Dynamics of a small-scale single free piston engine generator

A single free piston engine generator with 10 mm bore and 10 W power output aimed for use as a small-scale power supply is presented. In order to validate the principle, a numerical simulation program for dynamics and performance prediction is established and solved by a series of dynamic, thermodynamic and electromagnetic equations. The results indicate that the principle is feasible with advantageous characteristics compared with the conventional crankshaft engine and the dual free piston engine generator, including asymmetric operation with faster expansion than compression. The motion of piston keeps in stable cycle with a closed loop of velocity versus displacement. The predicted combustion is close to the ideal constant volume process. If the vibration and piston lubrication problems associated with high accelerations can be resolved, the single free piston engine generator provides a compact and simple internal combustion engine generator with high efficiency.