GB2220034A

GB2220034A - Load transmission in gas turbine engines

Info

Publication number: GB2220034A
Application number: GB8814779A
Authority: GB
Inventors: Trevor Harold Speak
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1988-06-22
Filing date: 1988-06-22
Publication date: 1989-12-28
Anticipated expiration: 2008-06-22
Also published as: FR2633330A1; DE3919606C2; DE3919606A1; FR2633330B1; JPH0240027A; GB8814779D0; US4984423A; GB2220034B

Abstract

Means are provided for reacting the axial loads FA experienced by for example, the combustion chamber inner and outer casings 24, 30 and the inlet guide vanes of 26 of the turbine of a gas turbine engine, through the outlet guide vanes 22 of the compressor and to the supportive engine outer casing 28 without imparting a torsional load on the outlet guide vanes 22. The means comprises a plurality of loading bars 32, formed by cutting slots 34 in the combustion chamber outer casing 30, which are angled relative to the applied axial load FA at the same angle as the chord line C of the outlet guide vanes 22 is angled relative to the engines centre line CL. A significant proportion of the axial load FA is reacted along the load bars 32 and through the vanes 22 without imparting twist into said vanes. The comparatively small torsional reaction load required is reacted through the inlet guide vanes 26 of the turbine 16. A seal 36, prevents gas escape through the slots 34. …<IMAGE>…

Description

2 2- AERODYNAMIC LOADING IN GAS TURBINE ENGINES This invention relates to

aerodynamic loading in gas turbine engines and is particularly relevant to the re-orientation of axial loads experienced by various components in such an engine.

Some components in a gas turbine engine experience several different types of loading during operation such as for example axial, torsional, radial and bending loads. This invention is particularly relevant to the first of these loads, however, consideration is also given to torsional loads.

Gas pressures acting on the combustion chamber inner and outer casing as well as the high pressure turbine nozzle guide vanes produce axial and torsional loads which must be reacted out to the engine's supportive outer casing. It is common practice to react out the comparatively low torsional loads through the inlet guide vanes in the high pressure turbine. The comparatively high axial loads are reacted through the outlet guide vanes of the high pressure compressor via the combustion chamber outer casing.

Each high pressure compressor outlet guide vane is angled relative to the centre line of the engine in order to direct air into the combustion chamber at the most advantageous angle. A significant aerodynamic advantage may be gained by reducing the thickness of each vane so that it presents as small an obstacle as possible to the incoming air-flow.

it has been found that in order to prevent the vanes twisting due to L-he high axial loads transmitted therethrough it is necessary to have vanes thicker than desirable. It is an object of the present invention to provide a means for re-orientating the axial loads experienced by the high pressure compressor outlet guide vanes which avoids twisting and thereby allows thinner and more aerodynamically efficient vanes to be used.

The present invention will now be more particularly described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of a gas turbine engine.

Figure 2 is a cross sectional view of part of the engine shown in figure 1.

Figure 3 is a diagrammatic representation of the present invention.

Referring briefly to figure 1, a gas turbine engine 10 generally comprises an axial flow compressor 12 combustion means 14 turbine means 16 connected to the compressor to drive the compressor, a jet pipe 18 and a rear nozzle 20.

In figure 2, it can be seen that the engine 10 includes a plurality of circumferentially spaced outlet guide vanes 22 situated in the high pressure portion of the compressor I", an inner combustion chamber 24 which forms part of the combustion means 14, and a plurality of circumferentially spaced inlet guide vanes 26 situated in the high pressure portion of the turbine 16. The outlet guide vanes 22 are fixedly attached at their radially outer end 22a to a portion of the engine casing 28 and at their radially inner end 22b to the combustion chamber outer casing 30. The combustion chamber outer casing 30 acts to contain the combustion gasses and is located at its downstream end to the inlet guide vanes 26 of the high pressure portion of the turbine 16. It will be appreciated that the downstream portions of the inner combustion chamber 24 and combustion chamber outer casing 30 together with the inlet guide vanes 26 experience an axial load F due to the gas pressures acting thereon. The gas pressures can be considerable and are commonly reacted through the combustion chamber outer casing 30 and the outlet guide vanes 22 to the engine casing 28 which acts as a support structure.

It is well known that in order to prevent the above mentioned vanes 22 twisting it is necessary to make them thicker than aerodynamically desirable. It has been found that if the axial load F can be reorientated such that it is transmitted along the chord line C of the vanes 22 the required load can be reacted by thinner vanes than previously used.

4 The axial load F is re-orientated by the use of one or more bars 32 positioned circumferentially around the combustion chamber outer casing 30. Each load bar is angled relative to the applied load and the engines centre 141ne C L by an amount-which is equal to the angle o at which the chord line of each vane 22 is angled relative to the centre line C L The load bars 32 are formed by cutting a series of circumferentially spaced slots 34 around the circumference of the combustion chamber outer casing 30. Each slot is angled relative to the engines centre line C T1 in the same manner as each loading bar 32 and thereby defines the outer edges 32a of each loading bar 32. In order to prevent combustion gasses escaping through the slots 34 a circumferentially extending seal 36 is positioned over the slots as shown in figure 2. The seal 36 may be located relative to the outer casing 30 with the aid of circumferentially extending lips 36a, 36b provided on the outer casing 30 which locate in features 38,40 provided on the casing 30. It will however be appreciated that alternative methods of mounting may be utilised.

In operation, the combustion chamber inner and outer casings 24, 30 and the inlet guide vanes 26 to the turbine 16 experience high axial loads and possibly a small degree of torsional loading due to the pressure of the combustion gasses, as represented diagrammatically by arrows FA and F T on the vane 26 in figure 3. Any small torsional load F T which the combustion chamber casings experience is reacted through the vanes 26 to the outer casing 28.

Bolts or anv other similar device may be used to secure the ends of the combustion chamber outer casing 30 to the vanes 26 and hence help transinit the torsional load FT The direction of the reaction force which reacts the effect of the axial loading F A is determined by the angular position of the loading bars 32 relative to the centre line C L The load bars 32 provide a loading path along which a portion of the reaction load Rt)is transmitted. It can be seen from figure 3 that if the chord line C of the compressor outlet guide vanes 22 is angled relative to the centre line C L to the same degree as the loading bars 32 are angled relative to the centre line then that portion of the axial load F A which is reacted along the loading bars 32 is transmitted to the supportive engine outer casing 28 along the chord line C of the vanes 22. It will be appreciated that twisting of the vanes 22 can be avoided by incorporating this method of load reaction as the vane experiences no torsional force. It will also be seen from figure 3 that in order to balance the reaction force which counteracts the effect of the axial load F A a small torsional reaction load RT is required. The torsional reaction load RT is acceptably small and may be transmitted through the inlet guide vanes 26 in the same manner as the torsional load FT' It will be appreciated that the effect of reducing the angles-e and 0 is to allow a greater portion of the axial load to be reacted through the loading bars and the outlet guide vanes 22 and to reduce the magnitude of the reaction load RT

Claims

We Claim:

4 1. A means for re-orientating and reacting an. applied load experienced by a first component, the means comprising at least one load bar angled relative to the applied load which is connected at a first end the first component and at a second end to a second component which reacts said applied load.
2. A means as claimed in claim 1 in which the loading bar and the first and second components are situated in a gas turbine engine and the applied load is the axial load produced by the gas pressure in said engine.
3. A means as claimed in claim 1 or claim 2 in which the second component is an outlet guide vane of the high pressure compressor of a gas turbine engine.
4. A means as claimed in claim 3 in which the chord line of the outlet guide vane is angled relative to the applied load at an angle which is equal to the angle at which the load bar is angled relative to said applied load.
5. A means as claimed in any one of the preceding claims in which there is provided a means for reacting torsional movement of the first component relative to the second component.
6. A means as claimed in claim 5. in which the means for reacting the torsional movement comprises an inlet guide vane in the high pressure turbine of said engine.
7. A means as claimed in any one of the preceding claims in which the first component includes the combustion chamber outer casing of said engine.
8. A means as claimed in claim 7 in which the first component further includes any structure carried by the combustion chamber outer casing which is subjected to an axial load.
9. A means as claimed in any one of claims 3 to 8 in which a plurality of circumferentially spaced outlet guide vanes are provided around the circumference of the high pressure compressor outlet.
10. A means as claimed in claim 9 which each outlet guide vane is provided with at least one load bar connected there to.
11. A means substantially as herein described with reference to figures 1 to 3 of the accompanying drawings.

Published 1989 at The Patent Office, State House. 6671 High Holborn, London WCIF 4TP. Partner c:)ples May be obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent, Con. 1/87

11. A means as claimed in claim 10 in which each load bar forms part of the combustion chamber outer casing.

12. A means as claimed in claim 11 in which each load bar is circumferentially spaced from its neighbour by a predetermined amount.

8 13. A means as claimed in claim 11 or claim 12 in which a seal is provided to prevent the passage of gasses through the spaces formed between the load bars.

14. A means substantially as herein described with reference to figures 1 to 3 of the accompanying drawings.

1 Amendments to the claims have been filed as follows 1. A means for re-orientating and reacting an applied axial gas pressure load experienced by a first component in a gas turbine engine having a compressor with outlet guide vanes situated therein, the means comprising at least one load bar which is angled relative to the applied load and which is connected at a first end to the first component and at a second end to an outlet guide vane of the compressor, said guide vane having a chord line which is angled relative to the applied load at an angle equal to the angle at which the load bar is angled relative to said applied load.

2. A means as claimed in claim 1 in which there is provided a means for reacting torsional movement of the first component relative to the outlet guide vane.

3. A means as claimed in claim 2 in which the means for reacting the torsional movement comprises an inlet guide vane in the high pressure turbine of said engine.

4. A means as claimed in any one of the preceding claims in which the first component includes the combustion chamber outer casing of said engine.

5. A means as claimed in claim 4 in which the first component further includes any structure carried by the combustion chamber outer casing which is subjected to an axial load.

- ID - 6. A means as claimed in any one of claims 3 to 5 in which a plurality of circumferentially spaced outlet guide vanes are provided around the circumference of the high pressure compressor outlet.

7. A means as claimed in claim 6 which each outlet guide vane is provided with at least one load bar connected there to.

8. A means as claimed in claim 7 in which each load bar forms part of the combustion chamber outer casing.

9. A means as claimed in claim 8 in which each load bar is circumferentially spaced from its neighbour by a predetermined amount.

10. A means as claimed in claim 7 or claim 8 in which a seal is provided to prevent the passage of gasses through the spaces formed between the load bars.