Experimental Study On Multiphase Detonation Characteristics Of Paraxylene (PX)Flammable Gas-Air Mixture

The fuel-gas multiphase cloud detonation is one of the most important parts in the detonation filed. The study of this multiphase detonation focuses on the initiation, propagation, attenuation and the structure of the detonation. It tends to see the fuel-gas multiphase detonation as an extension of the gaseous detonation. This thesis studies the detonation characteristics of the fuel-gas mixture which is composed of PX-flammable gas-Air with the help of vertical detonation tube and experiment system. The main work and conclusions are as follows:(1) The lowest concentration of flammable gas for direct detonation were measured in vertical detonation tube with three fuel-gas mixture (PX-C2H4-Air、PX-H2-Air、PX-C3H8-Air). The result indicated that the relationship of the lowest concentration of flammable gas and equivalence ratio shows "U" shape curve, and the corresponding equivalence ratio of the minimum of the lowest concentration is nearly equal to one. Under the fixed initiation energy, the order of the lowest concentration is C2H4<H2<C3H8.(2) The detonation parameters of three fuel-gas mixture (PX-C2H4-Air、PX-H2-Air、 PX-C3H8-Air) and the deflagration parameters of PX-CO-Air multiphase system were measured in vertical detonation tube. The result shows that the detonation pressure firstly increase and then descend along with the equivalence ratios, and the biggest value in the equivalence ratio to one. Comparing the measuring detonation velocities with the theory of CJ detonation velocities, the result indicates that the measuring detonation velocities tend to the theory of CJ detonation velocities along with the equivalence ratio. It shows that the unstable detonation transform into stable detonation along with the equivalence ratio. Under the maximum design initiation energy, the PX-CO-Air multiphase system failed to achieve detonation directly. It indicates that PX-CO-Air multiphase system had the least sensitive to detonation directly of the four fuel-gas mixtures.(3) The cell size of fuel-gas mixture (PX-C2H4-Air、PX-H2-Air、PX-C3H8-Air) were experimentally measured in different conditions using smoke foil technique. The cell size of gaseous detonation is smaller than that of the fuel-gas mixture. It shows that the theory of gaseous detonation is different with that of the fuel-gas mixture. Gaseous detonation is much more sensitive than gas-liquid two phase detonation.The cell size of C2H4-Air gaseous mixture and PX-C2H4-Air mixture detonation was also experimentally measured in different equivalence ratios. The result shows that the cell size of two detonations gives "U" shape curve which change with equivalence ratios, and the corresponding equivalence ratio of the minimum of cell size is nearly equal to one. The cell size of PX-C2H4-Air mixture is not uniform and irregular. It illustrates that PX-C2H4-Air multiphase detonation is unstable detonation.