Experimental Study on Propane/Air Flame Propagation Characteristics in a Disc-Like Gap Chamber

A disc-like gap chamber was developed to investigate the microscale effects on flame propagation characteristics in closed chamber, which is very important to understand the combustion process in micro internal combustion engines. Under initially normal pressure and temperature, the morphology and evolution of outwardly propagating flame, the flammable limit, flame speed and flame instability of propane-air flames influenced by gap width and equivalence ratio were experimentally studied. The results show that, as the gap width nearly equals to the quenching distance, the sustained propagation was possible only with rich flames. The smooth flames and wrinkled flames were observed. It clearly shows that the flame wrinkles developed gradually instead of instantaneously. The flame speed was slower in the 2.0 mm gap chamber than in a conventional combustion bomb, and the flame speed decreased with the increase of flame radius. As a result, the flame acceleration was not observed in present experiments. With the smaller gap width, the wrinkled flame occurred early, and the flame speed was slower. Due to the geometry of disc-like gap chamber, simple theoretical analysis indicates that the heat loss and elevated pressure play important roles in reducing flame speed.