Effects of shape of ion probe on flame detecting characteristics in 2-stroke gasoline engine

Multiple-ion probe method is one of the beneficial method to obtain the detailed information about explosive combustion such as knocking. Our group has been trying to expand the measurement ability on multiple ion probe method from highly-controlled combustion in combustion test tube studied by previous studies to highly-unstable combustion such in spark ignition engines. The previous studies showed that multiple-ion probe method was able to capture the movement of propagating flame in 2-stroke gasoline engine in limited conditions. It requires that more reliable detection of propagating flame in the engine to capture the flame movement more stably.

In the present study, the effects of the shape of the ion probe on flame detection characteristics in 2-stroke gasoline engine was investigated. Tested parameters of the shape in the ion probe were projection length and diameter of an ion probe wire. Projection length was changed as 0, 0.5, 1.0, 1.5mm. Test results say that the projection length has positive effects for flame detection. Longer projection length has a higher sensitivity for flame detection. Diameter of ion probe wire was changed as 0.3, 0.5, 0.7, 1.0mm. Experimental results indicate that the size of diameter has less effect on the mean strength of detected flame signal than the projection length.