Thermodynamic analysis of an air suspension compressor for new energy vehicles under variable back-pressure

During the operation of new energy vehicles, the pressures of the air springs and the reservoir dynamically change in response to road conditions and vehicle loads. Consequently, the air suspension compressor must operate under variable back-pressures to accommodate pressure variations within the air suspension system. This study focuses on a miniature oil-free piston compressor used in the air suspension system of new energy vehicles, with particular emphasis on its operating states and thermodynamic characteristics under unsteady, variable back-pressure conditions (0.1–1.5 MPa). A combined air suspension compressor-reservoir model was established to analyze the thermodynamic performance and inflation characteristics of the compressor. Furthermore, a test platform was constructed for evaluating the variable back-pressure characteristics of the air suspension compressor, and thermal performance tests were conducted on the prototype. These results showed that under extremely high back pressure, the combined effect of expansion within the clearance volume and external leakage was the primary cause of the reduction in the air suspension compressor inflation. Additionally, at high pressure ratios, expansion and external leakage shifted the peak resistance torque of the compressor motor, causing fluctuations in motor speed and subsequently degrading the air suspension compressor inflation performance. Compared to conventional inflation conditions (0.6 MPa), the volumetric efficiency of the air suspension compressor decreased by 69%, and the isothermal indicated efficiency decreased by 48.1% when the maximum pressure of the air suspension system (1.5 MPa) was reached, leading to a sharp deterioration in air suspension compressor performance. Therefore, better oil-free sealing materials, a more compact clearance volume design, and multi-stage configuration are prospects for adapting to higher operating pressures. This study lays a theoretical foundation for subsequent performance optimization and air suspension compressor design.