阅读说明：本技术 用于涡轮机器的叶片和护罩 (Blade and shroud for a turbomachine ) 是由 马修·威廉·艾得华 西蒙·大卫·摩尔 克里斯多夫·帕里 安德鲁·沙利文 保罗·高希 M·R 于 2019-05-15 设计创作，主要内容包括：提出了一种用于涡轮机器的涡轮机,其中,在涡轮机叶轮的进气口处,叶片(407)从喷嘴环(405)延伸穿过护罩(6)中的狭槽。喷嘴环(405)和护罩(6)可绕涡轮机的旋转轴线相对旋转至少0.1度。在使用中,喷嘴环(405)和护罩(6)相对旋转,以使叶片(407)的一侧与狭槽的一个表面紧密接触,以防止气体在叶片和狭槽表面之间泄漏。为此目的,喷嘴和狭槽的相应表面可被配置为彼此紧密贴合。如果护罩和喷嘴环(405)存在不均匀的热膨胀,则喷嘴环(405)和护罩可以相对旋转,以从狭槽的边缘抽出叶片(407)以减轻它们之间的压力。(A turbine for a turbo machine is proposed in which, at the inlet of the turbine wheel, vanes (407) extend from a nozzle ring (405) through slots in the shroud (6). The nozzle ring (405) and shroud (6) are relatively rotatable about the axis of rotation of the turbine by at least 0.1 degrees. In use, the nozzle ring (405) and shroud (6) are rotated relative to each other so that one side of the vanes (407) are in close contact with one surface of the slots to prevent gas leakage between the vanes and the slot surfaces. To this end, the respective surfaces of the nozzle and the slot may be configured to closely conform to one another. If there is uneven thermal expansion of the shroud and nozzle ring (405), the nozzle ring (405) and shroud can be rotated relative to each other to withdraw the vanes (407) from the edges of the slots to relieve the pressure therebetween.)

1. A turbomachine, comprising:

(i) a turbine wheel, having an axis,

(ii) a turbine housing for defining a chamber for receiving the turbine wheel for rotation of the turbine wheel about the axis, the turbine housing further defining an inlet port, and an annular inlet passage from the inlet port to the chamber,

(iii) an annular shroud defining a plurality of slots and surrounding the axis; and

(iv) a nozzle ring supporting a plurality of vanes extending from the nozzle ring parallel to the axis and projecting through respective ones of the slots;

the shroud and nozzle ring are located on opposite sides of the inlet passageway and are rotatable relative to each other about the axis by an angular amount of at least 0.1 degrees.

2. The turbine of claim 1, wherein at least one of the shroud and the nozzle is rotatable relative to the turbine housing about the axis by at least 0.1 degrees, and the other of the shroud and the nozzle is rotatable relative to the housing about the axis by an amount less than 0.1 degrees.

3. A turbine according to claim 1 or claim 2, wherein the nozzle ring and shroud are relatively rotatable about the axis of the turbine by at least 0.3 degrees, at least 0.5 degrees, at least 1 degree or at least 2 degrees.

4. A turbine according to any preceding claim, further comprising an actuator for displacing one of the nozzle ring or shroud relative to the other, the actuator being mounted on the turbine housing and coupled to said one of the nozzle ring and shroud by a coupling mechanism which allows relative rotation of said one of the nozzle ring or shroud about said axis by at least 0.1 degrees relative to the actuator.

5. The turbomachine of claim 4 wherein the coupling mechanism comprises at least one guide coupler, each guide coupler comprising:

(i) a first element secured to the actuator or the one of the nozzle ring or shroud, an

(ii) A second element fixed with the other of the actuator or the one of the nozzle ring and shroud and arranged to move within a limited area defined by the first element, the area being dimensioned to allow circumferential rotation of the second element relative to the first element about the axis by at least 0.1 degrees.

6. The turbomachine of claim 5 wherein the first element defines at least one control surface extending in a circumferential direction about the axis, and the second element is arranged to move along a path defined by the control surface.

7. A turbine according to any preceding claim, wherein the nozzle ring is rotatable relative to the turbine housing about the axis by at least 0.1 degrees.

8. The turbomachine of claim 7 wherein the shroud is retained on the turbine housing and the turbomachine includes a limiting element that abuts a circumferentially facing surface of the shroud and limits rotation of the shroud about the axis.

9. The turbine of claim 8, wherein the restraining element is provided as a pin element protruding from the turbine housing, the shroud having a wall defining a gap accommodating the pin element.

10. The turbine of claim 8 or claim 9, wherein the pin element comprises a substantially flat surface for limiting movement of an opposing surface of the shroud.

11. A turbine according to any preceding claim, wherein the shroud is rotatable relative to the turbine housing about the axis by at least 0.1 degrees, and the shroud comprises a plurality of gas interaction elements upstanding from a platform surface of a surface of the shroud, each gas interaction element comprising at least one wall surface arranged to generate, in use, a rotational force due to gas flow against the gas interaction element.

12. The turbine of claim 11, wherein the surface of the shroud opposes the nozzle ring.

13. The turbine of claim 11 or claim 12, wherein each gas interaction element is disposed proximate an edge of a respective one of the slots.

14. The turbomachine of claim 13 wherein, in use, each gas interaction element is proximate to a suction portion of the slot surface of the respective slot and defines a wall surface facing the respective slot and a wall surface facing away from the respective slot.

15. A turbine according to claim 14, wherein no gas interaction element is provided adjacent an edge of one of the slots, which in use is a high pressure portion of the slot surface.

16. The turbine of any one of claims 11 to 15, wherein each gas interaction element comprises a wall surface that is an axial extension of a portion of an inwardly facing surface of the slot.

17. The turbine of any one of claims 11 to 16, wherein each gas interaction element is elongate.

18. A turbine according to any one of claims 11 to 17, wherein the ridge elements are connected together by rib elements upstanding from the surface of the shroud.

19. The turbine according to claim 18, wherein the rib element comprises a radially inward inner edge of the ridge element and/or a radially outward outer edge of the ridge element, and the ridge element is joined at its ends to the inner edge and/or the outer edge.

20. The turbine of any preceding claim, wherein each of said vanes is spaced from said axis by a nozzle radius;

each of the slots has an inwardly facing slot surface, and each of the vanes has:

axially extending vane surfaces comprising (i) a vane outer surface facing the outer surface of the respective slot, and (ii) an opposing vane inner surface facing the inner surface of the respective slot, and

a midline between the blade inner surface and the blade outer surface and extending from the first end of the blade to the second end of the blade;

a blade surface comprising conformal portions extending along at least 15% of a length of the centerline and facing respective conformal portions of the slot surface, wherein respective profiles of the conformal portions of the blade surface and the slot surface differ from each other by no more than 0.35% of the nozzle radius at room temperature.

21. The turbine of claim 20, wherein at room temperature, said conformal portion of said blade surface has a profile that differs from said profile of said conformal portion of said slot surface by no more than 0.3% of said nozzle radius over their respective lengths.

22. The turbine of claim 20 or 21, wherein at room temperature the conformal portion of the blade surface and the conformal portion of the slot surface are positionable to have a gap therebetween along their respective entire lengths of no more than 0.2% of the nozzle radius.

23. The turbine of claim 22, wherein at room temperature, said conformal portions of said blade surfaces and said conformal portions of said slot surfaces are positionable to have a gap therebetween along their respective entire lengths of no more than 0.1% of said nozzle radius.

24. The turbine of claim 23, wherein at room temperature, said conformal portions of said blade surfaces and said conformal portions of said slot surfaces are positionable to have a gap therebetween along their respective entire lengths of no more than 0.05% of said nozzle radius.

25. The turbine of claim 24, wherein at room temperature, said conformal portions of said blade surfaces and said conformal portions of said slot surfaces are positionable to remain in contact along their respective substantially entire lengths.

26. The turbine of any one of claims 20 to 25, wherein the blade inner surface extends between two convex end portions of the blade, and the conformal portion of the blade surface comprises a portion of a first one of the convex end portions of the blade surface.

27. A turbine according to any preceding claim, wherein the shroud is retained on the turbine housing, the turbine further comprising an annular retaining ring provided on a radially inward edge of the shroud, the retaining ring being positioned to inhibit gas entering the inlet passage from a side of the shroud remote from the inlet passage.

28. A turbocharger comprising a turbine according to any preceding claim.

29. A shroud for a turbine according to any one of claims 1 to 27, the shroud comprising a plurality of gas interaction elements upstanding from a platform surface of a surface of the shroud, each gas interaction element comprising at least one wall surface arranged to generate, in use, a rotational force due to gas flow against the gas interaction element.

30. The shroud of claim 29, wherein each gas interaction element is disposed proximate an edge of a respective one of the slots.

31. The shroud of claim 30, wherein each gas interaction element includes a wall surface that is an axial extension of a portion of the inner facing surface of the respective slot.

32. The shroud of any one of claims 29 to 31, wherein each gas interaction element is elongate.

33. A shroud as claimed in any one of claims 29 to 32 wherein the ridge elements are connected together by rib elements upstanding from the surface of the shroud.

34. A shroud as claimed in claim 33 wherein the rib elements comprise radially inward inner edges of the ridge elements and/or radially outward outer edges of the ridge elements and the ridge elements are joined at their ends to the inner and/or outer edges.

Technical Field

The present invention relates to a vane arrangement for location at an air inlet of a turbo-machine, such as a turbocharger.

Background

Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric (boost) pressure. Conventional turbochargers primarily include an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. 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 the intake manifold of the engine, thereby increasing engine power. The turbocharger shaft is typically supported by journal and thrust bearings (including a suitable lubrication system) located within a central bearing housing connected between the turbine and compressor wheel housings.

In known turbochargers, the turbine stage comprises a turbine chamber within which the turbine wheel is mounted; an annular inlet passage defined between facing radial walls arranged around the turbine chamber; an inlet disposed about the inlet passage; and an outlet passage extending axially from the turbine chamber. The passageway and the chamber communicate such that pressurized exhaust gas entering the inlet chamber flows from the inlet passageway to the outlet passageway through the turbine and rotates the turbine wheel.

It is known to improve turbine performance by providing vanes, known as nozzle vanes, in the inlet passage to deflect gas flowing through the inlet passage towards the direction of rotation of the turbine wheel. Each vane is generally laminar and is positioned to have a radially outer surface which is arranged to oppose the movement of the exhaust gas within the inlet passage, i.e. the radially inward component of the movement of the exhaust gas in the inlet passage is such as to direct the exhaust gas onto the outer surface of the vane which is then redirected into circumferential movement.

The turbine may be of a fixed or variable geometry type. Variable geometry turbines differ from fixed geometry turbines in that the geometry of the inlet passageway can be varied to optimise the airflow velocity over a range of mass flow rates, so that the power output of the turbine can be varied to suit varying engine demands.

In one form of variable geometry turbocharger, the nozzle ring carries a plurality of axially extending vanes that extend into the inlet and through corresponding apertures ("slots") in a shroud that forms a radially extending wall of the inlet. The nozzle ring is axially movable by an actuator to control the width of the air passageway. The movement of the nozzle ring also controls the extent to which the vanes project through the respective slots. The shroud is annular and surrounds the axis of rotation.

An example of such a variable geometry turbocharger is shown in fig. 1(a) and 1(b) (from US 8,172,516). The variable geometry turbine shown comprises a turbine housing 1, the turbine housing 1 defining an inlet chamber 2, gas from an internal combustion engine (not shown) being delivered to the inlet chamber 2. The exhaust gas flows from the inlet chamber 2 to the outlet channel 3 via the annular inlet channel 4. One side of the inlet passageway 4 is defined by the surface of a movable annular wall member 5 constituting the nozzle ring, while the opposite side is defined by an annular shroud 6, which annular shroud 6 covers an opening facing an annular recess 8 in the wall. The shroud 6 is an annular member (integral unit) defining a central bore and surrounding the axis of rotation. The facing wall is defined by a portion 28 of the turbine housing 1. The shroud 6 is connected to a portion 28 of the turbine housing 1 by a bracket 29 at the radially outer side of the shroud 6. In some arrangements, a retaining ring (not shown) is provided which is partially inserted into a radially outwardly facing recess in the carrier 29 and the radially outer portion of the retaining ring is retained by the portion 28 of the turbine housing 1.

Gas from the inlet chamber 2 to the outlet passage 3 flows through the turbine wheel 9 with the result that torque is applied to the turbocharger shaft 10 which is supported by a bearing assembly 14 which drives the compressor wheel 11. Rotation of the compressor wheel 11 about the axis of rotation 100 pressurizes ambient air present in the air inlet 12 and delivers the pressurized air to the air outlet 13, from which air outlet 13 it is fed to the internal combustion engine (not shown). The speed of the turbine wheel 9 is dependent on the speed of the gas passing through the annular inlet passage 4. For a fixed mass rate of gas flowing into the inlet passageway, the gas velocity is a function of the width of the inlet passageway 4, which can be adjusted by controlling the axial position of the nozzle ring 5. As the width of the inlet passage 4 decreases, the velocity of the gas passing through it increases. Fig. 1(a) shows the annular inlet channel 4 closed to a minimum width, while fig. 1(b) shows the inlet channel 4 fully open.

The nozzle ring 5 supports an array of circumferentially and equidistantly distributed vanes 7, each of the vanes 7 extending over the inlet passageway 4. The vanes 7 are oriented to deflect gas flowing through the inlet passage 4 towards the direction of rotation of the turbine wheel 9. As the nozzle ring 5 approaches the annular shroud 6 and the facing wall, the vanes 7 project through suitably configured slots in the shroud 6 and into the recesses 8. Each blade has an "inner" major surface closer to the axis of rotation 100 and an "outer" major surface further from the axis of rotation 100. The nozzle ring 5 and shroud 6 are both in a fixed angular position about the axis 100. The blade 7 is shown in fig. 1(a) and 1(b) as having a chamfered end (towards the right of the figure), but in most modern arrangements the blade is longitudinally symmetrical over its entire length, or is made up of two sections, each of which is longitudinally symmetrical but has a profile which differs from each other when viewed in the axial direction.

A pneumatically or hydraulically operated actuator 16 is operable to control the axial position of the nozzle ring 5 within an annular cavity 19 defined by a portion 26 of the turbine housing via an actuator output shaft (not shown) connected to a stirrup member (not shown). The stirrup member in turn engages axially extending guide rods (not shown) that support the nozzle ring 5. Thus, by appropriate control of the actuator 16, the axial position of the guide rods, and hence the nozzle ring 5, can be controlled. It should be understood that an electrically operated actuator may be used in place of the pneumatic or hydraulic actuator 16.

The nozzle ring 5 has axially extending inner and outer annular flanges 17, 18 respectively, the inner and outer annular flanges 17, 18 extending into an annular cavity 19, the annular cavity 19 being separated from the chamber 15 by a wall 27. Inner and outer sealing rings 20, 21, respectively, are provided to seal the nozzle ring 5 relative to the inner and outer annular surfaces of the annular cavity 19, while allowing the nozzle ring 5 to slide within the annular cavity 19. The inner sealing ring 20 is supported in an annular groove 22 formed in the inner surface of the cavity 19 and abuts the inner annular flange 17 of the nozzle ring 5, while the outer sealing ring 21 is supported in an annular flange 18 provided in the nozzle ring 5 and abuts the radially outermost inner surface of the cavity 19. It will be appreciated that the inner sealing ring 20 may be mounted in an annular groove in the flange 17 (rather than as shown) and/or the outer sealing ring 21 may be mounted in an annular groove provided in the outer surface of the cavity (rather than as shown). A first set of pressure balance apertures 25 are provided in the nozzle ring 5 within the vane passages defined between adjacent apertures, and a second set of pressure balance apertures 24 are provided outside the radius of the nozzle vane passages in the nozzle ring 5.

Note that in other known turbo machines the nozzle ring is axially fixed and an actuator is instead provided for translating the shroud in a direction parallel to the axis of rotation. This is referred to as a "moving shroud" arrangement.

In known variable geometry turbo machines that use vanes projecting through slots in the shroud, a gap is provided between the vanes and the edges of the slots to allow for thermal expansion of the vanes as the turbocharger becomes hotter. The blade and the slot have the same shape, viewed in the axial direction, but the blade is smaller than the slot. In a typical arrangement, the vanes are positioned with the axial centerline of each vane at the center of the respective slot such that the ratio of the distance from the centerline to the surface of the vane to the distance from the centerline to the edge of the respective slot is the same in all directions away from the centerline transverse to the axis of the turbine. The gap between the vane and the slot is typically set to at least about 0.5% of the distance of the vane center from the axis of rotation ("nozzle radius") around the entire periphery of the vane at room temperature (defined herein as 20 degrees celsius) (e.g., for a nozzle radius of 46.5mm, the gap may be 0.23mm or 0.5% of the nozzle radius). This means that if each of the blades is gradually thermally expanded perpendicular to the axial direction, all points around the periphery of the blade will simultaneously contact corresponding points on the slot. At all lower temperatures, there is a gap between the entire periphery of the vane and the edge of the respective slot.

Disclosure of Invention

The present invention is directed to a new and useful blade assembly for use in a turbomachine, and a new and useful turbomachine (particularly a turbocharger) incorporating the blade assembly.

In an earlier patent application (GB1619347.6, which was not published at the priority date of the present application), the present applicant proposed that in a turbomachine of a turbo machine in which the vanes project from the nozzle through slots in the shroud at the air inlet between the nozzle ring and the shroud, one "conformal" portion of the lateral surface (i.e. the surface comprising a direction parallel to the axis of rotation) of each vane substantially conforms to the shape of the corresponding "conformal" portion of the lateral surface of the respective slot at room temperature, so as to place the respective conformal portions of the surfaces relative to each other with only a small gap therebetween. This has the advantage that the gas flow between the corresponding conformal portion of the blade surface and the slot can be greatly reduced. This reduces leakage of gas from the nozzle ring into or out of the recess on the other side of the shroud. This leakage reduces the circumferential redirection of gas by the vanes and has been found to result in a significant loss in efficiency.

In such an arrangement, conformal portions of the blade surface and the slot surface may be positioned close to or even in contact with each other at low temperatures (e.g., room temperature). At higher temperatures, this contact can be maintained if the shroud and nozzle ring expand uniformly. However, uneven thermal expansion of the components of the turbine in use can cause the vanes and slots to compress against one another, making it more difficult to move the vanes axially relative to the slots. This effect can be reduced to some extent by any free play in the mounting of the shroud and nozzle ring which allows the vanes to retract from the inner surface of the shroud to prevent the respective surfaces from being forcibly pressed together. Any such free movement is not due to design, but rather to tolerances in the formation of the components. It varies among different turbo machines and the inventors have found experimentally that this freedom of movement allows relative rotation of the nozzle ring relative to the shroud of significantly less than 0.1 degrees, for example up to 0.05 degrees.

Generally, the present invention proposes a turbine (e.g. a turbocharger) which allows the nozzle ring to move relative to the shroud by a greater angular amount (at least 0.1 degrees) in the circumferential direction to relieve pressure between the vanes and the edges of the respective slots.

The present invention embodies a turbine comprising:

(i) a turbine wheel, having an axis,

(ii) a turbine housing for defining a chamber for receiving a turbine wheel for rotation about an axis, the turbine housing further defining an air inlet, and an annular inlet passage from the air inlet to the chamber.

(iii) An annular shroud defining a plurality of slots and surrounding an axis; and

(iv) a nozzle ring supporting a plurality of vanes extending from the nozzle ring parallel to the axis and projecting through respective ones of the slots;

the shroud and nozzle ring are located on opposite sides of the inlet passageway and are rotatable relative to each other about an axis by an angular amount of at least 0.1 degrees.

Both the shroud and the nozzle are supported within the turbine housing, but in one possibility at least one of the shroud and the nozzle may be rotatable relative to the turbine housing about an axis by at least 0.1 degrees. Typically, the other of the shroud and nozzle is mounted on the turbine housing such that it can rotate angularly about the axis relative to the housing by an amount less than 0.1 degrees.

The concept of arranging the nozzle ring to be rotatable relative to the shroud is referred to herein as "clocking".

Typically, the nozzle ring and shroud are relatively rotatable about the axis of the turbine by at least 0.3 degrees, at least 0.5 degrees, at least 1 degree, at least 1.5 degrees or at least 2 degrees.

We refer to the connection between the turbine housing and the shroud or nozzle ring as a coupling mechanism, which allows relative rotation of the shroud or nozzle ring relative to the turbine housing by at least 0.1 degrees, respectively.

In one possibility, the coupling mechanism may substantially fix the axial position of the shroud/nozzle ring, and/or substantially maintain the center of the shroud/nozzle on the axis of the turbine wheel, but may allow the shroud/nozzle to rotate relative to the turbine housing about the axis of the turbine wheel. The coupling mechanism may allow the shroud/nozzle ring to rotate relative to the turbine housing over a fixed angular range of at least 0.1 degrees, or a free angle (i.e., an infinite angular amount). In the latter case, rotation of the shroud/nozzle ring relative to the turbine housing may be limited only by interaction between the vanes of the nozzle ring and the slots of the shroud.

The turbine preferably further comprises an actuator for axially displacing one of the nozzle ring or shroud relative to the other. The actuator may typically be mounted on the turbine housing. In one possibility, the coupling mechanism couples the nozzle ring or shroud to the turbine housing via an actuator.

In a first possibility, a coupling mechanism connects the actuator to the nozzle ring while allowing rotational movement of the nozzle ring relative to the actuator. The shroud may be generally fixed together (i.e., mounted in a fixed positional relationship) with a casing of the turbomachine. The turbine housing may include a limiting element that abuts a circumferentially facing surface of the shroud and limits rotation of the shroud about the axis. The restriction element may for example be provided as a pin element protruding from the turbine housing, the shroud having a wall defining a gap containing the pin element. In use, the circumferentially facing surface of the wall may abut the pin element to limit rotational movement of the shroud.

The coupling mechanism may comprise at least one guide coupling. Each guide coupler may include: (i) a first element fixed with one of the nozzle ring and the actuator, and (ii) a second element fixed with the other of the nozzle ring and the actuator and arranged to move within a restricted area defined by the first element. The region is sized to allow circumferential rotation of the second element relative to the first element about the axis by at least 0.1 degrees. For example, the first element may define a control surface (e.g. an edge of an elongate circumferential slot) extending in a circumferential direction about the axis, and the second element is arranged to move along a path defined by the control surface. The length of the path may be at least 0.1 degrees. In one variation, the region may be defined by an aperture that is large enough to allow rotational movement, but does not include a control surface to guide rotation along the path.

In a second possibility, a coupling mechanism connects the actuator to the shield while allowing rotational movement of the shield relative to the actuator.

A rotation mechanism is provided for causing relative rotation of the shroud and nozzle ring about the axis in a predetermined sense. In principle, the rotation mechanism may comprise an externally controllable actuator. In other possibilities, a rotation mechanism may be provided, which comprises at least one elastic spring element and/or at least one magnetic element. The rotation mechanism may cause the lateral surfaces of the vanes and the corresponding lateral surfaces of the corresponding slots to abut one another, thereby reducing gas flow between those surfaces. This is particularly, but not exclusively, useful if the lateral surfaces of the vanes and the respective slots closely conform in shape to each other.

Preferably, the rotation mechanism comprises a gas interaction element on one of the shroud and nozzle arranged to generate, in use, a rotational force due to the flow of gas against the gas interaction element. The vanes themselves may act as gas interaction elements for urging the nozzle ring to rotate relative to the turbine housing so that no additional rotational mechanism is required.

Where the gas interaction elements are provided on the shroud, one or more of the gas interaction elements may be located on a surface of the shroud opposite the nozzle ring.

If the surface of the shroud comprises a platform surface (e.g., a surface transverse to the axis of rotation), the one or more gas-interacting elements may, for example, comprise respective ridge elements of the surface of the shroud that are upstanding from the platform surface (e.g., farther from the nozzle ring than the platform surface). One or more of the ridge elements may be elongate. One or more ridge elements may comprise a top surface substantially transverse to the axial direction, and/or comprise two opposing wall surfaces of the axial direction. Typically, a rotational force is generated due to the flow of gas over one of the wall surfaces. In addition, rotational forces are generated by the flow of gas relative to other surfaces of the shroud (e.g., the inwardly facing surfaces of the slots that extend between the surfaces of the shroud and define the edges of the slots). The net rotational force on the shroud is the sum of the rotational forces applied by the gas to all surfaces of the shroud.

At least one respective ridge element may be provided for one or more slots (e.g., each of the slots) of the shroud. The corresponding ridge element for the slot may have a shape matching the shape of the edge of the slot. Respective ridge elements for the slots may be provided near the edges of the slots (e.g. in the range of less than 250 microns or less than 100 microns from the slot about the axis of rotation). In practice, the axially extending surface of the raised portion may be substantially flush with the inwardly facing surface of the slot defining the slot edge. For example, it may be a continuous axial extension of a portion of the inwardly facing surface of the slot (i.e., the protruding slot surface).

Some or all of the ridge elements may extend radially inward from the radially inward end of the slot, for example to engage an inner edge portion of the shroud surface upstanding from the platform surface and surrounding a radially inward axis of rotation of the slot. Alternatively or additionally, some or all of the ridge elements may extend radially outward from the radially outward end of the slot, for example to engage (e.g., be integrally formed with) an outer edge portion of the shroud surface that is upstanding from the platform surface and that surrounds the radially outward axis of rotation of the slot. In this case, the ridge elements divide the platform surface of the shroud into respective portions of each of the slots.

The inner and/or outer edges may be considered rib elements (i.e., upstanding elements that extend circumferentially to engage a plurality of ridge elements). The ridge members may be connected together by further rib members upstanding from the surface of the shroud. The rib elements may make the ridge elements easier to form with high accuracy, since it may not be necessary to form corners at the ends of the ridge elements if the respective rib elements are connected to one or both ends of the ridge elements.

As mentioned above, it is preferred that a portion of the surface of each vane conforms to an opposing portion of the surface of the respective slot, wherein the rotation mechanism pushes the two conformal portions of the respective surfaces together. In one particular expression of this concept, each of the vanes has an axially extending vane surface that includes (i) a vane outer surface facing an outer surface of the respective slot, (ii) an opposing vane inner surface facing an inner surface of the respective slot. The blade further comprises a mid-line between the blade inner surface and the blade outer surface, the mid-line extending from the first end of the blade to the second end of the blade. The blade surface comprises a conformal portion extending along at least 15% of the length of the mid-line and facing a corresponding conformal portion of the slot surface, wherein at room temperature the respective profiles of the conformal portion of the blade surface and the corresponding conformal portion of the slot surface differ from each other by no more than 0.35% of the nozzle radius, and preferably no more than 0.3%, 0.2% or even 0.1% of the nozzle radius.

The conformal portion of the blade surface may extend along at least 20%, at least 30%, at least 40%, at least 60%, at least 80% or at least 90% of the length of the mid-line.

In this document, the statement that two lines differ from each other by no more than a certain distance x is to be understood as meaning that the lines can be placed such that they do not cross and that no point along any of the lines is further than the distance x from the other line. The statement that the conformal portions of the blade surface and the slot surface differ from each other by no more than a certain distance x means that the conformal portions of the blade surface and the conformal portions of the slot surface are axially aligned with each other and appear as respective lines when viewed in the axial direction. In this view, the lines do not differ from each other by more than a distance x.

Preferably, at room temperature, the conformal portions of the vane surfaces and the corresponding conformal portions of the slot surfaces of the vanes may be positioned with a clearance along their respective entire lengths of no more than 0.35%, 0.3%, 0.2%, or even 0.1% of the nozzle radius therebetween (e.g., for a nozzle radius of 48.1mm, the clearance is no more than 0.17mm, no more than 0.1mm, or even no more than 0.05 mm). Thus, gas leakage between the vane inner surface and the slot inner surface can be reduced. If the conformal portion of the blade surface is short (e.g. at least 10% or 15% but not more than 30% or even not more than 20% of the mid-line length), the phase difference is preferably not more than 0.05% or even 0.02% of the nozzle radius (i.e. not more than 0.03mm or not more than 0.001mm for a nozzle radius of 48.1 mm). The phase difference may for example be in the range of 1 micron to 0.05mm, or even in the range of 1 micron to 0.025 mm.

Note that this is in contrast to the known vane and slot arrangement described above, in which the vanes and slots have the same overall shape when viewed in the axial direction, but have different dimensions at room temperature, such that each portion of the vane surface has a different radius of curvature than the nearest portion of the slot surface.

In some embodiments, the conformal portions of the blades may be positioned in contact with respective portions of the edges of the slot along substantially the entire length of the conformal portions. For example, there may be more than two points of contact between them, and the maximum distance of any point of the conformal portion of the blade surface from the slot surface is no more than 0.35%, 0.3%, or even 0.2% of the nozzle radius. For example, where the nozzle radius is 48.1mm, the vanes may be positioned such that the maximum distance of any point of the conformal portion of the vane surface from the slot surface is no greater than 0.17mm, 0.15mm or even 0.10 mm.

The conformal portion of the blade surface may comprise a portion of one of the convex end portions of the blade surface. If the conformal portion of the blade surface is located on the inner surface of the blade, this is typically a conformal portion at the leading edge of the blade. If the co-shaped surface is located on the outer surface of the blade, this is typically at the trailing edge of the blade. Preferably, the conformal portion of the blade surface comprises at least the portion of the convex end portion of the blade surface between the first major blade surface and the mid-line.

Drawings

Embodiments of the invention will now be described, for example purposes only, with reference to the following drawings, in which:

fig. 1 consists of fig. 1(a) and 1(b), fig. 1(a) being an axial cross-section of a known variable geometry turbine, fig. 1(b) being a cross-section of a portion of the turbine of fig. 1 (a);

FIG. 2 is an axial view of a nozzle ring that may be used in the known arrangement of FIG. 1;

FIG. 3 is an axial view of a shroud that may be used in the known arrangement of FIG. 1;

FIG. 4 illustrates the positional relationship between the nozzle ring of FIG. 2 and the shroud of FIG. 3;

FIG. 5 illustrates a first possible positional relationship between the bucket and the shroud in one embodiment of the present invention;

FIG. 6 illustrates a second possible positional relationship between the buckets and the shroud in one embodiment of the present invention;

FIG. 7 illustrates a third possible positional relationship between the buckets and the shroud in one embodiment of the present invention;

fig. 8 is composed of fig. 8(a) and 8(b), fig. 8(a) being an axial view of a vane arrangement in the first embodiment of the present invention, and fig. 8(b) being an enlarged view of a portion of fig. 8 (b);

FIG. 9 consists of FIG. 9(a), FIG. 9(b) and FIGS. 9(c) to 9(e), FIG. 9(a) being a perspective view of a portion of a first turbine housing usable with the embodiment of FIG. 8, FIG. 9(b) showing a pin element for insertion into a bore of the turbine housing of FIG. 9(a), and FIGS. 9(c) to 9(e) showing the combination of the turbine housing and shroud in cross-section, cross-section and axial views, respectively;

fig. 10 shows three variants of the embodiment of fig. 9. FIG. 10(a) is a perspective view of a portion of a second turbine housing that may be used in the embodiment of FIG. 8, FIGS. 10(b) and 10(c) are perspective views of a shroud for a turbine housing, and FIGS. 10(d) and 10(e) show a combination of a second turbine housing and a shroud in perspective and cross-sectional views, respectively; FIG. 10(e) shows the installation of a variation of the pin element of FIG. 9, and FIG. 10(f) shows the pin element in use; and fig. 10(g) shows a second variant of the pin element of fig. 9.

FIG. 11 consists of FIGS. 11(a) and 11(b) showing a shield in a second embodiment of the invention;

fig. 12 consists of fig. 12(a) to 12(c) showing a shield in a third embodiment of the invention; and

fig. 13 is composed of fig. 13(a) to 13(f), which show parts of shrouds in fourth to ninth embodiments of the present invention.

Detailed Description

Referring to fig. 2, a nozzle ring is shown that may be used in the known turbocharger of fig. 1. The nozzle ring is viewed from a position between the nozzle ring 5 and the shroud 6 to the right in the axial direction shown in fig. 1(a) (this direction is also referred to herein as "from the turbine end of the turbocharger").

The axis about which the turbine wheel 9 (not shown in fig. 2, but visible in fig. 1 (a)) and the compressor wheel 11 (also not shown in fig. 2, but visible in fig. 1 (a)) rotate is indicated at 100.

Viewed in this axial direction, the generally planar annular nozzle ring 5 surrounds an axis 100. The vanes 7 project in the axial direction from the nozzle ring 5. By defining a circle 70 centrally located on axis 100 and passing through the centre of the profile of the vane 7, we can define the nozzle radius 71 as the radius of the circle 70.

The gas moves radially inwardly between the nozzle ring 5 and the shroud 6. In some turbines, the radially outer surface of the blade 7 is a "high pressure" surface, while the radially inner surface of the blade 7 is a "low pressure" surface. In other turbines, these effects are reversed.

The nozzle ring 5 is moved axially by an actuator 16 (not shown in fig. 2, but visible in fig. 1 (a)) within an annular cavity (also not shown in fig. 2, but visible in fig. 1 (a)) defined by a portion 60 of the turbine housing. Each vane 7 is optionally longitudinally symmetrical (that is, its profile may be the same at all axial positions as viewed in the axial direction), although in some embodiments only a portion of the vane 7 is longitudinally symmetrical.

The actuator exerts a force on the nozzle ring 5 via two axially extending guide rods. In fig. 2, a portion 32 of the nozzle ring 5 is omitted so that the connection between the nozzle ring 5 and the first of the guide rods can be seen. The guide bar is not shown but is centred at the position marked 61. The guide bar is integrally formed with a bracket 33 (commonly referred to as a "foot"), which bracket 33 extends circumferentially from the guide bar to either side. The bracket 33 comprises two circular holes 62, 63. The face of the nozzle ring 5 facing away from the shroud 6 is formed with two bosses 34, 64 projecting from the nozzle ring 6. Each boss 34, 64 has a circular profile (viewed in the axial direction). Bosses 34, 64 are inserted into bores 62, 63, respectively, and bosses 34, 64 are sized such that boss 34 substantially fills bore 62, while boss 64 is narrower than bore 63. The connection between the bosses 34 and the apertures 62 fixes the circumferential position of the nozzle ring 5 relative to the bracket 33 (in a typical implementation, the relative circumferential movement of the nozzle ring 5 and shroud 6 about the axis 100 is no more than 0.05 degrees). However, if the guide rods are radially separated due to thermal expansion, the clearance between boss 64 and bore 63 allows the carrier 33 to rotate slightly about boss 34. Thus, the boss 34 is referred to as a "pivot".

The location at which the second of the guide rods is connected to the nozzle ring 5, seen in the axial direction, is shown at 31. The connection between the nozzle ring 5 and the second guide rods is due to the second brackets (not visible in fig. 2) being integrally attached to the second guide rods. A second bracket is attached to the rear surface of the nozzle ring 5 in the same manner as the bracket 33. The pivot of the second bracket is at position 35.

The holes 24, 25 are balancing holes provided in the nozzle ring for balancing the pressure. They are provided to achieve a desired axial load (or force) on the nozzle ring.

Facing the nozzle ring 5 is a shroud 6 as shown in fig. 3. Fig. 3 is a view from the nozzle ring 5 toward the shroud 6 (i.e., toward the right in fig. 1). The shroud defines a slot 30 (that is, a through hole) for receiving a respective one of the vanes 7. The edge of each slot is an inwardly facing transverse (i.e., transverse to axis 100) slot surface. Note that in fig. 7, the slots 30 are not shown as having the same profile as the vanes 7 of fig. 2, but generally the respective profiles do have substantially the same shape, although the size of the slots is larger than the size of the vanes.

Fig. 4 is another view in the axial direction from the nozzle ring 5 toward the shroud 6 (i.e., toward the right in fig. 1 (a)), showing representative vanes 7 inserted into respective representative slots 30. The vanes 7 have a generally arcuate (crescent-shaped) profile, although in other forms the vanes are generally planar. Specifically, the vanes 7 have vane inner surfaces 41 that are closer to the impeller. The vane inner surface 41 is generally concave in the axial direction, but may alternatively be planar. The vanes 7 also have a vane outer surface 42, the vane outer surface 42 being closer to the exhaust gas inlet of the turbine. Each of the blade inner and outer surfaces 41, 42 is a main surface of the blade. The vane outer surface 42 is generally convex in the axial direction, but may also be planar. The main surfaces 41, 42 of the blade 7 face in substantially opposite directions and are connected by two axially extending end surfaces 43, 44, which end surfaces 43, 44 have a radius of curvature, seen in the axial direction, which is smaller than the radius of curvature of either of the two surfaces 41, 42. The end surfaces 43, 44 are referred to as a leading edge surface 43 and a trailing edge surface 44, respectively.

In most arrangements, the vane outer surface 42 is arranged to oppose the movement of the exhaust gas in the inlet passage, i.e. the movement of the exhaust gas in the inlet passage causes the exhaust gas to be directed onto the vane outer surface. Accordingly, the blade outer surface 42 is typically at a higher pressure than the blade inner surface 41 and is referred to as a "high pressure" (or simply "pressure") surface, while the blade inner surface 41 is referred to as a "low pressure" (or "suction") surface. Corresponding portions of these opposing inwardly facing surfaces define the edges of slot 30 and are given the same corresponding names.

In some possible arrangements, the vane inner surface 41 redirects the airflow. In this case, the vane inner surface 41 is typically at a higher pressure than the vane outer surface 42 and is referred to as a "high pressure" (or simply "pressure") surface, while the vane outer surface 42 is referred to as a "low pressure" (or "suction") surface. Again, they are opposite the corresponding portions of the inwardly facing surface, which define the edges of the slot 30 and are given the same respective names.

Each blade 7 has a centre line 51, seen in the axial direction, which extends from one end of the blade to the other (half the distance between the inner and outer surfaces 41, 42 of the blade, seen in the axial direction) and which has both a radial component and a circumferential component. We refer to the slot surface that the vane inner surface 41 faces as the slot inner surface 46 and the slot surface that the vane outer surface 42 faces as the slot outer surface 47. As shown in fig. 4, there is a gap having a substantially constant width between the periphery of the vane 7 and the surface of the slot 30. The gap comprises four parts: between the vane inner surface 41 and the slot inner surface 46; between blade outer surface 42 and slot outer surface 47; and between the leading edge surfaces 43 and trailing edge surfaces 44 of the vanes and the respective leading portions 49 and trailing portions 59 of the slot edges. Together, surfaces 46, 47, 49 and 59 constitute inwardly facing slot surfaces that define the slot.

Turning to FIG. 5, a first possible positional arrangement between blades and shroud slots in a turbine is shown as one embodiment of the present invention. The turbine has the form shown in figures 1 and 2, with the difference being the shape and size of the vanes and/or slots in the shroud. In fig. 5, elements corresponding to those of fig. 1 to 4 are given reference numerals increased by 100. Thus, a representative vane 107 is depicted within the representative slot 130. The vane outer surface 142 faces the slot outer surface 147 and the vane inner surface 141 faces the slot inner surface 146. Alternatively, the vane 107 may be longitudinally symmetrical throughout its length (i.e., the profile is the same at all axial positions as viewed in the axial direction). In another possibility, only a portion of the vane 107 may be axially symmetric, e.g., including a portion insertable into the slot 130 when the vane 107 is in its most advanced position. In this case the blade part shown in fig. 5 is part of this axially symmetrical part of the blade. The vanes 107 are integrally formed with the nozzle ring 5 (e.g. by casting and/or machining) as a one-piece unit.

In contrast to the known vane of fig. 4, the vane 107 of fig. 5 has a relatively narrow gap between the vane inner surface 141 and the opposing slot inner surface 146. Instead, a wider gap exists between the vane outer surface 142 and the corresponding portion 147 of the slot outer surface 147. This means that exhaust gas entering the shroud recess 8 between the outer vane surface 142 and the slot outer surface 147 is largely prevented from exiting the shroud recess between the vane inner surface 141 and the slot inner surface 146.

To encourage this effect, the blade and slot surfaces are formed with conformal portions 145, the conformal portions 145 extending along at least about 15%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60% or at least about 80%, or even along at least 85% or 90% of the length of the midline 151. As shown in FIG. 5, the conformal portion 145 of the blade surface in FIG. 5 includes substantially all of the blade inner surface 141. The profile of the vane inner surface 141 (i.e., the shape as viewed in the axial direction) and the corresponding portion of the slot inner surface 146 are very similar to one another so that they can be placed against one another along the entire length of the conformal portion 145 with little (e.g., negligible) clearance therebetween. Specifically, at room temperature, the profile of vane inner surface 141 and the corresponding portion of slot inner surface 146 are such that they may be positioned against each other with a gap therebetween (e.g., transverse to centerline 151) of no greater than 0.35% of nozzle radius 71, and preferably no greater than 0.2% or 0.1% of nozzle radius 71. On average, over the conformal portion 145 of the blade surface, the clearance between the blade inner surface 141 and the slot inner surface 146 is no more than 20% or 10% of the clearance between the blade outer surface 142 and the slot outer surface 147. The vane leading edge surface 143 is spaced from a corresponding portion 149 of the inner surface of the slot 130.

Turning to FIG. 6, a second possible positional arrangement between the blades 207 and shroud 230 slots in a turbine of an embodiment of the present invention is shown. Elements having the same meaning as in fig. 5 are given the reference numeral increased by 100. The blade surface and the slot surface are formed with a conformal portion 245, the conformal portion 245 extending along at least about 90% of the length of the centerline 251. The conformal portion 245 of the vane surface in fig. 6 includes substantially all of the vane inner surface 241 and also includes a majority of the vane leading end surface 243 facing the slot leading edge surface 249. At room temperature, the profile of the blade inner surface 241 and the corresponding portion of the slot inner surface 246 are substantially the same within machining tolerances, so they may be placed opposite each other with substantially no gaps between them along the entire length of the conformal portion 245. There is a gap between the outer surface 242 of the blade 207 and the facing portion 247 of the slot 230.

Turning to FIG. 7, a third possible positional arrangement between the blades 307 and the shroud slots 330 in a turbine as one embodiment of the present invention is shown. In this arrangement, the conformal portion 345 of the vane 307 is located at the vane outer surface 342, and similarly, the conformal portion 345 of the slot 330 is located at the slot outer surface 347. The conformal portion 345 of the vane 307 comprises a majority of the outer surface 342 of the vane 307 that rests against the slot outer surface 347 along at least 90% of the length of the midline 351. It also includes a rear surface 344, the rear surface 344 being located on a corresponding portion 359 of the slot edge until a point where the midline 351 meets the rear surface 344 is located radially inward. This positional arrangement inhibits gas flow from the outer surface 342 to the inner surface 343 of the vane 307 by substantially preventing gas from leaking between the vane outer surface 342 and the slot outer surface 347.

In the positional relationship of fig. 5, 6, and 7, if there is uneven (differential) thermal expansion between the vanes 107, 207, 307 and the shroud (e.g., because they are made of different materials and/or are subjected to different temperatures), the conformal portions of the vanes 107, 207, 307 may be forced against the slot inner surfaces 146, 246 or the slot outer surfaces 347. The friction between them may then prevent axial movement of the blades relative to the shroud. However, even if the nozzle ring and shroud are mounted in a "fixed" angular position as in the system of fig. 1, there is some freedom of movement in the system (e.g. the nozzle ring may have some inherent freedom to rotate about axis 100 due to the nozzles 5 being coupled to the rods (as shown in fig. 2)), and we have found experimentally that this may be as high as 0.05 °. This will allow the vanes 107, 207, 307 to retract to some extent from the conformal portion of the slot surface. However, the extent of this retraction will be limited and may not be consistent from one turbine unit to another as it depends on the tolerances of the components. Thus, in embodiments of the invention (described below), the nozzle ring and shroud are arranged to be relatively rotatable at a large angle with respect to each other. However, the turbine is arranged to generate a rotational force that urges the respective conformal portions of the surfaces of the nozzle ring and slot together.

In particular, fig. 8 shows a nozzle ring in a first embodiment of the invention. Elements corresponding to elements of fig. 1-4 are given reference numerals incremented by 400. The nozzle ring of fig. 8 may again be used in a known system such as that of fig. 1, in which the vane arrangement is located within a cavity defined by a portion 60 of the turbine housing.

As in the nozzle ring of fig. 2, the nozzle ring 405 of the embodiment of fig. 8 comprises a plurality of circumferentially equally spaced axially extending vanes 407 for insertion into slots of a shroud 6 having the same appearance as the known shroud 6 of fig. 3. The vanes 407 and slots may have the profile and positional arrangement shown in either of fig. 5 or 6, such that conformal portions of the surface of one of the vanes 407 may rest against corresponding conformal portions of the edges of the corresponding slot, or have a small gap therebetween. The center of the blade 407 lies on a circle 470 having a radius 471, which is the nozzle radius.

As with fig. 2(a), fig. 8(a) shows the appearance of the vane arrangement as viewed in the axial direction from a position between the nozzle ring 405 and the shroud 6. With the known arrangement of fig. 2, the nozzle ring 405 is movable in either axial direction within an annular cavity (not shown, but having the same configuration as shown in fig. 1) defined by the portion 60 of the turbocharger housing by means of two axially extending guide rods by an actuator (not shown, but having the same configuration as shown in fig. 1), which is movable in either axial direction. The apertures 424, 425 in the nozzle ring 405 are balancing apertures provided in the nozzle ring 405 for balancing the pressure. They are provided to achieve a desired axial load (or force) on the nozzle. In use, in the arrangement shown in figure 1, exhaust gas moves radially inwardly in direction a towards the turbine wheel. Thus, the radially outer surfaces of the vanes 407 are high pressure surfaces, and their radially inner surfaces are low pressure surfaces. Thus, the exhaust gas exerts a force on the outer surface of the vane 407 which urges the vane to move in the clockwise direction of fig. 8 (a).

The connection between the nozzle ring 405 and the first guide rods is shown in fig. 8(a) by omitting the forward portions 432 of the nozzle ring 405 to expose brackets 433 ("feet") fixedly mounted on the first guide rods. The surface of the nozzle ring 405 facing away from the shroud 6 is formed with two bosses 434, 464 which project in the axial direction from the nozzle ring 405 in a direction away from the turbine wheel. Each of the bosses 434, 464 has a circular profile (viewed in the axial direction). The bracket 433 includes a circular hole 463 into which the boss 464 is inserted. Bore 463 has a larger radius than boss 464, thus allowing bracket 33 to rotate slightly about boss 34 if the guide rods are radially separated due to thermal expansion. Thus, the boss 34 is referred to as a "pivot".

Fig. 8(b) is an enlarged portion of fig. 8(a) showing that the bracket 433 includes an arcuate slot 436 instead of the circular aperture 62 of the known system of fig. 2. The arcuate slot 436 has a curved central axis extending in a circumferential direction about the axis 100. The boss 434 is inserted into the arc-shaped slot 436. The width of the arcuate slot 436 is only slightly greater than the diameter of the boss 434, transverse to the central axis, and therefore the edges of the slot provide control surfaces to guide the boss along a path. The connection between the bosses 434 and the apertures 436 fixes the radial position of the bosses 434, but allows relative circumferential movement of the nozzle ring 405 relative to the bracket 433. The amount of this circumferential movement is limited by the length of the arcuate slot. In typical implementations, the relative circumferential movement of the nozzle ring 405 and shroud 6 about the axis 100 is at least 0.1 degrees, and may be at least 1 degree, at least 1.5 degrees, and up to about two degrees. Note that in a variation, instead of the arcuate slots 436, the brackets 433 may include (e.g., circular) holes in which the bosses 434 move such that the combination of the bosses and holes allow relative circumferential movement of the nozzle ring 405 and shroud 6 by at least 0.1 degrees. The boss 434 remains within the area defined by the hole, but the edge of the hole does not limit the position of the boss 434 to a position on the path defined by the hole.

The connection between the nozzle ring 405 and the second guide rods is due to the second brackets (not visible in fig. 8) being integrally attached to the second guide rods and having the same shape as the brackets 433. The position of the second guide bar when viewed in the axial direction is shown as 431. The second bracket is attached to the rear surface of the nozzle ring 5 in the same manner as the bracket 433. The bosses of the second bracket are positioned to correspond to the bosses 434 of the bracket 433, as indicated at 435; the boss is located within a circumferentially extending arcuate slot of the second carrier such that the boss and slot are not relatively movable in a radial direction but are relatively movable in a circumferential direction. The length of the arcuate slot may be the same as the length of the arcuate slot 436.

Thus, the brackets 433 and bosses 434 together form a coupling mechanism that allows relative movement of the shroud 6 and nozzle ring 405 in the circumferential direction. However, the centers of the nozzle ring 405 and the shroud 6 remain on the axis 100, and the entire plane of each of the nozzle ring 405 and the shroud 6 remains generally transverse to the axis 100.

The vanes 407 are urged in this direction due to the force applied to the vanes 407 by the exhaust gas in the circumferential direction. The connection between the bracket 433 and the respective boss 434 allows this movement so that the inner surface of each vane 407 is pressed against the respective slot inner surface. The relative circumferential movement of the nozzle ring 405 and shroud is referred to as "clocking". This movement is possible because the bosses 434 slide within the slots 436 of the brackets 434 so that the nozzle ring 405 can move circumferentially even if the guide rods do not move. The shroud is in this case mounted so as to be immovable relative to the turbine housing.

Because, as explained above with reference to fig. 5 and 6, the conformal portions of the inner surfaces of the blades 407 have substantially the same profile (i.e., the same shape and the same dimensions) as the corresponding conformal portions of the inner edges of the respective slots, the blades 407 and slot edges are very close together, even substantially in contact, along the entire conformal portions of the blades 407. In particular, the conformal portion of the blade 407 may include the entire blade inner surface that is completely coincident with the corresponding portion of the slot inner surface.

This embodiment thus benefits from the force of the exhaust gas to ensure that the conformal portions of the blade surface are pressed against the corresponding conformal portions of the slot edges with little or no gap therebetween. This reduces or even eliminates gas leakage from the recess 8 between the conformal portion of the blade surface and the corresponding conformal portion of the edge of the slot.

If the blade 407 thermally expands, the blade may expand into a gap at the outer surface of the blade 407. This causes the nozzle ring 405 to move circumferentially (in a counterclockwise direction in fig. 8 (a)) relative to the shroud 6, and relative to the actuators 16 and guide rods. This movement is opposed by the gas pressure on the outer surface of the vane 407 which pushes the corresponding conformal portions of the surfaces of the vane and slot together. Thus, despite the uneven thermal expansion of the nozzle ring and shroud, a tight connection is maintained between the conformal portions of the vanes 407 and the edges of the respective slots without generating excessive forces therebetween.

As mentioned above, the first embodiment shown in fig. 8 may be used in a known turbocharger as shown in fig. 1. However, fig. 9 and 10 show portions of two corresponding novel turbines (e.g., of a turbocharger or other turbo-machine), in which the nozzle mechanism of fig. 8 may also be advantageously employed.

Specifically, fig. 9(a) shows a turbine housing 401 having a portion 428 for defining a recess 408 and for retaining an annular shroud 406 covering the recess 408. The portion 428 of the turbine housing 401 defines a bore 481 on its surface facing the bearing housing. The bore 481 is an opening having a cylindrical cavity with an axis of rotation that extends generally in an axial direction (i.e., parallel to the axis of rotation). Fig. 9(b) shows a cylindrical pin element 482 which may be inserted into the hole 481, e.g. so as to substantially fill it, the pin element 482 having an axis of rotation extending in an axial direction. The pin element 482 may be longer than the depth of the hole 481 and extend out of the hole 481.

Fig. 9(c) is a sectional view when the turbine housing 401 supports the shroud 406, and fig. 9(d) is a cut-away perspective view of the turbine housing 401 and the shroud 406. The bearing housing and nozzle ring are omitted in both views. The radially inner portion of the shroud 406 defines a cradle 429, the cradle 429 having an inner annular wall 483 and an outer annular wall 484. A retaining ring 485 is positioned between the annular walls 483, 484. The retaining ring 485 extends radially inward from the gap between the annular walls 483, 484 and is retained internally by an annular lip 486 of the turbine housing portion 428. It has been found that providing a retaining ring 485 radially inward of the shroud 406 may provide excellent resistance to gas leakage from the recess 408 into the inlet passage 404 at the radially inner edge of the shroud 406.

In the radially outer part of the shroud 406, a wall 487 is provided, which wall 487 extends in the axial direction away from the inlet channel 404.

Fig. 9(e) is a plan view of the shroud 406 viewed axially from the bearing housing direction. Wall 487 is at the back of shroud 406 and is therefore not visible in fig. 9(e), but its outline is indicated by line 491. Similarly, fig. 9(e) marks the location of pin element 482, although it is also located at the rear of shroud 406. The wall 487 extends around a majority of angular positions about the turbine axis, but the wall 487 includes a gap 489 between the circumferentially facing surfaces 488, 490 of the wall 487. When the shroud 406 is supported by the portion 428 of the turbine housing 401, the pin element 482 is located within a gap 489 in the wall 487. Thus, the pin element 482 securely prevents the shield 406 from rotating in a counterclockwise direction as shown in fig. 9 (a). Note that this is accomplished without the need for high tolerances in the shape of the shroud 406. This is because the exact extent of the gap 489 is not critical. If it is significantly larger (e.g., at least 50% larger) than the diameter of the pin element 482, the pin element 482 may be inserted therein when the shroud 406 is attached to the portion 428 of the turbine housing 1. Only the surface 488 of the shroud 406 impinges on the pin element 482.

Fig. 10 shows three variants within the scope of the claims of the embodiment of fig. 9 in fig. 10(a) - (e), fig. 10(f) - (g) and fig. 10(h), respectively. Turning first to fig. 10(a) - (e), elements having the same meaning as in fig. 9 are given the same reference numeral as they do, but with the letter "a". As shown in fig. 10(a), in this form of the turbine housing 401a, the portion 428a of the turbine housing 401a is formed with a shoulder 492 (instead of a bore). The shoulder 492 may be radially outward from the recess 408 a.

As shown in the perspective views of fig. 10(b) and 10(c), the shroud 406a is formed at its radially outer edge with a recess 493 for receiving the shoulder 492. Thus, the shroud 406 is prevented from rotating about the axis of rotation of the turbine. Fig. 10(d) is a perspective view of the shroud 406a mounted on the portion 428a of the turbine housing 401, showing the insertion of the shoulder 492 into the recess 493. Thus, in use, the shoulder 493 prevents rotation of the shroud 406 about the turbine axis. Thus, the shoulder 493 acts like the pin element 482 of the arrangement of fig. 9 as a limiting element of the turbine, which abuts a circumferentially facing surface of the shroud (the surface defining the recess 493) and limits rotation of the shroud 406a about the axis.

As in the arrangement of fig. 9, the shroud 406a is provided with an annular retaining ring 485a at its radially inner side. The retaining ring 485a may be inserted between two walls 483a, 484a of the cradle 429a defined by the radially inner portion of the shroud 406 a. The radially inner retaining ring 485a effectively prevents gas from leaking from the recess 408a into the inner passage 404 a.

Turning to fig. 10(f) - (g), another variation is shown. The cylindrical pin element 482 of fig. 9 is replaced by a pin element 482b as shown in fig. 10(f), which pin element 482b is comprised of two portions 495, 496. Each shown as a generally rectangular parallelepiped. Portion 496, shown larger than portion 495, defines a hole 497, which may be a generally cylindrical through hole. Portion 496 has a radius 498, such as a non-cylindrical surface, as described below.

Fig. 10(g) shows a pin element 482b for use with the shroud 406, which is generally the same as that shown in fig. 9 and therefore is denoted by the same reference numeral. Although the pin element 482 of fig. 9(b) extends axially out of the bore 481 in use, in the arrangement of fig. 10(g), the longest dimension of the pin element 482b extends radially. That is, portion 495 is radially inner and portion 496 is radially outer. The radially outer portion 496 has a greater circumferential width than the inner portion 495. The radially inner portion 495 is circumferentially recessed relative to the surface 498 of the radially outer portion 496. The second pin 499, shown in fig. 10(g) as viewed along its length axis, passes through the hole 497 and extends in the axial direction of the turbine into a hole in the turbine housing, which may be the hole 481 in fig. 9. Which secures the pin element 482b to the turbine housing.

In fig. 10(g), the shroud 406 is viewed from the rear (i.e., looking toward the nozzle ring). The radially outer portion 496 is located within the gap 489 and the surface 498 faces a surface 488 of the wall 487, which extends axially from the shroud 406. Thus, both surfaces 488 and 498 face in the circumferential direction. As shown in fig. 10(g), rotational movement of the shroud 406 in the clockwise direction is limited by the surface 488 of the pin element 482 b.

The surface 498 is substantially flat, thus reducing contact pressure as compared to the circular pin element 482. However, it is preferably not completely flat, but may be convex and slightly curved, e.g. with a radius of curvature much larger (e.g. 3 times larger) than the circumferential extent of the pin element 482 b. Thus, the contact between the surface 498 and the surface 488 is not at the corners of either element, but between the rounded surface 498 and the flat surface 488. In one variation, the surface 488 can also be rounded, or the only rounded surface. Note that the radially inner portion 495 of the pin element 482b radially inward of the wall 487 may abut against or be axially separated from the rear surface of the shroud 406. Its circumferential facing surface does not restrict the movement of the shroud. However, the inner portion 495 may increase the strength of the pin element 482 b.

Fig. 10(g) shows the installation of the pin element 482b during assembly of the turbine. The pin element 482b is held in a correspondingly shaped gap in the assembly tool 494 and is moved by moving the assembly tool 494 into position relative to the turbine housing portion 428. The pin 499 may then be threaded through the through hole 497 to secure the pin element 482b to the turbine housing.

Another variation is shown in fig. 10 (h). This variation includes a pin element 482c that is identical to pin element 482b of fig. 10(f), but omits the inner portion 495. One circumferential facing surface 498a of the pin element 482c is used to impart and limit movement of the surface 488 of the shroud 406 of fig. 9. The pin element 482c has the same cross-section (shape and size) in all planes parallel to the page. Thus, surface 498a includes straight lines that extend into the page, but the intersection of these lines with the page is curve 498 b. In other words, the surface 498a is generally planar, but more precisely a convex (non-circular) cylindrical surface having a radius of curvature that is much larger (e.g., 3 times larger) than the circumferential extent of the pin element 482 c. In fig. 10(h), pin element 482c is shown during assembly of the turbine, supported in an appropriately sized gap in assembly tool 494 a.

Turning to fig. 11(a), a shroud 506 of a second embodiment of the present invention is shown. This second embodiment is also a turbocharger having the general form of fig. 1, and the elements of this embodiment other than the shroud 506 and its coupling to the turbine housing are the same as in the known turbocharger of fig. 1, and therefore will be referred to herein by the same corresponding reference numerals. In particular, the nozzle ring 5 of the turbocharger may be as shown in fig. 2 and arranged for axial movement under the control of an actuator 16 as shown in fig. 1. Like the shroud 6 of the known turbocharger of fig. 1, the shroud 506 of the second embodiment is mounted in the turbine housing 1 in such a way that it is held in a fixed axial position (the same position shown in fig. 1) and its entire plane remains perpendicular to the axis of rotation 100. However, in contrast to the known arrangement of fig. 1, the coupling between the shroud 506 and the turbine housing 1 allows the shroud 506 to rotate freely about the axis of rotation 100 of the turbine wheel. Its rotation is limited only by interaction with the nozzle ring vanes.

The shroud 506 is viewed in perspective in fig. 11(a), looking at its face which faces away from the nozzle ring 5 in use. The shroud 506 is formed with a flat platform surface 561 transverse to the axis 100. The stage surface 561 is formed with a plurality of slots 530 as through holes. The platform surface 561 extends between the outer edge 563 and the inner edge 564. Each slot 530 is defined by an inwardly facing surface (i.e., having an edge that is an inwardly facing surface) that encompasses an axial direction at all points. In other words, the slot 530 has longitudinal symmetry in the axial direction.

The outer edge 563 is generally located where the shroud 506 is coupled to the turbine housing 1. For example, the outer edge 563 may be captured in an annular space defined between a circular surface of the turbine housing 1 and an annular plate (not shown) mounted to the turbine housing 1 such that the outer edge 565 is rotatable about the rotational axis 100 in the annular space.

Fig. 11(b) is an enlarged view of a portion of fig. 11(a) and shows that each slot 530 is provided with a respective ridge element 560, which ridge element 560 is upstanding from the platform surface 561 in an axial direction away from the nozzle ring 5. The ridge elements 560 extend along portions of the edges of the slot 530. The spine element 560 is elongated and curved. It extends between a rear end (radially inner) 562 and a front end (radially outer) 563. The ridge element 560 has a rectangular form as viewed in the direction of extension of the ridge element 560 (i.e., in the direction from the inner end 562 toward the outer end 563). It is defined between two wall surfaces 564, 565 extending in the axial direction 100, respectively, and a top surface 566 transverse to the axial direction 100. Wall surface 564 is located on a side of ridge element 560 facing slot 530. Each portion of wall surface 564 facing slot 530 is flush with a closest portion of the radially inner surface of slot 530, i.e. each portion of wall surface 564 and the respective closest portion of the radially inner surface of slot 530 form a continuous surface, wherein a line in the axial direction extends continuously over the portion of wall surface 564 and the respective closest portion of the inner surface of slot 530.

Each slot 530 is intended to receive a respective blade 7. The vanes 7 and corresponding slot surfaces are formed with conformal portions as shown in figures 5 and 6.

The turbocharger of the second embodiment is of the type in which the radially outer surfaces of the slots and vanes are the high pressure side and the radially inner surface is the suction side. In use, when the vane 7 is received in the slot 530, the ridge element 560 is on the side of the vane 7. The wall surface 564 faces the vane inner surface, and the portion of the slot surface closest to the wall surface 564 is the slot inner surface (suction surface). The flow of gas creates forces on the various surfaces of the shroud 506. In particular, in comparison to the conventional shield 6 of fig. 3, a rotational force is generated on the wall surface 564, which causes the shield 506 to rotate in a counterclockwise direction as shown in fig. 11(a), as indicated by the large arrow. Simulations we performed show that even without the ridge elements 560 there is a rotational force acting on the shroud 506 in the counter-clockwise direction, but when the vanes 7 are in a central position within the slots 530, the rotational force is increased by about 38% due to the ridge elements 560. When the ridge element is in this position, the efficiency of the turbine is only slightly increased (less than 1%) relative to known shrouds. However, this force causes the slot 530 and the vane 7 to adopt the arrangement shown in fig. 5 or 6. That is, due to the ridge elements 560, the respective conformal portions of the vanes 7 and the slots 530 are pushed together to inhibit or even prevent gas flow therebetween. In one of these two positions, the efficiency of the second embodiment would be significantly higher than if the ridge element 560 were not present.

Turning to fig. 12(a), a third embodiment of the present invention is shown as shield 606. This third embodiment is also a turbocharger having the general form of fig. 1, and the elements of this embodiment other than the shroud 606 and its coupling to the turbine housing are the same as in the known turbocharger of fig. 1, and therefore will be referred to herein by the same corresponding reference numerals. In particular, the nozzle ring 5 of the turbocharger may be as shown in fig. 2 and arranged for axial movement under the control of an actuator 16 as shown in fig. 1. Similar to the shroud 6 of the known turbocharger of fig. 1, the shroud 606 of the third embodiment is mounted in the turbine housing 1 so that it is held in a fixed axial position (the same position shown in fig. 1) and its entire plane remains perpendicular to the axis of rotation 100. However, as in the second embodiment of the invention, the coupling between the shroud 606 and the turbine housing 1 allows the shroud 606 to rotate freely about the axis of rotation 100 of the turbine wheel. Its rotation is limited only by interaction with the nozzle ring vanes.

The shroud 606 is shown in perspective view in fig. 12(a), which shows its surface facing away from the nozzle ring 5 in use. It is formed with a platform surface 612 that is flat and transverse to the axis 100. The platform surface 612 is formed with a plurality of slots 630 as through holes. Platform surface 612 extends between outer edge 663 and inner edge 664. Each slot 630 is defined by (i.e., has an edge that is) an inward-facing surface that encompasses the axial direction 100 at all points. In other words, slot 630 has longitudinal symmetry in the axial direction.

The outer edge 663 is generally the location where the shroud 606 is coupled to the turbine housing 1. For example, the outer edge 663 may be captured in an annular space defined between a circular surface of the turbine housing 1 and an annular plate (not shown) mounted to the turbine housing 1 such that the outer edge 663 is rotatable about the axis of rotation 100 in the annular space.

Fig. 12(b) is a view of a portion of the shroud 606 facing the nozzle ring in the axial direction, and fig. 12(c) and 12(d) are perspective views of respective portions of the same surface of the shroud 606, viewed from different respective directions. They show that each slot 630 is provided with a respective ridge element 631 upstanding from the platform surface 612 in an axial direction away from the nozzle ring 5. The ridge member 631 extends along a portion of the edge of the slot 630. The ridge member 631 is elongated and curved. It joins the outer edge 663 at the outer end and the inner edge 664 at the inner end. Thus, ridge member 631 divides platform surface 612 into various portions, one for each slot 630.

The ridge member 631 has a rectangular form, seen in the extension direction of the ridge member 631. It is defined between two wall surfaces 632, 633, each comprising an axial direction 100 at all points, and a top surface, transverse to the axial direction 100. Wall surface 633 is on a side of ridge member 631 facing slot 630. Each portion of wall surface 633 facing slot 630 is flush with a closest portion of the inner surface of slot 630, i.e., each portion of wall surface 633 and the respective closest portion of the inner surface of slot 630 form a continuous surface, wherein a line in the axial direction extends continuously over the portion of wall surface 633 and the respective closest portion of the inner surface of slot 630.

Each slot 630 is for receiving a respective blade 7. The vanes 7 and corresponding slot surfaces are formed with conformal portions as shown in fig. 5 or fig. 6.

The turbocharger of the third embodiment is of the type in which the radially inner surfaces of the slots and vanes are on the suction (low pressure) side and the radially outer surfaces are on the high pressure side. In use, when the vane 7 is received in the slot 630, the ridge member 631 is located on the low pressure side of the vane 7. The wall surface 633 faces the blade inner surface, and the portion of the slot surface closest to the wall surface 633 is the slot inner surface. The slot outer surface 635 is a pressure surface.

The flow of gas creates forces on the various surfaces of the shroud 606. In particular, a greater net rotational force (torque) is generated as compared to the conventional shield 6 of fig. 3, which causes the shield 606 to rotate in a counterclockwise direction, as shown by the large arrow in fig. 12 (a). A positive (counterclockwise) torque is generated on the slot pressure surface 635, the outer edge 663 and the wall surface 632. These torques are greater than the negative torques on the wall surface 633, slot suction surface and shroud plate extension tab 634. The net torque urges the slots 630 and vanes 7 to adopt the arrangement shown in fig. 5 or 6. That is, due to the ridge elements 631, the respective conformal portions of the vanes 7 and slots 630 are pushed together to inhibit or even prevent the flow of gas therebetween. The simulations we performed show that the net torque on the shroud is about 67% higher than the known shroud shown in fig. 3. The comparison is performed when the blade is in a centered position within the slot. Thus, the rotational force on the shield 606 is significantly greater than the rotational force of the shield 506 of the first embodiment. Even in this position, the efficiency of this embodiment is about 1% higher than conventional shrouds.

When the blades are in the angular position as shown in fig. 5 or 6, simulations show an increase in torque of 81% and an increase in turbine efficiency of 5.9%.

Turning to fig. 13, shields of six further embodiments of the present invention are shown in fig. 11(a) - (f), respectively. All of these embodiments are "moving shroud" type turbochargers, in which an actuator (not shown) is mounted on the turbine housing (not shown) to axially translate the shroud. Which replaces the actuator 16 of the turbocharger of fig. 1. It is well known that the actuator of a turbocharger of the "moving shroud" type is connected to the shroud by an arrangement similar to that of figure 2. That is, the shield is mounted on the guide bar using a bracket (foot) similar to the bracket 33. The axial position of the guide rod is controlled by an actuator.

Fig. 13(a) shows a shield of a fourth embodiment of the present invention. The shroud has the same appearance as the shroud of a conventional "moving shroud" turbine, which includes a plurality of slots 730 for receiving blades (not shown). Radially inward of each slot 730 is a low pressure surface. However, in the embodiment of fig. 13(a), in contrast to known "moving shroud" turbines, a coupling mechanism (not shown) is provided between the actuator and the shroud to allow the shroud to rotate about the circumferential axis of the turbine, i.e. perpendicular to the nozzle ring facing surface 708. Although this coupling mechanism is not shown, it may be similar to the coupling of fig. 8, wherein the bracket that conventionally connects the moving shield to the guide bar is replaced by a bracket similar to bracket 433 of fig. 8.

Further, in the embodiment of fig. 13(a), the lateral surface of the blade (not shown) and the slot 730 are formed with opposing conformal portions, as shown in any of fig. 5-7.

Fig. 13(b) shows a hood of a fifth embodiment of the present invention. The shroud is viewed towards a surface of the shroud facing away from the nozzle ring. The surface includes a land surface 710. The embodiment of fig. 13(b) is the same as that of fig. 13(a) (and therefore corresponding elements are given the same reference numerals), except that as shown in fig. 13(b), a ridge element 711 is provided along the edge of the slot 730, upstanding from the platform surface 710.

Fig. 13(c) shows a shield of a sixth embodiment of the present invention. The embodiment of fig. 13(c) is the same as that of fig. 13(a) (and therefore corresponding elements are given the same reference numerals), except that as shown in fig. 13(c), an annular ridge element 712 is provided around the entire edge of the slot 730 and upstanding from the surface 708 (which may be considered a platform surface).

Fig. 13(d) shows a shroud of a seventh embodiment of the present invention. The embodiment of fig. 13(d) is the same as that of fig. 13(a) (and corresponding elements are therefore given the same reference numerals) except that as shown in fig. 13(d) annular ridge elements 713 are provided around the entire edges of the slots 730, upstanding from the platform surface 710 facing away from the nozzle ring.

Fig. 13(e) shows a shroud of an eighth embodiment of the present invention. The embodiment of fig. 13(e) is the same as the embodiment of fig. 13(a) (and therefore corresponding elements are given the same reference numerals), except that as shown in fig. 13(e), the shroud comprises a plurality of vanes 714 arranged to provide a "waterwheel" arrangement. The vanes 714 are gas-interacting elements that produce a rotational force on the shroud due to the gas flow in recesses on the side of the shroud opposite the nozzle ring.

Fig. 13(f) shows a shroud of a ninth embodiment of the present invention. The embodiment of fig. 13(f) is the same as the embodiment of fig. 13(a) (and corresponding elements are therefore given the same reference numerals) except that as shown in fig. 13(d) a ridge element 715 is provided along the radially inward edge of the slot 730, the ridge element 715 upstanding from a platform surface 710 facing away from the nozzle ring. The radially outer end of the slot is crimped around the radially outer end of the slot 730.

In the simulations, we have demonstrated that the airflow in all of these embodiments produces positive torque, where the positive direction is counterclockwise as shown in fig. 13(a) (i.e., clockwise as viewed from the turbine end). This positive torque will tend to produce a blade-slot arrangement as shown in fig. 5 or 6, wherein the radially inner side of the slot 730 is pressed towards the radially inner side of the blade.

However, the embodiment of fig. 13(b) produces less positive torque than the embodiment of fig. 13(a), and the embodiments of fig. 13(c) and 13(e) are only more positive than the embodiment of fig. 11 (a). In the case of the embodiment of fig. 13(e), this is because the vanes 714 are in a position where the airflow tends to slow. In contrast, the embodiment of FIG. 13(d) produces about 75% higher positive torque on the radially inner side of the annular ridge members 713 than the embodiment of FIG. 13(a) due to the high pressure differential between the inwardly facing surfaces (low pressure locations) of the ridge members 713 and the opposing outwardly facing wall surfaces of the ridge members 713.

The embodiment of fig. 13(f) produces about twice the positive torque of the embodiment of fig. 13 (a). This is because the ridge elements 715 have the same surface as the ridge elements 713 of the embodiment of fig. 13(d), but do not have the radially outer portion of the annular ridge elements (i.e., there is no portion of the ridge elements 711 corresponding to fig. 13(b) that tends to reduce positive torque, as described above). Thus, it can be concluded that the ridge elements at the suction side of these embodiments are most effective in generating torque in the desired clockwise direction.

In the simulation, we investigated the effect of providing circumferential spacing between the radially inner wall surface of the ridge element 715 and the nearest portion of the slot inner surface in a variation of the embodiment of fig. 13 (f). In the embodiment of fig. 13(f), there is no such spacing (i.e., the radially outer wall surface of the ridge element 715 is simply an extension of the slot inner surface), but in these variations, the ridge element 715 is displaced in a counterclockwise direction as shown in fig. 13(f) to varying degrees. In other words, portions of the platform surface 710 are disposed between the slot 730 and the ridge member 715. It has been found that the larger the spacing, the more the torque is reduced. It can be concluded that maximum torque is generated when the radially outer wall surface of the ridge element 715 is substantially flush (i.e., the inwardly facing slot surface is a continuous axial extension of the closest portion) with the closest portion of the inwardly facing slot surface (in this case the slot inner surface).