Heat transfer model development for the free double piston engine concept

The Free Double Piston Composite Cycle Engine (FDP-CCE) integrates turbofan engine architecture with piston engine characteristics, aiming to optimize the engine efficiency and reduce the CO2 emissions. Its free-piston structure is significantly lighter and smaller than traditional crankshaft-connected piston engines, eliminating the need for mechanical transmissions and lubrication systems. Innovations like air lubrication, increased piston velocities, and a self-powered gas generator contribute to higher cylinder temperatures. This study details the FDP’s concept design, its operational parameters and a novel filling-discharge model for a two-stroke compression ignition engine, analyzing piston dynamics and airflow. It also delineates the engine's operational cycle into phases to the functions of engine and compressor pistons. Specifically, the compressor piston includes the expansion, intake and compression phases, while the engine piston encompasses fuel injection, combustion, expansion, exhaust, an overlap phase characterized by the simultaneous operation of both exhaust and inlet valves, and the compression phase. The comprehensive heat transfer models developed are crucial for assessing thermal dynamics in various engine components and predicting performance under different conditions. Encompassing mass flow, combustion energy release, and heat transfer mechanisms (conduction, convection, radiation), this study lays a foundational framework for future aeroengine designs, promoting sustainable propulsion solutions with reduced fuel consumption and emissions.