GB2235734A

GB2235734A - Bladed rotor construction

Info

Publication number: GB2235734A
Application number: GB9016445A
Authority: GB
Inventors: Wolfgang Weiler
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines GmbH
Priority date: 1989-07-27
Filing date: 1990-07-26
Publication date: 1991-03-13
Anticipated expiration: 2010-07-26
Also published as: IT1242978B; FR2650338A1; GB2235734B; IT9020963A0; DE3924829C2; FR2650338B1; IT9020963A1; GB9016445D0; DE3924829A1

Abstract

A compressor or turbine rotor, particularly for gas turbine propulsion units in which individual blades 1. 2 of a compressor or turbine stage are disposed in slotted-wing fashion in respect of adjacent outlet and inlet edges 3, 4. The rotor comprises a plurality of portions A, B, each of which comprises a row of profile members or blades 1, 2 the portions A, B having on adjacent end faces 3, 4 thereof interengaging complementary profiles 7, 8 thereon to prevent relative rotation. Coaxial centering action when the portions A, B are pushed together may be provided by a peripheral stepped portion (9), Fig 1. The rotor portions A, B may be fastened together by welding or by bolts (16), Fig 1. <IMAGE>

Description

1 T.URBO-ROTOR CONSTRUCTION This invention relates to a rotor,

particularly for compressors or turbines of gas turbine propulsion units.

Axial compressors, are known in which blades of guide vanes and bladed wheels are constructed as so-called "tandem nozzles", i.e. instead of in each case single-row cascades with solid profiles, mounting twin-row cascades with single profiles on one and the same wheel, slotted winglike throughflow cross-sections always being left between two axially successive single profiles (c.f. "Besonderheiten der axialen Str6mungsmaschinen" /Special Features of Axial Flow Machines) on p.406 of the journal "Strbmungsmaschinen" published by Carl Pfleiderer; Hartwig Petermann, 5th edition, 1986). Within the framework of sach cascade concepts it is intended inter alia that, for example in the case of compressors, the necessary stage work should be completed with the least possible loss and should effectively require a comparatively minimal overall length. For instance, in the case of compressor guide vanes or nozzles compared with solid profile concepts, it is intended that the running length of the boundary layer of air around the profile should be limited; furthermore, by inter alia an appropriate correlation of the outlet and inlet edges of the nozzle profiles to one another, the risk of boundary layer detachment on the convex side of the blade (solid profile) is thought to be increased by the so-called "slotted wing effect".

2 From already proposed wing concepts (aircraft) and also from pure guide vane concepts, e.g. in the case of diffusers for radial compressors, it emerges that the relevant leading and main (wing) profile portions ought to overlap in a slotted wing-like fashion on the leading and trailing edges, the overlap possibly being variable, so that, for instance in the case of a compressor, the breadth of the performance characteristics can be widened over the range of operating conditions. The advantages of the actual at least partially localised profile overlap resides inter alia in the fact of rendering useful the slotted wing effect in the sense of an even lower-loss flow deflection or an even higher level of aerodynamic efficiency.

In the past, it has always been extremely difficult to produce a socalled tandem nozzle with an associated disc integrally, e.g. by machining the blades from the solid material. Just on account of the considerable space needed for the necessary production tools (shank end mills, spherical cutters). it has hitherto been impossible for practical reasons to produce tandem rotors of integral design, particularly in respect of comparatively small or c6mpact dimensions of the relevant turbine components. Production would be even more complicated and expensive if it were desired to utilise the already suggested idea of the "slotted wing effect" with actual localised profile edge overlapping, for example in the case of a so-called ',tandem nozzle".

One object of the present invention is to enable the manufacture 3 of a turbine rotor of the type mentioned which, while having relatively small dimensions, can be aerodynamically highly effective and comparatively easily produced, with optimum exploitation of the slotted wing effect.

According to this invention we propose a turbo rotor, particularly for gas turbine propulsion units, in which the rotor blades of one stage comprise prof ile members or blades which partially overlap in the direction of flow and which are disposed in a ring on the wheel rims of interconnected rotor bodies, the wheel rims having end faces adapted by the provision of profiled surfaces, to interengage in form-locking manner to constitute a safeguard against peripheral rotation. One advantage of this invention is that the multiple profile nozzle an be produced from individual rotor or disc elements in the "exploded state--; with this arrangement, a rotor element containing the relevant blade profiles is produced complete in itself; the individual blade profiles can, for example, be machined fairly conveniently from solid and given a fine surface treatment (for example, by grinding) to satisfy particular requirements; thereforef access from all sides for tools and machining is possible; this is particularly advantageous in the light of the relatively narrow gap which is left between adjacent blade profile end edges (slotted wing effect). Within the framework of an appropriate peripheral distribution and construction and depth of engagement of the tongue-and -groove joint, therefore inter alia in relation to the reciprocal profile end edge offset which is required for the slotted wing effect, the necessary overall profile geometry 4 resides in simple assembly or fitting together of the individual rotor of wheel elements. In this respect, the individual elements can be connected inseparably (by welding) or separably (by means of bolts and flanges); the latter method having the particular advantage of enabling the exchange damaged or faulty rotor blade units.

other advantageous features of the present invention are set forth in the appendant claims.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional view of a portion of an axial compressor of a gas turbine propulsion unit showing a tandamlike profile nozzle integrated into the compressor rotor and composed of two individual wheel discs with a partially slotted wing type of overlap of adjacent profile outlet and inlet edges, and Figure 2 is a plan view of the tandem 'nozzle taken on arrow Z in Figure 1.

Figures 1 and 2 illustrate a so-called ',tandem nozzle arrangement" which is integrated into the drum-like rotor of the axial compressor as shown.

The rotor has a plurality of rotor members, in this case two rotor members A,.B,, each of which comprises one row of profile members/blades 1,2, with wheel rims 5, 6, adjacent end faces 3,4, (Fig. 2) of which are shaped so as to interengage in a f orm locking manner to prevent relative rotation. Af ter f inal assembly of the rotor, the adjacent outlet and inlet edges of the blades 1,2, of a geometrically rigid nozzle (consisting of rotor blades - viewed at blade height) should overlap at least partially on the slotted wing principle as illustrated at position S in f igure 1. Therefore, the relevant outlet or inlet edges are shown overlapping in relation to an imaginary vertical transverse plane extendipg obliquely inwardly and intersecting the end edges 3.4. In terms of peripheral distribution, i.e. particularly in terms of peripheral division (teeth, projections, keys or the like) and depths of engagement, the end-face surface profiling on the wheel rims 5,6, should be adopted to the operationally required rigid nozzle geometry of the profile members 1,2, of the blade assembly along with the slotted wing overlap arrangement S.

The rotors A,B, blades 1,2, may be constituent parts of a combined axially or diagonally traversed rotor blade assembly of a blade wheel.

In the illustrated embodiment the rotors A,B, comprise wheel rims 5,6, which have end faces which are complementary in shape 3,4, having in this case, for example, a nose-like type of profile, However, a serrated or castellated profiling or a mixed combination of complementary profiles may be provided. As can be seen especially in figure 2, the outlet and inlet edges of the 6 two rows of adjacent blades 1, 2, are disposed on the axially projecting parts 7.8. of the associated wheel rims 5,6.

Figure 2 shows also that the relevant projections 7,8, on the two adjacent wheel rims 5,6, are of different widths but within the framework of the form-locking interengaging connection,, they are nevertheless uniformly distributed over the periphery.

Furthermore, it can be seen particularly clearly in figure 2 that on one wheel rim 5, there is only one blade 1 with its outlet edge disposed on the comparatively narrow projection 7. By contrast, the other wheel rim 6 may have more than one blade 2, V, the inlet edges of which extend onto the relatively broad projections 8. Therefore, the number of profile members 2,21. of the wheel rim 6 may be a whole multiple of the number on t:he wheel rim 5, so that, for example, as shown only every second blade 2 of the wheel rim 6 communicates with a blade 1 of the wheel rim 5 on the slotted wing principle (S).

As figure 1 clearly shows, the end face of the wheel rim 5 may be stepped to define a cylindrical surface onto which the wheel rim 6 f itted, being centred thereby - by a portion which is adapted to it in terms of installation height and depth.

The rotors A,B, containing the wheel rims 5,6, are constituent parts of wheel diBCS 10,11, the step 9 on the wheel rim 5 being integral with a connecting flange 12 extending radially inwardly toward the rotor axis to which the wheel disc 11 is secured.

-1 7 Furthermore, in accordance with figure 1, the wheel disc 11 with. the relevant other wheel rim 6, and in fact on the side remote from the surface profile connection, the rim 6 of the wheel disc 11 may likewise fit over a stepped portion 13 of a drum wall part 14 of the rotor assembly. The stepped portion 13 has integral therewith another connecting f lange 15 which extends inwardly toward the rotor axis; wheel discs 10, 11, are detachably connected to each other by means of bolts 15 which pass through the flanges 12 and 15.

The two rotor bodies can be welded together in the region of the outer wheel rim segments. Furthermore, it is possible for the flange sides of the wheel discs 10 and 11 to be welded together. Also, there may be a welded connection at 17 to f urther extexiial drum structures of the axial compressor rotor".

Other advantageous developments of the techniques underlying the invention are: firstly, at least two blade wheel members 10, 11, are produced separately and have on their wheel rim surfaces blades 1,2, which are disposed in the required peripheral distribution; mutual surface machining of one rear and one matching front surf ace 3 or 4 of the wheel rims to produce complementary interengaging shapes or profiles to prevent relative rotation, i.e. to safeguard against peripheral rotation, the illustrated tongue and groove connection guaranteeing a concentric seating of the surfaces of the two blade wheels or wheel discs 10.11; the surface finishing which is carried out 8 is such that by subsequent axial fitment together of the wheel rims 5,6, with wheel discs 10,11, two adjacent rows of blades 1,2, will overlap at least partially on the slotted ring principle (S-f igure 1) at their respective outlet and inlet edges; afterwards, as already described with reference to figures 1 and 2, the wheel discs 10, 11, can either be connected to each other in a mechanically separable fashion ort alternatively, be permanently connected by e.g. welding.

Figures 1 and 2 also show that appropriately profiled complementary end faces 3,4, in this case, having what can also be described as a "tongueand-groove" kind of connection for example with nose-like projecting portions, in the fully assembled state are at a relatively minimal particularly axial distance from each other. This is also an advantageous feaLare of the invention in that the differential heat expansion on the wheel rim side or minor stresses which form, for instance due to centrifugal forces, can be compensated without adversely affecting the rigid and blade-end seating of the wheel discs of the wheel rims. By reason of the fact-that the mutual engagement of the profiled constructed end faces 3,4, of the wheel rims 5,6, is on a peripheral stepped portion 9, it is possible at the same time to provide a coaxial centering fitment when the wheel rims 5,6, are pushed together. Such an advantageous combination of protection against peripheral rotation and centering at the relevant connection is provided.

The outer housing 171 of the axial compressor has guide vanes 18 9 and 19 mounted on it and the blades 1 or 2 or 21 are shroudless at the tips, the relevant free outer blade ends being disposed at a distance from one another, leaving minimal radial gaps in respect of a blade inlet lining 20 in the compressor housing 171.

Claims

CLAIMS:

1. A rotor, in which the rotor blades of one stage at least partially overlap in the direction of flow and are disposed on the wheel rims of interconnected rotor bodies, the wheel rims having profiled end faces adapted to interengage so as to prevent relative rotation.

2. A rotor according to claim 1, the end face prof iling, in terms of peripheral distribution and graduation as well as depth of engagement, is matched to the operationally required mutual fixed correlation of the blades.

3. A rotor according to claim 2, wherein the adjacent end faces of the wheel rims are complementary in shape, preferably having a serrated, projecting or wedge-shaped profile.

4. A rotor according to any one of claims 1 to 3, wherein the outlet and the inlet edges of two rows of adjacent blades are in each case disposed on axially projecting portions of the associated wheel rims.

5. A rotor according to claim 4. wherein projecting portions on two adjacent wheel rims are of different widths but are in themselves uniformly distributed over the periphery.

6. A rotor according to claim 4 or 5, wherein on one wheel rim having comparatively narrow projecting portions, the outlet edge of only one blade extends onto each of said portions and on the 1 i 11 other wheel rim, the inlet edges of at least two blades extend into the relatively broad projecting portions so that the number of blades of the said other wheel rim is a whole multiple of the number on the said one wheel rim, and that only one of the said at least two blades on the said other wheel rim communicate with a blade on the said one wheel rim on the slotted wing principle.

7. A rotor according to any one of claims 1 to 6, wherein the end face surface profiling is on a stepped portion of one side of one wheel rim onto which the other wheel rim is fitted and is centred.

8. A rotor according to claim 8, wherein the rotor bodies containing the wheel rims are component parts of wheel discs a stepped portion on one wheel ridmerging into a connecting flange extending toward the rotor axis and to which the wheel disc containing the other wheel rim is fixed.

9. A rotor according to claim 7, wherein on the side remote from the end face profiling the wheel disc with the said other wheel rim has a portion which fits onto a stepped portion on a drum wall part, which, stepped portion merges into a connecting flange extending toward the rotor axis, both or at least one first and one further wheel disc being separably connected to each other by fastening means passing through the flanges.

10. A rotor according to claim 7 or 8,, wherein there is provision for wheel rim and/or flange-side welding of the rotor.

12

11. A rotor constructed and arranged substantially as herein before described with reference to and as illustrated in the accompanying drawings.

:X Published 1991 at7be Patent Office. State House. 66/71 HighHolbom. London WCIR47?. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile point, Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.