Study on the ion current formating process under engine knocking conditions

In the last decades, ion current sensing has been widely recognized as a promising approach to engine knock/super knock detection. However, formating mechanism under knocking conditions is yet be revealed, which substantially hinder further development of based detecting technology. this paper, signals detected are investigated both experimentally and numerically. spark ignition engine, signal combustion pressure analyzed in time frequency domain. Besides, multi-physics CFD model, incorporates compressible fluid dynamics, neutral/charged species reaction kinetics flame plasma hydrodynamics, constructed work. Then process, - wave interaction motion charged analyzed, key features studied. The model indicates that in-cylinder distribution positive negative almost same due ambipolar diffusion electrons, then can via observing flux solely. By combining experimental numerical results, it revealed concentration correlative temperature non-linear way, mainly responds low oscillation mode. Correspondingly, relation between oscillating amplitude intensity non-linear. For at high load conditions, respond local intensity. particular, becomes insignificant when KI < 0.85.