Opposed-piston free-piston engine generators (OFPEGs) have emerged as a promising technology for next-generation hybridized and electrified transportation systems, offering the potential for high efficiency, reduced mechanical complexity, and favorable noise, vibration, and harshness (NVH) characteristics. By eliminating the conventional crankshaft mechanism and directly coupling a free-piston engine with linear generators, OFPEGs enable the direct conversion of combustion energy into electrical power. This architecture is particularly attractive for hybrid and range-extender applications, where operational flexibility and high system efficiency are critical to achieving significant reductions in fuel consumption and CO₂ emissions.
Despite these advantages, the performance of OFPEG systems is governed by a strong coupling between piston dynamics, in-cylinder combustion processes, and electrical loading conditions. This coupling presents substantial challenges for system design, control, and optimization, limiting the further development and application of OFPEGs.
In this study, a novel one-dimensional numerical model is developed for the OFPEG using the Gasdyn simulation code and validated against experimental measurements. The model captures the coupled dynamic and thermodynamic behavior of the OFPEG system, enabling a comprehensive analysis of OFPEG performance under various operating conditions.
Based on the validated model, a comprehensive parametric investigation is conducted to quantify the influence of key design and operating parameters, including combustion settings, electrical load conditions, and system configuration, on system performance. The results provide valuable insights into the design and optimization of OFPEG system. Furthermore, the proposed numerical model offers an effective tool for investigating piston trajectory optimization and advanced control strategies, supporting the development of low-carbon, high-efficiency OFPEG systems for future transportation applications.