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,
NOx, smoke and water vapor. CO₂ is an unavoidable
emission of combustion reaction, whereas emissions of
NOx mainly depend on temperature. A lean primary zone
design is required to achieve low NOx 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.