Indirect Time-Resolved Visualization of Propagating Flame on Methane-Oxygen Mixture by Densely Installed Multiple Ion-Probes 2017-32-0047

Multiple ion-probes method has an advantage for detailed measurement on high-intensity combustion including engine combustion, oscillation combustion in gas turbine or burner. Multiple ion-probes are installed individually on the surface of the confinement wall in combustion chamber. Detailed behavior of the flame propagation along the chamber wall can be reproduced by the datasets of the flame arrival time detected by individual ion-probes. Main target of this study is to clarify the measurement performance of this multiple ion-probes method for various type of propagating flames generated in confined combustion tube. The characteristics of the flame is largely varied by changing the ratio of dilution with nitrogen on methane-oxygen stoichiometric mixture. No dilution, which means methane-oxygen stoichiometric mixture only, results fastest speed and relatively stable propagation. On the other hand, heavier dilution, which is diluted by larger amount of nitrogen, results lower speed and tabulated propagation.

Heavily diluted condition results the propagating flame with lower propagating speed and heavily bent flame front. In addition, propagation velocity was considerably different at each location and each moment. On the other hand, no diluted condition results stable detonation and planner flame front accurately perpendicular to the combustion tube axis was captured. Although measured propagation velocity in 200mm average corresponds to theoretical detonation velocity within 0.5%, fluctuation of 2.4% on velocity was observed in special span of 10mm. This fluctuation seems to be caused by macro-explosion in cell-structure of detonation front. Therese results indicate that developed measuring method has an ability to capture precisely both slowest propagating flame and fastest knocking line flame in actual reciprocating gasoline engine.