Structural Integrity Assessment of An Indigenously Developed Semi-Cryogenic Engine Component Based on FE Stress Analysis

Semi-cryo engine is designed to operate with LOX (oxidiser) and special grade kerosene (fuel) as propellant. The engine generates thrust by converting the chemical energy of this propellant into kinetic energy of hot gas in the thrust chamber assembly. Thrust chamber assembly comprises of injector head assembly, the combustion chamber, and the convergent-divergent nozzle assembly. In the injector head assembly, proper injection of propellant in the desired mixture ratio takes place, and the resultant product is injected into the combustion chamber through injector elements. Injector head assembly consists of the Gas duct, Diffuser, and Mixer assembly, which are welded together. During operating condition, the injector head assembly is subjected to high pressure and high temperature loads. The response of the structure under these loads is non-linear. Therefore, finite element analysis is called upon to check the structural integrity before putting it into actual engine hot test conditions. An acceptance pressure test at room temperature is devised to screen the quality of the assembly. The response of the structure to this test is evaluated by means of finite element simulations. The FE simulations are performed using the ANSYS FEA package, and a material model based on test data is used to account for their non-linear behaviour at service conditions. Based on the results of FE simulations, necessary modification in the configuration of the gas duct was carried out so that they conform to the requirements spelt out for launch vehicle systems as per relevant standards. Subsequently, analysis was done to ensure the structural integrity of the modified configuration for acceptance pressure test condition and maximum operating condition.