Size Distribution of Particles in Combustion Products of Aluminized Composite Propellant

An experimental study is carried out to measure the size distribution of condensed particles in the combustion products of aluminized composite propellant using quench bomb technique. One meter long and 200 mm diameter quench bomb with propellant specimens of mass ∼32 g is used. The effects of geometry of propellant specimen, quench distance, and chamber pressure on the particle size distribution are investigated. Size distribution of the particles is measured by laser diffraction particle size analyzer and the surface structure is examined by scanning electron microscope. The study shows that the particles are spherical and their sizes vary from 0.1 to 300 μm. The particles have trimodal distribution with modes at ∼1 μm, ∼4 μm, and μ70 μm. Although modes 1 and 4 μm particles are alumina, mode 70 μm particles are aluminum agglomerates. About 30% of aluminum present in the propellant converts into agglomerates. Results also show that coalescence of particles is higher if the particles have higher residence time in the high-temperature region or when the flow is more turbulent. From the particle size distribution obtained in the quench bomb tests, the size distribution is deduced for the combustion chamber of rocket motor.