饱和氢气加注过程中低温贮箱降温特性及热应力分布的数值研究

Investigation on Cool-Down Behavior and Thermal Stress of Cryogenic Tank During Saturated Hydrogen Gas Filling Process

为了获得低温贮箱在饱和氢气加注过程中的降温特性以及箱体壁面的热应力分布,通过计算流体力学软件FLUENT计算了一定加注流量下贮箱内部流体区域的流场、温度场和壁面内的温度场变化,分析了加注过程中贮箱内的流动特性和降温特性;采用单向流固耦合方法进行壁面热应力分析,得到了3种不同进、出口约束条件下热应力在壁面中的分布以及最大热应力随时间的变化情况,并分析了进、出口弹性支撑约束条件设置的合理性;考虑贮箱内的压力变化,进行了箱体壁面的综合应力分析。计算结果表明:加注过程可以分为3个阶段,前2个阶段贮箱内部的流场、温度场和壁面温度分布特性依次由入口强制对流和壁面自然对流单独决定,第3阶段由入口强制对流及壁面自然对流共同决定;在3种不同的约束条件下,箱体壁面中的最大热应力均出现在贮箱加注口和排气口处,在进、出口弹性支撑条件下,壁面最大热应力随时间先增大而后趋于稳定,在稳定应力状态下,热应力的存在使箱体壁面总应力增加了15%左右。

A numerical study is performed on the cool-down behavior and thermal stress of a cryogenic tank during the saturated hydrogen gas filling process. CFD simulation is carried out to obtain the flow and temperature distributions inside the tank and the temperature distribution of the tank wall under a specific filling rate. Then the flow and cooling characteristics of the tank during the filling process are analyzed. The thermal stress in the tank wall under three different constraints of the inlet and outlet is calculated with unidirectional fluid-solid coupling method, and the spatial distribution and transient behavior of the thermal stress are revealed. In addition, the rationality of applying elastic supports to the inlet and outlet is demonstrated, and the integrated stress in the tank wall is calculated with the pressure variation in the tank taken into account. Numerical results show that the filling process can be divided into three steps, where the flow and temperature distributions inside the tank are governed by the forced convection from the inlet or the natural convection near the wall in the first and second steps, and by both of them in the third step. The maximum thermal stress appears at the inlet and outlet of the tank under any of the three constraints. For radial elastic support on the inlet and outlet, the maximum thermal stress increases gradually to a steady value and takes up about 15% of the maximum integrated stress in steady state.