Patent Publication Number: US-4321794-A

Title: Gas turbine engine fuel burners

Description:
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 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. According to the present invention there is provided a gas turbine engine fuel burner having an annular duct arranged to receive a flow of compressed air, means for injecting fuel into said duct, 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 open at its downstream end with respect to the air flow through said duct, a plurality of apertures in the wall of said central body extending between the annular duct and the interior of the central body to enable some of the air flowing through the annular duct to flow over the interior surface of the hollow base of the central body. 
    
    
     The present invention will now be more particularly described with reference to the accompanying drawings in which; 
     FIG. 1 shows a portion of the combustion apparatus of a gas turbine engine including one form of fuel burner according to the present invention, 
     FIG. 2 shows a section of the fuel burner and pintle of FIG. 1 to a larger scale, 
     FIG. 3 is a view on arrow `A` in FIG. 2 disclosing the pintle and with the support bracket omitted for the purpose of clarity, 
     FIG. 4 is a section on line 4--4 in FIG. 2, 
     FIG. 5 is a section on line 5--5 in FIG. 2, 
     FIG. 6 is a modified form of the pintle shown in FIG. 2, 
     FIG. 7 is a view on arrow `B` in FIG. 6, 
     FIG. 8 is a section on line 8--8 in FIG. 6 and, 
     FIG. 9 is a section on line 9--9 in FIG. 6. 
    
    
     Referring to the Figures and more particularly to FIGS. 1 to 5 inclusive, 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, having a number of equi-spaced fuel burners 12 only one being 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 similar to 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. 
     The pintle 18, shown more clearly in FIGS. 2 to 5 inclusive has a hollowed out interior 28 leaving only a relatively small annular land 30 as compared to the circular base which previously existed. Two rows of three equi-spaced apertures 32 are formed in the wall of the pintle, the axis of each aperture being tengential 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 (indicated by arrow D). 
     FIGS. 6 to 9 show a modification of the pintle shown in the preceding Figures n that each row of apertures contains four apertures 32 the axis of each aperture being arranged as previously described. 
     In operation, a small proportion of the axially flowing air in the annular duct 14 flows through the apertures 32 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 none 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.