Experimental Study On The Ignition And Combustion Of ADN-based Liquid Propellant Under The Action Of Microwave

Due to the development of space technology and the need for environmental protection,the concept of green propellant with high performance,low toxicity,low pollution and low cost has been proposed and paid attention to by various countries.Ammonium dinitramide(ADN)is a green propellant with good application prospects.At present,the ignition and combustion of this propellant mainly adopts the catalytic method,due to the existence of catalytic particle sintering,affected by preheating and other problems,it is difficult to expand on medium and large thrust occasions,so the development of new ignition technology for the development of the next generation of ADN-based liquid propulsion technology is of great significance.Microwave plasma ignition has the advantages of no catalyst,reliable ignition,high ignition energy and no preheating,which has good prospects for aerospace applications and has received wide attention.In this paper,the idea of using microwave plasma ignition technology for the ignition and combustion of ADN-based liquid propellants is proposed and investigated.Based on the microwave plasma ignition technology,a microwave ignition test platform was built and the effects of microwave power,gas flow rate and ADN-based liquid propellant flow rate on microwave plasma ignition and ADN-based liquid propellant combustion were investigated using an experimental method.Firstly,based on the microwave plasma generation principle,a resonant cavity for microwave plasma ignition test is designed and its internal electric field strength is simulated and analyzed based on COMSOL simulation software.The optimization of the electric field distribution in the cavity by the inner conductor is completed by comparative analysis.A test platform for microwave plasma ignition and combustion has been constructed.The test platform consists of a microwave generation component,a microwave ignition component and a test data acquisition component.A rectangular waveguide propagates microwave energy at 2.45 GHz in TE10 mode,generating a standing wave in the resonant cavity and amplifying it by means of a concentrated electric field at the tip of the inner conductor to produce a plasma of sufficient energy for the ignition of ADN-based liquid propellants.Secondly,the effect of microwave power on the combustion of ADN-based liquid propellants was investigated by means of experiments.The flame height,temperature and emission spectra of the combustion at different power levels were measured using a controlled variable approach.The test results show that microwave power has a facilitating effect on the combustion of ADN-based liquid propellants,with an increase in microwave power from 1500 W to 2500 W,an 86.4% increase in flame length,a 200 K or approximately 20% increase in flame temperature and a significant increase in the peak intensity of some radicals in the spectra.Finally,the effects of gas flow and ADN-based liquid propellant flow on combustion were investigated separately.The gas flow rate and the ADN-based liquid propellant flow rates were adjusted separately to study their effects on combustion,keeping other operating conditions constant.The test results showed that the flame length and temperature was the highest at 14.32 cm and 1533 K for a gas flow rate of20L/min and an ADN-based liquid propellant flow rate of 30 m L/min respectively.The experimental work proved the feasibility of microwave plasma ignition of ADN-based liquid propellant,and initially explored the combustion characteristics of ADN-based liquid propellant,providing a basis of future engineering applications of microwave plasma ignition devices.