Precooler-design & engine-performance conjugated optimization for fuel direct precooled airbreathing propulsion

Highlights: • Design study of precooler is presented from the perspective of Pareto optimality. • Tradeoff feature is observed between the selected optimization objectives. • Significant increase in specific impulse can only be made within a certain range. • Adoption of larger precooling temperature benefits both the precooler and cycle. • Developing high performance intake is extremely important for precooled engines. -- Abstract: Design study of the precooling heat exchanger specified for high speed airbreathing propulsion was carried out from the perspective of overall engine performance. The precooler proposed for the SABRE engine was adopted as the representative configuration for evaluation. Design procedure of the precooler was developed and incorporated into a cycle analysis model such that the variation in engine performance can be assessed as the design inputs is altered. By means of the differential-evolution algorithm, the design characteristics of the precooler were clarified through the idea of Pareto-Optimality. Precooler total mass and axial length, together with engine specific impulse, was included as optimization objectives on account of the results of parametric analysis. Pareto-optimal-fronts were obtained with the influence of some key design parameters such as the precooling temperature and the intake efficiency was analyzed. The results show that precooler design is a tradeoff between the optimization objectives considered. Selection of a larger precooling temperature helps to increase engine specific impulse and reduce the mass of precooler, although engine specific thrust is decreased slightly, whereas larger intake efficiency is extremely preferred for precooled cycles from not only the performance side of the engine, but more importantly, the geometry side of the precooler.