铝/水两相自点火实验和理论研究

In response to the problems such as unclear ignition mechanism of aluminum-steam and lack of fundamental combustion experimental data in -water ramjet, this study carries out aluminum-steam two-phase self-ignition experiments and theoretical research based on the visualized high-pressure shock tube experimental platform. The temperature effect, pressure effect and scale effect of aluminum are presented from three perspectives: luminous intensity and flame image, self-ignition temperature and ignition delay time. The study reveals the difference of ignition mechanism for aluminum in steam and oxygen and develops the prediction model of aluminum-steam self-ignition temperature. The experimental results demonstrate that the ignition of aluminum- steam follows a mode -where small-sized particles are preferentially ignited, subsequently the larger particles. The critical self-ignition temperature is inversely dependent on the aluminum particle size. The relation bet-ween ignition delay time and temperature conforms to the Arrhenius relation, -with smaller particles exhibiting higher temperature sensitivity in ignition delay time. The ignition delay time of nano-sized aluminum powder exhibits a pronounced pressure-dependent behavior, and with the flame area exhibiting more concentrated under high pressure conditions, the oxidizer competition among aluminum powder particles is more intense. The scale effect on aluminum powder ignition delay time is obvious, and the ignition delay time of 50 jim aluminum powder at 1 500 K is about 30 times that of 100 nm aluminum powder. It is found that aluminum-steam self-ignition characteristic is superior to aluminum-oxygen, and the established aluminum-steam model demonstrates a minor deviation from experimental data in existing literature regarding the self-ignition temperature of micron-sized particles. The fundamental combustion data and theoretical analysis of ignition mechanism in this study offer a theoretical basis for combustion structure optimization and combustion chamber structure design of aluminum water ramjet and present valuable research insights for the development of aluminum-steam ignition mechanism and model.