Abstract
In an effort to increase the reliability and net power and efficiency benefit of the axial- and mixed-flow turbocharger turbine, there is provided, a tapered, axially translatable (“sliding nozzle”) flow restrictor member to provide appropriate inlet exhaust gas flow characteristics for the operation of an axial or mixed flow turbine. The invention produces change of turbine flow with acceptable resolution at a lower cost than that for a conventional pivoting vane, variable geometry axial turbocharger turbine or at a similar cost but higher efficiency than a conventional sliding nozzle, variable geometry mixed, flow turbocharger turbine.
Claims
1-13. (canceled)
14. A turbocharger comprising a turbine for driving a compressor wherein the turbine has a shaft of rotation and wherein the turbine is of either axial or mixed flow geometry, an inlet for fluid entering the turbine, an outlet for fluid exiting the turbine, and a flow restrictor positioned in the inlet for restricting the flow of fluid entering the turbine, the flow restrictor being moveable between a first less restricting position and a second more restricting position, wherein the flow restrictor is shaped so as to guide fluid towards the turbine and to avoid fluid being trapped in the inlet.
15. The turbocharger of claim 14, wherein the flow restrictor is shaped so as to conform to the shape of the inlet, so as to reduce gaps between the flow restrictor and the inlet.
16. The turbocharger of claim 14, wherein the flow restrictor has a tapered section, which acts as a flow guide for fluid entering the turbine.
17. The turbocharger of claim 16, wherein the tapered section has a degree of inward curvature.
18. The turbocharger of claim 16, wherein the tapered section has a degree of outward curvature.
19. The turbocharger of claim 16, wherein the tapered section has zero curvature.
20. The turbocharger of claim 14, wherein an axis of movement of the flow restrictor from the first to the second position is parallel to an axis defined by the shaft of the turbine.
21. The turbocharger of claim 14, additionally comprising an actuator for varying position of the flow restrictor, a sensor for sensing inlet pressure, and a controller to control the actuator to provide a flow restrictor position dependent on the inlet pressure sensed by the sensor.
22. The turbocharger of claim 21, further comprising a flow restrictor position sensor to enable closed loop position control.
23. A flow control device for a turbocharger having a turbine of either axial or mixed flow geometry, the device comprising an inlet for fluid entering the turbine, a flow restrictor positioned in the inlet for restricting the flow of fluid entering the turbine, the flow restrictor being moveable between a first less restricting position and a second more restricting position, wherein the flow restrictor is shaped so as to guide fluid towards the turbine and to avoid fluid being trapped in the inlet.
24. The flow control device of claim 23 wherein the flow restrictor is shaped so as to conform to the shape of the inlet, so as to reduce gaps between the flow restrictor and the inlet.
25. The flow control device of claim 23, wherein the flow restrictor has a tapered section, which acts as a flow guide for fluid entering the turbine.
26. The flow control device of claim 23, wherein the tapered section has a degree of inward curvature.
27. An internal combustion engine including a turbocharger, wherein the turbocharger comprises: a turbine for driving a compressor wherein the turbine has a shaft of rotation and wherein the turbine is of either axial or mixed flow geometry, an inlet for fluid entering the turbine, an outlet for fluid exiting the turbine, and a flow restrictor positioned in the inlet for restricting the flow of fluid entering the turbine, the flow restrictor being moveable between a first less restricting position and a second more restricting position, wherein the flow restrictor is shaped so as to guide fluid towards the turbine and to avoid fluid being trapped in the inlet.
28. A vehicle including an internal combustion engine which includes a turbocharger, wherein the turbocharger comprises: a turbine for driving a compressor wherein the turbine has a shaft of rotation and wherein the turbine is of either axial or mixed flow geometry, an inlet for fluid entering the turbine, an outlet for fluid exiting the turbine, and a flow restrictor positioned in the inlet for restricting the flow of fluid entering the turbine, the flow restrictor being moveable between a first less restricting position and a second more restricting position, wherein the flow restrictor is shaped so as to guide fluid towards the turbine and to avoid fluid being trapped in the inlet.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Embodiments of the invention will be described below, by way of example only, with reference to the accompanying drawings, in which:
[0029] FIG. 1 is a system overview of a prior art turbocharged internal combustion engine.
[0030] FIG. 2 is a sectional view of a prior art, conventional radial-inflow turbocharger turbine with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional sliding nozzle flow restrictor member. The principle of variable geometry is provided in this drawing for closed nozzle position (FIG. 2A) and open nozzle position (FIG. 2B).
[0031] FIG. 3 illustrates the operation of a prior art, conventional radial-inflow turbocharger turbine with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional pivoting vane flow restrictor array.
[0032] FIG. 4 illustrates a sectional view of a prior art, mixed flow turbocharger turbine (FIG. 4A) and a sectional view of an axial turbocharger turbine (FIG. 4B) with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional sliding nozzle flow restrictor member in both cases with the interspace gap between the exit of the flow restrictor and the inlet to the turbine rotor highlighted.
[0033] FIG. 5 is a sectional view of the present invention disclosure whereby a tapered sliding nozzle low restrictor is provided such that its contours follow the internal geometry of the turbine inlet casing. The invention disclosure is applicable to both mixed flow turbines (FIG. 5A) as well as axial turbines (FIG. 5B). This tapering of a sliding nozzle flow restrictor offers minimisation of the interspace gap especially at the higher turbine inlet area restrictions.
[0034] FIG. 6 is a sectional view of the mixed flow turbine sliding nozzle flow restrictor illustrating in FIG. 6A straight tapering, in FIG. 6B inwardly-curved contouring and in FIG. 6C, outwardly-curved contouring. The same options apply to the axial turbine flow restrictor of FIG. 5B.
[0035] FIG. 7 is a sectional view of the axial flow turbine sliding nozzle flow restrictor from FIG. 5B, illustrating the option of using a shorter tapered section, 213, for the flow restrictor (compared to the longer tapered flow restrictor, 199, in FIG. 5B) in order to enable a higher degree of restriction when comparing the resultant available passage area, 215, for the exhaust flow from which to enter the axial turbine rotor, 201, compared to the available area, 207, in FIG. 5B.
[0036] FIG. 8A is a sectional view of the axial flow turbine sliding nozzle flow restrictor from FIG. 5B, illustrating the option (in FIG. 8B) of using a lower mass (and therefore) inertia hub design, 203. The mass that can be potentially removed is highlight in light grey in FIG. 8B (217).
DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS
[0037] The following embodiments relate generally to an exhaust gas driven turbocharger and, more particularly, to a variable-geometry turbine turbocharger. In these embodiments, the turbine contains an adjustable inlet flow control mechanism comprising of a single axially translatable flow restrictor member. This is to increase overall internal combustion engine efficiency as the turbocharger is connected to, driven by and boosts an internal combustion engine. Embodiments differ from existing variable geometry arrangements in the following ways: the flow restrictor member follows the contours of the rotatable hub on which the axial turbine blades are mounted. By having this specific profile the axially translatable flow restrictor can effectively provide conversion of the flow from the radial to the axial or mixed flow direction while providing flow restriction throughout. By comparison, axially translatable members described in other inventions disclosures (e.g. U.S. Pat. No. 4,776,168) do not provide hub contour geometry and therefore create an interspace gap between flow restrictor and turbine rotor (either axial or mixed flow) which leads to flow losses as described in the Background to this invention disclosure. The contoured flow restrictor also allows the retention of the traditional advantages of axially translatable flow restrictor members compared to pivoting vane variable geometry systems described earlier (e.g. U.S. Pat. No. 7,571,607) such as simpler, single piece construction of lower cost and higher reliability while preserving the performance of more conventional (i.e., radial), axially translatable flow restrictor systems.
[0038] With reference to FIG. 1, a typical turbocharger 101 having a radial turbine includes a turbocharger housing and a rotor configured to rotate within the turbocharger housing along an axis of rotor rotation 103.The turbocharger housing includes a turbine housing 105, a compressor housing 107, and a bearing housing 109 (i.e., a centre housing that contains the bearings) that connects the turbine housing to the compressor housing. The rotor includes a turbine wheel 111 located substantially within the turbine housing, a compressor wheel 113 located substantially within the compressor housing, and a shaft 115 extending along the axis of rotor rotation, through the bearing housing, to connect the turbine wheel to the compressor wheel.
[0039] The turbine housing 105 and turbine wheel 111 form a turbine configured to circumferentially receive a high pressure and high temperature exhaust gas stream 117 from an engine, 119. The turbine rotor is driven in rotation around the axis of rotor rotation 103 by the high-pressure and high-temperature exhaust gas stream, which becomes a lower-pressure and lower-temperature exhaust gas stream 121 and is axially released into an exhaust system (not shown).
[0040] The compressor housing 107 and compressor wheel 113 form a compressor stage. The compressor wheel, being driven in rotation by the exhaust-gas driven turbine wheel 111, is configured to compress axially received input air (e.g., ambient air 123, or already-pressurised air from a previous-stage in a multi-stage compressor) into a pressurised air stream 125 that is ejected circumferentially from the compressor.
[0041] Optionally, the pressurized air stream may be channeled through a convectively cooled charge air cooler configured to dissipate heat from the pressurized air stream, increasing its density. The pressurized output air stream 125 is channeled into an internal combustion engine, 119, or alternatively, into a subsequent-stage, in-series compressor. The operation of the system is controlled by an ECU (engine control unit), 127, that connects to the remainder of the system via communication connections 129.
[0042] FIG. 2 provides a sectional view of a prior art, conventional radial-inflow turbocharger turbine with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional sliding nozzle flow restrictor member. The principle of variable geometry is provided in this drawing (FIGS. 2A and 2B). In FIG. 2A the engine cylinder or cylinders, 131, are undergoing an exhaust process whereby, the piston is moving from a low position inside the cylinder bore towards the Bottom Dead Centre (BDC) and back up towards the Top Dead Centre (TDC) during which time an exhaust valve or valves, 133, are open allowing exhaust gas to escape toward a turbocharger turbine, 135. At the inlet to the turbocharger turbine, 137, there is disposed an axially translatable, flow restrictor, variously referred to in practice as a sliding wall, sliding nozzle or slidevane. This is a cylindrical member, concentrically disposed around the circumference of the turbine rotor, 139. It can translate axially inside the turbine inlet passage, 137, and reduce the cross-sectional area available for the flow to pass through and reach the turbine. This has the effect of the accelerating the flow, which therefore, enters the turbine rotor, disposed immediately downstream of the flow restrictor member, 139, and cause a higher momentum flow to impact the rotor blades which in turn creates acceleration of the rotor to a higher rotational speed. This higher rotational speed is then transmitted to the turbocharger compressor, 113 in FIG. 1, which is then able to draw in and pressurise more air and thereby more boost and therefore more power to the engine compared to an un-restricted turbine inlet system in a turbocharger also known in practice as a fixed geometry turbocharger turbine. At low engine speeds and loads, the amount of exhaust gas produced is minimal, necessitating the maximum flow restriction practical in a variable geometry turbocharger turbine, 143, in FIG. 2A. It is this restriction that causes high momentum flow to impact the turbine rotor blades and therefore allows the turbocharger to accelerate in order to provide engine boost pressure. When the engine is operated at a condition where the engine speed and load provide significant to maximum exhaust mass flow, the flow restrictor, 139, is adjusted to allow a maximum turbine inlet passage area, 145, so that the momentum rise of the exhaust gas flow does not surpass the turbocharger rotational speed limit (FIG. 2B).
[0043] FIG. 3 illustrates the operation of a prior art, conventional radial-inflow turbocharger turbine with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional pivoting vane flow restrictor array. In FIG. 3A a section of the turbocharger turbine is provided in which exhaust gas flow, 159, is directed through an opening of the turbine inlet casing (volute), 147. The flow is directed towards an array of pivoting vanes, 151, which provide flow guidance according to the engine operating requirements towards a turbine rotor, 149. The array of pivoting vanes is radially disposed around the circumference of the turbine rotor, 149, and is individually pivotable as a result of rotational motion of a steering pivot, 153, connected through a pivoting pivot lever, 155, to a circular nozzle control ring, 157, on which all pivoting vanes are mounted. The nozzle control ring is rotated to effect pivoting motion of all pivoting vanes in unison. Rotation of the nozzle control ring can be effected by various means of actuation such as electro-pneumatic, electrohydraulic, servo-electric or electro-magnetic. When the engine is operated at high engine speeds and loads, there is provided a substantial amount of exhaust gas mass to the turbocharger turbine and therefore the flow is directed in a substantially radial direction such that the turbine rotor will not overspeed (FIG. 3B). When the engine is operated at low engine speeds and loads, there is provided a small amount of exhaust gas mass to the turbocharger turbine and in the event of a required transient operation from low-to-high engine speed and load the vanes have to guide the flow in a substantially tangential direction in order to impart momentum onto the turbine rotor blades. The rotation of the pivoting vane array, 151, 153, 155, 157, towards a more tangential direction in relation to the turbine rotor blade leading edges creates an additional flow passage restriction between consecutive vanes which allows the flow to accelerate (FIG. 3C). This accelerated flow is also then, as a result of the tangential direction of the flow cause the turbine rotor to accelerate faster than a conventional turbocharger turbine with fixed (non-pivoting) vanes or without any vanes at all.
[0044] FIG. 4 illustrates a sectional view of a prior art, mixed flow turbocharger turbine (FIG. 4A) and a sectional view of an axial turbocharger turbine (FIG. 4B) with adjustable means of the exhaust gas passage at the turbine inlet being provided by a conventional sliding nozzle flow restrictor member in both cases (161 and 189, respectively) with the detrimental interspace gap between the exit of the flow restrictor and the inlet to the turbine rotor created as a results of the two respective geometries (193 in both FIG. 4A and FIG. 4B) being highlighted.
[0045] FIG. 4A is a prior art embodiment found in WO2006/061588 A1. In this embodiment, a conventional sliding nozzle flow restrictor member, 161, is incorporated into a turbine inlet casing (volute) structure formed by members 163 on the outside and 165 on the inside of the volute exit member is used to attach member 167 onto 163. A yoke system, 171, is mounted on the flow restrictor, 161, and the yoke is driven by an external actuator (not shown) and transmits its rotational motion onto the flow restrictor, 163, via a pivot point, 169, which translates rotational motion into linear. The location of the flow restrictor is immediately upstream of the turbine rotor, 171. The rotor blades are cast into a rotating hub, 173, and protrude radially outwards from it. The rotor is of mixed flow geometry so the leading edge of the rotor blade does not align itself to the axis of shaft rotation of the turbocharger, 175. This creates a space between the exit of the flow restrictor, 161 and the inlet to the turbine rotor blade leading edge (171) and is highlighted as the shaded area 193 in FIG. 4.A.
[0046] FIG. 4B is a prior art embodiment similar in effect to the one found in U.S. Pat. No. 4,776,168. In this embodiment, a conventional sliding nozzle flow restrictor member, 189, is incorporated into a turbine inlet casing (volute) structure. The flow restrictor member, 189, may be actuated by a similar mechanism and actuator as in FIG. 4A. The location of the flow restrictor is upstream of the turbine rotor, 179. The rotor blades are cast into a rotating hub, 183, and protrude radially outwards from it. The rotor is of axial flow geometry this rotor receives exhaust gas axially (in relation to the axis of shaft rotation of the turbocharger, 181) from the volute inlet, 187, and this exhaust gas flow exits axially as well. Because of the fact that the volute is accepts exhaust gas flow radially and guides to an axial direction prior to entry into the axial turbine's rotor blades, 179, and the unique rotating (about axis, 181 on shaft, 185) hub geometry, 183, which allows this radial-to-axial flow conversion a space is created between the exit of the flow restrictor, 189, when it is protruding into the flow to allow flow restriction, 191, and therefore energy recovery and the inlet to the turbine rotor blade leading edge, 179 which is detrimental to the performance of the rotor due to a large region of flow deceleration forming before the flow can reach the turbine rotor blades, 179. This interspace is highlighted as the shaded area 193 in FIG. 4B.
[0047] FIG. 5 illustrates a sectional view of the present invention disclosure whereby a tapered sliding nozzle flow restrictor, 197, is provided such that its contours follow the internal geometry of the turbine inlet casing. The invention disclosure is applicable to both mixed flow turbines (FIG. 5A) as well as axial turbines (FIG. 5B). This tapering of a sliding nozzle flow restrictor offers minimisation of the interspace gap, 207, especially at the higher turbine inlet area restrictions.
[0048] Specifically, in FIG. 5A, a mixed flow turbine is illustrated, where exhaust flow is guided from a turbine inlet casing, 195, through a sliding nozzle flow restrictor, 197, into a turbine rotor, 201 and exits into the atmosphere through piping attached at the exit to the turbine (not shown). The tapered, axially translatable flow restrictor, 197, is positioned radially and outside of the turbine rotor hub, 203. The turbine rotor blades, 201, are attached to a rotating hub, 203, and are projected radially outwards from it. The hub, 203, and turbine rotor blades are rotated around a shaft axis of rotation, 205. When the engine operating conditions are such that the mass of exhaust gas flow is relatively small, then the flow restrictor is translated axially into the turbine rotor upstream passage known as the throat section, up to a maximum level of restriction, 199. Due to the degree of tapering in the nozzle, the detrimental-to-turbine-performance interspace gap, 199, between flow restrictor and turbine rotor blade leading edge is minimised when compared to the equivalent interspace gap in FIG. 4A.
[0049] In FIG. 5B, an axial flow turbine is illustrated, where exhaust flow is guided from a turbine inlet casing, 195, through a sliding nozzle flow restrictor, 197, into a turbine rotor, 201 and exits into the atmosphere through piping attached at the exit to the turbine (not shown). The tapered, axially translatable flow restrictor, 197, is positioned radially and outside of the turbine rotor hub, 203. The turbine rotor blades, 201, are attached to a rotating hub, 203, and are projected radially outwards from it. The hub, 203, and turbine rotor blades are rotated around a shaft axis of rotation, 205. When the engine operating conditions are such that the mass of exhaust gas flow is relatively small, then the flow restrictor is translated axially into the turbine rotor upstream passage known as the throat section, up to a maximum level of restriction, 199. Due to the degree of tapering in the nozzle, the detrimental-to-turbine-performance interspace gap, 199, between flow restrictor and turbine rotor blade leading edge is minimised when compared to the equivalent interspace gap in FIG. 4B.
[0050] FIG. 6 illustrates a sectional view of the mixed flow turbine sliding nozzle flow restrictor illustrating in FIG. 6A straight tapering, in FIG. 6B inwardly-curved contouring and in FIG. 6C, outwardly-curved contouring. These are options for the design of the flow restrictor depending on the degree to which the contouring of the internal flow passage of the turbine inlet casing, 195 in FIG. 5, is required to be followed. The same options apply to the design of axial turbine flow restrictor of FIG. 5B.
[0051] FIG. 7 illustrates a sectional view of the axial flow turbine sliding nozzle flow restrictor from FIG. 5B, illustrating the option of using a shorter tapered section, 213, for the flow restrictor (compared to the longer tapered flow restrictor, 199, in FIG. 5B) in order to enable a higher degree of restriction when comparing the resultant available passage area, 215, for the exhaust flow from which to enter the axial turbine rotor, 201, compared to the available area, 207, in FIG. 5B. It is understood that any length may be chosen according to the turbocharger designer's perception of the turbocharger turbine operating requirement and the same applies to the design of the level of direction of curvature of the tapered section for either mixed or axial turbine flow restrictor in FIG. 6.
[0052] FIG. 8A illustrates a sectional view of the axial flow turbine sliding nozzle flow restrictor of FIG. 5B, illustrating the option (in FIG. 8B) of using a lower mass (and therefore) inertia hub design, 217. Since the tapered nozzle section already covers in part the hub cross section, there is no need for a hub cross sectional area indicated in light grey in FIG. 8B and it can thus be removed, thus reducing the mass of the rotatable hub substantially. This inertia is therefore reduced by (1) the reduction in mass and by the fact that the removed mass is removed from the outer radius of the hub (‘217’ in FIG. 8) thus reducing the polar moment of inertia even further compared to the case of an equivalent mass being removed from a lower radius (i.e., closer to the axis of rotation of the shaft, ‘205’ in FIG. 8B).
[0053] All optional and preferred features and modifications of the described embodiments and dependent claims are usable in all aspects of the invention taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.
[0054] The disclosures in UK patent application number 1420559.5 from which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.
