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As a new type of energy-containing material, Ammonium dinitramide based liquid propellant has the advantages of being green, having low toxicity, good stability, and high safety performance. Traditional catalytic combustion methods require preheating of the catalytic bed and deactivation of the catalytic particles at high temperatures, while microwave ignition methods can effectively solve these problems. To study the combustion characteristics of ADN-based liquid propellants during microwave ignition, the influence of microwave power and gas flow rates on the combustion process are analyzed using experimental methods. A high-speed camera was used to observe the enhanced effects of microwave power and gas flow on plasma and flame. Combined with temperature measurement, the combustion process of ADN-based liquid propellants under the action of plasma was analyzed. The combustion process in the presence of microwaves was observed by comparing parameters such as flame length, flame temperature, and radical intensity. Those results show that, with the increase in microwave power, the luminous burning area of the flame grows significantly. The microwave power is increased by 250 W each, and the flame jet length is increased by nearly 20%. The increase in microwave power also leads to an increase in propellant combustion temperature, however, this increase gradually slows down. At a gas flow rate of 20 L/min, the ADN-based liquid propellant showed the best combustion performance with a maximum jet length of 14.51 cm and an average jet length increase of approximately 85.9% compared to 14 L/min. Too much gas flow rate will hinder the development of the jet, while the high-velocity airflow will have a cooling effect on the flame temperature. The results provide a basis for the specific parameter design of microwave ignition and promote the application of ADN-based liquid propellants in the aerospace field. [ABSTRACT FROM AUTHOR]

Microwave ignition has attracted much attention due to its advantages of reliable ignition, large ignition area and cold-start capability. In this paper, the experimental method is used to explore the ignition ability of the microwave device to ADN-based liquid propellant. Additionally, we discuss the influence of the inlet power and rate of propellant injected into the ignition system on the height of the combustion jet and the combustion temperature. In the experiment, a microwave-assisted ignition system was established based on a special microwave resonant cavity. The liquid propellant and working gas were sprayed into the resonator cavity through the hollow straight tube beneath the resonant cavity. The test results show that the device can ignite the propellant under the condition of 800 W input power, which proves the feasibility of the microwave ignition device for ADN-based liquid propellant. Microwave power has some influence on the flame spray height at the initial stage of combustion. The spray height at 2000 W is increased by 55.7% in comparison to 1000 W. In the stable combustion stage, the input power has a very significant increase in the average temperature of the flame, which is increased by 25%. The combustion is relatively better when the propellant flow rate is 30 mL/min, and the height of the flame spray increases by 25.2%. The increase in throughput did not have a significant impact on the flame temperature. [ABSTRACT FROM AUTHOR]