GB2028488A

GB2028488A - Gas Turbine

Info

Publication number: GB2028488A
Application number: GB7922372A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1978-08-19
Filing date: 1979-06-27
Publication date: 1980-03-05
Also published as: GB2028488B

Abstract

A gas turbine combustion chamber 10 comprises a plurality of primary air inlets 20 with associated swirling means 26, and a plurality of fuel injectors located in fuel injector apertures 22, the fuel injectors and primary air inlets being arranged so that at least two primary air inlets are located between any two fuel injectors, the primary air all being swirled in one direction so that the fuel from one injector is sheared in opposing directions by the swirling primary air from adjacent primary air inlets. Little or no air enters the combustion chamber in the region of the fuel injectors and any air that does enter in that region is not swirled. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Combustion Chambers This invention relates to combustion chambers particularly for use in gas turbine engines and is concerned with enabling such combustion chambers to operate on low grade fuels, such as diesel whilst keeping the emissions of smoke or carbon particles to acceptable levels. Many methods of controlling smoke or carbon particles have been proposed and tested for example, utilising very high combustion temperatures, having a relatively weak fuel/air mixture in the primary zone, staged fuel injection and improving the mixing of fuel and air in the primary zone to obtain a more homogeneous fuel/air mixture.

The present invention is concerned with providing a combustion chamber with improved means for mixing fuel and air in the primary zone of the combustion chamber.

According to the present invention there is provided a combustion chamber arrangement for a gas turbine engine comprising at least one combustion chamber; the or each combustion chamber having a closed upstream end, an open downstream end, inlets in the walls thereof for the flow of dilution air, the closed upstream end having a ring of circumferentially arranged primary air inlet apertures and at least one fuel inlet aperture, the or each fuel inlet aperture being arranged to receive a fuel injector means, each primary air inlet aperture having means for imparting a swirling motion to the primary air, the ring of primary air inlet apertures being associated with at least one fuel inlet aperture.

In a preferred arrangement, the invention provides an annular combustion chamber having a closed upstream end and an open downstream end, inlets in the walls thereof for the flow of dilution air, the closed upstream end having a ring of circumferentially arranged primary air inlet apertures interspersed with a ring of fuel inlet apertures, each fuel inlet aperture being arranged to receive a fuel injector means, each primary air inlet aperture having means for imparting a swirling motion to the primary air, one or more of the primary air inlet apertures being arranged between any two of the fuel inlet apertures.

Two primary air inlet means may be arranged between any two of the fuel inlet apertures and the primary air swirling means may comprise a number of angled vanes.

The swirling means may be arranged so that the direction of rotation of the swirling primary air is the same for each air inlet aperture or the swirling means may be arranged so that the dii;ection of rotation of the swirling air from some of the air inlet means is opposite to that of the primary air issuing from the remaining air inlet apertures.

Each primary air inlet may have a deflector which acts to control both the angle at which the swirling primary air enters the combustion chamber and the spread of the mass of swirling primary air.

The present invention will now be more particularly described with reference to the accompanying drawings in which; Figure 1 shows an elevation of one form of combustion chamber according to the present invention, Figure 2 is a partial section to a smaller scale on line 2-2 in Figure 1, Figure 3 is a view on arrow '3' in Figure 1, Figure 4 is a view on arrow '4' in Figure 1, Figure 5 is a section on line B-B in Figure 4.

Figure 6 is a section on line C-C in Figure 3, Figure 7 is a section line D-D in Figure 3, Figure 8 shows a further combustion chamber according to the present invention.

Referring to the Figures, an annular combustion chamber 10 for a gas turbine engine (not shown) comprises a closed upstream end 12, and open downstream end 14 and a plurality of inlets 1 6 in walls 1 8 for the inflow of dilution air.

The upstream end 12 has a ring of circumferentially spaced primary air inlet apertures 20 interspersed with fuel inlet apertures 22, in each of which apertures an airspray fuel injector 24 (shown diagrammatically) is located.

Each primary air inlet aperture 20 has a swirler means 26 which is arranged to impart a swirling motion to the primary air as it enters the combustion chamber, all the swirlers 26 giving the primary air the same direction of rotation.

Each swirler comprises a number of angled vanes 26 supported by a ring 30 which itself supports a central boss 32 by means of three arms 34. A deflector or pintle 26 is adjustably mounted on a bolt 38 which is screwed into the boss 32.

The air inlet apertures 20 and fuel inlet apertures 22 are arranged in assemblies 40, each assembly comprising a fuel inlet aperture 22 flanked by an air inlet aperture 20 on each side.

When the assemblies are placed together to form the upstream end 12 of the combustion chamber any two fuel inlet apertures have two air inlet apertures between them.

Each assembly 40 (see particularly Figures 3, 4 and 5) comprises a base plate 42 and a front plate 44 which between them define a plenum chamber 46. The base plate 42 has a plurality of apertures 48 through which cooling air can flow into the plenum chamber and thus cool the plate 44, the cooling air then passes out of the plenum chamber through a large number of relatively small diameter holes 50.

In operation, fuel and unswirled air enters the combustion chamber through the fuel injectors 24 and primary air from the compressor of the gas turbine engine enters through the swirlers 26.

The fuel from each injector becomes rapidly entrained with the mass of swirling air entering though the swirler on each side of it. Because the swirlers each rotate the primary air in the same direction, the fuel from each injector tends to be sheared into, two parts, one part being entrained with the primary air entering on one side of the fuel injector and the other part being entrained with the primary air entering on the other side of the fuel injector.This can be illustrated by reference to Figure 3, in which it will be seen that the left hand air swirler tends to pick up the fuel from the left hand side of the fuel injector and direct it towards the inner wall of the combustion chamber whilst the right hand air swirler tends to pick up the fuel from the right hand side of the fuel injector and direct it towards the outer wall of the combustion chamber The fuel and air thus became intimately mixed in a relatively short time and in a relatively small volume.

The pintles 36 also operate to control the angle at which the swirling mass of primary air enters the combustion chamber and also acts to confine the downstream spread of the primary air. This is achieved by a momentum balance of swirler and pintle airflows arrived at by adjusting the pintle outlet gap (X in Figure 6) thus resulting in a larger swirler exit angle with consequent high air to fuel shear areas in a very short downstream distance.

The deflectors whilst assisting in the control of the primary air, are not essential to the satisfactory operation of the invention and may be omitted, if desired. However, the use of a device such as the pintle for the control outlined above is most useful, and for a given swirler surface area allows larger quantities of air to be mixed within a short time and in a relatively small volume.

The pintles 26 also operate to control the angle at which the swirling mass of primary air enters the combustion chamber and also acts to confine the downstream spread of the primary air. This is achieved by a momentum balance of swirler and pintle airflows arrived at by adjusting the pintle outlet gap (X in Figure 6) thus resulting in a large swirler exit angle with consequent high air to fuel shear areas in a very short downstream distance.

The deflectors whilst assisting in the control of the primary air, are not essential to the satisfactory operation of the invention and may be omitted, if desired. However, the use of a device such as the pintle for the control outlined above is most useful, and for a given swirler surface area allows larger quantities of air to be mixed within a short time and small volume, i.e. close to the upstream end of the combustion chamber and consequently the fuel injection points.

A combustion chamber according to the invention has been found to operate on diesel fuel without producing black smoke at any power or white smoke at the engine idle condition, whilst also improving combustion efficiency at idle.

The invention has been described above showing two air inlet apertures between two adjacent fuel inlet apertures, but the number of primary air inlet apertures between any two adjacent fuel inlet apertures can be varied to suit the circumstances, provided at least one primary air inlet aperture is located between any two adjacent fuel inlet apertures.

Referring to Figure 8, the invention has been applied to a combustion chamber of the tubo or can-annular type in which a number of individual cylindrical combustion chambers 100 are enclosed with an annulus 102 defined by an inner wall 104 and outer wall 106. Each chamber 100 has a closed upstream end provided with a central fuel inlet aperture 108 in which is located a fuel injector 110 and a number of equi-spaced air inlet apertures 112 each having means 114 for imparting a swirling motion to the incoming primary air.

The swirling means 114 can be as described in relation to the embodiment of the invention descibed above and the operation of the swirling means is such that fuel and primary air are rapidly mixed within a short distance of the upstream end of the combustion chamber.

The direction in which the swirlers rotate the primary air is the same in the case of the embodiments of the invention, illustrated and described, but if circumstances demand it can be arranged for a group or groups of swirlers to rotate the primary air in the opposite direction to that of the remaining group or groups of swirlers.

It will be noted that one feature of the present invention is that each fuel injector does not have a co-axial swirling air inlet associated with it and similarly each air inlet and associated swirler does not have an associated co-axial fuel injector. It is a feature of the invention that the air inlet apertures and swirlers are circumferentially or radially spaced away from the fuel injector apertures and thus the fuel injectors, when in use.

Claims

1.-A combustion chamber arrangement for a gas turbine engine, the arrangement comprising at least one combustion chamber, the or each combustion chamber having a closed upstream end, an open downstream end, inlets in the wall thereof for the flow of dilution air, the closed upstream end having a ring of circumferentially arranged primary air inlet apertures and at least one fuel inlet aperture, the or each fuel inlet aperture being arranged to receive a fuel injector means, each primary air inlet aperture having means for imparting a swirling motion to the primary air, the ring of primary air inlet apertures being associated with at least one fuel inlet aperture.

2. A combustion chamber arrangement as claimed in claim 1 comprising an annular combustion chamber having a closed upstream end and an open downstream end, inlets in the walls thereof for the flow of dilution air, the closed upstream end having a ring of circumferentially arranged primary air inlet apertures interspaced with a ring of fuel inlet apertures, each fuel inlet aperture being arranged to receive a fuel injector means, each primary air inlet having means for imparting a swirling motion to the primary air, one or more of the primary air inlet apertures being arranged between any two of the fuel inlet apertures.

3. A combustion arrangement as claimed in claim 2 in which at least two primary air inlet means are arranged between any two of the fuel inlet apertures.

4. A combustion arrangement as claimed in claim 1 in which the means for imparting a swirling motion to the primary air comprises a number of angled vanes located in each primary air inlet aperture.

5. A combustion arrangement as claimed in claim 1 in which the means for imparting a swirling motion to the primary air are arranged to swirl the primary in the same direction of rotation at each primary air inlet aperture.

6. A combustion arrangement as claimed in claim 1 in which the means for imparting a swirling motion to the primary air is arranged so that the direction of rotation of the swirling primary air from some of the primary air inlet means is opposite to that of the primary air from the remaining air inlet apertures.

7. A combustion arrangement as claimed in claim 1 in which each primary air inlet aperture has a variable area deflector through which the primary air enters the combustion chamber.

8. An annular combustion chamber for a gas turbine engine having a closed upstream end, an open downstream end, inlets in the wall thereof for the flow of dilution air, the closed upstream end having a plurality of circumferentially arranged primary air inlet apertures and a plurality of circumferentially arranged fuel injector apertures, a fuel injector located in each said fuel injector aperture, each said primary air inlet aperture having associated primary air swirling means, the fuel injectors and the primary air inlet apertures being arranged with respect to one another, so that at least two primary air inlet apertures are located between any two fuel injectors, the primary air swirling means being arranged to swirl the primary air from each primary air inlet aperture in the same direction of rotation, all the primary air entering through said inlet apertures being swirled while any air entering the combustion chamber around or through each fuel injector being non-swirled.

9. A can-annular combustion system for a gas turbine engine comprising an annular housing, a plurality of equi-spaced circumferentially arranged cylindrical combustion chambers located in said annular housing, each said chamber having a central fuel injector located in a fuel injector aperture in the upstream end of said chamber, a plurality of equi-spaced primary air inlet apertures in said head, each said primary air inlet aperture having of an associated primary air swirling means arranged to swirl the primary air in the same direction from each of said primary air inlet apertures, all the primary air entering the combustion chamber through said inlet apertures being swirled and any air entering the combustion chamber around or through the fuel injector being non-swirled.

10. A combustion chamber arrangement for a gas turbine engine constructed and arranged for use and operation substantially as herein described with reference to and as shown in Figures 1 to 7 and Figure 8 of the accompanying drawings.