Experimental investigation on the condensed combustion products of aluminized GAP-based propellants

The condensed combustion products (CCPs) of solid propellants significantly affect the combustion and internal flow inside the solid rocket motor. A constant-pressure quench vessel was used to collect the condensed combustion products of an aluminized glycidyl azide polymer (GAP)-based propellant. The effects of freezing medium, quench distance, chamber pressure (5∼9 MPa) and virgin aluminum size (13∼40 μm) on the physicochemical properties of the condensed combustion products were studied. The typical size distribution of the condensed combustion products is in three modes, 1∼2 μm, 20∼30 μm, ∼300 μm and their sizes vary from 0.3 to 600 μm, corresponding to smoke oxide particles and agglomerates. Freezing medium is found to have little impact on the particle size, while the agglomeration ratio in water is larger than nitrogen and argon. In contrast to the freezing medium, pressure does affect the size of CCPs, but has little effect on the agglomeration ratio. Quench distance has no significant effect on the particle size. Agglomeration is found to increase first and then decreases with the increase of virgin aluminum size. The influence mechanism of freezing medium and virgin aluminum size on CCPs is proposed. The combustion-agglomeration map is particularly obtained, which shows that freezing medium and virgin aluminum particle size have more profound influence on the agglomeration than quench distance and pressure. The low-pressure condition presents poorest performance with high fraction of agglomerates, large agglomerate size and low combustion efficiency. Results of this work are expected to provide better insight in the combustion of solid propellant and solid rocket motor.