 and a ring-shaped portion 15 of the turbine housing 2, there can be a relatively small space 13 to permit free movement of the vanes 7. The shape and dimensions of the vane space 13 can be chosen to increase the efficiency of the turbocharger 1, while allowing for thermal expansion due to the hot exhaust gases. To ensure the width of the vane space 13 and the distance of the vane support ring 6 from the opposite housing ring 15, the vane support ring 6 can have spacers 16 formed thereon. Various other turbocharger components can also be used with compressor wheel 21 and turbocharger 1.

[0025] Turbocharger 1 can have a mixed flow turbine wheel 4 formed by a non-zero blade inlet angle, an inlet with a varying radius from the center axis or a combination of both. The exemplary embodiment of FIGS. 2-3, illustrates a turbine wheel 4 with an extended tip 400. The extended tip 400 can be at various angles to the axis of the turbocharger. The mixed flow turbine wheel 4 to benefit from both the radial and axial components of the exhaust gas flow for improved efficiency.

[0026] In a variable turbine geometry turbocharger, the vanes 7 are the predominant factor controlling the relative turbine wheel blade incidence angle. As a result, the turbocharger can be forced to operate over a much wider range of incidence angles. The use of the mixed flow turbine wheel 4 in combination with a variable turbine geometry, (i.e., vanes 7) allows the turbocharger 1 to maintain higher efficiency over a much wider range of incidence angles. In one embodiment, the variable turbine geometry can compensate for any increased inertia due to the turbine wheel geometry by throttling the inlet flow for an improved transient response.

[0027] Referring to FIGS. 4-6, another exemplary embodiment of the mixed flow turbine wheel is shown and generally represented by reference numeral 4'. Turbine wheel 4' has one or more extended tips 400' in proximity to the vanes 7. The extended tips 400' are at an angle, i.e., non- parallel) with each of the trailing edges of the vanes 7. In one embodiment, all of the tips of the turbine wheel 4' are extended tips 400'. In one embodiment, the angle is between 1 and 60 degrees, preferably between 5 and 45 degrees, and more preferably between 10 and 30 degrees. However, the present disclosure contemplates the use of other angles, as well as varying the angles of the extended tips 400'. The extended tips 400' can extend into an inlet of the vane space 13. The inlet is represented generally by broken line 500 in FIG. 5.

[0028] The VTG vanes 7 can control the flow angle into the turbine wheel 4' and can directly affect the magnitude of the tangential and radial flow vectors. In one embodiment, where the mixed flow turbine wheel 4' is less incidence angle sensitive, then the wheel can maintain a higher overall efficiency over a wider range of incidence angles (tangential/radial components) than a traditional radial inflow wheel.

[0029] In another embodiment, a variable turbine geometry turbocharger can have an axial component of the exhaust gas flow generated by leakage flow, secondary flow or a combination of both. This can be used in combination with the extended tips 400 and 400'. In yet another embodiment, the vane 7 can be parallel to the angle of the turbine wheel. In such an embodiment, the VTG vane trailing edge is not radial and has a matching angle to the turbine wheel inlet (or similar angle).

[0030] Although a turbine wheel has been described herein with great detail with respect to an embodiment suitable for the automobile or truck industry, it will be readily apparent that the turbine wheel and the process for production thereof are suitable for use in a number of other applications, such as fuel cell powered vehicles. Although this invention has been described in its preferred form with a certain of particularity with respect to an automotive internal combustion compressor wheel, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of structures and the composition of the combination may be resorted to without departing from the spirit and scope of the invention.

[0031] It is also contemplated by the present disclosure that the features of the turbochargers and/or housings can be used with other types of fluid impelling devices where a particular length of a diffuser is desired. Such other fluid impelling devices include, but are not limited to, the following: superchargers; centrifugal pumps; centrifugal fans; single-stage gas compressors; multistage gas compressors; and other kinds of devices which generally use one or more rotating elements to compress gases and/or induce fluid flow.

[0032] While the invention has been described by reference to a specific embodiment chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A turbocharger ( 1 ) comprising: a turbine wheel (4, 4') having a plurality of extended tips (400, 400'); and a variable turbine geometry assembly in fluid communication with the turbine wheel and having a nozzle ring (6) with a plurality of vanes (7) movably attached thereto, wherein one or more of the extended tips are non-parallel with an edge of one or more of the plurality of vanes.

2. The turbocharger of claim 1, wherein all of the extended tips are non-parallel with all of the edges of the plurality of vanes.

3. The turbocharger (1) of claim 1, wherein the extended tips are at an angle with the edges of the plurality of vanes of between 1 and 60 degrees.

4. The turbocharger (1) of claim 1, wherein the extended tips are at an angle with the edges of the plurality of vanes of between 5 and 45 degrees.

5. The turbocharger (1) of claim 1, wherein the extended tips are at an angle with the edges of the plurality of vanes of between 10 and 30 degrees.

6. The turbocharger (1) of claim 1, wherein the plurality of vanes are positioned in a vane space (13) that is in fluid communication with the turbine wheel, wherein the vane space has an inlet (500) and wherein the extended tips extend into the inlet.

7. A method of operating a turbocharger (1), the method comprising: providing an exhaust gas flow to a turbine wheel (4) of a variable turbine geometry turbocharger, wherein the exhaust gas flow is a mixed flow having both a radial component and an axial component, and wherein the mixed flow is formed by at least one of leakage gas, secondary flow and a non-parallel incidence angle of the turbine wheel.

(WP492867 ; 1 }

8. The method of claim 7, comprising providing extended tips for the turbine wheel, wherein the extended tips are at an angle with edges of plurality of vanes of between 1 and 60 degrees.

9. The method of claim 7, comprising providing extended tips for the turbine wheel, wherein the extended tips are at an angle with edges of plurality of vanes of between 5 and 45 degrees.

10. The method of claim 7, comprising providing extended tips for the turbine wheel, wherein the extended tips are at an angle with edges of plurality of vanes of between 10 and 30 degrees.

11. The method of claim 8, wherein the plurality of vanes are positioned in a vanes space (13) that is in fluid communication with the turbine wheel, wherein the vane space has an inlet (500) and wherein the extended tips extend into the inlet.

{ WP492867 ; 1 }