Manufacturing intermediate for a turbine

Abstract

There is provided a manufacturing intermediate for a turbine housing. The manufacturing intermediate being configured for engagement with an abutment portion of a holding device during machining. The manufacturing intermediate comprising a connection portion comprising a connection surface defining a first radius from a central axis. The manufacturing intermediate comprising an inlet portion defining a turbine inlet having two inlet volutes axially separated by a dividing wall, the dividing wall comprising a terminal edge defining a second radius from the central axis. The second radius is smaller than the first radius such that the dividing wall defines an alignment surface configured to abut the abutment portion to align the dividing wall with the abutment portion.

Description

[0001]M&C 30^^^^^^:2^ 1 Manufacturing for a Turbine The present invention relates to a manufacturing intermediate for a turbine housing, in particular a manufacturing intermediate for a turbine housing having two inlet volutes axially separated by a dividing wall. The manufacturing intermediate comprising an alignment surface configured for engagement with an abutment portion of a holding device allows improved alignment between the dividing wall of the turbine housing and the dividing wall of a nozzle ring, thereby improving tolerance, reducing assembly time, and improving efficiency of the turbine. The present invention also relates to a method of engaging a manufacturing intermediate of a turbine housing with an abutment portion of a holding device, a turbine housing, a nozzle ring, and a turbine. Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure (boost pressures). A conventional turbocharger comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to the intake manifold of the engine, thereby increasing engine power. The turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housings. In known turbochargers, the turbine stage comprises a turbine chamber within which the turbine wheel is mounted; a circumferentially extending inlet passageway defined between opposing walls arranged around the turbine chamber; an inlet volute arranged around the inlet passageway; and an outlet passageway extending from the turbine chamber. The passageways and chambers communicate such that pressurised exhaust gas admitted to the inlet volute flows through the inlet passageway to the outlet passageway via the turbine and rotates the turbine wheel. It is also known to improve turbine performance by providing vanes, referred to as nozzle vanes, in the inlet passageway so as to deflect gas flowing through the inlet passageway towards the direction of rotation of the turbine wheel. 69154916-1 M&C 30^^^^^^:2^ 2 Turbines may be of a single-entry or entry type. Single-entry turbines comprise a single inlet volute that typically receives all of the exhaust gas from an internal combustion engine. Multiple-entry turbines comprise more than one volute which typically receive separate streams of exhaust gas from different cylinder banks of an internal combustion engine. One form of multiple-entry turbine is a “twin-entry” turbine in which two volutes extend circumferentially with one another around the turbine axis in angular alignment with one another. In such “twin-entry” turbines, a dividing wall is used to separate the volutes from one another. In multiple-entry turbines, the exhaust gas streams in the different inlet volutes will exhibit transient pressure pulses caused by the separate cylinder banks. Often this means that when a first volute exhibits high pressure an adjacent second volute exhibits low pressure. If the pressure difference between the two volutes is high enough, this will cause exhaust gas from the first (higher pressure) volute to spill over the dividing wall from into the second (lower pressure) volute. The presence of the high pressure gas in the second volute forms a fluid blockage which may impede exhaust gas flow through the second volute during the next exhaust gas cycle and thereby increase the pumping work required by the engine and resulting in engine energy losses. During the next exhaust gas cycle, high pressure gas in the second volute may spill over the dividing wall into the first volute to form a fluid blockage in the first volute. Such fluid interaction between the different volutes is known as “cross-talk”. It is beneficial to keep the inlet flow streams separated from one another until close as possible to the turbine wheel. By keeping the two flows separate until just before the turbine wheel, this increases the relative pressure difference between the two volutes required for cross-talk to occur. However, this requires that the dividing wall is sized so that it extends as close as possible to the turbine wheel in the radial direction. As a result, the dividing wall in a twin-entry turbine housing is often very long in the radial direction and very narrow in the axial direction. Because of this uneven geometry when assembling the turbomachine is it difficult to obtain good alignment between the dividing wall of the turbine housing and the dividing wall of the nozzle ring. It is further difficult, during use, to maintain the alignment between the dividing wall of the nozzle ring and the dividing wall of the turbine housing, due to movement (including rotation) of the nozzle ring. 69154916-1 M&C 30^^^^^^:2^ 3 It is an object of the present invention to machining accuracy so as to provide improved alignment between a nozzle ring dividing wall and a turbine housing dividing wall. It is a further object of the invention to mitigate one or more disadvantages of the prior art whether described herein or elsewhere, and / or to provide an alternative turbine housing. According to a first aspect of the invention there is provided manufacturing intermediate for a turbine housing, the manufacturing intermediate being configured for engagement with an abutment portion of a holding device during machining, the manufacturing intermediate comprising: a connection portion comprising a connection surface defining a first radius from a central axis; an inlet portion defining a turbine inlet having two inlet volutes axially separated by a dividing wall, the dividing wall comprising a terminal edge defining a second radius from the central axis; wherein the second radius is smaller than the first radius such that the dividing wall defines an alignment surface configured to abut the abutment portion to align the dividing wall with the abutment portion. The term “manufacturing intermediate for a turbine housing” encompasses an unfinished turbine housing which, with further manufacturing or machining, results in a complete turbine housing. That is to say, the manufacturing intermediate is a component that is used in the manufacture of a turbine housing and, in particular, is a component that undergoes subsequent machining to arrive at its finished geometry. Such manufacturing intermediates may also be known as ‘blanks’. The term “holding device” may encompass any suitable device for holding a turbine housing, in particular for holding a turbine housing during a machining and / or manufacturing process. The holding device may be a clamp, and the clamp may comprise an abutment portion. The holding device may comprise a chuck, the chuck may have one or more jaws. The jaws of the chuck may define an abutment portion. The term “connection portion” encompasses a part of the manufacturing intermediate that is configured to connect with another component of the turbine, such as for example a heatshield. The connection surface may be revolved around the central 69154916-1 M&C 30^^^^^^:2^ 4 axis. The central axis may be, in a central axis of the manufacturing intermediate. In other words, the central axis may be the central axis of a turbine housing once manufactured. The “first radius” encompasses the innermost radius of the connection surface relative to the central axis. The “second radius” encompasses the innermost radius of the terminal edge of the dividing wall relative to the central axis. The “alignment surface” may be a surface of the dividing wall facing towards the connection portion. That is to say, the alignment surface is accessible from the connection portion side of the manufacturing intermediate. In turbines comprising two inlet volutes separated by a dividing wall, achieving good alignment between the dividing wall of the turbine housing and a dividing wall of a corresponding nozzle ring is often difficult to achieve. This is because the machining process is typically takes its datum from the radially extending surface of the manufacturing intermediate that defines the axial extremity of the nozzle passage furthest from the connection portion (e.g. see surface 214 in Figure 4). Accordingly, the widths of the nozzle passages are toleranced (defined by dimensions, each with their own tolerance) from the axial side of one of the nozzle passages. However, because the precise shape and position of the datum surface itself will vary depending upon casting tolerances, this causes a knock-on effect on the machining dimensions toleranced based upon this datum surface. In particular, this may cause the dividing wall of the housing to become misaligned with the dividing wall of the nozzle ring. However, by providing a manufacturing intermediate that comprises a dividing wall having an alignment surface that is configured to abut the abutment portion the machining datum can be taken from the alignment surface of the dividing wall. Accordingly, the widths of the nozzle passages are toleranced from the dividing wall, thus providing improved alignment between the dividing wall of the housing and the dividing wall of the nozzle ring. Providing improved machining accuracy improves alignment between the turbine housing dividing wall and a nozzle ring dividing wall, which in turn, in use, improves flow into a turbine wheel. If there is misalignment between the turbine housing dividing wall and the nozzle ring dividing wall, there may be a “step” in the inlet flow path from 69154916-1 M&C 30^^^^^^:2^ 5 the inlet volutes to the turbine wheel would reduce the efficiency of the turbine. Further, the improved machining mitigates against crossover (which improves efficiency) due to an increased clearance path around the divider circumference of turbine housing dividing wall. The terminal edge of the dividing wall may comprise an inwardly extending protrusion defining the alignment surface, and wherein the protrusion may define the second radius. That is to say the terminal edge may not have a constant radius from the central axis but instead may vary in dependence upon its azimuth angle relative to a particular reference point, such as for example a tongue of the inlet portion. In particular, the terminal edge may comprise one or more protrusions. The term “protrusion” encompasses an extension of any suitable geometry formed in the dividing wall and extending towards the central axis. The remainder of the dividing wall that does not comprise the protrusion may have a constant radius. Using a protrusion to provide the alignment surface is beneficial at least because such an alignment surface is easily locatable from the connection portion side of the manufacturing intermediate so as to enable engagement with the abutment portion of the holding device. The abutment portion of the holding device can therefore readily locate directly on to the alignment surface. A further advantage is that the inwardly extending protrusion may form an anti-rotation feature. In particular, the inwardly extending protrusion may be received in a corresponding recess of a nozzle ring, so as to prevent the nozzle ring from rotating about the central axis. The protrusion may be provided in any suitable shape to form the anti-rotation feature. The anti-rotation feature may improve efficiency by mitigating seal ring wear related leakage and also by promoting correct alignment of the nozzle ring vanes with the housing tongue (dividing wall). The terminal edge of the dividing wall may define a circumferentially extending base portion having a constant radius from the central axis, and wherein the protrusion may extend radially inward from the base portion. 69154916-1 M&C 30^^^^^^:2^ 6 That is to say, the base portion of the wall is the portion of the dividing wall from which the protrusion extends. The terminal edge of the dividing wall may comprise at least three protrusions spaced apart about the central axis. Providing at least three protrusions is beneficial as it promotes ease of locating one or more abutment portions of the holding device against the alignment surface. The terminal edge of the dividing wall may define exactly three protrusions The at least three protrusions may be unequally distributed about the central axis. That is to say that the circumferential distance between the centroids of adjacent protrusions are not equal. Or in other words, the angle between the centroids of each protrusion and the central axis may not be equal. By the at least three protrusions being unequally distributed the manufacturing intermediate and / or the holding device require correct orientation for the abutment portion to abut the alignment surface. This is advantageous as it promotes correct orientation of the manufacturing intermediate during machining. Further, in some embodiments the distance between the central axis and the radially innermost edge of each protrusion may be different. That is to say the radial distance between the radially innermost edge of a first protrusion and the central axis is different to the radial distance between the radially innermost edge of a second protrusion and the central axis. Similarly, there may be a third protrusion that has a radial distance from its radially innermost edge to the central axis, that is different to the first and second protrusions, or the distance may be the same as either one of the first or second protrusions. When the distance from the radially innermost edges of the protrusions to the central axis are different, it is beneficial because it promotes correct orientation of the manufacturing intermediate during machining. It will be appreciated, that in some embodiments the circumferential distance between the centroids of adjacent protrusions may not equal and the distance between the central axis and the radially innermost edge of each protrusion may be different. 69154916-1 M&C 30^^^^^^:2^ 7 The base portion of the dividing wall may a third radius from the central axis, the third radius may be greater than the second radius. This ensures that the base portion is wider than the connection portion. Accordingly, the nozzle ring may be received within the space defined by the edge of the dividing wall. The ratio of the second radius to the first radius is within the range of between around 0.75 to around 0.95. The alignment surface may be a substantially flat surface lying in a plane substantially normal to the central axis. The alignment surface lying in a plane that is substantially normal to the central axis is advantageous as the surface area that the abutment portion of the holding device can abut is increased, compared to, for example, if the alignment surface lay in a plane that was not substantially normal to the central axis. Thus, the ability of the holding device to hold the manufacturing intermediate during a machining process is improved. However, in alternative embodiments the alignment surface may be angled relative to the central axis. For example, if the manufacturing intermediate is part of a mixed-flow turbine in which the nozzle passages extend both radially and axially, the alignment surface may be angled relative to the central axis by the same extent as the nozzle passages. The terminal edge of the dividing wall may comprise a sealing formation. The term “sealing formation” encompasses substantially any suitable sealing arrangement, including for example mechanical seals and / or fluidic seals. For example, the fluidic sealing formation may comprise a labyrinth seal. In other embodiments, it may comprise a circumferentially extending groove or recess that receives a sealing member, such as an o-ring or the like. The sealing formation mitigates against fluid exhaust gas passing between the two inlet volutes, at the interface between the dividing wall of the manufacturing intermediate and the dividing wall of the nozzle ring. Reducing leakage between the two volutes mitigates against reduction in efficiency of the turbine during use. 69154916-1 M&C 30^^^^^^:2^ 8 The fluidic sealing formation may extend around the entire circumference of the terminal edge of the dividing wall, or may extend around only a portion thereof. The terminal edge of the dividing wall may comprise an inwardly extending protrusion defining the alignment surface, and the protrusion may defines the second radius, and the terminal edge of the dividing wall may comprise a sealing formation, and the sealing formation may extend along at least a part of the protrusion. Additionally, the sealing formation may extend around the entire circumference of the terminal edge of the dividing wall. According to a second aspect of the invention there is provided a method of manufacturing a turbine housing, the method comprising: obtaining a manufacturing intermediate according to any preceding claim; inserting an abutment portion of a holding device into the connection portion; abutting a first surface of the abutment portion against the alignment surface; and abutting a second surface of the abutment portion against the connection surface. Because the second radius is smaller than the first radius, the alignment surface protrudes radially inwardly from the connection surface. Accordingly, it is simply and easy to insert the holding device so as to engage the alignment surface of the manufacturing intermediate with the first surface of the abutment portion of the holding device, and to engage the connection surface of the connection portion with the second surface of the abutment portion of the holding device. A suitable holding device capable of achieving the above may be, for example, a set of radially expandable chuck jaws. The method may comprise machining the manufacturing intermediate. Machining the manufacturing intermediate may include performing at least one turning operation and / or at least one milling operation. 69154916-1 M&C 30^^^^^^:2^ 9 The manufacturing intermediate may an outlet portion defining a turbine outlet, and wherein the step of machining the manufacturing intermediate may include: performing a turning operation to remove material from an end face of the turbine outlet portion until a predetermined axial distance between the end face of the outlet portion and the first surface of the abutment portion is achieved. The pre-determined axial distance between the end face of the outlet portion and the first surface of the abutment portion may be referred to as a set-up dimension. The holding device may comprise a chuck. The chuck may comprise one or more jaws defining the abutment portion. An end surface of each jaw may define the first surface of the abutment portion. A side surface of each jaw may define the second surface of the abutment portion. The method may further comprise: disengaging the holding device from the manufacturing intermediate; engaging the end face of the outlet portion with the holding device; and machining the manufacturing intermediate. The manufacturing intermediate may comprise a turbine wheel chamber portion defining a turbine wheel chamber. The method may further comprise performing a turning operation to machine the turbine wheel chamber portion to a predetermined geometry. In this context “predetermined geometry” comprises substantially any geometric feature that can be produced by machining, including for example, dimension, shape, tolerance, surface finish (i.e. surface roughness), or the like. The manufacturing intermediate may comprise a bearing housing connection portion configured to connect to a bearing housing. The method may further comprise performing a turning operation to machine the bearing housing connection portion to a predetermined geometry. 69154916-1 M&C 30^^^^^^:2^ 10 The inlet portion may comprise an inlet surface. The method may further comprise performing a milling operation to machine the annular inlet surface to a predetermined geometry. The method may further comprise performing a milling operation to machine the connection surface to a predetermined geometry. The method may further comprise performing a milling operation to machine one or more fastener holes into the manufacturing intermediate. The fastening holes, may be threaded bores. The terminal edge of the dividing wall may comprise an inwardly extending protrusion defining the alignment surface, and wherein the protrusion may define the second radius; and wherein the method may further comprise performing a machining operation to remove material from the dividing wall to reduce the size of the protrusion. The method may further comprise performing a machining operation to remove material from the dividing wall so as to remove the alignment surface entirely. According to a third aspect of the invention there is provided a turbine housing for a turbocharger, the turbine housing defining: a connection portion comprising a connection surface defining a first radius from a central axis; an inlet portion defining a turbine inlet having two inlet volutes axially separated by a dividing wall, the dividing wall comprising a terminal edge defining an inwardly extending protrusion; wherein the protrusion defines a second radius smaller than the first radius; and wherein the protrusion is configured to be received by a correspondingly shaped slot of a nozzle ring. This enables the protrusion to be used as an anti-rotation feature preventing rotation of a nozzle ring. The terminal edge of the dividing wall may define a plurality of protrusions. 69154916-1 M&C 30^^^^^^:2^ 11 In particular, the terminal edge of the dividing wall may define at least three protrusions. The plurality of protrusions may be unequally distributed about the central axis. If the turbine housing comprises protrusions that are unequally distributed that are received in corresponding slots of a nozzle ring, the corresponding slots of the nozzle ring will also be unequally distributed about the central axis. This is advantageous as it ensures that the nozzle ring is provided in the correct orientation in the turbine housing. The base portion of the dividing wall may define a third radius from the central axis, the third radius may be greater than the second radius. The terminal edge of the dividing wall may comprise a sealing formation. The sealing formation may extend around the entire circumference of the terminal edge of the dividing wall. According to a fourth aspect of the invention there is provided a nozzle ring for a turbine for a turbocharger, the nozzle ring comprising: an annular nozzle ring dividing wall encircling a central axis; and a plurality of vanes extending from the nozzle ring dividing wall; and wherein the nozzle ring dividing wall comprises an inwardly recessed slot for receiving a protrusion of a turbine dividing wall, the slot being positioned such that the entirety of the slot is located angularly between two adjacent vanes. Nozzle rings are provided in turbochargers to accelerate and guide flow, particularly exhaust gas flow, to a desired angle to the turbine wheel. In use, the nozzle ring dividing wall will be concentric with and axially aligned with the dividing wall of the turbine housing, such that exhaust gas flow from the first and second volutes of a turbine can be guided by the plurality of vanes of the nozzle ring. The term “inwardly recessed slot” comprises any suitable slot or recesses, such that a terminal edge of the nozzle ring, i.e. an outer perimeter of the nozzle ring does not 69154916-1 M&C 30^^^^^^:2^ 12 have a constant radius, measured from axis of the nozzle ring. That is to say, the radius from the central axis of the nozzle ring to an outer surface of the nozzle ring where the inwardly recessed slot is provided is smaller than to a location where no inwardly recessed slot is provided. The inwardly recessed slots being configured to receive a protrusion from a turbine is advantageous, as when a protrusion is received in the inwardly recessed slot rotation of the nozzle ring about the central axis of the nozzle ring is restricted, thereby preventing against any substantial rotation of the nozzle ring about the central axis. It is desirable to prevent rotation of the nozzle ring, as rotation in the nozzle ring leads to efficiency losses of the turbocharger. During use of the turbine, exhaust gases which pass from an internal combustion engine, though the inlet volutes and to the nozzle ring apply pressure loading on the vanes of the nozzle ring. This aerodynamic pressure loading on the vanes can cause the nozzle ring to move relative to the central axis. Movement of the nozzle ring is undesirable, as it results in increased wear on sealing elements, for example seal rings and O-rings which seal the nozzle ring at least in part from the bearing housing. Wear of the sealing elements can reduce the efficiency and performance of the turbine as there may be increased leakage paths, and said wear could ultimately result in failure of the turbine. In addition to the protrusions providing alignment surfaces during manufacture and assembly of the turbine, they may also provide an anti-rotation feature when used in combination with the recessed slots. The recessed slots in the nozzle ring may have a complementary shape to the protrusions, such that the protrusions are received in the recessed slots. When the protrusions are received in the corresponding recessed slots, they may prevent rotation of the nozzle ring 3about the central axis. The protrusions may therefore act as an anti-rotation feature, preventing rotation of the nozzle ring and in turn mitigate against wear of the sealing elements caused by rotation of the nozzle ring. The term “the slot being positioned such that the entirety of the slot is located angularly between two adjacent vanes” encompasses the slot not entirely overlapping the plurality of vanes, or a line of extension of the plurality of vanes. The nozzle ring dividing wall may comprise a plurality of inwardly recessed slots. 69154916-1 M&C 30^^^^^^:2^ 13 The nozzle ring dividing wall may comprise three inwardly recessed slots. The nozzle ring dividing wall may at least three inwardly recessed slots. The number of slots provided on the nozzle ring may be equal to or greater than the number of protrusions provided on the turbine dividing wall. Each of the plurality of inwardly recessed slots may be positioned such that the entirety of each slot angularly is located between two adjacent vanes. The plurality of slots may be unequally distributed about the central axis. According to a fifth aspect of the invention there is provided a turbine for a turbocharger, the turbine comprising: a turbine housing according to the third aspect of the invention; and a nozzle ring according to the fourth aspect of the invention, wherein the protrusion of the turbine dividing wall is received in the slot of the nozzle ring dividing wall. The protrusion when received in the slot of the nozzle ring restricts rotation of the nozzle ring about the central axis, thereby preventing against any substantial rotation of the nozzle ring about the central axis. It is desirable to prevent rotation of the nozzle ring, as rotation in the nozzle ring leads to efficiency losses of the turbocharger. The protrusion and the slot of the nozzle ring may be complementary in shape. The protrusion and slot having complementary shapes aids in further restricting rotation of the nozzle ring about the central axis. A detailed description of one or more exemplary embodiments of the invention is provided below with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional drawing of a known turbocharger; Figure 2 is an end view of a manufacturing intermediate of a turbine housing according to an embodiment of the present invention; 69154916-1 M&C 30^^^^^^:2^ 14 Figure 3 is a cross sectional end view of the opposing end of the manufacturing intermediate shown in Figure 2; Figure 4 is a cross sectional perspective side view of the manufacturing intermediate shown in Figure 2 and 3; Figure 5 is a cross section perspective side view of part of the manufacturing intermediate shown in Figures 2 to 4 with part of a holding device positioned in the manufacturing intermediate; Figure 6 is a cross sectional side view of the manufacturing intermediate with a holding device; Figure 7 shows a front view of a nozzle ring according to an embodiment of the present invention; Figure 8 shows a cross sectional perspective view of a portion of the nozzle ring positioned within a turbine housing formed from a manufacturing intermediate according to an embodiment of the present invention; and Figure 9 shows a cross sectional perspective view of a portion of a further embodiment of a nozzle ring positioned within a turbine housing formed from a manufacturing intermediate according to an embodiment of the present invention. Figure 1 shows a schematic cross-section through a known turbocharger. The turbocharger comprises a turbine 1 joined to a compressor 2 via a central bearing housing 3. The turbine 1 comprises a turbine wheel 4 for rotation within a turbine housing 5. Similarly, the compressor 2 comprises a compressor wheel 6, of the centrifugal type, which can rotate within a compressor housing 7. The compressor housing 7 defines a compressor chamber within which the compressor wheel 6 can rotate. The turbine wheel 4 and compressor wheel 6 are mounted on opposite ends of a common turbocharger shaft 8 which extends through the central bearing housing 3. The turbine housing 5 has two inlet volutes 9 located annularly around the turbine wheel 4, and an axial exhaust gas outlet 10. The inlet volutes 9 are configured to 69154916-1 M&C 30^^^^^^:2^ 15 receive exhaust gas from separate banks of the internal combustion engine. The compressor housing 7 has an axial air intake passage (compressor inlet) 11 and an outlet volute 12 arranged annularly around the compressor chamber. The outlet volute 12 is in gas flow communication with a compressor outlet 13 that delivers the compressed air onwards to an internal combustion engine (not shown). The bearing housing 3 defines a bearing chamber through which the turbocharger shaft 8 passes. The shaft 8 is rotatably supported by a bearing assembly which comprises two journal bearings 14 and 15 housed towards the turbine end and compressor end respectively of the bearing housing 3. Oil is supplied to the bearing assembly from the oil system of the internal combustion engine via oil inlet 18 and is fed to the bearings 14, 15 by oil passageways 19. The oil fed to the bearings 14, 15 may be used to both lubricate the bearings and to remove heat from the bearings. In use, the turbine wheel 4 is rotated about an axis 25 by the passage of exhaust gas from the exhaust gas inlet 9 to the exhaust gas outlet 10. Exhaust gas is provided to exhaust gas inlet 9 from an exhaust manifold (also referred to as an outlet manifold) of the engine. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet 11 and delivers boost air to an inlet manifold of the engine via the volute 12 and then the outlet 13. The compressor chamber is defined between a shroud portion 17 of the compressor housing 7 and a hub portion 20 of the bearing housing 3. The compressor housing 7 shown in Figure 1 may be formed as a one-piece (i.e. integral) unit including the shroud portion 17, although in alternative embodiments may comprise multiple components. The shroud portion 17 has an inwardly facing shroud surface 21 which is circularly symmetric about the rotational axis 25. Figures 2 to 4 show a manufacturing intermediate 105 for a turbine housing. The manufacturing intermediate 105 is used in the manufacture of a turbine housing and, in particular, is a component that undergoes subsequent machining to arrive at its finished geometry. Typically, the manufacturing intermediate 105 is formed by casting and therefore the precise geometry of the manufacturing intermediate 105 will vary between individual castings, even when a consistent mould geometry is used. 69154916-1 M&C 30^^^^^^:2^ 16 Accordingly, the manufacturing 105 must undergo one or more machining operations in order to alter its geometry to a desired size and shape. With reference to Figures 2, 3, and 4, the manufacturing intermediate 105 comprises an inlet portion 107. The inlet portion 107 comprises two inlet volutes 109 (which can be best seen in Figure 4). In particular, the manufacturing intermediate 105 comprises a first inlet volute 109a and a second inlet volute 109b terminating in a first nozzle passage 110a and a second nozzle passage 110b respectively. The first and second inlet volutes 109a, 109b receive exhaust gas from separate banks of cylinders of an internal combustion engine (not shown). The manufacturing intermediate 105 further comprises a dividing wall 201 that separates exhaust gas flowing through the first inlet volute 109a from exhaust gas flowing through the second inlet volute 109b. The dividing wall 201 extends generally radially relative to a central axis 203 of the turbine housing 105, such that the first inlet volute 109a and the second inlet volute 109b are positioned axially adjacent to one another. Accordingly, the manufacturing intermediate 105 may be used in the manufacture of (and / or may be considered to define) an axially-divided twin volute turbine housing. The dividing wall 201 is integrally formed with the first and second inlet volutes 109a, 109b. The manufacturing intermediate 105 defines a turbine wheel chamber 111 that is configured to contain a turbine wheel (not shown) and a turbine outlet 113 for receiving exhaust gas that has passed through the turbine wheel. The manufacturing intermediate 105 further comprises a connection portion 205 which is configured to connect with another component of the turbine, for example a bearing housing and / or heat shield. The connection portion 205 further comprises a connection surface 207. The connection surface 207 is revolved around the central axis 203 and the connection surface 207 defines a first radius R1 from the central axis 203. The first radius R1 is measured as the innermost radius of the connection surface 207 relative to the central axis 203. Returning to the dividing wall 201. The dividing wall 201 further comprises three inwardly extending protrusions 211. That is to say the protrusions 211 extend from the dividing wall 201 in a direction towards the central axis 203. In particular, the protrusions 211 extend from a base portion 212 of the dividing wall 201. The base 69154916-1 M&C 30^^^^^^:2^ 17 portion 212 defines a constant radius the central axis 203 and defines the part of the dividing wall 201 from which the protrusion 211 extends. The inwardly extending protrusions 211 may also be referred to as location pads. The protrusions 211 are integrally formed with the dividing wall 201. In other embodiments the manufacturing intermediate 105 may comprise less than three protrusions (e.g. one or two protrusions), or it may comprise more than three protrusions (e.g. four, or five, or six protrusions). The dividing wall 201 defines a terminal edge 209 running along its radially innermost extent. The terminal edge 209 is the inner rim of the dividing wall 201 with respect to the central axis 203 and runs along both the base portion 212 and the protrusions 211. The terminal edge 209 defines a second radius R2 from the central axis 203. The second radius R2 encompasses the innermost radius of the terminal edge 209 of the dividing wall 201 relative to the central axis 203. Accordingly, the second radius R2 is defined at the apex of one or more of the protrusions 211. Because the dividing wall 201 comprises the inwardly extending protrusions 211, the terminal edge 209 of the dividing wall 201 does not have a constant radius. As such, in the embodiments shown in Figures 2 to 4, the innermost radius of the dividing wall 201 lies on an edge of a protrusion 211 that is closest to the central axis 203. The second radius R2 is smaller than the first radius R1. In other words, the distance between the central axis 203 and the innermost radius of the dividing wall 201 is less than the distance between the central axis 203 and the connection surface 207. The base portion 212 defines a third radius R3 from the central axis 203. In the illustrated embodiment, the third radius R3 is bigger than the second radius R2. In other embodiments, the dividing wall 201 may not comprise inwardly extending protrusions 211 (i.e. the protrusions 211 may be absent), but nevertheless the second radius R2 may be smaller than the first radius R1 of the connection surface 207. In embodiments that do not comprise a protrusion 211, the base portion 212 may define the second radius R2, such that the second radius R2 and the third radius R3 are equal. 69154916-1 M&C 30^^^^^^:2^ 18 The dividing wall 201 further an alignment surface 213. The alignment surface 213 is a face, or at least part of a face, of the dividing wall 201. In particular, in the embodiment shown in Figures 2 to 4, the alignment surface 213 is a face of the inwardly extending protrusions 211. The alignment surface 213 is a substantially flat surface lying in a plane substantially normal to the central axis 203. In other embodiments, i.e. embodiments where the dividing wall 201 does not comprise inwardly extending protrusions 211, the alignment surface 213 may simply be a face of the dividing wall 201. The alignment surfaces 213 face towards the connection portion 205. The alignment surfaces 213 are configured to abut an abutment portion of a holding device (not shown in Figures 2 to 4), which is explained in more detail below in relation to Figure 5. Because the second radius R2 is smaller than the first radius R1, the alignment surfaces 213 can be abutted by a holding device that is inserted into to the manufacturing intermediate 105, at least when inserting the holding device via the connection portion 205. If the second radius R2 was not smaller than the first radius R1, the holding device would not be able to abut against the alignment surface 213. Preferably, the second radius R2 should be smaller than the first radius R1 by around 5 % to 20 % of the first radius R1, so as to enable the alignment surfaces 213 to protrude sufficiently deeply for abutment by the holding device. In some embodiments the connection surface 207 which defines the first radius R1 may not be concentric with the terminal edge 209 that defines the second radius R2 and / or the base portion 212 which defines the third radius R3. In instances where the first, second and third radii R1, R2, R3 cannot be measured from a single concentric point, it will be understood, that the surface which defines the second radius R2 should be radially inwards, relative to the central axis 203 of the first radius R1 such that the alignment surfaces 213 can be abutted against a holding device. By abutting the holding device against the alignment surfaces 213, this enables the alignment surfaces 213 to be used as the datum point for subsequent machining operations. Accordingly, the axial widths of the nozzle passages 110a, 110b and the axial width 204 of the nozzle dividing wall 201 relative to the central axis 203 can be toleranced from the dividing wall 201, which is positioned centrally between the nozzle passages 110a, 110b. This avoids compound tolerancing errors that would be caused 69154916-1 M&C 30^^^^^^:2^ 19 by a so-called tolerance ‘stack’ that a datum from another point of the manufacturing intermediate 105. For example, in prior art methods, the holding device is often abutted against a side 214 of the second nozzle passage 110b, which is then used as the datum point. However, the side 214 of the second nozzle passage 110b may vary from casting to casting, and therefore any subsequent machining operations to the dividing wall 201 that are based upon a particular spacing from the side 214 will inherently include the geometrical variations caused by the casting quality of the side 214 on top of any standard tolerance variations based on machining processes dimensioned from the datum. In particular, this may cause misalignment of the dividing wall 201 with the dividing wall of a corresponding nozzle ring. In the present invention, because the alignment surface 213 is positioned in the centre of the nozzle passage and because the alignment surface 213 is used as the datum, this reduces the number of compound tolerance variations defining the nozzle passages, and helps to improve alignment between the dividing wall 201 the dividing wall of any nozzle ring with which the manufacturing intermediate 105 is assembled. This in turn mitigates against the occurrence of so-called ‘cross-talk’ between the inlet volutes 109a, 109b (i.e. it provides increased pulse separation into the turbine wheel) and hence reduces losses in turbine stage efficiency. The protrusions 211 are equi-angularly spaced about the central axis 203. In other embodiments, the protrusions 211 may not be equi-angularly spaced (i.e. the protrusions 211 may be unequally angularly spaced). The protrusions 211 being unequally angularly spaced is beneficial as it can ensure correct orientation of the manufacturing intermediate and other tools (such as the holding device) during manufacturing and assembly processes. This is because, by way of example, when the protrusions are unequally spaced the holding device may only be able to abut against the alignment surface 213 if the manufacturing intermediate and / or the holding device is in a particular orientation (i.e. abutment may not be possible for all orientations). In addition to the inwardly extending protrusions 211, the dividing wall 201 further comprises an extending tongue 215 (see Figure 3). The tongue 215 is configured to be received in a corresponding slot of a nozzle ring. Because the tongue 215 is received in a slot of a nozzle ring, rotation of the nozzle ring about the central axis 203 is prevented. The extending tongue 215 is an optional feature, in other embodiments, the tongue 215 may not be present. 69154916-1 M&C 30^^^^^^:2^ 20 Figure 5 shows a cross sectional perspective side view of part of the manufacturing intermediate 105. Received in the manufacturing intermediate 105 is part of a holding device 217 which is arranged to hold the manufacturing intermediate 105 in a fixed position. Holding the manufacturing intermediate 105 in a fixed position is required to carry out further manufacturing and / or assembly processes. The holding device 217 defines an abutment portion 223 in the form of a plurality of jaws arranged in a chuck. In particular, the abutment portion 223 comprises a three-jaw chuck, although in Figure 5 only a first jaw 219 and a second jaw 221 are visible. The first jaw 219 comprises a first surface 250 defining a terminal end of the jaw, and a second surface 225 defining an outer axially extending side of the jaw 219. The abutment portion 223 is inserted into the connection portion 205 of the manufacturing intermediate 105 such that the first surface 250 is brought into abutment against the alignment surface 213 of dividing wall 201. Corresponding first surfaces of the remaining jaws in the abutment portion 223 are brought into contact with the alignment surfaces 213 of the remaining protrusions 211. The surface area of the first surface 250 is greater than the surface area of the alignment surface 213 allowing the first surface 250 of the abutment portion 223 to be easily and readily located onto the alignment surface 213. As described above, the holding device 217 in this embodiment is a three jaw chuck. Accordingly, the manufacturing intermediate 105 comprises three protrusions 211. In other embodiments, where the number of inwardly extending protrusions 211 may be different to three, the number of jaws of the chuck may be equal to the number of inwardly extending protrusions 211. Nevertheless, even when there are more than three protrusions 211, the chuck may still only comprise three jaws which are then able abut against at least three of the protrusions 211, this may be advantageous for easily locating the abutment portion 223 against the alignment surface 213. Dependent upon the relative location of the inwardly extending protrusions 211 and the extending tongue feature 215, at least one of the jaws 219, 221 may be specially shaped such that the abutment portion 223 of the holding device 217 can fit around the extending tongue feature 215 and still maintain good contact against the alignment surface 213. Although a three jaw chuck is shown in Figure 5, it will be appreciated that 69154916-1 M&C 30^^^^^^:2^ 21 any suitable holding device may be can abut against the alignment surface 213, and hold a manufacturing intermediate / turbine housing during a machining and / or manufacturing process. Once the first surface 250 of the jaw 219 is brought into engagement with the alignment surface 213 the holding device 217 is then adjusted so that the second surface 225 of the jaw 219 abuts against the connection surface 207 of the connection portion 205. Corresponding second surfaces of the remaining jaws defining the abutment portion 223 are also brought into contact with the connection surface 207. The jaws 219, 221 of the abutment portion 223 exert an outward radial force on the connection surface 207 which thereby holds the manufacturing intermediate 105 securely in place. With reference to Figure 6, the manufacturing intermediate 105 may be further machined to form a turbine housing for use in a turbocharger. As described above, the manufacturing intermediate 105 is initially held in place with the holding device 217. Following this, the turbine outlet 113 is machined so as to define a turbine outlet connection portion 227. In particular, the turbine outlet connection portion 227 is machined so that it is provided with an end face 252 that has a predetermined spacing X from the first surface 250 of the abutment portion 223 of the holding device 217. The spacing X may be referred to as the so-called ‘set-up dimension’. The turbine outlet connection portion 227 may be machined using one or more turning operations to remove unwanted material form the manufacturing intermediate 105. The one or more turning operations may be so-called ‘rough’ turning operations, or may be so-called ‘smooth’ turning operations that provide the turbine outlet 113 with a particular the surface finish / roughness. The one or more machining operations may also include performing a machining operation using a cutting tool on the turbine outlet 113 so as to machine the thickness of the turbine outlet wall 229 to within a predetermined thickness. The machining of the turbine outlet wall 229 may also be a ‘rough’ turning operation, or a ‘smooth’ turning operation. Although the machining operations are described are turning operations, other machining operations, for example, milling may be used. Following machining of the turbine outlet connection portion 227 and / or the turbine outlet wall 229, a depth micrometer 231 is used to measure the distance from an outlet 69154916-1 M&C 30^^^^^^:2^ 22 face 233 of the turbine outlet portion 227 to the first surface 250 of the abutment portion 223 of the holding device 217. This distance is measured to the first surface 250 of the abutment portion 223 because there is no direct line of access to the face of the protrusions 211 opposite the alignment surface 213, due to the protrusions 211 having a larger radius measured from the central axis 203 than the radius of the turbine outlet passage 113 (as can be best seen in Figure 4). Further machining operations may be carried out until the predetermined spacing X between the outlet face 233 and the abutment portion 223 is achieved. Once the pre-determined set-up dimension is achieved the features of the turbine outlet 113 (i.e. features that are axially downstream of the turbine wheel when in use) can be machined. These further machining steps may be done by a computer numerical control (CNC) program, to produce the features of the turbine outlet 113. In providing a set-up dimension using the inwardly extending protrusions 211 the position of the dividing wall 211 relative to the turbine outlet connection portion 233 is known. The holding device 217 may then be removed from the connection portion 205. The holding device 217 may then be inserted into the manufacturing intermediate 105 via the turbine outlet 113 end of the manufacturing intermediate 105. The jaws 219, 221 (and the third jaw which is not visible) are located against an internal wall 235 of the turbine outlet 113, such that the manufacturing intermediate 105 is held again in a fixed position relative to the holding device 217. Alternatively, this may be achieved using a different holding device specifically adapted for receipt within the turbine outlet 113 (for example, comprising a different chuck arrangement). Further machining operations can then be conducted upon the turbine wheel chamber 111 and the connection portion 205, and the dividing wall 201 to machine these features to a desired final geometry. Because the set-up dimension X between the alignment surface 213 and the end face 252 of the outlet 113 has already been machined into the manufacturing intermediate 105, when the holding device is provided in the turbine outlet 113 the further machining operations can take their datum from the end face 252. Thus, the tolerances for the further machining operations can be controlled based upon the relationship between the end face 252 and the alignment surface 213 which, as explained above, is 69154916-1 M&C 30^^^^^^:2^ 23 positioned centrally to the nozzle Accordingly, this promotes accurate alignment with a nozzle ring, when the nozzle ring is provided. In some embodiments one of the final machining operations may be to machine away the inwardly extending protrusions 211. If the inwardly extending protrusions are machined away, the dividing wall 201 will have a constant radius which is the distance between the central axis 203 and the base portion 212 of the dividing wall 201. On the other hand, the protrusions 211 may remain as integrally formed parts of the dividing wall as anti-rotation features. The protrusions 211 may be machined further to form a specific shape. Figure 7 shows a front view of a nozzle ring 301. As will be more apparent in Figure 8, the nozzle ring 301 is a nozzle ring for a twin volute turbine. The nozzle ring 301 comprises a nozzle ring dividing wall 303 from which a first plurality of vanes 305 extend from a first face 307 of the nozzle ring dividing wall 301. The nozzle ring dividing wall 303 is an annular wall which encircles the central axis 203. The nozzle ring dividing wall 303 further comprises a second face 309 which is opposite the first face 307 (not visible in Figure 7). A second plurality of vanes 311 (not visible in Figure 7) extend from the second face 309 in a direction generally opposite to the first plurality of vanes 305. The first and second plurality of vanes 305, 311 are provided to guide flow, particularly exhaust gas flow, to a desired angle to the turbine wheel when in use. In use, and as can be better seen in Figure 8, the nozzle ring dividing wall 303 is concentric with an axially aligned with the dividing wall 201 of a turbine housing formed from a manufacturing intermediate 105. In use, exhaust gas flow from the first and second volutes of a turbine can be guided by the plurality of vanes 305, 311 of the nozzle ring 301 towards a turbine wheel (not shown). The nozzle ring dividing wall 303 comprises three inwardly recessed slots 313 such that a terminal edge 315 of the nozzle ring dividing wall 303 (i.e. an outer perimeter of the nozzle ring) has a variable radius when measured from the central axis 203. The three inwardly recessed slots 313 are provided to receive the three inwardly extending protrusions 211 of a finished turbine housing derived from the manufacturing intermediate 105. The inwardly recessed slots 313 are positioned such that the entirety 69154916-1 M&C 30^^^^^^:2^ 24 of the slot is located angularly two adjacent vanes 307. This prevents interference between the slots 313 and the vanes 307. In particular, this avoids the need to form part of the vane geometry on the protrusions 211. Turning to Figure 8, the nozzle ring 301 is shown in use, where it is received in a turbine housing formed from a manufacturing intermediate 105. The nozzle ring dividing wall 303 is axially aligned with, and concentric with, the turbine dividing wall 201. The inwardly recessed slots 313 are positioned to receive a corresponding inwardly extending protrusion 211 of the turbine dividing wall 201. The inwardly recessed slots 313 have a complementary shape to the protrusions 211. Because the protrusions 211 are received in the slots 313, rotation of the nozzle ring 301 about the central axis 203 is restricted. Restricting rotation of the nozzle ring 301 mitigates against efficiency losses in the turbine during use. During use of the turbine, exhaust gases which pass from an internal combustion engine, though the inlet volutes and to the nozzle ring 301 apply pressure loading on the vanes 305 of the nozzle ring 301. This aerodynamic pressure loading on the vanes 305 can cause the nozzle ring 301 to move relative to the central axis 201. Movement of the nozzle ring 301 is undesirable, as it results in increased wear on sealing elements, for example seal rings (not shown in the present embodiments) which seal the nozzle ring 301 at least in part from the bearing housing. Wear of the sealing elements can reduce the efficiency and performance of the turbine as there may be increased leakage paths, and said wear could ultimately result in failure of the turbine. In addition to the protrusions 211 providing alignment surfaces during manufacture and assembly of the turbine, they can also provide an anti-rotation feature when used in combination with the slots 313 in the nozzle ring 301. The slots 313 in the nozzle ring have a complementary shape to the protrusions 211, such that the protrusions 211 are received in the slots 211. When the protrusions 211 are received in the corresponding slots 313, they prevent rotation of the nozzle ring 301 about the central axis 203. The protrusions 211 therefore act as an anti-rotation feature, preventing rotation of the nozzle ring 301 and in turn mitigating against wear of the sealing elements caused rotation of the nozzle ring 301. In alternative embodiments, the nozzle ring 301 may comprise any number of inwardly recessed slots 313 that are configured to receive corresponding protrusions 211 of a dividing wall 201. However, the number of recessed slots 313 will typically be equal to 69154916-1 M&C 30^^^^^^:2^ 25 the number of protrusions 211, an excess of recessed slots could result in undesirable exhaust gas flow between the volutes. It will be appreciated that in turbine housings formed from the manufacturing intermediate 105, where the inwardly extending protrusions 211 are machined away as part of the manufacturing process, the nozzle ring used in the turbine will not comprise inwardly extending recesses 313 as these would result in exhaust gas flow passing between the two turbine housing volutes, which is undesirable. Although in the embodiments shown, the dividing wall 201 of the manufacturing intermediate 105 and the nozzle ring dividing wall 303 extend generally radially relative to the central axis 203, it will be appreciated that in alternative embodiments the dividing wall 201 and the nozzle ring dividing wall 303 may extend at an angle that is non-radial relative to the central axis 203, for example as part of a mixed flow turbine. With reference to Figure 9, the terminal edge 209 dividing wall 201 of the manufacturing intermediate 105 comprises a sealing formation 254. The sealing formation 254 is a recessed groove configured to define a fluidic sealing formation of the kind disclosed in the applicant’s International Patent Application WO2020 / 169986. In particular, the recessed groove is configured to generate turbulence within any exhaust gas that passes through an interface 256 between the outer edge of the nozzle ring dividing wall 307 and the terminal edge 209 dividing wall 201, thus mitigating against so-called ‘cross-talk’ between the inlet volutes 109a, 109b. Suitable alternative fluidic sealing arrangements include, for example, labyrinth seals or the like. Although the sealing formation 254 described above is a fluidic sealing formation, it will be appreciated that in alternative embodiments the sealing formation 254 may comprise any suitable sealing arrangement. In particular, the sealing formation 254 may comprise a mechanical obstruction seal, such as for example an O-ring or the like. 69154916-1

Claims

M&C 30^^^^^^:2^ 26 CLAIMS:

1. A manufacturing intermediate for a turbine housing, the manufacturing intermediate being configured for engagement with an abutment portion of a holding device during machining, the manufacturing intermediate comprising: a connection portion comprising a connection surface defining a first radius from a central axis; an inlet portion defining a turbine inlet having two inlet volutes axially separated by a dividing wall, the dividing wall comprising a terminal edge defining a second radius from the central axis; wherein the second radius is smaller than the first radius such that the dividing wall defines an alignment surface configured to abut the abutment portion to align the dividing wall with the abutment portion.

2. A manufacturing intermediate according to claim 1, wherein the terminal edge of the dividing wall comprises an inwardly extending protrusion defining the alignment surface, and wherein the protrusion defines the second radius.

3. A manufacturing intermediate according to claim 2, wherein the terminal edge of the dividing wall defines a circumferentially extending base portion having a constant radius from the central axis, and wherein the protrusion extends radially inward from the base portion.

4. A manufacturing intermediate according to claim 2 or claim 3, wherein the terminal edge of the dividing wall comprises at least three protrusions spaced apart about the central axis.

5. A manufacturing intermediate according to claim 4, wherein the at least three protrusions are unequally distributed about the central axis.

6. A manufacturing intermediate according to any of claims 3 to 5, wherein the base portion of the dividing wall defines a third radius from the central axis, the third radius being greater than the second radius. 69154916-1M&C 30^^^^^^:2^ 27 7. A manufacturing intermediate to any preceding claim, wherein the ratio of the second radius to the first radius is within the range of between around 0.75 to around 0.

95.

8. A manufacturing intermediate according to any preceding claim, wherein the alignment surface is a substantially flat surface lying in a plane substantially normal to the central axis.

9. A manufacturing intermediate according to any preceding claim, wherein the terminal edge of the dividing wall comprises a sealing formation.

10. A method of manufacturing a turbine housing, the method comprising: obtaining a manufacturing intermediate according to any preceding claim; inserting an abutment portion of a holding device into the connection portion; abutting a first surface of the abutment portion against the alignment surface; and abutting a second surface of the abutment portion against the connection surface.

11. A method according to claim 10, wherein the method comprises machining the manufacturing intermediate.

12. A method according to any of claim 11, wherein machining the manufacturing intermediate includes: performing at least one turning operation and / or at least one milling operation.

13. A method according to claim 11 or claim 12, wherein the manufacturing intermediate comprises an outlet portion defining a turbine outlet, and wherein the step of machining the manufacturing intermediate includes: performing a turning operation to remove material from an end face of the turbine outlet portion until a predetermined axial distance between the end face of the outlet portion and the first surface of the abutment portion is achieved. 69154916-1M&C 30^^^^^^:2^ 28 14. A method according to any of 10 to 13, wherein the holding device comprises a chuck.

15. A method according to any of claims 10 to 14, wherein the method further comprises: disengaging the holding device from the manufacturing intermediate; engaging the end face of the outlet portion with the holding device; and machining the manufacturing intermediate.

16. A method according to any of claims 10 to 15, wherein the terminal edge of the dividing wall comprises an inwardly extending protrusion defining the alignment surface, and wherein the protrusion defines the second radius; and wherein the method further comprises performing a machining operation to remove material from the dividing wall to reduce the size of the protrusion.

17. A method according to any of claims 10 to 16, wherein the method further comprises performing a machining operation to remove material from the dividing wall so as to remove the alignment surface entirely.

18. A turbine housing for a turbocharger, the turbine housing defining: a connection portion comprising a connection surface defining a first radius from a central axis; an inlet portion defining a turbine inlet having two inlet volutes axially separated by a dividing wall, the dividing wall comprising a terminal edge defining an inwardly extending protrusion; wherein the protrusion defines a second radius smaller than the first radius; and wherein the protrusion is configured to be received by a correspondingly shaped slot of a nozzle ring.

19. A turbine housing according to claim 18, wherein the terminal edge of the dividing wall defines a plurality of protrusions.

20. A turbine housing according to claim 19, wherein the plurality of protrusions are unequally distributed about the central axis. 69154916-1M&C 30^^^^^^:2^ 29 21. A turbine housing according to of claims 18 to 20, wherein the terminal edge of the dividing wall comprises a sealing formation.

22. A turbine housing according to claim 21, wherein the sealing formation extends around the entire circumference of the terminal edge of the dividing wall.

23. A nozzle ring for a turbine for a turbocharger, the nozzle ring comprising: an annular nozzle ring dividing wall encircling a central axis; and a plurality of vanes extending from the nozzle ring dividing wall; and wherein the nozzle ring dividing wall comprises an inwardly recessed slot for receiving a protrusion of a turbine dividing wall, the slot being positioned such that the entirety of the slot is located angularly between two adjacent vanes.

24. A nozzle ring according to claim 23, wherein the nozzle ring dividing wall comprises a plurality of inwardly recessed slots.

25. A nozzle ring according to claim 24, wherein each of the plurality of inwardly recessed slots is positioned such that the entirety of each slot angularly is located between two adjacent vanes.

26. A nozzle ring according to claim 24 or claim 25, wherein the plurality of slots are unequally distributed about the central axis.

27. A turbine for a turbocharger, the turbine comprising: a turbine housing according to any of claims 18 to 22; and a nozzle ring according to claim any of claims 23 to 26, wherein the protrusion of the turbine dividing wall is received in the slot of the nozzle ring dividing wall. 69154916-1

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