A free-piston linear generator (FPLG) has a number of advantages compared to a tradi-tional crank-slider internal combustion engine, including better thermal and mechanical eficiencies,different fuel compatibility, and a higher power-to-weight ratio. For electric vehicle propulsion andgeneration of portable power, an FPLG is a very attractive alternative source of energy. This paperpresents the development of an FPLG simulation model using MATLAB-Simulink and investigatesthe impact of combustion variance on its operation. Results provided insight into various characteris-tics of system behavior through variation of structural dimension and operational parameters. Insteady-state operation with fixed electrical load and fixed ignition for combustion, it was found that consecutively low combustion pressures can easily lead to engine stoppage, pointing to the signifi-cance of control for continuous operation. Due to the absence of the moment of inertia and fiywheelcharacter of the rotating engine, a linear engine-generator is subject to ceased operation even after two consecutively low combustions under 10% variance. This will not be a fundamental problem in an ordinary crank-slider engine-generator, but in a linear engine-generator, control measure will benecessary to ensure sustained operation.

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This paper presents the modeling and optimization of the complete electromechanicalsystem of the FPLG on MATLAB/Simulink. Initially the model was tested for full-cycleoperation with and without load by varying structural parameters and combustion factor(CF). We noted that there was some unrealistic behavior in the piston trajectory toward the CC. After improving the model and introducing some natural combustion variations, we noted that the system was behaving naturally. The P-d diagram resembled the experimental results.The combustion model is made up of a fixed pressure vs. displacement profile,which was originally experimentally obtained. It was improved to achieve the pressure-displacement profile for free-piston combustion. However, the shape will always be the same and the model is basically a fixed pressure profile. The program was modeled forcombustion to occur on the left side while the bounce chamber was on the right side.

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The FPLG Simulink model was improved to eliminate unrealistic system behaviorsby implementing a minimum displacement of-30 mm for combustion and preventing compression pressure from increasing beyond the combustion profile or jumping to the combustion profile during the return stroke from left of right. The natural phenomenon of combustion variance was introduced with a combustion factor CF of 0.94 and coefficient of variation (COV) of 10% implemented in the program. This produced cyclic variation incombustion pressures, resulting in system stoppage due to consecutively low combustionenergy in the last few cycles. After final improvement of the FPLG simulation model to correct any deficiency, final simulation graphs of CC pressure vs. displacement, displacement vs. velocity and emf vs.displacement were obtained, compared and validated with experimental results. It was noted that the simulated FPLG system exhibited comparable behavior to the experimental profiles. Finally, three graphs of CF and CC pressure vs. time, CF and CC displacement vs.time and CC pressure and BC displacement vs. time were obtained for three different CFvalues of 0.87, 0.89 and 0.91, all subject to a COV of 10%. Results showed that in the earlier cycles, due to healthy combustion and a sufficiently high CF, operation was stable and the CC endpoint displacement could achieve the minimum value for combustion.

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1.Technical Innovation: The focus on improving the simulation model and addressing unrealistic system behaviors demonstrates a commitment to technical excellence. If this innovation results in a more efficient or reliable Free-Piston Linear Generator, it could have market potential, especially in industries relying on linear engine-generators.

2.Energy Efficiency: The need for higher combustion energies with electrical loads, suggesting a potential application in power generation. If the FPLG can offer improved energy efficiency or unique advantages over existing technologies, it may attract interest from industries looking for sustainable and efficient power solutions.

3.Control Measures: The mention of implementing control measures, such as load current control, indicates an awareness of the practical challenges associated with the technology. Developing effective control measures could enhance the reliability of the system, making it more appealing for commercial applications.

4.Validation with Experimental Results: The validation of simulation results with experimental data adds credibility to the study. If the FPLG can demonstrate consistency between simulated and real-world performance, it may instill confidence in potential investors or customers.

5.Applications in Various Industries: Depending on the scalability and adaptability of the technology, the FPLG could find applications in different industries, such as power generation, automotive, or any field requiring linear engine-generators.

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