CN111980758A

CN111980758A - Method for producing a two-vane nozzle ring assembly for a turbocharger with a two-scroll turbine housing

Info

Publication number: CN111980758A
Application number: CN202010441942.9A
Authority: CN
Inventors: F.埃克尔; P.普日比尔; P.斯卡拉
Original assignee: Garrett Transportation I Inc
Current assignee: Garrett Power Technology (Shanghai) Co.,Ltd.
Priority date: 2019-05-24
Filing date: 2020-05-22
Publication date: 2020-11-24
Also published as: EP3741960A1; EP3741960B1

Abstract

The present invention relates to a method for manufacturing a double vane nozzle ring assembly for a turbocharger with a double scroll turbine housing for directing exhaust gas from each scroll member onto a turbine wheel in an interleaved manner. A two-bladed nozzle ring for a turbine nozzle of a turbocharger nozzle ring is manufactured by assembling the nozzle ring from three separately formed parts. The central portion includes a first ring of circumferentially spaced first vanes and a second ring of circumferentially spaced second vanes, the first and second rings being axially spaced and integrally joined to one another. The first vane is circumferentially offset from the second vane, and the outlet of the first vane passage is radially aligned with and circumferentially staggered from the outlet of the second vane passage. The first and second side walls are provided as separate portions. Finally, a first sidewall is joined to the distal or outer surface of the first ring and a second sidewall is joined to the distal surface of the second ring to complete the assembly.

Description

Method for producing a two-vane nozzle ring assembly for a turbocharger with a two-scroll turbine housing

Technical Field

The present disclosure relates to turbochargers in which the turbine of the turbocharger is driven by exhaust gas from a reciprocating engine. The present invention more particularly relates to a turbine housing that is divided into a plurality of substantially separate sections, each section being fed by a separate exhaust system.

Background

Exhaust gas driven turbochargers are devices used in conjunction with internal combustion engines to increase the power output of the engine by compressing the air delivered to the intake of the engine to be mixed with fuel and combusted in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and yet another center housing is connected between the turbine housing and the compressor housing for receiving the shaft bearings. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle leading from the chamber to the turbine wheel. Exhaust gas flows from the chamber through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. The turbine thus extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through an inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

In multi-piston reciprocating engines, it is known to design the exhaust system in such a way as to take advantage of the pressure pulsations that occur in the exhaust stream. In particular, it is known to employ so-called "pulse separation" in which the cylinders of the engine are divided into groups and pulses from each group of cylinders are substantially isolated from pulses from other groups by having separate exhaust passages for each group of cylinders. To take full advantage of the benefits of pulse separation, it is desirable to minimize communication or "cross talk" between the separate cylinder banks. In the case of turbocharged engines, it is therefore advantageous to always keep separate exhaust gas passages into the turbine of the turbocharger. Thus, the turbine housing into which the exhaust gas is fed is typically divided into a plurality of substantially separate portions.

There are two basic ways of dividing the turbine housing: (1) sector division and (2) meridian division. In a sectorised turbine housing, the generally annular chamber is divided into angular sectors, each occupying only a portion of the circumference, such that the passages are continuous with one another in the circumferential direction, such as shown in figure 2 of us patent No. 6,260,358. Sectorization of the turbine housing is advantageous from a flow separation point of view, but out of phase exhaust pulses from the two sectors may cause undesirable turbocharger shaft movement.

In a meridian-divided turbine housing, a scroll or chamber that surrounds a turbine wheel and supplies exhaust gas thereto is divided into a plurality of scrolls that are continuous with one another in the axial direction, each of the scrolls occupying substantially the entire circumference, such as shown in fig. 4 of U.S. patent No. 4,027,994. The meridional division of the turbine housing is advantageous from an axial motion perspective, but the exhaust flow from each scroll member impinges less than the full axial width of the leading edge of the turbine blade, which negatively impacts turbine efficiency due to mixing losses.

The present disclosure relates to turbochargers having turbine housings of the meridian dividing type.

Disclosure of Invention

The present disclosure relates to turbochargers having meridionally divided scrolls, and in particular to methods for manufacturing a two-bladed nozzle ring that allows separate exhaust gas flows from the two scrolls to be blown onto the turbine wheel in an interleaved manner around the circumference of the wheel. According to embodiments described and illustrated herein, a method for manufacturing a two-bladed nozzle ring assembly for a turbine nozzle of a turbocharger comprises the steps of:

(a) providing a first sidewall as an annular portion;

(b) providing a second sidewall as the annular portion, the second sidewall being formed separately from the first sidewall;

(c) providing a nozzle ring spaced from the first and second sidewalls, wherein the nozzle ring is configured with a first vane ring comprising first vanes circumferentially spaced apart around a circumference of the nozzle ring and is configured with a second vane ring comprising second vanes circumferentially spaced apart around the circumference of the nozzle ring, the first and second vane rings being axially spaced apart and integrally joined to one another, the first vane ring defining first vane passages between circumferentially successive first vanes and the second vane ring defining second vane passages between circumferentially successive second vanes, wherein the first vane passages have respective first vane passage inlets and first vane passage outlets, wherein the second vane passages have respective second vane passage inlets and second vane passage outlets, wherein the first vanes are circumferentially offset from the second vanes, the first vane channel inlet is axially spaced from the second vane channel inlet, and the first vane channel outlet is radially aligned with and circumferentially staggered from the second vane channel outlet; and

(d) the first sidewall is joined to the distal face of the first vane ring and the second sidewall is joined to the distal face of the second vane ring.

Because each of the two vane rings blows exhaust gas straight on the turbine wheel about its circumference and the jets from the first and second vane passages are staggered about the circumference, the nozzle ring assembly manufactured according to the method of the present invention may alleviate shaft motion and mixing loss problems that may affect some prior art turbines of the segmental and meridional types. A nozzle ring assembly made in accordance with the present invention can maintain good flow isolation between the two exhaust gas streams up to the turbine wheel, thereby fully utilizing and separating the exhaust manifold pressure pulses.

In some embodiments, symmetry may exist between the first vane channel and the second vane channel in that the first vane channel and the second vane channel have respective flow areas that are substantially equal. However, in other embodiments, the flow area of the first vane passage may be different from the flow area of the second vane passage such that one scroll member contributes a greater portion of the total exhaust flow than the other scroll member, while the volumes of the first and second scroll members may alternatively be equal.

In some embodiments, the first vane passages may be configured such that each first exhaust jet impinges the entire extent of the turbine blade leading edge, and similarly, the second vane passages may be configured such that each second exhaust jet impinges the entire extent of the turbine blade leading edge. In other embodiments, each of the first and second vane channels may be configured such that the first and second exhaust jets impinge less than an entire extent of the leading edge.

According to one embodiment of the invention, the first sidewall may comprise a plurality of recessed blade receptacles in a face of the first sidewall facing the distal end face of the first blade ring, each said recessed blade receptacle receiving a distal end of a respective first blade. Similarly, the second sidewall may include a plurality of recessed blade receptacles in a face of the second sidewall facing the distal end face of the second blade ring, each said recessed blade receptacle receiving a distal end of a respective second blade.

The nozzle ring may be manufactured by an injection molding process, one non-limiting example of which is a Metal Injection Molding (MIM) process.

The assembly of the first and second side walls with the nozzle ring may be achieved by the use of pins. In one embodiment, each side wall and two opposed distal end faces of the nozzle ring are provided with pin receptacles, the pin receptacles in each side wall being aligned with corresponding pin receptacles in the respective face of the nozzle ring. The pins are press fit into the pin receptacles in each face of the nozzle ring and the pin receptacles of each sidewall to complete the assembly.

In another embodiment, the first vane ring and the second vane ring include integrally formed pins that project from each of the opposing distal end faces of the nozzle ring, and the side walls include pin receptacles. The pin is inserted into a pin receptacle in the sidewall and then secured therein, such as by riveting or any other suitable fastening technique.

Drawings

Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is an axial cross-sectional view of a turbocharger having a two-vane nozzle ring assembly that may be made by a method according to the present invention;

FIG. 2 is an isometric view of a nozzle ring assembly according to a first embodiment of the present invention;

FIG. 3 is an exploded view of a nozzle ring assembly according to a first embodiment of the present invention;

FIG. 4A is an isometric view of a nozzle ring component of the nozzle ring assembly of the first embodiment;

FIG. 4B is another isometric view of the nozzle ring member of the first embodiment;

FIG. 5A is an exploded view of the first and second sidewalls of the nozzle ring assembly of the first embodiment;

FIG. 5B is another exploded view of the first and second sidewalls of the first embodiment;

FIG. 6 is a schematic end view of the nozzle ring assembly for explaining the location of the cross-sectional views of FIGS. 7 and 8;

FIG. 7 is a cross-sectional view of the nozzle ring assembly taken along line 7-7 of FIG. 6 in accordance with the first embodiment of the present invention;

FIG. 8 is a cross-sectional view of the nozzle ring assembly taken along line 8-8 of FIG. 6 in accordance with the first embodiment;

FIG. 9A is an isometric view of a nozzle ring member for a nozzle ring assembly according to a second embodiment of the present invention;

FIG. 9B is another isometric view of the nozzle ring member of the second embodiment;

FIG. 10 is a cross-sectional view similar to FIG. 7, but at an intermediate stage of an assembly operation for the second embodiment of the invention;

FIG. 11 is a sectional view similar to FIG. 8, but at an intermediate stage of an assembly operation for the second embodiment;

FIG. 10A is similar to FIG. 10 but shows the nozzle ring assembly of the second embodiment after the assembly operation is completed; and

FIG. 11A is similar to FIG. 11 but shows the nozzle ring assembly of the second embodiment after the assembly operation is completed.

Detailed Description

The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. In this context, references to "radial", "circumferential" and "axial" (or equivalently to cylindrical coordinates r, θ, z, respectively) are relative to the turbocharger axis of rotation, with the axial direction along or parallel to the axis of rotation, the radial direction extending perpendicularly from the axis of rotation, and the circumferential direction about the axis of rotation.

A turbocharger 10 suitable for employing a nozzle ring assembly made in accordance with the present invention is shown in fig. 1. The turbocharger includes a compressor wheel or impeller 14 disposed in a compressor housing 16 and mounted on one end of a rotatable shaft 18. The shaft is supported in bearings 19, the bearings 19 being mounted in a center housing 20 of the turbocharger. The shaft 18 is rotated by a turbine wheel 22 mounted on the other end of the shaft 18 spaced from the compressor wheel to rotatably drive the compressor wheel, which compresses air drawn in through the compressor inlet and delivers the compressed air to a volute 21, which volute 21 collects the compressed air for supply to the intake of an internal combustion engine (not shown) to increase the performance of the engine.

The turbocharger also includes a turbine housing 24 that houses the turbine wheel 22. As previously mentioned, in reciprocating internal combustion engines having a plurality of cylinders, it is advantageous to design the exhaust system in such a way that pressure pulsations occurring in the exhaust gas flow discharged from the cylinders are utilized. In particular, it is advantageous to employ so-called "pulse separation" in which the cylinders of the engine are divided into groups and the pulses from each group of cylinders are substantially isolated from the pulses of the other groups by having a separate exhaust passage for each group. To take full advantage of the pulse separation, it is desirable to minimize communication or "cross talk" between the separate cylinder banks. In the case of a turbocharged engine, it is advantageous to maintain a separate exhaust passage all the way into the turbine of the turbocharger. To this end, the turbine housing typically has separate scroll members that include two separate scroll members that each receive a separate exhaust flow.

Thus, as shown in FIG. 1, the turbine housing 24 defines a meridian-dividing scroll comprising a first scroll 26a and a second scroll 26b separated from one another by a dividing wall 27. The second scroll member is secured to the first scroll member in an axial direction of the turbocharger, and each scroll member receives exhaust gas via a separate exhaust gas inlet defined through the turbine housing. According to the invention, the two exhaust gas flows are separated from one another via a nozzle ring assembly 30 up to the turbine wheel 22, which nozzle ring assembly 30 directs the two exhaust gas flows onto the turbine wheel, respectively. The nozzle ring assembly is disposed adjacent the center housing 20 within the turbine housing 24.

Referring to fig. 2, the nozzle ring assembly 30 defines a first vane ring 40, the first vane ring 40 including first vanes 42 circumferentially spaced around the circumference of the nozzle ring, and a second vane ring 50, the second vane ring 50 including second vanes 52 circumferentially spaced around the circumference of the nozzle ring. The first ring 40 defines first vane passages 44 between circumferentially successive first vanes 42. Similarly, the second ring 50 defines second vane channels 54 between circumferentially successive second vanes 52. The first vane passage 44 is circumferentially offset relative to the second vane passage 54. In other words, the array of second vanes 52 circumferentially "clockwise" about the nozzle ring axis relative to the array of first vanes 42 by an angular amount that is less than the angular spacing between adjacent first vanes. In the illustrated embodiment, the second vane channel is circumferentially offset from the first vane channel by about half the circumferential spacing between the leading edge of one first vane 42 and the leading edge of the next first vane 42 in the circumferential direction. Fluid isolation of the two sets of

vane passages

44 and 54 is achieved by a partition 49 comprising a generally annular wall, with the end of the first vane 42 being joined to one face of the partition 49 and the end of the second vane 52 being joined to the opposite face of the partition.

The nozzle ring assembly 30 includes a first end wall 46 and a second end wall 56. The first end wall 46 is axially spaced from a bulkhead 49, and the end of the first vane 42 opposite the bulkhead is joined to the first end wall. The second end wall 56 is axially spaced on the other side of the bulkhead and the end of the second vane 52 opposite the bulkhead is joined to the second end wall. To prevent rotation of the nozzle ring assembly relative to the turbine housing 24, the nozzle ring may be provided with an anti-rotation feature or a plurality of such features. In one non-limiting embodiment, the anti-rotation feature may include one or more pins 32 (FIG. 1). The nozzle ring assembly may define receptacles in the second end wall 56 (or alternatively, or additionally, in the first end wall 46) that align with corresponding receptacles in the turbine housing 24, and each pair of aligned receptacles may be held in alignment by one of the anti-rotation pins 32. In an exemplary embodiment, there are three such anti-rotation pins, which are circumferentially spaced around the circumference of the nozzle ring. Other types of anti-rotation features are also possible in the practice of the present invention, examples of which include, but are not limited to, radially oriented pins that engage in holes or slots in the turbine casing, integral features such as tabs formed on the nozzle ring assembly for engaging corresponding slots or recesses in the turbine casing, and the like.

The radially innermost end of the divider wall 27 of the turbine housing 24 is adjacent the radially outer periphery of the diaphragm 49 of the nozzle ring assembly 30, as best shown in FIG. 1. The interface between the divider wall and the nozzle ring may be sealed with a seal (e.g., an O-ring or any other suitable type of seal). Alternatively, however, it may be desirable in certain circumstances to have a defined gap between the divider wall and the nozzle ring, the size of the gap being selected to regulate the degree of fluid separation between the two exhaust gas streams.

The first vane passages 44 are positioned to receive exhaust gas only from the first scroll member 26a, and the outlet of each first vane passage 44 directs a first exhaust gas jet onto the leading edge of the turbine blade. Similarly, second vane passages 54 are positioned to receive exhaust gas only from second scroll member 26b, and the outlet of each second vane passage 54 directs a second jet of exhaust gas onto the leading edge of the turbine blade.

Due to the circumferential offset between the two sets of

blades

42 and 52, the turbine blade leading edges receive the first and second exhaust jets from the first and

second blade passages

44 and 54, respectively, in an alternating manner around the circumference of the turbine wheel. That is, one circumferential sector of the impeller receives a first exhaust jet from a first vane passage, an adjacent circumferential sector receives a second exhaust jet from a second vane passage, the next circumferential sector receives a first exhaust jet from the next adjacent first vane passage, and so on in an alternating or staggered manner around the entire circumference of the impeller.

As previously described, the nozzle ring assembly according to embodiments of the present invention can alleviate some of the disadvantages of both meridional and scalloped turbine casing designs according to the prior art. With respect to a sectored turbine housing, out of phase pulses directed at the turbine wheel from two 180 degree sectors can cause undesirable turbocharger shaft motion. In contrast, the nozzle ring assembly of the present invention distributes out-of-phase pulses evenly around the circumference of the turbine wheel, tending to reduce or eliminate such excessive shaft motion. With respect to a meridian-divided turbine casing, since each scroll supplies exhaust gas only to about half the width of the turbine blade leading edge, a significant amount of mixing loss occurs, thereby adversely affecting turbine efficiency. Nozzle ring assemblies according to embodiments of the present invention may alleviate both shaft motion problems and mixing loss problems because the two scroll members alternately (i.e., in an interleaved manner) supply exhaust gas around the entire circumference (and may also blow exhaust gas over the entire extent of the turbine blade leading edges in some embodiments).

The nozzle ring assembly provides the ability to control the flow distribution between the two scroll members. For example, by sizing the vane passages of one scroll member smaller than the vane passages of the other scroll member, an uneven or asymmetric flow distribution can be achieved. In such a case, it may be advantageous for the scroll members to have equal volumes.

The shapes of the inlet and outlet sides of the

vane passages

44 and 54 may be selected by a designer. In some embodiments, the vane passage outlet may be generally rectangular; in other embodiments, they may be elliptical. The inlet of a given vane passage need not necessarily have a shape similar to the outlet of the passage. For example, the vane passage inlet may be rectangular and the outlet may be circular or elliptical, or vice versa. In the above-mentioned case, the vane passage of one of the scroll members is smaller than that of the other scroll member, and the shape of the outlet of the vane passage may be different between the two scroll members. As a non-limiting example, the vane passage outlet for one scroll member may be rectangular, and the vane passage outlet for the other scroll member may be oval and have a smaller flow area than the rectangular outlet.

In the illustrated embodiment, the second vane passages 54 are circumferentially staggered relative to the first vane passages 44 such that there is no circumferential overlap between a given second exhaust jet and an adjacent first exhaust jet. However, the invention is not limited in this sense and in other (not shown) embodiments, the vanes may be configured such that there is some circumferential overlap between the respective first and second exhaust jets. Additionally, in other (not shown) embodiments, each of the first and second blade rings may blow exhaust over less than the entire width or extent of the turbine blade leading edge, and in that case may overlap in the axial direction (and optionally also in the circumferential direction) between the first and second exhaust jets.

In particular, the present invention relates to a method for manufacturing a nozzle ring assembly 30 such as that shown in fig. 2. According to the invention, the nozzle ring assembly comprises three main components, as shown in fig. 3: a nozzle ring 60 defining vanes, first and

second side walls

46, 56. These three components are fabricated as separate parts and then assembled to form nozzle ring assembly 30, as described below. The nozzle ring 60 may be manufactured by an injection molding process, one non-limiting example of which is a Metal Injection Molding (MIM) process.

Referring to fig. 4A and 4B, the nozzle ring 60 includes the first vane ring 40 as previously described, which includes first vanes 42 circumferentially spaced around the circumference of the nozzle ring, and includes the second vane ring 50, which includes second vanes 52 circumferentially spaced around the circumference of the nozzle ring. The first vane ring and the second vane ring are axially spaced apart and integrally joined to each other (and to the intermediate diaphragm 49). As previously described, first vane 42 is circumferentially offset from second vane 52, first vane channel inlet 44 is axially spaced from second vane channel inlet 54, as shown in fig. 1 and 2, but as shown in fig. 1, the first vane channel outlet is radially aligned with the second vane channel outlet (i.e., the first vane channel outlet and the second vane channel outlet are not axially spaced but occupy substantially the same axial extent), and they are circumferentially staggered with respect to one another.

Referring to fig. 5A and 5B, the first sidewall 46 is an annular (or ring-like) portion whose axially outer surface is generally planar. The Outer Diameter (OD) of the first sidewall is substantially equal to the largest diameter of the first vanes 42 at their leading edges (see fig. 2), and the Inner Diameter (ID) of the first sidewall is substantially equal to the smallest diameter of the first vanes at their trailing edges. The axial thickness of the first sidewall is relatively small at the OD and increases in a radially inward direction with a substantially maximum thickness at the ID. Thus, the inner surface of the first side wall does not extend radially, but is inclined with respect to the radial direction. The inner surface defines a plurality of recessed blade receptacles 47 therein, each configured to receive a distal end of a respective one of the first blades 42. The recessed vane pocket 47 mitigates or eliminates exhaust gas leakage between the distal end of the first vane and the inner surface of the first endwall 46.

Second sidewall 56 is substantially a mirror image of the first sidewall, with an inner surface defining a plurality of recessed blade receptacles 57 for receiving the distal ends of second blades 52, but with recessed blade receptacles 57 circumferentially offset or "clockwise" relative to blade receptacles 47, which corresponds to the manner in which second blades 52 rotate clockwise relative to first blades 42 as previously described. The recessed vane pocket 57 mitigates or eliminates exhaust gas leakage between the distal end of the second vane and the inner surface of the second endwall 56.

A method of assembling the nozzle ring 60 with the

side walls

46 and 56 will now be described with primary reference to fig. 3, 4A, 4B, 5A, 5B, 6, 7 and 8. The nozzle ring 60 defines first pin receptacles 61 in a distal end of each of the plurality of circumferentially spaced first vanes 42, the illustrated embodiment showing three such first pin receptacles 61 (fig. 4A and 4B). Corresponding pin receptacles 48 are defined in the first sidewall 46 (fig. 5A and 5B), each pin receptacle 48 in the first sidewall being aligned with a corresponding pin receptacle 61 in the nozzle ring 60. Similarly, the nozzle ring defines second pin receptacles 62 in the distal end of each of the plurality of circumferentially spaced second vanes 52, three such second pin receptacles 62 in the illustrated embodiment (fig. 4A and 4B). A corresponding pin receptacle 58 is defined in the second side wall 56 (fig. 5A and 5B).

Referring to fig. 3, 7 and 8, the first sidewall 46 is secured to one side of the nozzle ring 60 by a first pin P1, the first pin P1 being press fit into the pin receptacle 48 in the first sidewall and the first pin receptacle 61 in the nozzle ring, as seen in fig. 8. Similarly, the second side wall 56 is secured to the other side of the nozzle ring by second pins P2, and the second pins P2 are press fit into the pin receptacles 58 in the second side wall and into the second pin receptacles 62 in the nozzle ring, as best seen in fig. 7, thereby completing the assembly of the nozzle ring assembly 30 as shown in fig. 2.

A second embodiment of the present invention is shown in fig. 9A, 9B, 10A, 11 and 11A. As shown in fig. 9A and 9B, the second embodiment is generally similar to the first embodiment except that the first and second pins P1 and P2 are an integral structure of the nozzle ring 60. The first pin P1 is inserted into the pin receptacle 48 in the first side wall 46 (fig. 11) and then secured therein, such as by riveting (fig. 11A). Similarly, a second pin P2 is inserted into the pin receptacle 58 in the second sidewall 56 (fig. 10) and then secured therein, such as by riveting (fig. 10A).

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for manufacturing a two-bladed nozzle ring assembly for a turbine nozzle of a turbocharger, the method comprising the steps of:

(a) providing a first sidewall as an annular portion;

(b) providing a second sidewall as an annular portion, the second sidewall being formed separately from the first sidewall;

(c) providing a nozzle ring spaced from the first and second sidewalls, wherein the nozzle ring is configured with a first vane ring comprising first vanes circumferentially spaced apart around a circumference of the nozzle ring and is configured with a second vane ring comprising second vanes circumferentially spaced apart around the circumference of the nozzle ring, the first and second vane rings being axially spaced apart and integrally joined to one another, the first vane ring defining first vane passages between circumferentially successive first vanes and the second vane ring defining second vane passages between circumferentially successive second vanes, wherein the first vane passages have respective first vane passage inlets and first vane passage outlets, wherein the second vane passages have respective second vane passage inlets and second vane passage outlets, wherein the first vane is circumferentially offset from the second vane, the first vane channel inlet is axially spaced from the second vane channel inlet, and the first vane channel outlet is radially aligned with and circumferentially staggered from the second vane channel outlet; and

(d) joining the first sidewall to a distal face of the first vane ring and joining the second sidewall to a distal face of the second vane ring.

2. The method of claim 1, wherein step (a) comprises providing the first sidewall to include a plurality of recessed blade receptacles in a face of the first sidewall facing the distal end face of the first blade ring, each of the recessed blade receptacles receiving a distal end of a respective first blade.

3. The method of claim 1, wherein step (b) comprises providing the second sidewall to include a plurality of recessed blade receptacles in a face of the second sidewall facing the distal end face of the second blade ring, each recessed blade receptacle receiving a distal end of a respective second blade.

4. The method of claim 1, wherein step (c) comprises manufacturing the nozzle ring by an injection molding process.

5. The method of claim 4, wherein the injection molding process comprises a Metal Injection Molding (MIM) process.

6. The method of claim 1, wherein the first sidewall and the first vane ring are each configured to define a plurality of circumferentially spaced pin receptacles, the pin receptacles of the first sidewall being aligned with the pin receptacles of the first vane ring, and wherein step (d) comprises press-fitting pins into the pin receptacles of the first vane ring and into the pin receptacles of the first sidewall.

7. The method of claim 1, wherein the second sidewall and the second vane ring are each configured to define a plurality of circumferentially spaced pin receptacles, the pin receptacles of the second sidewall being aligned with the pin receptacles of the second vane ring, and wherein step (d) comprises press fitting pins into the pin receptacles of the second vane ring and into the pin receptacles of the second sidewall.

8. The method of claim 1, wherein the first blade ring is configured to include a plurality of circumferentially spaced pins projecting from the distal end face of the first blade ring and the first sidewall is configured to include a plurality of circumferentially spaced pin receptacles, and wherein step (d) includes inserting the pins of the first blade ring into the pin receptacles of the first sidewall and securing the pins therein.

9. The method of claim 8, wherein the step of securing the pin in the pin receptacle comprises riveting the pin.

10. The method of claim 1, wherein the second vane ring is configured to include a plurality of circumferentially spaced pins projecting from the distal end face of the second vane ring and the second sidewall is configured to include a plurality of circumferentially spaced pin receptacles, and wherein step (d) includes inserting the pins of the second vane ring into the pin receptacles of the second sidewall and securing the pins therein.

11. The method of claim 10, wherein the step of securing the pin in the pin receptacle comprises riveting the pin.