Experimental study on combustion of aluminum in composite propellant

Used the optical methods with the long distance microscope and high-speed camera are to study the dynamic combustion process of aluminum particle on and out of the burning surface of the AP composite propellant. The experiments are all conducted in a combustion chamber under 1MPa, 3MPa and 5MPa. All the experiments use the same formulation ammonium perchlorate (AP)/ Aluminum (Al)/ cyclotrimethylene trinitramine (RDX)/ hydroxyl-terminated poly butadiene (HTPB) propellants. Based on the photos captured by camera, aluminum droplets with different particle size are observed. The flow velocity with the combustion gas is calculated. As the particle diameter increasing, the flow velocity becomes small. Under 3MPa and 5MPa the flow velocity are larger than the in 1MPa. But the flow velocity rang from 150um to 450um in 3MPa is close to the 5MPa. Also the weight mean Aluminum agglomerate diameter Dag is calculated. The agglomerate size generally decreases with increase in burning rate of the propellant, and that it also decreases with an increase in pressure. Also the agglomerate size range decreases. The moving motion for the agglomerates under low pressure on the burning surface has been especially observed before they separate from the surface.