A variable geometry turbine comprises a turbine wheel (5) supported in a housing for rotation about a turbine axis with an annular inlet passageway (9) defined between a radial face of a nozzle ring (11) and a facing wall of the housing (10). The nozzle ring is movable along the turbine axis to vary
A variable geometry turbine comprises a turbine wheel (5) supported in a housing for rotation about a turbine axis with an annular inlet passageway (9) defined between a radial face of a nozzle ring (11) and a facing wall of the housing (10). The nozzle ring is movable along the turbine axis to vary the width of the inlet passageway and has a circumferential array of vanes (20) that are received in corresponding slots (24) in the facing wall. A wastegate valve (15) is provided in a chamber behind the facing wall and gas bypasses the turbine through the chamber to the wastegate port (14) at high flow rates.
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1. A variable geometry turbine comprising: a turbine housing having an inlet and an outlet;a turbine wheel arranged for rotation about an axis in the housing between the inlet and outlet;the inlet comprising a substantially annular inlet passageway defined between a substantially radial face of a fi
1. A variable geometry turbine comprising: a turbine housing having an inlet and an outlet;a turbine wheel arranged for rotation about an axis in the housing between the inlet and outlet;the inlet comprising a substantially annular inlet passageway defined between a substantially radial face of a first wall and a facing second wall of the housing, the walls being movable relative to one another along the turbine axis to vary the size of the inlet passageway;a substantially annular array of vanes extending across the inlet passageway for directing exhaust gas flow towards the turbine wheel, each vane being fixed to one of the first and second walls, and a respective opening for receiving each vane being provided the other of the first and second walls to accommodate said relative movement of the walls;a chamber adjacent to the second wall, the second wall being disposed between the chamber and the first wall;a wastegate port at the chamber providing communication between the chamber and the outlet of the turbine housing; anda bypass path being provided from the inlet passageway to the chamber for exhaust gas to bypass the turbine wheel and to exit through the wastegate port. 2. A variable geometry turbine according to claim 1, wherein the wastegate port is provided at an end of the chamber distal from the second wall. 3. A variable geometry turbine according to claim 1, wherein the chamber is substantially annular. 4. A variable geometry turbine according to claim 1, wherein the chamber is defined by the housing. 5. A variable geometry turbine according to claim 1, wherein the wastegate port is provided at a distance from the axis that is substantially equal to or less than the distance of the vanes from the axis. 6. A variable geometry turbine according to claim 1, wherein the wastegate port is defined in a wall that defines an exducer passage of the outlet. 7. A variable geometry turbine according to claim 1, wherein the first and second walls are movable relative to one another between a first position in which they are spaced apart to define a relatively wide annular inlet passageway and a second position in which the they are proximate so as to define a relatively narrow annular inlet passageway. 8. A variable geometry turbine according to claim 7, wherein the bypass path is provided, at least in part, by the openings in the second wall. 9. A variable geometry turbine according to claim 8, wherein the vanes have an end that is cut away such that it has a reduced vane chord. 10. A variable geometry turbine according to claim 9, wherein in the second position of the first and second walls there is negligible peripheral clearance between the vanes and edges of the openings such that the bypass path is substantially closed and in the first position of the walls the cut away end of each vane occupies the respective opening such that the clearance between the vanes and the edges of the openings is larger than in said first position thereby ensuring the bypass path is open. 11. A variable geometry turbine according to claim 7, wherein the wastegate port is selectively closable by a valve that is operable independently of the relative movement of the walls. 12. A variable geometry turbine according to claim 11, wherein in the closed position the valve rests on a valve seat that is defined in a wall adjacent to an exducer passage portion of the outlet. 13. A variable geometry turbine according to claim 11, wherein the valve comprises a moveable member disposed in the outlet, the member having a port and being moveable between an open position in which the port is in communication with the wastegate port so as to allow flow of gas through the bypass path to the outlet and a closed position in which the port is blocked by the sleeve so as to prevent such flow. 14. A variable geometry turbine according to claim 13, wherein the movable member comprises a sleeve. 15. A variable geometry turbine according to claim 14, wherein the sleeve is slidably movable between the open and closed positions. 16. A variable geometry turbine according to claim 15, wherein the sleeve is rotatably movable between the open and closed positions. 17. A variable geometry turbine according to claim 14, wherein the movable member is an inner sleeve that is received in a fixed outer sleeve. 18. A variable geometry turbine according to claim 17, wherein at least part of the wastegate port is defined by a clearance between the outer sleeve and a wall of the turbine housing that defines the outlet. 19. A variable geometry turbine according to claim 18, wherein the clearance is a recess in a surface of the fixed sleeve. 20. A variable geometry turbine according to claim 1, wherein the inlet comprises an inlet chamber for delivering exhaust gas to the inlet passageway and the bypass path is defined, at least in part, between the inlet chamber and the chamber adjacent to the second wall. 21. A variable geometry turbine according to claim 20, wherein the inlet chamber is radially outboard of the inlet passageway. 22. A variable geometry turbine according to claim 20, wherein a bypass port is provided between the inlet chamber and the chamber adjacent to the second wall. 23. A variable geometry turbine according to claim 1, wherein the inlet comprises an inlet chamber for delivering exhaust gas to the inlet passageway and the bypass path is defined, at least in part, between the inlet chamber and the chamber adjacent to the second wall, a bypass port is provided between the inlet chamber and the chamber adjacent to the second wall, a valve member is provided inside the chamber and connected to at least one of the vanes, the valve member is movable over the bypass port such that when the walls are in the second position the valve member blocks gas communication between the bypass port and the wastegate port and when the walls are in the first position the valve member is clear of the bypass port so that bypass gas can flow from the inlet chamber through the bypass port along the bypass path to the outlet exducer passage via the wastegate port. 24. A variable geometry turbine according to claim 23, wherein the valve member is in the form of at least one piston connected to at least one of the vanes. 25. A variable geometry turbine according to claim 24, wherein the at least one piston is defined at or near the end of at least one of the vanes. 26. A variable geometry turbine according to claim 25, wherein a piston is defined at the end of each of the vanes. 27. A variable geometry turbine according to claim 23, wherein the valve member is sealed to the interior of the chamber adjacent to the second wall. 28. A variable geometry turbine according to claim 1, wherein the vanes are fixed to the first wall and the respective openings for receiving the vanes are provided in the second wall, the chamber accommodating the vanes that project through the openings. 29. A variable geometry turbine according to claim 1, wherein the second wall is defined by a shroud plate. 30. A variable geometry turbine according to claim 1, wherein the first wall is defined by a nozzle ring. 31. A turbocharger comprising a variable geometry turbine according to claim 1 and drivingly connected to a compressor. 32. A turbocharger according to claim 31 and fitted to an internal combustion engine. 33. A method for operating a variable geometry turbine in which the size of an inlet passageway defined between a substantially radial face of a first wall and a facing second wall of a housing of the turbine is varied by moving the walls relative to one another along the turbine axis, further comprising the steps of using a plurality of vanes fixed one of the first and second walls and extending across, the inlet passageway outside the turbine wheel to direct exhaust gas flow toward the turbine wheel, the vanes passing through openings in the other of the first and second walls to accommodate the relative movement, a chamber being provided adjacent to one side of the second wall, and selectively opening a bypass path so as to allow at least a portion of the exhaust gas to bypass the turbine through the chamber and to exit through a wastegate port in the chamber. 34. A method according to claim 33, wherein the openings are in the second wall and define a portion of the bypass path, the path being opened and closed by relative movement of the vanes and the openings between a first position in which there is a significant clearance between the vanes and the openings so as to open the bypass path and a second position in which the vanes substantially close the openings and therefore the bypass path. 35. A method according to claim 34, wherein the bypassing gas is allowed to enter the chamber through a port defined between the chamber and an inlet chamber of the inlet. 36. A method according to claim 33, wherein a valve is used to selectively open the bypass path. 37. A method according to claim 36, wherein a movable sleeve in the turbine outlet is selectively movable to open and close the wastegate port and therefore the bypass path. 38. A method according to claim 33, further comprising moving the first and second walls relative to one another so as to reduce the size of the inlet passageway such that the vanes are received, at least partially, within the chamber.
Arnold, Steven Don; Slupski, Kevin P.; Wiersma, Zandrie J.; Bunsirisert, Kelvin K., Variable geometry turbocharger having internal bypass exhaust gas flow.
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