The free piston linear expander (FPLE) is an energy conversion device that converts mechanical energy into electric energy by using a linear electric machine (LEM) without emission. This research addresses the numerical modeling of a dual-piston air-driven FPLE constructed on the basis of the free piston engine linear generator (FPELG) concept. The model was built in MATLAB/Simulink. The simulation results were in good agreement with the experimental data. Where the in-cylinder pressure and displacement profiles attained errors of less than 10 (within the acceptable range). Then, the predicted results of the simulation model, namely, the displacement profile, in-cylinder pressure, piston velocity, and engine power results were analyzed. Findings indicate that intake pressure was the most important parameter for enhancing engine performance. The in-cylinder pressure increased by approximately 16 and 21.7 when the intake pressure was increased from 5 to 6 bar and from 6 to 7 bar, respectively. The piston velocity increased by approximately 12.3 when the intake pressure increased by 1 bar. Finally, engine power increased by approximately 26.5 and 30.6 when the intake pressure increased from 5 to 6 bar and from 6 to 7 bar, respectively. © 2022 Novel Carbon Resource Sciences. All rights reserved.