Experimental Assessment of a Free Elastic-Piston Engine Compressor with Separated Combustion Chamber

This paper presents the experimental assessment of a free elastic-piston compressor (FEPC) equipped with a separated combustion chamber. The FEPC is a proposed device that utilizes combustion of a hydrocarbon fuel to compress air into a high-pressure supply tank, thus potentially serving as a portable power supply candidate for untethered pneumatic systems of human-scale power output. The design and simulation of the FEPC concept have been shown in previous work, and the device's energetic merit outlined. The free "piston" consists of a custom-molded silicone-rubber membrane, clamped at the circumference, thus providing perfect blow-by sealing and near zero friction. The device is equipped with a custom-built separated combustion chamber, which dynamically channels high-pressure combustion products of a hydrocarbon fuel in order to produce power strokes. Experimental results coupled with high-speed video are presented which verify 1) the operation of the separated combustion chamber including its air/fuel mixture control, 2) the dynamics of the combustion valve in first sealing the pre-combustion gases and then venting the combustion products into an expansion chamber, 3) the dynamics of the free piston in converting pressure energy in the expansion chamber into kinetic energy, and 4) successful pumping of air into a reservoir.