Detection of flame propagation pattern in a spark ignition engine using gasket ion sensor

In order to reduce the exhaust emission and the fuel consumption in a spark ignition engine, the combustion diagnostics had been developed. However, there are few sensors which can detect the combustion quality for the individual cycle and cylinder in production engines. In previous study, the new technique using a gasket ion sensor for measuring the combustion quality has been proposed. In present study, the flame propagation pattern in a spark ignition engine was detected by using a gasket ion sensor with a circular electrode. The waveforms of ion current obtained from a circular ion sensor were compared with the flame propagation pattern obtained from multiple ion sensors. When the mixture was ignited in offset center of the cylinder, the flame propagation pattern was distorted from the spherical pattern. Then the waveforms of ion current from the circular ion sensor were varied from the waveform for a center ignition. The peak location of ion current was coincident with the peak location of heat release rate. This is because the contact area between the flame and the ion sensor is largest when the surface area of flame is largest. The circular sensor is available to detect the variation of the flame propagation pattern and the peak location of heat release rate.