THERMAL SHOCK PROTECTION BASED ON MICROTUBE AND MICROPOST ARRAY SURFACE
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摘要: 针对核电站核泵主轴、管道系统等高温环境下工作的部件受冷却水热冲击而容易出现裂纹的问题,提出通过表面微结构设计,利用水低热扩散率的特性,在被热冲击表面产生隔热水膜,从而降低瞬态热冲击过程中表层结构的热应力,防止结构热疲劳损伤. 针对这一设想,采用有限元与无限元相结合的办法,解决热应力分析的多尺度问题. 利用COMSOL多场耦合分析软件,对瞬态热冲击条件下,表面微结构的温度场与热应力分布进行分析,研究了冲击时间、微结构几何参数和流体黏性底层厚度等对微结构表面热冲击防护能力的影响. 研究发现,表面微柱或微管结构对降低短时间冷水冲击产生的表面热应力具有显著效果,同时在微结构与基底之间存在最优过渡曲面使表面热应力最小化.Abstract: To prevent primary pump shaft and the piping system from crack caused by the thermal shock of cold water at the nuclear power facilities, a new method for thermal shock protection is proposed. The proposed thermal shock protection technique is based on bionic surface with microstructure covered with a layer of water film. Due to the low thermal diffusivity of the water film,the thermal stress at the surface caused by the thermal shock is reduced and the probability of the thermal fatigue failure of the structure will be decreased. In the present paper,using COMSOL multifield coupling analysis software,the temperature field and thermal stress distribution of microstructure at the solid surface are analyzed combining finite elements method and infinite elements method. Effects of thermal shock time, the transition corner between microstructure and bulk material, the thickness of viscous boundary layer and the boundary temperature di erence on the surface thermal stress are studied. Based on the simulation results,it is found that the surface thermal stress is remarkably reduced contributed to the surface microtubes and microposts array structure, and there is an optimal shape of transition structure between microstructure layer and bulk material for minimizing thermal stress.
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Key words:
- thermal shock /
- microstructure surface /
- water film /
- thermal stress
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