Investigation Into The Deflagration/Detonation Characteristics Of RDX-ethylene-air Hybrid

The experimental study was conducted in order to determine the deflagration/detonation characteristics of RDX particle dispersed into flammable gas and the effect of diffusion time for deflagration and detonation parameters of ethylene-air, which provided raw data to investigate the mechanics about the development and propagation of detonation wave, cellular structure and the guideline of prevention, control, extinguish of industrial accident in the defense industry,civil explosive and petroleum industry, and foundation research for the military application in certain region. The deflagration and detonation parameters of ethylene-air mixtures were measured at different diffusion time in a shock tube, detonation pressure and velocity,cell size,critical initiation energy of RDX-ethylene-air hybrid mixture in different ethylene and RDX concentration have also been measured. The main conclusions are as follows:1. The trend of deflagration and detonation parameters of ethylene-air mixture(three concentrations) are plain when the diffusion time increases,4.00 vol.% ethylene-air can’t meet detonation criteria under the experiment condition; Comparing the experimental value of detonation pressure and velocity of ethylene-air (four concentrations) with the CJ theory value calculated by NASA CEA, it is found that the experimental pressure and velocity respectively reach to 90%,92% of theoretical value.2. The RDX-air mixture(cRDX=284 g/m3、474 g/m3) can’t meet detonation criteria under two given ignition energy. For the RDX-4.00vol.% ethylene-air hybrid mixture, under the ignition energy 0.75 MJ/m2, the pressure and velocity have an obvious decrease from no dust to 189 g/m3, the hybrid mixtures achieve detonation due to the synergistic effects of RDX and ethylene when the RDX concentration up to 284 g/m3,474 g/m3, but a mutation is occurred that mixture didn’t achieve detonation when CRDX=379 g/m3. Substitue ignition energy 1.31 MJ/m2 for 0.75 MJ/m2, the hybrid mixtures achieve detonation for the RDX concentration among 189 g/m3 to 474 g/m3.3. Under the ignition energy 0.75 MJ/m2, the pressure of RDX-ethylene-air hybrid mixtures which ethylene concentration ((p=0.914,1.023) is nearly stoichiometric has a noticeable increase when from no dust up to cRDX=474 g/m3, but the velocity only has a slight rise. For the RDX-ethylene-air hybrid mixtures which ethylene concentration ((φ=1.123,1.397) is fuel enriched, the pressure of RDX-8.89vol.% ethylene-air hybrid mixtures is smaller than that of RDX-7.27vol.% ethylene-air under several dust concentrations, the situation reverses when cRDX≥379 g/m3.4. Based on the method of Smoked foil, the cellular structures of RDX-ethylene-air at different RDX concentration with the ethylene concentration (6.00vol.%,6.67vol.%, 7.27vol.%,8.89vol.%) which is far from the explosion limits are seized, which are not very regular. The cell size of ethylene-air which is measured under 0.25 MPa is smaller than that in the literature that is measured under 0.1 MPa, the cell size and ratio of l/λ are 8 mm-16 mm, 1.5 resepectively. For the RDX-ethylene-air hybrid mixtures, the measured cell size possesses a "U" shaped curve with the RDX concentration, which reaches its minimal value when c=189 g/m3or 284 g/m3, the cell size and l/λ of hybrid mixtures are 5 mm～12 mm,1.2 resepectively.5. The critical initiation energy of RDX-4.00 vol.% ethylene-air is not a standard "U" shaped curve with the RDX concentration. According to the surface energy model which is proposed by Lee, the calculation value of critical initiation energy of 6.00 vol.% ethylene-air, RDX-4.00 vol.% ethylene-air (cRDx=284 g/m3) have a well agreement with the experimental value. A possible mechanism of synergistic effects between RDX particles and ethylene has been proposed in this thesis to illustrate the experimental behavior, which could provide an opinion of the multiphase detonation.