Experimental research on a newly developed detonation flame arrester
In this research, a flame arrester consists of radial slit structure is developed. In order to determine the characteristic of the newly developed flame arrester, pressure response and detonation wave velocity are measured using two radial slit structures with different inside diameter. At first, the flow characteristics for the slit structures are investigated theoretically and experimentally. Then, the slit structures are applied to the flame arrester. Detonation experiments are performed for mixture gas of air and hydrogen. It reveals that the radial slit structure with the suitable inside diameter is effective for the flame arrester.
Relation between cell size, induction zone length and critical initiation energy in oxyhydrogen detonations.
Detonation cell size has been measured in a mixture of hydrogen with oxygen over wide ranges of equivalence ratio and subatmosheric initial pressure. The experiments have been carried out in a cylindrical tube of diameter 30 mm and the cell size has been determined by using the sooted plate technique. The data of the cell size at subatomospheric pressures have indicated that it is proportional to p0-1.2, where p0 is an initial pressure of the mixtures. Values at the atmospheric pressure have been obtained by extrapolating the obtained subatmosheric values of the cell size, and have been plotted against the equivalence ratio and compared with calculated induction zone length by Westbrook. The fact that the cell size is directly proportional to the induction zone length has been verified for the oxyhydrogen mixture over the range of the equivalence ratio tested. The proportionality factor for this mixture has been found to be 23.3, while that for hydrogen/air mixtures had been found by Knystautas et al. to be 52.2. The critical initiation energies etimated from the cell size data obtained here by utilizing the theoretical model proposed by Lee have been found to be in good agreement with measured critical initiation energies by the critical tube diameter method of Matsui and Lee.
A high-speed photographic study of the transition from deflagration to detonation wave
Experiments were conducted to investigate the DDT process of the oxyhydrogen gas in the rectangular detonation tube of 3 m long. The repeated obstacle was installed near the ignition plug and the effects of the obstacle on the DDT process were investigated. The behaviour of the combustion and detonation wave were visualized utilizing Imacon high-speed camera with the aid of Schlieren optics.As a result, DDT process was visualized, i.e. (i) multiple shock waves were induced by the expanding combustion wave, because the combustion flame played a role as a piston and compressed the unburned gases. (ii) The acceleration of the combustion wave was occurred and the distance between the shock wave and the combustion flame became shorter. (iii) Eventually, the local explosion was occurred and cause overdriven detonation wave to propagate at the velocity of about 3 kms−1.