US20100150701A1

US20100150701A1 - Variable geometry turbocharger

Info

Publication number: US20100150701A1
Application number: US12/663,891
Authority: US
Inventors: Volker Simon; Mathias Weber; Paul Anschel
Original assignee: BorgWarner Inc
Current assignee: BorgWarner Inc
Priority date: 2007-06-26
Filing date: 2008-06-26
Publication date: 2010-06-17
Also published as: JP2010531957A; EP2171219A2; WO2009003144A3; EP2171219A4; CN101663466A; WO2009003144A2

Abstract

A variable geometry turbocharger is provided. The turbocharger improves efficiency by controlling flow to the rotor (230) via movable vanes (260). The vanes (260) can be rotated using a pin (380, 480) and groove (385, 485) system. The vanes (260) can be multiple structures (710, 730) that are movable with respect to each other to increase the length of each of the vanes (260). The turbocharger also improves efficiency by creating a better seal in the area between the vanes (260) and the adjustment ring (240). The seal can be provided by biasing the adjustment ring (240) towards each of the vanes (260). The seal can be provided by expanding each of the vanes (260). The seal can be provided by having a movable portion (1150) of the adjustment ring (240) that is actuated by a pressure source or the like and axially moves towards the vanes (260). The plurality of vanes (260) can be low solidity vanes.

Description

FIELD OF THE INVENTION

The invention relates in general to turbochargers and, more particularly, to variable geometry turbochargers.

BACKGROUND OF THE INVENTION

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 and reducing the aerodynamic drag of the vehicle. 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.
Turbocharger units typically include a turbine operatively connected to the engine exhaust manifold, a compressor operatively connected to the engine air intake system, 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 from 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, air pressure and temperature delivered to the engine cylinders.
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 150,000 miles of operation. It has been necessary to design engine components in trucks for reliable operation in excess of 1,000,000 miles of operation for some time. This means that extra care must be taken to ensure proper design and fabrication and cooperation of all supporting devices.
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_xand 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.
Turbocharger efficiency over a broad range of operating conditions is enhanced if the flow of motive gas to the turbine wheel can be modulated. One method for achieving this level of control is to make the vanes pivotable so as to alter the geometry of the passages therebetween. The design of the mechanism used to effect pivoting of the vanes is critical to prevent binding of the vanes. Other considerations include the cost of manufacture of parts and the labor involved in assembly of such systems.
Additionally, the design of the vane is critical to both the efficiency of the gas delivery to the turbine, as well as the reliability of the variable geometry assembly. While movement of the vanes allows for control of the gas delivery, it also adds the problem of leakage past the moveable vanes. Additionally, due to the extreme environment that the moveable vanes are placed in, the structure of the vanes, especially where pivotally connected via vane posts and the like, must be sound to avoid failure.
In U.S. Published Application 20050207885 to Daudel, the Applicants attempt to control fluid delivery to the compressor wheel by providing movable guide vanes. As shown in FIG. 1, a variable diffuser geometry 13 on a rear compressor wall 14 comprises a plurality of annularly arranged guide vanes 16 which are uniformly distributed over the circumference and each of which includes a guide vane shaft 17. The guide vane shaft 17 of each guide vane 16 is pivotally supported in a support ring 18 which is surrounded by an adjustment ring 19. The radially inner end of the adjustment ring 19 is rotatably supported on the radially outer circumference of the support ring 18. The adjustment ring 19 includes a plurality of adjustment elements 20 in the form of pins arranged at an axial front side of the adjustment ring 19. The adjustment ring 19 is engaged by an adjustment member 21 in the form of an operating rod for rotating the adjustment ring 19.
The Daudel adjustment member 21 is operated by an actuator 21′. The adjustment member 21 is capable of rotating the adjustment ring 19, so that the adjustment elements 20 are moved circumferentially by a certain angle whereby the guide vanes 16 on the support ring 18 are pivoted by a corresponding angle about their guide vane shaft 17. Each guide vane 16 is fork-like shaped with two spaced fork tines 22 and 23 disposed at their outer ends between which a radially outwardly open engagement channel is formed into which the adjustment element 20 extends in any position of the adjustment ring 19. During an adjustment movement of the adjustment ring 19 in the direction of the arrow 25, the guide vanes 16 can be guided in any position of the adjustment ring 19.
The Daudel system suffers from the drawback of requiring a complicated system with numerous parts. The Daudel system further suffers from the drawback of only allowing for a particular range of motion for control of the fluid flow.
In U.S. Pat. No. 6,679,057 to Arnold, the Applicant attempts to control flow to the volute by providing movable guide vanes. As shown in FIG. 2, the Arnold system has a turbocharger 110 with a turbine housing 112 adapted to receive exhaust gas from an internal combustion engine and distribute the exhaust gas to an exhaust gas turbine wheel or turbine 114 rotatably disposed within the turbine housing 112 and coupled to one end of a common shaft 116. The turbine housing 112 encloses a variable geometry member 117 that comprises a plurality of pivotably moving vanes 118 disposed therein. A turbine adjustment or unison ring 119 is positioned within the turbine housing 112 adjacent the vanes 118 to engage the vanes and effect radially inward and outward movement of the vanes vis-a-vis the turbine in unison. The turbine unison ring 119 comprises a plurality of slots 120 disposed therein that are configured to provide a minimum backlash and a large area contact when combined with correspondingly shaped tabs 122 that project from each of the turbine vanes 118. The turbine unison ring 119 is rotatably positioned within the housing, and is configured to engage and rotate turbine vanes through identical angular movement.
The turbine unison ring 119 comprises an elliptical slot 123 that is configured to accommodate placement of an actuator pin 124 therein for purposes of moving the unison ring within the housing. The pin 124 is attached to one end of an actuator lever arm 126, that is attached at its other opposite end an actuator crank 128. The turbine actuating pin 124 and lever arm 126 are each disposed within a portion of the turbocharger center housing 130 adjacent the turbine housing. The actuator crank 128 is rotatably disposed axially through the turbocharger center housing 130, and is configured to move the lever arm 126 back and forth about an actuator crank longitudinal axis, which movement operates to rotate the actuating pin 124 and effect rotation of the unison ring 119 within the turbine housing. Rotation of the unison ring 119 in turn causes the plurality of turbine vanes to be rotated radially inwardly or outwardly vis-a-vis the turbine 114 in unison.
The turbocharger 110 also comprises a compressor housing 131 that is adapted to receive air from an air intake 132 and distribute the air to a compressor impeller 134 rotatably disposed within the compressor housing 131 and coupled to an opposite end of the common shaft 116. The compressor housing also encloses a variable geometry member 136 interposed between the compressor impeller and an air outlet. The variable geometry member is in the form of radial diffuser and comprises a plurality of pivoting vanes 138. A compressor adjustment or unison ring 140 is rotatably disposed within the compressor housing 131 and is configured to engage and rotatably move all of the compressor vanes 138 in unison. The compressor unison ring 140 comprises a plurality of slots 142 disposed therein that are each configured to provide a minimum backlash and a large area contact when combined with correspondingly shaped tabs 144 projecting from each respective compressor vane. The compressor unison ring 140 effects rotation of the plurality of compressor vanes 138 through identical angular movement.
The compressor adjustment ring 140 comprises a slot and an actuating pin 146 that is rotatably disposed within the slot. An actuating lever arm 148 is attached at one of its end to the actuating pin 146, and is attached at another one of its ends to an end of the actuator crank 128 opposite the turbine unison ring lever arm 126. The compressor unison ring actuating pin 146 and lever arm 148 are disposed through a backing plate 150 that is interposed between the turbocharger compressor housing 131 and the center housing 130. The actuator crank 128 is rotatably disposed through the center housing 130. Rotation of the actuator crank 128 causes the compressor unison actuating lever arm 148 to move around a longitudinal axis of the actuator crank, which in turn effects rotation of the compressor unison ring actuating pin 146. Rotation of the actuating pin 146 causes the compressor unison ring 140 to rotate along the backing plate 150, which in turn causes each of the compressor vanes 138 to be pivoted radially inwardly or outwardly vis-a-vis the compressor impeller 134.
The Arnold system suffers from the drawback of requiring a complicated system with numerous parts. The Arnold system further suffers from the drawback of only allowing for a particular range of motion for control of the fluid flow.
Thus, there is a need for a variable geometry system that effectively and efficiently controls fluid flow from the compressor wheel. There is a further need for such a system that is reliable and cost-effective. There is yet a further need for such a system that facilitates assembly of the turbocharger.

SUMMARY OF THE INVENTION

The present disclosure provides an efficient and cost-effective system for controlling fluid from the compressor impeller of a turbocharger. The system facilitates assembly of the turbocharger by reducing the requirement for precision fit. The system further improves efficiency by creating a better seal between the vanes and the mating surfaces against which they control the airflow.
In one aspect of the invention, a turbocharger is provided comprising a compressor housing; a compressor rotor rotatably mounted in the compressor housing; a supply channel for supplying a compressible fluid from the compressor rotor; and a vane ring assembly having an adjustment ring and a plurality of vanes. The plurality of vanes are distributed in an annular vane space and are movable to control flow of the compressible fluid. The vane angle of attack can be changed using a variety of methods. The plurality of vanes (260) can be low solidity vanes.
In another aspect, a turbocharger is provided comprising: a housing; a rotor rotatably mounted in the housing; a supply channel for supplying a fluid to the rotor; and a vane ring assembly having first and second nozzle rings. The first nozzle ring is fixed with respect to the turbocharger and has a plurality of first vanes. The second nozzle ring is rotatable with respect to the turbocharger and has a plurality of second vanes. Each of the plurality of first and second vanes is distributed in an annular vane space. Each of the plurality of first and second vanes is non-rotatable with respect to the first and second nozzle rings. The second nozzle ring is rotatable from a first position to a second position. In the first position, the plurality of first vanes are aligned with the plurality of second vanes. In the second position, the plurality of first vanes are non-aligned with the plurality of second vanes.
In another aspect, a turbocharger is provided comprising: a housing; a rotor rotatably mounted in the housing; a supply channel for supplying a fluid to the rotor; and a vane ring assembly having an adjustment ring and a plurality of vanes. The plurality of vanes are distributed in an annular vane space and are movable to control flow of the fluid. Each of the plurality of vanes is connected to the turbocharger by a rotatable pin. The adjustment ring has a sealing portion that is axially movable towards the plurality of vanes. The sealing portion is in communication with an actuator. The actuator causes the sealing portion to move towards the plurality of vanes to reduce a gap therebetween.
The turbocharger may further comprise a biasing mechanism that biases the adjustment ring towards the plurality of vanes. The biasing mechanism can be a spring. The biasing mechanism may be a plurality of springs. The turbocharger can further comprise a biasing mechanism that biases each of the plurality of vanes towards the adjustment ring. Each of the plurality of vanes can be first and second portions that are moveable with respect to each other, and the biasing mechanism can expand each of the plurality of vanes.
The biasing mechanism may be at least one spring positioned between the first and second portions. The biasing mechanism can be a compressible material. The turbocharger can further comprise a biasing mechanism that biases the first and second nozzle rings towards the plurality of first and second vanes. The actuator can be a pressure source in communication with the sealing portion via a channel. The pressure source may be pneumatic or hydraulic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a variable geometry compressor of a turbocharger according to U.S. Published Patent Application No. 20050207885;

FIG. 2 is a cross-sectional view of another variable geometry compressor of a turbocharger according to U.S. Pat. No. 6,679,057;

FIG. 3 is a cross-sectional view of a portion of a variable geometry compressor according to an exemplary embodiment of the invention;

FIG. 4 a is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 4 b is a plan view of a vane used with the variable geometry compressor of FIG. 4 a;

FIG. 5 a is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 5 b is a plan view of a vane used with the variable geometry compressor of FIG. 5 a;

FIG. 6 a is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 6 b is a plan view of a vane used with the variable geometry compressor of FIG. 6 a;

FIG. 7 is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 8 is a plan view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 9 is a plan view of a portion a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 10 is a plan view of a portion of the variable geometry compressor of FIG. 9 in a second position;

FIG. 11 a is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 11 b is a cross-sectional view of the variable geometry compressor of FIG. 11 a in a biased state;

FIG. 12 a is a perspective view of a vane of a variable geometry compressor according to another exemplary embodiment of the invention;

FIG. 12 b is a perspective view of the vane of FIG. 12 a in an un-biased state;

FIG. 13 is a cross-sectional view of a portion of a variable geometry compressor according to another exemplary embodiment of the invention; and

FIG. 14 is a schematic representation a variable geometry compressor according to another exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments described herein are directed to a variable geometry compressor system for a turbocharger. Aspects will be explained in connection with several possible embodiments of the system, but the detailed description is intended only as exemplary. The particular type of turbocharger that utilizes the exemplary embodiments of the vane and vane assemblies described herein can vary. The several embodiments are described with respect to vanes for the compressor wheel. Exemplary embodiments are shown in FIGS. 3-14, but the present disclosure is not limited to the illustrated structure or application. In one embodiment, the moveable guide vanes are low solidity vanes (i.e., low ratio of gap to chord). For example, the low solidity can be less than one.
A portion of a turbocharger system as shown in FIG. 3 includes turbomachinery in the form of a compressor housing 210, a bearing housing 220, a compressor wheel 230, an adjustment ring 240 and a flow channel 250. The flow channel or vane space 250 has a series of guide vanes 260 that allow for control of flow therethrough and thus adjustment of flow to the compressor wheel 230. The adjustment force for the vane 260 is applied at region 270, while the pivot point is along a pin or other rotation mechanism 265. The particular size or shape of each of the vanes 260 can be chosen based upon a number of factors including flow efficiency. The embodiment of FIG. 3 uses a single bearing, which is pin 265. However, the present disclosure contemplates the use of bearings on both sides of the vanes 260.
FIGS. 4 a and 4 b show a variable geometry compressor system having the compressor housing 210, the adjustment ring 240 and the flow channel 250. The adjustment force for the vane 360 is applied at region 270, while the pivot point is along the pin or other rotation mechanism 265. An adjustment pin 380 is connected to the adjustment ring 240 and is housed in a groove 385 of the vane 360. Annular movement of the adjustment ring 240 and thus adjustment pin 380 causes selective sliding of the pin within groove 385 and rotation of the vane 360.
FIGS. 5 a and 5 b show a variable geometry compressor system having the compressor housing 210, the adjustment ring 240 and the flow channel 250. The adjustment force for the vane 460 is applied at region 270, while the pivot point is along the pin or other rotation mechanism 265. An adjustment pin 480 is connected to the vane 460 and is housed in a groove 485 of the adjustment ring 240. Annular movement of the adjustment ring 240 and thus groove 485 causes selective sliding of the pin within groove 485 and rotation of the vane 460.
FIGS. 6 a and 6 b show a variable geometry compressor system having the compressor housing 210, the adjustment ring 240 and the flow channel 250. The adjustment force for the vane 560 is applied at region 270, while the pivot point is along the pin or other rotation mechanism 265. A pair of opposing adjustment pins or a fork 580 abuts the vane 560 and is connected to the adjustment ring 240. Annular movement of the adjustment ring 240 and thus fork 580 causes rotation of the vane 560 about the axis defined by pin 265.
Rotation of the adjustment ring 240 for the above-described embodiments can be by various structures and techniques including gear pairing, lever mechanisms and/or chain drives. Various sizes and shapes can be used for the components described above including the grooves, pins and forks based upon various factors including flow efficiency and effecting selected motion of the vanes 560.
FIG. 7 shows a variable geometry compressor system having the compressor housing 210, the adjustment ring 240 and the flow channel 250. The adjustment force for the vane 660 is applied along the pin or other rotation mechanism 665. For example, an adjustment moment can be applied to pin 665 via a gear 670 operably connected to an actuation device 680. Rotation of the adjustment ring 240 causes rotation of the gear 670 due to its connection to the actuation device 680.
FIG. 8 shows a variable geometry compressor system that allows for change of angle of attack or profile of the vane set. The system has a first fixed nozzle ring 700 having a series of fixed guide vanes 710 attached thereto and a second rotatable nozzle ring 720 having a series of fixed guide vanes 730 attached thereto. Rotation of the ring 720 allows for changing of the position of the vanes 730 and thus changing of the angle of attack of the total vane structure. The un-aligned position of the vanes 730 is shown by dashed lines 735. The embodiment of FIG. 8 provides for an adjustment of the operating point while reducing the number of moving parts. While the system of FIG. 8 has two nozzle rings, the present disclosure contemplates the use of more than two rings which can be various combinations of moveable and non-movable rings for adjustment of the position of each of the vanes 710, 730 with respect to each other.
FIGS. 9 and 10 show a variable geometry compressor system that allows for adjustment of the vane effective chord lengths. The system has a vane comprising first, second and third portions 800, 810, 820. Portions 800, 810 and 820 are connected to an actuation device, such as an adjustment ring 850, that allow for movement of the vane portions 800, 810, 820 along path 830. The extended vane structure is shown in FIG. 10. The embodiment of FIGS. 9 and 10 provides for an adjustment of the vane effective chord length in a synchronized manner for flow control to the compressor wheel. While the system of FIGS. 9 and 10 has three portions 800, 810, and 820 that are movable with respect to each other, the present disclosure contemplates the use of two or more movable vane portions.
In the embodiment of FIGS. 11 a and 11 b, efficiency of flow control is enhanced by reducing the gap loss resulting at the forward end of the vane, adjacent to the leading edge of the vane. Vane 900 is adjustably positioned with respect to adjustment ring 240 through use of pin 265. A biasing mechanism, such as spring 910, is utilized to bias the adjustment ring towards the vane 900 to reduce or eliminate any gap 905 between the ring and the vane. The particular type of biasing mechanism 910, e.g., a spring, and the amount of force applied can be selected so as to ensure movement of the vane while minimizing any gap. The number and configuration of the biasing mechanisms can be chosen to efficiently reduce or eliminate any gap 905 while still allowing for movement of the vanes 900, such as, for example, a plurality of equidistantly spaced springs 910 to spread the biasing force with respect to the adjustment ring 240. The adjustment mechanism can be on either the bearing housing side of the vane, or on the compressor housing side of the vane.
In the embodiment of FIGS. 12 a and 12 b, efficiency of flow control is enhanced by reducing the gap losses in the area adjacent to the leading edge of the vane. Vane 1000 is adjustably positioned with respect to an adjustment ring through use of a pin 265 or the like. A biasing mechanism, such as spring 1010, is utilized to bias the vane toward the adjustment ring and/or compressor housing to reduce or eliminate any gap therebetween. The particular type of biasing mechanism 1010 and the amount of force applied can be selected so as to ensure movement of the vane while minimizing any gap. The biasing spring 1010 can be one or more springs positioned within separate housings or portions 1015, 1020 of the vane to expand the width of the vane as desired. The biasing mechanism 1010 can also be a compressible or expandable foam or other material applied between the separate housings or portions 1015, 1020.
In the embodiment of FIG. 13, efficiency of flow control is enhanced by reducing the gap loss in the area adjacent to the leading edge of the vanes. Vane 1100 is adjustably positioned with respect to an adjustment ring 240 through use of a pin 265 or the like. A movable ring segment 1150 is utilized to reduce or eliminate any gap between the vane and the adjustment ring. The ring segment 1150 is moveably connected to the adjustment ring 240 by bearings 1160 and the like, and can be axially moved by various sources including a pneumatic or hydraulic source in communication with the segment through supply channel 1175. Movement of the segment 1150 against or in proximity to the vane 1100 can also reduce any gap between the vane and the compressor housing 210. Variations of the pressure supplied through channel 1175 can dynamically adjust the vane gaps as needed. The present disclosure also contemplates movement of the segment 1150 by other means such as electrical controllers, springs or mechanical actuators.
FIG. 14 shows a variable geometry compressor system having a flexible vane 1200 that is connected to the turbocharger by a rotatable pin 265 or the like. The pin 265 is rigidly connected to the vane 1200 and can be connected to the compressor housing and/or adjustment ring. Pins or a fork 1220 abuts against the vane 1200. A rotational force 1210 applied to pin 265 causes flexing of the vane into the shape shown by dashed line 1250. It should be understood that features of the various exemplary embodiments can be interchangeable with one another. The foregoing description is provided in the context of exemplary embodiments of vanes and vane assemblies for a turbocharger. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.

Claims

1. A turbocharger including means for minimizing axial vane gap, comprising:

a compressor housing (210);

a compressor rotor (230) rotatably mounted in the compressor housing (210);

a volute (250) for receiving a compressible fluid from compressor rotor (230); and

a vane ring assembly comprising a plurality of vanes (260), the plurality of vanes (260) being mounted for rotation to control flow of the compressible fluid in an annular vane space radially between compressor wheel and volute and axially between first and second walls, and

means for application of axial force between said vanes and at least one of said walls.

2. A turbocharger as in claim 1, wherein said axial force is a spring force, a hydraulic force, a pneumatic force, or an electrical force.

3. The turbocharger of claim 2, wherein said plurality of vanes (260) are mounted on an adjustment ring forming at least a part of, and wherein said means for application of axial force comprises a biasing mechanism (910) that biases the adjustment ring (240), and vanes mounted thereon, towards the wall opposite the adjusting ring.

4. The turbocharger of claim 2, wherein said means for application of axial force comprises a biasing mechanism (1010) that biases each of the plurality of vanes (260) towards the adjustment ring (240) or towards the wall opposite the adjusting ring.

5. The turbocharger of claim 2, wherein said means for application of axial force comprises a biasing mechanism (1010) that biases each of the walls towards each other.

6. The turbocharger of claim 1, wherein said means for application of axial force comprises is at least one coil spring.

7. The turbocharger of claim 1, wherein each of the plurality of vanes (260) are connected to the turbocharger by a rotatable pin (265), wherein either the vanes (260) or the adjustment ring (240) has an adjustment pin (380, 480) rigidly connected thereto, wherein the other of the vanes (260) or the adjustment ring (240) has a groove (385, 485), wherein the adjustment pin (380, 480) is partially inserted into the groove (385, 485), and wherein rotation of the adjustment ring (240) causes rotation of the vanes (260).

8. The turbocharger of claim 6, wherein each of the plurality of vanes has first and second portions (1015, 1020) that are moveable axially with respect to each other, and wherein the biasing mechanism (1010) axially biases each of the vane portions.

9. A turbocharger comprising:

a housing (210);

a rotor (230) rotatably mounted in the housing (210);

a supply channel (250) for supplying a fluid to the rotor (230); and

a vane ring assembly having first and second nozzle rings (700, 720), the first nozzle ring (700) being fixed with respect to the turbocharger and having a plurality of first vanes (710), the second nozzle ring (720) being rotatable with respect to the turbocharger and having a plurality of second vanes (730), each of the plurality of first and second vanes (710, 730) being distributed in an annular vane space, each of the plurality of first and second vanes (710, 730) being non-rotatable with respect to the first and second nozzle rings (700, 720),

wherein the second nozzle ring (720) is rotatable from a first position to a second position, wherein in the first position the plurality of first vanes (710) are aligned with the plurality of second vanes (720), and wherein in the second position the plurality of first vanes (710) are non-aligned with the plurality of second vanes (720).

10. A turbocharger as in claim 9, wherein each of the plurality of first and second vanes (710, 730) has first and second portions (1015, 1020) that are moveable with respect to each other, and wherein the biasing mechanism (1010) expands each of the plurality of first and second vanes (710, 730)