Research and Development of Microwave Plasma Combustion Engine (Part II: Engine Performance of Plasma Combustion Engine)

The objective of this study was to develop an innovative microwave-induced plasma ignition system to improve the fuel economy of a current engine and achieve a higher efficiency without any configuration modifications. A new plasma generation technique was proposed for a stable and intense ignition source. A microwave plasma combustion system was developed consisting of a spark plug, microwave transfer system, and control system. A magnetron, like that found in a microwave oven, was used as a microwave oscillator. The spark plug had a microwave antenna inside that generated plasma in the engine cylinders. The microwave transfer system transmitted microwave power from the oscillator to the antenna. Combustion experiments were performed using a single-cylinder research engine. The microwave plasma expanded the range of lean operating conditions. The single-cylinder engine had an indicated mean effective pressure (IMEP) of 275 kPa at an engine speed of 2000 rpm. The threshold of the lean limit was defined as a coefficient of variation (COV) of 5% at the IMEP. For the plasma ignition case, the combustion was stable even in the lean condition, and the COV remained under 2% up to an air-to-fuel ratio (A/F) of 22%. The lean limit improved from 19.3 to 24.1 with the plasma ignition.