Adapter

The present invention relates to an adapter for an outlet of a turbine, and in particular to an adapter for an outlet of a turbine in which the adapter comprises a diffuser.

Turbines are machines which convert the potential energy of a fluid into mechanical work. Turbines comprise a turbine wheel and a turbine housing defining a turbine inlet and a turbine outlet. In use, fluid enters the turbine through the turbine inlet, where it is passed to the turbine wheel. The fluid impinges upon one or more blades defined by the turbine wheel, thus exerting a force upon the turbine wheel causing the turbine wheel to spin. Once the fluid has travelled through the turbine wheel, it exits the turbine via the turbine outlet. It is known to provide a bypass passage configured to permit fluid flow from the turbine inlet to the turbine outlet without passing through the turbine wheel. Such bypass passages are typically fitted with a valve, known as a wastegate, configured to permit or prevent flow through the bypass passage.

Wastegated turbines typically comprise an adapter mounted to an outlet of the turbine housing. The turbine outlet typically comprises a turbine wheel portion for receiving fluid from the turbine wheel and a wastegate portion for receiving fluid from the bypass passage. The wastegate portion is normally positioned immediately adjacent to the turbine wheel portion. The adapter functions as an end cap which forces the fluid exiting the wastegate to merge with the fluid exiting the turbine wheel in the region immediately downstream of the turbine wheel. Typically, the fluid exiting the wastegate and the fluid exiting the turbine wheel are discharged into a common plenum formed by the adapter immediately downstream of the wastegate and the turbine wheel. Such adapters provide the advantage that they are relatively compact and cheap to manufacture. However, the region where the two fluid streams merge often becomes highly turbulent. The resulting turbulence often acts as a barrier that restricts the flow of the merged fluid stream. This results in increased fluid pressure downstream of the turbine wheel and reduces the efficiency of the turbine.

Some turbines comprise a diffuser positioned at the turbine outlet, downstream of the turbine wheel. Such a diffuser defines a passage which widens as the fluid travels further downstream of the turbine outlet. As the passage widens the velocity of the fluid in the diffuser will decrease resulting in a corresponding increase in pressure of the

fluid in the diffuser. This is advantageous for example if the exhausted fluid is fed to further downstream components, such as a secondary turbine or an exhaust gas aftertreatment system. In such cases, the pressure at the outlet of the diffuser is determined by the downstream components. The pressure increase provided by the diffuser therefore results in a decrease in pressure at the outlet of the turbine wheel. As a result, the difference in pressure across the turbine wheel is increased and therefore more energy can be extracted from the fluid, thus increasing the efficiency of the turbine.

It is known to provide a turbine having both a wastegate and a diffuser. However, as noted above, merging of the fluid exiting the wastegate and the fluid exiting the turbine wheel downstream of the turbine wheel causes turbulence that often results in an increase in pressure. To mitigate this problem, it is known to provide an adapter that separates the fluid exiting the wastegate from the fluid exiting the turbine wheel until both have passed downstream of the diffuser. In such arrangements the diffuser is typically suspended within the adapter by one or more struts so as to divide the adapter into a central passageway and an outer annular passageway. The central passageway receives fluid from the turbine wheel, and the annular passageway receives exhaust gasses from the wastegate. However, such configurations are generally bulky, which may be detrimental in applications where spatial constraints are tight (such as within a vehicle). Furthermore, the geometry of such a diffuser is relatively complex, and therefore the diffusers are more costly to manufacture.

It is therefore an object of the invention to provide an improved turbine adapter which is more compact and less costly to manufacture. It is a further object of the invention to provide an improved turbine adapter which obviates or mitigates one or more of the problems identified above. It is a further object of the invention to provide an alternative turbine adapter.

According to a first aspect of the invention there is provided an adapter for an outlet of a turbine having a wastegate, the adapter comprising: a primary conduit configured to receive fluid that has passed through a turbine wheel of the turbine; and a secondary conduit configured to receive fluid that has passed through the wastegate; wherein the primary conduit further comprises a diffuser configured to decelerate fluid as it moves away from the turbine wheel, and a port configured to deliver fluid from the secondary conduit to the primary conduit; and wherein the port is positioned downstream of the diffuser.

By“adapter” it is meant a housing for containing fluid that is configured to connect to an outlet of a turbine, such as for example the outlet of a turbine housing. By“conduit” it is meant a ducting or other enclosed space having an inlet for receiving fluid and an outlet for discharging fluid. The term“downstream” refers to the direction of travel of fluid within the primary and/or secondary conduits under normal operating conditions (for example, in a direction from an inlet of the primary and/or secondary conduits to an outlet of the primary and/or secondary conduits). The term“port” is intended to mean an opening or orifice capable of providing fluid flow communication between the primary conduit and the secondary conduit. The term“diffuser” means a portion of the primary conduit which increases in cross-sectional area relative to the direction of travel of the fluid received from the turbine wheel. The diffuser imparts a decelerating force upon the fluid within the primary conduit due to the Bernoulli Effect. The fluid which has passed through the turbine wheel may be referred to as the turbine flow and the fluid which has passed through the wastegate may be referred to as the bypass flow. The term “downstream of the diffuser” is intended to mean that the port is positioned downstream of the point at which the diffuser defines its maximum cross-sectional area. That is to say, the port does not overlap with or form part of the diffuser, and is positioned at a point in the flow after the diffuser has decelerated the fluid.

Because the port is positioned downstream of the diffuser, the presence of the port does not interfere with the turbine flow as it passes through the diffuser. As such, the diffuser is able to impart the maximum amount of deceleration upon the turbine flow before the turbine flow is subjected to any other influences. This is particularly advantageous, for example, when the wastegate is closed. In such circumstances, no fluid passes through the secondary conduit and there is no bypass flow. The secondary conduit acts as plenum which contains generally stationary fluid. When the turbine flow passes the port, the turbine flow will interfere with the stationary fluid in the secondary conduit. However, because the port is positioned downstream of the diffuser, the interference between the stationary fluid in the secondary conduit and the turbine flow does not affect the ability of the diffuser to decelerate the turbine flow (since the turbine flow has already been decelerated). Furthermore, when the wastegate is open, the turbine flow and the bypass flow will merge downstream of the port. Merging of the

turbine flow and bypass flow will cause interference between the two flows. However, because the port is positioned downstream of the diffuser, such interference only occurs after the turbine flow has been decelerated by the diffuser. As such, the introduction of the bypass flow to the turbine flow does not detrimentally affect the diffuser.

Furthermore, the use of a port ensures that the primary conduit connects to the secondary conduit at a single concentrated location, for example on one side of the primary conduit. As such, the geometry of the adapter is relatively compact, thus making the adapter easier to accommodate for applications with tight spatial constraints, such as within vehicle engines. By contrast, in prior art adapters it is known to merge the bypass flow to the turbine flow using an annular opening surrounding a diffuser. However, such arrangements more costly to manufacture are not suitable for applications with tight spatial constraints.

The primary conduit may define a primary flow axis and the secondary conduit defines a secondary flow axis, and wherein, at the port, the secondary flow axis is inclined at an acute angle relative to the primary flow axis. By“flow axis” it is meant the centreline of a conduit. That is to say, the flow axis is the line which follows the centre of the primary or secondary conduits long the entire length of the conduit. For example, for a conduit which is a straight pipe, the flow axis of the conduit will be the central axis of the pipe. However, for non-straight conduits the flow axis will bend in conformance with the shape of the conduit. The incline between the secondary flow axis and the primary flow axis refers to the smallest angle subtended between the primary flow axis and the secondary flow axis at the port. This angle may alternatively be referred to as the “confluence angle”. By“acute angle” it is meant an angle less than 90 °.

When the wastegate is open, the bypass flow and the turbine flow will merge at the port. Because the confluence angle is an acute angle, the turbine flow and the bypass flow will have vector components of velocity which act in the same direction. As such, the turbine flow and the bypass flow are encouraged to merge. By merging the turbine flow and the bypass flow in this manner, turbulence can be reduced and the merged flow is less likely to cause any restrictions within the primary conduit.

At the port, the secondary axis may be inclined relative to the primary flow axis at an angle in the range of around 35 ° to around 55 °, in the range of around 40 ° to around 50 ° or at an angle of around 45 °. If the confluence angle is too high, merging of the bypass flow and the turbine flow may cause turbulence which acts to restrict the flow of fluid through the adapter. If the flow becomes too restricted, the deceleration provided by the diffuser will be reduced or cancelled entirely. However, when the confluence angle is reduced the size of the port will increase. For example, typically the shape of the port is determined by projecting the cross-section of the secondary conduit onto the primary conduit at the confluence angle. The larger the area of the port, the more interference the port will cause with the turbine flow when the wastegate is closed, and the larger the primary conduit needs to be to accommodate the port area. It has been found that when the confluence angle is in the range of around 35 ° to around 55“the confluence angle is shallow enough to encourage the bypass flow and the turbine flow to merge with little turbulence, but is steep enough to ensure that the port is not too large.

The adapter may comprise an outer wall defining a generally hollow interior and a dividing wall extending across at least part of the hollow interior, and wherein the dividing wall separates the primary conduit from the secondary conduit. By“outer wall” it is meant a wall delimiting the outermost boundary of the adapter. The outer wall is the wall seen by the user from the exterior of the adapter, and at least partially defines the geometry of the primary and secondary conduits. By“dividing wall” it is meant a wall extending across at least part of the interior of the adapter. Because a dividing wall is used to separate the primary conduit from the secondary conduit, the adapter is more compact. By contrast, without the dividing wall the primary conduit and the secondary conduit would each require respective outer walls. This would increase the overall size of the adapter, and make the adapter more difficult and costly to manufacture.

The adapter may be formed as a single integral body. By“single integral body” it is meant that the adapter is manufactured as a single piece. The adapter may be manufactured, for example, by casting and/or machining. When the adapter is made from a single body, the adapter is cheaper and easier to manufacture and will have increased mechanical strength to resist vibrations.

The primary conduit may define a primary inlet and the secondary conduit defines a secondary inlet, the primary inlet and the secondary inlet being positioned at a first end of the adapter. Because the primary and secondary inlets are both positioned at the first end of the adapter, adapter is more compact and is easy to manufacture. Furthermore, such an adapter will be suitable for use with turbines in which the wastegate is positioned adjacent to the outlet of the turbine wheel, which is beneficial for turbochargers for internal combustion engines.

The adapter may comprise a flange configured to seal the adapter against a housing of the turbine at the outlet of the turbine. When the adapter is sealed against the turbine housing this ensures that all of the turbine flow is directed into the primary conduit and all of the bypass flow is directed into the secondary conduit without leakage. Where the adapter is used in conjunction with an internal combustion engine, if any leakage were to occur, this could result in exhaust gases escaping to atmosphere without passing through the exhaust gas aftertreatment system, which would be damaging to the environment and potentially cause the adapter to fail regulatory tests.

The primary conduit may define an outlet, and wherein the outlet is positioned at a second end of the adapter opposite to the first end. By“opposite” it is meant that the outlet is positioned at a terminal end of the adapter which is a different end of the adapter to the first end of the adapter. As such, the term“opposite” is not intended to imply that there is a symmetrical relationship between the first end and the second end of the adapter.

The primary conduit may define a generally linear flow axis. The flow axis may be the primary flow axis. By“generally linear” it is meant that the primary conduit extends in a substantially straight line, along a single axis. As such, the primary conduit does not comprise any bends which would change the overall direction of the bulk flow through the primary conduit. The primary conduit is therefore generally straight. Because the primary conduit is straight, the primary conduit does not comprise any bends which would change the overall flow direction of the turbine flow. As such, frictional losses associated with bent pipe sections are minimised.

The primary conduit may define a bent flow axis. The flow axis may be the primary flow axis. By“bent flow axis” it is meant an axis that deviates from a straight line. A bent flow axis therefore comprises one or more changes in direction. When the primary conduit defines comprises a bent flow axis, the primary conduit is able to direct the turbine flow around complex geometries. This is particularly advantageous when the adapter is for use in applications where space is tight, such as for example within a vehicle engine housing.

The bent flow axis may comprise a right angled bend. The secondary conduit may define a first bend parallel to the bent flow axis of the primary conduit, and a second bend inclined towards the primary conduit. In such arrangements, the secondary conduit will follow the path of the primary conduit before merging the bypass flow with the turbine flow. Because the secondary conduit follows the path of the primary conduit, the adapter can be made more compact.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a cross-section of a turbocharger according to the prior art;

Figure 2 is a cross-sectional view of a portion of a further known turbocharger comprising a wastegate;

Figure 3 is a cross-sectional view of an adapter according to a first embodiment of the present invention, configured for use with the turbocharger of Figure 2;

Figure 4 is an external side view of the adapter of Figure 3;

Figure 5 is a plan view of a first end of the adapter of Figure 3;

Figure 6 is an external side view of an adapter according to a second embodiment of the present invention, configured for use with the turbocharger of Figure 2; and

Figure 7 is a plan view of a first end of the adapter of Figure 6.

Like reference numerals are used to refer to equivalent features throughout the description and figures.

Figure 1 shows a cross-section of a known turbocharger 2. The turbocharger 2 comprises a compressor 4, a turbine 6 and a bearing housing 7. The compressor 4 comprises a compressor inlet 8, a compressor wheel 10, a compressor housing 12, and a compressor outlet 14. The turbine 6 comprises a turbine inlet 16, a turbine wheel 18, a turbine housing 20 and a turbine outlet 22. The bearing housing 7 comprises bearings 26 which support a shaft 24 for rotation. The compressor wheel 10 and the turbine wheel 18 are fixedly mounted to the shaft 24 such that that compressor wheel 10 and the turbine wheel 18 rotate in unison.

During use, rotation of the compressor wheel 10 causes air to enter the compressor inlet 8. The air passes through the compressor wheel 10 and into a compressor volute 28 defined by the compressor housing 12. Due to the kinetic energy imparted on the incoming air by the compressor wheel 10, the air in the compressor volute 28 is at a higher pressure than the air entering the compressor inlet 8. The compressed air exits the compressor 4 via the compressor outlet 14 where it is delivered to an internal combustion engine (not shown). In some embodiments, the air passes through a heat exchanger to cool the air before it arrives at the internal combustion engine. Fuel is mixed with the air and the fuel-air mixture is combusted within the internal combustion engine. Due to the increased pressure of the air entering the internal combustion engine, a greater mass of oxygen is available for combustion and therefore more power can be produced by the internal combustion engine. The exhaust gases from the internal combustion engine are then passed to the turbine 6. The exhaust gases enter the turbine inlet 16 and pass into a turbine volute 30 defined by the turbine housing 20. The exhaust gases impinge upon one or more vanes 31 of the turbine wheel 18 which causes rotation of the turbine wheel 18 about a turbocharger axis 32. Rotation of the turbine wheel 18 drives rotation of the shaft 24 and the compressor wheel 10, thus driving the compressor 4.

The turbine 6 further comprises a diffuser 34 which is defined by a tapered wall 36 of the turbine housing 20 at the turbine outlet 22. The cross-sectional area of the diffuser 34 in a plane normal to the turbocharger axis 32 increases in a direction axially away from the turbine wheel 18. This causes the velocity of the exhaust gases exiting the turbine 6 to reduce and the pressure of the exhaust gases to increase (in accordance with the Bernoulli Effect). The outlet of the diffuser 34 is connected to an exhaust gas aftertreatment system (not shown) which will determine the pressure of the exhaust gases at the outlet of the diffuser 34. The presence of the diffuser 34 therefore has the effect of reducing the pressure of the exhaust gases at the exit of the turbine wheel 18. This increases the pressure difference between the turbine inlet 16 and the turbine outlet 22, thus increasing the amount of energy extracted from the exhaust gases and improving the efficiency of the turbine 6.

Figure 2 shows a further known turbocharger 2. The turbine 6 of the turbocharger 2 comprises a wastegate 38 including a wastegate valve 40 and a valve shaft 42. The turbine housing 20 comprises a divider 33 which separates the turbine outlet 22 into a turbine wheel portion 22a and a wastegate portion 22b. The turbine housing 20 further defines a bypass passage 46 which passes from the turbine volute 30 to the wastegate portion 22b of the turbine outlet 22. The turbine housing 20 comprises an end face 50 which is configured for mating against a diffuser (not shown). The end face 50 comprises a number of mounting holes 52 which are configured to receive bolts so as to hold the diffuser against the turbine housing 20.

The wastegate valve 40 defines a closed position in which the wastegate valve 40 bears against the turbine housing 20 to cover the bypass passage 46 and an open position in which the wastegate valve 40 does not contact the turbine housing 20. During use, an actuating member (not shown) exerts a rotational force upon the valve shaft 42 to move the wastegate valve 40 between the open and closed positions. When the wastegate valve 40 is in the closed position, exhaust gases are prevented from passing through the bypass passage 46. As such, all exhaust gases are made to flow through the turbine wheel 18. When the wastegate valve 40 is in the open position, some of the exhaust gas can flow from the turbine volute 30 directly to the turbine outlet 22 via the bypass passage 46 without passing through the turbine wheel 18. Because the gas passing through the bypass passage 46 does not impinge upon the turbine wheel 18, the amount of energy absorbed by the turbine wheel 18 from the exhaust gas decreases. The speed of rotation of the turbine wheel 18 reduces and therefore compression of the inlet air achieved by the compressor 4 is also reduced. As such, actuation of the wastegate valve 40 can be used to ensure the pressure increase produced by the compressor 4 is within acceptable levels for different engine operating conditions.

Figure 3 shows a cross-sectional view of a first embodiment of an adapter 54 according to the present invention, and Figure 4 shows an exterior view of the adapter 54 of Figure 3. Referring to Figure 3, the adapter 54 comprises an outer wall 56 defining a generally hollow interior. The adapter 54 further comprises a dividing wall 58 which separates the interior into a primary conduit 60 and a secondary conduit 62. The primary conduit 60 is configured to receive exhaust gases from the turbine wheel 18 and the secondary conduit 62 is configured to receive exhaust gases from the wastegate 38. The primary conduit 60 defines a primary inlet 64 and the secondary conduit 62 defines a secondary inlet 66. The exhaust gases entering the primary conduit 60 via the primary inlet 64 have passed through the turbine wheel 18 and are therefore referred to as the“turbine flow”. The exhaust gases entering the secondary conduit 62 via the secondary inlet 66 have bypassed the turbine wheel 18 through the wastegate 38, and are therefore referred to as the“bypass flow”. However, it will be appreciated that the bypass flow occurs only when the wastegate valve 40 is opened. When the wastegate valve 40 is closed, only the turbine flow will pass through the adapter 54.

The primary inlet 64 and the secondary inlet 66 are positioned at a first end 68 of the adapter 54. The first end 68 comprises a mounting flange 69 configured to abut the end face 50 of the turbine housing 20. The mounting flange 69 defines a plurality of through holes 71 (see Figure 5) which are aligned with the mounting holes 52 of the turbine housing 20. During use, adapter 54 is mounted against the turbine housing 20 so that the primary inlet 64 is aligned with the turbine wheel portion 22a of the turbine outlet 22 and the secondary inlet 66 is aligned with the wastegate portion 22b of the turbine outlet 22. The dividing wall 58 of the adapter 54 is further aligned with the divider 33 of the turbine housing 20 so as to separate the bypass flow from the turbine flow. In order to secure the adapter 24 to the turbine housing, during use bolts (not shown) are passed through the through holes 71 of the adapter 54 and are received by the mounting holes 52. A gasket (not shown) may further be provided to prevent leakage of exhaust gases at the interface between the adapter 54 and the turbine housing 20. The gasket is positioned between the mounting flange 69 of the adapter 54 and end face 50 the turbine housing 20, the gasket being compressed between the mounting flange 69 and the end face 50 under the action of the bolts so as to form a fluid-tight seal.

The primary conduit 60 further comprises an outlet 70 positioned at a second end 72 of the adapter 54, opposite the first end 68. The outlet 70 is typically connected to a downstream component such as an exhaust throttle valve or an exhaust gas aftertreatment system (not shown). The outer wall 56 and the dividing wall 58 define a port 74 therebetween which provides fluid flow communication between the primary conduit 60 and the secondary conduit 62. The port 74 acts as an outlet to the secondary conduit 62 to deliver exhaust gases from the secondary conduit 62 to the primary conduit 60. During use, exhaust gases are received at the first end 68 of the adapter 54 by the primary inlet 64 and the secondary inlet 66, and are discharged at the second end 72 by the outlet 70.

The shape of the port 74 is determined by the geometry of the primary conduit 60 and the secondary conduit 62 at the point where the primary conduit 60 and secondary conduit 62 meet. The port 74 is typically a projection of the cross-section of the secondary conduit 62 onto the primary conduit 60. However, it will be appreciated that the port 74 may define substantially any suitable geometry for permitting fluid flow communication from the secondary conduit 62 to the primary conduit 60. Because of the port 74, the secondary conduit 62 connects to the primary conduit 60 only on one side of the primary conduit 60. As such, the port 74 merges the bypass flow and the turbine flow at a single concentrated location. The geometry of the adapter 54 is therefore relatively compact, thus making the adapter 54 easier to accommodate for applications with tight spatial constraints, such as within vehicle engines.

The dividing wall 58 extends at least partially across the interior of the adapter 54 to separate the primary conduit 60 from the secondary conduit 62 upstream of the port 74. The dividing wall 58 therefore allows the adapter 54 to be more compact. Furthermore, the adapter 54 may be manufactured as a single integral body. Because the adapter 54 is a single body, the adapter 54 is easier and more economical to manufacture. However, it will be appreciated that in alternative embodiments of the invention, the adapter 54 could be composed of a plurality of mechanically separate components. For example, the primary conduit 60 and the secondary conduit 62 may be manufactured as separate pieces of piping that are joined at the port 74.

The adapter 54 described above is preferably composed of ductile cast iron. However, it will be appreciated that the adapter 54 may be composed of substantially any

material suitable for the environment within which the adapter 54 is to be used. For example, in the present embodiment the adapter 54 is for use within a turbocharger 2. Therefore, the material of the adapter 54 must be able to withstand high temperature exhaust gases and mechanical vibrations generated by the internal combustion engine. Other suitable materials include, for example high temperature capable alloys of iron or steel, including Inconel. The adapter 54 may be manufactured using any suitable method, such as for example by casting and/or machining.

The primary conduit 60 is generally tubular and comprises a diffuser 76 and a pipe section 78 which are defined by the outer wall 56 and dividing wall 58. The diffuser 76 extends from the primary inlet 64 and connects to the pipe section 78. The diffuser 76 has a cross-sectional area which increases in the direction of travel of the exhaust gases along the primary conduit 60 (i.e. from the first end 68 to the second end 72 of the adapter 54). The diffuser 76 is generally frusto-conical in shape, such that the diffuser 76 has a narrower diameter at the primary inlet 60 than the pipe section 78. The portions of the outer wall 56 and dividing wall 58 which define the diffuser 76 are tapered relative to a longitudinal centreline of the diffuser 76 at an angle within the range of about 5 ° to about 10 °, and preferably about 7 °. Larger taper angles result in lower resistance to flow due to fluid friction, but are more likely to cause flow separation (especially at high flow rates). Smaller taper angles reduce the likelihood of flow separation but increase fluid friction. Furthermore, smaller taper angles result in a less compact adapter 54 because the length of the diffuser 76 must be increased. It has been found that taper angles within the range above provide sufficient increase in pressure of the turbine flow whilst ensuring the adapter 54 remains compact, with a taper angle of 7 ° being the most optimised taper angle. However, it will be appreciated that in alternative embodiments substantially any suitable taper angle can be used.

The cross-section of the primary conduit 60 is generally circular so that the primary inlet 64 matches the shape of the turbine wheel portion 22a of the turbine outlet 22. In the present embodiment, the primary inlet 64 defines a diameter of approximately 45 mm, however the diameter of the primary inlet 64 may be varied to match the size of the turbine wheel 18. Furthermore, it will be appreciated that in alternative embodiments the cross-section of the primary conduit 60 may be substantially any suitable shape. For example, the cross-section of the primary conduit 60 may be quadrilateral. Furthermore, the cross-section of the primary conduit 60 may change

shape between the primary inlet 64 and the outlet 70. For example, the primary inlet 64 may be generally circular and the outlet 70 may be quadrilateral.

It will be appreciated that the diffuser 76 does not need to be precisely frusto-conical and, in practice, may include one or more distortions which depart from the frusto-conical shape. For example, as shown in Figure 4, the outer wall 56 may comprise one or more depressions 77 which are provided to permit a bolt to be passed into an adjacent through-hole 71. In order for the diffuser 76 to function correctly all that is required is that the cross-sectional area of the diffuser 76 increases from the primary inlet 64 to the point at which the diffuser 76 joins the pipe section 78. Preferably, the change in cross-sectional area should be smooth so as to avoid the turbulence generated by the presence of sharp edges.

The pipe section 78 of the adapter 54 defines a constant cross-sectional area in the direction of travel of the exhaust gases along the primary conduit 60. In the present embodiment, the diameter of the pipe section 78 is approximately 58 mm. The diameter of the pipe section 78 may be varied in dependence upon the desired taper angle of the diffuser 76. Alternatively, the diameter of the pipe section 78 may be sized to match that of any downstream components (e.g. exhaust throttle valves, aftertreatment piping etc.), and therefore the taper angle may be varied in dependence upon the size of the downstream components.

The port 74 connects the secondary conduit 62 to the pipe section 78 of the primary conduit 60. The port 74 is positioned downstream of the diffuser 76, such that merging of the turbine and bypass flows occurs downstream of the diffuser 76. During use, when the wastegate valve 40 is closed there is no flow through the secondary conduit 62. As such, the secondary conduit 62 provides a relatively large plenum for the containment of stagnant exhaust gases. The additional fluid capacity provided by the secondary conduit 62 absorbs fluctuations in pressure in the region immediately downstream of the wastegate valve 40 and helps to reduce the likelihood of wastegate “flutter” (a condition in which the pressure downstream of a wastegate valve causes the valve to rattle, which may occur during opening or closing of the valve). As the turbine flow travels along the primary conduit 60 and past the port 74, the turbine flow will be disturbed by the capacity provided by the secondary conduit 62. However, because the port 74 is positioned downstream of the diffuser 76, the diffuser 76 is able to fully decelerate the turbine flow before the turbine flow is disturbed by the presence of the secondary conduit 62. That is to say, by displacing the point of confluence between turbine flow in the primary conduit 60 and bypass flow in the secondary conduit 62 downstream of the diffuser 76, the turbine flow can obtain the full benefit of the diffuser 76 before it is disturbed by stagnant exhaust gases, bypass flow from the secondary conduit 62, or the geometry of the port 74 itself (for example, by the edge of the dividing wall 58).

With reference to Figure 3, the primary conduit 60 defines a primary flow axis 80. The primary flow axis 80 is the centreline of the primary conduit 60 between the primary inlet 64 and the outlet 70. Likewise, the secondary conduit 62 defines a secondary flow axis 82 which is the centreline of the secondary conduit 62 between the secondary inlet 66 and the port 74. In the embodiment shown in Figure 3, the primary conduit 60 extends generally axially, such that the primary flow axis 80 is generally linear. However, the secondary conduit 62 comprises a bend 84 which causes the secondary conduit 62 to merge with the primary conduit 60 at the port 74. As such, the secondary flow axis 82 initially extends linearly from the secondary inlet 66 and then bends inwardly towards the primary flow axis 80.

The primary flow axis 80 and the secondary flow axis 82 define a confluence angle Q therebetween. The confluence angle Q is the relative angle between the primary flow axis 80 and the secondary flow axis 82 at the port 74 (where the primary conduit 60 joins the secondary conduit 62). The confluence angle Q is an acute angle, and is preferably within the range of about 35 ° to about 55 °, more preferably is within the range of about 40 ° to about 50 °, and most preferably is within the range of about 40 ° to about 45 °. In the embodiment shown in Figure 3, the confluence angle Q is 45 °. Increasing the confluence angle Q improves flow through the primary conduit 60 when the wastegate valve 40 is closed, whilst decreasing the confluence angle Q improves the joining of the turbine and bypass flows when the wastegate valve 40 is open. It has been found that a confluence angle within the range of about 35 ° to 55 ° provides a good balance between these two factors. In particular, it has been found that by controlling the confluence angle Q the amount of turbulence produced by merging of the turbine flow and the bypass flow can be adjusted; in most cases the preferred result being a reduction in turbulence by optimisation of the confluence angle Q.

As discussed above, increased turbulence in the region where the turbine flow and the bypass flow meet is known to create a throttling effect on the flow of exhaust gases through the turbine wheel 18. The throttling effect is known to decrease the efficiency of the turbine 6. However, when the confluence angle Q is reduced the turbine flow and the bypass flow will have components of velocity which extend generally in the same direction which helps to avoid turbulence at the port 74. As such, it is preferable if the confluence angle is less than about 55 °.

It will be appreciated that when the confluence angle Q is reduced, the size of the port 74 will increase due to the geometrical intersection between the primary conduit 60 and the secondary conduit 62. However, the size of the port 74 will be limited by the axial extent of the pipe section 78, which in turn will be determined by the overall spatial requirements of the turbine adapter 54 for its application (for example, the available space within an engine compartment of a vehicle). Furthermore, when the size of the port 74 is increased, when the wastegate valve 40 is closed the port 74 will create a greater disturbance on the turbine flow as it passes the port 74, increasing pressure losses and decreasing the efficiency of the turbine 6. As such, it is generally not possible to reduce the confluence angle below around 35 ° or else the adapter 54 would become too large.

Figure 5 shows a plan view of the first end 68 of the adapter 54. As shown in Figure 5, the primary conduit 60 defines a generally circular cross section at the primary inlet 64. The diameter of the primary inlet 64 is sized to match the diameter of the turbine housing 20 at the outlet of the turbine wheel 18. The secondary conduit 62 defines a generally triangular cross-section at the secondary inlet 66. The secondary inlet 66 is shaped so that it is large enough to accommodate the wastegate 38 which sits within the outlet of the turbine housing 20. Referring back to Figure 3, as the bypass flow moves away from the secondary inlet 66 along the secondary conduit 62 and towards the port 74, the secondary conduit 62 converges to define a throat 79. The throat 79 is the part of the secondary conduit 62 which defines the minimum cross-sectional area Athroat in relation to the direction of the bypass flow. The cross-sectional area Athroat of the throat 79 is chosen so that it is about at least three times greater than the cross-sectional area of the bypass passage 46 so as to ensure that the throat 79 does not create any restriction to flow through the secondary conduit 62.

Furthermore, it has been found that when the cross-sectional area Athroat of the throat 79 is about at least three times larger than the cross-sectional area of the bypass passage 46, if the wastegate valve 40 fails (i.e. if it becomes separated from the valve shaft 42) the wastegate valve 40 is able to pass through the throat 79 and out of the outlet 70 of the adapter 54. This prevents the wastegate valve 40 from blocking the secondary conduit 62, which would prevent exhaust gases from bypassing the turbine wheel 18. As such, sizing the throat 79 so that it is sufficiently large enough to allow the wastegate valve 40 to pass through it in the event of failure reduces the risk of the turbine wheel 18 over-speeding.

The outlet 70 of the adapter 54 defines a cross-sectional area Aout relative to the primary flow axis 80. The primary inlet 64 defines a cross-sectional area Aturbine relative to the primary flow axis 80. The cross-sectional areas of the outlet 70 is chosen so that it is greater than or equal to the sum of the cross-sectional area Athroat of the throat 79 of the secondary conduit 62 and the cross-sectional area Aturbine of the primary inlet 64.

Aout— Athroat Aturbine

Because the pipe section 78 has a constant diameter in the embodiment shown in Figures 3 to 5, the cross-sectional area Aout of the outlet 70 will be equal to the cross-sectional area of the downstream end of the diffuser 76. Using the formula above, the cross-sectional area Athroat of the throat 79 is therefore equal to the increase in cross-sectional area of the diffuser 76 between the primary inlet 64 and the pipe section 78. The outlet 70 is therefore large enough to accommodate flow through both the primary conduit 60 and the secondary conduit 62, without causing a restriction when the wastegate valve 40 is open.

Although the primary conduit 60 of the adapter 54 changes in cross-sectional area due to the diffuser 76, it will be appreciated that the direction of the turbine flow through the primary conduit 60 occurs in a linear direction (i.e. along a generally straight line). As such, the primary conduit 60 is generally axially extending. That is to say, the primary conduit 60 does not bend or change direction. Furthermore, starting from the secondary inlet 66, the secondary conduit 62 extends generally parallel to the primary conduit 60 until it reaches the bend 84, at which point the secondary conduit changes direction to force the bypass flow to merge with the turbine flow. Most of the flow along the adapter 54 therefore occurs in the same direction as the primary conduit 54, which is to say in a straight line. This configuration of the adapter 54 may therefore be referred to as a “straight” configuration. When the adapter 54 has a straight configuration, changes in flow direction from the primary inlet 64 and the secondary inlet 66 to the outlet 70 are minimised. This means that frictional pressure losses associated with more complex pipe geometries are reduced.

However, it will be appreciated that the precise spatial configuration of the adapter 54 will depend upon the spatial constraints for the application in which the adapter 54 is to be used. For example, where the adapter 54 is used within a vehicle engine, there may not be sufficient space for the adapter to have a straight configuration. Depending upon the available space, the primary conduit 60 and the secondary conduit 62 may comprise bends or turns in one or more directions so as to connect the inlets 64, 66 to the outlet 70. Furthermore, the spatial constrains may require that the primary inlet 64 and/or the secondary inlet 66 and/or the outlet 70 are oriented in different planes relative to one another.

One such configuration is shown in Figures 6 and 7. In particular, Figure 6 shows an exterior side view of a second embodiment of an adapter 54’ according to the present invention, and Figure 7 shows an exterior top view of the adapter 54’ of Figure 6. The second embodiment of the adapter 54’ differs from the first embodiment in that the first end 68 and the second end 72 of the adapter 54’ are oriented at right angles to one another. That is to say, the plane defined by the primary inlet 64 and the secondary inlet 66 is perpendicular to the plane defined by the outlet 70. In order to provide smooth flow from the first end 68 to the second end 72, the primary conduit 60 and the secondary conduit 62 comprise a right angle turn 86, shown most clearly in Figure 6.

The right angle turn 86 occurs in a plane which is mutually orthogonal to the plane defined by primary and secondary inlets 64, 66 and the plane defined by the outlet 70. That is to say, the right angle turn occurs within the plane of Figure 6. The right angle turn 86 differs from the bend 84 of the secondary conduit 62 in that the right angle turn 86 changes the direction of both the primary conduit 60 and the secondary conduit 62 by the same amount. As such, both the primary and secondary flow axes 80, 82 (now shown) are bent. By contrast, in the first embodiment above only the secondary flow axis 82 comprises a bend and the primary flow axis 80 is straight. The primary conduit 60 and secondary conduit 62 extend generally parallel to one another throughout the right angle turn 86. After the right angle turn 86, the bend 84 of the secondary conduit 62 directs the bypass flow towards the turbine flow and the two flows subsequently merge. The secondary conduit 62 therefore defines a first bend in which the secondary flow axis 82 is generally parallel to the primary flow axis 80, and a second bend in which the secondary flow axis 82 is inclined towards the primary flow axis 80.

It will be appreciated that although the different embodiments of the adapter 54, 54’ have been described above in relation to a turbine 6 of a turbocharger 2, in practice either embodiment of the adapter 54, 54’ could be used with substantially any turbine. For example, either embodiment of the adapter 54, 54’ could be used within a turbine for power generation, such as a steam turbine.

It will be appreciated that the optional features and advantages described above in relation to the first embodiment of the adapter 54 may apply equally to the second adapter 54’.
CLAIMS:

1. An adapter for an outlet of a turbine having a wastegate, the adapter comprising:

a primary conduit configured to receive fluid that has passed through a turbine wheel of the turbine; and

a secondary conduit configured to receive fluid that has passed through the wastegate;

wherein the primary conduit further comprises a diffuser configured to decelerate fluid as it moves away from the turbine wheel, and a port configured to deliver fluid from the secondary conduit to the primary conduit; and wherein the port is positioned downstream of the diffuser.

2. An adapter according to claim 1 , wherein the primary conduit defines a primary flow axis and the secondary conduit defines a secondary flow axis, and wherein, at the port, the secondary flow axis is inclined at an acute angle relative to the primary flow axis.

3. An adapter according to claim 2, wherein, at the port, the secondary axis is inclined relative to the primary flow axis at an angle in the range of around 35 ° to around 55 °.

4. An adapter according to claim 3, wherein, at the port, the secondary axis is inclined relative to the primary flow axis at an angle in the range of around 40 ° to around 50 °.

5. An adapter according to claim 4, wherein, at the port, the secondary axis is inclined relative to the primary flow axis at an angle of around 45 °.

6. An adapter according to any preceding claim, wherein the adapter comprises an outer wall defining a generally hollow interior and a dividing wall extending across at least part of the hollow interior, and wherein the dividing wall separates the primary conduit from the secondary conduit.

7. An adapter according to any preceding claim, wherein the adapter is formed as a single integral body.

8. An adapter according to any preceding claim, wherein the primary conduit defines a primary inlet and the secondary conduit defines a secondary inlet, the primary inlet and the secondary inlet being positioned at a first end of the adapter.

9. An adapter according to claim 8, wherein the adapter comprises a flange configured to seal the adapter against a housing of the turbine at the outlet of the turbine.

10. An adapter according to any preceding claim, wherein the primary conduit defines an outlet, and wherein the outlet is positioned at a second end of the adapter opposite to the first end.

11. An adapter according to any preceding claim, wherein the primary conduit defines a generally linear flow axis.

12. An adapter according to any of claims 1 to 10, wherein the primary conduit defines a bent flow axis.

13. An adapter according to claim 12, wherein the bent flow axis comprises a right angled bend.

14. An adapter according to claim 12 or 13, wherein the secondary conduit defines a first bend parallel to the bent flow axis of the primary conduit, and a second bend inclined towards the primary conduit.