Abstract
Ignition properties of laser-induced breakdown sparks and electrical spark ignition were examined experimentally to choose an ignition method to investigate ignition limit of volatile components from heated materials in a microgravity experiment. Firstly, the characteristics of each ignition method were investigated for methane/air mixtures. In the case of electrical spark ignition, the minimum ignition energy depended on the electrode gap. On the other hand, in the case of laser-induced breakdown sparks, the minimum ignition energy did not depend on the focal length. Effects of gravity were clearly observed for lean mixtures in schlieren images of flame kernel development. Components of PMMA pyrolysis gas were examined using a gas chromatograph. Ignition behaviors of MMA/air mixtures, which are supposed to be produced from PMMA, were investigated. The minimum ignition energy for mixtures with various equivalence ratios was measured to identify the ignition limits of the gas. A change in ignition energy with an increase in the equivalence ratio was observed. Fundamental data for ignition tests in microgravity were obtained.
