GB2523855A - Turbomachine arrangement - Google Patents

Abstract

A turbomachine arrangement comprises a turbine including a housing having an exhaust gas inlet 42, and an outlet 44. A fluid storage device 46 is linked to the turbine inlet 42 by a conduit 48 and a flow control device 50 selectively enables fluid to flow from the fluid storage device 46 to the turbine inlet 42 via the fluid conduit 48. The flow control device 50, eg solenoid valve, is actuated by an actuator 56 under the control of a controller, eg ECU, 54. When a desire for rapid acceleration is detected at lower engine speeds, the actuator 56 opens the valve 50 to boost the turbomachine and reduce turbo lag. Unidirectional valves 60, 70 may be provided to prevent gas passing from the turbine inlet 42 to the storage device 46 and from the storage device 46 to the inlet manifold, respectively. The fluid storage device 46 is pressurised by the compressor of a turbocharger; in a modification, the storage device (46a, fig.3) it is pre-filled with pressurised fluid; alternatively, it may form part of another vehicle pressurised system, eg braking system.

Description

Turbomachine arrangement The present invention relates to a turbomachine arrangement. The turbomachine arrangement includes a turbine which may form part of a turbocharger. The turbomachine arrangement also includes a fluid storage device.

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 inlet including an annular inlet passageway defined between facing radial walls arranged around the turbine chamber, and an inlet volute arranged around the annular inlet passageway; 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 (which may be referred to as boost gas) 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.

Some known internal combustion engines include Exhaust Gas Recircuation (EGR).

EGR is used to reduce nitrogen oxide (NOx) emissions of an internal combustion engine. EGR works by recirculating a portion of an exhaust gas produced by the internal combustion engine back to the engine cylinders, usually via the engine intake manifold. Recirculating a portion of the exhaust gas results in a reduction in temperature of the combustion which occurs in the engine cylinders. Because NOx production requires a mixture of nitrogen and oxygen (as found in the air) exposed to high temperatures, the lower combustion temperatures resulting from EGR reduces the amount of NOx generated by the combustion of the internal combustion engine. In some known internal combustion engines a variable geometry turbine (which forms part of a turbocharger) is used to increase the pressure (also known as back pressure) of the exhaust gas. This creates a pressure differential between the exhaust gas and the engine intake such that the exhaust gas will flow via an exhaust gas recirculation channel to the engine intake. However, the creation of back pressure by the variable geometry turbine can impair the operating performance of the internal combustion engine.

In turbocharger applications which require relatively rapid changes in output power, such as when a turbocharger forms part of an automotive engine, the turbocharger may suffer from turbo lag. Turbo lag is a delay between a throttle change of an engine, which is applied in order to cause the engine to accelerate, and the resulting change in power output of the engine. Turbo lag may be observed as a slow throttle response when accelerating from idle as compared to a naturally aspirated engine. Turbo lag is caused by the time needed for the engine to produce enough exhaust so as to cause the turbocharger to rotate with enough speed to generate the boost pressure required to increase the power output of the engine.

In particular, when an engine to which a turbocharger is connected is operated at an idle speed, the rate of production of exhaust gas by the engine (which is supplied to the turbine of the turbocharger) is low. The low rate of production of exhaust gas by the engine results in the pressure of the exhaust gas being supplied to the turbine of the turbocharger being low. The low pressure of the exhaust gas supplied to the turbine of the turbocharger results in a low rotation speed of the turbine wheel and attached compressor wheel and hence a low boost gas output by the compressor to the engine intake. The low rate of supply of boost gas to the engine intake results in low engine output and hence a low rate of production of exhaust gas by the engine.

If it is desired to accelerate the engine speed from the idle speed, the low pressure of the exhaust gas supplied to the turbine cannot rapidly accelerate the turbine wheel and attached compressor wheel. Because the compressor wheel cannot be accelerated quickly, the rate at which boost gas is supplied to the engine cannot be increased quickly. As a result the engine operating speed cannot be increased rapidly and hence the pressure of the exhaust gas produced by the engine and supplied to the turbine cannot be increased quickly. This cycle results in turbo lag and hence reduced acceleration performance of the engine.

It is an object of the present invention to provide an alternative turbomachine arrangement. The alternative turbomachine arrangement may obviate or mitigate at least one disadvantage of the prior art, whether discussed above (e.g. turbo lag) or otherwise.

According to a first aspect of the present invention there is provided a turbomachine arrangement comprising a turbine including a housing, the housing defining a turbine inlet for receiving exhaust gas from an engine, a turbine outlet and a turbine chamber between the turbine inlet and the turbine outlet; and a turbine wheel located within the turbine chamber and arranged for rotation about an axis, the turbine wheel being configured to receive exhaust gas from the inlet; the turbomachine arrangement further comprising: a fluid storage device; a fluid conduit linking the fluid storage device to the turbine inlet; and a flow control device configured to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid condut and turbine inlet.

The turbomachine arrangement may further comprise a control arrangement, the control arrangement including a controller configured to control an actuator, the actuator being configured to actuate the flow control device to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid condut and turbine inlet.

The turbomachine arrangement may further comprise a uni-directional valve arrangement configured to allow fluid to pass from the fluid storage device and/or fluid conduit to the turbine inlet, and configured to substantially prevent exhaust gas from passing from the turbine inlet to the fluid storage device and/or fluid condut.

The uni-directional valve arrangement may be located and configured so as to allow fluid to pass from the flow control device to the turbine inlet, and located and configured to substantially prevent exhaust gas from passing from the turbine inlet to the flow control device.

The turbine may form part of a turbocharger, the turbocharger additionally comprising a compressor including a compressor housing, the compressor housing defining a compressor outlet for supplying boost gas to an engine intake, a compressor inlet, and a compressor chamber between the compressor inlet and the compressor outlet; and a compressor wheel located within the compressor chamber and arranged to co-rotate with said turbine wheel about said axis.

The turbomachine arrangement may further comprise a second fluid conduit linking the compressor outlet to the fluid storage device.

The turbomachine arrangement may further comprise a second uni-directional valve arrangement configured to allow boost gas to pass from the compressor outlet and/or second fluid conduit to the fluid storage device, and configured to substantially prevent gas from passing from the fluid storage device to at least one of the compressor outlet, the engine intake and the second fluid conduit.

The controller may be configured to provide a control signal to the actuator in order to control the actuator; and the controller further being configured such that the control signal is a function of at least one of the group consisting of: speed of a vehicle of which the turbomachine arrangement forms part, engine speed, pressure at turbine inlet, pressure at the compressor outlet, pressure at the engine intake manifold, state of a throttle control for the engine, rate of change of state of said throttle control, rotary speed of camshaft of the engine, rotary position of camshaft of the engine, rotary speed of crankshaft of the engine, and rotary position of crankshaft of the engine.

The controller may be configured to provide a control signal to the actuator in order to control the actuator; and wherein the controller is configured such that the control signal is co-ordinated with an exhaust gas emission pattern of the engine, whereby the actuator actuates the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel in a substantially pulsed fashion, the pulses of fluid flowing from the fluid storage device to the turbine wheel being such that they arrive at the turbine wheel at substantially the same time as pulses of exhaust gas produced by the engine, and wherein the pulses of exhaust gas are caused by cylinders of the engine producing exhaust gas at different times.

According to a second aspect of the present invention there is provided a method of operating an engine including a turbomachine arrangement, the turbomachine arrangement including a turbine comprising a housing, the housing defining a turbine inlet, a turbine outlet and a turbine chamber between the turbine inlet and the turbine outlet; and a turbine wheel located within the turbine chamber; the turbomachine arrangement further comprising a fluid storage device; a fluid conduit linking the fluid storage device to the turbine inlet; and a flow control device; and a control arrangement including a controller and an actuator linked to the flow control device; the method comprising the engine providing exhaust gas to the turbine wheel via the turbine inlet to thereby rotate the turbine wheel about an axis; and the controller controlling the actuator to actuate the flow control device to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid conduit and turbine inlet.

The turbine of the turbomachine arrangement may form part of a turbocharger, the turbocharger additionally comprising a compressor including a compressor housing, the compressor housing defining a compressor outlet, a compressor inlet, and a compressor chamber between the compressor inlet and the compressor outlet; and a compressor wheel located within the compressor chamber; the method may further comprise the turbine wheel driving the compressor wheel such that it co-rotates with said turbine wheel about said axis; and the rotation of the compressor wheel causing the compressor to supply boost gas to an engine intake.

The turbomachine arrangement may further comprise a second fluid conduit linking the compressor outlet to the fluid storage device; and the method may further comprise supplying boost gas to the fluid storage device via the second fluid conduit.

The method may further comprise the controller providing a control signal to the actuator in order to control the actuator; and wherein the control signal is a function of at least one of the group consisting of: speed of a vehicle of which the turbomachine arrangement forms part, engine speed, pressure at turbine inlet, pressure at the compressor outlet, pressure at the engine intake manifold, state of a throttle control for the engine, rate of change of the state of said throttle control, rotary speed of camshaft of the engine, rotary position of camshaft of the engine, rotary speed of crankshaft of the engine, and rotary position of crankshaft of the engine.

The method may further comprise the controller providing a control signal to the actuator in order to control the actuator; and the controller coordinating the control signal with an exhaust gas emission pattern of the engine, whereby the actuator actuates the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel in a substantially pulsed fashion, the pulses of fluid flowing from the fluid storage device to the turbine wheel being such that they arrive at the turbine wheel at substantially the same time as pulses of exhaust gas produced by the engine, and wherein the pulses of exhaust gas are caused by cylinders of the engine producing exhaust gas at different times.

Specific embodiments of the present nvention 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 view of a turbomachine arrangement according to an embodiment of the present invention; and Figure 3 shows a schematic view of a further turbomachine arrangement according to an embodiment of the present invention.

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 ol a common turbocharger shaft S 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 S rotates about an axis A 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 in Figure 1) to which the turbocharger may be attached. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet 11 and may deliver boost air to an inlet manifold of the engine (again not shown in Figure 1) via the volute 12 and then the outlet 25.

The exhaust gas inlet 9 is defined in part 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.

Figure 2 shows a schematic view of a turbomachine arrangement 30 according to an embodiment of the present invention. The turbomachine arrangement 30 comprises a turbocharger 32. The turbocharger 32 shown within Figure 2 has been illustrated in a very schematic way. None of the components within the turbocharger 32 have been shown. This is because a turbocharger is a well known device and, as such, discussion of its structure and its method of operation are not included here. It will be appreciated that the turbocharger 32 may be any appropriate turbocharger, for example, of the same type as the known turbocharger shown in figure 1.

The turbomachine arrangement 30 is connected to an engine 32. Again, the engine is shown schematically within figure 2. The engine 34 in this embodiment includes four cylinders represented by the circles 36. In use, air is supplied to each of the cylinders via an engine inlet manifold 38. Exhaust gas for each of the cylinder 36 of the engine 34 is supplied to an exhaust manifold 40. It will be appreciated that in other embodiments, the turbomachine arrangement may be connected to any appropriate internal combustion engine have any appropriate number of cylinders.

The turbine (not shown in detail within figure 2) of the turbocharger 32 includes a housing, the housing defining a turbine inlet (shown schematically as 42) for receiving exhaust gas from the engine 34 (and, in particular, in this case, from the exhaust manifold 40 of the engine 34). The housing of the turbine also defines a turbine outlet (shown schematically as 44).

A turbine chamber (not shown) is located between the turbine inlet 42 and turbine outlet 44. A turbine wheel (again not shown) is located within the turbine chamber and is arranged for rotation about an axis. The turbine wheel is configured to receive exhaust gas from the turbine inlet 42.

The turbomachine arrangement 30 further comprises a fluid storage device 46. The fluid storage device may be any appropriate device capable of storing fluid. For example, in one embodiment, the fluid storage device is a tank for storing compressed air.

The turbomachine arrangement 30 also comprises a fluid conduit 48 linking the fluid storage device 46 to the turbine inlet 42.

In addition, the turbomachine arrangement 30 includes a flow control device 50 which is configured to selectively enable fluid to flow from the fluid storage device 46 to the turbine wheel (not shown) via the fluid conduit 48 and turbine inlet 42. In order to selectively enable fluid to flow from the fluid storage device 46 to the turbine wheel, the flow control device may have a first (open) state in which fluid can flow through the flow control device 50 from the fluid storage device 46 to the turbine wheel, and a second (closed) state in which fluid flow through the flow control device 50 from the fluid storage device 46 to the turbine wheel is relatively restricted (compared to that in the open state) or substantially prevented. The state of the flow control device (i.e. whether it is in the open or closed state) determines whether fluid can flow through the flow control device, or whether flow through the flow control device is relatively restricted (or substantially prevented) -hence the flow control device is configured to selectively enable fluid to flow from the fluid storage device 46 to the turbine wheel.

The turbomachine arrangement 30 further comprises a control arrangement 52. The control arrangement 52 includes a controller 54 configured to control an actuator 56.

The actuator is configured to actuate the flow control device 50 to selectively enable fluid to flow from the fluid storage device 46 to turbine wheel via the flud conduit 48 and turbine inlet 42. The flow control device of the present invention may be any appropriate device for controlling the flow of a fluid. For example, the flow control device may comprise a valve. Many types of valve are well known within the art, and any appropriate valve may be utilised as the flow control device of the present invention. For example, the flow control device may comprise a solenoid valve.

Following from the above, in some embodiments the actuator may be configured to actuate the flow control device to selectively enable fluid to flow from the fluid storage device to the turbine wheel. This may be achieved by the actuator moving between a first position (in which the flow control device is in the first (open) state) and a second position (in which the flow control device is in the second (closed) state).

The controller 54 may control the actuator 56 by providing a control signal to the actuator 56. Within the embodiment shown in Figure 2 the control signal is represented schematically by line 58. The control signal maybe conveyed between the controller 54 and actuator 56 by any appropriate means. For example, the control signal may be conveyed by a physical lnk such as a mechanical, electrical or optical link. In other embodiments, the control signal 58 may be conveyed by a non-physical link, for example wireless, e.g. electromagnetic radiation. Details of the way in which the controller controls the actuator by use of a control signal is given later within this

description.

It will be appreciated that the controller 54 may be any appropriate controller provided that it can control the actuator such that the actuator can actuate the flow control device as previously discussed. For example, the controller may be an engine control unit (ECU) or portion of an ECU. Alternatively, the controller may be separate from an ECU.

A turbomachine arrangement according to the present invention may, as is the case with the embodiment shown in figure 2, comprise a unidirectional valve arrangement 60. The unidirectional valve arrangement is configured to allow fluid to pass from the fluid storage device 46 and/or fluid conduit 48 to the turbine inlet 42. The unidirectional valve arrangement 60 is also configured to substantially prevent exhaust gas which may be present in the turbine inlet 42 and/or engine exhaust manifold 40 to the fluid storage device 46 and/or the fluid conduit.

It will be appreciated that the effect of the unidirectional valve arrangement depends upon where the unidirectional valve arrangement is located relative to the fluid storage device, the fluid conduit, the flow control device, and the turbine inlet. For example, in the embodiment of the invention shown in figure 2, the unidirectional valve arrangement 60 is located between the fluid flow conduit 48 and the turbine inlet 42.

Consequently, with the unidirectional valve arrangement 60 being located in this position, fluid can flow via the unidirectional valve arrangement from the fluid storage device and fluid conduit to the turbine inet, but cannot flow from the turbine inlet 42 to the fluid conduit and fluid storage device 46. If instead the unidirectional valve arrangement were to be located at the junction between the fluid storage device and fluid conduit 48 then the unidirectional valve arrangement would be configured to allow fluid to pass via the unidirectional valve arrangement from the fluid storage device to the fluid conduit (and then to the turbine inlet). Furthermore, if the unidirectional valve arrangement is located in this position then the unidirectional valve arrangement would substantially prevent fluid flow from the fluid conduit to the fluid storage device.

Within the embodiment shown in figure 2 the unidirectional valve arrangement is located and configured so as to allow fluid to pass from the flow control device 50 to the turbine inlet 42; and also such that the unidirectional valve arrangement will substantially prevent exhaust gas from passing from the turbine inlet 42 to the flow control device. In some applications, preventing exhaust gas from passing from the turbine inlet to the flow control device may be advantageous. For example, the exhaust gas may have a high temperature and/or may contain contaminants which may adversely affect the flow control device. For example the flow control device may not operate correctly at the high temperatures of the exhaust gas and/or may not operate correctly when exposed to contaminants within the exhaust gas.

Consequently, preventing exhaust gas from passing from the turbine inlet to the flow control device may prevent the flow control device from being adversely affected by exhaust gas.

As well as a turbine, the turbocharger 32 of the turbomachine arrangement 30 shown in figure 2 also includes a compressor (not shown). The compressor includes a compressor housing, the compressor housing defining a compressor outlet 62 for supplying boost gas to an engine intake (e.g. engine inlet manifold 38).

In the embodiment shown in figure 2 an intercooler 64 is located between the compressor outlet 62 and inlet manifold 38. However it will be appreciated that in other embodiments there need not be an intercooler.

The compressor housing also defines a compressor inlet 66 and a compressor chamber (not shown) between the compressor inlet and compressor outlet 62. A compressor wheel is located within the compressor chamber and arranged to co-rotate with the turbine wheel. The compressor wheel and turbine wheel may be located at opposite ends of a shaft (sometimes referred to as a turbocharger shaft) in order that they co-rotate. As before, further details of operation of the compressor portion of the turbocharger are omitted because turbochargers are well known as is the way in which they operate.

The turbomachine arrangement 30 further comprises a second fluid conduit 68 which links the compressor outlet 62 (in this case via intercooler 64, although this need not be the case in other embodiments) to the fluid storage device 46.

The turbomachine arrangement further comprises a second unidirectional valve arrangement 70. The second unidirectional valve arrangement 70 is configured to allow boost exhaust gas to pass from the compressor outlet 62 to the fluid storage device 46. The valve arrangement 70 is also configured to substantially prevent gas from passing from the fluid storage tank 46 to the compressor outlet 62. The valve arrangement 70 also prevents gas from passing from the second fluid conduit 68 to the compressor outlet 62. Furthermore, the valve arrangement 70 prevents gas from passing from the fluid storage device 46 to the inlet manifold 38 of the engne 34.

As is the case with the first unidirectional valve arrangement, the location of the second unidirectional valve arrangement affects the functioning of the unidirectional valve arrangement within the turbomachine arrangement. In particular, due to the location of the unidirectional valve arrangement 70 shown in figure 2, the valve arrangement 70 allows boost gas from the compressor outlet 62 to pass into the second fluid conduit 68 and hence fluid storage device 46. In addition, the valve arrangement 70 does not permit fluid from the fluid storage tank 46 and second fluid conduit 68 to pass to the compressor outlet 62 or an engine inlet manifold 38. In other embodiments in which the second unidirectional valve arrangement is located at a junction between the second fluid conduit and fluid storage device, then the second unidirectional valve arrangement will function so as to allow gas from the compressor inlet and second fluid conduit to pass into the fluid storage device. In addition, in this position the second unidirectional valve arrangement will substantially prevent fluid from passing from the fluid storage device into the second fluid conduit and to the compressor outlet.

Furthermore, in this position, the second unidirectional valve arrangement will substantially prevent fluid from passing from the fluid storage device to the inlet manifold of the engine.

The second unidirectional valve arrangement serves to allow the fluid storage device to collect the fluid (in this case boost gas which is produced by the compressor) without allowing any fluid which is stored in the fluid storage device to undesirably leak, whether that leak be to the compressor outlet (and hence potentially to atmosphere) or the engine inlet manifold.

The second unidirectional valve arrangement may be configured such that it permits gas from the compressor outlet to pass into the fluid storage device 46 only when the pressure of the gas produced by the compressor which reaches the second unidirectional valve arrangement is greater than a predetermined amount. For example, the predetermined amount may be about 1.7 atmospheres. By ensuring that no gas is allowed to be diverted from the engine inlet 38 to the fluid storage device 46 via the second fluid conduit 68 until the pressure of the gas at the second unidirectional valve arrangement exceeds a predetermined level, this will help to ensure that gas produced by the compressor is not directed away from the engine intake 38, thereby negatively effecting engine acceleration performance, until the pressure of the gas at the engine inlet is sufficiently high such that redirecting some of the gas from the engine inlet will have limited adverse effect on the engine acceleration performance. In some embodiments, the second unidirectional valve arrangement is configured to maintain an open state (i.e. permit gas from the compressor outlet to pass into the fluid storage device 46) until the air pressure in the storage tank is within a predetermined range of the air pressure in the intake manifold. The balance state of the second unidirectional valve arrangement may be that the air pressure in the tank plus about 1.7 atmospheres is equal to the air pressure in the intake manifold. Of course, in other embodiments the balance state of the second unidirectional valve arrangement may be that the air pressure in the tank plus any appropriate amount is equal to the air pressure in the intake manifold.

In some embodiments the turbomachine arrangement may include a second flow control device (shown in broken lines and indicated by 50a), which is configured to selectively enable fluid to flow from the engine inlet manifold 38 to the fluid storage device 46 via the second fluid conduit. In order to selectively enable fluid to flow from the engine inlet manifold 38 to the fluid storage device 46, the second flow control device may have a first (open) state in which fluid can flow through the second flow control device 50a from the engine inlet manifold 38 to the fluid storage device 46, and a second (closed) state in which fluid flow through the flow control device 50a from the engine inlet manifold 38 to the fluid storage device 46 is relatively restricted (compared to that in the open state) or substantially prevented. The state of the second flow control device (i.e. whether it is in the open or closed state) determines whether fluid can flow through the second flow control device, or whether flow through the flow control device is relatively restricted (or substantially prevented) -hence the flow control device is configured to selectively enable fluid to flow from the engine inlet manifold 38 to the fluid storage device 46.

In embodiments of the turbomachine arrangement which include a second flow control device 50a, the controller 54 may be configured to control a second actuator (again shown in dotted lines and indicated as 56a). The second actuator is configured to actuate the second flow control device 50a to selectively enable fluid to flow from the engine inlet manifold 38 to the fluid storage device 46 via the second fluid conduit 68.

The second flow control device of the present invention may be any appropriate device for controlling the flow of a fluid. For example, the second flow control device may comprise a valve. Many types of valve are well known within the art, and any appropriate valve may be utilised as the second flow control device of the present invention. For example, the second flow control device may comprise a soenoid valve.

The controller 54 may control the second actuator 56a by providing a control signal to the actuator 56a. Within the embodiment shown in Figure 2 the control signal is represented schematically by broken line 58a. The control signal maybe conveyed between the controller 54 and actuator 56a by any appropriate means. For example, the control signal may be conveyed by a physical link such as a mechanical, electrical or optical link. In other embodiments, the control signal 58a may be conveyed by a non-physical link, for example wireless, e.g. electromagnetic radiation.

The controller 54 may be configured to control the second actuator 56a to actuate the second flow control device 50a such that when the pressure in the intake manifold is greater than a predetermined reference value (for example, about 1.7 atmospheres) the second actuator (and hence second flow control device) will be in the open state.

The controller 54 may also be configured to control the second actuator 56a to actuate the second flow control device 50a such that the second actuator (and hence second flaw control device) will remain in the open state (when the pressure in the intake manifold is greater than a predetermined reference value) until the air pressure in the storage tank is within a predetermined range of the air pressure in the intake manifold.

In embodiments of the invention which include a second flow control device 50a, as before described, the second unidirectional valve 70 may be configured such that it substantially prevents fluid flow to engine intake manifold from the storage tank.

The layout of the components within the turbomachine arrangement shown in figure 2 and how the turbomachine arrangement is connected to an engine have been discussed. The operation of the turbocharger arrangement shown in figure 2 is now discussed.

As mentioned above, in turbochargers which require relatively rapid changes in output power, such as when the turbocharger forms part of an automotive engine, the turbocharger may suffer from turbo lag. Turbo lag is a delay between a throttle change of an engine, which is applied in order to cause the engine to accelerate, and the resulting change in power output to the engine. Turbo lag may be observed as a slow throttle response when accelerating from idle as compared to a naturally aspirated engine. Turbo lag is caused by the time needed for the engine to produce enough exhaust so as to cause the turbocharger to rotate with enough speed to generate the boost pressure required to increase the power output of the engine.

In particular, when an engine to which a turbocharger is connected is operated at an idle speed, the rate of production of exhaust gas by the engine, which is supplied to the turbine of the turbocharger, is low. The low rate of production of exhaust gas by the engine results in the pressure of the exhaust gas being supplied to the turbine of the turbocharger being low. The low pressure of the exhaust gas supplied to the turbine of the turbocharger results in a low rotation speed of the turbine wheel and attached compressor wheel and hence a low boost gas output by the compressor to the engine intake. The low rate of supply of boost gas to the engine intake results in a low engine output and hence a low rate of production of exhaust gas by the engine.

If it is desired to accelerate the engine speed from the idle speed a throttle signal may be sent to the engine by a user in order to indicate that it is desired for the engine to be accelerated. The low pressure of the exhaust gas supplied to the turbine when the engine is operating at the idle speed cannot rapidly accelerate the turbine wheel and attached compressor wheel. Because the compressor wheel cannot be accelerated quickly, the rate at which boost gas is supplied to the engine by the compressor of the turbocharger cannot be increased quickly. As a result the engine speed cannot be increased rapidly and hence the pressure of the exhaust gas produced by the engine and supplied to the turbine of the turbocharger cannot be increased quickly. This turbo lag results in reduced acceleration performance of the engine.

A turbomachine arrangement according to the present invention obviates or mitigates the effect turbo lag would otherwise have on the acceleration performance of an engine to which the turbomachine arrangement is connected. This is achieved as follows.

The fluid storage device when in use contains a pressurised fluid, such as pressurised air. The pressurised fluid may be at any appropriate pressure. The pressure of the pressurised fluid may be greater than atmospheric pressure. For example, a pressurised fluid may have a pressure of between about 1.2 atmospheres to 2 atmospheres.

When the controller 54 detects that rapid engine acceleration is desired the controller 54 controls the actuator 56 such that the actuator 56 actuates the flow control device such that it enables fluid from the fluid storage device 46 to flow from the fluid storage device 46 to the turbine wheel via the fluid conduit 48 and turbine inlet 42.

Consequently, the pressurised fluid witftn the fluid storage device flows to the turbine inlet and turbine wheel and thus increases the pressure at the turbine wheel.

Increased pressure at the turbine wheel will enable to the turbine wheel and attached compressor wheel to accelerate relatively rapidly (when compared to that when the turbine wheel is not at an increased pressure due to fluid flowing from the fluid storage device to the turbine wheel). This relatively rapid acceleration of the compressor wheel results in the relatively rapid increase in rate at which boost gas can be supplied by the compressor of the turbocharger to the engine. This increase in rate in which the boost gas can be supplied to the engine may manifest itself as a relatively rapid increase in boost gas pressure at the engine inlet manifold. The increase in the rate at which boost gas is supplied to the engine will result in an increase in the rate at which the engine operating speed can be increased (i.e. in an increase in the rate acceleration of the engine operating speed). Consequently, turbo lag is obviated or mitigated.

Furthermore, once the engine operating speed has increased the exhaust gas output (and hence the pressure of the exhaust gas produced by the engine and supplied to the turbine of the turbocharger) will be increased. This will assist if further acceleration of the engine operating speed is required.

When rapid engine acceleration is no longer required the controller 54 controls the actuator 56 such that the actuator 56 actuates the flow control device such that it substantially prevents fluid from the fluid storage device 46 flowing from the fluid storage device 46 to the turbine wheel via the fluid conduit 48 and turbine inlet 42. This conserved the fluid stored in the fluid storage device and enables the amount of fluid stored in the Iluid storage device to be replenished via the second fluid conduit 68. The duration of time for which the controller causes the flow control device to enable fluid flow to the turbine wheel from the fluid storage device before the controller causes the flow control device to substantially prevent fluid flow to the turbine wheel from the fluid storage device may be any appropriate amount of time in order to enable the turbine wheel to be sufficiently accelerated by the fluid provided from the fluid storage device.

For example, the duration may be up to about one second, up to about O.ls or up to about 0.Ols.

In some embodiments the controller 54 may control the actuator 56 such that the actuator 56 actuates the flow control devce such that it substantially prevents fluid from the fluid storage device 46 flowing from the fluid storage device 46 to the turbine wheel via the fluid conduit 48 and turbine inlet 42 in situations where rapid engine acceleration is still required but when another criteria is satisfied. For example, the flow control device may substantially prevent fluid from the fluid storage device 46 flowing from the fluid storage device 46 to the turbine wheel when the engine speed is greater than a high engine reference speed for out of function (for example about 1400 rpm).

As previously discussed, the controller 54 controls the actuator 56 in order that the actuator 56 actuates the flow control device. In order to do so, the controller provides a control signal 58 to the actuator 56. This control signal 58 supplied by the controller 54 to the actuator 56 may be a function of at least one input signal provided to the controller 54. Figure 2 shows schematically four input signals 72 being supplied to the controller 54. However, it will be appreciated that any appropriate number (e.g. at least one) of input signals may be provided to the controller and the controller may be configured such that the control signal produced by the controller is a function of said one or more input signals.

The at least one input signal may be a function of at least one of the speed of a vehicle of which the turbomachine arrangement forms part, the engine speed, the pressure at the inlet of the turbocharger turbine, the state of a throttle control for the engine to which the turbomachine arrangement is connected, the rate of change of the state of said throttle control, the rotary speed of a camshaft of the engine to which the turbomachine arrangement is connected, the rotary position of said camshaft, the rotary speed of a crankshaft of the engine to which the turbomachine arrangement is connected, and the rotary position of said crankshaft. It would be appreciated by a person skilled in the art that any appropriate sensor arrangement may be used to provide at least one input signal to the controller which is a function of one of the propertes listed above.

It will be appreciated that in other embodiments the control signal produced by the controller may be a function of any appropriate parameter or combination of parameters of the turbomachine arrangement, engine to which the turbomachine arrangement is connected and/or vehicle of which the turbomachine arrangement and engine form part.

In some embodiments of the invention in which the turbomachine arrangement includes a controller configured to provide a control signal to the actuator in order to control the actuator, the controller may be configured such that the control signal is coordinated with an exhaust gas emission pattern of the engine.

Referring once again to figure 2, it can be seen that the engine 34 noludes four cylinders 36 which are each supplied by the inlet manifold 38 and which each supply exhaust to the exhaust manifold 40. In some engines the combustion cycle of each cylinder may be out of phase with on another. Consequently, in such arrangements, the exhaust gas at the exhaust manifold may not have a substantially constant pressure, but a pressure which varies periodically-the pressure being a maximum at times when one of cylinders has produced exhaust gas. Because the pressure of the exhaust gas at the exhaust manifold (and hence at the turbine inlet) varies periodically as a function of when each cylinder produces exhaust, the exhaust gas produced by the engine may be referred to as pulses of exhaust gas. The periodic change in exhaust manifold pressure may be referred to as an exhaust emission pattern of the engine.

In some embodiments of the invention the controller is configured suci the control signal is coordinated with an exhaust gas emission pattern of the engine. In such embodiments the control signal produced by the controller may be such that the actuator actuates the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel in a substantially pulsed fashion. The pulses of fluid flowing from the fluid storage device to the turbine wheel may be such that the pulses of fluid flowing from the fluid storage device to the turbine wheel arrive at the turbine wheel at substantially the same time as pulses of exhaust gas produced by the engine (for example in the case of an engine with several cylinders, at substantially the same time that the exhaust gas produced by each cylinder reaches the turbine wheel of the turbocharger via the exhaust manifold).

By providing pulses of fluid from the fluid storage device to the turbine wheel at substantially the same time as the pulses of exhaust from each of the cylinders of the engine arrive at the turbine wheel, this will increase the maximum pressure which is exerted on the turbine wheel. This in turn will maximise the performance of the turbine wheel. By increasing the performance of the turbine, the boost gas pressure produced by the compressor of the turbocharger may be improved. This may result in an improvement of the performance of the engine connected to the turbomachine arrangement.

An example of control signal which could be produced by the controller in order to actuate the actuator in the manner required to produce pulse fluid flow from the fluid storage device to the turbine wheel is an oscillating signal. One such signal is a pulse width modulated (PWM) signal. In order for the controller to produce a control signal which results in fluid from the fluid storage device being pulsed such that the pulses arrive at substantially the same time as pulses of exhaust gas produced by the engine, it may be necessary to provide the controller with an input signal which is a function of when pulses of exhaust gas are produced by the engine. Any appropriate input signal which is a function of when the pulses of exhaust gas are produced by the engine may be used. For example, sensors which measure the position and/or speed of the crankshaft and/or camshaft of the engine may be used. This is because it is rotation of the crankshaft and camshafts which govern the combustion cycle of each of the cylinders of the engine and hence the position/speed of each of the crankshaft and camshafts is directly linked to the time at which each cylinder produces a pulse of exhaust gas.

In some embodiments the frequency f of the oscillating control signal may be given by: (1) 60n where n is the number of rotations of the crankshaft required for a full combustion cycle of one of the cylinders (usually 2), N is the number of cylinders that the engine has and S is the engine speed in revolutions per minute (rpm).

Of course it will be appreciated that as the speed of the engine changes, the frequency of the oscillating control signal produced by the controller will have to change according to the formula above.

As previously discussed, the controller 54 may be configured to provide a control signal to the actuator in order to control the actuator, the control signal being a function of at least one input signal 72. One example of control logic which may be implemented by the controller 54 such that the controller can produce the control signal 58 as a function of various input signals 72 is given below. The control logic described below operates on the basis that pressurised fluid from the fluid storage device will only need to be provided to the turbine wheel of the turbocharger when the speed of the engine to which the turbomachine arrangement is connected is relatively low and also only when rapid engine acceleration is required. In other embodiments, basis for the control logic may be different.

First, the controller is provided with an input signal 72 which is a function of the speed of a vehicle of which the turbomachine arrangement and engine form part. Any appropriate speed sensor may be used to sense the speed of the vehicle and provide an input signal to the controller based on the sensed speed. Based on the input signal provided to the controller which is a function of the vehicle speed, the controller checks that the vehicle speed is greater than zero in order to confirm that the vehicle is in motion. If the vehicle is not in motion, no rapid acceleration of the engine will be required and consequently the controller 54 will output a control signal which controls the actuator 56 such that the flow control device is placed in a closed state, thereby substantially preventing fluid flowing from the fluid storage device to the turbine wheel.

If the vehicle speed is greater than zero, such that vehicle is in motion, then the control logic advances to the next step.

The controller 54 is provided with an input signal 72 which is a function of the speed of the engine (or portion of the engine) to which the turbomachine arrangement is connected. Any appropriate speed sensor may be used which may sense the speed of any appropriate part of the engine. For example, a sensor which senses the speed of rotation of the crankshaft or a camshaft may be used. The controller 54 is configured such that if the input signal 72 which is a function of engine speed indicates that the engine speed is less than a low reference speed, or the engine speed is greater than a high engine reference speed for out of function (for example about 1400 rpm), then the controller produces a control signal 58 which controls the actuator so as to actuate the flow control device to a closed state which substantially prevents fluid flow from the fluid storage device to the turbine wheeL This is because, if the engine speed is too low (i.e. lower than idle speed) or higher than a particular engine speed for which turbo lag is not a significant problem, then rapid acceleration of the turbocharger and hence attached engine will not be required. If the engine speed is greater than or equal to the low reference speed and the engine speed is less than or equal to the high engine reference speed, then the control logic advances to the next step.

The controller 54 may receive an input signal 72 which is a function of the air pressure at an intake (e.g. intake manifold) of the engine to which the turbomachine arrangement is connected. Any appropriate sensor may be used to detect air pressure at the intake and provide an input signal indicative of such to the controller 54. The controller 54 may be configured such that if the intake air pressure is greater than a high pressure reference then the controller 54 may be configured to output a control signal 58 to the actuator which causes the actuator to actuate the flow control device in order to substantially prevent fluid from the fluid storage device to the turbine wheel (i.e. actuate the flow control device into a closed state). This is because if the pressure of the air at the intake to the engine is relatively high then, not only is further intake pressure unlikely to be required, but further increased air pressure at the engine intake may result in adverse performance of the engine and/or turbocharger. An example of a high pressure reference is about 1.5 atmospheres, although in other embodiments any high pressure reference may be used. Provided the intake air pressure is less than or equal to the high pressure reference, then the control logic will proceed to the next step.

The controller 54 may be provided with an input signal which is a function of a state of the throttle of the engine to which the turbomachine arrangement is connected. For example, if the throttle control includes a portion which adopts a position which depends on or determines the throttle state of the engine, then a sensor may be used to measure the position of such a moveable portion because the position of the moveable portion is indicative of the throttle state of the engine. For example, a sensor may measure the position of an accelerator pedal of the engine. In embodiments in which the engine throttle is controlled electronically then the controller may determine the state of the throttle of the engine by measuring a variable which is used to control the throttle state. For example, if an engine control unit of the engine includes a variable within its memory which is indicative of a desired throttle position, then the controller may measure the variable indicative of the desired throttle position in order to determine the throttle state.

The throttle state may be described as a throttle percentage where the throttle percentage L7. is given by = iüo(i -T1) (2) rnflxrnifl where T is a value indicative of the throttle state, Tmin is a value indicative of a minimum possible throttle state and Tm is a value indicative of a maximum possible throttle state.

If the throttle percentage is less than a reference throttle percentage for out of function then the controller may be configured to send a control signal 58 to the actuator which actuates the flow control device in order to substantially prevent fluid from flowing the fluid storage device to the turbine wheel (i.e. closed state of flow control device). This is because unless particularly rapid acceleration of the engine, which is indicated by a high throttle percentage (i.e. greater than the reference throttle percentage) is required, then rapid acceleration of the turbocharger using the turbocharger arrangement of the present invention will not be required. An example of a reference throttle percentage is 60% although any appropriate throttle percentage may be used as the reference throttle percentage. If the throttle percentage is greater than or equal to the reference throttle percentage, then the control logic may advance to the next step.

As previously discussed, the controller may be provided with an input signal which is a function of the state of the engine throttle control. The controller may use this information in order to calculate a throttle change rate. A throttle change rate may be measured by measuring the speed of movement of a moving part of the throttle control.

Alternatively, the throttle change rate may be calculated by measuring the change in the throttle state for a given unit of time. If the throttle change rate is greater than or equal to a reference rate (for example 3000% per second -although any appropriate reference rate may be used) then the controller may send a control signal 58 to the actuator such that the actuator can actuate the flow control device to enable fluid to flow from the fluid storage device 46 to the turbine wheel (i.e. open state of flow control device).

Measuring the throttle change rate as well as the throttle state may be important for determining whether fluid should be provided from the fluid storage device to the turbine. This is because, rapid acceleration of the engine is not just linked to throttle state (which is more closely linked to the speed of the engine), but is also linked to the speed at which the throttle state is changed (also referred to as the throttle change rate).

Once the control signal has been provided to the actuator which causes the actuator to actuate the flow control device to enable fluid flow from the fluid storage device to the turbine wheel (i.e. open state of flow control device), the controller 54 may monitor at least one input signal 72 in order to demine when the controller should provide a control signal to the actuator in order to actuate the flow control device such that fluid flow from the fluid storage device to the turbine wheel is substantially prevented (i.e. place the flow control device in the closed state). For example, the controller may monitor at least one of vehicle speed, engine intake pressure and throttle state. If at least one of these monitored variables enters a particular range then the controller may output a control signal which causes the actuator to close the fluid control device such that fluid flow from the fluid storage device to the turbine wheel is substantially prevented. For example, this may happen if the vehicle speed drops to zero, if the engine speed falls below a low reference speed or exceeds a high engine reference speed, if the engine intake pressure is greater than a reference pressure for out of function, or if the throttle state is less than a reference state (e.g. throttle percentage is less than a reference throttle percentage) for out of function.

It will be appreciated that in some embodiments of turbomachine arrangement according to the present invention the controller may implement control logic which differs from the control logic described above. Any appropriate control ogic may be used provided that the controller provides a control signal to the actuator in order to actuate the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel when required, and provided that the controller provides a control signal to the actuator which causes the actuator to actuate the flow control device such that the flow control device substantially prevents the flow of fluid from the fluid storage device to the turbine wheel when such flow is not required. In other embodiments of control logic, the control logic may include any number of the steps described above and in any desired order. Within any of the steps described above, instead of the control logic passing to the next step, the controller may provide a control signal to the actuator in order to actuate the flow control device to enable fluid to Ilow from the fluid storage device to the turbine wheel (i.e. in order for the actuator to place the flow control device in an open state).

It will be appreciated that in other embodiments of the invention any other appropriate characteristic of the turbomachine arrangement (and engine and/or vehicle of which the engine forms part) may be monitored by the controller via an appropriate input signal to the controller thereby enabling the controller to use such an input signal to produce an appropriate control signal for the actuator.

Figure 3 shows an alternative turbomachine arrangement according a further embodiment of the present invention. Features of the embodiment shown in figure 3 which correspond to those shown in figure 2 have been given the same reference numerals. It can be seen that the embodiment of turbomachine arrangement 30a shown in figure 3 differs from that shown in figure 2 in that fluid storage device 46a shown in figure 3 differs from that in figure 2. In addition, the embodiment shown in figure 3 has no second fluid conduit or second unidirectional valve arrangement which links the compressor outlet of the turbocharger with the fluid storage device.

Because the fluid storage device 46a is not replenished by relatively high pressure gas produced by the compressor of the turbocharger, the fluid storage device 46a stores fluid from another source. For example, the fluid storage device 46a may be a vessel which is pre-filled with pressurised flud and then connected to the turbomachine arrangement. When the pressurised fluid within the fluid storage device is depleted, the fluid storage device can be removed and either refilled or replaced with another fluid storage device containing pressurised fluid.

In other embodiments, the fluid storage device 46a may form part of another pressurised system of a vehicle of which the turbomachine arrangement forms part.

For example, some known vehicles utilise pressurised air as part of their braking system. When a turbomachine arrangement according to an embodiment of the present invention forms part of a vehicle which includes another pressurised system, then the fluid storage device of the turbomachine arrangement and the fluid storage device required for the other pressurised system of the vehicle may be one and the same. Alternatively, the other pressurised system of the vehicle may include a pressurising device which is used to either pressurise the turbomachine arrangement directly or which may be used to pressurise the fluid storage device which forms part of the turbomachine arrangement. In this case, the pressurising device of the other pressurised system may be used to pressurise (i.e. supply pressurised fluid to) the fluid storage device 46a.

It will be appreciated that any other appropriate method of filling the fluid storage device of embodiments of the present invention with pressurised fluid may be used.

The embodiments of turbomachine arrangement described above both include a turbocharger. In other embodiments, this need not be to the case. For example, in some embodiments of turbomachine arrangement according to the present invention, the turbocharger of the previously described embodiments may be replaced by any appropriate turbomachine. For example, a turbomachine arrangement according to the present invention may include a turbine, but the turbine may not form part of a turbomachine which includes a compressor. In particular, a turbomachine arrangement according to the present invention may include turbine which forms part of a power turbine, for example a power turbine which converts the rotation of the turbine wheel into electrical power.

Although the turbine machine arrangement described above operates in conjunction with gas (in particular air) it will be appreciated that turbomachine arrangements according to the present invention may operate in conjunction with any appropriate fluid, for example a liquid. For example, the turbocharger turbine may have a liquid supplied to it in order to rotate the turbine wheel. The turbocharger compressor may act so as to compress a fluid. The fluid storage device may store a liquid and supply a liquid to the turbine wheel.

Although none of the turbines according to the present invention previously described incorporate a variable geometry arrangement, it will be appreciated that other embodiments of the present invention may include a variable geometry arrangement.

For example, any of the embodiments described above may be modified so as to include a variable geometry arrangement.

The variable geometry arrangement may be configured to selectively change at least one characteristic of the turbine inlet. For example, the turbine may include a swing-vane-type arrangement, as is well-known in the art, which is capable of changing the swirl angle of the substantially annular array of vanes.

In another variable geometry arrangement the general annular inlet passageway may be defined between a first wall and a facing second wall. The variable geometry arrangement is configured to move the first wall relative to the second wall in a direction substantially parallel to the turbine axis in order to vary the size of the inlet passageway. Changing the size of the inlet passageway will change the speed, in use, of the gas which passes through the inlet passageway. For example, for a given mass flow rate of gas provided to the first and second flow passages, the larger the axial size of the inlet passageway, the slower gas will pass through the inlet passageway.

The way in which various variable geometry arrangements operate is well-known in the art. Consequently, further explanation of the operation of variable geometry arrangements is omitted. It will be appreciated that although only two types of variable geometry arrangement have been discussed, any appropriate variable geometry arrangement may be used provided it is capable of selectively changing at least one characteristic of the turbine inlet.

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.

It will be appreciated that a turbine according to an embodiment of the present invention, for example any of the turbines described above, may additionally include a valve controlled bypass port referred to as a wastegate. The wastegate may be configured to enable control of the rotation speed of the turbine. Additionally, ii the turbine forms part of a turbocharger, the wastegate may be used to control the boost pressure of the gas output by the compressor of the turbocharger. The bypass port provides a conduit between the inlet of a turbine and either the outlet of the turbine or atmosphere. Consequently, when the wastegate valve is opened, to thereby open the bypass port, in use, it allows at least some of the exhaust gas to bypass the turbine wheel.

Claims (14)

1. CLAIMS: 1. A turbomachine arrangement comprising: a turbine including: a housing, the housing defining a turbine inlet for receving exhaust gas from an engine, a turbine outlet and a turbine chamber between the turbine inlet and the turbine outlet; and a turbine wheel located within the turbine chamber and arranged for rotation about an axis, the turbine wheel being configured to receive exhaust gas from the inlet; the turbomachine arrangement further comprising: a fluid storage device; a fluid conduit linking the fluid storage device to the turbine inlet; and a flow control device configured to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid conduit and turbine inlet.
2. 2. A turbomachine arrangement according to claim 1, further comprising a control arrangement, the control arrangement including a controller configured to control an actuator, the actuator being configured to actuate the flow control device to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid conduit and turbine inlet.
3. 3. A turbomachine arrangement according to either claim 1 of claim 2, further comprising a uni-directional valve arrangement configured to allow fluid to pass from the fluid storage device and/or fluid conduit to the turbine inlet, and configured to substantially prevent exhaust gas from passing from the turbine inlet to the fluid storage device and/or fluid conduit.
4. 4. A turbomachine arrangement according to claim 3, wherein the uni-directional valve arrangement is located and configured so as to allow fluid to pass from the flow control device to the turbine inlet, and located and configured to substantially prevent exhaust gas from passing from the turbine inlet to the flow control device.
5. 5. A turbomachine arrangement according to any proceeding claim, wherein the turbine forms part of a turbocharger, the turbocharger additionally comprising: a compressor including a compressor housing, the compressor housing defining a compressor outlet for supplying boost gas to an engine intake, a compressor inlet, and a compressor chamber between the compressor inlet and the compressor outlet; and a compressor wheel located within the compressor chamber and arranged to co-rotate with said turbine wheel about said axis.
6. 6. A turbomachine arrangement according to claim 5, further comprising a second fluid conduit linking the compressor outlet to the fluid storage device.
7. 7. A turbomachine arrangement according to claim 6, further comprising a second uni-directional valve arrangement configured to allow boost exhaust gas to pass from the compressor outlet and/or second fluid conduit to the fluid storage device, and configured to substantially prevent gas from passing from the fluid storage device to at least one of the compressor outlet, the engine intake and the second fluid conduit.
8. 8. A turbomachine arrangement according to claim 2 or any of claims 3 to 7 when dependent on claim 2, wherein the controller is configured to provide a control signal to the actuator in order to control the actuator; and the controller further being configured such that the control signal is a function of at least one of the group consisting of: speed of a vehicle of which the turbomachine arrangement forms part, engine speed, pressure at turbine inlet, pressure at the compressor outlet, pressure at the engine intake manifold, state of a throttle control for the engine, rate of change of state of said throttle control, rotary speed of camshaft of the engine, rotary position of camshaft of the engine, rotary speed of crankshaft of the engine, and rotary position of crankshaft of the engine.
9. 9. A turbomachine arrangement according to any preceding claim, wherein the controller is configured to provide a control signal to the actuator in order to control the actuator; and wherein the controller is configured such that the control signal is co-ordinated with an exhaust gas emission pattern of the engine, whereby the actuator actuates the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel in a substantially pulsed fashion, the pulses of fluid flowing from the fluid storage device to the turbine wheel being such that they arrive at the turbine wheel at substantially the same time as pulses of exhaust gas produced by the engine, and wherein the pulses of exhaust gas are caused by cylinders of the engine producing exhaust gas at different times.
10. 10. A method of operating an engine including a turbomachine arrangement, the turbomachine arrangement including: a turbine comprising: a housing, the housing defining a turbine inlet, a turbine outlet and a turbine chamber between the turbine inlet and the turbine outlet; and a turbine wheel located within the turbine chamber; the turbomachine arrangement further comprising: a fluid storage device; a fluid conduit linking the fluid storage device to the turbine inlet; and a flow control device; and a control arrangement including a controller and an actuator linked to the flow control device; the method comprising: the engine providing exhaust gas to the turbine wheel via the turbine inlet to thereby rotate the turbine wheel about an axis; and the controller controlling the actuator to actuate the flow control device to selectively enable fluid to flow from the fluid storage device to the turbine wheel via the fluid conduit and turbine inlet.
11. 11. A method according to claim 10, wherein the turbine of the turbomachine arrangement forms part of a turbocharger, the turbocharger additionally comprising: a compressor including a compressor housing, the compressor housing defining a compressor outlet, a compressor inlet, and a compressor chamber between the compressor inlet and the compressor outlet; and a compressor wheel located within the compressor chamber; the method further comprising: the turbine wheel driving the compressor wheel such that it co-rotates with said turbine wheel about said axis; and the rotation of the compressor wheel causing the compressor to supply boost gas to an engine intake.
12. 12. A method according to claim 11, wherein the turbomachine arrangement further comprises a second fluid conduit linking the compressor outlet to the fluid storage device; and the method further comprising supplying boost gas to the fluid storage device via the second fluid conduit.
13. 13. A method according to any of claims 10 to 12, the method further comprising the controller providing a control signal to the actuator in order to control the actuator; and wherein the control signal is a function of at least one of the group consisting of: speed of a vehicle of which the turbomachine arrangement forms part, engine speed.pressure at turbine inlet, pressure at the compressor outlet, pressure at the engine intake manifold, state of a throttle control for the engine, rate of change of state of said throttle control, rotary speed of camshaft of the engine, rotary position of camshaft of the engine, rotary speed of crankshaft of the engine, and rotary position of crankshaft of the engine.
14. 14. A turbomachine according to any of claims 10 to 13, the method further comprising the controller providing a control signal to the actuator in order to control the actuator; and the controller coordinating the control signal with an exhaust gas emission pattern of the engine, whereby the actuator actuates the flow control device to enable fluid to flow from the fluid storage device to the turbine wheel in a substantially pulsed fashion, the pulses of fluid flowing from the fluid storage device to the turbine wheel being such that they arrive at the turbine wheel at substantially the same time as pulses of exhaust gas produced by the engine, and wherein the pulses of exhaust gas are caused by cylinders of the engine producing exhaust gas at different times.