GB2147405A

GB2147405A - Gas turbine engine combustion chamber mounting

Info

Publication number: GB2147405A
Application number: GB08325964A
Authority: GB
Inventors: Anthony Pidcock
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1983-09-28
Filing date: 1983-09-28
Publication date: 1985-05-09
Also published as: GB8325964D0

Abstract

A front mounting for a gas turbine engine annular combustion chamber has a plurality of radial locating pins (28) screwed into bosses (26) which are attached to the radially outer wall of the combustion chamber. Each pin (28) co-operates with a housing (30) which is removably attached to a casing (14) enclosing the combustion chamber. The mounting allows radial movement whilst restraining axial movement, and allows the pins to be replaced easily without the need for engine removal or strip. As the housings are in a relatively cool zone, lubricant can be used to reduce or eliminate frettage. <IMAGE>

Description

SPECIFICATION Gas turbine engine combustion chamber mounting This invention relates to a means for mounting a combustion chamber within a casing of a gas turbine engine, and is particularly concerned with a mounting for an annular combustion chamber.

There are two main approaches to the mounting of gas turbine engine combustion chambers. The mounting can either be at the front or rear of the combustor. A rigid mounting at the rear end results in relative axial movement between the combustor head and the fuel injector over the engine operating range which can compromise combustion performance. A front mounting avoids this relative movement and can be achieved by the use of rigid bolting, flexible diaphragms or sliding pins. The sliding pins provide an arrangement in which there are no locked up stresses due to differential thermal growth, but problems can arise due to frettage between the pins and their respective locating bushes.

The present invention seeks to provide a front mounting for a gas turbine engine combustor using locating pins which are easily replaceable and which can be lubricated to reduce or eliminate frettage.

Accordingly, the present invention provides a front mounting for a gas turbine engine annular combustion chamber, the mounting comprising a plurality of radially arranged locating pins removably attached to the combustion chamber adjacent the front end thereof and a plurality of corresponding locating pin housings removably attached to a casing enclosing the combustion chamber, each locating pin being a sliding fit in one of the housings.

Each locating pin can be screwed into a boss which is permanently attached to the radially outer wall of the combustion chamber adjacent the front or upstream end of the combustion chamber.

The present invention will now be more particularly described with reference to the accompanying drawing in which, Figure 1 shows a gas turbine engine incorporating a combustion chamber front mounting according to the present invention, and Figure 2 is an elevation of the combustion chamber and front mounting of Fig. 1 to a larger scale.

Referring to the figures, a gas turbine engine 10 of the front fan high by-pass ratio type has an annular combustion chamber 1 2 located within a casing 14. The combustion chamber 1 2 has a number of fuel burners 1 6 positioned at its front or upstream end, and the head of each burner is located in a ring of swirl vanes 20 which is fixed axially but can move radially to some extent.

The combustion chamber is mounted at its front end to the casing 14 by a number of circumferentially arranged equi-spaced mountings 22 which restrain axial movement but allow radial movement of the combustion chamber. At the rear or downstream end, the combustion chamber is supported radially and axially in a mounting 24 which allows relative axial movement between the combustion chamber and the mounting.

Each mounting 22 comprises a boss 26 attached to the radially outer wall of the combustion chamber, a locating pin 28 which is screwed into the boss, and a bush housing 30 which is removably attached to the casing 14 and contains a bush (not shown) in which the locating pin is a sliding fit. The locating pin 28 has a head 32 shaped to allow the pin to be removed and replaced in the boss by means of a suitable tool.

When the engine 10 is operating, the casing 14 and combustion chamber 1 2 are subjected to differential thermal expansion and the mountings 22 restrain the front end of the combustor from moving axially relative to the fuel burners 1 6 so that the correct axial relationship between the burners and the combustor is maintained. The accumulation of locked-up stresses in the combustor due to differential thermal growth axially is prevented by the mounting 24 which allows the downstream end of the combustor to move relative to the casing 14.

The mountings 22 allow the combustor to expand in the radial sense, so there may be some frettage between the locating pins and their bushes. This can be reduced or eliminated by suitable lubrication of the sliding surfaces and choice of component materials.

As the mountings are in a relatively cool zone of the engine, lubrication is possible and could be achieved by keeping the housings packed with lubricant. If frettage does occur, the locating pin can be easily removed and replaced without having to strip the engine or even remove the engine from the aircraft.

Thus combustor removal is not dictated by locating pin frettage.

1. A front mounting for a gas turbine engine annular combustion chamber, the mounting comprising a plurality of radially arranged locating pins attached to the combustion chamber adjacent the front end thereof, and a plurality of locating pin housings removably attached to a casing enclosing the combustion chamber, each locating pin being a sliding fit in one of the housings.

2. A front mounting as claimed in claim 1 in which each locating pin is screwed into a boss, the bosses being permanently attached to the radially outer wall of the combustion chamber.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Gas turbine engine combustion chamber mounting This invention relates to a means for mounting a combustion chamber within a casing of a gas turbine engine, and is particularly concerned with a mounting for an annular combustion chamber. There are two main approaches to the mounting of gas turbine engine combustion chambers. The mounting can either be at the front or rear of the combustor. A rigid mounting at the rear end results in relative axial movement between the combustor head and the fuel injector over the engine operating range which can compromise combustion performance. A front mounting avoids this relative movement and can be achieved by the use of rigid bolting, flexible diaphragms or sliding pins. The sliding pins provide an arrangement in which there are no locked up stresses due to differential thermal growth, but problems can arise due to frettage between the pins and their respective locating bushes. The present invention seeks to provide a front mounting for a gas turbine engine combustor using locating pins which are easily replaceable and which can be lubricated to reduce or eliminate frettage. Accordingly, the present invention provides a front mounting for a gas turbine engine annular combustion chamber, the mounting comprising a plurality of radially arranged locating pins removably attached to the combustion chamber adjacent the front end thereof and a plurality of corresponding locating pin housings removably attached to a casing enclosing the combustion chamber, each locating pin being a sliding fit in one of the housings. Each locating pin can be screwed into a boss which is permanently attached to the radially outer wall of the combustion chamber adjacent the front or upstream end of the combustion chamber. The present invention will now be more particularly described with reference to the accompanying drawing in which, Figure 1 shows a gas turbine engine incorporating a combustion chamber front mounting according to the present invention, and Figure 2 is an elevation of the combustion chamber and front mounting of Fig. 1 to a larger scale. Referring to the figures, a gas turbine engine 10 of the front fan high by-pass ratio type has an annular combustion chamber 1 2 located within a casing 14. The combustion chamber 1 2 has a number of fuel burners 1 6 positioned at its front or upstream end, and the head of each burner is located in a ring of swirl vanes 20 which is fixed axially but can move radially to some extent. The combustion chamber is mounted at its front end to the casing 14 by a number of circumferentially arranged equi-spaced mountings 22 which restrain axial movement but allow radial movement of the combustion chamber. At the rear or downstream end, the combustion chamber is supported radially and axially in a mounting 24 which allows relative axial movement between the combustion chamber and the mounting. Each mounting 22 comprises a boss 26 attached to the radially outer wall of the combustion chamber, a locating pin 28 which is screwed into the boss, and a bush housing 30 which is removably attached to the casing 14 and contains a bush (not shown) in which the locating pin is a sliding fit. The locating pin 28 has a head 32 shaped to allow the pin to be removed and replaced in the boss by means of a suitable tool. When the engine 10 is operating, the casing 14 and combustion chamber 1 2 are subjected to differential thermal expansion and the mountings 22 restrain the front end of the combustor from moving axially relative to the fuel burners 1 6 so that the correct axial relationship between the burners and the combustor is maintained. The accumulation of locked-up stresses in the combustor due to differential thermal growth axially is prevented by the mounting 24 which allows the downstream end of the combustor to move relative to the casing 14. The mountings 22 allow the combustor to expand in the radial sense, so there may be some frettage between the locating pins and their bushes. This can be reduced or eliminated by suitable lubrication of the sliding surfaces and choice of component materials. As the mountings are in a relatively cool zone of the engine, lubrication is possible and could be achieved by keeping the housings packed with lubricant. If frettage does occur, the locating pin can be easily removed and replaced without having to strip the engine or even remove the engine from the aircraft. Thus combustor removal is not dictated by locating pin frettage. CLAIMS

3. A front mounting as claimed in claimed in claim 1 in which each locating pin is a sliding fit within a bush contained within the locating pin housing.

4. A front mounting as claimed in claim 1 in which each locating pin housing is packed with lubricant.

5. A front mounting for a gas turbine engine annular combustion chamber constructed and arranged for use and operation substantially as herein described, and with reference to the accompanying drawing.