Effect of ammonium perchlorate content on the combustion and injection efficiency of Al-H₂O gelled propellant

Aluminum-water (Al-H₂O) propellant is a solid propulsion that offers the advantages of cost-effectiveness and minimal signal feature. Nonetheless, prevailing formulations of Al-H₂O propellants result in 70–80 % combustion residue, presenting a potential hazard in terms of nozzle blockage and specific impulse. In this study, oxidants were introduced into an Al–H₂O propellant to establish a methodology for enhancing combustion efficiency and injection efficiency. Thermal gravimetric analysis, laser ignition experiments, and ignition tests using a laboratory-scale solid rocket motor (SRM) were conducted to systematically investigate the influence of varying ammonium perchlorate (AP) content on the combustion behavior and thrust characteristics of Al-H₂O propellants. The investigation identified a notable improvement in the combustion characteristics of Al-H₂O propellants upon the introduction of AP. Following the inclusion of AP at a mass fraction of 12 %, the propellant exhibited a 36 % reduction in ignition delay time and a 54 % increase in burning rate. After the addition of an appropriate amount of AP, the combustion efficiency of the Al-H₂O propellants increased from 88.4 % to 93.4 %. SRM firing experiments corroborated heightened combustion chamber pressure and thrust for Al-H₂O propellants enriched with AP. Notably, the introduction of 12 % AP resulted in a substantial decrease in propellant residue rate from 66 % to 27 %. This finding demonstrated that the introduction of AP offers a viable means to mitigate the formation of combustion residue, holding promise for guiding the developmental trajectory of Al-H₂O propellants in propulsion systems.