Experimental Research On Impact Of Flexible Perturbance On Detonation Propagation

Industrial production is suffering from gaseous explosion seriously. Once highly sensitive mixtures was ignited in confined space, equipments and properties will be destoryed by a leading detonation with highly possibility. Initial conditions and boundary conditions are regarded as unsubstitutable measurements to predict and appraise detonation probability. Present research shows that perturbance results in a significant impact on development, reaction and failure for detonation wave. However, how flexible materials, as multilayer polypropylene foil performing as head-on obstruction in tube, impacts on detonation propagation is still unkown. There is significant meaning to prevent detonation disasters and develop its application with deep reseach of relative disciplines.Therefore, polypropylene foil was set as head-on perturbance ?blocking rate is 1.0? in a detonation tube, experimental system of gaseous detonation was designed and built, charateristics of detonation propagation nearby perturbance were studied comprehensively. Main works and conclusions of this thesis are as follows:?1? In non-perturbanced tube, charateristics of detonation velocities and cellular structures of detonation propagation for C₂H₂+2.50₂+nAr mixtures were carried. Applicable conditions for the one-dimensional theory of detonation were evaluated. With different initial pressures ?Po=10?50 kPa? and argon-diluted concentrations ?n=0?80%?, detonation waves will propagate as stable model for C₂H₂+2.50₂+nAr mixtures, while velocities of detonation wave are sightly lower than velocities of CJ detonation theory. When argon-diluted concentration is higher, velocity of detonation wave will reduce, when initial pressure grows higher, velocity of detonation wave will rise sightly. The specific differences of stable mixtures and unstable mixtures were analysed, ZND structures of stable mixtures were observed. Errors between actual and theorical velocities of detonation wave are lower than 5 percent. For stable mixtures, simplified calculation is a mean of forecast on velocities of one-dimensional detonation.?2? Impact of head-on perturbance by polypropylene foil as material on detonation propagation and its discipline were analysised. There are two different models of detonation propagation after perturbance:when initial pressure is low or argon-diluted concentration is high ?Po< 40 kPa, n> 50%?, detonation front will decouple and fail; when initial pressure is high and argon-diluted concentration is low ?P0?40 kPa, n<50%?, detonation velocity reduces. Analyses shows that flexible materials were impacted by shock front in this way:when induction wave dominate the impacting process, flow expansion along reflected wave will lead to reduction of detonation after shock front destroy foil which cause velocity deficit.On the other hand when reflection wave dominate dominate the process, detonation fail.?3? Experimental investigation on acceleration and propagation after perturbance when velocity reduced and detonation failed was accomplished, discipline for detonation propagation at lower-speed detonation or failed detonation were analysed, regions that caused by perturbance of propagation in lower-speed or failed detonation were offered. There is no accurate transition for velocity deficit since triple structures disappeared with which dominated distance is about 37.5 mm to 50 mm. Shock front of detonation wave turns to expansion wave when detonation fails. Distance of deflagration grows when initial pressure reduces or argon-diluted concentration raises, but the distance is not sensitive to argon-diluted concentration. Dominated distance is longer than the length of deflagration-to-detonation transition, shorter than distance to stable-model propagation. After a transient overdrove detonation, reduced or failed detonation will finally propagate as a stable model.According to the experimental results, propagation of stable detonation across perturbance was divided into three sections, a. self-sustaining detonation, b. low-speed or failed propagation, c. overdriven detonation.