GB2100409A

GB2100409A - Gas turbine engine fuel burners

Info

Publication number: GB2100409A
Application number: GB8112770A
Authority: GB
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1981-04-24
Filing date: 1981-04-24
Publication date: 1982-12-22
Also published as: DE3213761A1; GB2100409B; FR2504601A1; JPS57187530A

Abstract

In order to prevent the accumulation of carbon on the pintle of a gas turbine engine fuel burner (34), the pintle is hollow and has inlet holes (60) upstream of the fuel inlets (46) so that a small mass flow of compressor delivery air can enter the hollow pintle and flow over the interior surface of the pintle. <IMAGE>

Description

SPECIFICATION Gas turbine engine fuel burners This invention relates to gas turbine engine fuel burners and is particularly concerned with the problem of carbon accretion on parts of airspray type burners, e.g. the central body or pintle which usually extends part way into the engine flame tube. Carbon particles which are produced more readily when the engine is operating at an offdesign point, such as peak power tend to collect on the bluff bases of the burner pintles and gradually a relatively large mass of carbon can become attached to the pintle base.At some point this large carbon mass or parts of it become detached from the pintle and travel through the combustion chamber of the engine and impinge on the downstream components of engine, such as the nozzle guide vanes and the static and rotating blades of the engine turbine, causing erosion of these components or more serious damage.

The present invention seeks to provide a means of preventing the deposition of carbon to any considerable extent and is an improvement in or modification to the invention described and claimed in our co-pending application No.

7909839. In that application, the pintle was hollowed out and a number of apertures were drilled through the wall of the pintle towards the downstream end of the pintle. This arrangement was successful in restraining carbon accretion but it was found that in some conditions, the most downstream apertures were operating rather like miniature fuel injectors, and fuel and air were burning in the apertures. This combustion was damaging the pintle and causing other combustion problems.According to the present invention there is provided a gas turbine engine fuel burner having an annular duct for a flow of fuel and air, the duct being defined by a wall of the fuel burner and a central body supported in said duct, the central body being hollow and having a closed upstream end and an open downstream end with respect to the air flow through said duct, the upstream wall of said central body having a plurality of apertures extending between the annular duct and the interior of the central body, each said aperture having air swirling means to enable some of the air flowing through the annular body to flow over substantially the whole of the interior surface of the central body.

The present invention will now be more particularly described with reference to the accompanying drawings in which; Figure 1 shows a gas turbine engine incorporating one form of fuel burner according to the present invention, Figure 2 shows a portion of the combustion apparatus of a gas turbine engine including one form of fuel burner according to the present invention, Figure 3 shows a section of the fuel burner and pintle of our co-pending application No. 7909838 and Figure 4 is a similar section to Figure 3, but illustrating a fuel burner according to the present invention.

Figure 5 is a section on line V-V in Figure 4 and, Figure 6 shows a modified form of fuel burner according to the present invention.

Referring to Figure 1 a gas turbine engine 10 comprises a single stage fan 12 driven by a turbine 14, an intermediate pressure compressor 1 6 driven by an intermediate pressure turbine 18, a high pressure compressor 20 driven by a high pressure turbine 22, and a combustion apparatus 24. The air propelled by the fan 12 flows through a bypass duct 26 and exhausts through a propulsion nozzle 28 and the gases from the turbines 14, 18 and 22 exhaust through a propulsion nozzle 30. The combustion apparatus 24 shown in Figures 2 and 3 in more detail includes a combustion chamber 32 which in this case is annular, but can be of the can type or the can-annular type, having a number of equi-spaced fuel burners 34 only one being shown.

Each burner 34 has an annular duct 36 defined by a wall 38 and a central body or pintle 40 which is supported by a cruciform shaped bracket 42 in the annular duct. In use, fuel is injected from a manifold 44 in the fuel burner through inclined apertures 46 so that the fuel swirls around the wall 38 in a downstream direction, following a path similar to a low pitch helix. The air flowing through the duct 36 only has an axial component of direction and the pintle is shaped to provide a venturi with an annular outlet 48, so that the air and fuel ar accelerated towards the outlet achieving a maximum shear between the fuel and air, thereby atomising the fuel.

This design results in a pintle which has a bluff downstream base extending partly into the flame tube and any carbon produced in the combustion chamber tends to collect on this base.

The pintle 40 shown more clearly in Figure 3 has a hollowed out interior 50 leaving only a relatively small annular land 52 as compared to the solid circular base which previously existed.

Two rows of three equi-spaced apertures 54 are formed in the wall of the pintle, the axis of each aperture being tangential to a circle of smaller diameter than the internal diameter of the pintle in the plane containing the axis and inclined in a downstream direction.

In operation, a small proportion of the axially flowing air in the annular duct 36 flows through the apertures 54 into the interior of the pintle and then flows over the interior surface of the pintle preventing carbon from being deposited on that surface. Since non or hardly any carbon can accumulate on the pintle, the downstream components of the engine will not be subject to erosion from this source and component life is increased.

However, it has been found that under some operating conditions, fuel and air are present in some of the apertures 54, usually the most downstream apertures, and combustion takes place in and adjacent these apertures and the venturi causing damage to the pintle. Also, the burning of fuel in the apertures and venturi is detrimental to flow through the venturi 48 and causes overall combustion inefficiency.

The modification or improvement according to the present invention is shown in Figure 4, in which like parts have been given the same reference numeral.

The pintle 40, in Figure 4 is completely hollowed out so that the wall thickness is substantially uniform throughout and the pintle has a closed upstream end 54 and an open downstream end 58. The pintle is supported in the duct 36 by three arms 42a which are located at one end in slots 42b on the pintle and at the other end in slots 42c in the wall 38 and are brazed in position. Adjacent the upstream end 56 of the pintle, a plurality of equi-spaced apertures 60 are formed through the wall of the pintle, to allow compressed air from the compressor 20 of the engine 10 to flow into the interior of the pintle 40. This air is swirled as indicated by arrow A in Figure 4, so that the air washes over the inner surface of the pintle to prevent any carbon accretion.The swirling effect can be achieved by the use of a vane or vanes in each aperture or preferably by making the axis of each aperture tangential to a circle of smaller diameter, than the internal diameter of the pintle in a plane containing each said aperture axis.

Since the apertures are at the upstream end of the pintle, i.e. upstream of the fuel inlets 46, there is no possibility of fuel and air being burnt in the apertures. As well as this benefit, because the apertures are well upstream of the control gap 48, the air flowing through the apertures does not affect the air flow through the gap, as does the presence of apertures closer to the downstream end of the pintle.

Referring to Figure 6, the burner illustrated is similar to the burner shown in Figures 4 and 5 and where appropriate the same reference numerals are used for similar components. In this burner the outer air shroud has been deleted to make the burner more suitable for use in a dump diffuser potted head type combustor, the outer air shroud being replaced by a ring of swirler vanes (not shown) through which air flows and which has a similar action as that of the air flowing through the air shroud of the burner of Figures 4 and 5.

Claims

1. A gas turbine engine fuel burner having an annular duct for a flow of fuel and air, the duct being defined by a wall of the fuel burner and a central body supported in said duct, the central body being hollow and having a closed upstream end and an open downstream hollow end with respect to the air flow through said duct, the upstream wall of said central body having a plurality of apertures extending between the annular duct and the interior of the central body each said aperture having air swirling means to enable some of the air flowing through the annular body to flow over substantially the whole of the interior surface of the central body.

2. A fuel burner as claimed in claim 1 in which the apertures each have at least one vane to swirl any incoming air.

3. A fuel burner as claimed in claim 1 in which the axis of each aperture is tangential to a circle of diameter less than the internal diameter of the central body in the plane containing said axis to give a swirl component to any incomong air.

4. A gas turbine engine fuel injector constructed and arranged for use and operation substantially as herein described with reference to and as shown in the accompanying drawings.