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Prediction of Engine Casing Temperature of Combat Aircraft for various operating conditions needs modeling of convective and radiative heat flow from the jet pipe to the casing. Radiation modeling which implies modeling of multiple reflections and scattering is done here by the radiance-irradiance approach. The engine layout is approximated by three co-axial cylinders and axially discretized. The shape factors (which account for the directional dependence of radiation heat flow) for various configurations needed in radiation modeling are analytically obtained by a sequence of shape factor algebra from standard configurations. The resulting non-linear algebraic equations of combined convection and radiation heat flow are solved by an iterative technique to give the engine casing temperatures which may be used for infrared signature studies.

This paper attempts to bring home the philosophy which lies behind the practical application of air-breathing and rocket engines. The various types of practical engines namely rocket engine, ram jet engine, turbojet engine, turbofan engine (mixed and unmixed exhausts), turboprop engine appear to be principally different. However philosophically, they are all one and the same. To appreciate this philosophy, let us change our frame of interest from the fluid to the jet engine. This leads us to the very first principles of jet propulsion i.e. the generation of thrust from the pressure forces exerted by the fluid on the boundaries and components of the jet engine. Well established mathematical concepts and relationships are available for practically estimating the performance of these engines based on fluid parameters. However philosophically, thrust and propulsive efficiency are sufficient for the philosophical understanding of the generation of variety of aircraft engines.