Optimization of System Parameters for Liquid Rocket Engines with Gas-Generator Cycles

摘要

System design of liquid rocket engines must consider engine performance, weight, cost, and reliabilitynrequirements. A general design optimization framework has been developed in this paper to select the best systemnparameters for liquid rocket engines with gas-generator cycles. The object is to maximize the specific impulse andnvacuum thrust-to-weight ratio of the engine with given system requirements and design assumptions by changingnthrust-chamber pressure andmixture ratio.The systemanalysis, alongwith the engineweight estimation, is based onna modular scheme. Multidisciplinary design optimization formulations including multidisciplinary feasible andncollaborative optimization are used, evaluated, and compared during the optimization process. Several techniques ofnmulti-objective processing are also used to identify the Pareto frontier and the optimal compromise solutions. Anproposed cryogenic-propellant engine using liquid oxygen and hydrogen with a gas-generator cycle is studied as anspecific example. Moreover, uncertainties in the engine operation, such as thrust-chamber pressure and mixturenratio, are taken into account as random variables in the reliability-based optimization. Results are presented tonillustrate the tradeoff between the engine performance and reliability requirements.