Research On Thermo-Ablation Of Thermal Protection Material Of Ramjet Combustion Chamber

EPDM is a kind of charring ablation material and is usually used as inner thermal protection material for some kinds of ramjets. The analysis of thermo-ablative properties of EPDM thermal protection material of ramjet combustion chamber is presented under different conditions with different injection angles of the gas flow and mass flow rate ratio between air and fuel. The ablation mechanism and the ablation model of EPDM are established. The numerical simulations of thermo-ablation and ground test are both carried out.Due to the need of heat load boundary for the calculation of thermo-ablation model, the temperature distribution of internal chemical reaction flow field of chamber is needed. So the simulation on chemical reaction flow field with different injection angles and mass flow rate ration is solved by the CFD software FLUENT. Then the temperature distribution is loaded as the heat load boundary in the analysis of thermo-ablation analysis. The thermo-ablation models are solved by the FEA software ANSYS.The ground tests of oxygen-rich and oxygen-poor were carried out. After both tests, the surface layer of ablation samples comes into being a layer of carbon, which is called charring layer. At the state of oxygen-poor, pyrolysis takes place inside the EPDM sample, and no combustion happens at the surface of sample in the process of ablation. Because of the obstruction by charring-layer and the material above, along with the pyrolysis gas flowing out, the inner pressure increased gradually. Then the material began to expand along with the pressure increase, so the sample after test is thicker than that of origin sample. At the oxygen-rich situation, the condition is worse than that of oxygen-poor, because except pyrolysis inside the sample, the charring layer at the surface of sample formed during the ablation can react with oxygen inside the combustion gas, and suffered erosion by the higher-speed combustion gas flow inside the chamber and so on. The ablation process continues, and the heat imported layer-by-layer until the end of ramjet operation. So part of the test samples under oxygen rich were burnt through. Finally, the calculation results are compared to the test results, and the results show that the calculation results are consistent with the test results basically.