AND TURBINE WITH BYPASS ARRANGEMENT

BACKGROUND AND SUMMARY

The present application relates, according to an aspect thereof, generally to methods and apparatus for adjusting engine exhaust gas temperature in an engine including a turbine in the exhaust stream.

Modern diese! engines typicall include exhaust aftertreatment systems (EATS) with one or more components such as diesei particulate filters (DPFs), diesei oxidation cataiysts (DOCs), and selectivt' catalytic reduction cataiysts (SCRs). Most of the EATS components are intended to operate within particular tempera ure ranges. During operation, at start-up or at low loads, it ma be difficult to reach or maintain the temperatures necessary to activate catalysts on

equipment such as DPFs, DOCs, and SCRs. Additionally, it is occasionally necessary to increase exhaust gas temperatures to well above normal operating temperatures to regenerate components such as DPFs.

One way of raising exhaust gas temperature has ^' been to use a variable geometry turbocharger (VGT) with a turbine downstream of the engine. The VGT can be adjusted to reduce the efficiency of the turbocharger, which can result in an increase in engine exhaust temperature. VGTs, however, tend to be expensive and involve numerous moving parts that can be subject to failure.

Another technique for raising exhaust gas temperature in volves the use of a disch arge recirculation valve that decreases compressor efficiency without increasing pre-turbine pressures. Still further techniques include use of intake and exhaust throttles, tailpipe hydrocarbon

injection, and charge air cooler (CAC) bypass valves.

it is desirable to provide a simple, inexpensive apparatus and method for adjusting exhaust gas temperature.

According to an aspect of the present invention, a turbocharger comprises a turbine comprising a scroll passage comprising at least first and second, portions, a gas outlet extending axialiy from the scroll passage, a turbine wheel comprising one or more blades disposed in the gas outlet, and means for establishing a bypass flow between the first and second portions of the scroll passage.

According to another aspect of the present invention, a turbocharger comprises a turbine comprising a scroll passage, a gas outlet extending axialiy from the scroll passage, a turbine wheel comprising one or more blades disposed in the gas outlet, a .nozzle ring arranged between the scroll passage and the gas outlet, the nozzle ring comprising a plurality of vanes adapted to direct a flow of gas from the scroll passage against the one or more blades of the turbine wheel in the gas outlet, and means for moving the nozzle ring relative to the scroll passage to alter the gas flow through the nozzle ring from the scroll passage toward the one or more blades of the turbine wheel.

According to another aspect of the present invention, a method, for adj usting exhaust gas temperature in an engine comprising a turbine arranged to receive engine exhaust comprises causing engine exhaust gas to flo w through a scroll passage of the turbine toward a gas outlet of the turbine, the scroll passage comprising at least first and second portions, and establishing a bypass flow between the first and second portions of the scroll passage. According to yet another aspect of the present invention, a method for adjusting exhaust gas temperature in an engine comprising a turbine arranged to receive engine exhaust comprises causing engine exhaust gas to flow through a scroll passage of the turbine toward a gas outlet of the turbine, the scroll passage comprising at least first and second portions, directing the exhaust gas again st one or more blades of a turbine wheel in the gas outlet of the turbine with a nozzle ring comprising a plurality of vanes arranged at a first orientation relative to the scroll passage, and moving the nozzle ring from a first position relative to the scroll passage in which the plural ity of vanes on the nozzle ring direct gas against the one or more blades of the turbine wheel to a second position relative to the scroll passage in which gas flow from the scroll passage through the plurality of vanes into the gas outlet is altered relative to gas flow in the first position.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understood by reading the following detailed description in conjunction with the drawings in which like numerals indicate similar elements and in which:

FIG, 1 is a schematic- iew of an engine with a turbocharger and turbine;

FIG. 2A is a partially cross-sectional view of a portion of a turbine according to an aspect of the present .in vention;

FIG. 2B is a partially cross-sectional view of the portion of the turbine of FIG. 2A showing a sealing vane moved relative to a nozzle ring of the turbine;

FIG. 2C is a partially cross-sectional view of a portion, of a turbine according to another aspect of the present invention showing a nozzle ring moved relati ve to a scroll passage; FIG, 3 A is a partially cross-sectional view of a portion of a turbine according to an aspect of the present invention;

FIG. 3B is a partially cross-sectional view of the portion of the turbine of FIG. 3 A

showing a sealing vane moved relative to a nozzle ring of the turbine; and

FIG. 3C is a partially cross-sectional view of a portion of a turbine according to another aspect of the present invention showing a nozzle ring moved relative to a. scroll passage

DETAILED DESCRIPTION

Gas flow through scroil passages in a turbocharger turbine connected to the exhaust of a multi-cylinder engine is not ordinarily at a constant pressure over the length of the scroll passage. In single scroll turbines, pressure differences will be present betwee different locations of the scroll due to factors such as opening and closing of piston valves and pressure losses as exhaust flows around the scroil. in addition, in twin scroll turbines, pressure differences will be present between the scrolls, also usually due factors such as to opening and closing of piston val ves, some of which pistons exhaust to one scroll and some to the other, and due to pressure losses as exhaust flows around the scrolls, one of which is ordinarily longer than the other.

A turbocharger 21 according to an aspect of the present invention is shown in FIG. I and includes a turbine 23. The turbocharger 21. is preferably a fixed geometry turbocharger. An embodiment of the turbine 23 comprises a scroll passage 25 such, as is seen in FIG. 2 A

composing at least first and second portions. The first and second portions of die scroll passage 25 may take various forms. The turbine 23 comprises a gas outlet 27 extending axially from the scroll passage 25 and a turbine wheel 29 comprising one or more blades 31 disposed in the gas outlet. One or more of several suitable structures or means can be provided for establishing a bypass flow between the first and second portions of the scroll passage 25 such that some or all of the gas flowing through the scroll, passage toward the gas outlet 23 i permitted to How to one or the other of the first and second portions before it reaches the gas outlet The structure for establishing the bypass flo can alter or disrupt gas flow and/or lower pressure of the gas in the scroll passage when the bypass flow is established, so as to tend to reduce turbine efficiency. Reduced turbine efficiency can, in turn, result in increased temperature of gas exiting the engine 33 to which the turbocharger 21 is attached. The increased engine exhaust temperature can be used to activate catalysis in exhaust aftertreatment system equipment such as a diesel particniate filter (DPF), a diesel oxidation catalyst (DOC), and/or a selective catalytic reduction catalyst

(SCR). It can also facilitate regeneration of the DPF by cr eating or helping to create sufficient l hig temperatures for 02 based regeneration or for N02 based regeneration.

FIG. 2A shows one possible structure for establishing the bypass flow that can be used by itself or in conjunction with the structures shown in FIGS. 28 and/or 2C. Specifically, a conduit 55 can be connected between a first portion 43 of the scroll passage 25 near a beginning of the scroll passage, i.e., an inlet region, from a second portion 45 of the scroll passage near the end of the scroll passage, i.e., an end region, and a controllable valve 57 can be provided in the conduit that opens to establish the bypass flow. The valve 57 can be controlled by a conventional ECU or other computing device 59, or by any other suitable means, including manual operation.

One of the possible structures for establishing the bypass flow is seen in FIGS. 2B and comprises a nozzle ring 35 arranged between the scroll passage 25 and the gas outlet 27. The nozzle ring 35 comprises a plurality of vanes 37 adapted to direct flow of gas from the scroll passage 25 against the one or more blades 31 of the turbine wheel 29 in the gas outlet 27. The nozzle ring 35 shown in FIGS. 2A and 2B comprises at least one sealing vane 39 that extends to an inner wall or tongue 1 of the gas outlet 27 and seals the first portion 43 of the sero!! passage 25 from the second portion 45 of the scroll passage. n the embodiments shown i F3GS. 2A-2C, the fust and second portions 43 and 45 of the scroll passage 25 take the form of different portions of the same scroll passage. One or more struc tures or means is provided for moving the sealing vane 3 relative to the scroll passage 25 to establish the bypass flow between the first and second -portions 43 and 45 of the scroll passage. The sealing vane 39 is moved relative to the scroll passage 25 by moving the sealing vane relati ve to stationary nozzle ring 35. As seen in FIG. 2B, this opens a bypass or passage 47 between a first and second portions 43 and 45 of the scroll passage 25. The ordinary flow pattern seen in FIG. 2A, usually a flow with minimal turbulence, throush the scroll passage 25, the nozzle r.in.¾ 35. and aaainsi the turbine blades 31 is disrupted by the opening of the bypass 47 as higher pressure flow from the first portion 43 of the scroll passage flows into the lowe pressure region at the second portion 45 of the scroll passage. Consequently, turbine efficiency decreases.

The sealing vane 39 can be moved in any suitable manner, such as by being mounted on a pivotahie rod 49 mounted in a wall of the turbine housing and is turned through a limited angle by a device 51 (shown schematically in FIG. 1 ) such as a solenoid, motor, or other suitable means. Ordinarily, the rod 49 will extend through a wall of the turbine housing and the rod and seal ing vane 39 wi ll be turned by a devi ce 5.1 mounted outside of the turbine, al though numerous arrangements can be contemplated for driving the rod and sealing vane, and including devices that would be partially or completely disposed inside the turbine housing, not necessarily from outside of the turbine. Another one of the possible stractures for establishing the bypass flow is seen in the turbine 123 shown in FIG. 2C and comprises a nozzle ring 135 arranged between the scroll passage 125 and the gas outlet 127. The nozzle ring 135 comprises a plurality of vanes 137 adapted to direct a flow of gas from the scroll passage 125 against the one or more blades 1 1 of the turbine wheel 12 in the gas outlet 127. As with the nozzle ring 35 shown in FIGS. 2A and 2B, the nozzle ring 135 shown hi FIG. 2C comprise at least one sealing vane 139 that extends to an inner wall or tongue- .1 1 of the gas outlet 127 and seal a first portion 1 3 of the scroll, passage 125 near a beginning of the scroll passage from a second portion 145 of the scroll, passage near the end of the scroll passage. One or more structures or means is provided for moving the nozzle ring 135 relative to the scroll passage 125 to establish the bypass flow between the first and second portions 143 and 145 of the scroll passage. As seen, in FIG. 2€, this opens a bypass or passage 147 between a first and second portions 143 and 1 5 of the scroll passage 125, The ordinary flow pattern through the scroll passage 125, the nozzle ring 135, and the gas outlet 127 for the turbine 123 when the nozzle ring is not moved to open the bypass 147 is substantially the same as the ordinary flow pattern for the turbine 23 seen in FIG. 2 A. This flow, usually a flow with minimal turbulence, through the scroll passage 125, the nozzle ring 135, and against the turbine blades 131 is disrupted by the opening of the bypass 147 as higher pressure flow from the first portion 143 of the scroll passage flows in to the lower pressure region at the second portion 145 of the scroll passage. Consequently, turbine efficiency decreases. The nozzle ring 135 can be moved in any suitable manner, such as by providing an outer geared surface 149 (shown in phantom) on or connected to the nozzle ring that meshes with a driven gear 151 (shown in phantom in FIG. 2C) that is disposed in the turbine housing or at least partiall extends through a wall of the turbine housing and is driven through a limited angle by a motor 153 (shown in phantom), or other suitable means, that may be disposed outside, inside, or partially inside and partially outside the turbine housing. An external linear actuator that can reciprocate a shaft or linkage component that extends through an opening in the turbine housing and move a linkage that converts linear motion of the shaft into rotational motion of the ring (or of a vane) is presently believed to be particularly useful because only a .single seal where they shaft or linkage extends through the turbine housing is needed. It may also be possible to move the ring (or v ane) b means that do not require a mechanical connection extending through the turbine housing, such as by providing permanent magnets on the ring and moving the ring via a magnetic field around the turbine housing.

If the entire nozzle ring 135 is moved as seen in FIG, 2C, the plurality of vanes 137 and 139 on the nozzle ring 135 are also moved. If the van.es 137 and 139 are oriented to achieve maximum turbine efficiency when oriented as shown in FIG. 2A _> turbine efficiency can be decreased by turning, the nozzle ring 135 relative to the scroll passage 125 through a small angle. Ordinarily, the nozzle ring 135 rotates about an axis of the turbine wheel 129 through an arc of no more than an arc between ou termost peripheral dps of any two adjacent vanes 1.37 and 139 on the nozzle ring. For example, if the nozzle ring 135 has 18 vanes 137 and 139 spaced every 20° around the circular nozzle ring, the nozzle ring might be moved as much as 20* but, more typically will be moved through an angle less than 20°, such as an angle between l ^c' and 19°, more typically between.5° and 15°. and still more typically, about 10°. By such an angular movement, gas that had been deflected by the vanes 137 and 139 toward the one or more blades 13 i of the turbine wheel 129 at one angle as seen in FIG. 2A (illustrated by arrows extending across the nozzle ring 35) will be deflected i a somewhat different manner (illustrated by arrows extending across the nozzle ring 135 in FIG. 2C). While not wishing to be bound by theory, the movement of the nozzle ring 135 from a position i which the turbine is at maximum efficiency through a limited angle to a second position can generate more turbulence in the turbine 123 and decrease its efficiency. Altering gas flow from the scroll passage 125 through the vanes 137 and 139 into the aas outlet 127 can result in Sower turbine efficiency, as can introduction of the eas into the gas outlet 127 against the turbine blades 131 at a sub-optimal angle,

FIG. 3 A shows an embodiment of a turbine 223 that can be used in the iurbocharger 21 shown in FIG. .1 instead of the turbine 23. The turbine 223 comprises a twin scrol l passage 225 comprising a first scroll passage 225' and a second scroll passage 225" that, respectively, correspond to first and second portions 243 and 245 of the scroll passage. The turbine 223 comprises a gas outlet 227 extending axia!ly from the first and second scroll passages 225' and 225" and a turbine wheel. 229 comprising one or more blades 23 1 disposed in the gas outlet.

As with the turbine 23 with the single scroll passage shown in FIGS.. 2A-2C, one or more of several suitable structures or means can be provided for establishing a bypass flow between the first and second portions of the scroll passages 225 ^* and 225" such that some or all of the gas flowing through the scroll passages toward the gas outlet 223 is permitted to flow to one or the other of the first and second portions before it reaches the gas outlet. The structure for establishing the bypass flow can alter or disrupt gas flow and/or Sower pressure of the gas in the scroll passage when the bypass flow is established, so as to tend to reduce turbine efficiency. Reduced turbine efficiency can, in turn, result in. increased temperature of gas exiting the engine 33 to which the iurbocharger 21 is attached. The increased engine exhaust temperature can be used to activate catalysts in exhaust aftertreatjnent system equipment such as a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC), and/or a selective catalytic reduction catalyst (SCR). It can also facilitate regeneration of the DPF by creatiog or helping to create suffic iently high temperatures for 02 based regeneration or for N02 based regeneration.

FIG. 3 A shows one possible structure for establishing the bypass flow thai can be used by itself or in conjunction with the structures shown in FIGS, 3B and/or 3C. Specifically, a conduit 255 can be connected between a first portion 243 of the scroll passage 225 formed by the first scroll passage 225 ^! from a second, portion 245 of the scroll passage formed by the second scroll passage 225" and a controllable valve 257 can be provided in the conduit that opens io establish the bypass flow. The valve 25? can be controlled by a conventional ECU or other computing devic 259, or by any other suitable means, including manual operation.

One of the possible structures for establishing the bypass flow is seen in FIGS. 3B and comprises a nozzle ring 235 arranged between the scroll passage 225 (i.e. , the first and second scroll passages 225' and 225") and the gas outlet 227. The nozzle ring 235 comprises a plurality of vanes 23? adapted to direct a flow of gas from the scroll passage 225 against the one or more blades 2 1 of the turbine wheel 229 in the gas outlet. 227. The nozzle ring 235 shown in FIGS. 3A and 3B comprises at least two sealing vanes 239 that extend to inner wall portions or tongues 241 of the gas outlet 227 that separate the portion of the first scroll passage 225' that meets the gas outlet from the portion of second scrol l passage 225" and seals the first portion 243 of the scroll passage 225, i.e., the first scroll passage 225 ', from the second portion 245 of the scroll passage, i.e., the second scroll passage 225 ^' '. in the embodiments shown in FIGS. 3A-3C, the- first and second portions 243 and 245 of the scroll passage 225 take the form of different scroll passages. One or more structures or means is provided for moving the sealing vanes 239 relative to the scroll passage 225 to establish the bypass flow between the first and second portions 243 and 245 of the scroll passage. The sealing vanes 239 are moved relative to the scroll passage 225 by moving the sealing vane relative to a stationary nozzle ring 235. As seen in FIG, 3B, this opens bypasses or passages 247 between a first and second portions 243 and 245 of the scroll passage 225. The ordinary flow pattern seen in F G. 3 A, usually a flow with minima!

turbulence, through the scroll passage 225, the nozzle ring 235, and against the turbine blades 231 is disrupted by the opening of the bypasses 247 as higher pressure flow from the first portion 243 of the scroll passage flo ws in to the lower .pressure region at the second portion 245 of the scroll passage, or higher press re flow from the second portion flows into the lower pressure region in the first portion, depending upon whic portion has, at the particular time, higher or lower pressure. Consequently, turbine efficiency decreases.

The sealing vanes 239 can be moved in any suitable manner, such as by being mounted on a pivotable rod 249 mounted in a wall, of the turbine bousing and can be turned through a limited angle by a device such as a solenoid, motor, or other suitable means (motor 51 shown schematically in FIG. I). Ordinarily, the rod 249 will extend through a wall of the turbine housing and the rod and sealing vane 239 will be turned by a device 251 mounted outside of the turbine, although numerous arrangements can be contemplated for driving the rod and sealing vane, and tnciuding devices that would be disposed inside the turbine housing, not necessarily from outside of the turbine.

Another one of the possible structures for establishing the bypass flow is seen in FIG. 3C and comprises a nozzle ring 335 arranged between the scroll passage 325 and the gas outlet 327. The scroll passage 325 comprises a first scroll passage 325' and a second scroll passage 325" that, respectively, correspond to first and second portions 343 and 345 of the scroll passage. The nozzle ring 335 comprises a plurality of vanes 337 adapted to direct a flow of gas from the scroll passage 325 against the one or more blades 331 of the turbine wheel 329 in the gas outlet 327. The nozzle ring 335 shown in FIG. 3C, like the nozzle ring 235 shown in FIGS. 3A-3B, comprises at least two sealing vanes 339 that extend to inner wall portions or tongues 341 of the gas outlet 327 and seal the first portion 343 of the scroll passage 325, i.e., the first scroll passage 325 \ from a second portion 345 of the scroll passage, i.e., the second scroll passage 325". One or more structures or means is provided for moving the nozzle ring 335 relative to the scroli passage 325 to establish the bypass flow between the first and second portions 343 and 345 of the scroll passage. As seen in FIG. 3C, this opens a bypass or passage 347 between, a first and second portions 343 and 345 of the scroll passage 125. The ordinary flow pattern through the scroll passage 325, the nozzle ring 335, and the gas outlet 327 for the turbine 323 when the nozzle ring is not moved to open the bypass 347 is substantially the same as the ordinary flow pattern for the turbine 223 seen in. FIG. 3A. This flow, usually a How with minimal turbulence, through the scroll passage 325, the nozzle ring 335, and against the turbine blades 33.1 is disrupted by the opening of the bypass 347 as higher pressure flow from the first portion 343 of the scroll passage flows into the lower pressure region at the second portion 345 of the scroll passage, or higher pressure flow from the second portion flows into the lower pressure region in the first portion, depending upon which portion has, at the particular time, higher or low er pressure. Consequently, turbine efficiency decreases. The nozzle ring 335 can be moved in any suitable manner, such as by providing a outer geared surface 34 (shown in phantom) on or connected to the nozzle ring that meshes with a driven gear 35.1 (shown in phantom) thai is disposed in the turbine housing or at least partially ex tends through a wall of the turbine housing and is driven through a limited angle by a motor 353 (shown in phantom), or other suitable means, that may be disposed outside, inside, or partially inside and partially outside the turbine housing.. If the entire nozzle ring 335 is moved as seen in FIG. 3C _S the plurality of vanes 337 and 339 on the nozzle ring 335 are also moved. If the vanes 337 and 339 are oriented to achieve maximum turbine efficiency when oriented as shown in FIG. 3 A, turbine efficiency can be decreased by turning the nozzle ring 335 relative to the scroll passage 325 through a small angle. Ordinarily, the nozzle ring 335 rotates about an axis of the turbine wheel 329 through an arc of no more tha an arc between outermost peripheral tips of any two adjacent vanes 337 and 339 on the nozzle ring. For example, if the nozzle ring 335 has 18 vanes 337 and 339 spaced every 20° around the circular nozzle ring, the nozzle ring might be moved as much as 20° but, more typically will be moved through an angle less than 20°, such as an angle between 1° and 19°, more typically between 5 ^C ' and 15°, and still more typically, about 10°. By such an angular movement, gas that had been deflected by the vanes 337 and 3.39 toward the one or more blades 331 of the turbine wheel 329 at one an«Se as seen in FIG. 3A will be deflected in a somewhat different manner. While not wishing to be bound by theory, the movement of the nozzle ring 335 from a position in which the turbine is at maximum efficiency through a limited angle to a second position can generate more turbulence in the turbine 323 and decrease its efficiency. Altering gas flow from the scroll passage 325 through the vanes 337 and 339 into the gas outlet 327 can result in lower turbine efficiency, as can introduction of the gas into the gas outlet 327 against the turbine blades 331 at a sub-optimal angle.

A method according to an aspect of the present invention for adj sting exhaust gas temperature in an engine comprising a turbine arranged to receive engine exhaust is described with reference to the engine 33 shown in FIG. I . For purposes of illustration, the method shall be described in connection with a single scroll turbine 23 as shown in FIGS. 2A-2B, except where otherwise noted. It will be appreciated that the description of the method in connection with the single scroll turbine 23 is also generally applicable to the single scroll turbine 123 shown in FIG. 2C and the twin scroll turbines 223 and 323 shown in FIGS. 3A-3C, except where otherwise noted.

In the method, engine exhaust gas is caused to flow from the engine 33 (FIG. 1) through a scroll passage 25 of the turbine 23 toward a gas outlet.27 of the turbine. The scroll passage 25 comprises at least first and second portions 43 and 45. A bypass flow of the exhaust gas is caused to flo w through a bypass 47 betw een the first and second porti ons 43 and 45 of the scroll passage 25. By establishing the bypass 47 and bypass flow, efficiency of the turbine 23 will ordinarily be decreased relative to the condition when there is no bypass, and exhaust

temperature will ordinarily rise.

In the embodiment of FIGS. 2A-2B, as in the embodiment of FIG. 2( \ the first portion 43 of the scroll passage 25 is near a beginning of the scroll passage and the second portion 45 is near an end of the scroll passage, and the first and second portions are separated by a tongue 41. in the embodiments of FIGS. 3A-3C, first and second portions of the scroll passage are first and second scroll passages of a twin scroll passage that are separated by two tongues.

Referring to the embodiment of FIGS. 2A-2B for purposes of illustration, the exhaust gas is directed by a nozzle ring comprising a pluralit of vanes 37 and 39 arranged at a first orientation relative to the scroll passage against one or more blades 3 ! of the turbine wheel 29 in the gas outlet 27 of the turbine. The nozzle ring 35 comprises at least one sealing vane 39 that, during ordinary operation, is arranged so that the first portion 43 of the scroll passage 25 is sealed from the second portion 45 of the scroll passage.

The bypass 47 for establishing the bypass flow between the first and second portions 43 and 45 of the scroll passage 25 is opened by moving the sealing vane 39 relative to the scroll passage 25. in the embodiment of FIGS. 2A-2B (and in the embodiment of FIGS. 3A-3B), the sealing vane 39 is moved, reiative to the scroll passage 25 by moving the sealing vane relative to the nozzle ring 35.

in the embodiment of FIG. 2 C (and in the embodiment of FIG. 3C), the sealing vane 139 is moved reiative to the scroll passage 125 by moving the nozzle ring 135 relative to the scroii passage. Moving the nozzle ring 135 from a. first position, e.g., a position like the position shown in FIG. ^' 2 A (or 3 A.) to a second position, e.g., a position like the position shown in FIG. 2C (or 3C) relati ve to the scroll passage .125 alters flow of exhaust gas from the scroll passage to the gas outlet through the plurality of vanes 137 and 139. Altering gas flow in the turbine from a gas flow (illustrated by arrows extending across the nozzle ring 35) as shown in FIG, 2A, which shall be assume to achieve optimal turbine efficiency, to a gas flow (illustrated by arrows extending across the nozzle ring 135) as shown in FIG. 2C can also reduce turbine efficiency and, thus, increase exhaust temperature.

In any of the illustrated embodiments, a bypass flow can be achieved by establishing a bypass via a conduit 55 connected to the first and second portions 43 and 45 of the scroii passage, such as by opening a valve 57 in the conduit. In addition, the embodiment of FIGS. 2A- 2B including a nozzle ring 35 with a movable sealing vane 39 can be combined, with the embodiment of FIG. 2C including a movable nozzle ring 135. In addition, the embodiment of

FIGS 3A-3B including a, ozzle ring 235 with movable sealing vanes 239 can. be combined with the embodiment of FIG. 3C including a movable nozzle ring 335.

Provision of a movable nozzle ring or nozzle ring vane can allow control of turbo wheel speed (TWS) and exhaust backpressure, as done in engines using a variable geometry turbocharger or exhaust throttle device. This can facilitate engine braking and. EGR flow control (via restriction/backpressure).

Addiiionally, current engine designs are limited in turbine design by various mechanical and physical constraints. With a turbine that is designed to run at a high speed (130,000 rpm, for example), the turbine must be designed to be mechanically sound at this speed and

aerodynamical ty capable, i.e., not hitting choked flow or surge, etc. If peak speed can be limited with a technology (to. say, 110,000 rpm), the turbine can be redesigned to new constraints, and turbine efficiency can be improved. So, controlling speed allows for a more optimal design overall.

Aspects of the present invention permit providing substantially all of the advantages of a

VGT in any turbine, not just a turbine that is part of a mechanically coupled turbocharger unit.

In the present application, the use of terms such as "including" is open-ended and is intended to have the same meaning as terms such as "comprising" and not preclude the presence of other structure, material or acts. Similarly , though the use of terms such as "can" or "may" is intended to be open-ended and to reflect that structure, .material., or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presentl considered to be essential, they are identified as such.

While this invention has been illustrated and described in accordance wit a preferred embodiment, it is recognized thai variations and changes may he made therein without departing from the invention as set forth in the claims.