Effect of Heating Rate on Ignition Characteristics of Newly Prepared and Aged Aluminum Nanoparticles

Abstract

AbstractAluminum (Al) nanoparticles have been widely applied in propellants, but the ageing of Al nanoparticles will result in the degradation of propellant ignition performance. This paper experimentally investigates the ignition characteristics of newly prepared and aged Al nanoparticles, and improves the ignition performance of aged Al nanoparticles through elevating the heating rate. It was observed that, despite newly prepared or aged Al nanoparticles, their ignition included three stages: stage I – heating, stage II – melting, and stage III – evaporation. The temperature rise and time in stage I, melting temperature, and time in stage II and ignition temperature in stage III were separately discussed. It is found that the duration of each stage during the ignition of aged Al nanoparticles was much longer than that of newly prepared Al nanoparticles, testifying that ignition temperature of Al nanoparticles increased and ignition delay time elongated due to ageing. At elevated power density, the heating rate of Al nanoparticles increased, the heating, melting, and evaporating time shortened. The difference of ignition delay time between newly prepared and aged Al nanoparticles was significantly reduced. It means that the ignition performance can be improved through increasing the heating rate. Simultaneously, the energy conversation equation of each stage was built and discussed. It will be beneficial to deeply understand the ignition process and reveal the ignition mechanism of aged Al nanoparticles.