학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 김규홍.Ablation experiments for pure tungsten and tungsten composites, W-HfC and W-ZrC, with addition of Computational Fluid Dynamics were performed to study the ablation characteristics and ablation resistance of the materials. Ablation characteristics of pure tungsten with respect to enthalpy and stagnation pressure were studied through series of ablation experiments. The amount of recession caused by ablation increased with respect to enthalpy and the mass lost due to ablation was found to be linearly proportional to the stagnation pressure. In addition to the experiment, ablation phenomenon analysis framework was established. Tungsten ablation was analyzed for the mentioned experiments to obtain results, such as maximum surface temperature, interior temperature distribution of the tungsten specimen, etc., which were not possible with the experiments. Moreover, to overcome the weakness of tungstenvulnerable to oxidation and ablation in high-temperature conditions, W-ZrC and W-HfC composites were manufactured using three different methods. Ablation experiments and micro-structural analyses were carried out to study the ablation characteristics and ablation resistance of W-ZrC and W-HfC with respect to manufacturing method and volume fraction of ZrC and HfC. Methods to increase tungsten composites ablation resistance were suggested with the basis of results of the experiments, CFD analyses, and micro-structural analyses. The suggested methods were to produce composites with small particles and to form ZrOx, HfOx layer on the surface.Abstract I
Table of contents II
List of figures IV
List of tables VI
1. Introduction 1
1.1 Background 1
1.2 Refractory metal for rocket nozzle throat 1
1.3 Ablation phenomenon of tungsten 2
2. Ablation experiments of pure tungsten 5
2.1 150 kW plasma generator 6
2.2 Enthalpy varying ablation experiments 9
2.2.1 Experimental conditions for enthalpy experiments 9
2.2.2 Experimental results for enthalpy experiments 10
2.3 Stagnation pressure varying ablation experiments 18
2.3.1 Experimental conditions for stagnation pressure experiments 19
2.3.2 Experimental results for stagnation pressure experiments 20
3. CFD analysis of pure tungsten ablation 22
3.1 Ablation phenomenon CFD analysis framework 22
3.1.1 Plasma generator interior flow analysis 23
3.1.2 Nozzle downstream flow condition analysis 25
3.2 Shape change analyses with respect to temperature 27
3.2.1 Shape change analyses conditions 27
3.2.2 Shape change analyses results 28
3.3 Mass loss analyses with respect to stagnation pressure 30
3.3.1 Mass loss analyses conditions 30
3.3.2 Mass loss analyses results 31
4. Tungsten composites ablation resistance study 32
4.1 Methods of manufacturing tungsten composites 32
4.2 Ablation resistivity with respect to HfC fraction 34
4.2.1 Experimental conditions of W-HfC ablation tests 34
4.2.2 Experimental results of W-HfC ablation tests 35
4.3 Ablation resistivity with respect to ZrC fraction 37
4.3.1 Experimental conditions of W-ZrC ablation tests 37
4.3.2 Experimental results of W-ZrC ablation tests 37
4.4 Suggestions to increase ablation resistance 39
5. Conclusion 41
6. References 42
국문초록 46Maste
