Nozzle ablation on flow field and performance of solid rocket motor

Ground-based motor experiments were conducted to investigate the throat ablation mechanism in solid rocket motors. The internal profiles of sectioned nozzles were characterized using high-precision scanning to determine the ablation structure. A dynamic ablation rate calculation method was established for nozzle throat diameter evolution analysis during motor operation. Numerical simulations based on the commercial software Fluent employing the SST (shear-stress transport) k-ω turbulence model analyzed internal flow field modifications induced by surface ablation, while ground experiments quantified performance variations attributable to distinct ablation structures. The maximum observed ablation rate at the nozzle throat is 0.124 mm/s, while the average ablation rate is 0.08 mm/s. Distinct ablation regimes are observed along the nozzle liner, with the convergent section exhibiting a peak ablation rate of 0.3 mm/s for the high-silicon fiber, while the divergent section shows 0.16 mm/s for the carbon-phenolic. Both values significantly exceed the 0.08 mm/s ablation rate measured for the carbon/carbon throat liner. The ablation-induced surface irregularities on the nozzle contour generate multiple complex shock waves in the divergent section. These shock structures cause substantial flow parameter variations, with the axial Mach number experiencing up to 68.6% reduction through shock interactions. Furthermore, the ablation step in the divergent section creates recirculation zones that suppress flow expansion and acceleration, ultimately degrading motor thrust performance. The thrust coefficient demonstrates an initial slight increase within a specific range of ablation step heights before undergoing a sharp decline. Nozzle profile ablation significantly deteriorates flow performance, resulting in a maximum performance loss of 5.11%.