GB2044913A - Gas turbine burner - Google Patents

Abstract

A gas turbine fuel burner, comprises a pintle with an annular slot 34, forming a neck thereby reducing the heat flow path area. This has the effect of making the pintle run at a high enough temperature to prevent carbon deposition. <IMAGE>

Description

SPECIFICATION Improvements in or relating to 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 such burners, e.g. the central body or pintle which usually extends partway into the engine flame tube. Carbon particles which are produced more readily when the engine is operating at an off-design 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. According to the present invention there is provided a gas turbine engine fuel burner having an annular duct for the 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 having an upstream portion and a downstream portion, the two portions being joined together by a portion of reduced cross-sectional area as compared to the cross-sectional area of the upstream and downstream portions adjacent the junction between said two portions.

The present invention will now be more particularly described with reference to the accompanying drawings in which; Figure 1 shows a portion of the combustion apparatus of a gas turbine engine including one form of fuel burner according to the present invention and, Figure 2 shows a section of the fuel burner and pintle of Figure 1 to a larger scale.

Referring to the Figures, a gas turbine engine combustion apparatus, includes a combustion chamber 10 which in this case is annular, but can be of the can-type or the can-annular type and a number of equi-spaced fuel burners 12, only one of which is shown.

Each burner 12 has annular duct 14 defined by a wall 16 and a central body or pintle 18 which is support by a cruciform shaped bracket 20 in the annular duct. In use, fuel is injected from a manifold 22 in the fuel burner through inclined apertures 24 so that the fuel swirls around the wall 16 in a downstream direction, following a path similarto a low pitch helix. The air flowing through the duct 14 only has an axial component of direction and the pintle is shaped to provide a venturi with an annular outlet 26, so that the air and fuel are 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.

It has been found that if in operation of the combustion apparatus, the pintle 18 runs above a certain temperature, carbon produced in the combustion apparatus tends not to accumulate to any extent on it. The pintle 18 shown in detail in Figure 2 is designed to operate at or above this critical temperature and is provided with an annular slot 28 which divides the pintle into upstream and downstream portions 30 and 32 respectively, which are joined together by a neck 34, or portion of reduced cross-sectional area.

Without the slot 28, the heat from the pintle would normally be dissipated in part to the body of the fuel burner via the bracket 20, but in the main by direct cooling brought about by the airflowthroughthe duct 14 over the area of the pintle. The heat now has to be conducted through a smaller cross-sectional area, e.g. the neck 34 and as a consequence the downstream portion 32 of the pintle runs at a much higher temperature and carbon does not accumulate. Thus the downstream components of the engine will not be subject to erosion from this source and component life will be increased.

The diameter Y of the neck and the distance X of the neck from the downstream end of the pintle can be varied according to circumstances as can the width of the slot 34.

The factors dictating the dimensions X and Y include the temperature at which the pintle normally runs and the temperature at which it is required to run, and the structural integrity of the pintle, although the slot 28 should be as close as possible to the downstream end of the pintlewhilst also meeting the requirements determined by the above factors because the pintle is mainly cooled by the airflow over the area A.

1. A gas turbine engine fuel burner having an annular duct for the 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 having an upstream portion and a downstream portion, the two portions being joined together by a portion of reduced cross-sectional area as compared to the cross-sectional area of the upstream and downstream portions adjacent the junction between said two portions.

2. Afuel burner as claimed in claim 1 in which the central body tapers outwardly in a downstream direction, the upstream and downstream portions being defined by an annular slot in the central body which forms a neck between said two portions.

3. Afuel burner as claimed in claim 1 in which the ratio between the distance of the annular slot from the downstream end of the central body and the diameter of the neck lies within the range 0.268 to 1.045.

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

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to 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 such burners, e.g. the central body or pintle which usually extends partway into the engine flame tube. Carbon particles which are produced more readily when the engine is operating at an off-design 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. According to the present invention there is provided a gas turbine engine fuel burner having an annular duct for the 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 having an upstream portion and a downstream portion, the two portions being joined together by a portion of reduced cross-sectional area as compared to the cross-sectional area of the upstream and downstream portions adjacent the junction between said two portions. The present invention will now be more particularly described with reference to the accompanying drawings in which; Figure 1 shows a portion of the combustion apparatus of a gas turbine engine including one form of fuel burner according to the present invention and, Figure 2 shows a section of the fuel burner and pintle of Figure 1 to a larger scale. Referring to the Figures, a gas turbine engine combustion apparatus, includes a combustion chamber 10 which in this case is annular, but can be of the can-type or the can-annular type and a number of equi-spaced fuel burners 12, only one of which is shown. Each burner 12 has annular duct 14 defined by a wall 16 and a central body or pintle 18 which is support by a cruciform shaped bracket 20 in the annular duct. In use, fuel is injected from a manifold 22 in the fuel burner through inclined apertures 24 so that the fuel swirls around the wall 16 in a downstream direction, following a path similarto a low pitch helix. The air flowing through the duct 14 only has an axial component of direction and the pintle is shaped to provide a venturi with an annular outlet 26, so that the air and fuel are 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. It has been found that if in operation of the combustion apparatus, the pintle 18 runs above a certain temperature, carbon produced in the combustion apparatus tends not to accumulate to any extent on it. The pintle 18 shown in detail in Figure 2 is designed to operate at or above this critical temperature and is provided with an annular slot 28 which divides the pintle into upstream and downstream portions 30 and 32 respectively, which are joined together by a neck 34, or portion of reduced cross-sectional area. Without the slot 28, the heat from the pintle would normally be dissipated in part to the body of the fuel burner via the bracket 20, but in the main by direct cooling brought about by the airflowthroughthe duct 14 over the area of the pintle. The heat now has to be conducted through a smaller cross-sectional area, e.g. the neck 34 and as a consequence the downstream portion 32 of the pintle runs at a much higher temperature and carbon does not accumulate. Thus the downstream components of the engine will not be subject to erosion from this source and component life will be increased. The diameter Y of the neck and the distance X of the neck from the downstream end of the pintle can be varied according to circumstances as can the width of the slot 34. The factors dictating the dimensions X and Y include the temperature at which the pintle normally runs and the temperature at which it is required to run, and the structural integrity of the pintle, although the slot 28 should be as close as possible to the downstream end of the pintlewhilst also meeting the requirements determined by the above factors because the pintle is mainly cooled by the airflow over the area A. CLAIMS

1. A gas turbine engine fuel burner having an annular duct for the 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 having an upstream portion and a downstream portion, the two portions being joined together by a portion of reduced cross-sectional area as compared to the cross-sectional area of the upstream and downstream portions adjacent the junction between said two portions.

2. Afuel burner as claimed in claim 1 in which the central body tapers outwardly in a downstream direction, the upstream and downstream portions being defined by an annular slot in the central body which forms a neck between said two portions.

3. Afuel burner as claimed in claim 1 in which the ratio between the distance of the annular slot from the downstream end of the central body and the diameter of the neck lies within the range 0.268 to 1.045.

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