Design and experimental study of a 300 We class combustion-driven high frequency free-piston Stirling electric generator

Portable electric power generator with a power level of several hundred Watts plays an important role in outdoor activities, emergency relief and tactical power supply. As an external-combustion heat engine with outstanding heat source adaptability, free-piston Stirling generator (FPSG) owns attractive advantages of quietness, high thermal efficiency, and high reliability. This paper proposes a novel ultra-high frequency (UHF) FPSG-based portable power supply system driven by a diesel porous media evaporative combustor (PMEC). An experimental setup was designed and built based on the quasi-one-dimension thermoacoustic impedance matching of the FPSG and three-dimension thermal coupling of steady combustion and alternating flow between FPSG and combustor. The fundamental operating characteristics of the system were investigated in terms of combustion powers and electric loads. Preliminary experimental results show that a maximum output electric power of 350 We at a heating temperature of 875 K and a maximum fuel-to-electric efficiency of 11.98 % were obtained. Computational fluid dynamics (CFD) simulations were employed to delve into the intricate combustion and heat transfer processes, unveiling the formation of carbon deposits and confirming the efficacy of cyclone holes in reducing carbon deposition. This pioneering exploration of 130 Hz UHF and evaporative-combustion coupled heat transfer successfully showcases the feasibility of constructing a high-specific-power FPSG-based portable power system. •An innovative portable power generation system was proposed utilizing a free-piston Stirling generator.•Free-piston Stirling generator with an ultra-high operating frequency exceeding 130 Hz was built to demonstrate a high power density of 70 W/kg.•The integrated design of the high-temperature heat exchanger in the free-piston Stirling electric generator ensures reliability under elevated temperatures and pressures.•The novel design featuring inclined swirl air jet orifices and a gradually shrinking spout effectively eliminates severe carbon deposits, enhancing combustion and heat transfer efficiency.