Design Procedure of a Reverse Flow Combustor for a Helicopter Engine with High Temperature Rise 2011-01-2562

Modern advanced engines are expected to operate with higher combustor temperature rise and lower emissions. These development trends result in more combustor design difficulties. High temperature rise requires more air for complete combustion, hence reducing the amount of cooling air. Emissions consist of CO₂, UHC, NO_x, smoke and water vapor. CO₂ is an unavoidable emission of combustion reaction, whereas emissions of NO_x mainly depend on temperature. A lean primary zone design is required to achieve low NO_x emission. Reverse flow combustors have more difficulties because of the presence of turn section which does not exist in other combustor configurations.

There are many studies in public domain which talk about design of combustors. But none of them gives detailed guide on designing reverse flow combustor. The objective of this paper is to provide a reverse flow combustor design procedure, with emissions and performance analysis. The combustor designed in this study is expected to be used in advanced helicopter engine. Substantial amount of literature is available on conventional combustor designs which mainly include empirical and semi-empirical models plus experiment test methods. All these combustor design methods focus on the direct flow combustor. In this study, a reverse flow combustor design methodology is proposed. The design procedure includes the combustor sizing, fuel injector design, swirl cup design, air distribution along the liner, primary hole design, dilution zone design and the cooling system design. Final dimensions are also shown in a figure, which have been validated with one of the present combustor designs. After finalizing the design of the combustor, overall performance has been evaluated using empirical correlations and equations.