CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase filing under 35 U.S.C. § 371 of International Application No. PCT/GB2018/052995, titled “TURBINE,” filed on Oct. 17, 2018, which claims priority to British Patent Application No. 1717127.3, filed on Oct. 18, 2017, the entire disclosures of which being expressly incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a turbine, and in particular to a turbine having a baffle separating a first outlet portion and a second outlet portion of the turbine.

BACKGROUND

Turbines are used to harness power from a working fluid by converting fluid pressure into rotational motion using a turbine wheel. This rotary motion can be used to do useful work, such as for example by generating electrical power or by powering a compressor within a turbocharger of which the turbine forms part.

Turbochargers are used to increase the pressure of air entering into an internal combustion engine using a turbine wheel and a compressor wheel mounted to a common shaft. Exhaust gasses from the internal combustion engine are passed through the turbine wheel, which causes rotation of the turbine wheel, shaft and compressor wheel. Air is drawn through the compressor wheel and compressed to a boost pressure which is above atmospheric pressure. By providing higher pressure air to the internal combustion engine, more oxygen is available within the internal combustion engine for the combustion of fuel. As such, the turbocharger permits more fuel to be combusted, and hence the internal combustion engine may produce more power.

Turbines, as part of a turbocharger or otherwise, are typically provided with either an axial or radial turbine arrangement. In axial turbine arrangements, a working fluid (such as exhaust gas) passes through the turbine wheel in a direction parallel to the axis of rotation of the turbine wheel. In radial turbine arrangements, the working fluid circulates around the turbine wheel in an inwardly directed spiral, before being deflected by the turbine wheel along a path parallel to the axis of rotation of the turbine wheel.

Radially arranged turbines typically comprise an inlet in the shape of a hollow spiral, referred to as a volute, which is shaped to encourage circulation of the working fluid around the turbine wheel. Some radial turbines are provided with a twin entry arrangement comprising two such volutes arranged to be either side-by-side or radially overlapping. Where such a twin volute turbine is used within a turbocharger, each volute is typically connected to a separate bank of cylinders of an internal combustion engine. Exhaust gasses from each bank of cylinders are fed to one of the inlet volutes by separate exhaust manifolds. The exhaust manifolds may be tuned using pressure wave superposition to provide more efficient flow of exhaust gasses through the exhaust manifolds and inlet volutes. In order to prevent interference between the tuned exhaust gasses in each manifold, the two streams of exhaust gasses are kept separate until they reach the turbine wheel, at which point both streams of exhaust gasses are directed through the turbine wheel.

Some turbines, particularly those used in turbochargers, comprise wastegates which are used to bypass exhaust gasses to a position downstream of the turbine wheel such that the exhaust gasses do not pass through the turbine wheel. Such wastegates are used to reduce the amount of exhaust gas impinging on the turbine wheel so as to regulate the power produced by the turbine wheel. In this manner, detrimental flow conditions in the turbocharger compressor, such as compressor surge, can be avoided.

It is known to provide a twin volute radial turbine with a wastegate, such as of the type disclosed in U.S. Pat. No. 5,046,317. In the case of U.S. Pat. No. 5,046,317, the wastegate is positioned in the outlet of the turbine and comprises a pair of valve members which are configured to selectively cover and uncover a pair of wastegate passages connected to either inlet volute. Depending upon the configuration of the internal combustion engine and the exhaust manifolds, it is common that only one of the exhaust manifolds is pressurised at any one time (i.e. because a cylinder which feeds that manifold has just fired). As such, when the wastegate is opened, pressure pulses from each wastegate passage are able to interfere with the pressure pulses from the other wastegate passage. Any pressure difference between the two passages can result in an impedance to gas flow through the less pressurised passage as the pressure of the pressurised passage is transmitted into region downstream the unpressurised passage. The increased local pressure downstream of the unpressurised passage reduces the velocity of the exhaust gasses travelling through the unpressurised passage, and thus the amount of exhaust gas which can be transmitted through the wastegate overall (i.e. the wastegate efficiency). It is therefore desirable to reduce such interference between the wastegate passages.

SUMMARY

It is an object of the present disclosure to obviate or mitigate at the problems prevalent in the prior art, whether identified herein or elsewhere.

According to a first aspect of the disclosure there is provided a turbine comprising: a turbine housing; a turbine wheel; an inlet upstream of the turbine wheel, the inlet defining a first inlet portion and a second inlet portion; an outlet downstream of the turbine wheel, the outlet defining a first outlet portion and a second outlet portion; and a wastegate arrangement configured to selectively vent exhaust gas from the first inlet portion to the first outlet portion via a first bypass passage, and further configured to selectively vent exhaust gas from the second inlet portion to the second outlet portion via a second bypass passage; wherein the first outlet portion and the second outlet portion are separated by a baffle of the turbine housing.

Because the baffle separates the first outlet portion and the second outlet portion, when the wastegate arrangement is opened, pressure pulses from the first outlet portion must travel around the baffle in order to interfere with the pressure pulses from the second outlet portion. Interference between the pressure pulses in either outlet portion therefore occurs at a distal end of the baffle and not at the points where the first and second bypass passages connect to the first and second outlet portions. It will be appreciated that the distal end of the baffle is defined as the most downstream point of the baffle relative to the flow of fluid through the outlet. As such, this structure prevents pulse wave interference occurring within (or immediately downstream of) the first and second bypass passages themselves, and therefore the corresponding impedance to flow through the first and second bypass passages is reduced. That is to say, by creating a more tortuous path for exhaust gas flow between the first and second bypass passages, the location of any interference between the pressures of the exhaust gasses in the first and second bypass passages is displaced away from the first and second bypass passages themselves. As such, the efficiency of the flow through the first and second bypass passages is increased.

It will be appreciated that the first and second inlet portions are separate portions of the turbine which are positioned upstream of the turbine wheel. The first and second inlet portions may be fully or partially defined by the turbine housing and may include some or all of an exhaust manifold connected to an internal combustion engine.

It will be appreciated that the first and second outlet portions are separate portions of the turbine which are positioned downstream of the turbine wheel. The first and second outlet portions are regions of the turbine outlet which are separated from one another by the baffle. The turbine outlet may comprise additional regions which do not form part of the either the first or second outlet portions. For example, the first and second outlet portions may feed into a common region of the turbine outlet downstream of the first and second outlet portions.

By the term “configured to selectively vent” it will be understood that the wastegate arrangement is configurable between a first state in which gas flow communication between the first and second inlet portions and the first and second outlet portions via the first and second bypass passages is substantially prevented, and a second state in which such gas flow communication is permitted. As such, the wastegate arrangement may comprise one or more valve members configured to selectively block the path of exhaust gasses through the first and second bypass passages.

The baffle may extend in a generally axial direction with respect to a rotational axis of the turbine wheel.

The baffle may be an annular baffle. Where the baffle is annular, the baffle acts to encourage circulation of the exhaust gasses in the first and second outlet portions around the axis of the turbine wheel. As such, at the point immediately downstream of the baffle where the exhaust gasses in the first and second outlet portions are no longer separated by baffle, the exhaust gasses will be circulating around the axis of the turbine wheel in the same direction and at approximately the same speed. As such, detrimental flow effects such as turbulence at a distal end of the baffle are avoided, and the two streams of fluid are smoothly mixed.

The baffle may be arranged concentrically in relation to the turbine wheel and turbine housing. Where the baffle is concentric to the turbine wheel, the circulation of exhaust gasses around the axis of the turbine wheel may be symmetric.

The first bypass passage may be vented to a central region of the baffle, such that the central region of the baffle defines the first outlet portion. It will be appreciated that the term “vented” is intended to mean that the first bypass passage directs exhaust gasses from the first inlet portion and into the central region of the annular baffle.

The central region of the baffle may define a proximal end adjacent to the turbine wheel and a distal end opposite the proximal end and positioned further away from the turbine wheel, and wherein the central region of the baffle is open at both said distal end and said proximal end. As such, the central region may receive exhaust gasses from the turbine wheel and/or first bypass passage and transmit these exhaust gasses to the turbine outlet.

The first bypass passage may be vented to a position at or near the proximal end of the turbine wheel. That is to say, an exit of the first bypass passage may be positioned adjacent to an outlet of the turbine wheel. As such, exhaust gasses from the first bypass passage may enter the first outlet portion at an upstream part of the first outlet portion which is spaced apart from the distal end of the baffle.

The first bypass passage may be configured to direct exhaust gasses into the first outlet portion in a non-radial direction relative to an axis of rotation of the turbine wheel. That is to say, the exhaust gasses may enter the first outlet portion from the first bypass passage in a direction which is inclined relative to the radial direction of the axis of the turbine wheel in a plane which is normal to the axis of the turbine wheel. As such, circulation of the exhaust gasses around the axis of the turbine wheel is induced by the first bypass passage.

The second outlet portion comprises an annular region defined between the baffle and the turbine housing, and wherein the second bypass passage is vented to the annular region. It will be appreciated that the term “vented” is intended to mean that the second bypass passage directs exhaust gasses from the second inlet portion and into the annular region between the exterior of the baffle and the interior of the turbine housing. Furthermore, it will be appreciated the exterior of the baffle is defined by a radially outer surface of the baffle and the interior of the baffle is defined by a radially inner surface of the baffle.

Said annular region may have an upstream end and a downstream end spaced apart from the upstream end, and wherein the annular region is closed at the upstream end and open at the downstream end. That is to say, the annular region may define two ends, once of which is closed and the other of which is open. As such, exhaust gasses may be transmitted through the annular region to the turbine outlet.

The second bypass passage may be vented to the upstream end of the annular region. That is to say, an exit of the second bypass passage may be positioned such that it is spaced apart from the distal end of the baffle and towards the closed end of the annular region.

The second bypass passage may be vented to a position which is spaced apart from the upstream end of the annular region. It will be appreciated that by being spaced apart from the upstream (i.e. closed) end of the second outlet portion, the spacing may be tuned so as to reduce resonance of any pressure pulses present in the second outlet portion. As such, the exit of the second bypass passage is spaced apart from both the closed end of the second outlet portion and the distal end of the baffle. The second bypass passage may be vented to a position equidistant between the ends of the annular region, or may be vented to a position which is further towards one of the upstream or downstream ends of the annular region.

The second bypass passage may be configured to direct exhaust gasses into the second outlet portion in a non-radial direction relative to an axis of rotation of the turbine wheel. That is to say, the exhaust gasses may enter the second outlet portion (e.g. the annular region) from the second bypass passage in a direction which is inclined relative to the radial direction of the axis of the turbine wheel in a plane which is normal to the axis of the turbine wheel. As such, circulation of the exhaust gasses around the axis of the turbine wheel may be induced by the first bypass passage.

The baffle may be formed as an insert separable from the turbine housing. Alternatively, the baffle may be integrally formed with the turbine housing, such as for example by casting or welding. The first inlet portion may comprise a first volute and the second inlet portion may comprise a second volute separate to the first volute. The wastegate arrangement may comprise a first wastegate valve configured to open and close the first bypass passage and a second wastegate valve configured to open and close the second bypass passage. The first and second wastegate valves may be integrally formed with the turbine housing. The first and second wastegate valves may be external to the turbine housing. The turbine may form part of a turbocharger.

