Numerical and experimental analysis of ablation in graphite nozzles for solid fuel motors

Using heat shield, especially in throat area has a significant effect on combustion chamber pressure and thermal efficiency of solid fuel engines, and so many studies have been made in this field. A precise prediction of regression in throat surface is essential to optimum design of high burning time engines. In this study, ablation of graphite nozzle in solid fuel engines is investigated numerically for a special ingredient composite fuel .Navier Stocks equations together with thermodynamic equations inside the engine as well as thermochemical and thermal conductivity equations on nozzle surface are derived and written in their suitable forms and solved to determine the regression rate of nozzle throat surface. Furthermore, a cartridge full size solid motor by polyester binder fuel was tested and the ablation rate was measured by using a 3D scanner. The experimental pressure-time and thrust-time curves were also derived and used as input data for numerical calculations. Comparison between numerical and experimental results shows a satisfactory agreement. The experimental results show that the ablation has maximum value in the inlet area, and in divergent section is approximately constant and its value is 0.2mm. Because of important effect of ablation rate on the geometry of nozzle throat and so on the performance of the engine, the results of this study may have applicable usage in analyzing and designing solid fuel engines.