Study On Solid Ramjet Insulator Ablation&Its Relation To Ramjet Structrue

Solid Ramjet features with its high velocity, high specific impulse and wellmaneuverability. These merits make it a good candidate of weapon power system.Thermo Protection is a key technology in ramjet development. And it’s also the bottleneck in solid ramjet research. So, the research on ramjet insulator ablation would makesignificant progress on ramjet research.In this paper, one kind of silica insulators has been taken into research. Approachesof theory analysis, numerical computation, and experimental study have been applied inthis research. And with the conclusion of this research, the ramjet inlet has been optimaldesigned, in order to maximize total pressure recovery and minimize insulator ablationrate.First, thermo-chemical ablation model has been established based on classicalthermo transfer theory. A2-D numerical simulation result shows that the temperaturecontrols insulator ablation rate. And non-uniform temperature distribution inducesablation holes on insulator surface. With the method of CVT, Constant-VolumeTetrahedron, boundary condition problems on fluid-solid interface have been solved.And a3-D numerical simulation has been computed. On the two sides of each inlet,there are two zones of high temperature, and also two ablation holes. The temperature ofzones that downstream of the combustion chamber declines quickly. And insulatorablation on these zones is not such serious as zones besides the inlet. The ablation rategets bigger while the char layer generates. And also chemical ablation rate wouldgradually approach a constant after char layer generates.According to silica insulator ablation features, three kinds of insulator ablationmechanics have been analyzed, including ablation due to gas blowing, particleimpingement and thermo-chemical ablation. Based on the assumption of stable silicidesgeneration rate, the insulator ablation model has been established. It is calculated thechemical ablation rate, gas-bolowing ablation rate and particle erosion rate under acertain condition. The numerical simulation result shows that, among these3mechanics,gas blowing is the main effect causing TPS failure. The zones besides inlet anddownstream the combustion chamber are seriously ablated. The gas temperature is veryhigh in this zone.The particle movement after impingement has been analyzed. The effect of solidparticles and liquid particles to insulator ablation has been argued. Heat transfer andparticle erosion are the main particle effects. The liquid particles, with high speed andlarge particle diameter, strengthen insulator heat transfer. After impingement, rather thanadhering on the insulator, they all split into small particles, and spray out. Also, particlesof large diameter charge the particle erosion. The zones with serious particle erosion locate at the centry of the combustion chamber.Ramjet structure parameters’ effect to insulator ablation has been argued. It isfound that the structure of gas generator outlet affects insulator ablation. The insulatorablation of the one having only one jet on gas generator declines while compared to theone having5jets. The zone with most serious ablation moves to the downstream of thecombustion chamber and is far from the inlet. The distance of two neighbor jets haslittle affect to ablation due to gas blowing, but heavily affects the chemical ablation.The inlet angle affects ablation due to gas blowing. Small inlet angle makes themaximum ablation rate decreases. Small inlet angle also makes temperature of the gas,adjacent to the chamber wall, increases. But this makes the chemical ablation rate getlarger. Inlet area reducing enhances the velocity of air flow. And this makes themaximum ablation rate decreases.Based on the conclusions of other ramjet structure parameters’ effects on inlet, theinlet has been optimal designed. Minimizing gas-blowing ablation rate and the tunnellength are taken as two optimal targets in inner tunnel design. The optimal results shows,the length of flat tunnel has little affect on the tunnel length. Inlet angle affects both theablation rate and inlet inner tunnel length.