Effects of Aluminum Oxide Particles and Gas Properties on the Thermal Response of Solid Rocket Nozzle Liners

Abstract

The propellant formulations, the gas properties in motor chamber, and the aluminum oxide particle sizes for two kinds of solid propellants with approximately 20% aluminum powder have been investigated. The scanning electron microscope photographs of aluminum oxide particles taken from a nozzle entrance show that the aluminized PCP propellant with 47% volumetric fraction AP/HNIW and the bimodal oxidizers, 200/5 µm, can offer greater possibility for increasing aluminum agglomeration than the aluminized HTPB propellant with 64% volumetric fraction AP and the trimodal oxidizers, 400/200/6 µm. The aluminized PCP propellant with energetic plasticizers results in locally greater mechanical erosion in four circumferential sections of the nozzle entrance in line with grain slots, due to the impingement of large particles. However, the HTPB propellant results in greater thermochemical ablation at the blast tube, the throat insert, and the exit cone of rocket nozzle, due to 2.3 times more H2O and CO2 oxidizing species in exhaust gases than the PCP propellant.