Investigations on multi-circle spray detonations

Experimental investigations are carried out on a 50 I. D. multi-cycle pulse detonation engine model, and liquid fuel (gasoline) is used. The average of pressure peak, as measured by piezoelectricity pressure transducer, increases versus distance to thrust wall before fully developed detonation comes into being. According to the pressure history, the pressure in detonation tube will rise abruptly, when the flame front advances a certain distance downstream the spark. Two compression waves spreading to opposite directions are formed. One is enforced by combustion and becomes detonation rapidly, and the other is weakened because of obstacles and insufficiency of fuel. Two methods are used to determine the induction length of two-phase detonation wave through the pressure history. Ignition delay time is found to be much longer than DDT (deflagration to detonation transition) time, and the sum of the two changes little as cycle frequency increases. Together, they are the most important factors to control two-phase PDE operating frequency. Filling process and blowdown process are also analyzed.