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LOCALLY THICKENED CMC COMBUSTOR LINER

IP.com Disclosure Number: IPCOM000245271D
Publication Date: 2016-Feb-24

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention relates to gas turbine engine combustors. Specifically, the invention relates to strain and stress reduction in combustor liners made from ceramic matrix composite (CMC) material.

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LOCALLY THICKENED CMC COMBUSTOR LINER

TECHNICAL FIELD

    The invention relates to gas turbine engine combustors. Specifically, the invention relates to strain and stress reduction in combustor liners made from ceramic matrix composite (CMC) material.

BACKGROUND

    Combustor liners are generally used in the combustion section of a gas turbine engine, which is located between the compressor and turbine sections of the engine. Combustors generally include an exterior casing and interior combustor radially inner and outer liners between which fuel is burned producing a hot gas, usually at an intensely high temperature such as 2,000 °F or even higher. To prevent this intense heat from damaging the casing structure before it exits to a turbine, a combustor liner is provided in the interior of the combustor. The combustor liner helps to prevent the combustion heat from damaging the surrounding engine. Such liners can be formed from high temperature withstanding CMC materials.

    Because they are exposed to heat generated by the combustion process, combustor liners are cooled to meet life expectancy requirements. Liner cooling is commonly provided by diverting a portion of the compressed air (which is relatively cool) and causing it to flow over the outer surfaces of the liners. In addition, a thin layer or film of cooling air is provided along the combustion side of the liners by directing cooling air flow through cooling holes formed in the liners. This technique, referred to as film cooling, reduces the overall thermal load on the liners


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because the mass flow through the cooling holes dilutes the hot combustion gas next to
the liner surfaces, and the film of cooling air provides convective cooling of the liner walls.

    Multi-hole cooled liners use a large number of very small cooling holes formed through the liners at a shallow angle. Compressor air passes through the cooling holes to create closely packed, discrete jets of cooling air that coalesce and produce the film of cooling air on the combustion side of the liners. The cooling holes are generally distributed over the whole liner so as to provide a constant replenishing of the cooling film along the entire length of the liner. Multi-hole film cooling is particularly effective in continuous replenishment of an existing film and provides the added benefit of bore cooling of the liner substrate.

    Regardless of the cooling approach, liners tend to develop hot spots or regions during operation. Different liner designs develop hot spots in different locations. Where hot spots occur can be a function of many factors including the configuration of the liners, dome assemblies and swirlers. For instance, the swirl of the combustion flow induced by the swirlers can cause hot gases to impinge against distinct regions of the liner surfaces. These regions tend to experience a loss of cooling film effectiveness and thus be more susceptible to thermal degradation. This effect, which is usual...