Design, Modeling and Experimental Characterization of a Free Liquid-Piston Engine Compressor with Separated Combustion Chamber

Abstract

This dissertation presents the design, modeling, simulation, fabrication, and experimental characterization and model validation of a free liquid-piston engine compressor (FLPC). The FLPC 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 (100 Watts). The combined factors of high energy density of hydrocarbon fuels, high energy conversion efficiency (relative to comparable small-scale internal combustion engines and air compressors), compactness and low weight of the device, and its intended ability to drive power-dense pneumatic actuators (relative to DC motors), are projected to provide at least a twofold increase in systems-level energy and power densities over state-of-the art electromechanical human-scale untethered robotic systems. The free liquid-piston is powered by a custom-built separated combustion chamber, which dynamically channels high-pressure combustion products through a high-flow passive valve in order to produce power strokes. A dynamic model and simulation are presented, and experimental results are provided which validate the model and demonstrate the energetic potential of the device. Finally, the experimentally validated model is used as a diagnostic tool as well as a basis for future design suggestions.