Study On Microscale Combustion Of Energetic Materials And Propulsion Principle

In order to development high performance solid chemical micro-thruster, characteristics and mechanisms of solid energetic materials combustion in microscale as well as work characteristics and structure design of micro-thruster were investigated by this dissertation.Change of Burning rate of B/KNO3 varied with tube diameters, combustor pressures, wall thicknesses and wall thermal conductivities in microscale quartz tubes were obtained by the high-speed photography. Based on the mechanisms of combustion and thermal conduction, a model describing the process of combustion and thermal conduction of solid energetic materials burnt in a microtube was established. With the help of this model, effects and mechanisms of micro-tube dimensions, wall thicknesses and wall thermal conductivities on thermal loss and combustion stability were obtained by numerical simulation. Results show the stability was decreased with decreasing tube diameters, combustor pressures, and increased with decreasing wall thermal conductivities. When wall thermal conductivity was smaller, buring rate was increased with increasing wall thicknesses. In contrary, buring rate was decreased with increasing wall thickness. However, when the wall thickness reach a certain value, effects of wall thicknesses on combustion tended to stability.Change laws of work performance of different propellants varied with different chamber diameters were tested and analyzed by Simple Pendulum Principle. Results show thrust and impulse were increased with increasing chamber diameters in the same propellant. Lead styphnate species had large thrust and impulse, and nickel hydrazine nitrate species had small thrust and impulse in the same chamber diameters.A model describing thrust of micro-thruster was established, and effects of micro-nozzle structures on performance of micro-thruster were obtained by calculation. Results show micro-nozzle had a optimal exit expansion ratio under 0.1 MPa pressure. Thrust was increased with increasing exit expansion ratio of micro-nozzle in vacuo.A one-dimensional finite difference model describing the process of combustion and thermal conduction, as well as finite element model of micro-thruster array were established respectively. With the help of these methods, structures and mechanical Properties of micro-thruster cell were analyzed by numerical calculation and simulation. Results show larger heat conductivity, longer combustion time led to less micro-thruster cells on a same area.The maximum value of equivalent thermal stress and thermal deformation were located on edge of chamber hole, which were the brittle parts on micro-thruster chamber. Due to the thermal stress and thermal deformation, the structure of array are more easily damaged with the increasing combustion gas temperature, action time and chamber diameters, and decreasing cell spacing.