Combustion stability control of a single-piston free piston engine generator

Abstract

Free piston engine generator is an effective alternative to conventional range ex-tender, which is able to facilitate the transportation sector decarbonization attributed to its high thermal efficiency and ultimate fuel flexibility. However, due to the lack of crankshaft mechanism, stable and robust operation of free piston engine generator is difficult to achieve since various disturbances may exist during its operation. In this paper, a combustion stability control based on active disturbance rejection control algorithm was proposed for a single piston free piston engine generator. To develop this control, a thermodynamic model of the free piston engine generator system was calibrated and validated through experimental data. Afterward, a 2nd order active disturbance rejection control based speed control was developed by leveraging the developed free piston engine generator model. The proposed active disturbance rejection control was employed into multiple abnormal combustion scenarios through a simulation, including various fuel heat released, ignition positions and burn durations, aimed to verify the control ability of rejecting disturbances and enhancing the robustness of the free piston engine generator operation.