Insulator ablation modes in different impact conditions of alumina droplets onto wall surfaces

Current understanding of insulator ablation modes under different alumina droplet impact conditions onto wall surfaces in solid rocket motors (SRM) is limited. This study uses theoretical analysis and numerical calculations to design a lab-scale experimental device and an ultra-high-temperature heat flow gauge. Alumina droplet/insulator wall surface impact characteristics such as erosion angle, speed, and droplets size distribution are discussed based on the resulting experimental data using the proposed design. Three ablation modes are established according to the droplet speed threshold: the weak erosion state, deposition state, and strong erosion state. On this basis, heat transfer characteristics are studied under the condition of high-density, two-phase flow and the general rules of the wall heat increment with droplet concentration, size, and velocity under different droplet/wall impact modes are obtained. Finally, discussing multi-factor variables, the coupling relationship among the thermal increment, thermal chemical ablation, and mechanical erosion under droplet/wall surface action is analysed, providing insights toward establishing an insulator ablation model.