GB2516767A

GB2516767A - Turbine

Info

Publication number: GB2516767A
Application number: GB1412375.6A
Authority: GB
Inventors: John Bywater
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2013-07-12
Filing date: 2014-07-11
Publication date: 2015-02-04
Anticipated expiration: 2034-07-11
Also published as: GB201412375D0; GB2516767B; GB201312524D0

Abstract

Disclosed is a turbine 32 comprising a turbine housing 5 defining a turbine inlet 9 upstream of a turbine wheel 4 and a turbine outlet 10 downstream of the turbine wheel. The turbine also comprises a wastegate passage 34 connecting the turbine inlet and the turbine outlet to bypass the turbine and a wastegate valve comprising a movable valve member, poppet valve 36. The wastegate valve has an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage. The valve member is mounted to an actuation member 39, the actuation member passing through an actuator conduit 40 of the turbine housing. The turbine further comprises a sealing arrangement, annular seal ring 44, configured to provide a seal arranged to substantially prevent gas passing from the turbine outlet into the actuator conduit. The sealing arrangement is degradable such that when the sealing arrangement is subjected to a first environment, such as a cold environment, in which an initial turbine performance test is conducted the sealing arrangement substantially does not degrade and when the sealing arrangement is subjected to a second environment, for example a hot environment, in which the turbine normally operates the sealing arrangement degrades. The seal may comprise a wax, paper or cardboard sealing part.

Description

Turbine The present invention relates to a turbine and in particular to a turbne having a degradable sealing arrangement. The turbine may form part ol a turbocharger or power turbine. The present invention also relates to a method of turbine assembly.

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. It is also known to improve turbine performance by providing vanes, referred to as nozzle vanes, in the inlet so as to deflect gas flowing through the inlet. That is, gas flowing through the annular inlet flows through inlet passages (defined between adjacent vanes) which induce swirl in the gas flow, turning the flow direction towards the direction of rotation of the turbine wheel.

Turbines may be of a fixed or variable geometry type. Variable geometry turbines differ from fixed geometry turbines in that characteristics of the inlet (such as the inlet's size) can be varied to optimise gas flow velocities over a range of mass flow rates so that the power output of the turbine can be varied to suit varying engine demands. For instance, when the volume of exhaust gas being delivered to the turbine is relatively low, the velocity of the gas reaching the turbine wheel is maintained at a level which ensures efficient turbine operation by reducing the size of the inlet using a variable geometry mechanism. Turbochargers provided with a variable geometry turbine are referred to as variable geometry turbochargers.

Nozzle vane arrangements in variable geometry turbochargers can take different forms. Two known types of variable geometry turbine are swing vane turbochargers and sliding nozzle turbochargers.

Generally, in swing vane turbochargers the inlet size (or flow size) of a turbocharger turbine is controlled by an array of movable vanes in the turbine inlet. Each vane can pivot about an axis extending across the inlet parallel to the turbocharger shaft and aligned with a point approximately half way along the vane length. A vane actuating mechanism is provided which is linked to each of the vanes and is displaceable in a manner which causes each of the vanes to move in unison, such a movement enabling the cross sectional area available for the incoming gas and the angle of approach of the gas to the turbine wheel to be controlled.

Generally, in sliding nozzle turbochargers the vanes are fixed to an axially movable wall that slides across the inlet. The axially movable wall moves towards a facing shroud plate in order to close down the inlet and in so doing the vanes pass through apertures in the shroud plate. Alternatively, the nozzle ring is fixed to a wall of the turbine and a shroud plate is moved over the vanes to vary the size of the inlet.

The compressor of a conventional turbocharger comprises a compressor housing defining 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, to enable control of the turbocharger boost pressure and/or shaft speed. A wastegate valve (typically a poppet type 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. Typically the wastegate port opens into a wastegate passage which diverts the bypass gas flow to the turbine outlet or vents it to atmosphere.

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 actuator conduit in the turbine housing. Where the linkage passes through the actuator conduit it is possible that fluid from the turbine outlet may leak into the actuator conduit and then to atmosphere.

In some cases, after the turbine has been assembled, the turbine undergoes a pass-off test in order to evaluate aspects of the performance of the turbine to ensure that the turbine meets specified performance standards. One portion of the pass-off test is a pressure leak down test. This test is used to check the turbine for leaks which may have an adverse effect on the operating performance of the turbine. If, in a particular turbine, a leakage path exists from the turbine outlet, through the actuator conduit and thence to atmosphere, then this may result in the turbine failing the pressure leak down test. However, in such a case, although the leakage path via the actuator conduit has caused the turbine to fail the pressure leak down test, the presence of such a leakage path via the actuator conduit is not, generally, a significant fault which will result in unacceptable performance of the turbine.

Turbines which fail a portion of the pass-off test (e.g. the pressure leak dawn test) may be recalled so that they can be inspected and/or reassembled before being retested and, if passed, released for dispatch. It will be appreciated that inspection, reassembly and/or retesting of a turbine which fails the pressure leak down test due to a leakage path via the actuator conduit (generally, a non-significant fault) may be a waste of time, effort and money. This is because a turbine with a leakage path via the actuator conduit will, in general, still exhibit acceptable performance and hence such a turbine could be have been released for dispatch without the need for inspection, reassembly and/or retest.

It is an object of the present invention to provide a turbine which obviates or mitigates at the above described disadvantage or other disadvantages present in the prior art.

According to a first aspect of the present invention there is provided a turbine comprising a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve comprising a movable valve member; the wastegate valve having an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage; and wherein the valve member is mounted to an actuation member, the actuation member passing through an actuator conduit of the turbine housing, and being movable so as to move the wastegate valve between the open and closed states; the turbine further comprising a sealing arrangement configured to provide a seal arranged to substantially prevent gas from passing from the turbine outlet into the actuator conduit; wherein the sealing arrangement is degradable such that when the sealing arrangement is subjected to a first environment in which an initial turbine performance test is conducted the sealing arrangement substantially does not degrade, and when the sealing arrangement is subjected to a second environment in which the turbine normally operates the sealing arrangement degrades.

According to a second aspect of the invention there is provided a turbine comprising a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve comprising a movable valve member; the wastegate valve having an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine nlet and the turbine outlet via the wastegate passage; and wherein the valve member is mounted to an actuation member, the actuation member passing through an actuator conduit of the turbine housing, and being movable so as to move the wastegate valve between the open and closed states; the turbine further comprising a sealing arrangement configured to provide a seal arranged to substantially prevent gas from passing from the turbine outlet into the actuator conduit; wherein the sealing arrangement is designed to degrade in a second environment corresponding to normal operating conditions of the turbine, and the sealing arrangement is designed to substantially not degrade in a first environment corresponding to an environment in which an initial turbine performance test is conducted.

The seal arrangement substantially does not degrade in the first environment. In other words, in the first environment the seal arrangement is capable of operating as an effective seal. Hence, in the first environment the seal arrangement provides a seal which substantially prevents gas from passing from the turbine outlet into the actuator conduit. The seal arrangement is designed to degrade in the second environment. As such, the seal arrangement degrades in the second environment such that it no longer provides an effective seal.

Such an arrangement provides a relatively low cost and simple way of sealing any leakage path which exists from the turbine outlet, through the actuator conduit and thence to atmosphere. Such a leakage path may result in a costly failure of the turbine during the pressure leak down test. Because the leakage path via the actuator conduit which may cause the turbine to fail the pressure leak down test is not, generally, a significant fault which will result in unacceptable operating performance of the turbine, the seal arrangement is designed to degrade during normal operating conditions, when sealing of the leakage path is not necessary. As previously mentioned, using a seal arrangement which is designed to function effectively as a seal in the first environment but which does not have to function effectively as a seal in a second envronment (i.e. during normal operating conditions) means that the seal arrangement used can be relatively cheap and simple, yet still effective as a seal in the first environment.

The turbine may be subjected to the first environment (e.g. initial turbine performance test) prior to the second environment (e.g. normal operating conditions).

The first environment may differ from the second environment in that the temperature of the first environment is different to the temperature of the second environment.

The temperature of the first environment may be less than the temperature of the second environment.

The temperature of the first environment may fall within at least one of the group of ranges including: about 0°C to about 50°C, about 10°C to about 40°C, and about 10°C to about 30°C.

The temperature of the second environment may fall within at least one of the group of ranges including: about 100°C to about 1200°C, about 300°C to about 1100°C, and about 500°C to about 1000°C.

The valve member may be mounted to the actuation member such that the valve member is located on a first side of the actuator conduit, and a portion of the actuation member is mechanically linked to an actuator or linkage configured to be linked to an actuator, wherein the portion of the actuation member which is mechanically linked to the actuator or linkage configured to be linked to the actuator is located on a second side of the actuator conduit.

The sealing arrangement may comprise a seal member.

The seal member may be disposed upon the actuation member.

The seal member may be sandwiched between the valve member and the turbine housing.

The turbine may further comprise a bush, the bush being received by the actuator conduit and the actuation member passing through the bush, and wherein the seal member is sandwiched between the valve member and the bush.

The seal member may at least in part be formed from a material which is solid in the first environment, and a liquid or gas in the second environment.

The seal member may at least in part be formed from wax.

The seal member may at least in part be formed from a material which combusts in the second environment.

The seal member may at least in part be formed from paper or cardboard.

The sealing arrangement (for example the seal member) may comprise a lubricant. For example, a portion of the sealing arrangement (for example the seal member) may be formed from a material which is a lubricant. In other embodiments a portion of the sealing arrangement (for example the seal member) may be impregnated with a lubricant or have a coating of lubricant. The lubricant may also be configured such that when it is subjected to the second environment in which the turbine normally operates the lubricant degrades. The lubricant may be a wax-type material. The wax-type material.

The above optional features may apply to either the first or second aspects of the invention above or either of the third or fourth aspects of the invention below.

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

According to a fourth aspect of the invention there is provided a method of producing a turbine, the turbine comprising a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve comprising a movable valve member; the wastegate valve having an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage; and an actuation member, the actuation member being movable so as to move the wastegate valve between the open and closed states; the method comprising assembling the turbine, the assembling comprising passing the actuation member through an actuator conduit of the turbine housing, and sealing the actuator conduit with a sealing arrangement that substantially prevents gas from passing from the turbine outlet into the actuator conduit; performing an initial turbine performance test in a first environment, the sealing arrangement being designed (or configured) such that the sealing arrangement substantially does not degrade in the first environment; and operating the turbine in a second environment, the sealing arrangement being designed (or configured) such that the sealing arrangement degrades in the second environment.

A specific embodiment 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 shows a schematic perspective view of a portion of a turbocharger including a turbine according to the present invention; Figure 3 shows a schematic end-on perspective view of a portion of the turbocharger shown in Figure 2; Figure 4 shows a schematic cross-section through a portion of the turbocharger shown in Figures 2 and 3; and Figure 5 shows an schematic exploded perspective view of a valve member and actuation member which forms part of the turbocharger in Figures 2 to 4.

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 U 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 4 show various schematic views of portions of a turbocharger 30 which includes a turbine 32 in accordance with an embodiment of the present invention. The turbocharger 30 includes all of the features of the turbocharger described above in relation to Figure 1. The same numbering is used within Figures 2 to 5 for features of the turbocharger 30 shown in Figures 2 to 5 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 according to an embodiment of the present invention shown in Figures 2 to 4 also includes a wastegate assembly. As can be seen best in Figure 4, the turbine 32 includes a turbine housing 5 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 arrangement includes a wastegate passage 34 (indicated schematically in dashed lines) which extends between the turbine inlet 9 and turbine outlet 10, and hence connects the turbine inlet 9 with the turbine outlet 10. The wastegate arrangement also includes a wastegate valve comprising a movable valve member 36 and a valve seat 38. The valve seat 38 is a surface of the turbine housing 5 which is configured to be contactable with a surface of the valve member 36 in order to produce a substantially gas-tight seal between the valve seat 38 and the valve member 36.

The wastegate valve (and hence valve member 36) has an open state (as can be seen in Figure 4) in which gas may pass between the turbine inlet 9 and turbine outlet 10 via the wastegate passage 34. The wastegate valve (and hence valve member 36) also has a closed state (as shown in Figure 3) in which the wastegate valve member 36 contacts the valve seat 38 and thereby in which gas is substantially prevented from passing between the turbine inlet 9 and turbine outlet 10 via the wastegate passage 34.

The valve member 36, which in this embodiment is of a poppet type, is mounted to an actuation member 39 having a longitudinal axis A. The actuation member passes through an actuator conduit 40 of the turbine housing 5. The actuation member 39 is movable so as to move the wastegate valve between the open and closed states and, in particular, so as to move the valve member 36 between corresponding open and closed states.

The actuation member 39 may be moved in any appropriate manner so as to move the valve member 36 of the wastegate valve between the open and closed states. In the embodiment of turbine shown within Figures 2 to 5 this is achieved as follows. The actuation member 39 includes a generally cylindrical shaft 45 which extends along a longitudinal axis A. The shaft 45 of the actuation member 39 is connected at a first end to the valve member 36. The shaft of the actuation member 39 is connected at a second end to a lever arm 46. Within Figure 5, the lever arm 46 is shown separated from the shaft 45 in order to aid the clarity of the Figure. In present embodiment, the second end of the shaft 45 of the actuation member is received by a recess 48 of the lever arm 46. Spaced from the recess 48 along the lever arm 46 is a stub 50. The stub 50 is received by a first end 52 of an actuation rod 54. A second end (not shown) of the actuation rod 54 is connected to an actuator (again, not shown).

In this embodiment, the actuator is a pneumatic actuator; however, any appropriate actuator may be used. The mounting and operation of an actuator (and any associated linkage) in order to move a valve member of a wastegate valve is well-known, and hence further discussion of this is omitted within this description. However, it is worth noting that movement of the actuator rod 54 causes the lever arm 46, and hence attached shaft 45 of the actuation member 39, to pivot about axis A. The pivoting movement of the shaft 45 of the actuation member 39 about the axis A results in the valve member 36 also pivoting about axis A. Hence the valve member 36 can pivot about axis A between the open state (corresponding to the open state of the wastegate valve) in which the valve member 36 is spaced from the valve seat 38, and the closed state (corresponding to the closed state of the wastegate valve) in which the valve member 36 contacts the valve seat 38.

The shaft 45 of the actuation member is located within the actuator conduit 40 as follows. A bush 74 is received by the actuator conduit 40 of the turbine housing 5. The bush 74 is generally annular and the shaft 45 of the actuation member passes through the central opening of the annular bush 74.

In some embodiments a leakage path may be formed from the turbine outlet 10 to atmosphere via the actuator conduit 40 such that gas from the turbine outlet 10 may pass through the actuator conduit 40 to atmosphere. In embodiments in which the actuation member is located within the actuator conduit by a bush, the leakage path via the actuator conduit may include a leakage path between the actuation member and the bush -e.g. between the outer diameter of the actuation member and the inner diameter of the bush.

In some cases, after the turbine has been assembled, the turbine may undergo a pass-off test (an initial turbine performance test) in order to evaluate aspects of the performance of the turbine to ensure that the turbine meets specified performance standards. One portion of the pass-off test may be a pressure leak down test. This test is used to check the turbine for leaks which may have an adverse effect on the operating performance of the turbine. If, in a particular turbine, a leakage path exists from the turbine outlet, through the actuator conduit and thence to atmosphere, then this may result in the turbine failing the pressure leak down test. However, in such a case, although the leakage path via the actuator conduit has caused the turbine to fail the pressure leak down test, the presence of such a leakage path via the actuator conduit is not, generally, a significant fault which will result in unacceptable operating performance of the turbine.

Turbines which fail a portion of the pass-off test (e.g. the pressure leak down test) may be recalled so that they can be inspected and/or reassembled before being retested and, if passed, released for dispatch. It will be appreciated that inspection, reassembly and/or retesting of a turbine which fails the pressure leak down test due to a leakage path via the actuator conduit (generally, a non-significant fault) may be a waste of time, effort and money. This is because a turbine with a leakage path via the actuator conduit will, in general, still exhibit acceptable performance during operation (e.g. when it is installed to the exhaust outlet of an engine) and hence such a turbine could be have been released for dispatch without the need for inspection, reassembly and/or retest.

It can be seen from above that the pass-off test (or initial turbine performance test) is performed after the turbine has been assembled, and prior to the turbine being mounted to an exhaust outlet of an engine of which the turbine forms part. The engine to which the turbine is mounted may form part of a vehicle. After the turbine has been mounted to the engine, the engine (and hence turbine) is then operated in its normal operating condition. The normal operating condition may continue for many thousand engine operating hours. If the engine forms part of a vehicle, the engine may operate in its normal operating condition for tens or hundreds of thousands of miles.

The embodiment of the invention shown in Figures 2 to 5, includes a sealing arrangement comprising an annular seal ring 44 (or seal member) which is disposed upon the shaft 45 of the actuation member and is sandwiched between the valve member 36 and the bush 74. In other embodiments of the present invention, such as those which do not include a bush which locates the actuation member within the actuator conduit, the seal member may be sandwiched between the valve member and the turbine housing.

The valve member 36 is mounted to the actuation member such that the valve member 36 is located on a first side of the actuator conduit 40. A portion of the actuation member is mechanically linked to a linkage (actuator lever 46 and actuator rod 54) configured to be linked to an actuator. The portion of the actuation member which is mechanically linked to the linkage configured to be linked to the actuator, is located on a second side of the actuator conduit 40. Within Figure 4, the first side of the actuator conduit 40 is indicated generally by 70 and the second side of the actuator conduit 40 is indicated generally by 72.

As previously discussed, the turbine of the present invention includes a sealing arrangement 42 which is configured to provide a seal arranged to substantially prevent gas from passing between the turbine outlet 10 and the actuator conduit 40. In particular, the sealing arrangement 42 is configured to provide a seal arranged to substantially prevent gas from passing from the turbine outlet 10 into the actuator conduit 40. In the embodiment shown, the sealing arrangement 42 includes a seal member in the form of an annular seal ring 44. It will be appreciated that in other embodiments the sealing arrangement may have any appropriate configuration provided that it is capable of substantially preventing gas from passing between the turbine outlet and the actuator conduit.

The sealing arrangement (and in particular the seal ring 44 of the sealing arrangement) is degradable such that when the sealing arrangement 42 is subjected to a first environment in which an initial turbine performance test (e.g. pass-off test and/or pressure leak down test) is conducted, the sealing arrangement (and in particular the sealing ring of the sealing arrangement) substantially does not degrade. Furthermore, when the sealing arrangement 42 (and in particular the sealing ring 44 of the sealing arrangement 42) is subjected to a second environment in which the turbine normally operates (i.e. the normal operating condition of the turbine), the sealing arrangement (in particular the sealing ring 44 of the sealing arrangement 42) degrades.

In other words the seal arrangement (for example the seal ring 44 of the sealing arrangement) may be designed or configured to degrade in a second environment corresponding to normal operating conditions of the turbine, and the sealing arrangement may be designed or configured to substantially not degrade in a first environment corresponding to an environment in which an initial turbine performance test is conducted. The seal arrangement substantially does not degrade in the first environment. In other words, in the first environment the seal arrangement is capable of operating as an effective seal. Hence, in the first environment the seal arrangement provides a seal which substantially prevents gas from passing from the turbine outlet into the actuator conduit. The seal arrangement is designed to degrade in the second environment. As such, the seal arrangement degrades in the second environment such that it no longer provides an effective seal.

The seal arrangement of a turbine according to the present invention is different to known seal arrangements which may form part of a turbine for the following reasons.

Known seal arrangements are designed such that they degrade as little as possible whilst the seal arrangement is exposed to the environment which is the normal operating environment of the turbine. This is the case because, for readily appreciable reasons, it is beneficial for the seal arrangement to function for as long as possible during the operating lifetime of the turbine. Such seals may last for a number of years and/or for hundreds of operating hours of the turbine.

To the contrary the seal arrangement of the present invention is designed such that it degrades relatively quickly when the seal arrangement is exposed to the environment which is the normal operating environment of the turbine. For example, the seal arrangement of the present invention may be designed such that it is completely degraded (or degraded to the extent that it can no longer function as a seal) within a relatively short time of being exposed to the normal operating environment of the turbine (e.g. when the turbine is mounted to the exhaust outlet of a running engine).

For example, the seal arrangement may have completely degraded withn minutes of the turbine being run as part of a running engine. In further examples the seal arrangement may have completely degraded within a few hours or days of the turbine being run as part of a running engine. That is to say, the turbine will continue to have a significant operating lifetime after the seal arrangement has degraded to the extent that it is no onger a seal and/or is fully degraded.

In a particular example, the initial turbine test may be performed at relatively low temperatures, such as room temperature. The relatively low temperatures of the first environment in which the initial turbine performance test is conducted may be in the range of about 0°C to about 50°C, for example in the range of about 10°C to about 40°C and/or in the range of about 10°C to about 30°C.

The second environment in which the turbine normally operates will generally have a temperature which is relatively high compared to the temperature of the first environment. This is because the turbine will generally receive hot exhaust gas from an engine to which the turbine is attached. Examples of the range of temperatures within which the temperature of the second environment may fall include: about 100°C to about 1200°C, about 300°C to about 110000, and/or about 500°C to about 100000.

The second environment may any environment which has a temperature greater than room temperature. For example, the second environment may have a temperature in excess of at least one of: about 30°C, about 40°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 10000, about 300°C, and 500°C.

Examples of materials which may be used to form the seal ring of the sealing arrangement such that in the first environment the sealing arrangement substantially does not degrade and in the second environment the sealing arrangement degrades are paper, cardboard or wax.

It will be appreciated that the sealing arrangement (for example the sealing ring of the sealing arrangement) may be made of any appropriate material providing it substantially does not degrade in the first environment but does degrade in the second environment. In the case where the first and second environment differ in terms of temperature such that the temperature of the first environment is relatively low compared to the temperature of the second environment the material may be chosen such that it is a solid at the temperature of the first environment, but melts or vaporises to be a liquid or gas at the temperature of the second environment. In some embodiments it is preferable that the material vaporises to became a gas at the temperature of the second environment. This is because a gas is more readily expelled from the turbine leaving minima residue within the turbine.

It will be appreciated that the previously described sealing arrangement (and in particular the sealing ring of the sealing arrangement) degrades when subjected to the second environment and substantially does not degrade when subjected to the first environment, because the relatively high temperature of the second environment compared to the first environment causes the sealing arrangement (and in particular the sealing ring of the sealing arrangement) to combust, melt and/or vaporise.

Whilst, in the embodiment of the invention described above, it is a difference in temperature between the first and second environment which causes the sealing arrangement to degrade in the second environment, in other embodiments the difference between the first environment and second environment which causes the sealing arrangement (e.g. sealing ring of the sealing arrangement) to degrade in the second environment may be any appropriate environmental difference. For example, in some embodiments it is envisaged that, if the turbine is configured to be supplied with exhaust gas from an engine, the exhaust gas may include at least one substance which is either not present in air, or is present in air in relatively limited amounts. In this situation, air the first environment incudes air, whereas the second environment includes exhaust gas. Exposure of the sealing arrangement to the at least one substance within the exhaust gas during the normal operation of the turbine may lead to chemical decomposition of the sealing arrangement (e.g. the sealing ring of the sealing arrangement).

In other words, in the preceding embodiment, the first environment is an environment which includes substantially only air and the second environment includes the exhaust gases produced by the engine to which the turbine is attached. The lack, or relatively low concentration of at least one substance within the air means that the sealing arrangement substantially does not degrade. However, the sealing arrangement is formed of a particular material which, when in the presence of or subjected to a relatively high concentration of said at least one substance within the exhaust gas, the sealing arrangement is caused to chemically degrade by said at least one substance.

The applicant has found that the use of a temporary (i.e. degradable) seal arrangement has several benefits over a permanent (i.e. substantially non degradable) seal arrangement. There are two main reasons for this. First, the design of a permanent sealing arrangement would be relatively more complicated than that of a temporary seal arrangement. This is because it is inherently difficult to create a seal which has adequate performance and longevity given that the seal has to function in an environment where there are relatively high temperatures and where the valve member and actuator undergo regular movement. Furthermore, because, as previously discussed, the presence of a leakage path via the actuator conduit is not, generally, a significant fault which will result in unacceptable performance of the turbine, the implementation of a permanent seal arrangement would be a relatively expensive and time consuming measure in order to prevent engine pass off test failures, especially when prevention of leakage via the actuator conduit is not normally required during normal operating use of the turbine.

In some embodiments it is advantageous for the dimensions of the sealing arrangement (for example, seal member) to be optimised such that the volume and hence material content of the seal member is as small as possible. This will help to minimise any residue being left within the turbine once the sealing arrangement has degraded.

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.

The sealing arrangement (for example the seal member) may include a ubricant. For example, a portion of the sealing arrangement (for example the seal member) may be formed from a material which is a lubricant. In other embodiments a portion of the sealing arrangement (for example the seal member) may be impregnated with a lubricant or have a coating of lubricant. The lubricant is preferably configured to reduce friction between the seal arrangement (for example the seal member) and at least one of: the actuation member, the valve member, the turbine housing and the bush (if present). In addition the lubricant may reduce friction between the actuation member and/or actuator, and the turbine housing and/or bush (if present). The lubricant may be configured to reduce friction which may oppose movement of the actuation member and/or valve member relative to the turbine housing and/or bush (if present). The lubricant may also be configured such that when it is subjected to the second environment in which the turbine normally operates the lubricant degrades. In applications of turbine in which the initial turbine performance test includes a test which requires the actuation member and valve member to move between their respective positions in the open and closed states of the wastegate valve, the lubricant will assist in enabling the actuation member and valve member to move between their respective positions in the open and closed states of the wastegate valve, thereby assisting the turbine to pass the initial turbine performance test. An example of a suitable lubricant is a wax-type material, however, any appropriate lubricant may be used. The wax-type material may be applied as an outer layer to a portion of the sealing arrangement, such as the sealing member.

Although the previous description is related to an embodiment 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 embodiment relates 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.

The wastegate valve within the above described embodiment includes a poppet type valve, which is actuated such that substantially linear movement of an actuator is converted by a linkage to rotation of an actuation member which results in movement of the valve member of the wastegate valve between open and closed positions. It will be appreciated that any appropriate wastegate valve may be used, provided it has an open state in which gas may pass between the turbine inlet and turbine outlet via a wastegate passage and a closed state in which gas is substantially prevented from passing between the turbine inlet and the turbine outlet via the wastegate passage.

Likewise, any appropriate configuration of actuation of the wastegate valve may be used provided it is capable of effecting a change of state of the wastegate valve between the open and closed states.

Although the above described embodiment includes a sealing arrangement which comprises a seal ring, it will be appreciated that any configuration of seal arrangement may be used, provided that the seal arrangement is arranged to substantially prevent gas from passing between the turbine outlet and the actuator conduit, and provided that the sealing arrangement is degradable such that when the sealing arrangement is subjected to a first environment, in which an initial turbine performance test is conducted, the sealing arrangement substantially does not degrade, and when the sealing arrangement is subjected to a second environment, in which the turbine normally operates, the sealing arrangement degrades. For exampe, the seal arrangement may comprise a seal member of any appropriate size and/or shape.

Furthermore, the seal member may be formed of any appropriate material.

Claims

CLAIMS: 1. A turbine comprising: a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve comprising a movable valve member; the wastegate valve having an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage; and wherein the valve member is mounted to an actuation member, the actuation member passing through an actuator conduit of the turbine housing, and being movable so as to move the wastegate valve between the open and closed states; the turbine further comprising a sealing arrangement configured to provide a seal arranged to substantially prevent gas from passing from the turbine outlet into the actuator conduit; wherein the sealing arrangement is designed to degrade in a second environment corresponding to normal operating conditions of the turbine, and the sealing arrangement is designed to substantially not degrade in a first environment corresponding to an environment in which an initial turbine performance test is conducted.
2. A turbine according to claim 1, wherein the first environment differs from the second environment in that the temperature of the first environment is different to the temperature of the second environment.
3. A turbine according to claim 2, wherein the temperature of the first environment is less than the temperature of the second environment.
4. A turbine according to claim 3, wherein the temperature of the first environment falls within at least one of the group of ranges including: about 0°C to about 50°C, about 10°C to about 40°C, and about 10°C to about 30°C.
5. A turbine according to either claim 3 or claim 4, wherein the temperature of the second environment falls within at least one of the group of ranges including: about 100°C to about 1200°C, about 300°C to about 1100°C, and about 500°C to about 1000°C.
6. A turbine according to any preceding claim, wherein the valve member is mounted to the actuation member such that the valve member is located on a first side of the actuator conduit, and a portion of the actuation member is mechanically linked to an actuator or linkage configured to be linked to an actuator, wherein the portion of the actuation member which is mechanically linked to the actuator or linkage configured to be linked to the actuator is located on a second side of the actuator conduit.
7. A turbine according to any preceding claim, wherein the sealing arrangement comprises a seal member.
8. A turbine according to claim 7, wherein the seal member is disposed upon the actuation member.
9. A turbine according to claim 7 or claim 8, wherein the sea member is sandwiched between the valve member and the turbine housing.
10. A turbine according to any of claims 7 to 9, wherein the turbine further comprises a bush, the bush being received by the actuator conduit and the actuation member passing through the bush, and wherein the seal member is sandwiched between the valve member and the bush.
11. A turbine according to any of claims 7 to 10, wherein the seal member is at least in part formed from a material which is solid in the first environment, and a liquid or gas in the second environment.
12. A turbine according to claim 11, wherein the seal member is at least in part formed from wax.
13. A turbine according to any of claims 7 to 10, wherein the seal member is at least in part formed from a material which combusts in the second environment.
14. A turbine according to claim 13, wherein the seal member is at least in part formed from paper or cardboard.
15. A turbocharger or powerturbine including a turbine according to any preceding claim.
16. A method of producing a turbine, the turbine comprising: a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve comprising a movable valve member; the wastegate valve having an open state in which gas may pass between the turbine inlet and turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage; and an actuation member, the actuation member being movable so as to move the wastegate valve between the open and closed states; the method comprising: assembling the turbine, the assembling comprising passing the actuation member through an actuator conduit of the turbine housing, and sealing the actuator conduit with a sealing arrangement that substantially prevents gas from passing from the turbine outet into the actuator conduit; performing an initial turbine performance test in a first environment, the sealing arrangement being designed such that the sealing arrangement substantially does not degrade in the first environment; and operating the turbine in a second environment, the sealing arrangement being designed such that the sealing arrangement degrades in the second environment.
17. A method according to claim 16, wherein the temperature of the first environment is less than the temperature of the second environment.