Multiple cycles overall analysis and evaluation for fuel direct/indirect precooled engines: A unified thermodynamic model based approach

Precooled engines are promising power for future aerospace transportation vehicles. The engines family is characterized by a rich variety of cycle configurations. A unified cycle model that can provide a spectrum view for the entire family is recognized as crucial in creating deeper insights to illustrate the application potentials, the evolution tendency and the synthesizing of new engines of precooled cycles. While attempts concerning spectrum view based modeling for fuel direct and indirect precooled engines have been carried out respectively, a consistent cycle model and the related analysis framework applicable to the wholistic precooled family is still absent to date due to the obvious discrepancies between the different precooling schemes applied. To bridge this modeling gaps, an equivalent thermodynamic conversion method is introduced in this work, through which a more generalized and unified precooled cycle model is then constructed. The model makes known that the differences among the different precooled engines lie solely in the way how its precooling-compression sub-system (PCS) is implemented. Thereafter performances for four elementary PCS implementations identified are analyzed, with the superiority of indirect precooled engines is clarified accordingly. The current study may be helpful in guiding the design, assessment and optimization of precooled cycle engines.