A detonation-driven shock tube firstly designed by H.-R. Yu, is considered as a useful facilities capable of producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating oxygen-hydrogen (oxyhydrogen) mixture and has characteristics that temperature as well as pressure of driver gas is extremely high compared with conventional shock tubes. However, a structure of detonation wave is not uniform e.g., detonation wave has three-dimensional cellular structures and multiple transverse waves. Furthermore, the detonation wave is followed by a Taylor expansion fan and performance of detonation-driven shock tube is not well understood. In this preliminary study, a detonation-driven shock tube is constructed and its performance is experimentally investigated by measuring pressure histories and a profile of ionization current behind detonation wave. As a result, (i) the pressure histories of detonation wave is clarified and it shows reasonable agreement with a result obtained by KASIMIR shock tube simulation code. (ii) A propagation velocity of detonation wave is coincided well with theoretical predictions assuming Chapman-Jouguet detonation wave. (iii) An equivalence ratio of oxyhydrogen mixture to produce a highest Mach number of the shock wave is evaluated as 〓≃1.7.
It is important to investigate a pressure profile when a diffracted shock wave interacts with a reflector from a safety point of view. Because the diffracted shock waves are often generated by the explosions of combustible gases to cause serious damages against human race and surrounding buildings. The maximum pressure behind reflected shock wave is one of the most important parameter and this report is concerned with the evaluation of maximum pressure, which might be a function of Mach number of the shock wave, distance from a source of the shock wave, initial pressure of the gas, and initial diameter of the shock wave, etc. In this study, a detonation-driven shock tube of 14 m long and 50 mm diameter is used to generate a strong shock wave of propagating Mach number MS=3.0∼5.2. The shock wave is diffracted from an open end of the shock tube of 25 mm diameter and reflected from a cylindrical reflector of 50 mm diameter. These phenomena are observed using color-schlieren optical techniques and the pressure histories at the stagnation point of the reflector are simultaneously measured. As a result, (i) The behaviors of the diffracted shock wave and complicate flow-fields behind reflected shock wave are observed. (ii) An empirical equation to calculate the maximum pressure behind reflected shock wave is estimated by the results of experimental and numerical simulation.
