The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines, which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder flow characteristics. This paper reviews the development history and characteristics of gas exchange types, as well as the current state of theory and the validation methods of gas exchange technology, while also discusses the trends of cutting-edge technologies in the field. This paper provides a theoretical foundation for the optimization and engineering design of gas exchange systems and, more importantly, points out that the innovation of gas exchange types, the modification of theoretical models, and the technology of variable airflow organization are the key future research directions in this field.

As an auxiliary mechanical device, Air Turbine Starter (ATS) uses compressed air as power source to start and drive the engine. It withstands the impact of high-pressure airflow during operation, which may cause collision between key components. For this reason, it is necessary to investigate the transient dynamics of ATS rotor system. However, different from the traditional dual rotor structure, ATS uses magnetic reduction gear (MRG) as a reduction unit, which involves multiple physical fields such as magnetic field and stress field, bringing challenges to transient dynamics analysis. In this paper, the magnetic interaction forces between various rotors are innovatively simplified into the form of springs, and added to the solution model to achieve the decoupling of multiple physical fields. On this basis, the transient displacement response of MRG-ATS has been analyzed using transient dynamics theory. The results indicate that the transient displacement of the rotor system has obvious characteristics of oscillation attenuation. The study reveals the feasibility of MRG-ATS application under transient shock.