Gas turbine combustion chambers

Abstract

A combustion chamber for a gas turbine made up of outer and inner side walls, the combustion chamber being received in a casing so as to define an annular space between the combustion chamber and the casing in which there flows air for combustion, for dilution, and for cooling the combustion chamber, the side walls of the combustion chamber being pierced by a plurality of holes in which bushings of substantially elliptical right section are fixed to define air injection passages for injecting air into the combustion chamber, each bushing having a peripheral wall in which at least one additional orifice is formed opening out into the combustion chamber in the immediate vicinity of the side wall of the combustion chamber in which said bushing is fixed so that the air passing through said orifice flows substantially along said peripheral wall, the peripheral wall of each bushing having at least one groove opening out into the annular space and into which the or each orifice opens out so as to be fed with air and so as to cool the peripheral wall of the bushing.

Description

[0001] The present invention relates to the field of combustion chambers for airplane gas turbine engines, and more particularly to combustion chambers having air injection orifices through their walls.[0002] A combustion chamber for a gas turbine is disposed in conventional manner inside a housing that constitutes a casing. It is made up of inner and outer side walls that are united by an end wall on which injector systems are mounted that are distributed over one or more heads.[0003] Conventionally, the air coming from the high pressure compressor of the turbine is admitted into the combustion chamber. A fraction of this air feeds the combustion zone axially via end wall injector systems and another fraction enters transversely via primary air injection holes pierced through the inner and outer side walls of the combustion chamber. A further fraction of this air, referred to as a "dilution" fraction, is also introduced transversely, but further downstream within the combustion cha...

AI Technical Summary

Benefits of technology

[0010] The present invention thus seeks to mitigate such drawbacks by proposing bushings that are fixed in the air injection holes of the combustion chamber while providing passages for cooling air to improve the temperature behavior of the combustion chamber walls around said air injection holes, while maintaining a long lifetime.

[0012] The elliptical shape of the bushings serves to reduce the aerodynamic blocking due to the flow of cooling air and thus to attenuate degradation of the cooling film in the vicinity of the injection holes. In addition, the presence of a peripheral groove makes it possible to ensure that air is fed to one or more orifices opening out into the groove, and also makes it possible to provide effective cooling of the peripheral wall of the bushing adjacent to its front face which is exposed to the hot gases.

[0013] The portions of the bushings that project into the combustion chamber can match substantially the concave shape of the combustion chamber wall so as to minimize degradation of the film of cooling air.

Problems solved by technology

It is known that piercing multiple perforation orifices in the vicinity of primary combustion air and dilution air injection orifices is undesirable since there is a danger of causing cracks to propagate via said orifices.

Unfortunately, the absence of local cooling in this zone gives rise to the appearance of hot points and temperature gradients which disturb the high temperature behavior of the combustion chamber side walls.

In addition, the impact of the air and fuel mixture against the walls of the combustion chamber tends to form hot points at any point within the combustion zone.

Nevertheless, none of those solutions appears to be satisfactory for reducing the temperature gradients which appear all around the air injection holes.

In addition, the front portions of the peripheral walls of these bushings which project into the combustion chamber are exposed to hot gases.

As a result these bushings tend to become damaged quickly.

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