Rotary valve

A rotary turbine bypass valve comprises a valve chamber and a valve rotor. The chamber is positioned at a junction of an inlet port, an outlet port and a bypass port. The inlet port is configured to receive exhaust gas, the outlet port is configured to fluidly communicate with a turbine inlet, and the bypass port is configured to fluidly communicate with an exhaust aftertreatment device.The rotor comprises a first and second recess, the first recess defining a primary flow passage, the second recess defining a secondary flow passage. The rotor is rotatable between a first position in which the rotor substantially blocks exhaust gas flow through the bypass port and a second position in which the rotor permits such. The secondary flow passage is configured to selectively permit fluid communication between the inlet port and the bypass port when the primary flow passage is partially blocked.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage application under 35 U.S.C. § 371 of PCT Application No. PCT/GB2019/053191, filed Nov. 11, 2019, which claims priority to U.K. Application No. 1818505.8, filed Nov. 13, 2018, the entire disclosures of which being hereby expressly incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a rotary valve. In particular, the present disclosure relates to a rotary turbine bypass valve suitable for bypassing an inlet to a turbine.

BACKGROUND

Turbines are well known devices for converting the kinetic energy within a flowing gas into useful work. In particular, known turbines convert the kinetic energy of flowing gas into rotation of a rotor (or turbine wheel) of the turbine. The rotation of the rotor may be transmitted by a suitable linkage to any device suitable for doing useful work. Examples of such devices include a power generator (such that the turbine forms part of a power turbine) and a compressor (such that the turbine forms part of a turbocharger).

As is well known in the art, turbochargers function by their turbine receiving exhaust gas from an internal combustion engine and consequently rotating a turbine wheel of the turbocharger so as to drive rotation of a compressor wheel. The compressor wheel draws in gas and pressurises it so that the gas output by the compressor is at an elevated pressure (or boost pressure) as compared to that at the inlet of the compressor. The output of the compressor of the turbocharger (i.e. the gas at boost pressure) can be fed to an inlet of the internal combustion engine of which the turbocharger forms part.

In some applications of turbine, a turbine bypass valve may be required to enable exhaust gas produced by the engine, to which the turbine is attached, to bypass the turbine so the exhaust gas flows to an exhaust aftertreatment system of the engine without passing through the turbine.

One known type of turbine bypass valve is a rotary valve. A rotary valve includes a housing defining a valve chamber positioned at a junction of an inlet port, an outlet port and a bypass port. A valve rotor is supported for rotation in the valve chamber. The valve rotor is rotatable about a valve axis between a first position in which the valve rotor permits gas flow through the bypass port and a second position in which the valve rotor blocks gas flow through the bypass port.

There exists a need to provide an alternative rotary turbine bypass valve which overcomes one or more of the disadvantages of known bypass valves whether set out above or otherwise. Additionally, there is a need for an alternative rotary turbine bypass valve.

SUMMARY

According to a first aspect of the disclosure there is provided a rotary turbine bypass valve for an engine arrangement, the rotary turbine bypass valve comprising:

a valve chamber positioned at a junction of an inlet port, an outlet port and a bypass port, the inlet port configured to fluidly communicate with a flow of exhaust gas from an engine, the outlet port configured to fluidly communicate with an inlet of a turbine, and the bypass port configured to fluidly communicate with an exhaust aftertreatment device; and

a valve rotor supported for rotation, about a valve axis, within the valve chamber, the valve rotor comprising a first recess and a second recess, the first recess defining at least part of a primary flow passage, the second recess defining at least part of a secondary flow passage;

wherein the valve rotor is rotatable about the valve axis between a first position in which the valve rotor substantially blocks exhaust gas flow through the bypass port and a second position in which the valve rotor permits exhaust gas flow through the bypass port; and

wherein the secondary flow passage is configured to selectively permit fluid communication between the inlet port and the bypass port when the primary flow passage is at least partially blocked.

The engine arrangement may form part of an automotive vehicle such as an automobile. More specifically, the vehicle may be a car, truck, bus, train or the like. The engine arrangement may be an internal combustion engine. The internal combustion engine may be a petrol engine or a diesel engine. The internal combustion engine may otherwise be a natural gas or Liquefied Petroleum Gas (LPG) engine, or some other variety of engine. The engine arrangement may be a hybrid arrangement which comprises the aforementioned internal combustion engine.

The turbine may form part of a turbocharger or a power turbine.

The valve chamber may be generally cylindrical. The valve chamber may be a blind bore.

The inlet port, bypass port and outlet port may be arranged in any appropriate relative orientation. One such example, when viewed in axial cross-section (i.e. cross-section normal to the axis of rotation of the rotary valve), the outlet port is generally opposite the inlet port and the bypass port is disposed between the inlet port and the outlet port. The bypass port may be closer to the inlet port than the outlet port. The bypass port may be substantially next to the inlet port. An angle between the inlet port and the bypass port may be acute i.e. less than 90°.

The inlet port, bypass port and outlet port may have any appropriate geometry. For example, the ports may be generally circular, generally elliptical, generally rectangular or some other polygonal shape. The ports may not all have the same geometry and/or dimensions. The ports may not all have the same cross-sectional area.

The inlet port, bypass port and outlet port may be directly connected to their respective regions/components of the engine arrangement with which they are in fluid communication. Alternatively, other components or connections may be present between the ports and the regions/components of the engine arrangement with which they are in fluid communication. For example, other components or connections may interpose the engine of the vehicle and the inlet port.

The flow of gas exhaust gas from the engine may comprise all of the exhaust gas from the engine, or a portion thereof.

The turbine may be a dual-inlet or twin-volute turbine. Alternatively, the turbine may be a single-inlet turbine. The turbine may be a fixed geometry turbine. The turbine may be a variable geometry turbine.

The exhaust aftertreatment device may comprise one or more of a selective catalytic reduction (SCR) catalyst, diesel particulate filter (DPF) or other particulate filter, Diesel Oxidation catalyst, Lean NOx catalyst, NOx absorber, or any other appropriate exhaust aftertreatment technology. The exhaust aftertreatment device may form part of an exhaust system. The exhaust system may further comprise a reductant. The reductant may otherwise be referred to as a reducing agent.

The exhaust aftertreatment device may perform more efficiently at a higher temperature than room temperature. The exhaust aftertreatment device may perform more efficiently with increasing temperature. That is to say, increasing the temperature of the exhaust gas flow may increase the efficiency of performance of the exhaust aftertreatment device. The exhaust aftertreatment device may have an activation or operating temperature which it must reach before the device functions to an acceptable efficiency.

The valve rotor may be generally cylindrical. The valve rotor may be manufactured from metal. The valve rotor may incorporate a spindle about which the valve rotor rotates. A first end of the spindle may be received in a corresponding bore in the valve chamber. A bush may be seated in the bore such that the spindle is received in the bush and is thus able to rotate in the bush. A second end of the spindle may be received in a second bush. An actuator may be used to control the rotational position of the valve rotor and hence the state of the rotary turbine bypass valve. One of the spindles may be mechanically linked to (or in rotational communication with) the actuator. In particular, one of the spindles may be directly connected to the actuator.

The valve rotor may completely block exhaust gas flow through the bypass port when in a bypass port blocking position. Alternatively, the valve rotor may substantially block exhaust gas flow through the bypass port when in the bypass port blocking position. If the valve rotor is able to rotate to a position whereby the outlet port is substantially blocked, some leakage through the outlet port may be allowable. Alternatively, in some embodiments, the valve rotor may be able to rotate to a position whereby the outlet port is completely blocked.

The valve rotor may incorporate sealing features to reduce leakage of exhaust gas flow through the bypass port when in the bypass port blocking position.

The bypass port may be connected directly, or indirectly, to the exhaust aftertreatment device. That is to say, the bypass port may, in some embodiments, be connected to the exhaust aftertreatment device via an interposing passage or component. In some embodiments, the bypass port may be connected to a turbine outlet passage, and the turbine outlet passage may then be connected to the exhaust aftertreatment device.

The disclosure provides the benefit that the temperature of the exhaust gas which flows to the aftertreatment device via the bypass port can be increased. This is owing to the at least partial blockage of the primary flow passage. The secondary flow passage provides fluid communication between the inlet port and the bypass port even when the primary flow passage is at least partially blocked. This means that even at low engine loads and RPM's, whereby the exhaust gas temperature would normally not be sufficiently high to activate or increase the efficiency of the aftertreatment device, the exhaust gas temperature and/or pressure can be adjusted to activate or increase the efficiency of the aftertreatment device.

The second recess may be smaller than the first recess.

In other words, a volume of (or associated with, or defined by) the second recess may be less than a volume of (or associated with, or defined by) the first recess.

The second recess being smaller than the first recess is advantageous in that the primary flow passage is therefore larger than the secondary flow passage. The reduced cross-section of the secondary flow passage assists in increasing the back pressure of the exhaust gas and further increasing the temperature of the exhaust gas (which may flow to the exhaust aftertreatment device) as a result thereof.

The second recess may span at least a portion of an outer circumference of the valve rotor.

The second recess is advantageously easier to manufacture when it spans at least a portion of the outer circumference of the valve rotor.

The second recess may oppose the first recess.

The first and second recesses opposing one another is intended to mean that the recesses are disposed across from one another about the valve axis. Put another way, the first and second recesses may be diametrically opposed.

Such an arrangement may be advantageous for reasons of improved balancing of the valve rotor. That is to say, the valve rotor may be more balanced for rotation about the valve axis, which may be desirable for reasons of reduced wear and improved longevity.

The first and second recesses may be separated by a barrier.

The barrier may otherwise be referred to as a sealing section.

The barrier may defines a chord of the valve rotor.

The valve rotor may be movable about the valve axis to selectively open and close the primary flow passage whilst the secondary flow passage remains open.

The aforementioned function may otherwise be referred to as modulation.

Modulation is advantageous in that the pressure of the exhaust gas can be adjusted. As a result, the exhaust temperature can also therefore be adjusted. This can be used to ensure that the back pressure generated across the rotary valve is not unnecessarily high when not required. An increased back pressure reduces the fuel economy of the engine. In other words, the back pressure is inversely proportional to the fuel economy. Put another way, once a required temperature of exhaust gas is reached, modulation can be used to reduce the back pressure and therefore increase the fuel economy.

The secondary flow passage may be configured to selectively provide fluid communication between the inlet port and the bypass port when the primary flow passage is substantially blocked.

The primary flow passage being substantially blocked whilst the secondary flow passage is open leads to the highest temperatures and pressures of the exhaust gas which can be actively diverted to the bypass port. This is because substantially all of the exhaust gas flows through the secondary flow passage to the bypass port.

The first and second recesses may occupy substantially the same axial extent of the valve rotor.

Put another way, the first and second recesses have substantially the same axial lengths along the length of the valve rotor.

The second recess may be one or more of generally rectangular, triangular, and/or teardrop-shaped.

Generally rectangular may be a geometry having two pairs of substantially parallel sides. The corners of the rectangular geometry may be filleted i.e. rounded.

Generally triangular may mean a shape with a substantially horizontal base, and two inclined sides stemming from ends of the base and merging at an apex. The apex may be rounded. The other corners may be rounded. The inclines sided may be arcuate. Generally triangular may be interpreted to include a shape like that of a sole plate of an iron.

Teardrop-shaped may refer to an ellipse with a pointed end.

As well as the above shapes, the second recess may be any one of a variety of further shapes. For example, the second recess may be some arbitrary shape, such as substantially wine-glass-shaped (e.g. substantially semicircular with a pointed tip).

The second recess being any one or more of the above shapes or geometries is intended to refer to a shape defined by the recess when the valve rotor is viewed from a radial perspective. In other words, the shape which would be formed if the (opening of the) second recess was to be filled with material, and the material was then removed and laid flat.

Where the second recess is of a geometry with a cross-sectional area which changes with the circumferential position about which the cross-section is taken (i.e. triangular, teardrop-shaped etc.), the second recess may be said to have a wide end and a thin end. Put another way, where a width of the second recess varies with a circumferential position about the valve rotor, the second recess may be said to have a wide end and a thin end.

It may be advantageous to have the second recess oriented such that the thin end is more directly exposed to the inlet port than the deep end is exposed to the inlet port when the rotary valve exhibits a thermal management regime. This is such that the thin end can be used to gradually open the secondary flow passage.

Alternatively, it may be desirable to have the second recess oriented such that the deep end is more directly exposed to the inlet port than the shallow end is. This may be for the reason that it may be desirable to initially open the secondary flow passage to a greater extent, and then gradually further open the secondary flow passage.

The aforementioned geometries may refer to the second recess when an outer surface of the valve rotor is unwrapped. That is to say, the geometry of the second recess may refer to the shape of the second recess if the cylindrical exterior of the valve rotor was to be laid out flat.

The geometry and/or depth of the second recess, or second recesses, may be varied to modify the flow area versus rotational position of the valve rotor behavior, or characteristics.

The second recess may have a substantially uniform depth.

Substantially uniform depth may mean that the second recess is of a substantially constant depth. In other words, the second recess is recessed to substantially the same extent across the whole second recess.

A uniform, or substantially uniform, depth of the second recess may be advantageous for reasons of simpler manufacture.

The second recess may have a non-uniform depth.

The second recess having a non-uniform depth may mean that the depth of the second recess varies substantially continuously circumferentially and/or axially. Alternatively, the non-uniform depth may mean that the second recess has discrete variations of depth e.g. a first section recessed to a first extent, and a second section recessed to a second extent. The non-uniform depth may also refer to a repeating, or non-repeating, pattern of depths.

The non-uniform depth of the second recess may be beneficial for reasons of being able to adjust, more accurately, the extent to which the secondary flow passage is open. That is to say, the non-uniform depth of the second recess may allow the extent of fluid communication between the inlet port and the bypass port, via the secondary flow passage, to be varied to a greater degree.

The depth may otherwise be described as a channel depth.

The non-uniform depth of the second recess may give rise to different flow areas, or cross-sectional areas, through which exhaust gas can flow at different rotational positions of the valve rotor. Different rotational positions of the valve rotor may otherwise be described as different angular positions of the valve rotor.

Where the second recess is of a non-uniform depth, the second recess may be said to have a shallow end and a deep end.

It may be advantageous to have the second recess oriented such that the shallow end is more directly exposed to the inlet port than the deep end is exposed to the inlet port when the rotary valve exhibits a thermal management regime. This is such that the shallow end can be used to gradually open the secondary flow passage.

Alternatively, it may be desirable to have the second recess oriented such that the deep end is more directly exposed to the inlet port than the shallow end is. This may be for the reason that it may be desirable to initially open the secondary flow passage to a greater extent, and then gradually further open the secondary flow passage.

The second recess may be one of two second recesses forming part of a secondary arrangement, and the first recess may be one of two first recesses forming part of a primary arrangement.

A valve incorporating two first recesses and two second recesses is advantageously configured for use with a twin-inlet turbine.

Either or both of the second recesses may be one or more of generally rectangular, triangular, and teardrop-shaped.

Both of the second recesses may have substantially the same shape.

Same shape may refer to an outer geometry, boundary or perimeter of the recess, rather than a depth thereof.

The second recesses may have substantially the same depths.

In other words, a first of the second recesses may be recessed to substantially the same extent as a second of the second recesses.

The second recesses may have different depths.

The second recesses may be circumferentially aligned.

Put another way, the circumferential positions of the second recesses, about an outermost radius of the valve rotor, when viewed from an axial direction of the valve rotor, may be substantially the same. That is to say a portion of one of the second recesses has the same circumferential position as that of the equivalent portion of the other second recess.

The second recesses may be circumferentially offset.

In other words, there may be rotational offset of one of the second recesses relative to the other. That is to say a portion of one of the second recesses is circumferentially offset relative to the equivalent portion of the other second recess. This may be desirable for reasons of being able to provide different flow characteristics through each of the two inlets of a twin-inlet turbine.

The first and/or second arrangements may be symmetrically disposed about a length of the valve rotor.

The first and/or second arrangements being symmetrically disposed about the length of the valve rotor may be beneficial for reasons of improved balance of the valve rotor.

The turbine may form part of a turbocharger.

The disclosure is particularly advantageous when the turbine forms part of a turbocharger because the disclosure can be used to control the speed of the turbine and so boost pressures generated by a compressor of the turbocharger.

The turbocharger comprises the turbine and a compressor, the compressor being rotationally coupled to the turbine so as to be driven thereby.

According to a second aspect of the disclosure there is provided an engine arrangement comprising an engine, a turbine and the rotary turbine bypass valve according to the first aspect of the disclosure.

Optionally the engine arrangement comprises a turbocharger, the turbine forming part of the turbocharger.

According to a third aspect of the disclosure there is provided a method of operating the rotary turbine bypass valve according to the first aspect of the disclosure, wherein the rotary turbine bypass valve exhibits the following flow regimes in order as the valve rotor rotates from a position in which the outlet port is substantially blocked:

(i) a complete turbine bypass regime in which the outlet port is substantially blocked by the valve rotor;

(ii) a braking regime in which the inlet port is substantially blocked;

(iii) a thermal management regime in which the primary flow passage is at least partially blocked and the secondary flow passage permits fluid communication between the inlet port and the bypass port;

(iv) a 100% turbine regime in which the bypass port is substantially blocked and the inlet and outlet ports are open; and

(v) a wastegate regime in which the outlet port is open and the bypass port is at least partially open.

The rotational position of the valve rotor may be adjusted from the position of step (iii) to increase or reduce the extent of the blockage of the primary flow passage to adjust a temperature and/or pressure of the exhaust gas in the inlet port.

The adjustment of temperature and/or pressure of the exhaust gas may otherwise be referred to as modulation.

No fuel may be supplied to the engine during step (ii).

It will be appreciated that any of the above-discussed aspects of the disclosure may, where appropriate, be combined with one or more other aspects of the disclosure. Furthermore, an optional feature described in relation to one of the aspects of the disclosure may, where appropriate be an optional feature of one of the other aspects of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

FIG.1ashows a schematic view of a known engine arrangement10a. The engine arrangement includes a plurality of combustion chambers12which are connected to an inlet manifold14and an outlet manifold16. The outlet manifold16is separated into a first portion16aand a second portion16b. The first portion16aof the outlet manifold is connected to a first set (not shown) of the combustion chambers12, and the second portion16bof the outlet manifold16is connected to a second set (again, not shown) of the combustion chambers12.

The engine arrangement also comprises a turbocharger18having, as is well known, a turbine20and a compressor22. The engine arrangement further includes an exhaust aftertreatment system24, an EGR (exhaust gas recirculation) circuit26, which includes an EGR valve28, and a turbine bypass valve30. The exhaust aftertreatment system24comprises one or more exhaust aftertreatment devices, as will be explained in detail below.

In use, the combustion chambers12are supplied with fuel and air, the air being provided from the atmosphere37via the engine air inlet32, the air passing through the compressor22of the turbocharger18and inlet manifold14. Once the fuel and air has been burnt in the combustion chambers12, exhaust gas is produced which passes to the outlet manifold16. The exhaust gas from the first portion16aof the exhaust manifold16is supplied to a T-junction34at which it is split so that it flows both to an EGR circuit26and to a first inlet20aof the turbine20of the turbocharger18. The EGR circuit26passes back to the inlet manifold14and the amount of exhaust gas which passes into the EGR circuit26is controlled by the EGR valve28. The manner in which the EGR circuit functions is entirely conventional and is not key to the present disclosure. Consequently, for the sake of brevity, further discussion as to the operation of the EGR circuit is omitted.

The turbine20of the turbocharger18is a twin inlet (or twin volute) turbine. As such, the turbine includes a second inlet20b. This inlet20bof the turbine20is supplied by a first outlet30aof the bypass valve30. The bypass valve30is in turn supplied with exhaust gas from the second portion16bof the exhaust manifold16via an inlet30bof the bypass valve30.

The exhaust gas provided to the turbine20of the turbocharger18via the inlets20a,20bcauses a turbine wheel (not shown) of the turbine20to rotate. The exhaust gas then exits the turbine20via the turbine outlet20cand passes to an exhaust aftertreatment system24(which may include, for example, a particulate trap and/or selective catalytic reduction [SCR] arrangement). The exhaust gas passes from the turbine outlet20cto the exhaust aftertreatment system24via a turbine outlet passage20d. The exhaust gas then exits the aftertreatment system24via an engine outlet36to atmosphere37. The rotation of the turbine wheel of the turbine, caused by the exhaust gases provided to the turbine20, causes rotation of a compressor wheel (again, not shown) of the compressor18. Rotation of the compressor wheel results in air at atmospheric pressure being drawn into the compressor through the engine inlet32to be pressurised to an elevated (or boost) pressure by the compressor wheel. This pressurised gas is then supplied to the inlet manifold14as previously discussed.

The bypass valve30also includes a second outlet30c(or bypass outlet) which is connected to the aftertreatment system24(without going through the turbine). Whilst the second outlet30cis connected to the exhaust aftertreatment system24without going through the turbine20, in some embodiments the second outlet30cmay be in fluid communication with the turbine outlet20c. That is to say, rather than being connected directly to the exhaust aftertreatment system24, the second outlet30cmay be connected to the exhaust aftertreatment system24via the turbine outlet passage20d. This is illustrated inFIG.1b, and will be described in more detail below.

The bypass valve30can be controlled so that it is possible to selectively open the second outlet30c. When the second outlet30cis open, at least some of the exhaust gas from the second portion16bof the outlet manifold16which would have otherwise passed to the inlet20bof the turbine20can flow via the outlet30cto the aftertreatment system24. Such gas is said to bypass the turbine20. The ability for gas to bypass the turbine20may be advantageous in several situations. First, in a situation where it is desired to reduce the speed of the turbine, for example when the turbine20is over-speeding, the ability to bypass the turbine, and thereby reduce the amount of exhaust gas being supplied to the turbine will reduce the amount of exhaust gas rotating the turbine wheel and hence reduce the speed of the turbine wheel. Secondly, in some applications, the aftertreatment system24may only function effectively when it is at a required operating temperature. This may be the case when, for example, the after-treatment system24includes a temperature-sensitive catalyst. The required operating temperature of the aftertreatment system24may be considerably in excess of room temperature. Consequently, at some point during the operation of the engine arrangement10a(for example, just after engine switch on) the aftertreatment system24may be operating at a temperature below the required operating temperature. In this situation, the bypass valve30can be opened such that some of the hot exhaust gas, which would otherwise pass to the turbine20, passes to the aftertreatment system24without passing through the turbine20, thereby causing the temperature of the after-treatment system24to be raised relatively quickly so that it can reach its operating temperature.

Once it is no longer desired to allow some of the exhaust gas from the second portion16bof the exhaust manifold16to bypass the turbine20, the bypass valve30can be actuated so as to close it, thereby closing the second outlet30cand ensuring that all of the exhaust gas passing into the bypass valve30from the second portion16bof the exhaust manifold16passes to the turbine20of the turbocharger18.

The engine arrangement10adescribed above provides context as to the operation of a turbine bypass valve. It will be appreciated that a bypass valve according to the present disclosure may be utilised as part of any appropriate engine arrangement. For example, the engine arrangement discussed above includes a two-part exhaust manifold arrangement. Some suitable arrangements may instead include a single exhaust manifold with the valve being located between the exhaust manifold and the turbine inlet. In addition, although the disclosure is described in relation to a turbine which forms part of a turbocharger, the disclosure equally applies to any type of turbine, for example, but not limited to, a turbine that forms part of a power turbine. The turbine may include a twin inlet or twin volute as discussed above. Alternatively, the turbine may include any appropriate number of inlets and/or volutes, such as a single inlet and a single volute.

FIG.1bshows an alternative engine arrangement10b. The engine arrangement10bofFIG.1bis substantially the same as the engine arrangement10aofFIG.1a, save for the connection of the second outlet30cof the bypass valve30. Given the general similarities between the engine arrangements10a,10b, like features are indicated using the same reference numeral and will not be described in detail in connection withFIG.1b.

In the engine arrangement10b, the second outlet30cof the bypass valve30is connected to the exhaust aftertreatment system24via the turbine outlet passage20d. In other words, whilst in the engine arrangement10athere are two separate exhaust gas flows which enter the exhaust aftertreatment system24, in the engine arrangement10bthe two exhaust gas flows merge and enter the exhaust aftertreatment system as a single, combined flow. The combined flow passes through the turbine outlet passage20dand into the aftertreatment system24.

The specific structural details of a bypass valve according to the present disclosure are now discussed in more detail below.

FIG.2shows an enlarged schematic view of the valve30. Features of this figure which correspond to those ofFIG.1have been given the same reference numerals.

FIG.3shows a perspective view of a valve rotor40. As will be described in greater detail below, a combination of the valve rotor40and a valve chamber (not shown inFIG.3) make up the valve30, herein referred to as the rotary valve30.

The valve rotor40rotates within the valve chamber to selectively permit or prevent fluid communication between an inlet port, an outlet port and a bypass port of the valve chamber. The inlet port, outlet port and bypass port correspond with the inlet30b, the first outlet30aand the second outlet30cof the rotary valve30as shown inFIGS.1and2).

Various operating modes of, and associated flow regimes of exhaust gas passing through, the rotary valve30will be described and illustrated in connection withFIGS.4and5below.

Returning toFIG.3, the valve rotor40comprises a rotor body42and spindles44a,44bextending therefrom. Spindles44a,44bdefine an axis A1about which the valve rotor40rotates. The axis A1may otherwise be referred to as the valve axis.

The rotor body42comprises end walls46a,46b. These end walls46a,46bare axially offset from one another and so may be referred to as axially offset end walls. The axially offset end walls46a,46bdefine outermost edges of the rotor body42. When the valve rotor40is located in the valve chamber, the axially offset end walls46a,46bare in facing relations with corresponding walls of the valve chamber. That is to say, the axially offset end walls46a,46bare received by the valve chamber.

The spindles44a,44bextend axially away from the axially offset end walls46a,46b. The spindles44a,44bare generally cylindrical and provide an axle about which the valve rotor40rotates. The spindles44a,44bare received by corresponding bores in the valve chamber. Spindles44a,44bmay be a geometry other than generally cylindrical provided that the valve rotor40is still able to rotate about the valve axis A1.

The rotor body42also comprises opposing internal walls48a,48b. The opposing internal walls48a,48bare also axially offset along valve axis A1. Each of the internal walls48a,48balso opposes a corresponding end wall46a,46brespectively.

Disposed between internal walls48a,48bis a sealing section50. Sealing section50comprises an internal surface52and an external surface54.

A combination of the internal surface52, and the internal walls48a,48bdefine a first recess56. As such, the valve rotor40comprises the first recess56. The first recess56, in use, defines at least part of a primary flow passage between one or more of the inlet port, outlet port and bypass port. This is described in greater detail below. The first recess56may otherwise be described as a passage, or cavity.

The external surface54of the sealing section50comprises a second recess58. In use, the second recess58defines at least part of a secondary flow passage, which will again be described in more detail below.

When the valve rotor40is positioned in the valve chamber, the rotational position of the valve rotor40dictates whether exhaust gas flow is permitted through, or blocked from passing through, the bypass port. When the valve rotor40is in a bypass port blocking position, the valve rotor40is in a rotational position such that the external surface54of the sealing section50covers, or substantially covers, the bypass port. Exhaust gas flow is thereby substantively prevented from flowing through the bypass port.

When the valve rotor40is not in a bypass port blocking position, the valve rotor40is in a rotational position such that the relative alignment of the external surface54of the sealing section50and bypass port permits the exhaust gas flow through the bypass port. That is to say, exhaust gas is able to flow into the bypass port via the first recess56of the valve rotor40. Depending upon the geometry of the valve rotor40, when the valve rotor40is not in the bypass port blocking position, the internal surface52of the sealing section50may obstruct the flow of exhaust gas such that the flow is impeded and is deflected towards the bypass port. That is to say, in certain valve rotor40positions, and with certain valve rotor40geometries, the internal surface52may act as a deflector plate for the exhaust gas flow. It will be appreciated that the exhaust gas is able to flow through the first recess56of the valve rotor40.

It will also be appreciated that exhaust gas can flow through the second recess58of the valve rotor40. As such, in some rotational positions of the valve rotor40, the second recess58provides fluid communication between ports to thereby allow exhaust gas to flow therebetween. This is particularly advantageous in arrangements whereby it is desired to at least partially block the inlet port, for example in order to increase exhaust gas temperature, whilst still diverting a proportion of the exhaust gas flow via the bypass port. The second recess58enables this functionality. More detail will be provided in connection with this, and the other, operating modes below.

The valve rotor40may be turned from a single piece of metal. More broadly, features of the valve rotor40may be produced by machining. Alternatively, the end wall sections may be manufactured separately before being combined with the sealing section50in a separate operation. Further alternatively, the valve rotor40may be cast. The valve rotor40may include sealing features in order to improve valve performance.

The valve rotor40illustrated inFIG.3is adapted for use with a single inlet turbine. That is to say, there is a single first recess56and a single second recess58. However, it will be appreciated that twin entry or twin volute turbines also exist, and that is desirable to be able to use a rotary valve according to the disclosure in combination therewith. Accordingly,FIG.4shows a perspective view of a second embodiment of a valve rotor60.

The valve rotor60is adapted for use with a twin entry or twin volute turbine. As such, there are two arrangements of corresponding first and second recesses. A first arrangement62comprises the two first recesses56a,56b. A second arrangement64comprises the two secondary recesses58a,58b. The first and second arrangements may otherwise be referred to as first and second pairs. It will be appreciated fromFIG.4that a first combination of the first recess56aand the second recess58acorrespond with a first entry passage or volute of the turbine, whilst a second combination of the corresponding first recess56band second recess58bcorrespond with a second entry passage or volute of the turbine.

The valve rotor60shares many features in common with the valve rotor40, and so these features will not be described in detail in connection withFIG.4. However, of note, due to the presence of two first recesses56a,56b, a wall section66is present in the valve rotor60. The wall section66separates the two first recesses56a,56b.

Either or both of the valve rotors40,60may be symmetrical about the valve axis. In other words, either or both of the valve rotors40,60may be symmetrical along a length of the valve rotors40,60. Either or both of the first and second arrangements62,64may be symmetrically disposed about a length of the valve rotor60. Symmetrical features of the valve rotors40,60may be desirable for reasons of improved balancing of the rotary valve30, and so improved performance.

FIG.5is a schematic side view of the rotary valve30. In other words,FIG.5shows the valve rotor40inserted in a valve chamber70. Of note, whilst valve rotor40is described in connection withFIGS.5to9, the valve rotor60according to the alternative embodiment is operated in the same way, and so the description is equally applicable.

InFIG.5the valve rotor40is shown in a cross section view as indicated by plane P1inFIG.3. Cross hatching is used to indicate the cutaway view of the valve rotor40. In particular, a cross hatched section is indicated on the sealing section50, which may otherwise be referred to as a barrier. Valve axis A1is also indicated onFIG.5, along with first and second recesses56,58. Finally, the inlet port30b, outlet port30aand the bypass port30care also labelled onFIG.5.

As has been described in connection with the previous figures, rotation of the valve rotor40about the valve axis A1can be used to selectively block or open one or more of the inlet port30b, outlet port30aand bypass port30c. Exhaust gas flowing through the inlet port30bcan therefore be selectively directed to flow through the first recess56and/or the second recess58, or through neither recess.

To recap the description in connection withFIGS.1and2, the inlet port30bis connected to the engine, the outlet port30ais connected to an inlet of the turbine20, and the bypass port30cis connected to the exhaust aftertreatment system24. Specifically, the inlet port30bis downstream of the engine, the outlet port30ais upstream of the turbine20and the bypass port30cis upstream of the exhaust aftertreatment system24.

The various flow regimes which the rotary valve can be used to implement will now be described. For the purposes of this document, the terms flow regime and operating mode are used interchangeably. These terms simply refer to the different manners of valve operation which are attributable to the various rotational positions of the rotary valve30, specifically the valve rotor40thereof.

FIG.5shows the rotary valve30in a 100% turbine regime. That is to say, in theFIG.5arrangement, the exhaust gas which flows through the inlet port30balso flows through the outlet port30a. Substantially all the exhaust gas which enters the valve chamber70is directed through the outlet port30a, towards the turbine. The bypass port30cis blocked, or substantially blocked, in this arrangement. That is to say, there is minimal, if any, exhaust gas flow through the bypass port30c, and so to the aftertreatment system. In the rotational position of the valve rotor40shown inFIG.5, exhaust gas flows via the first recess56. In other words, substantially all of the exhaust gas flows through the primary flow passage. As mentioned above, the first recess56defines at least part of the primary flow passage. Minimal, if any, exhaust gas flows via the secondary flow passage in the 100% turbine regime. Again, as mentioned above, the secondary flow passage is at least partly defined by the second recess58.

TheFIG.5arrangement may otherwise be described as the valve rotor40being in its fully open position. Accordingly, there is minimal pressure drop across the rotary valve30when the valve rotor40is in the fully open position. In other words, there is minimal resistance to the exhaust gas flow across the rotary valve30.

The 100% turbine regime is most likely to be used when the engine and turbine are operating at a peak torque condition. The 100% turbine regime is therefore likely to be used when it is desired that all of the exhaust gas flow is directed through the turbine.

FIG.6shows the rotary valve30in a wastegate mode. The wastegate mode may otherwise be referred to as a partial wastegate mode, or a partial bypass mode. In the wastegate mode, the outlet port30ais open and the bypass port30cis also open. Furthermore, the inlet port30bis also not obstructed by the sealing section50. In other words, the inlet port30bis also open. All ports are therefore open. In the wastegate mode, and as suggested by the name, some of the exhaust gas flow, which would otherwise flow through the outlet port30a, is instead directed to the bypass port30c. This is equivalent to the typical function of a wastegate in a turbocharger, which reduces the proportion of the flow which is expanded across the turbine by diverting a proportion of the flow before it reaches the turbine.

The wastegate mode may be used in a number of different scenarios including preventing turbine overspeed. In other words, the wastegate mode may be used to control the rotational speed of the turbine. Such controlling may include reducing the rotational speed of the turbine. Another scenario in which the wastegate mode may be used is to control the boost pressure of air supplied to the engine when the turbine forms part of a turbocharger. In such circumstances, the speed of the turbine is representative of the boost pressures generated by the compressor (owing to the compressor being driven by the turbine). As such, the wastegate mode can be used to control the boost pressure delivered by a turbocharger to the engine. Controlling the boost pressure may include either increasing, or reducing, the boost pressure delivered to the engine. In the wastegate mode, substantially all of the exhaust gas flows through the primary flow passage. Substantially no exhaust gas flows through the secondary flow passage.

Due to the position of the valve rotor40in the wastegate mode, there is exhaust gas flow through both the outlet port30aand the bypass port30c. That is to say, all of the ports are open. A greater proportion of the exhaust gas flows through the outlet port30athan the bypass port30c. This may be at least in part due to the relative position of the bypass port30cto the inlet port30band/or due to the relative cross-sectional area of the outlet port30aand the bypass port30c.

InFIG.7the rotary valve30is shown in a complete turbine bypass mode. In this mode, the outlet port30ais substantially blocked. That is to say, the sealing section50substantially prevents any exhaust gas from flowing through the outlet port30a. With the inlet port30band bypass port30copen, the exhaust gas flows via the inlet port30band out through the bypass port30c. Substantially all of the exhaust gas therefore flows to the exhaust aftertreatment system. The exhaust gas flows through the first recess56. In other words, the exhaust gas flows through the primary flow passage. Substantially no exhaust gas flows through the second recess58, and so the secondary flow passage.

In this mode, the temperature of the exhaust gas is not reduced due to it being expanded across the turbine. That is to say, because the outlet port30ais blocked, the exhaust gas does not flow to the turbine and so is not expanded across thereacross. The exhaust gas temperature is therefore not significantly reduced. Furthermore, because no exhaust gas is expanded across the turbine, minimal work is done by the exhaust gas in driving the turbine. As such, the supply of air to the engine via the compressor, where the turbine forms part of a turbocharger, is greatly reduced. This further increases the temperature of the exhaust gas, where the same fuel rate is provided to the engine, owing to a reduction in the air to fuel ratio. With that said, in practice the bypass port30cmay be reduced in cross sectional area in order to further increase engine pumping work (explained in more detail below). This may require that more fuel is provided to the engine in order to overcome the increase in pumping work (due to the engine pumping exhaust gases against the higher pressure gradient). In other words, more fuel may be provided to the engine, if it is desired to maintain the same engine speed, due to the increase in pumping work.

FIG.8shows the rotary valve30in a braking mode. As shown inFIG.8, in the braking mode the inlet port30bis substantially blocked by the sealing section50. As such, there is minimal, if any, exhaust gas flow through either of the bypass port30cand the outlet port30a. Whilst the inlet port30bis substantially blocked, due to the pressure of the exhaust gas there may be some leakage past, or around, the valve rotor40. There may therefore be a small amount of leakage flow around the valve rotor40, which flows into the bypass port30cand/or the outlet port30a.

Typically in the braking mode, no fuel is supplied to the engine.

The rotational position of the valve rotor40in theFIG.8arrangement, or the braking mode, increases the pressure drop across the rotary valve30. As such, there is an increased back pressure both at, and upstream of, the inlet port30b. This increased back pressure necessitates an increase in the pumping work from the engine in order to continue to pump the exhaust gas across the increased pressure gradient. As such, more work is done by the engine in pumping out the exhaust gas than would normally be the case. Because of the increased back pressure, more of the work done by the engine is expended in pumping the exhaust gas. Less power is therefore available for driving the pistons and the crankshaft. This results in a braking force being exerted by the engine, which results in a slowdown of the vehicle. Because of the increased back pressure, and increase in pumping work, the temperature and/or pressure of the exhaust gas is also increased. The engine may be described as absorbing its power by virtue of the increased pumping work, to thereby provide braking power for the vehicle.

To summarise, in the braking mode there is minimal exhaust gas flow to the turbine through the outlet port30a, and minimal exhaust gas flow to the aftertreatment system through the bypass port30c. Substantially no exhaust gas flows through the primary flow passage.

FIG.9shows the rotary valve30in a thermal management regime. The thermal management regime may be otherwise described as a backpressure generation and/or improved aftertreatment heating mode or regime.

In the thermal management regime, the temperature of the exhaust gas flowing into the aftertreatment system via the bypass port30cis increased. In the thermal management regime, the inlet port30bis at least partly blocked by the sealing section50. Furthermore, the bypass port30cis open.

The flow of exhaust gas is directed predominantly from the inlet port30bto the bypass port30c. It is the second recess58which provides the fluid communication between the inlet port30band the bypass port30c. The secondary flow passage, which is at least partly defined by the second recess58, therefore permits fluid communication between the inlet port30band bypass port30c. In the specific rotational position shown inFIG.9, the first recess56also provides fluid communication between the inlet port30band the outlet port30a. In other words, the primary flow passage, at least partly defined by the first recess58, permits fluid communication between the inlet port30band the outlet port30a. This provides a useful “modulating” functionality (or modulation functionality) in that the rotational position of the valve rotor40can be adjusted to increase or reduce the proportion of the exhaust gas which flows through the outlet port30a. This will be described in greater detail below.

Substantially blocking the inlet port30bwhen the engine is in a non-braking, or fired, mode (i.e. when fuel is being provided to the engine) means that the resultant pumping work increases. The pumping work increasing leads to an increase in the exhaust gas temperature. This is due to the engine doing more work to pump the exhaust gas across the rotary valve30against the higher pressure gradient. The exhaust gas temperature increases according to the work done, which is defined by the integral of PdV (where P is equal to the pressure, and dV is equal to the change in volume).

When the engine is in a braking mode, some fuel may be supplied if required. However, the majority of the pumping work is caused by the pressure drop across the rotary valve30. In other words, most of the pumping work is due to gas from a cylinder (i.e. a combustion chamber of the engine) being forced into a higher pressure region of the rotary valve30, when the inlet port30bis substantially blocked, in comparison to the rotary valve30being open. Put another way, most of the pumping work is due to gas from the cylinder being forced into a higher pressure region upstream of the rotary valve30, caused by the inlet port30bof the rotary valve30being substantially blocked. This means that more work must be done by a piston in the cylinder to expel the exhaust gas. Specifically, more work must be done by the piston to expel the exhaust gas into the raised pressure region upstream of the rotary valve30. The addition of fuel, and subsequent combustion thereof, into the cylinder causes a significant increase in the volume of the gas because the combustion products take up a greater volume than the individual liquid fuel and air components. This increase in volume leads to an increase in the work done, as indicated by the equation set out above.

The exhaust gas temperature also increases due to the additional fuel which is needed in the engine to prevent the engine speed dropping below a target value. Because of the increase in pumping work, more fuel is required, by the engine, in order to maintain the same engine speed (as defined by the ECU). The increased amount of fuel in the engine results in a lower air to fuel ratio and thus a high temperature of the exhaust gas. The air to fuel ratio is further lowered due to the fact that the bulk of the exhaust gas is not flowing through the outlet port30ai.e. to the turbine. As such, when the turbine forms part of a turbocharger, minimal work is done by the exhaust gas to drive the turbine, and so minimal work is done to drive the compressor. This results in a low boost pressure i.e. a reduced amount of air, and at a lower pressure, being delivered to the intake manifold of the engine. This further reduces the air to fuel ratio and therefore further increases the exhaust gas temperature.

Returning to the modulation functionality briefly mentioned above, the back pressure across the rotary valve30can be modulated by rotating the valve rotor40in order to generate a desired exhaust gas temperature at the exhaust aftertreatment device. Such a desired temperature may be of the order of at least around 200° C., for example at least around 190° C. However, it will be appreciated that this is dependent upon the specific engine arrangement and, more specifically, the chemistry thereof. The modulation means that excess back pressure can largely be avoided. In other words, the inlet port30bis only substantially blocked to the extent required in order to obtain the desired exhaust gas temperature. This is beneficial in that increased back pressure results in a reduced fuel economy. As such, modulating the back pressure by rotating the valve rotor40can be used to improve fuel economy. This is achieved by avoiding an excessive back pressure and so excessively high amount of fuel injected into the engine. Put another way, the modulation involves selectively opening and closing the primary flow passage whilst the secondary flow passage remains open.

The modulation functionality is also beneficial in being able to avoid an overpressure condition in the exhaust manifold owing to the increase in backpressure upstream of the inlet port30b.

Modulation can therefore be used to adjust the back pressure, and so exhaust gas temperature, as required. Described another way, variation of the rotational position of the valve rotor40may be used to modulate the back pressure and so adjust the exhaust gas temperature.

There are some similarities between the complete turbine bypass regime shown inFIG.7and the thermal management regime shown inFIG.9. Both of these regimes provide fluid communication between the inlet port30band the bypass port30c. However, it will be noted that this is achieved by way of the primary and secondary flow passages respectively, or via first and second recesses56,58respectively.

The difference between the modes is that in the thermal management mode, shown inFIG.9, there is an increase in back pressure due to the inlet port30bbeing at least partially blocked by the sealing section50. Under certain low load engine conditions and/or low speed engine conditions the temperature of exhaust gas which is required in order to activate and/or increase the efficiency of operation of the exhaust aftertreatment system cannot be provided by only directing all of the exhaust gas from the inlet port30bto the bypass port30c. As such, in some circumstances an additional back pressure is required in order to further increase the temperature of the exhaust gas which flows through the bypass port30cand to the exhaust aftertreatment system. This is achieved by the thermal management regime, owing to the inlet port30bbeing at least partially blocked by sealing section50of the valve rotor40.

The second recess58therefore provides a simple to manufacture feature which can allow fluid communication between the inlet and bypass ports30b,30cwhilst the inlet port30bis at least partially blocked. This has the effect that an increase in the exhaust gas temperature can be obtained. Furthermore, the increased temperature exhaust gas can still be directed to the bypass port30c.

WhilstFIGS.5to9, i.e. the different modes of operation, have been described in connection with the valve rotor40according to the first embodiment (shown inFIG.3), it will be appreciated that the description and Figures are equally applicable to the twin passage variant of the valve rotor60as shown inFIG.4.

FIGS.10to13show perspective views of four different embodiments of valve rotors, similar to that shown inFIG.4. For ease of reference, the numerals of like features are incremented by 100 for each different embodiment.

Beginning withFIG.10, a valve rotor160is shown. The valve rotor160shares many features in common with the valve rotor60ofFIG.4, which will therefore not be described in detail.

Of note, the valve rotor160is rotated relative to the position of the valve rotor60ofFIG.4. Furthermore, the primary recess, or primary recesses, are not visible inFIG.10.

A secondary arrangement164of two second recesses158a,158bis visible inFIG.10. InFIG.10, the second recesses158a,158bare both generally rectangular. That is to say, both second recesses are defined by two pairs of substantially parallel sides. The second recesses158a,158btherefore both have substantially the same shape.

Each of the second recesses158a,158bare of uniform depth i.e. they are recessed to the same extent relative to an outer radius of the valve rotor160. Furthermore, each of the second recesses158a,158bhave substantially the same depth.

Of note inFIG.10, the second recesses158a,158bare not circumferentially aligned. That is to say, a first of the second recesses158ais disposed at a different circumferential position to a second of the second recesses158b. This is indicated by O1. An advantage of the circumferential offset is that the passage of exhaust gas flow through the bypass port whilst the rotary valve is in the thermal management regime can be more precisely controlled. For example, for a given rotational position of the valve rotor160, a first secondary flow passage defined by the first second recess158may be open. At the same rotational position of valve rotor160, a second secondary flow passage defined by the second second recess158bmay be closed. This has the effect that exhaust gas flow can pass through the first secondary flow passage, but not the second. Rotation of the valve rotor160in either direction can therefore be used to increase or decrease the proportion of exhaust gas which flows through the bypass port from the inlet port.

A cross-section plane C1is indicated on the valve rotor160, and will be discussed in more detail in connection withFIGS.14and15.

FIG.11shows a perspective view of a further embodiment of valve rotor260. Once again, the valve rotor260incorporates a secondary arrangement264of second recesses258a,258b.

The second recesses258a,258bare generally triangular. That is to say, they are each defined by a substantially horizontal base259a,261a, and two inclined sides259b,259c,261b,261cwhich stem from ends of the base and merge at an apex259d,261d. As illustrated inFIG.11, the inclined sides may be arcuate i.e. curved.

The generally triangular geometries of the second recesses258a,258bare just one example of a geometry having a cross-sectional area which changes along the circumference. In other words, as the circumferential position about the valve rotor260is changed, a cross-sectional area of the geometries of the second recesses258a,258balso changes. In this specific example, the cross-sectional area is greatest at the base of the triangle, and smallest at the apex. The second recesses258a,258bcan therefore be said to have a wide end, and a thin end, corresponding with the base and the apex respectively.

This difference in cross-sectional area of the second recesses258a,258bcan be used to determine how to orient the geometries of the second recesses258a,258bon the valve rotor260. This, in turn, can be used to allow greater control over the extent to which the secondary flow passage(s) are open when the valve rotor260is in the thermal management regime.

In some arrangements, it may be desirable to position the second recesses258a,258bsuch that the thin end is more directly exposed to the inlet port when the valve rotor260is in the thermal management regime. In such a configuration, the thin end can be used to gradually open the secondary flow passage(s) when it is desirable to bleed some exhaust gas through the bypass port.

In other arrangements, it may be desirable to position the second recesses258a,258bsuch that the wide end is more directly exposed to the inlet port when the valve rotor260is in the thermal management regime. In such a configuration, the wide end can be used to initially open the secondary flow passage(s) to a greater extent than would be afforded by the thin end. Continued rotation of the valve rotor260would then increase, but by a reducing extent (or at a reducing rate), the extent to which the secondary flow passage(s) is open.

There are many variations which are possible in view of the above. For example, where the second recesses are of a variable geometry (i.e. with a cross-section which changes with circumferential position e.g. triangular, teardrop-shaped) the second recesses could be oriented such that a thin end of one second recess circumferentially aligns with a wide end of the other second recess. In other words, the two second recesses could be aligned such that their geometries are of opposite orientations. Alternatively, as shown inFIG.11, the geometries may be of the same orientation.

Once again, a cross-section plane C2is indicated and will be discussed in detail below.

FIG.12shows a further embodiment of a valve rotor360. Second recesses358a,358bof the valve rotor360are teardrop-shaped. Teardrop-shaped may otherwise be described as an ellipse with a pointed end, in other words a stretched ellipse.

All of the above description, regarding wide and thin ends, and considerations for orienting the second recesses, is equally applicable to the second recesses358a,358bof the valve rotor360.

A cross-section plane C3is indicated and will be discussed below.

FIG.13shows a further embodiment of a valve rotor460. Second recesses458a,458bof the valve rotor460are shaped like wine glasses (truncated teardrops or funnels). That is to say, the second recesses458a,458bare of a geometry which is substantially semi-circular with a pointed tip. The wine glass shape of the second recesses458a,458bis just one specific example of an arbitrary shape which the second recesses458a,458bmay take.

As with the previous figures, a cross-section plane C4is also indicated.

Given the above discussion regarding the possible geometries of second recess, it will also be appreciated that the second recesses may have dissimilar geometries. That is to say, one of the second recesses may be a first geometry, and the other second recess may be a second geometry. Furthermore, whilst the shapes, or geometries, of the second recesses may be the same, the second recesses may be scaled differently. For example, whilst both second recesses may be generally rectangular, a first of the second recesses may be a first size, and a second of the second recesses may be a second size which differs from the first size.

Moving on toFIGS.14and15, these are part cross-section views of two valve rotors. The part-cross-section view is owing to the fact that the cross-sections shown inFIGS.14and15correspond with the planes defined by C1, C2, C3and C4. In other words, only part of the valve rotors is shown in cross-section, hence a first recess, or first recesses, are not visible in the views illustrated inFIGS.14and15.

Beginning withFIG.14, a valve rotor560is shown in cross-section. The portion of the valve rotor560which is cutaway, i.e. the cross-section portion, is indicated by a hatched line. The non-cross-section portion of the valve rotor560simply shows an end wall546aand spindle544a.

The valve rotor560incorporates a second recess558bwhich is of uniform depth. That is to say, the second recess558bis recessed to a substantially constant depth relative to an outer radius of the valve rotor560. The depth to which the second recess558bis recessed is indicated by D1.

An advantage of the second recess558bbeing of a uniform depth is that the second recess558bmay be easier to manufacture. For example, by way of milling on a multi-axis mill. Furthermore, the uniform depth may be desirable in that the secondary flow passage, defined by the second recess558b, may be opened proportionally to the rotational position of the valve rotor560in use. This may make control of exhaust gas flow using the valve rotor560simpler.

Moving toFIG.15, a valve rotor660is shown in cross-section. Much of the above description, with respect toFIG.14, is also applicable toFIG.15and so, in the interest of brevity, such description is not repeated.

A notable distinction between the valve rotors660and560is that, inFIG.15, the valve rotor660comprises a second recess658bwhich is of a non-uniform depth. That is to say, the depth of the second recess658bvaries substantially continuously circumferentially. This can be seen in the form of the depth of the second recess658bat two circumferential points, as indicated by D2and D3, being different from one another.

It will be appreciated that a non-uniform depth covers a range of different examples. For example, the second recess could have two distinct depths, with a step change therebetween. Alternatively, and as illustrated inFIG.15, the second recess658bmay have a depth which varies substantially continuously about the circumference of the valve rotor660. Where the depth is said to vary substantially continuously about the circumference, it will be appreciated that this is only the case along, or spanning, the second recess. That is to say, where the second recess only occupies a portion of the circumference of the valve rotor, the depth of the second recess clearly only varies within the circumferential limits of the second recess (i.e. the portion of the valve rotor occupied by the second recess).

A non-uniform depth may be desirable because the flow regime exhibited by the valve rotor660may be more accurately controlled. Specifically, it may be desirable to initially open a secondary flow passage, defined by the second recess658b, by a first extent. A second extent of opening of the secondary flow passage, once the valve rotor660has continued to rotate by a given degree, may only be slightly more than the first extent. This could allow for fine tuning of the opening of the secondary flow passage after an initial opening has occurred. Put another way, the extent to which the secondary flow passage is opened may not be directly proportional to the rotational position of the valve rotor660. In other words, continued rotation of the valve rotor660may continue to open the secondary flow passage, but to a decreasing extent.

The reverse of the above arrangement is also considered, whereby it may be desirable to initially only slightly open the secondary flow passage, and wherein continued rotation of the valve rotor660opens the secondary flow passage to an increasing extent. In particular, the difference in the extent to which the secondary flow passage opens, for given increments of rotation, may increase with rotation of the valve rotor660.

A non-uniform depth of second recess may also be desirable for reasons of simpler manufacture. For example, a second recess could be manufactured in a single milling process in which, with the valve rotor held in position, the tool removes a plane of material. Given the rotary nature of the valve rotor, the removal of a plane of material could form a second recess having a non-uniform depth which is continuously circumferentially variable.

Where the second recess is of a non-uniform depth, there may be a shallow end and a deep end. The shallow end662and deep end664are indicated on the second recess658bof the valve rotor660.

The above discussion, regarding whether it is desirable to initially open the secondary flow passage by a relatively large or a relatively small extent, depends at least in part upon the orientation of the shallow and deep ends662,664of the second recess658b. In other words, where it is desirable to initially open the secondary flow passage to a greater extent, the deep end664may be more directly exposed to the inlet port when the valve is in a thermal management regime (the regime shown inFIG.9). Where it is desirable to initially open the secondary flow passage to a lesser extent, the shallow end662may be more directly exposed to the inlet port when the valve is in a thermal management regime.

It will be appreciated that the uniform or non-uniform depths of second recesses, as shown inFIGS.14and15, can apply to any of the geometries illustrated inFIGS.10-13. Furthermore, the uniform or non-uniform depths are equally applicable to a variety of other geometries, as will be appreciated by the skilled person.

As discussed above, it may be desirable to manipulate the geometry, orientation of the geometry, depth, orientation of the deep/shallow ends of one or more second recesses. This may be for reasons of ease of manufacture and/or control of the extent of the opening of the secondary flow passage. Where two second recesses are present, a further criterion which can be adjusted is that of a circumferential offset between the recesses. Adjustment of the circumferential offset, as well as the other aforementioned variables, may mean that the second recesses, and so secondary flow passages, open at different rotational positions of the valve rotor.

For greater control, and where a variable geometry of second recess is used, the depth of the second recess can also be made non-uniform. Furthermore, where there are two or more second recesses, the circumferential offset, geometries, depths, uniformity of the depths and/or orientations (of both geometry and depths) can be varied accordingly between the two second recesses. Alternatively, the second recesses may be a pair of like second recesses, which are of substantially the same geometry, depth and orientation.

The primary flow passage may be described as a main passage. The secondary flow passage may otherwise be described as a bleed passage. The second recess58may otherwise be described as a circumferential recess.

The above-described disclosure is particularly useful in reducing NOx (nitrous oxide) emissions. However, it will be appreciated that the disclosure can assist in reducing a variety of different types of emissions. This is owing to the ability to increase the temperature of exhaust gas flowing to the exhaust aftertreatment system.

In a preferred arrangement the exhaust aftertreatment system comprises a reductant and a catalyst. The catalysis is influenced by the exhaust gas temperature. At low engine loads and power, the exhaust gas temperature may be low and the effectiveness of the catalysis may be reduced as a result thereof. For simplicity, durability and packaging reasons, a catalytic NOx converter may be positioned downstream of the turbine. The turbine relies on an expansion process to generate power (to drive the compressor when the turbine forms part of a turbocharger). The expansion process further reduces the exhaust gas temperature.

Managing, or adjusting, the temperature of exhaust gas which flows via the bypass port30cto the exhaust aftertreatment system may be referred to as “thermal management”.

In preferred embodiments, the valve rotor40is moveable about the valve axis A1in order to selectively open and close the primary flow passage whilst the secondary flow passage remains open. In other words, this is the modulation functionality described above. The modulation allows the back pressure to be adjusted, to lessen any reduction in fuel economy, whilst providing a flow of exhaust gas, at an increased temperature, to the exhaust aftertreatment system through the bypass port30c.

Where a plurality of second recesses are present, they may have one or more of the same geometry, depth, volume and circumferential position. Alternatively, one or more of these criteria may be different between the plurality of second recesses (e.g. relative to one another, if there are two second recesses).

One second recess may be present, or a plurality of second recesses may be present. The plurality of second recesses may be two or more second recesses.

The disclosure provides a device which functions like a conventional wastegate/turbine bypass/engine braking valve, but which also allows a full bypass of the turbine to provide higher temperature exhaust gas to the exhaust aftertreatment system.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that fall within the scope of the disclosures as defined in the claims are desired to be protected.

In relation to the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim.

Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the disclosure set out herein are also applicable to any other aspects of the disclosure, where appropriate.