Research on Thermo-Ablation of Thermal Protection Material of Ramjet Combustion Chamber

摘要

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. Aider 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.

目录

英文文摘

声明

1. Introduction

1.1 Background

1.2. Literature review of related works

1.2.1 Experiment research

1.2.2 Theoretical model research

1.3 Main works in this paper

2 Thermo-ablation models and chemical reaction flow field models

2.1 Thermal protection systems

2.2 Thermo-ablation models

2.2.1 Ablation mechanism of EPDM thermal protection material

2.2.2 Ablation physical models

2.2.3 Ablation mathematical models

2.3 Chemical reaction flow field models

2.3.1 Turbulence flow and governing equation

2.3.2 Boundary conditions

2.3.3 Initial conditions

2.4 Film coefficient

2.4.1 Eddy-dissipation heat transfer

2.4.2 Forced-convection heat transfer

2.5 Chapter conclusion

3. Numerical simulation on chemical reaction flow field of ramjet chamber

3.1 Physical model of ramjet combustion chamber

3.2 Simulation model and boundary conditions

3.2.1 Simulation model

3.2.2 Initial and boundary conditions

3.3 Results of numerical simulation on chemical reaction flow field

3.3.1 α =30 degree, and f=7.3, 10 and 12

3.3.2 α=45 degree, and f=7.3, 10 and 12

3.3.3 α=60 degree, and f=7.3, 10 and 12

3.4 Chapter conclusions

4. Simulations on thermo-ablation of the thermal protection material

4.1 Introduction of ANSYS

4.1.1 Preprocessor

4.1.2 Solution processor

4.1.3 Postprocessor

4.1.4 Phase change

4.2 Virgin materials thermo-gravimetric analysis, TGA

4.3 Ablation model and computational mesh of thermal protection material

4.4 Numerical simulation of heat transfer and ablation

4.4.1 The angle of gas flow α=30 degree and mass flow rate ratio f= 7.3, 10 and 12

4.4.2 The angle of gas flow α =45 degree and mass flow rate ratio f= 7.3, 10 and 12

4.4.3 The angle of gas flow α =60 degree and mass flow rate ratio f= 7.3, 10 and 12

4.5 Chapter conclusions

5 Experiment investigations on thermo-ablation of thermal protection material

5.1 The surface regression rate to the heat transfer

5.1.1 Ablation

5.1.2 Description of material and environment

5.1.3 Decomposition

5.2 Thermo-ablation experiment on thermal protection material

5.2.1 Description of test system

5.2.2 Results of test under oxygen-poor conditions

5.2.3 Results of test under oxygen-rich conditions

5.3 Compare with experiment results and calculation results

5.4 Experiment conclusions

6 Conclusions and recommendations

6.1 Conclusions

6.2 Recommendation

Acknowledgements

References