GB2597478A

GB2597478A - Turbine rotary cup atomizer

Info

Publication number: GB2597478A
Application number: GB2011355.1A
Authority: GB
Inventors: David Hughes Stephen; Kenneth Sharp Nicholas; Mahmood Atif; Archer Jamie
Original assignee: Cummins Ltd
Current assignee: Cummins Ltd
Priority date: 2020-07-22
Filing date: 2020-07-22
Publication date: 2022-02-02
Also published as: GB202011355D0

Abstract

A rotary cup atomizer, eg for atomizing diesel exhaust fluid (DEF) in a turbocharger, comprises a cup 40 having a central axis coincident with the turbine axis A and a concentric frustoconical wall 43 extending from a base 41 and diverging from the central axis A, the edge of the wall 43 distal from the base 41 defining the open side of the cup 40. The inner surface 44 of the wall 43, facing the axis A, has a plurality of protrusions, eg ribs or fins, and/or recesses, eg straight or helical grooves 46. The groove depth may increase near the open side to form slots 58. Through-holes 70 may be provided in the wall 43. The rotary cup 40 may be integrally formed in the hub (36, fig.8) of a turbine wheel (33). For connecting to a shaft, the cup 40 may be held by a tool (100, fig.9) having protrusions (105) and/or recesses complementary to those of the cup; before the tool is removed, an impeller may be mounted at the other end of the shaft.

Description

I

TURBINE ROTARY CUP ATOMIZER

Field of the invention

The present application relates generally to the field of after-treatment systems for internal combustion engines, and particularly, but not exclusively to a turbine rotary cup atomizer provided in a turbocharger.

Background of the invention

Internal combustion engines, such as diesel engines, may emit carbon monoxide, hydrocarbons, particulate matter and nitrogen oxide compounds (NOx) in the exhaust. There are a number of legal requirements throughout the world which govern emission standards, and these requirements are becoming increasingly stringent, particularly in relation to nitrogen oxides (NOx) emissions. To reduce NOx emissions engine manufacturers may make use of exhaust gas recirculation and selective catalytic reduction (SCR).

Selective catalytic reduction (SCR) is an exhaust gas after-treatment, used to convert NOx into compounds that are less reactive, such as diatomic nitrogen and water, with the aid of a catalyst and a reductant. A liquid-reductant agent, such as anhydrous ammonia, aqueous ammonia, or urea, all which may be commonly referred to as Diesel Exhaust Fluid (DEF), is injected into the exhaust stream upstream of the catalyst.

In order to effectively convert the nitrogen oxides of the exhaust gas, the correct amount of DEF for given operating conditions is required, and efficient mixing of the DEF with the exhaust gas flow must also occur.

If the DEF is not adequately and uniformly mixed with the exhaust gas flow, when the mixture of exhaust gas and DEF passes through the catalyst, the reduction of nitrogen oxides is lower than if the DEF were uniformly distributed. This can result in nitrogen oxides being emitted into the atmosphere that are in excess of those permitted by various governing standards.

WO 2018/080371 discloses a cup-shaped exhaust additive distribution device ("rotary cup atomizer') provided on a turbine wheel of a turbocharger. The turbine wheel is mounted on a shaft of the turbocharger, and the mixing cup is provided on a hub of the turbine wheel, with the opening of the cup directed away from the shaft. In operation, DEF is sprayed into the device, and rotation of the turbine wheel promotes mixing of the DEF with exhaust gas.

The rotary cup atomizer needs to be suitably large to receive the DEF for liquid breakdown to occur, and then atomization of the DEF as it leaves the cup. Accordingly, dosing cups and dosing wheels may have a diameterwhich is greater than the hub radius of the turbine wheel it is mounted to. The dosing cup and dosing wheel therefore often impede the exhaust gas flow exiting from the turbine wheel, and can adversely affect downstream components of the after-treatment system.

Further, the turbine wheel is often mounted to the shaft using friction welding or electron beam welding. In the case of friction welding, a formation of radially-projecting protrusions, such as a star boss, is defined by the periphery of the hub of the turbine wheel, and a tool holds the protrusions during the welding, to prevent the turbine wheel from rotating. After the turbine wheel is welded to the shaft, a compressor wheel ("impeller") is mounted on the opposite end of the shaft from the turbine wheel. This opposite end of the shaft is usually provided with a threaded surface. The end of the shaft is passed through a central aperture in the impeller, and then a lock nut is tightened onto the threaded surface. The protrusions on the turbine hub are held by the tool during the tightening process to prevent the turbine wheel and shaft from rotating. However, the protrusions prevent the hub from having a smooth outer surface and may disturb gas flow exiting from the turbine wheel.

It is a preferred object of the invention to overcome or mitigate some or all the above problems.

It is also an object of the present invention to provide an improved or altemative turbine rotary cup atomizer.

It is also an object of the present invention to provide an improved or altemative method for mounting a turbine wheel to a shaft of a rotor assembly.

It is also an object of the present invention to provide an improved or alternative method for mounting an impeller to a shaft, where the impeller is mounted to an opposite end of the shaft from the turbine wheel.

In a first aspect of the invention there is provided a rotary cup for rotation about a turbine axis comprising: a base having a central axis coincident with the turbine axis, a wall disposed concentrically to the central axis, extending from the base and diverging from the central axis in a direction away from the base. An edge of the wall distal from the base defines an open side of the cup, and the wall further defines an inner surface facing the central axis, wherein the inner surface defines a plurality of protrusions and/or recesses.

The rotary cup is operative to receive diesel exhaust fluid, or any other desired fluid, and when in use, rotation of the rotary cup promotes liquid breakdown and the received fluid is dispersed on the inner surface of the rotary cup. The rotary cup causes the received liquid to exit from the open side of the rotary cup as a fine spray, and the cup can be considered to atomize the fluid. Providing recesses and/or protrusions on the inner surface of the rotary cup increases the mechanical interaction between the inner surface and the received fluid. Further, the recesses, and/or protrusions help to reduce fluid slippage and provide increased momentum to the liquid, further improving atomization of the DEF as it leaves the rotary cup. Advantageously, because the rotary cup according to the present invention when in use breaks down liquid more effectively, the fine spray of liquid that leaves the rotary cup mixes more uniformly with exhaust gas that flows concentrically to the rotary cup, so that the percentage of nitrogen oxides that are reduced downstream of the a rotary cup with a catalyst is increased.

Further, because the protrusions and/or recesses mean that when the rotary cup is in use the breakdown of liquid is improved, a smaller rotary cup may be provided compared to a known rotary cup with no protrusions or recesses. As the rotary cup may be mounted to the hub of a turbine wheel, the aerodynamic drag caused by the rotary cup will be reduced due to the cup having a smaller diameter.

There may also be provided a tool for engagement with the rotary cup. A surface of the tool defines a plurality of grooves recesses and/or protrusions that correspond in shape and size to the recesses and/or protrusions of the cup. Thus, when the tool is provided in the rotary cup the recesses and/or protrusions of the tool engage and interlock with the corresponding recesses and/or protrusions of the rotary cup and prevent rotation of the rotary cup relative to the tool. In instances when the rotary cup has a fixed angular relationship to a turbine wheel, the tool can be used to engage the rotary cup and prevent relative rotation of the turbine wheel. Advantageously, the protrusions and/or recesses of the rotary cup allow for the rotary cup in combination with a tool to be held in a fixed angular position, and prevent the rotation of another component, such as a turbine wheel, that the rotary cup has a fixed angular relationship with. This can aid in the mounting of a shaft to a turbine wheel such as by friction welding. This can further aid in the mounting of an impeller to a second shaft, when a turbine wheel is mounted to a first end of the shaft. Accordingly, another aspect of the disclosure is a combination of the rotary cup defined above and the tool.

The plurality of protrusions of the rotary cup may be a plurality of fins. The fins may extend from the inner surface of the cup in a direction towards the central axis. At least some, and preferably all, of the fins may intersect with a single plane transverse to the axis.

The plurality of recesses defined by the inner surface of the rotary cup may be a plurality of grooves. The grooves may extend from the edge of the wall to the base of the cup.

The inner surface of the rotary cup may define only a plurality of grooves, such that the inner surface does not define any protrusions.

At least one of the grooves may be a straight groove. A straight groove is a groove for which central points in the groove, at different respective positions along the length of groove, form a straight line.

At least one of the grooves may be a helical groove. Helical grooves, are grooves in which at each point along the groove the extension direction of the groove (e.g. the direction which is transverse to the semi-circular cross-section of the groove) of the groove is not co-planar with the central axis of the rotary cup and forms a constant angle with respect to the central axis, such that each groove has a circumferential component at all points along its length.

The maximum depth of each groove may be constant along the length of each groove.

Such that the depth of the groove proximate the open side of the rotary cup, is the same at any other point along the length of the cup.

The profile of at least one of the grooves in a plane parallel to the open side of the cup may be an arc. Further, the profile of at least one of the grooves in a plane parallel to the open side of the cup may be a square, a rectangle, or any other polygonal shape.

The number of grooves may be less than or equal to 12 Optionally, the number of grooves may be less than or equal to 10.

Optionally, the number of grooves may be greater than or equal to 4, and less than or equal to 8.

The grooves may be equally spaced about the central axis.

Each groove may have a groove length GL, and the open side of the cup has an outermost diameter OD. The ratio of the groove length, GL to the outer diameter, OD, (GL/OD) may be between 0.8 and 2.

Optionally, GL/OD may be between 0.9 and 1.5. Optionally GL/OD may be equal to 1.

The wall of the rotary cup at the open side may have a thickness, T. The depth of at least one grooves may increase proximate the open side of the rotary cup such that the depth of the groove is equal to the thickness, T of the rotary cup, and thus forms a slot in the wall of the rotary cup at the open side of the rotary cup.

The rotary cup may be provided with at least one through-hole in the wall. The through-hole extends from the inner surface of the cup to an outer surface of the cup.

The presence of the through-hole in the cup allows for DEF that is injected into the cup to exit from the cup upstream of DEF that exits the cup at the open side, when the cup is rotating about the central axis. This promotes further mixing of DEF with exhaust gas flow and promotes further atomisation of the DEF, as the through-hole forms a discontinuity on the inner surface of the cup.

The rotary cup may be integrally formed in a hub of the turbine wheel. The hub may define the base and the wall of the rotary cup. Advantageously, this obviates the need to mount a rotary cup onto the hub of a turbine wheel when the rotary cup is being provided as part of as SCR system in combination with a turbocharger.

There may be provided a turbine comprising a turbine housing having an inlet and an outlet. A turbine wheel may be mounted in the turbine housing between the inlet and the outlet for rotation about a rotational axis. The turbine wheel may comprise a hub and the hub defines a rotary cup according to the first aspect of the invention. In other words, the rotary cup may be an integral part of the turbine, such as produced in the same moulding operation optionally followed by machining. Alternatively, the cup and turbine wheel may be formed separately, and the base of a rotary cup according to the first aspect of the invention may be mounted to the hub of the turbine wheel. The turbine may be a turbine for use in a turbocharger.

A second aspect of the invention is a method of connecting a turbine wheel to a shaft, the turbine wheel having a rotational axis and having a fixed angular relationship to a rotary cup. The rotary cup being a cup according to the first aspect of the invention. The rotational axis of the turbine wheel coinciding with the central axis of the cup.

The method comprises inserting a tool into the cup, the tool comprising a plurality of recesses and/or protrusions corresponding in shape and size to the recesses and/or protrusions of the cup. The insertion of the tool into the cup causes the corresponding recesses and/or protrusions of the cup and tool to interlock to prevent relative rotation of the cup and tool about the axes. The tool is then held (e.g. by a vice) in a fixed angular position. The shaft is rotated about an axis which coincides with the rotational axis of the turbine and a length direction of the shaft. The shaft is moved along the axis relative to the turbine wheel from the side of the turbine wheel opposite the cup towards the turbine wheel, thereby forming a friction weld between the shaft and the turbine wheel. Then the tool is removed from the cup.

Moving the shaft along the axis from the side of the turbine wheel opposite the cup means moving the shaft in a direction such that if the shaft were imagined to pass through the turbine wheel and cup along the axis, it would first contact the center of the turbine wheel, then contact the base of the cup, pass through the cup and then exit the cup at the open side of the cup.

Holding the turbine wheel in a fixed angular position allows an improved weld between the shaft and the turbine wheel to be formed. If the turbine wheel is not held in a fixed angular position when being joined to the shaft, the join between the weld and the shaft 15 may be weaker.

The method of joining a turbine wheel to a shaft as set out above, is particularly advantageous when the turbine wheel is for use in a turbocharger. This is because the hub of the turbine wheel is usually formed with a cylindrical cavity for receiving the shaft, such that the hub of the turbine wheel is positioned concentrically around an end portion of the shaft. It is therefore desirable for a weld between the shaft and the hub of the turbine wheel to be formed in the cylindrical cavity rather than merely at an edge of the hub which meets the shaft. This can be achieved by use of friction welding. Friction welding also obviates the need for use of a filler material and gases, and produces a weld with a small heat affected zone. Providing an improved method of holding the turbine wheel in a fixed angular position when friction welding to a shaft, or through any other welding that is desired, leads to an improved weld between the turbine wheel and the shaft, the weld having improved sheared strength, compared to a weld formed whereby the turbine wheel is not held in a fixed angular position.

The method may further comprise mounting an impeller to a second end of the shaft, wherein the second end of the shaft is opposite the end to which the turbine wheel is mounted. Mounting the impeller to the second end of the shaft comprises, inserting the tool into the rotary cup and holding the tool in a fixed angular position to prevent rotation of the shaft, then mounting the impeller to the second end of the shaft, and once the impeller is mounted to the second end of the shaft removing the tool, such that the shaft with a turbine wheel mounted to a first end and an impeller mounted to a second end can rotate about a central axis of the shaft.

The impeller may be mounted to the shaft by friction welding, or alternatively by providing a threaded portion of the shaft which is passed through an aperture in the impeller, and onto which a locking component, such as a lock nut, is tightened. Being able to hold the shaft in a fixed angular position as described above allows the impeller to be mounted onto the shaft without the shaft rotating. This reduces the time taken to mount an impeller on the shaft and allows for greater torque to be applied when mounting the impeller to the shaft. In addition, using a tool and a rotary cup that is configured to engage with the tool, obviates the need to provide protrusions or a nut on the hub of a turbine wheel in order the hold the shaft in a fixed angular position, and so impedes exhaust gas flow over the turbine hub to a lesser extent.

Brief description of the drawings

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-section through a portion of a known turbocharger; Figure 2 shows a cross-sectional side view of the turbine end of a turbocharger, showing a diesel exhaust fluid delivery tube for dispensing DEF into a known dosing cup; Figure 3 shows a perspective view of a turbine rotary cup according to a first embodiment of the present invention; Figure 4 shows a cross-sectional side view of the turbine rotary cup according to figure 3; Figure 5 shows an end view of a variant of the turbine rotary cup as shown in figures 3 and 4; Figure 6 shows a cross-sectional side view of a turbine rotary cup according to a second embodiment of the present invention; Figure 7 shows an end view of a variant of the turbine rotary cup as shown in figure 6; Figure 8 shows a cross-sectional side view of a turbine rotary cup which is an embodiment of the invention integrally formed in the hub of a turbine wheel, where the interior structure of the rotary cup is not shown but the interior structure may be the same as the structure shown in any of figures 3 to 7; and Figure 9 shows a tool for engaging a turbine rotary cup of the present invention.

Detailed description of the embodiments

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 mounted for rotation, about a turbocharger axis 99, within a chamber defined by a turbine housing 5.

The turbine housing 5 comprises an inlet volute 19 to which gas from an internal combustion engine (not shown) is delivered. The inlet volute 19 defines an annular inlet passageway 9 located annularly around the turbine wheel 4. The turbine housing 5 further comprises an axially extending outlet 20 which defines an outlet passageway 10 that extends axially from, and fluidly connects, the turbine wheel 4 to an outlet port 57.

In use, the exhaust gas flows from the annular inlet passageway 9 to the outlet passageway 10 via the annular inlet passageway 9 and the turbine wheel 4.

The compressor 2 comprises a compressor wheel 6 mounted for rotation, about the turbocharger axis 99, within a chamber defined by a compressor housing 7.

The compressor housing 7 has an inlet 21 that defines an axially extending air intake passage 11 which extends from, and fluidly connects, an inlet port 22 to the compressor wheel 6.

The compressor housing further comprises an outlet volute 23 that defines an annular outlet volute passage 12 that is arranged annularly around the compressor chamber. The outlet volute passage 12 is in fluid communication with a compressor outlet 25.

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 turbocharger shaft 8 rotates on journal bearings 13 and 14 housed towards the turbine end and compressor end respectively of the bearing housing 3. The compressor end bearing 14 further includes a thrust bearing 15 which interacts with an oil seal assembly including an oil slinger 16. Oil is supplied to the bearing housing from the oil system of the intemal combustion engine via oil inlet 17 and is fed to the bearing assemblies by oil passageways 18. The oil fed to the bearing assemblies may be used to both lubricate the bearing assemblies and to remove heat from the bearing assemblies.

In use, the turbine wheel 4 is rotated by the passage of exhaust gas from the annular inlet passageway 9 to the outlet passageway 10. Exhaust gas is provided to the annular inlet passageway 9 from an exhaust manifold (also referred to as an outlet manifold) of the engine (not shown) to which the turbocharger is attached. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet port 22 and the air intake passage 11 and delivers boost air to an inlet manifold of the engine via the outlet volute passage 12 and the outlet 25.

The annular inlet passageway 9 is defined by a portion of the turbine housing 5 which includes a turbocharger mounting flange 27 at the end of the annular inlet passageway 9 remote from the turbine wheel 4.

The turbine wheel 33 can be joined to a turbine shaft using a friction weld. In order to form the friction weld, the turbine wheel 33 is held stationary and the shaft is rotated at a high speed, and is moved towards the back of the hub 36 of the turbine wheel 33, where a center hole may be provided to receive the shaft. Friction between the rotating shaft and the stationary hub 36 of the turbine wheel 33 causes the metals of each component to become extremely hot, reaching temperatures of approximately 1400 degrees Celsius.

Pressure may be applied to urge the turbine wheel 33 and shaft together, causing a friction weld to form between the shaft and the hub 36 of the turbine wheel 33. Other types of weld may be used to join the turbine shaft to the turbine wheel 33, however, a friction weld is advantageous due to reliability of the weld formed, and does not require any fluxes, filler material or gas in order to form the weld.

Figure 2 shows a cross-sectional side view of the turbine end 31 of a possible realization of a turbocharger which is a comparative example. The turbocharger comprises a turbine housing 32 and a turbine wheel 33 mounted for rotation about a turbocharger axis.

A known rotary cup atomizer 34, which may interchangeably be referred to as a dosing cup or rotary cup, is fixedly connected to a central hub 36 of the turbine wheel 33.

Alternatively, the rotary cup may be machined into the hub of the turbine wheel.

When the turbine wheel 33 is driven by exhaust gasses, or any other gas such as air, causing it to rotate, the rotary cup 34 rotates synchronously with the turbine wheel 33. This is because the rotary cup 34 is fixedly connected to the hub of the turbine wheel 33, such that a central axis of the rotary cup atomizer 34 is axially aligned with the turbocharger axis.

A delivery tube 35 is disposed in the rotary cup 34. The delivery tube 35 is operative to deliver from a source or reservoir (not shown) a liquid reductant. The liquid reductant may, for example be, anhydrous ammonia, aqueous ammonia, or urea, all of which may be collectively referred to as Diesel Exhaust Fluid (DEF). The delivery tube 35 is configured such that DEF is injected towards the center of a base of the rotary cup 34 proximate the hub of the turbine wheel 33.

When in use, the rotary cup 34 rotates synchronously with the turbine wheel 33, therefore, when DEF is injected into the rotary cup 34 it becomes distributed on an inner surface of the rotary cup 34. As the rotary cup 34 continues to rotate, the injected DEF that is distributed on the inner surface is ejected from the rotary cup 34 as a fine spray. The rotary cup 34 therefore, promotes atomization DEF received from the delivery tube 35.

The turbine wheel 33, when in use, is driven by exhaust gas from an engine that is connected to the turbocharger. The exhaust gas flow that drives the turbine wheel 33, exits the turbine wheel 33 in a generally axial direction, and flows concentrically around the rotary cup 34.

Accordingly, the atomized DEF that is ejected from the rotary cup 34, mixes with the exhaust gas flow. This mixture of DEF and exhaust gas then passes through a catalyst.

The central hub 36 of the turbine wheel 33 defines protrusions 38 (and/or notches) around its outer circumference, together forming a star boss. A tool can be engaged with the star boss, and used to hold the turbine wheel 33 in a fixed angular position. While the tool is engaged with the star boss, a rotating shaft may be attached to the opposite side of the turbine wheel by a friction weld.

If the protrusions 38 were not provided, the tool would need to provide a higher clamping force in order to prevent rotation and slippage of the central hub; this clamping force could damage central hub, causing deformation of the profile of the hub, which might result in an imbalance of the turbine wheel. Unfortunately, in use the protrusions 38 disturb the gas flow exiting from the turbine wheel 33. Undesirable turbulence can be arise as exhaust gas passes over the star boss 38. When the turbine wheel 33 is used in combination with an SCR system, disrupting the exhaust gas flow may adversely affect the components of the SCR system, downstream of the turbine wheel, such as a catalyst. For these reasons, the protrusions 38 are sometimes machined away after the turbine wheel 33 has been mounted to the shaft 8, such that surface of the central hub 36 is smooth. However, this is time intensive and may inadvertently damage other components of the turbine wheel 33.

Forming the rotary cup 36 to be large enough to be effective, makes it harder to access the protrusions 38, making them less suitable, or even ineffective, for preventing rotation of the turbine wheel 33 as the turbine wheel 33 is mounted to the shaft 8. Conversely, making the rotary cup 36 small enough to allow access to the protrusions 38 makes the rotary cup 36 less effective.

Referring now to Figure 3, there is shown a rotary cup 40 according to a first embodiment of the invention. The rotary cup 40 is suitable for rotation about a turbine axis, the rotary cup 40 comprises a base 41. The base 41 of the rotary cup 40 is a circular wall of uniform thickness with the centre of the wall normal to a central axis, A, of the cup. The central axis A is for alignment with a turbine axis. The rotary cup 40 further comprises a frustoconical wall 43 which is disposed concentrically to the central axis A, and extends from the base 41. The wall 43 diverges from the central axis A in a direction away from the base 41, resulting in the diameter of the cup increasing linearly from the base 41. In other non-depicted embodiments the wall 43 of the rotary cup 40 may be bell shaped, cylindrical or any other suitable shape. An edge 42 of the wall 41 distal from the base defines an open side 50 of the rotary cup 40, shown in Figure 3. It is from the edge 42 of the open side 50 that the majority of the DEF will be ejected from the cup as a fine spray when in use.

The frustro-conical shape of the rotary cup atomizer 40 promotes atomization of the DEF while allowing the closed side 41 to be suitably sized such that it can be fixedly attached to the hub of the turbine wheel 3, or integrally formed in the hub of a turbine wheel 3, as described in further detail below.

The wall 43 of the rotary cup 40 further defines an inner surface 44 (which in use faces generally away from the turbine wheel) and an outer surface 45. As described above, when in use, exhaust gas flow from the turbine wheel 33 passes concentrically over the rotary cup 40 and so passes over the outer surface 45 of the wall 43. Any DEF that is injected into the rotary cup atomizer 40 is forced on to the inner surface 44 of the wall 43 before being ejected from the rotary cup 40 at the open side 50 due to the rotation.

The inner surface 44 comprises a plurality of recesses, a plurality of protrusions or a combination of both. A protrusion means an area of the inner surface 44 which is closer to the central axis A than other portions of the inner surface at the same axial position along the central axis A, while a recess means an area of the inner surface 44 which is further from the central axis A than other portions of the inner surface at the same axial position along the central axis A. In either case the "other portions" may be frusto-conical portions of the inner surface 44, or portions which of the inner surface 44 which are at the average distance from the central axis A where the average is over the circumference of the inner surface 44 at that same position along the central axis A. Providing a plurality of protrusions or recesses increases the surface area of the inside of the rotary cup 40, compared to if they were not provided, increases the drag coefficient of the interior of rotary cup 40. The presence of recesses and/or protrusions on the inner surface 44 of the rotary cup 40 provides an increased mechanical interaction between the inner surface 44 of the rotary cup 40 and DEF, or any other liquid, that is provided in the rotary cup 40. Further, the recesses, and/or protrusions help to reduce fluid slippage and provide increased momentum to the DEF, further improving atomization of the DEF as it leaves the rotary cup 40.

By way of example, the plurality of protrusions may be a plurality of ribs or a plurality of fins, extending from the inner surface 44 towards the central axis A. In other embodiments, the protrusions may be a plurality of convex dimples formed on the inner surface 44. Further, the plurality of recesses by way of example may be a plurality of grooves, and/or a plurality of concave dimples formed on the inner surface 44 of the wall 43.

The rotary cup 40 of the first embodiment, as shown in Figures 3 and 4 and a variant as shown in Figure 5 comprise a plurality of groves 46. The wall 43 defines the grooves 46 as depressions in inner surface 44 of the wall 43. The grooves 46 may be formed during a casting process of the rotary cup 40, or they may be machined into the inner surface 44 of the rotary cup 40. The grooves 46 extend from the edge 42 of wall 43 towards the base 41. The grooves 46 do not extend completely to the base 41, such that there is a portion of the wall 43 provided proximate the base 41 where the grooves 46 are not provided and where the inner surface 44 is circular at any given position along the central axis A. In other embodiments, the grooves may extend to the base 41 of the rotary cup 40. The portions of the inner surface 44 between pairs of neighboring grooves 46 are frusto-conical and referred to as "lands".

The wall 43 has a thickness, T, defined at the open side 50 of the rotary cup 40 and is the substantially constant distance at the lands from the inner surface 44 to the outer surface 45.

Each groove 46 extends in a direction from the inner surface 44 towards the outer surface 45, defining a groove depth, GD. The maximum depth, GD, of each groove 46 is smaller than the thickness, T, such that the outer surface 45 of the wall 43 is a smooth surface to minimise any disturbance to exhaust gas flow. The maximum depth, GD of each groove is constant along the length of the groove 46. In other words, the maximum depth, GD, of a groove 46 at a point along its length proximate the edge 42 will be the same as the maximum depth of the groove 46 at a point along its length proximate the base 41, and at any point in between. The maximum groove depth, GD, is measured in a straight line from the point of the groove that is most recessed, to where the inner surface 44 would be (at the same position along the central axis A and the same circumferential positions around the axis A) if the groove 46 were not present. For example, if the surface of the groove 46 were formed as a section of a cylinder, as is in the first embodiment, the end profile of the groove 46 would be a circular arc, and the most recessed point would be at the center of the arc.

As described above, the grooves 46 extend from the edge 42 towards the base 41 and each have a groove length, GL. The groove length, GL, is measured along the length of the groove 46.

In the first embodiment, the plurality of grooves 46 each have the same groove length, GL, however in other embodiments, the plurality of grooves 46 may have differing groove lengths, GL, e.g. such that each groove 46 may have a different respective groove length, GL.

The rotary cup 40 can also be considered to have a length, L, which is measured from the open side 50 to the base 41 of the rotary cup 40, parallel to the central axis A. Further, the edge 42 of the rotary cup 40 defines an outermost diameter of the rotary cup 40. The outermost diameter, OD, is the diameter formed by the lands of inner surface 44 of the rotary cup 40 at the edge 42 of the wall 43. The ratio of the groove length, GL, to the outermost diameter, OD, (GUOD) is between 0.8 and 2. It may be advantageous for GUOD to be between 0.9 and 1.5, or it may be advantageous for GL/OD to be substantially equal to 1.

The grooves 46 may be straight grooves, meaning the grooves 46 have no circumferential component, as in Fig. 4. As can also be seen in Figure 3, the surfaces of grooves 46 of the first embodiment can be considered to be part of a circular cylinder.

Figure 5 shows an end view of a variant of the rotary cup 40 as shown in Figures 3 and 4, using like reference numerals to label like items items. It can be seen from Figure 5 that the grooves 46 in this variant of the first embodiment are helical. Helical grooves, which may also be known as conical helical grooves, are grooves in which at each point along the groove the extension direction of the groove (e.g. the direction which is transverse to the semi-circular cross-section of the groove) of the groove 46 is not co-planar with the central axis A and forms a constant angle with respect to the central axis A, such that the extension direction of each groove 46 has a circumferential component. Without wishing to be bound by any particular theory, it is envisaged that helical grooves further reduce fluid slippage and increase the momentum of DEF that is injected into the rotary cup 40 when in use, further promoting break down of the liquid and atomization of the OFF when exiting the rotary cup 40.

Eight grooves 46 are provided in the variant of Fig. 5, but a different number of grooves are provided in other embodiments. Typically, there may be at least two grooves 46 and a maximum of twelve grooves 46. The grooves 46 are equally distributed about the central axis, A. There does not necessarily need to be an even number of grooves 46, but there must be at least two grooves 46, and the grooves 46 should be equally spaced to ensure that the rotary cup atomizer 40 is balanced, meaning that the center of mass of the rotary cup 40 lies on the axis of rotation, A. If the grooves 46 are not equally spaced about central axis, or if only one groove 46 is provided, the center of mass of the rotary cup 40 would not lie on the axis of rotation, A, which can cause excessive noise and undesirable vibrations. The life of the bearings which support a turbine shaft, to which the rotary cup 40 may be connected to via a turbine wheel 33 may also decrease if the center of mass does not lie on the axis of rotation.

When viewing, the rotary cup 40 from the open side 50 looking towards the base 41, the profile of each groove 46 is an arc. The profile of the grooves 46 is constant along the length of the groove 46. In other embodiments, the end profile of a groove 46 may be a square, rectangle, triangle or any other suitable polygonal shape. A rotary cup may comprise a plurality of grooves 46 where the end profile of at least one of the grooves 46 is different to at least one of the other grooves 46.

A second embodiment of a rotary cup 40 will now be considered, as shown in Figure 6. Like reference numerals are used for like features.

The rotary cup 40 comprises a base 41. The base 41 is a circular base having a central axis A, for alignment with a turbine axis. The rotary cup 40 further comprises a frusto-conical wall 43 which is disposed concentrically to the central axis A, and extends from the base 41. The wall 43 diverges from the central axis A in a direction away from base 41, resulting in the diameter of the cup increasing linearly from the base 41. An edge 42 of the wall 43 distal from the base 41 (indeed, furthermost from the base 41) defines an open side 50 of the rotary cup 40. It is from the open side 50 that DEF will be ejected from the cup as a fine spray when in use, as set out above in relation to the first embodiment.

The wall 43 further defines an inner surface 44 and an outer surface 45. The rotary cup comprises a plurality of grooves 46 that are integrally formed as part of the wall 43. The grooves 46 extend from the edge 42 of the wall 43 towards the base 41. The grooves 46 do not extend completely to the base 41, such that there is a portion of the wall 43 provided proximate the base where the grooves 46 are not provided.

The wall 43 has a thickness, T, defined at the open side 50 of the rotary cup 40 and is the distance from the lands of inner surface 44 to the outer surface 45.

Each groove 46 is a recess compared to the neighboring lands in a direction from the innersurface 44 towards the outer surface 45, defining a groove depth, GD. The maximum depth, GD, of each groove 46 is smaller than the thickness, T, such that the outer surface 45 of the side wall 43 is a smooth surface, so as to minimize any disturbance to exhaust gas flow. The maximum depth, GD, of each groove 46 is constant along the length of the groove 46.

Also provided in the rotary cup 40 is at least one groove 46 where the groove depth, GD is smaller than the thickness, T, of the rotary cup 40, and is constant along the majority of its length, but increases at a point proximate the open side 50, to have a groove depth, GD equal to the thickness, T, of the rotary cup 40 and effectively forming a slot 58 in the wall 43 at the open side 50 of the rotary cup 40.

It is to be noted that the second embodiment can be considered to comprise all of the same features as described above in relation to the first embodiment save as for the differences noted above.

Also provided in the rotary cup 40 of the second embodiment is a through-hole 70, shown in Figure 6. The through-hole 70 is a channel or passage provided in the wall 43 of the rotary cup 40 at a point along the length of rotary cup 40 between the base 41 and the open side 50. The through-hole 70 is often provided such that it is equidistant from the open side 50 and the base 41.

Figure 6 shows two through-holes 70, that lie in the same circumferential plane of the rotary cup 40 (that is, a plane including the central axis A) There are a minimum of two through-holes 70, or there may be up to 24 through-holes 70. One or more of the through holes 70 may be in register with one of the grooves 46, or with a land between the grooves 46. Where there are 24 through-holes, the through-holes may be disposed such that there is one in each groove 46 and one in each land between the grooves 46. Further, when more than two through-holes 70 are provided, the through-holes 70 do not necessarily need to lie on the same circumferential plane, however, the through-holes are provided such that the center of mass of the rotary cup 40 lies on the central axis, A. The through-holes 70, in a similar manner to the slots 58 allow for injected DEF to exit the rotary cup 40 upstream of the DEF exiting from the open side 50. Again, this aids in further promoting mixing of the DEF that is injected into the rotary cup 40 with the exhaust gas flow when in use. The through-hole 70 can also be considered to form a discontinuity in the inner surface 44 of the rotary cup 40. Providing a discontinuity encourages liquid breakdown of the DEF that is injected into the rotary cup 40, and thus further promotes atomization of the DEF leaving the rotary cup 40 and improves mixing of the DEF with the exhaust gas flow.

Figure 7 shows an end view of a variant of the rotary cup 40 according to the second embodiment. It this variant, as in that of Fig. 5 the grooves 46 have a helical form. It can be seen that the slots 58 formed by the grooves 46 not only allow fluid to exit the rotary cup 40 in a generally axial direction, but also allow fluid to exit from the rotary cup 40, as a fine spray, in a generally radial direction. Providing the slots 58, not only further promotes atomization of DEF injected into the rotary cup 40, but further promotes mixing of the injected DEF with the exhaust gas flow from the turbine wheel 3 when in use. The slots 58 provide for a portion of the liquid to mix with exhaust gas flow upstream of the spray of liquid that exits the rotary cup at the open side 50.

As shown in Figure 7, the rotary cup 40 has six grooves 46 where the groove depth, GD is constant along the length of the groove 46, and two grooves 46 where the depth of the groove 46 increases proximate the open side 50 so as to form a slot in the wall. In other embodiments any number of the grooves 46, may be grooves 46 where the depth increases proximate the open side 50, so long as the maximum number of grooves 46, does not exceed twelve, and there are at least two grooves 46.

Figure 8 shows a cross-sectional side view of a turbine portion of a turbocharger which is an embodiment of the invention, integrally formed in the hub 36 of a turbine wheel 33. The turbine wheel may be a component of a turbocharger which is generally the same as the known turbocharger of Figure 1. The turbine wheel 33 and the cup 40 may be formed together by a moulding and/or machining process as a single body. In another example the turbine wheel 33 and the rotary cup 40 may be formed by additive manufacturing; as a single integral component.

The turbine wheel 33 defines a central hub 36, on which turbine blades are fixedly attached. The turbine axis passes through the center of the central hub 36. As noted above, the rotary cup 40 is integrally formed in the central hub 36. The central hub 36 defines a base 41 and a wall 43 of the rotary cup 40. A delivery tube 35 is shown provided in the rotary cup 40 operative to inject DEF towards the base 41 of the rotary cup 40.

The interior structure (not shown) of the rotary cup 40 may be the same as the structure of the first or second embodiments as shown in figures 3 to 7. The turbine wheel 33 is provided in a turbine housing 32 and is mounted to a shaft 8 for rotation about a turbine axis. It can also be seen in Figure 8, that when the rotary cup according to the first or second embodiments is used, it is no longer necessary to provide protrusions 38 allowing the hub 33 of the turbine wheel to have a smooth outer surface reducing the disturbance on flow exiting the turbine wheel.

In a variant, the cup 40 may be formed separately from hub 36 of the turbine wheel 33 (e.g. as shown in Figs. 3-7), by moulding and/or machining, or one or both may be additively manufactured. The base 41 of the rotary cup 40 may be mounted to the hub 36, such that the central axis, A of the rotary cup 40 is coincident with the turbine axis.

Because the rotary cup 40 is positioned on the central hub 36 of a turbine wheel 33, the rotary cup, 40 impedes the exhaust gas flow that exits the turbine wheel 33, in particular because the wall 42 of the rotary cup 40 diverges from the base 41 towards its open side 50. However, the rotary cup 40 of the present invention can have a smaller outer diameter, OD, for the same flow conditions a known rotary cup 34, as depicted in Figure 2, wherein the interior of the cup 34 is smooth. This is because the protrusions and/or recesses that are provided on the inner surface 44 of the rotary cup 40 according to the present invention further promote liquid breakdown and thus atomization of liquid exiting from the rotary cup 40, accordingly in order to achieve the same liquid breakdown the rotary cup 40 may have a smaller outermost diameter, OD when compared to a known rotary cup 34.

By providing a rotary cup 40 which impedes exhaust gas flow less than a known rotary cup 34, reduces the adverse effect that the rotary cup 40 may have on the performance of the components of an SCR exhaust gas after treatment system that are provided downstream of the rotary cup 40, such as the catalyst.

Figure 9 illustrates a tool 100 for engagement with the rotary cup 40 according to the present invention. As discussed above, the rotary cup 40 according to the present invention comprises a plurality or protrusions and/or a plurality of recesses. The surface of the tool 100 is complementary to the inner surface 44 of the rotary cup 40, such that the tool 100 comprises a plurality of recesses and/or protrusions. In this sense, the plurality of recesses and/or protrusions of the tool 100 will correspond in shape and size to the recesses and/or protrusions of the rotary cup 40. As such, when the tool 100 is inserted into the rotary cup 40, the recesses and/or protrusions of the rotary cup 40 interlock with the corresponding recesses and/or protrusions of the tool 100. The interlocking of the recesses and/or protrusions of the rotary cup 40 with those of the tool 100 prevent relative rotation of the rotary cup 40 and the tool 100 about the central axis, A The tool 100 of Fig 9 is adapted for engagement with a rotary cup 40 according to Figs. 3-4 or Fig. 6. The tool 100 has an exterior surface 103 for insertion into the inner surface 44 of the cup 40. The surface 103 defines a plurality of ridges 105 that extend along at least a portion of a length of the tool 100 and correspond to the grooves 46 of the rotary cup 40. The ridges 105 are disposed such that they are operative to slot into the plurality of grooves 46 of the rotary cup 40.

In variants, the tool 100 has a different number of ridges 105, which may also have a different shape (e.g. a helical shape) to match the rotary cup 50. That is, the tool 100 typically comprises at least two ridges 105, and a maximum of twelve ridges 105. The tool 100 typically has the same number of ridges 105 as the number of grooves 46 of the rotary cup 40. However, the tool may comprise fewer ridges 105 than grooves 46 of the rotary cup 40, provided that the ridges 105 that are defined by the surface 103 of the tool 100 are spaced such that they can be aligned with the grooves 46 of a corresponding rotary cup 40, and prevent relative movement of the rotary cup 40 and the tool 100 about the central axis, A, when the tool 100 is provided in the rotary cup 40.

The rotary cup 40 of the present invention, when either fixedly attached to a central hub 36 of the turbine wheel 33, or integrally formed as part of the central hub 36, can be used in combination with the tool 100 to hold a turbine wheel 33 at a fixed angular position.

In particular, the tool 100 may be used in a method of joining a shaft to a turbine wheel 33 provided with a rotary cup 40 according to the present invention, such that the rotational axis of the turbine wheel 33 is coincident with the central axis, A, of the rotary cup 40. The method comprises a first step of inserting the tool 100 into the rotary cup 40. As set out above the tool 100 comprises a plurality of recesses and/or protrusions which correspond to the plurality of recesses and/or protrusions of the rotary cup 40. When the tool 100 is inserted into the rotary cup 40 the protrusions and/or recesses of the tool 100 interlock with the corresponding recesses and/or protrusions of the rotary cup 40 to prevent relative rotation of the rotary cup 40 and the tool 100 about the central axis, A. Because the rotary cup 40 has a fixed angular relationship to the turbine wheel 33, holding the tool 100 in a fixed angular position prevents rotation of the rotary cup 40 and thus prevents rotation of the turbine wheel 33. A shaft can then be rotated about an axis which coincides with the rotational axis of the turbine wheel, and with the central axis, A, of the rotary cup 40. The shaft, as it rotates, is moved along the axis from the side of the turbine wheel 33 opposite the rotary cup 40 towards the turbine wheel 33, thereby forming a friction weld between the shaft and the turbine wheel 33. When the friction weld has been formed the tool 100 can be removed from the rotary cup 40.

A specific method which is an embodiment of connecting a turbine wheel to a shaft will now be described. This method is applicable to any of the rotary cups 40 described above, when the tool 100 has protrusions corresponding to the grooves of the rotary cup 40.

A first end 107 of the tool 100 is aligned with the open side 50 of the rotary cup 40, and the ridges 105 of the tool 100 are aligned with the grooves 46 of the rotary cup 40. Once the ridges 105 are aligned with the grooves 46, the tool 100 is moved in a direction towards the base 41 of the rotary cup 40. As the tool 100 moves towards the base 41 the ridges 105 are guided by the grooves 46. If the grooves 46 of the rotary cup are straight grooves 46, the tool 100 when moving towards the base 41 will move in a purely axial direction. However, if the grooves 46 of the rotary cup 40 are helical grooves as the tool 100 moves towards the base 41 of the rotary cup 40, the tool 100 will also undergo a rotational movement, as the ridges 105 of the tool 100 are guided by the helical grooves 46 of the rotary cup 40.

Accordingly, when the first end 107 of the tool 100 is proximate the base 41 of the rotary cup 40, the tool 100 cannot rotate independently of the rotary cup 40. The tool 100, can therefore be considered to have engaged with the rotary cup 40, because the ridges 105 of the tool 100 have interlocked with the grooves 46 of the rotary cup 40. Once the tool 100 is engaged with the rotary cup 40, the tool 100 is held in a fixed angular position.

Holding the tool 100 in a fixed angular position prevents the rotary cup 40 from rotating relative to the tool 100, and thus prevents the central hub 36 and turbine wheel 33 from rotating relative to the tool 100. The tool 100 can thus be used to hold the turbine wheel 33 when a shaft is being joined either by friction welding or any other suitable form of welding. The shaft can be joined to the turbine wheel 33 by rotating the shaft about an axis which coincides with the rotational axis of the turbine wheel 33 and then moving the shaft along the axis from the side of the turbine wheel 32 opposite the rotary cup 40 towards the turbine wheel 33, thereby forming a friction weld between the shaft and the turbine wheel 33.

Once the turbine wheel 33 is fixedly joined with the shaft, the tool 100 can simply be removed from the rotary cup 40 by moving the tool in a direction away from the base 41.

The method of connecting a turbine wheel 33 to a shaft as described above can be used in the instance where the rotary cup 40 is integrally formed in the hub 36 of the turbine wheel 33 such that the hub 36 defines the base 41 and the wall 43 of the rotary cup 40, or where the base 41 of the rotary cup 40 is fixedly connected to the turbine wheel 33. In both instances, the rotary cup 40 always has a fixed angular relationship relative to the turbine wheel 33.

Using a rotary cup 40 according to the present invention in combination with the tool 100 for mounting a shaft to a turbine wheel 33, where the rotary cup 40 is provided in a fixed angular position relative to the turbine wheel 33 as described above, obviates the need for any protruding features such as a star boss to be provided on the surface of the central hub 36. Therefore, the surface of the central hub 36 can be a smooth surface with reduced aerodynamic drag compared to a hub where protruding features are present.

As described above in relation to the embodiments shown in Figures 3 to 7, the groove length, GL, of each of the grooves 46 defined by the inner surface 44 of the rotary cup 40 is suitable for promoting liquid breakdown and atomization of DEF that is injected into the rotary cup 40. When the rotary cup 40 is being used in combination with the tool 100 in order to aid in mounting a shaft to a turbine wheel 33, the length of each groove, GL, is long enough for the ridges 105 of the tool 100 to engage with the grooves 46 of the rotary cup 40. Further, the maximum depth, GD, of each groove 46 is also deep enough for the ridges 105 to engage with the grooves 46. If the length of the grooves, GL, is too short, or the maximum depth, GD, of each groove 46 is too shallow, the ridges 105 of the tool 100 may not be able so successfully to engage with the grooves 46 and the tool 100 may be unable to hold the rotary cup 40 in a fixed angular position so securely.

Optionally, before the tool 100 is removed from the rotary cup 40 it may be used to mount an impeller to a second end of the shaft 8, opposite a first end of the shaft where the turbine wheel 33 is mounted. A first way of mounting the impeller would be by friction welding, by positioning a central rotational axis of the impeller on the rotational axis of the turbine wheel proximate the second end of the shaft, rotating one of the impeller and the tool 100 about the axis of the shaft (i.e. rotating the impeller and tool 100 relative to each other) and them forcing the impeller against the first end of the shaft. The tool 100 would prevent the shaft 8 from rotating relative to the tool 100.

Alternatively, the second end of the shaft may comprise an end portion with a threaded outer surface. The turbine wheel 33, and hence the shaft 8, are held in a fixed angular position by the tool 100. The end portion of the shaft is the passed through a central aperture in the impeller, and a lock component such as a lock nut may be positioned on the shaft to lock the impeller to the shaft. Once the impeller is mounted to the shaft 8, the tool 100 may be removed from the rotary cup 40, such that the shaft 8 with the turbine wheel 33 mounted to a first end and the impeller mounted to the second end, can rotate about the central axis of the shaft.

In some instances, the shaft may be provided in the housing of a turbocharger, before the impeller is mounted to the impeller end of the shaft 8. Once the impeller is mounted to the shaft 8, the shaft cannot be removed from the turbocharger housing.

In a further optional step, before the turbine wheel 33 is friction welded to the shaft 8, the rotary cup 40, in the case it is formed separately from the turbine wheel 33, could be friction welded to the turbine wheel 33 by holding the cup 40 with the tool 100 located within the cup 50 and engaged with the cup 50, and then rotating one of the tool 100 and turbine wheel 33 about the axis of the turbine wheel 33, and forcing the base of the cup 40 against the hub of turbine wheel. Optionally, this process for connecting the cup 40 to the hub of the turbine wheel 33 could be carried out other than as preliminary to the method described above for mounting the turbine wheel to the shaft 8. For example, the rotary cup 40 could be friction welded to the turbine well 33 after the turbine wheel 33 is connected to the shaft 8 by another method from the one described above.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modification that come within the scope of the inventions as defined in the claims are desired to be protected. In relation to the claims, it is intended that when words such as "a", "an" or "at least one" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim.

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

Claims

CLAIMS1. A rotary cup for rotation about a turbine axis comprising: a base having a central axis coincident with the turbine axis; a wall disposed concentrically to the central axis, extending from the base and diverging from the central axis in a direction away from the base; wherein an edge of the wall distal from the base defines an open side of the cup; and the wall further defining an inner surface facing the central axis, wherein the inner surface defines a plurality of protrusions and/or recesses.
2. A rotary cup according to claim 1 wherein the plurality of protrusions are a plurality of fins, extending from the inner surface of the cup in a direction towards central axis.
3. A rotary cup according to claim 1, wherein the plurality of recesses are a plurality of grooves, the grooves extending from the edge of the wall towards the base.
4. A rotary cup according to claim 3, wherein at least one groove is a straight groove
5. A rotary cup according to claim 3 or claim 4, wherein at least one groove is a helical groove.
6. A rotary cup according to any of claims 3 -5, wherein a maximum depth of each groove is constant along the length of the groove.
7. A rotary cup according to any of claims 3 -6, wherein the profile of at least one of the grooves in a plane parallel to the open side of the cup is an arc.
8. A rotary cup according to any of claims 3-7, wherein the number of grooves is less than or equal to 12.
9. A rotary cup according to any of claims 3-8, wherein the plurality of grooves are equally spaced about the central axis.
10. A rotary cup according to any of claims 6-9, wherein the open side of the cup has an outermost diameter, OD; each groove has a groove length. GL, and the ratio of the groove length, GL, to the outermost diameter, OD, is between 0.9 and 2
11. A rotary cup according to any of claims 6-10, wherein the wall at the open side of the cup has a thickness, T; and the depth of at least one of the grooves increases proximate the open side, to be equal to the thickness, T, forming a slot in the wall at the open side of the cup.
12. A rotary cup according to any of claims 3-11, wherein at least one through-hole is provided in the wall, extending from the inner surface to an outer surface of the cup.
13. A rotary cup according to any preceding claim, wherein the cup is integrally formed in a hub of a turbine wheel; the hub defining the base and the wall.
14. A turbine comprising: a turbine housing having an inlet and an outlet; a turbine wheel mounted in the turbine housing between the inlet and the outlet for rotation about a rotational axis; wherein the turbine wheel comprises a hub and the hub defines a rotary cup according to any of claims 1 to 12.
15. A tool for engagement with the rotary cup according to any of claims 3-13, wherein a surface of the tool defines a plurality of ridges operative to slot into the plurality of grooves of the cup.
16. A method of connecting a turbine wheel to a shaft, the turbine wheel having a rotational axis and having a fixed angular relationship to a rotary cup according to any of claims 1 -12 with the rotational axis of the turbine wheel coinciding with central axis of the cup; the method comprising: inserting a tool into the cup, the tool comprising a plurality of recesses and/or protrusions corresponding in shape and size to the recesses and/or protrusions of the cup, and the insertion causing corresponding recesses and/or protrusions of the cup and tool to interlock to prevent relative rotation of the cup and tool about the axes; holding the tool in a fixed angular position; rotating the shaft about an axis which coincides with the rotational axis of the turbine wheel and moving the shaft along the axis from the side of the turbine wheel opposite to the cup towards the turbine wheel, thereby forming a friction weld between a first end of the shaft and the turbine wheel; and removing the tool from the cup.
17. A method of connecting a turbine wheel to a shaft according to claim 16, wherein the plurality of recesses of the cup are a plurality of grooves extending from the edge of the wall towards the base; and the plurality of protrusions of the tool are a plurality of ridges, each ridge extending along at least a portion of a length of the tool; and wherein inserting the tool into the cup comprises aligning the ridges of the tool with the grooves of the cup then moving the tool in a direction towards the base of the rotary cup.
18. A method of connecting a turbine wheel to a shaft according to claim 16 or claim 17, wherein the turbine wheel comprises a hub, and the cup is integrally formed in the hub; the hub defining the base and the wall of the cup
19. A method of connecting a turbine wheel to a shaft according to claim 16 or claim 17, wherein the turbine wheel comprises a hub, and the base of the cup is fixedly connected to the hub of the turbine wheel.
20. A method of connecting a turbine wheel to a shaft according to any of claims 16 - 19, wherein the method further comprises, subsequent to connecting the turbine wheel to the shaft, mounting an impeller to a second end of the shaft opposite the first end of the shaft while the tool is located in the cup and engaged with the cup.