Near‐limit behavior of high‐Lewis number premixed flames in tubes at normal and low gravity

摘要: The high‐Lewis number (Le) diffusive‐thermal instability in premixed gas combustion is studied experimentally tubes using lean C4H10–O2–He mixtures (Le≊3.0). Two self‐excited instabilities are observed for flames propagating a tube open at the ignition end and closed other end: (1) combined spiral wave radial pulsation (2) pure pulsation. These modes both earth gravity (1 g) microgravity (μg) therefore believed to be direct manifestation of rather than buoyancy‐induced instability. Moreover, frequencies lower fundamental acoustic which renders unlikely possibility that they acoustically‐induced instabilities. A critical fuel concentration onset pulsation, as well found. transition between waves pulsations also observed. observatio...