Experimental study on the power generation characteristics of a free piston engine generator prototype with dual linear generator modules

The dual-piston dual-cylinder free piston engine generator (DD-FPEG) has garnered significant attention for its high thermal efficiency, power density, and suitability for various fuels. To improve performance and stability, this paper proposes a DD-FPEG prototype integrating dual linear generator (LG) modules. The structure and working process of the prototype is introduced, followed by testing its operating characteristics and power generation performance from the cold start to power generation process. When LG1 operates in motor mode, and LG2 operates in generation mode with no load, the motor thrust must exceed 126 N to ensure piston movement. As the motor thrust decreases from 221 N to 0 N and then switches to generation mode, the peak cylinder pressure, operating frequency, output voltage and power show a decreasing trend. The coefficients of variation for peak cylinder pressure position, top and bottom dead center positions are lower than that of peak cylinder pressure, and their values are below 3 %. When the load is 50 Ω, the prototype operates at about 31.2 Hz, with an average indicated power of 1422.8 W and a peak output power of about 1002.5 W. These results demonstrate that the proposed control strategy enables the designed prototype to achieve stable operation and smooth switching.