Study on Deflagration to Detonation Transiton Process of Gas/Solid/Liquid Multiphase Fuel Mixtures
Author:Li Shu Zhuan
Supervisor:liu qing ming
JP-10 is a high energy density of simple fuel,in the volume limited combustion equipment or aerospace power plant has a good application prospects;aluminum powder is an important industrial raw materials,the main fuel components of fuel air explosives and additive of mixed explosives.The fuel/air mixture is closely related to industrial safety and fuel air explosives weapons.Process of deflagration to detonation transitions(DDTs)and the structure of the detonation wave in high-density hydrocarbon fuel JP-10 and aluminum powder,n-pentane,nitroethane air mixture were studied in the Horizontal Multiphase Combustion and Explosion System(HMCES)in the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology).The influence of aluminum powder concentration and morphology on the DDT process of aluminum powder/air mixture was studied.It was found that DDT was achieved when the concentration of flaky aluminum powder/air mixture between 286 g/m~3-532 g/m~3,and the optimum concentration was 409g/m~3,the detonation velocity and detonation pressure are 1690m/s and 58bar respectively.The characteristic scale of aluminum powder(thickness of flaky aluminum,diameter of spherical aluminum)is an important parameter affecting the process of DDT in aluminum powder/air mixture.As the characteristic scale of aluminum powder increases the DDT process slows down and the detonation parameter decreases.At the concentration of 409 g/m~3,nanometer-aluminum,flaky aluminum,micrometer aluminum,10 micron aluminum powder/air mixture can achieve DDT,the detonation parameters of nanometer aluminum powder is maximum,the detonation velocity and detonation pressure were 1708m/s and 61bar respectively.While 15 micron aluminum powder and 20 micron aluminum powder/air mixture did not achieve DDT.And the DDT mechanism of aluminum powder/air mixture was analyzed.Through the study of DDT process of JP-10 mist/air mixture,it is found that the coupling process of the leading shock wave and the deflagration wave can be achieved and self-sustained at 510 m/s-560 m/s at a concentration of 142.86 g/m~3-222.57 g/m~3.This low-velocity self-sustained detonation can be explained by the low-volatile of JP-10 liquid and boundary conditions.Under the experimental conditions,the optimal detonation concentration of JP-10 mist/air mixture is 164.54 g/m~3,and the detonation velocity is 560m/s.The minimum critical detonation concentration is between 123.04 g/m~3 and 142.86g/m~3,and the maximum critical detonation concentration is between 222.57 g/m~3 and253.83 g/m~3.The DDT process of gas/solid/liquid multiphase fuel/air mixture with aluminum powder as the granule component,JP-10 as the main liquid component,n-pentane and nitroethane as liquid additive was studied.The effects of the addition of n-pentane and nitroethane on the DDT process were discussed.N-pentane plays a leading role in the DDT process of JP-10 mist/n-pentane/aluminum powder/air mixture,and the detonation parameter(pressure,velocity,etc.)increases with the increase of n-pentane content.Under the experimental conditions here,JP-10 mist/nitroethane/aluminum powder/air mixture did not achieve DDT.It is found that both the aluminum powder/air mixture,the JP-10 mist/air mixture,the JP-10 mist/n-pentane/aluminum powder/air mixture can achieve DDT,the DDT process undergoes a slow reaction compression stage,the pressure wave accelerates the shock wave formation stage,the impact reaction transition stage,the impact reaction to the overpressure detonation transition stage and the detonation stage,and obtain the DDT process parameters at each stage.The detonation wave structure of the multiphase fuel/air mixture was studied.The helical detonation angle and cell size of the double-headed mode were observed in the process of detonation of aluminum powder/air mixture.The structure of the detonation wave,the flow field parameters and the excitation parameters were analyzed.The interaction between the wave and the three-wave point trajectory;the low velocity spiral detonation of the single-head mode is observed during the detonation of the JP-10 mist/air mixture,and the transverse wave head rotates clockwise on the circumferential surface of the pipe wall,Cell size of 36.65°and 0.84 m respectively.In the JP-10 aluminum powder/air mixture,a single-head mode of spiral detonation was observed.The transverse wave head was rotated counterclockwise on the circumferential surface of the pipe wall,the grid dimensions are 42.93°and 0.56 m,respectively.