GB2564838A

GB2564838A - Turbine

Info

Publication number: GB2564838A
Application number: GB1709578.7A
Authority: GB
Inventors: Desai Shrinivas
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2017-06-15
Filing date: 2017-06-15
Publication date: 2019-01-30
Anticipated expiration: 2037-06-15
Also published as: GB2564838B; GB201709578D0

Abstract

A turbine (1, fig 1) comprises a turbine housing (5, fig 1) with a turbine inlet 9 upstream of a turbine wheel 4 and a turbine outlet 10 downstream of the turbine wheel. A wastegate valve assembly 30 has a valve member 31 mounted within a chamber having a chamber inlet which communicates with the turbine inlet, and has one or more chamber outlets 38a, 38b which communicate with the turbine outlet. The valve member is movable by an actuation member (34, fig 4) between a closed position and a range of open positions. The valve member obstructs gas flow through the chamber by blocking a portion of the outlet(s). The chamber may be defined by a cylindrical wall (37, fig 4), where the outlets are formed as slots in the wall. The valve member may include a head 32 and a shaft 33.

Description

Field of the invention

The present invention relates to a turbine and in particular to a turbine having a wastegate. The turbine may form part of a turbocharger or power turbine.

Background of the Invention

Turbomachines are machines that transfer energy between a rotor and a fluid. For example, a turbomachine may transfer energy from a fluid to a rotor or may transfer energy from a rotor to a fluid. Two examples of turbomachines are a power turbine, which uses the rotational energy of the rotor to do useful work, for example, generating electrical power; and a turbocharger, which uses the rotational energy of the rotor to compress a fluid.

Turbochargers are well known devices for supplying air to an inlet 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 inlet 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 of a conventional 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.

The compressor of a conventional turbocharger comprises a compressor housing defining a compressor chamber within which the compressor wheel is mounted such that it may rotate about an axis. The compressor also has a substantially axial inlet passageway defined by the compressor housing and a substantially annular outlet passageway defined by the compressor housing between facing radially extending walls arranged around the compressor chamber. A volute is arranged around the outlet passageway and an outlet is in flow communication with the volute. The passageways and compressor chamber communicate such that gas (for example, air) at a relatively low pressure is admitted to the inlet and is pumped, via the compressor chamber, outlet passageway and volute, to the outlet by rotation of the compressor wheel. The gas at the outlet is generally at a greater pressure (also referred to as boost pressure) than the relatively low pressure of the gas which is admitted to the inlet. The gas at the outlet may then be pumped downstream of the compressor outlet by the action of the compressor wheel.

It is known to provide a turbocharger turbine with a valve controlled bypass port referred to as a wastegate port, to enable control of the turbocharger boost pressure and/or shaft speed. The wastegate port is the inlet of a tubular wastegate chamber defined by a wall, and an outlet of the wastegate chamber is in communication with the turbine output or the atmosphere. A wastegate valve (typically a poppet type valve) is provided, including a valve member which is movable within the wastegate chamber, e.g. an edge portion of the valve member may be connected to the wastegate chamber by a pivot. The combination of the wastegate port, the wastegate valve and the wastegate chamber is referred to as a wastegate. The wastegate is closed by advancing the valve member to a position at which it blocks the wastegate port, and thereby prevents gas entering the wastegate chamber. The wastegate valve is opened by retracting the valve member from the wastegate port. This allows gas from the turbine to enter the wastegate chamber through the wastegate port, then flow between the valve member and an inwardly facing surface of the wall, to the outlet of the wastegate chamber. The wastegate valve is controlled to open the wastegate port (bypass port) when the boost pressure of the fluid in the compressor outlet increases towards a pre-determined level, thus allowing at least some of the exhaust gas to bypass the turbine wheel.

The wastegate valve may be actuated by a variety of means, including electric actuators, but is more typically actuated by a pneumatic actuator operated by boost pressure delivered by the compressor wheel. The wastegate valve actuator is typically connected to the wastegate valve by a linkage, part of which passes through an actuation conduit in the turbine housing. Earlier patents describing wastegates include US 8336309 and EP1486678.

Summary of the invention

It is an object of the present invention to provide a new and useful turbine which obviates or mitigates disadvantages present in the prior art.

In general terms, the present invention proposes that a movable valve member of a wastegate valve of a turbine is inserted into a chamber which communicates with a turbine inlet upstream of the turbine, and has one or more chamber outlets which communicate with an outlet of the turbine. The valve member has a closed position in which it prevents gas flow though the chamber, and a range of open positions in which the valve member obstructs gas flow through the chamber by blocking a corresponding portion of the chamber outlet(s). Controlled movement of the valve member varies how much of the chamber outlet(s) is blocked by the valve member, and thus the degree of obstruction.

Embodiments of the invention may be formed in which the gas is not required to flow through a gap between the periphery of the valve member and walls of the chamber.

For example, the valve member may be movable to uncover a controlled portion of at least one opening, such as a slot, formed in a sidewall of the chamber. The gas flows from the inlet of the chamber to the uncovered portion of the opening. The motion of the portion of the valve member which covers or uncovers the opening may be substantially transverse to the direction in which gas flows through the opening.

By contrast, when the known wastegate having a valve member of the poppet type is opened in a controlled manner by retracting the poppet valve by a controlled distance from the wastegate port, the gas entering the wastegate chamber flows through a gap between the lateral periphery of the poppet valve and the inwardly-facing surface of the wall of the wastegate chamber, to reach the outlet of wastegate passage. The direction in which gas flows through the wastegate port is substantially parallel to the motion direction of the valve member as it approaches the wastegate port. Even when the poppet-type valve member is fully retracted from the inlet to the wastegate chamber, the valve member significantly blocks gas flow through the wastegate chamber to the outlet. One way to avoid this effect would be to widen the wastegate passage transverse to direction of gas flow past the valve member, so that the distance from the poppet valve to the wall of the wastegate passage is increased, but that would undesirably increase the cross-sectional area of the wastegate chamber as viewed in the motion direction of the valve member.

Thus, the present invention makes it possible to achieve an increased gas flow though the wastegate for a given cross-sectional area of the wastegate passage (as viewed in the direction in which gas enters the wastegate chamber). This allows the valve member to be designed with a reduced valve area compared to a known wastegate having a valve member of the poppet type.

Furthermore, the reduced valve area leads to a reduced force which an actuator of the valve member is required to produce to actuate the wastegate valve, and in particular to force the valve member into the closed position. Indeed in some embodiments of the invention, the actuator does not have to move the valve member in a direction having a component opposite to the gas flow, so the force the actuator is required to provide may be substantially independent of the gas flow. This possibility is particularly suitable in arrangements in which the actuator is electric.

Furthermore, we have found by computational fluid dynamics experiments (CDF) that controlling gas flow through the wastegate by controlling the degree to which the valve member blocks a corresponding portion of the chamber outlet(s), is more accurate than providing control at the inlet to the chamber. In particular, in preferred embodiments of the invention, the variation of the gas flow rate with the distance moved by the valve member may be made linear for a much wider range than in the known wastegate having a poppet-type valve member at the inlet.

For example, when the valve member of an embodiment of the invention uncovers a portion of an opening in the sidewall of the chamber, the flow volume is proportional to the area of the uncovered portion of the opening. By contrast, in the known wastegate using a poppet valve, the flow volume is highly dependent on the gap between the valve member and nearest portion of the chamber wall, which is a complex function of the position of the valve member.

From another point view, the degree to which gas flow can be bypassed away from the turbine through the wastegate can be increased without increasing the size of the moveable valve member.

According to a first specific expression of the present invention there is provided a turbine comprising a turbine wheel; a turbine housing defining a turbine inlet upstream of the turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage including a wastegate chamber having a chamber inlet communicating with the turbine inlet and one or more chamber outlets communicating with the turbine outlet; and a wastegate valve comprising an actuation member and a movable valve member, the valve member being inserted into the wastegate chamber and connected to the actuation member;

the valve member being movable by the actuation member between:

a closed position at which the valve member substantially prevents fluid from passing through the chamber between the chamber inlet and the one or more chamber outlets, and any of a range of open positions in which a fluid path exists through the chamber from the chamber inlet to the one or more chamber outlets, in each open position the valve member obstructing a respective portion of the one or more chamber outlets.

In particular, in each open position the valve member may obstruct a different respective proportion of the total area of the chamber outlets.

The chamber may be cylindrical (preferably circularly cylindrical) having an axis, and be defined by a wall surrounding (preferably encircling) the axis. Thus, the wall may have a shape which is similar to the wastegate port of a conventional system.

At least one of the chamber outlets may be formed as a through-hole (opening) in the wall of the chamber.

In the open positions, the fluid path is through an unobstructed portion of each of the opening(s). This portion of the opening is defined between an edge of the valve member and an edge of the opening.

Preferably, the edge of the valve member is inclined to the edge of the aperture along at least part of their respective lengths. This permits fine control of the cross-sectional area of the fluid path, as a function of the movement of the valve member across the opening.

In particular, for at least some of the range of open positions, the edge of the valve member may be inclined to the edge of the aperture at a point where they intersect.

The term “inclined” is used to mean that the smallest angle between the tangent line to the edge of the valve member and the tangent line to the edge of the opening is greater than zero degrees, and less than 90 degrees. For example, it may be an angle less than 80 degrees, or less than 70 degrees. It may be greater than 10 degrees, or greater than 20 degrees.

In a first form of the invention, the valve member is moveable between the open and closed positions longitudinally in a movement direction, e.g. if the chamber is cylindrical, the valve member may be movable parallel to an axis of the cylindrical chamber.

Conveniently, the chamber outlet(s) may be formed as elongated slot(s) in the wall, with at least a component of the elongation direction being in the movement direction.

The unobstructed portion of any of the slots may be an end portion of the slot, such as an end of the slot which is least far in the motion direction.

Preferably the edge of the slot includes a section which is tangential to the edge of the valve member and/or transverse to the movement direction. Proximate to this section of the edge of the slot, the edge of the slot may be inclined to the movement direction. The edge of the slot may be curved.

The slot may be lozenge shaped. That is, the slot includes: a front end portion at one end of the slot in the elongation direction, where the slot has increasing width transverse to the elongation direction; and a rear end portion at the opposite end of the slot in the elongation direction, where the slot has decreasing width transverse to the elongation direction.

In a second form of the invention, the valve member is moveable rotationally between the open and closed positions, and the chamber outlet(s) are formed in a radiallyinward facing surface of the chamber in contact with the valve member. The valve member has a surface which is not rotationally symmetric, so as the valve member rotates a differing portion of the valve member is in register with the chamber outlet(s), so that the chamber outlet(s) are blocked to a varying degree. This form of the invention, force from the gas one the valve member has little or no tendency to move the valve member between the open and closed positions, so the actuator does not have to oppose this force in order to maintain the valve member in one position, or move the valve member to the closed position.

The valve member may define at least one aperture, which may be brought by rotational motion, into register with a respective one of the chamber outlet(s). Thus, edge of the valve member may be an edge of the aperture.

For at least some of the opening positions, the edge of the aperture may be inclined to an edge of the chamber outlet(s) at intersection point(s) where the edge of the aperture intersects with the edge of each chamber outlet.

The axis of the chamber may include a thrust bearing opposing movement of the valve member in the axial direction. The axial direction may extend from the thrust bearing in the direction towards the inlet to the wastegate chamber. Thus, the force exerted on the valve member by exhaust gas entering the chamber is opposed by the thrust bearing. For that reason, this force does not tend to push the valve member transverse to the axis against the wall of the chamber, which could lead to significant resistance to rotational motion of the valve member.

According to a second aspect of the present invention there is provided a turbocharger or powerturbine including a turbine according to the first aspect of the present invention.

Brief Description of the Figures

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic cross-section through a portion of a known turbocharger;

Figure 2 is a perspective view of a turbine which is a first embodiment of the invention;

Figure 3 is a cross-sectional view of a portion of the turbine of Figure 2;

Figure 3 is a view of another portion of the turbine of Figure 2;

Figure 4 is a view of another portion of the turbine of Figure 2;

Figure 5 is a schematic view of another portion of the turbine of Figure 2 with a movable valve member in a forward position;

Figure 6 is a schematic view of the portion of the turbine of Figure 2 with the moveable valve member in a rearward position;

Figure 7 shows a valve member of the turbine of Fig. 2;

Figure 8 schematically shows the position of an edge of the valve member in relation to an opening in a wastegate chamber of the turbine of Fig. 2;

Figure 9 is a schematic graph of the variation, as the valve member moves, of the area of an unobstructed portion of the opening in the wastegate chamber;

Figure 10 is a perspective view of a turbine which is a second embodiment of the invention;

Figure 11 is a perspective view of a valve member which is part of the embodiment of Figure 10;

Figure 12 is a cross-sectional view of a portion of the embodiment of Figure 10, with the valve member in a first rotational position; and

Figure 13 is a cross-sectional view of the portion of the embodiment of Figure 10 with the valve member in a second rotational position.

Detailed description of the embodiments

Figure 1 shows a schematic cross-section through a known turbocharger. The turbocharger comprises a turbine 1 joined to a compressor 2 via a central bearing housing 3. The turbine 1 comprises a turbine wheel 4 for rotation within a turbine housing 5. Similarly, the compressor 2 comprises a compressor wheel 6 which can rotate within a compressor housing 7. The compressor housing 7 defines a compressor chamber within which the compressor wheel 6 can rotate. The turbine wheel 4 and compressor wheel 6 are mounted on opposite ends of a common turbocharger shaft 8 which extends through the central bearing housing 3.

The turbine housing 5 has an exhaust gas inlet volute 9 located annularly around the turbine wheel 4 and an axial exhaust gas outlet 10. The compressor housing 7 has an axial air intake passage 11 and a volute 12 arranged annularly around the compressor chamber. The volute 12 is in gas flow communication with a compressor outlet 25. The turbocharger shaft 8 rotates on journal bearings 13 and 14 housed towards the turbine end and compressor end respectively of the bearing housing 3. The compressor end bearing 14 further includes a thrust bearing 15 which interacts with an oil seal assembly including an oil slinger 16. Oil is supplied to the bearing housing from the oil system of the internal combustion engine via oil inlet 17 and is fed to the bearing assemblies by oil passageways 18. The oil fed to the bearing assemblies may be used to both lubricate the bearing assemblies and to remove heat from the bearing assemblies.

In use, the turbine wheel 4 is rotated by the passage of exhaust gas from the exhaust gas inlet 9 to the exhaust gas outlet 10. Exhaust gas is provided to exhaust gas inlet 9 from an exhaust manifold (also referred to as an outlet manifold) of the engine (not shown) to which the turbocharger is attached. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet 11 and delivers boost air to an inlet manifold of the engine via the volute 12 and then the outlet 25.

The exhaust gas inlet 9 is defined by a portion of the turbine housing 5 which includes a turbocharger mounting flange 27 at the end of the exhaust gas inlet 9 remote from the turbine wheel 4.

Figures 2 to 6 show various schematic views of a turbine 21 in accordance with a first embodiment of the present invention, and which is a portion of a turbocharger. The turbocharger includes all of the features of the turbocharger described above in relation to Figure 1. The same numbering is used within Figures 2 to 6 for features of the turbocharger shown in Figures 2 to 6 which are equivalent to features shown in the turbocharger of Figure 1.

In addition to the features of the turbine shown in Figure 1, the turbine 21 shown in Figures 2 to 6 also includes a wastegate valve assembly 30. As shown in Figure 2, the turbine 21 includes a turbine housing 23 which defines a turbine inlet 9 upstream of the turbine wheel 4, and a turbine outlet 10 downstream of the turbine wheel 4.

The wastegate valve assembly 30 is shown in Figure 3 viewed in cross-section in the direction marked as A in Figure 2. In Figure 4, the wastegate valve assembly 30 is shown looking in the direction opposite to direction A. Figures 5 and 6 show a schematic cross-section looking in the direction marked as B in Figure 2. In this document the term “forward direction” will be used to refer to the direction which is to the left in Figure 3 (i.e. to the right in Figure 4). The term “rearward direction” will be used to refer to the direction which is to the right in Figure 3 (i.e. to the left in Figure 4).

The wastegate valve assembly includes a valve member 31 including a head 32 and a shaft 33.

As shown in Figure 3, the valve member 31 is positioned in a circularly cylindrical wastegate chamber defined by a wall 37. The wall 37 is generally circularly cylindrical about an axis on which the shaft 33 of the valve member 31 lies. The axis extends in the forward-backward direction, and passes through the centre of the head 32. The valve member 31 is circularly symmetric about the axis.

As shown in Figure 4, the wastegate valve assembly further includes an actuator 34 having an arm 35 fixedly mounted on a body 36. The body 36 can be rotated by a drive mechanism about an axis parallel to the direction A. The drive mechanism is not described here, but may be a pneumatic drive mechanism; however, any other drive mechanism may be used. The end of the arm 35 distal from the body 36 is connected to a rear end of the shaft 33 of the valve member 31. The connection is by a pin 41 extending in the direction A from the shaft 33, and inserted into a pin slot 43 formed in the arm 35. Thus, rotation of the body 36 by the drive mechanism controls the position of valve member 31 in the forward-rearward direction.

The chamber defined by the wall 37 has openings at both axial ends. A first of these openings (the “forward opening”) is proximate and in communication with the turbine inlet 9. It functions as a chamber inlet to allow gas into the chamber. Elongate slots 38a, 38b are formed in the wall 37 with their elongation direction parallel to the axial direction. The slots 38a, 38b are of the same shape and size and are in register with each other when viewed in the direction A. The slots 38a, 28b function as chamber outlets for gas. Via the slots 38a, 38b, the chamber is in communication with the turbine outlet 10. Thus, the chamber is part of a wastegate passage between the forward openings and the chamber outlets.

Figures 2-5 illustrate the valve member at a time at which it is in a “closed” position. In this position the head 32 of the valve member 31 fills the forward opening and blocks the communication between the chamber and the turbine inlet 9. Thus, as shown in Figure 5, gas from the turbine inlet 9 is only able to pass to the turbine outlet 10 by passing near the turbine wheel 4, and turning it.

Rotating the body 36 of the actuator 34 in the direction which is anti-clockwise when looking in the direction A causes the arm 35 to rotate in the same direction. The arm 35 bears on the pin 41, which in turn pulls on the shaft 33 of the valve member 31. Thus, the rotation of the actuator 34 pulls the valve member 31 rearwardly (i.e. to the right, when looking in direction A). The head 32 moves away from the forward opening, and comes into register with the forward end of the slots 38a, 38b.

Continued rearward movement of the valve member 31 moves the head 32 along the slots 38a, 38b to the position shown in Figure 6. This position is one of a range of open positions the valve member 31 can enter. In each open position, each of the slots 38a, 38b is partitioned by the head 32 into a corresponding forward portion which is forward of the head 32, and a corresponding rear portion which is rearward of the head 32. Gas from the turbine inlet 9 is able to enter the chamber through the forward opening of the chamber, and to pass out of the chamber to the turbine outlet 10 though the respective front portions of the slots 38a, 38b, as shown by the arrows of Figure 6. This gas bypasses the turbine wheel 4.

The resistance to flow depends on the position of the head 32, and varies as the head 32 moves across the slots 38a, 38b. Accordingly the proportion of the gas which enters the turbine through the turbine inlet 9, but bypasses the turbine wheel 4, depends upon which position the valve member 31 is in, and the size of the corresponding forward portion of the slots 38a, 38b.

This is illustrated in more detail with reference to Figs. 7 to 9. Figure 7 shows the geometry of the head 32. The head 32 includes a cylindrical portion 321 which has a radius the same as (or very slightly smaller than) the radius of the inwardly-facing surface of the wall 37. Thus, the cylindrical portion 321 fits snugly within the cylindrical wastegate chamber defined by the wall 37. The clearance between the cylindrical portion 321 and the inwardly-facing surface of the wall 37 is too small for gas to pass between them. The head 32 further includes a domed front portion 322. The intersection between the curved front portion 322 and the cylindrical portion 131 is at a circular edge 323.

As shown in Fig. 8 each of the slots 38a, 38b is lozenge shaped. That is, the slot includes: a front end portion at one end of the elongation direction where the slot has increasing width transverse to the elongation direction; and a rear end portion where the slot has decreasing width transverse to the elongation direction.

The edge of the slot in the front end portion is referred to as the front edge 381. The front edge 381 may be curved (e.g. semi-circular as viewed perpendicular to the axis of the wastegate chamber). The edge of the slot in the rear end portion is referred to as the rear edge 382. The rear edge 382 may be curved also (e.g. semi-circular as viewed perpendicular to the axis of the wastegate chamber).

The front edge 381 and rear edge 382 are connected by straight side edges 383, 384, which are parallel to the axial direction.

When the edge 323 of the head 32 is to the left of the whole of the front edge 381 (that is, further in the forward direction), the valve member 32 fully obstructs gas from passing through the slots 38a, 38b.

As the head 32 moves rearwardly (to the right in Figure 8), the edge 323 intersects with the front edge 381. Initially this intersection is just at the point on the front edge 381 which is furthest in the forward direction. At this intersection point, the edge 323 is parallel to the front edge 381 (because both the respective tangents extend in the circumferential direction around the axis, and there is an angle of zero degrees between them).

When the head 32 moves further rearwardly (i.e. the head 32 moves across the forward end of the slot 38a, 38b), there are two intersection points 381a, 381b between the front edge 381 and the edge 323. The intersection points 381a, 381b move gradually apart as the head 32 moves. The edge 323 is inclined to the front edge 381 at the intersection points 381a, 381b, because the tangent to the front edge 381 at each of the intersection points 381a, 381b includes a component in the axial direction.

The axial distance from the point on the front edge 381 which is furthest in the forward direction, and the edge 323, is denoted by x in Figure 8.

The portion of the slot 38a, 38b which is not obstructed by the head 32 is the portion of the slot 38a, 38b which is forward of the edge 323. The variation with x of the area of this unobstructed portion of the slot 38a, 38b is shown in Figure 9. As can be seen, the area increases from zero very slowly to begin with, which implies that controlling the axial position of the head 32 gives accurate control over the area of the unobstructed portion of the aperture 38a, 38b while x is small. Thus, the embodiment permits fine control of the gas flow through the wastegate chamber.

The total amount of gas which can bypass the turbine 4 by passing through the chamber and out of the slots 38a, 38b is not limited by the area of the head 32 as viewed in the axial direction. This means that, to allow a given quantity of gas transport though the wastegate valve assembly, the area of the head 32 as viewed in the axial direction can be reduced compared to the conventional wastegate valve assembly described above which employs a poppet valve as the movable valve member. We determined in a computational fluid dynamic (CFD) simulation that an embodiment of the invention as depicted in Figures 1-9 with a head 32 of diameter 15mm diameter and in which the valve member 31 has a distance of travel of 20mm, produces the same gas throughput as a conventional poppet-type wastegate value with an inlet of 25mm diameter.

Looking at this from another point of view, for a given gas flow rate, the required size of the head 32 is reduced. The reduced size of the head 32 leads to a reduced force required by the actuator 34 to maintain the valve member 31 at any desired position along the chamber, or to force the valve member 31 to move forward towards the closed position.

Turning to Figures 10-13, a turbine 101 which is a second embodiment of the invention is shown. This turbine 101 too has the features of the turbine shown in Figure 1, which will be designated by the same reference numerals, but the turbine 101 shown in Figures 10 to 13 also includes a wastegate valve assembly 130.

Figure 10 is a perspective view of the turbine 101. As shown in Figure 10, the turbine 101 includes a turbine housing 123 which defines a turbine inlet 9 upstream of the turbine wheel 4, and a turbine outlet 10 downstream of the turbine wheel 4.

The wastegate valve assembly 130 includes a generally circularly cylindrical chamber defined by a generally circularly cylindrical wall 137, encircling a central chamber axis. Figures 10 and 11 are views of the turbine 101 looking in the direction A, with portions of the wall removed. The direction to the left in Figures 12 and 13 is referred to as the “forward” direction, and the direction to the right is the “rearward direction”. Both these directions are parallel to the central chamber axis.

The chamber has a forward opening on the chamber axis communicating with and proximate to the turbine inlet 9, and thus functioning as a chamber inlet. It also has a rear opening on the chamber axis facing in the rearward direction. In one side of the wall 137 is a single slot 138 which functions as a chamber outlet. The slot is elongate, in the axial direction. Thus, the chamber is part of a wastegate passage between the forward openings and the slot (chamber outlet). The slot 138 may have substantially the same shape as the slots 38a, 39b of Figure 8. That is, the slot 138 is lozenge shaped: its edge has front and rear edges at either end, where the width of the slot along the elongation direction respectively increases and decreases (e.g. the front and rear edges may be curved edges). The front and rear edges are connected by straight, axially-extending side edges.

Figure 11 shows a valve member 131, having a barrel portion 132 which is generally circularly cylindrical about a barrel axis. The barrel portion is mounted at one end of a shaft 133, which lies on the barrel axis. A link element 134 is fixedly mounted on the shaft 134 and is elongate in the direction perpendicular to barrel axis. A bar 135 is fixedly mounted on the link element 134 and extends parallel to, but offset from, the barrel axis.

In use, and as shown in Figures 10, 12 and 13, the barrel portion 132 of the vale member 131 is inserted into the chamber through the rear opening, with the barrel axis coinciding with the chamber axis, as does the central line of the shaft 133.

The radius of the barrel portion 132 is very slightly less than the radius of the chamber, so that the barrel portion 132 substantially fits snugly into the chamber preventing gas flow through the chamber around the periphery of the barrel portion 132. The barrel portion 132 is rotatable about the barrel axis, and bearings (not shown) maintain the barrel portion 132 at a fixed position along the chamber axis in which a forward end of the barrel portion 132 is at the forward opening of the chamber, and the rearward end of the barrel portion 132 is within the chamber. In particular, the bearings comprise a thrust bearing (not shown) facing towards the chamber inlet along the barrel axis, and opposing motion of the barrel portion 132 of the valve member along the barrel axis.

The barrel portion 132 of the valve member 131 is rotatable about the barrel axis using the bar 135, the link element 134, and the shaft 134. An actuator (not shown), such as, but not limited to, a pneumatic actuator is provided for this purpose.

The barrel portion 132 of the valve member 131 is hollow, containing a generally cylindrical barrel chamber encircled by a generally cylindrical barrel wall 140. The forward end of the barrel portion 132 of the valve member 131 is open, so that the barrel chamber communicates with the turbine inlet 9. An aperture 139 is formed in the barrel wall 140, with an edge 136 which is inclined to the barrel axis.

When the valve member 131 is inserted into the chamber in the position shown in Figure 12, the slot 138 is not in register with the aperture 139. The barrel chamber of the barrel portion 132 of the valve member 131 is in communication with the turbine inlet 9 but there is no gas path from the barrel chamber to the turbine outlet 10. Thus, the valve member 131 is in a “closed” position.

However, if the valve member 131 is rotated by the actuator about the barrel axis, the valve member 131 moves across the slot 138. The aperture 139 gradually comes into register with the slot 138. This creates a path by which gas can flow through the forward opening of the chamber, into the barrel chamber of the barrel portion 132 of the valve member 131, and out through the aperture 139 and the slot 138 to the turbine outlet 10, thus bypassing the turbine wheel 4. The width of the gas path depends upon the size of the portion of the slot 138 which is in register with the aperture 139, and thus is controllable by controlling the rotational position of the valve member 131.

Note that the forces exerted by the gas onto the valve member 131 largely urge the valve member along the barrel axis, and are opposed by the bearing (not shown). Thus, the force which has to be applied by the actuator in order to rotate the valve member 131 may be substantially independent of the force exerted by the gas on the valve member 131. Thus, to an even greater extent than in the first embodiment, the force which has to be applied by the actuator to control the wastegate valve assembly is reduced compared to the conventional wastegate valve described above which employs a poppet valve. This possibility is particularly suitable in the case that the actuator is electric, i.e. the valve member is moved electrically.

The inclination of the edge 136 to the barrel axis changes the relationship between the rotational position of the valve member 131 and the flow resistance, because it changes the overlap between the slot 138 and the aperture 139. In particular, if, at a time when the aperture 139 is not in register with the slot 138, the valve member is rotated in the direction which is anti-clockwise when viewed in the direction marked as B in Figure 10 (and which is parallel to the barrel axis), the corner 141 of the of the aperture 139 first comes into register with part of the slot 138, creating a narrow gas path. At this stage there is an intersection between the edge 136 of the aperture 139 and the edge of the slot 138.

Because the edge 136 of the slot 138 is inclined to the side edge of the aperture 138, the area of the overlap of the aperture 139 and the slot 138 is at this stage very sensitive to small angular variations of the position of the barrel portion 132 about the barrel axis. This allows fine control of the extent to which the gas bypasses the turbine wheel 4, by fine control of the angular position of the valve member 131 about the barrel axis.

For example, the edge 136 may be designed to have the same axial length as the straight side edges of the slot 138, and to be in axial register with them. In this case, the area of the part of the slot 138 which is not obstructed by the barrel portion 132 is zero until the edge 136 intersects with a side edge of the slot 138 (the “upper” side edge in Figure 10). This intersection is at one end of the edge 136 and one end of the side edge of the slot 138.

As the barrel portion is moved rotationally further in the anti-clockwise direction (as viewed in the direction B on Figure 10) across the slot 138, the intersection point of the edge 136 and the upper side edge of the slot 138 moves gradually to the left in Figure

12.

During this process, the area of the portion of the slot 138 which is not obstructed by the barrel portion 132 (that is, the area of the portion of the aperture 139 which is in register with the slot 138) rises approximately in proportion to the square of the angular displacement of the barrel portion 132. This permits more accurate control of the unobstructed area (and thus of the extent of fluid flow) than would be possible if the edge 136 were parallel to the side edge of the slot 138 (in which case the area of the unobstructed portion of the slot 138 would rise linearly with the angular displacement of the barrel portion).

It is to be appreciated that numerous modifications to the above-described embodiments may be made without departing from the scope of the invention as defined in the appended claims.

Although the previous description is related to embodiments of a turbine according to the present invention which forms part of a turbocharger, it will be appreciated that a turbine according to the present invention may form part of any appropriate turbomachine. For example, a turbine according to the present invention may form part of a turbomachine which does not include a compressor. In particular, a turbine according to the present invention may form part of a power turbine, for example a power turbine which converts the rotation of a turbine wheel into electrical power.

Although the above described embodiments relate to a turbine which operates in conjunction with gas, it will be appreciated that turbines according to the present invention may operate in conjunction with any appropriate fluid, for example a liquid.

Claims

1. A turbine comprising a turbine wheel; a turbine housing defining a turbine inlet upstream of the turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage including a wastegate chamber having a chamber inlet communicating with the turbine inlet and one or more chamber outlets communicating with the turbine outlet; and a wastegate valve comprising an actuation member and a movable valve member, the valve member being inserted into the wastegate chamber and connected to the actuation member;

the valve member being movable by the actuation member between:

2. A turbine according to claim 1 in which the chamber is defined by a wall, each of the one or more chamber outlets being a respective opening in the wall, the valve member being movable across each opening to create the fluid path from the inside of the chamber through a controlled portion of the opening.

3. A turbine according to claim 2 in which, in each open position, the fluid path is defined between an edge of the valve member and an edge of the opening, and in at least some of the range of open positions, the edge of the valve member is inclined to the edge of the opening at an intersection point of the edge of the valve member and the edge of the opening.

4. A turbine according to claim 2 or claim 3 in which the wall surrounds a straight axis which extends in an axial direction.

5. A turbine according to claim 2, claim 3 or claim 4 in which at least one of the chamber outlets is formed as a slot in the wall, the slot having an elongation direction.

6. A turbine according to any preceding claim in which the valve member is moveable longitudinally in a movement direction between the closed position and the open positions.

7. A turbine according to claim 6 when dependent on claim 5, in which the elongation direction has at least a component in the movement direction.

8. A turbine according to claim 7 in which the elongation direction is parallel to the movement direction.

9. A turbine according to claim 7 or claim 8 when dependent upon claim 3, in which the edge of the slot is at an end of the slot which is least far along the movement direction.

10. A turbine according to any of claims 7 to 9 when dependent on claim 3 in which the edge of the slot is curved.

11. A turbine according to claim 9 or 10 in which the edge of the slot has a decreasing angle to the movement direction at respective positions which are successively further in the elongation direction.

12. A turbine according to any of claims 9 to 11 in which the edge defines an end portion of the slot in which, at respective positions which are successively further in the movement direction, the slot has increasing width transverse to the elongation direction.

13. A turbine according to any of claims 9 to 12 in which the slot includes an end portion furthermost in the movement direction, and side edges connecting the edge and the end portion.

14. A turbine according to claim 4 in which the chamber is circularly cylindrical about the axis, and said wall has an inner surface which faces radially-inwardly towards the axis, the valve member being moveable rotationally about the axis between the open and closed positions.

15. A turbine according to claim 14 in which the valve member includes a barrel portion located within the chamber and having an outer surface facing the wall, the barrel portion defining a barrel chamber in communication with the turbine inlet and having at least one aperture, wherein, in the closed position, the at least one aperture is not in register with the at least one chamber outlet, and in each of the open positions, a corresponding portion of the of the at least one aperture is in register with the at least one chamber outlet.

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16. A turbine according to claim 15 in which the valve member bears on a thrust bearing opposing movement of the valve member in the axial direction.

17. A turbine according to claim 16 in which the axis is directed from the thrust bearing towards the chamber inlet.

18. A turbine according to claim 16 or 17 when dependent upon claim 3 in which 10 the edge of the valve member is an edge of the aperture in the barrel portion of the valve member.

19. A turbine according to claim 18 in which the edge of the valve member is inclined to the axis.

20. A turbine according to claim 18 or claim 19 in which the edge of the at least one 15 chamber outlet is parallel to the axis.

21. A turbocharger or powerturbine including a turbine according to any preceding claim.