A Review of Studies on Ramjet and Scramjet Engines from an Energy–exergy Viewpoint

The second law of thermodynamics and exergy is an important issue in the analysis of propulsion systems that have been highly regarded by researchers in recent years. Studies show that the analysis of the first law in air propulsion systems alone has low scientific value, and for a complete study of a system, the second law and exergy should also be considered. Thermodynamic analysis of supersonic air engines, especially Ramjet and Scramjet engines, with the aim of studying their performance, has attracted the attention of many researchers in the last decade. In this method, using thermodynamic laws and exergy analyzes, Ramjet and Scramjet motors are systematically analyzed, and their optimal state is extracted. The main purpose of this study is to review and present the latest research findings in this field, focusing on Ramjet and Scramjet engines.