Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D17/00—Regulating or controlling by varying flow
  • F01D17/10—Final actuators
  • F01D17/12—Final actuators arranged in stator parts
  • F01D17/14—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits
  • F01D17/141—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of shiftable members or valves obturating part of the flow path
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D17/00—Regulating or controlling by varying flow
  • F01D17/10—Final actuators
  • F01D17/12—Final actuators arranged in stator parts
  • F01D17/18—Final actuators arranged in stator parts varying effective number of nozzles or guide conduits, e.g. sequentially operable valves for steam turbines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2220/00—Application
  • F05D2220/40—Application in turbochargers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/10—Stators
  • F05D2240/12—Fluid guiding means, e.g. vanes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/60—Structure; Surface texture
  • F05D2250/61—Structure; Surface texture corrugated
  • F05D2250/611—Structure; Surface texture corrugated undulated

Definitions

• the present invention relates to a variable geometry turbine.
• the variable geometry turbine may, for example, form a part of a turbocharger.
• Turbochargers are well known devices for supplying air to an intake of an internal combustion engine at pressures above atmospheric pressure (boost pressures).
• a conventional turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing connected downstream of an engine outlet manifold. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to an engine intake manifold.
• the turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housings.
• the turbine stage of a typical turbocharger comprises: a turbine chamber within which the turbine wheel is mounted; an annular inlet defined between facing radial walls arranged around the turbine chamber; an inlet volute arranged around the annular inlet; and an outlet passageway extending from the turbine chamber.
• the passageways and chamber communicate such that pressurised exhaust gas admitted to the inlet volute flows through the inlet to the outlet passageway via the turbine and rotates the turbine wheel.
• vanes referred to as nozzle vanes
• Turbines may be of a fixed or variable geometry type.
• Variable geometry turbines differ from fixed geometry turbines in that the size of the inlet can be varied to optimise gas flow velocities over a range of mass flow rates so that the power output of the turbine can be varied to suit varying engine demands. For instance, when the volume of exhaust gas being delivered to the turbine is relatively low, the velocity of the gas reaching the turbine wheel is maintained at a level which ensures efficient turbine operation by reducing the size of the inlet using a variable geometry mechanism.
• Turbochargers provided with a variable geometry turbine are referred to as variable geometry turbochargers. Nozzle vane arrangements in variable geometry turbochargers can take different forms.
• the vanes are fixed to an axially movable wall that slides across the inlet passageway.
• the axially movable wall moves towards a facing shroud plate in order to close down the inlet passageway and in so doing the vanes pass through apertures in the shroud plate.
• the nozzle ring is fixed to a wall of the turbine and a shroud plate is moved over the vanes to vary the size of the inlet passageway.
• the moving component of the variable geometry mechanism whether it is the nozzle ring or the shroud plate, is supported for axial movement in a cavity in a part of the turbocharger housing (usually either the turbine housing or the turbocharger bearing housing). It may be sealed with respect to the cavity walls to reduce or prevent leakage flow around the back of the nozzle ring.
• the moveable wall of the variable geometry mechanism is axially displaced by a suitable actuator assembly comprising an actuator and a linkage.
• a suitable actuator assembly comprising an actuator and a linkage.
• the linkage comprises a yoke pivotally supported within the bearing housing and having two arms, each of which extends into engagement with an end of a respective push rod on which the moving component (in this instance the nozzle ring) is mounted.
• the yoke is mounted on a shaft journaled in the bearing housing and supporting a crank external to the bearing housing which may be connected to the actuator in any appropriate manner.
• the actuator which moves the yoke can take a variety of forms, including pneumatic, hydraulic and electric forms, and can be linked to the yoke in a variety of ways.
• the actuator will generally adjust the position of the moving wall under the control of an engine control unit (ECU) in order to modify the airflow through the turbine to meet performance requirements.
• ECU engine control unit
• axial forces are imported on the moveable wall by the air flow through the inlet, which must be accommodated by the actuator assembly.
• a torque is imparted to the nozzle ring as a result of gas flow vane passages being deflected towards the direction of rotation of the turbine wheel. If the nozzle ring is the moving wall of the variable geometry mechanism this torque also has to be reacted or otherwise accommodated by the actuator assembly such as by parts of the linkage. It is one object of the present invention to obviate or mitigate the aforesaid disadvantages.
• variable geometry turbine comprising a turbine wheel mounted for rotation about a turbine axis within a housing, the housing defining an annular inlet surrounding the turbine wheel and defined between first and second inlet sidewalls; and a cylindrical sleeve axially movable across the annular inlet to vary the size of a gas flow path through the inlet; wherein the annular inlet is divided into at least three axially offset inlet passages by two or more inlet passage walls disposed between the first and second inlet sidewalls.
• axially offset inlet passages include inlet passages with different axial positions and/or inlet passages with different axial extents. Axially offset inlet passages may be spaced apart, adjacent or axially overlapping.
• the inlet passage walls may be axially spaced annular baffles, the baffles dividing the annular inlet into axially adjacent annular portions.
• the number of baffles may be one of 2, 3, 4, 5 or 6.
• variable geometry turbine may further comprise inlet vanes which extend axially across at least two of said axially adjacent annular portions; wherein the cylindrical sleeve is axially movable across the annular inlet to vary the size of a gas flow path through the inlet between a free end of the sleeve and the first inlet sidewall; and wherein the axial width of the inlet vanes extending across a first annular portion of the inlet is less than the axial width of the inlet vanes extending across a second annular portion of the inlet, the first annular portion being closer the first inlet sidewall than the second annular portion is to the first inlet sidewall.
• the two or more inlet passage walls may define an annular array of substantially tubular inlet passages extending generally towards the turbine wheel, wherein the annular array of inlet passages comprises at least three axially offset inlet passages.
• the sleeve may be axially movable between an open position in which there is a gas flow path through the inlet, between a free end of the sleeve and the first inlet sidewall, through at least one of said at least three axially offset inlet passages, and a closed position in which the size of said gas flow path through the inlet between the free end of the sleeve and the first inlet sidewall is reduced compared to that when the sleeve is in the open position; and wherein the sleeve moves in a direction towards said first inlet sidewall when the sleeve is moved from the open position towards the closed position.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between at least two of the two or more inlet passage walls and the first inlet sidewall.
• the axial distance between all of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between at least two of the two or more inlet passage walls and the first inlet sidewall.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between each of the two or more inlet passage walls and the first inlet sidewall.
• the axial distance between all of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between each of the two or more inlet passage walls and the first inlet sidewall.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than the axial distance between one of the two or more inlet passage walls and the first inlet sidewall, and wherein said one of the two or more inlet passage walls is located such that the axial distance between said one of the two or more inlet passage walls and the first inlet sidewall is less than or equal to substantially 50% of the axial distance between the first and second inlet sidewalls.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than the axial distance between one of the two or more inlet passage walls and the first inlet sidewall, and wherein the sleeve substantially does not contact said one of the two or more inlet passage walls when the sleeve is in the closed position.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than the axial distance between one of the two or more inlet passage walls and the first inlet sidewall, and wherein the sleeve is mounted such that gas may pass between said one of the two or more inlet passage walls and the sleeve when the sleeve is in the closed position, the gas then passing through the inlet.
• the sleeve may be mounted such that, when the sleeve is in the closed position, the sleeve substantially does not contact any of the two or more inlet passage walls.
• An axial dimension of a first of said axially offset inlet passages may be less than an axial dimension of a second of said axially offset inlet passages, and wherein the first of said axially offset inlet passages is located closer the first inlet sidewall than the second of said axially offset inlet passages.
• a variable geometry turbine may comprise an annular inlet surrounding a turbine wheel mounted for rotation about a turbine axis within a turbine chamber defined by a housing, the chamber having an annular inlet defined between inboard and outboard inlet side walls and surrounding the turbine wheel, the annular inlet including:
• exhaust gas may flow to the annular inlet via a surrounding volute.
• the volute may be axially or circumferentially divided, the annular inlet being defined downstream of the volute or any divided portion of the volute. In such divided volute turbines the adjacent volute portions generally do not communicate with each other, other than at their downstream ends where they terminate at the inlet.
• the inboard and outboard inlet sidewalls may for instance be continuations of walls which define the volute.
• the maximum width of the inlet will correspond to the area swept out by rotation of the tips of the turbine wheel blades.
• each of the second pair of inlet passages may be fully blocked to gas flow.
• variable geometry turbochargers may include a third pair of fourth and fifth circumferentially spaced inlet passages which are axially displaced from both the first and second pairs of inlet passages.
• Such embodiments may comprise four or more axially displaced pairs of circumferentially spaced inlet passages.
• all but one of said axially spaced pairs of circumferentially spaced inlet passages may be fully blocked to gas flow, the remaining pair of circumferentially spaced inlet passages being at least partially blocked to gas flow.
• Each of the pairs of inlet passages may be a part of a respective annular array of circumferentially spaced inlet passages surrounding the turbine wheel.
• Each pair or annular array of inlet passages may comprise passages which are substantially axially coincident.
• At least one inlet passage of at least one pair or annular array of inlet passages may axially overlap at least one of the inlet passages of an adjacent pair or annular array of inlet passages.
• the first position of the sleeve may be an open position in which each of said pairs or annular arrays of circumferentially spaced inlet passages are open to gas flow.
• the second position of the sleeve may be a closed position in which a free end of the sleeve projects across the annular inlet and abuts either the inboard or outboard side wall.
• the sleeve may be controllably positioned between said first and second positions.
• a variable geometry turbine may comprise a turbine wheel mounted for rotation about a turbine axis within a housing, the housing defining a annular inlet surrounding the turbine wheel and defined between inboard and outboard inlet side walls, wherein a cylindrical sleeve is mounted within the housing for axial slideable movement across at least a portion of the annular inlet to vary the size of the annular inlet, further comprising:
• annular baffle axially spaced from the inboard and outboard side walls of the annular inlet to divide the annular inlet into axially adjacent annular portions, and wherein inlet vanes extend axially across at least two of said annular portions defined by the or each baffle.
• gas may flow to the annular inlet via an annular volute or similar chamber surrounding the annular inlet.
• the volute may be a divided volute, for instance split into separate axial or circumferential portions which may for instance receive gas from different sources (e.g. different banks of cylinders in a multi-cylinder combustion engine).
• the inlet and baffle will be downstream of the volute, or any volute portions in a divided volute.
• a variable geometry turbine may comprise two or more axially spaced inlet baffles which axially divide the annular inlet into three or more annular regions, wherein inlet vanes extend across at least three of said annular regions. At least some inlet vanes may extend across the full width of the annular inlet between the inboard and outboard side walls. For instance, an annular array of inlet vanes may extend across the annular inlet between the inboard and outboard side walls and two or more annular inlet baffles may be axially spaced within the annular inlet which together with the vanes define three or more axially spaced annular arrays of inlet passages.
• a variable geometry turbine may comprise a turbine wheel mounted for rotation about a turbine axis within a housing, the housing having an annular inlet surrounding the turbine wheel and defined between inboard and outboard inlet side walls, wherein the annular inlet is axially divided into adjacent annular regions by two or more annular inlet baffles, and wherein a cylindrical sleeve is mounted within the housing for axial slideable movement across at least a portion of the annular inlet to vary the size of the annular inlet.
• the annular inlet may be defined downstream of a surrounding volute (which may be a divided volute) or similar gas chamber.
• Inlet vanes may extend across at least one of the annular regions to divide the annular region into a circumferential spaced array of inlet passages.
• variable geometry turbines which include inlet vanes as mentioned above, may be such that the trailing edges of at least a majority of vanes extending across an annular portion of the inlet may lie on a radius greater than the internal radius of a baffle defining the annular portion.
• all of the vanes extending across an annular portion of the inlet may have a trailing edge lying at a radius greater than the internal radius of a baffle defining the annular portion.
• each annular baffle may have an internal radius smaller than the radius of the leading edge of any vane of the annular inlet.
• At least some of the vanes extending across a first annular portion of the inlet may have a configuration different to at least some of the vanes extending across a second annular portion of the inlet.
• variable geometry turbines may comprise at least two of said annular baffles which divide the annular inlet into at least three axially adjacent annular portions. Movement of the sleeve between positions defining the maximum and minimum width of the inlet is confined to discreet positions corresponding to the axial location of the or each annular baffle. Accordingly, in some variable geometry turbines the sleeve may be controlled to move in a step-wise fashion between discreet positions which may correspond to open and closed positions as well as intermediate positions, wherein each of the intermediate positions corresponds to the position of an annular baffle. In such intermediate positions the free end of the sleeve may axially align with the leading edge of a baffle.
• variable geometry turbines may comprise at least two of said annular baffles dividing the annular inlet into at least three axially adjacent annular portions, wherein at least one of said annular portions does not include any inlet vanes.
• a variable geometry turbine may comprise a turbine wheel mounted for rotation about a turbine axis within a housing, the housing including an annular inlet surrounding the turbine wheel and defined between inboard and outboard inlet side walls, wherein an annular array of inlet vanes extends between the inboard and outboard inlet side walls defining circumferentially spaced vane passages between adjacent inlet vanes, and wherein substantially circumferentially extending baffle walls extend between at least some adjacent pairs of inlet vanes to divide the respective vanes passages into axially spaced inlet passages.
• At least one baffle wall may be annular.
• a variable geometry turbine may comprise a turbine wheel mounted for rotation about a turbine axis within a housing, the housing including an annular inlet surrounding the turbine wheel and defined between inboard and outboard inlet side walls, wherein the annular inlet includes a nozzle structure comprising an annular array of substantially tubular inlet passages extending generally towards the turbine wheel, wherein the annular array of inlet passages comprises at least three axially displaced inlet passages.
• the nozzle structure may be disposed downstream of an annular volute (which may be axially or circumferentially divided) which surrounds the annular inlet passage to deliver gas flow to the annular inlet passage.
• annular volute which may be axially or circumferentially divided
• the inlet passages may have a generally diamond; pentagonal, hexagonal or other polygonal cross section along at least a portion of their length.
• the geometry of any given inlet passage may vary along its length.
• the cross-sectional area of the inlet passage may decrease to a minimum and then increase again.
• the cross-sectional area may change shape at different positions along its length.
• the inlet passage may have one cross section at its inlet (upstream) end and another cross section at its outlet (downstream) end.
• the cross section may change gradually along its length from inlet to outlet.
• Inlet passages may be substantially straight, or may be curved. In either case they may be swept forwards or backwards relative to the direction of rotation of the turbine wheel.
• Adjacent annular arrays may comprise inlet passages of a different number and/or size and/or geometry or configuration. For instance the passages of one annular array may define a different swirl angle to the passages of another annular array.
• the inlet passages may be defined by two or more annular inlet baffles positioned within the annular inlet, wherein adjacent inlet baffles contact one another or are otherwise joined to one another at circumferentially spaced locations to define inlet passages between the areas of contact.
• the annular inlet baffles may be circumferentially corrugated, so that the areas of contact between adjacent baffles extend across substantially the full radial width of each annular baffle.
• the cylindrical sleeve of any aspect of the invention may be mounted within a housing cavity separated from the inlet passage by said inboard side wall, wherein a free end of the cylindrical sleeve extends from said cavity into the annular inlet to define the width of the annular inlet.
• Gas flow through the annular inlet may therefore be confined between the free end of the sleeve and the outboard side wall.
• the housing comprises a bearing or centre housing portion, and a turbine housing portion, wherein the turbine wheel rotates in a chamber defined between the bearing/central housing and the turbine housing portions, and wherein the cylindrical sleeve is mounted with a housing cavity defined within the bearing/central housing.
• the cylindrical sleeve of any of the aspects of the invention may alternatively be mounted within a housing cavity separated from the inlet passage by said outboard side wall, wherein a free end of the cylindrical sleeve extends from said cavity into the annular inlet to define the width of the annular inlet.
• Gas flow through the annular inlet may therefore be confined between the free end of the sleeve and the inboard side wall.
• the housing comprises a bearing or centre housing portion, and a turbine housing portion, wherein the turbine wheel rotates in a chamber defined between the bearing/central housing and the turbine housing portions, and wherein the cylindrical sleeve is mounted with a housing cavity defined within the turbine housing.
• the cylindrical sleeve is preferably movable across an outside diameter of the annular inlet to selectively block upstream ends of respective inlet passages or portions relative to gas flow through the turbine.
• cylindrical sleeve is movable across an inside diameter of the annular inlet to selectively block downstream ends of respective inlet passages or portions relative to gas flow through the turbine.
• the sleeve surrounds the inlet portions (i.e. the sleeve is movable across an outside diameter of the annular inlet), which has been found to give an improved aerodynamic performance.
• the inner diameter of the sleeve is greater than an outer diameter (or outer radial extent) of the inlet portion or portions.
• the sleeve may be surrounded by the inlet portions.
• the outer diameter of the sleeve may be less than inner diameter of the inlet portion or portions.
• the sleeve may be moveable through the inlet portion or portions.
• the diameter (e.g. inner or outer, or average diameter) of the sleeve may be less than an outer diameter of the inlet portion or portions, and greater than an inner diameter of the inlet portion or portions.
• a variable geometry turbine may comprise a turbine wheel mounted for rotation about a turbine axis within a housing, the housing defining an annular inlet surrounding the turbine wheel and defined between inboard and outboard inlet sidewalls, and further comprising at least one annular baffle axially spaced from the inboard and outboard sidewalls of the annular inlet to divide the annular inlet into axially adjacent annular portions, and a cylindrical sleeve axially movable within the annular inlet around the outside diameter of the annular inlet portions and said at least one annular baffle to vary the size of the annular inlet defined between a free end of the sleeve and either the inboard or outboard sidewall.
• the annular inlet may be defined downstream of a surrounding volute (including a divided volute or similar chamber for delivering gas flow to the annular inlet).
• the effective axial width of the inlet is defined between the free end of the sleeve and either the inboard or outboard sidewalls (depending on which side of the housing the sleeve is mounted).
• the cylindrical sleeve is mounted for movement in a step-wise manner between an open position, a closed position, and one or more positions corresponding to the position of the or each annular baffle.
• the sleeve is therefore constrained to move between discreet predetermined positions, some of which correspond to the location of inlet baffles.
• the sleeve may be prevented from being positioned such that its free end lies between adjacent baffles.
• One or more vanes may extend across at least one of the annular inlet portions.
• a method of controlling or operating a turbine according to the present invention in which the sleeve is moved in discreet axial steps between positions corresponding to a closed position, an open position and intermediate positions in which the free end of the sleeve is aligned with an annular inlet baffle.
• Fig. 1 is an axial cross-section through a known turbocharger including a variable geometry turbine.
• Fig. 2 is a schematic representation of a radial view around a portion of the circumference of the annular inlet of the turbine illustrated in Figure 1.
• Fig. 3 is an axial cross-section through part of a turbocharger including a variable geometry turbine in accordance with an embodiment of the present invention.
• Figs. 4a and 4b illustrate detail of the nozzle assembly of the turbine of Fig. 3.
• Fig. 5 is a schematic representation of a radial view around a portion of the circumference of the annular inlet of the nozzle assembly of Figures 4a and 4b.
• Fig. 6 shows the schematic illustration of Fig. 5 modified to show a sleeve forming part of the nozzle assembly of Figs. 4a and 4b.
• Figs. 7a to 7g are axial cross-sections through part of a variable geometry turbine in accordance with alternative embodiments of the present invention.
• Figs. 8a - 8c are schematic illustrations of further embodiments of the present invention.
• Figs. 9a to 9f, 10a to 10d, 11 , 12a to 2d, and 13 to 8 are each schematic illustrations of a radial view around a portion of the circumference of a respective inlet structure in accordance with various embodiments of the present invention.
• Fig. 19 is a schematic illustration of a radial view around a portion of the circumference of an annular inlet structure in accordance with a embodiment of the present invention.
• Figs. 20a and 20b illustrate a modification of an embodiment of the present invention.
• Figs. 21 a to 21c are axial cross-sections through part of a turbine in accordance with another embodiment of the present invention.
• Figs. 22a and 22b schematically illustrate a detail of possible modifications to embodiments of the present invention.
• FIG. 1 this illustrates a known turbocharger comprising a variable geometry turbine housing 1 and a compressor housing 2 interconnected by a central bearing housing 3.
• a turbocharger shaft 4 extends from the turbine housing 1 to the compressor housing 2 through the bearing housing 3.
• a turbine wheel 5 is mounted on one end of the shaft 4 for rotation within the turbine housing 1
• a compressor wheel 6 is mounted on the other end of the shaft 4 for rotation within the compressor housing 2.
• the shaft 4 rotates about turbocharger axis 4a on bearing assemblies located in the bearing housing.
• the turbine housing 1 defines a volute 7 to which gas from an internal combustion engine (not shown) is delivered.
• the exhaust gas flows from the volute 7 to an axial outlet passageway 8 via an annular inlet 9 and turbine wheel 5.
• the inlet 9 is defined between sides walls, one side wall being surface 10 of a radial wall of a movable annular nozzle ring wall member 11 and on the opposite side wall being an annular shroud plate 12.
• the shroud 12 covers the opening of an annular recess 13 in the turbine housing 1.
• the nozzle ring 11 supports an array of circumferentially and equally spaced nozzle vanes 14 each of which extends across the full axial width of the inlet 9.
• the nozzle vanes 14 are orientated to deflect gas flowing through the inlet 9 towards the direction of rotation of the turbine wheel 5.
• the vanes 14 project through suitably configured slots in the shroud 12, into the recess 13.
• An actuator (not shown) is operable to control the position of the nozzle ring 11 via an actuator output shaft (not shown), which is linked to a stirrup member 15.
• the stirrup member 15 in turn engages axially extending guide rods 16 that support the nozzle ring 11. Accordingly, by appropriate control of the actuator (which may for instance be pneumatic or electric or any other suitable type), the axial position of the guide rods 16 and thus of the nozzle ring 11 can be controlled. It will be appreciated that details of the nozzle ring mounting and guide arrangements may differ from those illustrated.
• the nozzle ring 11 has axially extending radially inner and outer annular flanges 17 and 18 that extend into an annular cavity 19 provided in the turbine housing 1.
• Inner and outer sealing rings 20 and 21 are provided to seal the nozzle ring 1 with respect to inner and outer annular surfaces of the annular cavity 19 respectively, whilst allowing the nozzle ring 11 to slide within the annular cavity 19.
• the inner sealing ring 20 is supported within an annular groove formed in the radially inner annular surface of the cavity 19 and bears against the inner annular flange 17 of the nozzle ring 1 1.
• the outer sealing ring 20 is supported within an annular groove formed in the radially outer annular surface of the cavity 19 and bears against the outer annular flange 18 of the nozzle ring 11.
• Gas flowing from the inlet volute 7 to the outlet passageway 8 passes over the turbine wheel 5 and as a result torque is applied to the shaft 4 to drive the compressor wheel 6.
• Rotation of the compressor wheel 6 within the compressor housing 2 pressurises ambient air present in an air inlet 22 and delivers the pressurised air to an air outlet volute 23 from which it is fed to an internal combustion engine (not shown).
• the speed of the turbine wheel 5 is dependent upon the velocity of the gas passing through the annular inlet 9.
• the gas velocity is a function of the width of the inlet 9, the width being adjustable by controlling the axial position of the nozzle ring 11. (As the width of the inlet 9 is reduced, the velocity of the gas passing through it increases.)
• Figure 1 shows the annular inlet 9 fully open.
• the inlet passageway 9 may be closed to a minimum by moving the nozzle ring 11 towards the shroud 12.
• FIG 2 this is a schematic representation of a radial view around a portion of the circumference of the annular inlet 9 of the turbine of Fig 1 , un-rolled and laid flat in the plane of the paper.
• the nozzle ring 1 1 is in a fully open position such that parallel lines 11 and 12 represent the nozzle ring 11 and shroud plate 12 respectively, and parallel lines 14 represent the leading edges of the nozzle vanes 14 which extend across the inlet 9.
• the dimension c is a portion of the circumference of the inlet 9, and the dimension w is the maximum width of the annular inlet 9. From Fig 2 it can be seen that the vanes 14 divide the annular inlet 9 into an annular array of circumferentially adjacent inlet passages 14a.
• Each inlet passage 14a extends generally radially, but with a forward sweep (with decreasing radius) resulting from the configuration of the vanes 14 which as mentioned above is designed to deflect the gas flow passing through the inlet 9 towards the direction of rotation of the turbine wheel.
• the geometry of each of the inlet passages 14a, which extend across the full width w of the inlet 9, is defined by the configuration and spacing of the vanes 14, but as shown have a generally rectangular cross-section.
• Fig 3 is a cross-section through part of a turbocharger including a variable geometry turbine in accordance with an embodiment of the present invention. Where appropriate corresponding features of the turbochargers of Fig 1 and Fig 3 are identified with the same reference numbers.
• Fig 3 shows the bearing housing 3 and turbine housing 4 of the turbocharger, with the compressor (not shown) removed.
• a turbocharger shaft 4 extends through the bearing housing 3 to the turbine housing 1 and a turbine wheel 5 is mounted on one end of the shaft 4 within the turbine housing 1.
• the turbine housing 1 defines a volute 7 from which exhaust gas flow is delivered to an annular inlet 9 which surrounds the turbine wheel 5.
• the size of the inlet 9 is variable by controlling the position of an axially sliding cylindrical sleeve 30 which is supported on guide rods 31 which are slidably mounted within a cavity 19 defined by the bearing housing 3.
• the guide rods 31 may have a configuration substantially the same as that of the guide rods 16 illustrated in Fig 1 , and be actuated in the same way via a yoke (not shown) linked to inboard ends 31 a of the guide rods 31.
• Outboard ends 31 a of the guide rods 31 are connected to radially extended flanges 30a of the sleeve 30.
• Respective separate flanges 30a maybe provided for connection to the guide rods 31 as illustrated, or the sleeve 30 may comprise a single annular radially extending flange which is connected to the guide rods 31.
• the sleeve 30 has a free end which projects into the inlet 9 so that the width of the inlet can be varied in a controlled manner by appropriate movement and positioning of the sleeve 30 via the guide rods 31.
• the inlet 9 is, at least in part, defined between facing side walls of the turbine housing which in this embodiment comprise nozzle rings 32 and 33 of a nozzle assembly 34.
• the nozzle assembly 34 is shown in greater detail in Figs 4a and 4b (together with a section of the sleeve 30, and a guide rod 31).
• the first nozzle ring 32 of the nozzle assembly 34 extends radially across the opening of the cavity 19 of the turbine housing to the sleeve 30.
• Seal ring 35 seals the nozzle ring 32 with respect to the sleeve 30 to prevent gas leakage between the inlet 9 and the cavity 19.
• a seal ring 36 seals the nozzle ring 32 with respect to the turbine housing adjacent a radial inner periphery of the nozzle ring 32.
• the second nozzle ring 33 of the nozzle ring assembly 34 is fixed to a radial wall of the turbine housing, within a shallow annual recess defined by the turbine housing and is sealed with respect thereto by seal ring 36 to prevent gas leakage between the nozzle ring 33 and the turbine housing.
• An annular array of circumferentially equispaced nozzle vanes 37 extend between the first and second nozzle rings 32 and 33. The nozzle vanes 37 divide the annular inlet into circumferentially spaced inlet portions.
• Radially extending annular inlet baffles 38a, 38b and 38c are axially equispaced between the nozzle rings 32 and 33 and further divide the annular inlet 9 into axially spaced inlet portions.
• the baffles 38 are relatively thin rings coaxial with the turbine axis and orientated parallel to the nozzle rings 32 and 33 so that they have radially extending faces.
• Fig 5 is a schematic representation of a radial view of an un-rolled portion of the circumference of the nozzle assembly 34 corresponding to the representation of the known inlet structure shown in Fig 2.
• the dimension w is the full width of the inlet 9 and the dimension c is a portion of the circumference of the inlet.
• the vanes 37, and inlet baffles 38a-38c divide the inlet 9 into four axially spaced annular arrays of circumferentially spaced inlet passages 39a, 39b, 39c and 39d respectively.
• the known arrangement of Fig 2 has a single annular array of circumferentially spaced inlet passages, each of which extends across the full width of the inlet 9.
• the exact configuration of the inlet passages 39a to 39d is defined by the configuration of the vanes 37 and baffles 38a to 38c, but as illustrated it can be seen that the passages have a generally rectangular (in this case nearly square) cross section.
• Each of the inlet passages 39a - 39d directs gas flow to the turbine wheel, and due to the sweep of the vanes 37 turns the gas flow in a direction towards to the direction of the rotation of the turbine wheel 5.
• the inlet passages 39 in each annular array are circumferentially adjacent and each annular array 39a to 39d is axially adjacent to the next.
• the size of the inlet 9 is controlled by adjustment of the axial position of the sleeve 30 which slides over the outside diameter of the vanes and baffles.
• one or more of the axially spaced annular arrays of inlet passages 39a-39d may therefore be blocked or partially blocked to gas flow through the inlet 9.
• Fig 4a illustrates the sleeve 30 in an almost fully open position in which the first annular array of gas flow passages 39a is partially blocked to gas flow, and the second to fourth annular arrays of inlet passages 39b-39d are fully open to gas flow.
• Fig 4b (and Fig 3), show the sleeve 30 in a fully closed position in which the end of the sleeve 30 bears against the nozzle ring 33 and all four of the axially adjacent annular arrays of inlet passages 39a-39d are closed (subject to the potential for a minimum amount of leakage into the inlet passages 39d between the sleeve 30 and the nozzle ring 33).
• a selected number of the axially adjacent annular arrays of inlet passages 39a-39d may be opened or blocked, or partially opened/blocked.
• the sleeve 30 can fully close the inlet, i.e. block the inlet 9 completely.
• the sleeve need not necessarily be capable of closing the inlet fully, but might have a "closed" position in which the final array of passages 39 is at least partially open.
• the free end of the sleeve could be provided with axially extending lands which provide a hard stop for the closed position of the sleeve, with flow gaps defined between lands around the circumference of the sleeve.
• the increased acceleration of the gas flow is achieved by reducing the size of the inlet 9 occurs upstream of the inlet passages 39.
• Figs 3 to 6 has three inlet baffles 38, but more or less than three baffles could be incorporated in alternative embodiments.
• provision of only a single inlet baffle, for example midway between the nozzle rings 32 and 33, may improve efficiency above that attainable in the absence of any inlet baffle to a sufficient extent to provide an effective variable geometry turbine structure for use in a turbocharger and other applications.
• Efficiency of the turbine inlet can be expected to vary in a somewhat step-wise function of inlet size corresponding to the location of the or each inlet baffle. This effect can however be smoothed by increasing the number of baffles. Although increasing the number of baffles (which have an axial thickness) may increase aerodynamic drag and reduce the maximum cross-sectional flow area available to gas flow for any given inlet width w, this may, if necessary, be compensated by constructing the annular inlet 9 to have a larger maximum axial width and than would be the case in the absence of baffles.
• the turbine according to the present invention also has a number of other advantages over the known moving nozzle ring turbine shown in Fig 1.
• the present invention there are considerably reduced pressure and aerodynamic forces on the sleeve compared to those acting on a radial wall.
• the axial force imposed on the sleeve 30 by air flow through the inlet is much less than that imposed on a moveable radial wall.
• This allows the use of a smaller, less robust actuator, and also a less robust linkage between the actuator and the sleeve, as the axial force required to move the sleeve and hold it in position is much less than that required to control the position of a radial wall.
• Known devices comprising a moveable nozzle ring in which the moving wall member includes the vanes, for instance as shown in Fig 1 , also experience significant torque as the gas flow is deflected by the vanes. With the present invention there is no such torque on the moving component which further reduces the force on the actuator and actuator linkages.
• the inlet passages 39 are defined by a nozzle assembly 34 comprising the nozzle rings 32 and 33 which support the inlet vanes 37 and baffles 38.
• the nozzle rings 32 and 33 thus define the sidewalls of the annular inlet 9 of the turbine.
• This structure may have advantages such as allowing differently configured nozzle assemblies to be fitted to a common turbine housing so that the inlet structure (i.e.
• inlet passages 39 may be varied between turbines which are otherwise substantially identical. This (modular) construction may have manufacturing benefits.
• the vanes 37 and baffles 38 which define the passages 39 need not be formed in a separable modular nozzle assembly, but could be cast or machined integrally with the turbocharger housing (e.g. the bearing housing and/or turbine housing in a typical turbine structure).
• sidewalls of the inlet 9 need not be formed by discreet nozzle rings as with the embodiments of Figs. 3 and 5. Accordingly, although in the description below reference numerals 32 and 33 are conveniently used to identify sidewalls of a turbine inlet 9, these are not to be considered limited to the nozzle rings 32 and 33.
• the turbine nozzle comprises three inlet baffles 38, but as mentioned above there may be more or less inlet baffles in alternative embodiments of the invention.
• embodiments with only one or two inlet baffles are effective in significantly increasing the efficiency of a turbine inlet in which the moving component used to vary the inlet size is a cylindrical sleeve surrounding the vane array.
• embodiments with more than three baffles may be advantageous in some embodiments. In some applications, such as for instance turbocharger applications, it is expected that 3 to 6 baffles would be appropriate.
• baffles need not be axially equi-spaced across the width of the inlet 9, and in the case of a single baffle this need not be located mid-way between side walls of the inlet 9.
• the axial spacing between any two adjacent baffles, or between a baffle and an adjacent side wall of the inlet may increase or decrease from one axial side of the inlet to the other, or may first increase and then decrease, or vice versa.
• the axial space between the adjacent baffles and between any baffle and a side wall of the inlet may reduce/increase across the inlet 9 so that as the inlet is progressively closed by the cylindrical sleeve, the axial width of any exposed inlet passages 39 reduces/increases.
• each of the inlet baffles comprises a radially extending wall of constant thickness so that opposing surfaces of each baffle lie in a radial plane.
• facing surfaces of each baffle are parallel both to one another and to the facing surfaces of the nozzle rings 32 and 33 which defined the side walls of the annular inlet 9.
• the opposing surfaces of any given baffle need not be parallel to one another and/or need not lie in a radial plane, and/or need not be parallel to the facing surface of an adjacent baffle or inlet side wall.
• one or both of the opposing surfaces of a single inlet baffle may lie on a frusto-conical surface of revolution about the turbine axis.
• Such surfaces may be parallel with one another, or may angle in opposing directions.
• adjacent baffles may have facing surfaces which are parallel to one another or which lie at an angle to one another.
• the inlet side walls e.g. nozzle rings 32 and 33
• An inlet baffle may have a uniform axial thickness, or may have a thickness which varies across its radius.
• a baffle may have a narrowing axial thickness with decreasing radius.
• an inlet baffle may taper or may have a radial cross section which is has an aerofoil shape similar to that of a conventional inlet vane. Examples of some of the possible alternatives described above are shown in Figs 7a to 7g. These Figures are a simplified radial cross-sections through a turbine inlet 9 comprising sidewalls 11 and 12, and baffles 38. Details of inlet vanes 37 are omitted from some of the figures for simplicity.
• Fig 7a illustrates an embodiment comprising an annular inlet 9 defined between side walls 32 and 33 and comprising a nozzle having three baffles 38a-38c.
• baffle 38c is much closer to side wall 33 than to the neighbouring baffle 38b.
• the spacing of baffles 38a and 38b, and the spacing of side wall 32 and baffle 38a is greater than the spacing between baffle 38c and side wall 33.
• the axial dimension of inlet passage defined between baffle 38c and side wall 33 is less than an axial dimension of either of the inlet passages defined between sidewall 32 and baffle 38a or between baffle 32a and baffle 32b respectively.
• Fig 7b is a modification of the structure shown in Fig 7a, in which the side wall
• the side wall 32 could be angled in a similar way, and in some embodiments both side walls 32 and 33 may be angled so that both sides of the annular inlet 9 taper inwardly.
• Fig 7c illustrates an embodiment including three inlet baffles 38a-38c which have progressively increased spacing across the inlet 9, so that as the sleeve 30 is moved to close the inlet the axial width of the inlet passages 39 increases.
• the inlet nozzle comprises 5 baffles 38a-38e. As can be seen, in cross-section the baffles have a "fan" arrangement.
• the central baffle 38c which is mid way between inlet side walls 32 and 33, lies in a radial plane, but nozzle rings 38a, 38b, and baffles 38d and 38e are inclined so that they each lie on a frusto-conical surface with the effect that the inlet passages 39 tend to converge towards the central inlet baffle 38c.
• the effect is to define a tapering nozzle which has a maximum width defined between the nozzle ring 38a and the nozzle ring 38e, and which narrows with decreasing radius. In other words, the nozzle tapers inwardly.
• a similar effect could be achieved by dispensing with nozzle rings 38a and 38e and inclining the side walls 32 and 33 instead.
• baffles 38 In Fig 7e, two inlet baffles 38 are shown which taper inwardly. The tapering of the baffles is exaggerated for clarity, and only two baffles are shown to avoid complication, but it would be appreciated that in alternative embodiments there may be only one, or three or more baffles. The vanes are omitted for clarity.
• Fig 7f is a modification of the embodiment shown in Fig 7e, in which the baffles 38 have an airfoil type cross-section.
• the baffles are again simple uniform thickness annular rings, but in this embodiment each of the rings lies on parallel frusto-conical surface so that the baffles 38 are angled with respect to side walls 32 and 33, but are parallel to one another. In the illustration the baffles angle away from the inboard side wall 32 with decreasing radius. In an alternative embodiment the baffles could be angled in the opposite direction to that shown. If baffles at each axial end of the inlet contact the sidewalls 32 and 33 they may effectively constitute nozzle rings defining the maximum width of the inlet 9.
• the inlet vanes may have any suitable configuration, and may for instance have substantially the same aerofoil configuration of conventional inlet vanes or any alternative configuration selected to define a particular arrangement and configuration of inlet passages 39. That is, since the vanes and inlet baffles together define the configuration and orientation of the inlet passages 39, a wide variety of different inlet passage configurations can be achieved by appropriate design of the configuration and orientation of the individual nozzle vanes or inlet baffles, and moreover the designs can be such that there may be a variety of differently configured inlet passages within a single nozzle assembly.
• the efficiency of the turbine inlet may vary as the sleeve moves to different positions, and in particular may be greater at positions in which the free end of the sleeve is aligned with one of the baffles than when it is positioned between baffles.
• the actuator and/or control system for the sleeve may be configured so that the sleeve only moves in a step-wise manner between fully open and closed (including any "over-open” or "over-closed") positions and positions corresponding to the location of some or all of the baffles, and does not move to locations between adjacent baffles. The effect of this is to provide an inlet with a plurality of discreet sizes between a maximum and minimum. This may provide efficiency advantages, and may allow a lower cost actuator to be used.
• baffles may be desirable to locate baffles at particular axial positions corresponding to sleeve positions (i.e. inlet sizes) which are optimum for certain pre-determined operating conditions of the turbine.
• positions for a turbocharger turbine might correspond to preferred inlet widths for operation at peak engine torque, rated engine speed and freeway cruise point.
• the power generating engine may be operated at fixed loads and/or speeds with no need to allow for continuous adjustment of the turbine inlet width.
• baffles can be placed at positions corresponding to the optimum inlet widths for the particular operating conditions required, and the sleeve operated to move only between positions corresponding to the positions of the or each baffle.
• each inlet vane may be viewed as comprising axially adjacent inlet vane portions separated by the inlet baffles.
• each vane 37 may be considered to comprise portions which are axially aligned so that they are equivalent to a single vane extending across the full width of the inlet 9.
• the sleeve 30 is axially movable between an open position and a closed position.
• the open position in which there is a gas flow path through the inlet 9, between a free end of the sleeve (the end of the sleeve to the right in the figure) and a first inlet sidewall 33.
• the gas flow path through the inlet may be through at least one of the axially offset inlet passages.
• a closed position an example of which is shown in the figure
• the size of said gas flow path through the inlet 9 between the free end of the sleeve 30 and the inlet sidewall 33 is reduced compared to that when the sleeve is in the open position.
• the sleeve 30 moves in a direction towards inlet sidewall 33 when the sleeve 30 is moved from the open position towards the closed position.
• the sleeve 30 shown in figure 7a is in a closed position.
• the axial distance between any part of the free end of the sleeve (the end to the right as shown in the figure) and the inlet sidewall 33 is less than each of the respective axial distances between at least one of the inlet passage walls (in this case the baffles 38a, 38b and 38c) and the inlet sidewall 33.
• the nozzle assembly has three inlet passage walls (in this case baffles).
• the nozzle assembly may have any appropriate number of inlet passage walls.
• the number of inlet passage walls (which define axially adjacent inlet passages) is two or more.
• the axial distance between the free end of the sleeve 30 and the inlet sidewall 33 is less than the axial distance between each of baffles 38a and 38b and the inlet sidewall 33.
• the axial distance between the free end of the sleeve 30 and the inlet sidewall 33 is substantially the same as the axial distance between the baffle 38c and the inlet sidewall 33. This is because in the closed position of the sleeve 30 shown in figure 7a the sleeve is located such that the free end of the sleeve 30 is substantially axially aligned with the position of the baffle 38c.
• a closed position of the sleeve 30 may be such that the sleeve is substantially axially aligned with any of the inlet passage walls (e.g. baffles).
• a closed position of the sleeve may be such that the sleeve is not axially aligned with an inlet passage wall (e.g. baffle) and instead, the free end of the sleeve partially blocks an inlet passage defined by at least one of the inlet passage walls.
• the sleeve 30 is located past two inlet passage walls (baffles 38a and 38b). This is because the axial distance between the free end of the sleeve 30 and the inlet sidewall 33 is less than the axial distance between each of baffles 38a and 38b and the inlet sidewall 33.
• the sleeve in a closed position of the sleeve, may be located past any appropriate number of inlet passage walls. For example, the sleeve may be located past one, two, three or more inlet passage walls.
• the sleeve in a closed position of the sleeve, may be located past no inlet passage walls (such that the axial distance between the free end of the sleeve and the inlet sidewall is greater than the respective axial distance between each of the inlet passage walls and the inlet sidewall). In other embodiments, in a closed position of the sleeve, the sleeve may be located past all of the inlet passage walls (such that the axial distance between the free end of the sleeve and the inlet sidewall is less than the respective axial distance between each of the inlet passage walls and the inlet sidewall).
• the annular sleeve 30 has a free end (that which is to the right in the figure) which has an end face 30f which is generally flat.
• the end face 30f generally lies on a plane which is perpendicular to the turbine axis.
• the axial distance between any portion of the end face 30f and the inlet sidewall 33 is substantially constant. In other embodiments this need not be the case.
• the end face 30f may not be generally flat, i.e.
• the axial distance between a first portion of the end face 30f and the inlet sidewall 33 is different to the axial distance between a second portion of the end face 30f and the inlet sidewall 33.
• the end face 30f may have a circumferential profile which is generally wave shaped.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between at least one of the inlet passage walls and the first inlet sidewall.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between any number of the inlet passage walls and the first inlet sidewall.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be less than each of the respective axial distances between at least two or at least three inlet passage walls and the first inlet sidewall.
• the axial distance between at least a portion of the free end of the sleeve and the first inlet sidewall may be greater than each of the respective axial distances between any of the inlet passage walls and the first inlet sidewall.
• the sleeve 30 extends past both of inlet passage walls (baffles) 38a and 38b.
• Baffle 38b is located within the inlet 9 such that the axial distance between the baffle and inlet sidewall 33 is slightly less than substantially 50% of the axial distance between the inlet sidewalls 32 and 33.
• the sleeve in a closed position, may extend past at least one inlet passage wall (for example a baffle) which is located such that the axial distance between the inlet passage wall and inlet sidewall 33 is substantially 50% of the axial distance between the inlet sidewalls 32 and 33. In other embodiments, in a closed position, the sleeve may extend past at least one inlet passage wall (for example a baffle) which is located such that the axial distance between the inlet passage wall and inlet sidewall 33 is substantially between 50% and 40%, between 40% and 30%, between 30% and 20%, between 20% and 10%, between 10% and 5% or between 5% and 0% of the axial distance between the inlet sidewalls 32 and 33.
• at least one inlet passage wall for example a baffle
• Providing a inlet passage wall which is located such that the axial distance between the inlet passage wall and the inlet sidewall is substantially 50% or less of the axial distance between the inlet sidewalls has been found in some embodiments to increase the performance of the turbine and/or improve control of the gas flow through the inlet.
• FIG. 7a Another way of considering the relative positioning of the sleeve in a closed position and the inlet passage walls (baffles) as shown in figure 7a is that at least one inlet passage wall (in this case baffle 38b) is closer to the inlet sidewall 33 than it is to inlet sidewall 32.
• Inlet sidewall 33 is the sidewall towards which the sleeve moves when it moves from the open position to the closed position (i.e. when the sleeve moves to reduce the size of the inlet 9).
• the free end of the sleeve 30 is closer to inlet sidewall 33 than the inlet passage wall (baffle 38b) is to the inlet sidewall 33.
• the sleeve 30 and inlet passage walls 38a-38c of the embodiment shown in figure 7a are configured such that the sleeve contacts the inlet passage walls. More specifically, a radially inboard surface of the sleeve contacts a radially outboard portion of the inlet passage walls.
• the sleeve 30 may contact at least one of the inlet passage walls 38a-38c as it moves between open and closed positions, such that the at least on inlet passage wall helps to guide the movement of the sleeve.
• the sleeve may substantially not contact one or more of the inlet passage walls that the sleeve is past when the sleeve is in the closed position.
• the sleeve may be mounted such that gas may pass between at least one of inlet passage walls (that the sleeve is past) and the sleeve when the sleeve is in the closed position.
• the sleeve may not contact any of the inlet passage walls when it is in a closed position.
• Figs. 3 to 6 one possible modification of the embodiment of Figs. 3 to 6 is illustrated in Figs. 8a - 8c, and the same reference numerals are used where appropriate.
• vanes 37 are not continuous across the full width of the inlet 9, but rather vanes defining each of the annular arrays of inlet passages 39a - 39d have different radial extents. Whilst the leading edges of all of the vanes 37 lie on the same outer radius, the radius of the trailing edges of the vanes differ, in that the radial position of the trailing edge of each annular array of vanes decreases progressively from the first annular array 39a to the fourth annular array 39d. In addition, it can be seen that the inlet baffles 38a - 38c have a greater radial extent than at least some of the vanes 37 (in the illustrated embodiment it is greater than that of any of the vanes).
• each of the baffles 38a - 38c has the same radial dimension but this may not be the case in other embodiments.
• embodiments in which the baffles extend closer to the turbine wheel than the vanes may include embodiments in which the vanes all have the same radial extent.
• the axial spacing of the inlet baffles 38a - 38c is irregular so that whilst the width of the annular arrays of inlet passages 39b and 39c is the same, the axial width of the annular array 39a is greater than that of 38b and 38c, and the axial width of annular array 39d is less than that of axial arrays 38b and 38c.
• Figs. 8b and 8c show the vanes having different radial extents, and different swirl angles (that is the vanes visible in 8c are swept forwards to a greater extent than the vanes shown in Fig. 8b, and as such have a greater swirl angle).
• the present invention therefore provides a great degree of flexibility in optimising various features of the nozzle to particular requirements and efficiency profiles.
• there may be eight vanes in the array 39d twelve vanes in each of the arrays 39b and 39c, and 15 vanes in the array 39a.
• the swirl angle may be greatest in the array 39d and decrease progressively to the array 39a.
• minimising turbine high-cycle fatigue i.e. minimising the forcing function on the blades
• optimising or otherwise tailoring the efficiency and swallowing capacity of the turbine e.g. providing low efficiency at wide inlet openings which is useful in some applications such as e.g. EGR engines as described below.
• the arrays of inlet channels 39c and 39d are less able to stimulate vibration and fatigue in the turbine blades because the hub end of the turbine leading edge is more rigidly connected to the turbine hub (by virtue of it being closer to the turbine wheel back face).
• the vane arrays 39c and 39d may have a reduced clearance with respect of the turbine wheel (as illustrated) to boost efficiency given that this may not result in any significant vibration/fatigue problem as the turbine blades are more rigidly supported in this region.
• increasing the swirl angle of the vanes in the array 39d can offer a slight efficiency increase when the sleeve is at nearly closed positions (in which the leading edge of the sleeve 30 extends beyond the location of the inlet baffle 38c). This would have the additional effect of reducing the rate that the cross-sectional flow area changes as a function of sleeve motion, when the sleeve is nearly closed, which allows the actuator to control the cross-sectional flow area more precisely.
• each inlet baffle is annular and as such extends around the full circumference of the inlet 9.
• Each inlet baffle may however be considered to comprise an annular array of adjacent baffle portions defined between adjacent inlet vanes (or vane portions).
• the baffle "portions" of each baffle 38 are aligned to define the respective annular baffle.
• FIGs 9a to 9f and 10a to 10d are schematic radial views of un-rolled portions of the circumference of the respective embodiments corresponding to the views shown in Figs 2 and 5 for example.
• Figure 9a illustrates an embodiment in which inlet vane portions 37a-37d extend between adjacent inlet baffles 38 and between in the baffles 38 and side walls 32 and 33. No single inlet vane 37 is continuous across a baffle 38, with the effect that individual inlet passages 39 are arranged in circumferentially staggered annular arrays 39a-39b (there is circumferential overlap between axially adjacent passages 39).
• Figure 9b is a modification of the embodiment shown in Figure 8a, in which some vanes 37 do extend across the full width of the inlet 9, whereas other vane portions extend only between neighbouring baffles 38 or between a baffle 38 and enabling inlet wall 32/33.
• Fig 9c illustrates an embodiment of the invention in which inlet vanes 37 extend from the side walls 32 and 33 respectively, but in which no single inlet vane 37 extends the full width of the inlet 9.
• the effect in this case is to create four annular arrays of circumferentially adjacent in the passages 39a-39b, wherein the passages adjacent each side wall 32 and 33 have a rectangular cross-section and the passages 39b and 39c define between the baffles 38 have a generally square cross-section.
• Fig 9d illustrates an embodiment in which inlet vanes 37 extend only half way across the full width of the inlet 9, in this case extending from side wall 32 to a central inlet baffle 38b.
• inlet vanes 37 extend only half way across the full width of the inlet 9, in this case extending from side wall 32 to a central inlet baffle 38b.
• there only two annular arrays of inlet passages 39a and 39b whereas the "arrays" of 39c and 39d are each replaced by a single annular passage way 39c and 39d respectively.
• baffle separating them will require support. This could for instance be in the form of at least three small axially extending struts spaced around the turbine inlet between that central baffle and a neighbouring baffle or a side wall.
• a single vaneless space 19c between one of the side walls 32 or 33 and the annular arrays of passages may be very beneficial.
• the flow range of the variable geometry turbine can be considerably increased.
• the radially outboard inlet of the vaneless space may be axially wider than the radially inboard outlet (not illustrated).
• inventions of Figures 9e and 9f also comprise at least one annular inlet passage absent any vanes.
• there is a single inlet baffle 38 and vanes 37 extend from side wall 32 to the inlet baffle 38, but do not extend from the inlet baffle 38 to the side wall 33. This creates a first annular array of adjacent inlet passages 39a and a single annular inlet passage 39b.
• Figure 9f is an extreme example of the embodiments shown in Fig 9e, in which there is only a single vane 37 shown which extends from side wall 32 to the single inlet baffle 38.
• circumferentialiy distributed gas passages may for instance be appropriate for some applications of the invention, such as for instance heavy duty engine turbocharger applications. In other embodiments as many as 40 circumferentialiy distributed gas passages perhaps be appropriate, for instance for light duty engine turbocharger applications.
• 75 or more circumferentialiy distributed gas passages may be desirable (due to the lower exhaust temperatures and absence of gas pulsations). For very large turbines operated at low temperatures, low turbine pressure differentials, low gas speeds, and in the absence of gas pulsations and temperature variations, 100 circumferentialiy distributed gas passages may appropriate.
• the number of circumferentially distributed gas passages may generally be between 8 and 100. In other embodiments there may be between 12 and 100, or between 18 and 100 (perhaps 23 and 100, possibly 26 and 100 or conceivably 30 to 100). According to one embodiment of the invention, there may be provided two axially divided annular arrays of gas passages, each annular array having between 12 and 100 circumferentially distributed gas passages.
• vanes can vary from those illustrated in Figs. 9a-9f.
• Figures 10a to 10d show embodiments in which vanes 37 extend across the full width of the inlet 9, but at least one or more inlet baffles extend only a part way around the circumference of the inlet.
• Fig 10a illustrates an embodiment of the invention comprising a single inlet baffle 38 which extends around the full circumference of the inlet 9 (in this case midway between the side walls 32 and 33), and inlet baffle portions 38a and 38c which extend between other pairs of vanes 37 (which extend across the full width of the inlet 9).
• Fig 10b differs from the embodiment of Fig 10a in that there are two baffles 38a and 38d which extend around the full circumference of the inlet 9, but where baffle 38c is split into discontinuous baffle portions extending between every other pair of vanes 37.
• Figure 10c is an embodiment in which there is no single inlet baffle extending the full circumference of the annular inlet 9, rather inlet baffles 38a-38c comprise baffle portions extending between respective pairs of inlet vanes 37.
• the inlet baffle portions 38b are circumferentially staggered relative to the inlet baffle portions 38a and 38c.
• the individual inlet passages 39 are axially staggered, in that there is axial overlap between circumferentially adjacent passages 39.
• Fig 10d shows another example of a nozzle which has no single inlet baffle extending the full circumference of the annular inlet 9. Moreover, this embodiment shows how the spacing between inlet baffle portions extending between one pair of vanes may differ to that between the baffle portions extending between an adjacent pair of vanes.
• Figs 9 and 10 have generally regular arrays of inlet passages 39. However, this need not necessarily be the case.
• Fig 11 schematically illustrates an embodiment in which there is no single inlet baffle extending around the full circumference of the inlet, and no single inlet vane extending across the full width of the inlet. In this case the passage array is very irregular. In practice this specific pattern may not be particularly desirable, but it is included to illustrate the extent of variation that can be achieved (subject to manufacturing suitability) with some embodiments of the present invention.
• vanes or vane portions of the various embodiments of the invention described above may have any suitable cross-sections or configurations.
• the vanes may have a relatively conventional airfoil configuration.
• Increasing the thickness of the leading edge of the vanes offers higher tolerance to any variations in the incident angle of gas flow impinging on the vanes. That is, depending on the flow/pressure in the turbine volute the direction that gas will impinge on the vanes can vary. If gas hits a simple sheet structure at an angle it may cause the gas flow on the lee-side to separate off from the sheet leaving a vortex/turbulent area which greatly reduces efficiency.
• the configuration and/or arrangement of the vanes may vary in order to produce inlet flow passages 39 of a desired configuration.
• the inlet nozzle structures it may not therefore always be possible to view the inlet nozzle structures as comprising discernable inlet vanes in the conventional sense or even vane portions.
• the turbine nozzle comprises at least two axial spaced annular arrays of inlet passages.
• a single axial "array" may in fact comprise only one circumferential inlet passage.
• each annular array will comprise many inlet passages circumferentially spaced (e.g. adjacent) around the annular inlet.
• annular arrays of circumferentially spaced inlet passages 39 in different ways.
• Figs 12a to 12d show the embodiment of Fig 9d, but with axially spaced annular arrays of circumferentially spaced in the passages 39 identified in different ways.
• Fig 12a four annular arrays of inlet passages 39a-39d are identified.
• the inlet passages of the first array 39a have differing axial widths, but are adjacent one another.
• the inlet passages 39b of a second array each have the same axial width but are staggered relative to one another, and are not always adjacent one another.
• a third annular array of circumferentially spaced inlet passages 39c is identified which have the same axial width and position, but are not adjacent one another.
• a fourth annual array of circumferentially spaced inlet passages 39d corresponds to the first array 39a.
• Fig 12b identifies only two annular arrays of spaced inlet passages 39a and 39b. In this case, the inlet passages in each annular array are neither circumferentially nor axially adjacent one another.
• Fig 12c two different annular arrays of circumferentially spaced inlet passages 39a and 39b are identified.
• the inlet passages 39a of the first array are actually circumferentially adjacent inlet passages 39b of the second array, the axial spacing being achieved by an overlap in the axial dimension of the passages of each array. That is to say, the inlet passages 39b have a greater axial width than the inlet passages 39a so that at least a portion of each inlet passages 39b is axially spaced from the inlet passages 39a.
• Fig 12d shows another approach to identifying two axially spaced annular arrays of inlet passages 39a and 39b. In this case the passages 39a and 39b are axially adjacent one another, but the passages 39 of each array are not circumferentially adjacent.
• each inlet passage 39 has a generally rectilinear cross section.
• alternative cross sections are possible, such as for instance diamond shaped or hexagonal cross- sections as shown in Figs 13 and 14 defined by inlet walls 50.
• the nozzle structure clearly comprises a plurality of inlet passages 39.
• FIGs 13 or 14 one approach to identifying two distinct axially spaced annular arrays of circumferentially spaced passages, 39a and 39b is shown.
• the inlet passages in each annular array identified are circumferentially adjacent one another.
• adjacent annular arrays which are spaced axially across the inlet overlap one another to a degree. That is, a portion of each individual inlet passage 39b of the second annular array axially overlaps a portion of each inlet passage 39a of the first annular arrays. It is believed that such nozzle structures will further smooth any tendency for the turbine efficiency to have a "stepped" characteristic with varying inlet size.
• Figs 15 and 16 show the same embodiments as Figs 13 and 14 but illustrate a different approach to identifying axially spaced annular arrays of inlet passages 39a and 39b. In this case, in each embodiment two annular arrays of inlet passages which are axially spaced but which do not axially overlap are identified.
• inlet passages is governed by the configuration of the walls defining them, and that the nozzle structure may be designed such that there are individual inlet passages within the nozzle structure with a different configuration to that of other inlet passages within the same nozzle.
• a variation of the "honeycomb" embodiment of Figs 13 and 14 is for instance illustrated in Fig 17.
• inlet walls 50 again define generally hexagonal inlet passages 39 but in this case the array is somewhat irregular.
• One particular approach to identifying examples of two axially spaced annular arrays of inlet passages 30a and 39b is illustrated.
• the inlet nozzle structure comprises a plurality of inlet passages including at least one inlet passage spaced circumferentially and axially respectively from two other inlet passages, or indeed spaced both circumferentially and axially from each of the other two inlet passages.
• the spacing may be such that at least some of the passages are adjacent one another, and there may be axial and/or circumferential overlap between at least some of the passages.
• Fig 18 shows the embodiment of Figs. 14 and 16 described above.
• a first inlet passage 60 is circumferentially spaced from a second inlet passage 61 and is axially spaced from a third inlet passage 62. In this case the passages are adjacent to one another.
• a single inlet passage 63 is circumferentially spaced from an inlet passage 64 and axially spaced from an inlet passage 65. Here the passages are not adjacent.
• Inlet passages 60 and 61 can for instance be considered to comprise a first pair of circumferentially spaced inlet passages (as well as axially spaced by virtue of their axial overlap), and inlet passages 60 and 62 can be considered to comprise a second pair of inlet passages that are axially spaced, with the single inlet passage 60 common to both pairs.
• inlet passage 63 and 64 can be considered to comprise a first pair of inlet passages which are circumferentially spaced but not adjacent and inlet passages 63 and 65 can be considered to comprise a second pair of inlet passages which are axially spaced (and in this case also circumferentially spaced), in this case a single inlet passage 63 being common to both pairs.
• inlet passages 60 and 63 can for instance be considered to comprise a first pair of circumferentially spaced inlet passages, and inlet passages 64 and 65 can be considered to comprise a second pair of axially spaced inlet passages.
• Fig 19 shows how the structure shown schematically in Fig 14 can be constructed by pressing together axially adjacent baffles, four of which 78a-78d are identified in the figure.
• Each of these baffles is an annular ring but is circumferentially corrugated along the lines of a "wavy washer” and are aligned “out of phase” (circumferentially staggered) so that hexagonal inlet passages 39 are defined between adjacent baffles.
• the corrugations or waves could take a variety of forms including for instance sinusoidal and diagonal or "V" shapes, or any other shape appropriate to define the required configuration of inlet passages 39.
• each of the baffles 80 is corrugated, in other embodiments it may be desirable to place non-corrugated (e.g. strictly radial) baffles between one or more pairs of corrugated baffles to modify the configuration of the inlet passages 39 and certain axial locations across the inlet.
• individual corrugated baffles 80 need not have the same depth of corrugation.
• the baffles 80 can be pressed together in such a way as to have greater or smaller areas of contact between baffles 80 to that illustrated in figures 17 to 18 to again vary the configuration of the inlet passages.
• the contact area may vary across the radius of the nozzle structure to define individual inlet passages 39 which have a corresponding varying cross sectional area.
• adjacent baffles are aligned in anti-phase so that every other baffle 70 is directly aligned. This creates a honeycomb like structure in which axially adjacent inlet passages 39 are precisely aligned along the axis of the turbocharger. As illustrated in Figs.
• FIG. 20a and 20b some of the flow channels may be blocked to tailor efficiency in regions corresponding to certain inlet widths. For instance in Figs. 20a and 20b part-hexagonal channels at the axial ends of the nozzle are shown blocked out. In the case of Fig. 20b, the axial width of the channels in these regions is reduced which may be beneficial in reducing vibration on the blade when these channels are exposed to the inlet flow.
• Embodiments of the invention illustrated for example in Figs 3, 4a-4b, 7a-7g, 23-25 and 27a-27d each show an turbine inlet structure in which the sleeve 30 slides around the outside diameter of the nozzle structure, so that the sleeve acts to block/unblock inlet passages 39 at their upstream ends.
• the cylindrical sleeve may be located on the inside diameter of the nozzle so that it opens and closes inlet passages 39 at their downstream ends adjacent the turbine wheel.
• Figs 21a to 21 c show a modification of the embodiment of the invention illustrated in Figs 3 and 4a-4b, wherein a modified sleeve 130 slides across the inlet passage 9 downstream of inlet passages 39 so that it slides between the nozzle and turbine wheel.
• Other details of this embodiment of the invention are substantially the same as those shown and described in relation to Figs 3 and 4a-4b and like reference numerals are used where appropriate.
• first and second sleeves may have the same axial extent across the width of the inlet 9, or one of the two sleeves may extend further than the other at least some positions, so that in such positions the overall axial width of the annular inlets differs from its upstream to its downstream openings.
• the two sleeves could be coupled together (or integral) for actuation as a unit, or may be independently arranged and actuated.
• Embodiments of the invention described above show the sleeve 30 and 130 extending across the annular inlet 9 from the bearing housing side of the turbine wheel.
• the sleeve may extend across the annular inlet 9 from the turbine housing side of the wheel.
• the sleeve and actuating mechanism can be housed in the turbine housing rather than in the bearing housing. Examples of such embodiments of the invention are shown in Figs 32a and 32b, and 33a and 33b. Actuating the sleeve from the turbine side can be beneficial for mitigating high cycle fatigue of the turbine blades, because when the sleeve is nearly closed, exposing just one ring of inlet passages. When the sleeve is closed from the turbine side, then ordinarily it closes towards the bearing housing side, and towards the rear of the turbine wheel - which is where the blade is most robustly supported by the turbine back face.
• alternative embodiments of the invention may comprise two parallel sleeves, one on the inside diameter and one on the outside diameter, which may be arranged and controlled to move together or independently of one another, and may have different lengths.
• Figs. 22a and 22b show two possible arrangements for a sleeve 30 including a piston ring seal 00 adjacent the free end of the sleeve 30 to prevent gas flow between the sleeve 30 and a nozzle assembly in the accordance with the invention, indicated generally by reference 101.
• the nozzle assembly 101 may have any of the possible configurations according to the present invention described above.
• the sleeve may be mounted such that gas may pass between the sleeve and the nozzle assembly.
• the sleeve may be mounted such that there is a gap between the sleeve and at least one of the annular baffles.
• the sleeve may have an inner diameter which is greater than the outer diameter of at least one of the annular baffles.
• the flow path 38g passes through a radial gap between the sleeve 30 and baffle 38b of the nozzle assembly 34.
• the flow path 38g is such that once the gas has passed through the gap between the sleeve 30 and baffle 38b, the gas flows through the inlet 9 towards the turbine wheel.
• any other appropriate gap between the sleeve and the nozzle assembly (which defines a gas flow path between the nozzle assembly and the sleeve) may be used.
• Figure 7c the gap between the sleeve and the baffles 38a-38c has been exaggerated for clarity.
• the gap between the sleeve and the nozzle assembly may be such that it permits gas to flow between the nozzle assembly and the sleeve in a direction which is generally opposite to the direction in which the sleeve moves when it moves towards the inlet sidewall so as to reduce the size of the inlet.
• the gap between the sleeve and the nozzle assembly may be such that it permits gas to flow between the nozzle assembly and the sleeve in a direction which is generally radially inwards, towards the turbine wheel.
• the nozzle assembly and sleeve may be configured such that there is a gap between all of the baffles and the sleeve (e.g. the baffles all have an outer diameter which is less than the inner diameter of the sleeve).
• the nozzle assembly and sleeve may be configured such that there is a gap between only some of the baffles and the sleeve.
• those baffles for which there is not a gap between the nozzle and the sleeve may be such that they generally contact the sleeve.
• such baffles which abut the sleeve may guide the movement of the sleeve as it varies the size of the inlet. It has been found that in some embodiments, provision of a gap (and hence a gas flow path) between the sleeve and the nozzle assembly may improve the performance of the turbine.
• Nozzle structures in accordance with the present invention may be configured to provide varying efficiency for different inlet widths (i.e. corresponding to different positions of the sleeve or sleeves).
• baffles may be unequally spaced across the axial width of the inlet.
• the sleeve is capable of moving to positions between the location of baffles, there may be greater inefficiency at such an intermediate position between two relatively widely spaced baffles than between two relatively closely spaced baffles.
• the ability to tailor the efficiency of the nozzle in this way may have a number of applications.
• baffle spacing or otherwise increase the axial size of the inlet passages 39 in regions of the inlet corresponding to closed or relatively closed positions of the sleeve. That is, using a given number of baffles there may be advantages in arranging the baffles closer together near to the fully closed position. For any given number of baffles, this may increase efficiency in relatively closed positions of the sleeve.
• turbocharger In embodiments in which the turbine is part of a turbocharger, the turbocharger might be part of a turbocharged combustion engine, such as a compression ignition (diesel) engine, or a gasoline direction injection (GDi) engine for example.
• a turbocharged combustion engine such as a compression ignition (diesel) engine, or a gasoline direction injection (GDi) engine for example.
• Such applications could include more than one turbocharger including a turbine according to the present invention.
• Other possible applications include fuel cell turbochargers or turbines.
• the turbine inlet volute may be a divided volute.
• a turbocharger turbine with a volute divided into more than one chamber, each volute chamber being connected to a different set of engine cylinders.
• the division is usually an annular wall within the volute separating the volute into axially adjacent portions. It may also be possible to divide the volute circumferentially so that different arcuate portions of the volute deliver gas to different arcuate portions of the turbine inlet.
• the turbine of the present invention has been illustrated in the figures using a single flow volute, however it is applicable to housings that are split axially, whereby gas from one or more of the cylinders of an engine are directed to one of the divided volutes, and gas from one or more of the other cylinders is directed to a different volute of the turbine housing. It is also possible to split a turbine housing circumferentially to provide multiple circumferentially divided volutes, or even to split the turbine housing both circumferentially and axially.
• an axially or circumferentially split volute can for instance be distinguished from the axially and circumferentially spaced gas inlet passages of the present invention.
• the latter relate to a nozzle structure arranged to accelerate exhaust gas from the volute towards the turbine, and also possibly to adjust or control the swirl angle of the gas as it accelerates.
• straight inlet gas passages are in principle possible, generally they are curved so as to control the gas swirl angle efficiently.
• the gas inlet passages may also distinguished from divided volutes in that the former receive gas from the volute (or divided volute), and split the gas into an array of paths.
• divided volutes receive gas from the exhaust manifold, and generally from differing cylinders of an engine so as to retain the gas velocity in gas pulses resulting from individual engine cylinder opening events.
• a divided volute transmits the gas to the annular inlet, while the gas inlet passages of the present invention accept gas from the volute.
• baffle(s) axially dividing the gas inlet passages would generally be distinct from the wall(s) axially dividing the volutes.
• a wall dividing two circumferentially spaced volutes could extend radially inwards to further serve as one of the vanes (again provided that the sliding sleeve operates at the inner diameter of the gas inlet passages).
• a volute dividing wall could extend radially inward and adjacent to the sliding sleeve, so the sleeve is radially inboard of the volute dividing wall, but outboard of the gas inlet passages.
• Such an arrangement could beneficially mitigate the loss of gas velocity in gas pulses experienced in a single volute turbine, and might also assist in guiding the sliding sleeve to mitigate the possibility of it becoming misaligned and consequently jamming.
• the turbine inlet may be formed as a contiguous element with an exhaust manifold.
• a wide range of control strategies may be implemented to control the sliding sleeve described herein.
• the range of possible control strategies includes all those already described in the literature with respect to controlling conventional variable geometry mechanisms, especially sliding vane mechanisms used on automotive turbochargers.

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  • 2010-10-06 EP EP10776113A patent/EP2486260A2/de not_active Withdrawn
  • 2010-10-06 CN CN201080055342.3A patent/CN102782259B/zh not_active Expired - Fee Related
  • 2010-10-06 BR BR112012007837A patent/BR112012007837A2/pt not_active Application Discontinuation
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