Key technologies for thermodynamic cycle of precooled engines: A review

Abstract

The precooled combined cycle engines were proposed to overcome the limitation of Mach number due to high-temperature inlet. However, there has been little discussion about the thermodynamic cycle of these engines. Therefore, the current research progress and key technologies in the precooled engine thermodynamic cycle are analyzed and summarized in detail in this study. The main precooled engines, specifically ATREX and SABRE, are compared. The engine precooling cycle can be divided into direct and indirect precooling cycles. By comparing the performance of the direct precooling cycle ATREX engine in the non-precooling and precooling modes, the advantages of this engine in terms of specific thrust, compressor boost ratio, and flight Mach number are examined. The SABRE engine with an indirect precooling cycle not only solves the problem of hydrogen embrittlement of the precooler, but also achieves higher thrust and specific impulse than the ATREX engine. However, the ATREX engine with a direct precooling cycle is simpler in structure and has less adjusting variables, and thus, it is suitable for application in high-speed aircraft with a low flow rate. In addition, comparing the precooling cycle working mediums, the hydrogen medium shows excellent performance but has a limited aircraft flight range. Conversely, the use of a hydrocarbon fuel in the aircraft results in a longer flight range but with relatively low performance. Therefore, a development trend toward multi-fuel hybrid use can be expected.