The Study Of Atomization Character Of Coaxial Injector In Rocket Engine

Tripropellant injector element is one of the most important components in tripropellant engine, which is studied with emphasis. The cold - flow test about tripropellant injector is conducted in present paper. The experiment focuses on three aspects: discharge characteristics, atomization characteristics and the effect of ambient pressure on spray cone angle of coaxial swirl injector.The injector experimental system is reconstructed and some injectors are designed and manufactured. The law how the parameters, such as the pressure before injecting, ambient pressure, the distance to exit, affect discharge characteristics and atomization characteristics of injectors is analyzed.Some conclusion can be drawn from the discharge characteristics experiment. First, the discharge coefficient of coaxial shear injector is almost keeping the number 0.76 when the pressure drop of liquid is high enough and that of coaxial swirl injector is almost keeping the number 0.23. Second, the discharge coefficient of ring gap, whose ratio of length and width is greater than 10, is in the area from 0.4 to 0.65 and less than that of a common orifice of a coaxial shear injector.Some conclusion can be drawn from the discharge characteristics experiment. There is a leap of SMD(Sauter Mean Diameter) at a certain axial position downstream of injector studied. And under a certain ambient pressure, the increasing of pressure drop of liquid and gas makes the atomization worse for a fixed position, but the principle is different. For the two modes of tripropellant injectors, SMD of high ambient pressure is greater than that of low ambient pressure with the same pressure drop. Just because the mass flowrate of kerosene is so little that the different of SMD of the two modes is little in different ambient pressure.Generally speaking, the spray cone angle of coaxial swirl injector increases with the increasing of pressure drop of liquid, but in the increasing process, the angle is fluctuant. And the angle decreases with the increasing of ambient pressure. What's more, the angle becomes less without the injecting gas against the case of the exists of injecting gas.