Peijin Liu

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 150μm to 450μm 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.

Design and Numerical Investigations on a Dual-Duct Variable Geometry RBCC Inlet

Abstract A widely applicable and variable geometry 2-D rocket based combined cycle (RBCC) inlet characterized by the dual-duct design is conceptually put forward. The inlet operates as dual-duct status in the low Mach range (0~4), and transits to single-flowpath status in the following high Mach range (4~7). It accomplishes operational status transition through an 8.0-degree ramp rotation and a 4.0-degree cowl rotation at Mach 4. Through numerical simulations on typical flight Mach numbers, the observed starting Mach number is 2.2, which provides a sufficient operational window for a smooth ejector-to-ramjet mode transition. The RBCC inlet achieves comprehensive high mass capture coefficients in the overall wide flight range, especially in the low speed regimes. Suitable Mach numbers satisfying various combustion requirements in different modes together with high total pressure recovery coefficients are also obtained since the physical throat areas, compression angles, and the corresponding contraction ratios can be adjusted by a large margin through very limited rotations. The variable geometry scheme is not only feasible for practical realizations, but is also simple to arrange the dynamic sealing issues in a low-temperature environment in the RBCC engine.