Aluminum–water (Al-H₂O) propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature. However, conventional formulations are hindered by significant aluminum (Al) agglomeration, leading to reduced combustion efficiency and substantial residues. This study introduces a method for modifying Al powder with Polyvinylidene Fluoride (PVDF) to enhance the performance of Al-H₂O propellants by mitigating agglomeration during combustion. Experimental methodologies, including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests, were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants. Furthermore, the effect of PVDF on motor performance was systematically evaluated through laboratory-scale Solid Rocket Motor (SRM) tests. The results demonstrate that the addition of 7.5% PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699 μm to 527 μm. Combustion efficiency rises from 88.57% to 94.51%, while injection efficiency improves significantly from 30.45% to 70.45%. SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa. A dynamic agglomeration model explains these improvements, attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer, while increased gas yield improves injection performance. This study highlights PVDF’s potential in advancing Al-H₂O propellants by improving combustion and injection efficiency.

A novel constant-pressure and constant-quenching distance Condensed Combustion Products (CCPs) collection system was developed, coupled with a timing control system, to collect the CCPs formed in the course of burning of aluminum-based composite propellants. The effects of adiabatic graphite plating, collection zone, quenching distance, time series of collection, and propellant burning rate on the microscopic morphology, particle size distribution and unburned aluminum content of CCPs were investigated. It was verified that the graphite plating can provide a high-fidelity high-temperature environment for propellant combustion. The combustion efficiency is improved by 2.44% compared to the bare propellant case. The time series of collection has a significant effect on the combustion efficiency of aluminum, and the combustion efficiency of aluminum in the thermal state (1.2–2.4 s) is 2.75% higher than that in the cold state (0–1.2 s). Similarly, the characteristics of the CCPs in different collection zones are different. At the quenching distance of 5 mm, the combustion efficiency of aluminum in the core zone (85.39%) is much lower than that in the outer zone (92.07%), while the particle size of the CCPs in the core zone (172 μm) is larger than that in the outer zone (41 μm). This indicates that the core zone is more likely to produce large-sized and incompletely burned agglomerates during the propellant combustion process. Different burning rates also lead to a significant difference in particle size distribution and combustion efficiency. High burning rates result in higher combustion efficiency. A detailed sequence of the elaborative collection process of CCPs is proposed, mainly including the setting of ignition delay time, burning rate, working pressure, plating length and time series of collection. The findings of this study are expected to provide a reliable tool for the evaluation of the combustion efficiency of solid propellants.