NUMERICAL INVESTIGATION OF A SCRAM JET USING DNS METHOD

P.Ganesh Kumar, K. Gowrisankar

Abstract


Heat Transfer is the science that predicts the energy transfer across the materials as result of the temperature difference. It is well known that there are three fundamental modes of heat transfer namely Conduction, Convection and Radiation.

It has become exceedingly important for an engineer to possess a clear understanding of the principles of heat transfer and its applications to a large number of problems. Engineers are constantly confronted with the need to maximize or minimize the heat transfer rates and to maintain the integrity of materials under conditions of extreme temperatures. In order to determine the temperature distribution across the walls of combustion chambers and nozzles that possess hot gases, heat transfer coefficient is an important parameter to be evaluated in heat transfer analysis as the heat transfer in the engine components takes place mainly by convection from the hot gases to the surrounding walls.  It is necessary to combine equations of motion with those of heat conduction. Therefore the need for fluid flow analysis becomes evident while solving heat transfer problems, especially when the heat source is in the form of high temperature fluids as in the case of Propulsion systems.

In recent years there has been a vast increase in interest in supersonic combustion in connection with flight propulsion. In the typical propulsion unit,   propellants enter the combustion chamber, gets ignited and escapes through the nozzle at very high speeds which are supersonic in nature. Because of these gases escaping through the nozzle the rocket receives momentum in the opposite direction according to Newton’s Third Law of Motion.

The present work deals with the heat transfer analysis of the uncooled -combustion chamber. The study includes the temperature distributions across the thickness of the combustion chamber and estimation of the maximum time upto which the system can withstand the temperature under given operating conditions. A VB script code is developed to obtain the temperature distributions with respect to the time across the walls of the combustion chamber. Based on the heat transfer analysis, the maximum permissible test durations are estimated for the present uncooled combustion chamber of different materials with various configurations.. In order to increase the test duration, a cooling system is proposed for further studies.


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