GB2115881A

GB2115881A - Gas turbine engine stator vane assembly

Info

Publication number: GB2115881A
Application number: GB08205794A
Authority: GB
Inventors: Archibald Bathgate Mckenzie
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1982-02-26
Filing date: 1982-02-26
Publication date: 1983-09-14
Also published as: FR2522363A1; DE3306298A1

Abstract

An array of alternate primary 20 and secondary vanes 21 is provided wherein each primary vane 20 has a portion extending from its leading edge 24 to a mid-chord position 25 which is so configured as to provide no lift to any gases flowing over it. The remaining portion of each primary vane 20 is configured so as to provide lift. The arrangement provides low aspect ratio primary vanes 20 which have low eddy losses due to main gas flow and boundary layer flow interaction. Additional lift is provided by the secondary vanes 21 which are each less than half the chordal extent of the primary vanes 20 and are interposed between the lifting portions of the primary vanes 20. <IMAGE>

Description

SPECIFICATION Gas turbine engine stator vane assembly This invention relates to a gas turbine engine stator vane assembly.

Stator vane assemblies for gas turbine engines and in particular nozzle guide vane assemblies suffer, to a greater or lesser degree, from what are generally known as secondary losses. These generally arise from the interaction between the boundary layer of gases flowing adjacent the working surfaces of the vane assembly and the main flow of gases through the assembly. Thus velocity and flow direction differences between the boundary layer and the remainder of the gas flow result in eddies being formed on the working surfaces of the assembly and these in turn can seriously affect the efficiency of the vane assembly.

Secondary losses are known to increase in severity with a decrease in the aspect ratio (span to chord ratio) of the vanes of a particular vane assembly. However it is frequently desirable for installation purposes to have vanes which have low aspect ratios. It is an object of the present invention to provide a stator vane assembly having vanes of low aspect ratio but which have reduced secondary losses.

According to the present invention, a stator vane assembly suitable for a gas turbine engine comprises an annular array of low aspect ratio primary vanes, each of which is of generally aerofoil shape cross-section, a portion of the chordal extent of each of said vanes being so configured as to provide substantially no lift to any gas flowing over it, the remaining portion of each of said primary vanes being so configured as to provide lift to any gas flowing over it, those vane portions which provide lift having high aspect ratio secondary vanes interposed between them, each of said secondary vanes being of aerofoil shape crosssection to provide lifting surfaces along the whole of their chordal extent which supplement the lifting surfaces of said primary vanes and have a chordal extent which is less than that of each of said primary vanes.

The portion of each of primary vanes which is so configured as to provide substantially no lift to any gas flowing over it preferably extends from its leading edge to approximately mid-way along the chord thereof, the remaining portion of each of said primary vanes extending to the trailing edge thereof being so configured as to provide lift to any gas flowing over it.

The trailing edges of said primary and secondary vanes are preferably aligned with each other.

Said stator vane assembly may constitute a part of the turbine of a gas turbine engine.

Said stator vane assembly may be a nozzle guide vane assembly.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a sectional side view of a ducted fan gas turbine engine which incorporates a stator vane assembly in accordance with the present invention.

Figure 2 is a side view of a part of a stator vane assembly in accordance with the present invention.

Figure 3 is a view on section line A-A of Fig. 2.

With reference to Fig. 1, a ducted fan gas turbine engine generally indicated at 10 comprises, in axial flow series, a ducted fan 11, an intermediate pressure compressor 12, a high pressure compressor 13, combustion equipment 14, a high pressure turbine 15, an intermediate pressure turbine 16, a low pressure turbine 1 7 and a propulsion nozzle 18.

The gas turbine engine 10 functions in the conventional manner. Thus air is compressed by the fan 11, intermediate compressor 1 2 and high pressure compressor 1 3 is mixed with fuel and the mixture combusted in the combustion equipment 14. The resulting combustion products expand through the high, intermediate and low pressure turbines 15, 1 6 and 1 7 before being exhausted to atmosphere through the nozzle 1 8.

The intermediate pressure turbine 1 6 comprises an annular array of nozzle guide vanes 1 9 which direct exhaust gases from the rotor blades of the high pressure turbine 1 5 on to the rotor blades of the intermediate pressure turbine 16. The nozzle guide vane array 19, which can be seen more clearly in Figs. 2 and 3, comprises a plurality of primary and secondary vanes 20 and 21 respectively. Shrouds 22 and 23 which are located at the radially inner and outer ends of the primary and secondary vanes 20 and 21 serve to define an axial portion of the gas flow through the high, intermediate and low pressure turbines 15, 16 and 17.

Each of the primary vanes 20 is of low aspect ratio and generally aerofoil shape cross-section as can be seen in Fig. 3. However the portion of each vane 20 which extends from its leading edge 24 to a position 25 which is approximately mid-way along its chordal extent is so configured that it does not provide any lift to the exhaust gases which in operation pass over it. The remaining portion of each vane which extends from the mid-way position 25 to its trailing edge 26 is so configured that it does provide lift to the exhaust gases passing over it. Thus since each of the primary vanes 20 only provides lift over the portion which extends from its mid-chord position 25 to its trailing edge 26, it is only in this portion that boundary layer eddies, and hence, secondary losses, occur.The primary vane 20 portion which extends from the lead ing edge 24 to the mid-chord position 25 does not provide any lifting surfaces and hence does not incur any significant secondary losses. However it does extend the chordal extent of each primary vane 20 so that although secondary losses are minimised by being confined to the rear portion of each primary vane 20, the primary vane 20 nevertheless has a low aspect ratio.

Since the primary vanes 20 incur a loss in total lifting effect by virtue of their configuration, additional lifting surfaces are necessary.

These are provided by secondary vanes 21, each of which is interposed between adjacent primary vanes 20. Thus each secondary vane 21 is of high aspect ratio and aerofoil shape cross-section so that it provides lifting surfaces along the whole of its chordal extent. The chordal extend of each of the secondary vanes 21 is less than half that of the primary vanes 20 and the trailing edges 27 of the secondary vanes 21 are aligned with each other and with the trailing edges 26 of the primary vanes 20.

It will be seen therefore that the stator vane assembly of the present invention provides low aspect ratio primary vanes 20 which have lower secondary losses than would normally be expected with conventional vanes having the same aspect ratio.

Although the present invention has been described with reference to a nozzle guide vane assembly which constitutes part of a turbine assembly, it will be appreciated that it is applicable to other stator vane assemblies both in the turbine and eleswhere within a gas turbine engine.

Claims

1. A stator vane assembly suitable for a gas turbine engine comprising an annular array of low aspect ratio primary vanes, each of which is of generally aerofoil shape crosssection, a portion of the chordal extent of each of said vanes being so configured as to provide substantially no lift to any gas flowing over it, the remaining portion of each of said primary vanes being so configured as to provide lift to any gas flowing over it, those vane portions which provide lift having high aspect ratio secondary vanes interposed between them, each of said secondary vanes being of aerofoil shape cross-section to provide lifting surfaces along the whole of their chordal extent which supplement the lifting surfaces of said primary vanes and have a chordal extent which is less than that of each of said primary vanes.

2. A stator vane assembly as claimed in claim 1 wherein the portion of each of said primary vanes which is so configured as to provide substantially no lift to any gas flowing over it extends from its leading edge to approximately mid-way along the chordal thereof, the remaining portion of each of said vanes extending to the trailing edge thereof being so configured as to provide lift to any gas flowing over it.

3 A stator vane assembly as claimed in claim 1 or claim 2 wherein the trailing edges of said primary and secondary vanes are aligned with each other.

4. A stator vane assembly as claimed in any one preceding claim wherein said stator vane assembly constitutes a part of the turbine of a gas turbine engine.

5. A stator vane assembly as claimed in any one preceding claim wherein said stator vane assembly is a nozzle guide vane assembly.

6. A stator vane assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.