Experimental Results of Miniature Rotary Internal Combustion Engines

Internal combustion engines offer many advantages over batteries for applications in portable power generation. A liquid hydrocarbon-fueled engine could provide ten times the specific energy density of the best batteries available. A miniaturized engine was designed and developed to explore the issues of engine miniaturization and to prove the feasibility of small - scale engines. This study is part of a project to develop MEMS-based internal combustion capable of producing tens of milliwatts of power fabricated using techniques of the integrated circuit community. A rotary internal combustion engine was chosen due to its simple, planar design that lends itself well to the fabrication techniques of MEMS. A test bench for a minirotary engine has been developed and experiments have been conducted with gaseous-fueled mini-rotary engines to examine the effects of sealing, ignition, and design. Results shown here have confirmed that an engine of this size is feasible with a measured net power output of up to 3.7 W at 9300 RPM. These results were obtained using hydrogen-air mixtures with both spark and glow plugs used as ignition sources. Iterative design and testing of the mini-engine has lead to improved sealing designs and improved power output from the engine. This testing has proven that there are no fundamental phenomena that would prevent the operation of the microengine but technological issues still to be overcome. Heat loss and sealing will be important for the efficient operation of the micro-engine. Further research is needed to optimize the engine's performance and efficiency, integrate liquid fuel carburetor into the engine design, and develop a portable power generation system based on this engine. The mini-rotary engine design, testing, results and applications will be discussed.