A new technic to measure the propagating flame precisely by using densely installed multiple ion-probes has been developed. This system targets the high-intensity and pulsatile combustion, including knocking in gasoline engine, and oscillating combustion in burner or gas turbine combustor. In such environment, observation of details in the combustor by visualization is generally limited because of the strength of observation window. In contrast, ion-probe is physically and thermally strong enough to endure such environment.
In the present study, characteristics of the combustion measurement were investigated using the different types of propagating flame with various LPG-oxygen-nitrogen mixtures. The composition of the mixture was stoichiometric LPG-oxygen diluted with nitrogen. Nitrogen dilution ratio was varied to control the flame propagation velocity. Minimum and maximum propagation velocity tested in the series of experiment was a few meters per second and about 2300m/s respectively. This range covers most type of combustions utilized in the industrial field.
The result shows that this measurement technic has an ability to capture the fluctuation of propagating velocity in millimeter scale both in deflagration propagating at a few meters per second and in detonation propagating at supersonic speed with a few kilo meters per second. It is expected that this technic has sufficient performance to capture precisely the knocking in automotive engines and oscillating combustion in burners.