Study on Three-dimensional Thermal-hydraulic Characteristics of a Space Reactor based on Open Lattice Structure
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摘要: 高温气冷堆结合磁流体发电是一种高效的空间电源系统，可以满足空间任务对于大功率、高效率的需求，具有广阔的应用前景。本文参考美国普罗米修斯计划中的开放栅格方案，结合磁流体发电需满足的设计条件，提出了一种由三角形布置、217根燃料棒构成的堆芯方案。在通过试验数据确定流动模型后，对该空间堆进行了三维建模，并在考虑气隙结构、燃料棒功率分布及堆内辐射的基础上研究其热工水力特性，重点针对环境温度及外壁面发射率展开了热工参数敏感性分析。计算结果表明，该堆芯热工设计满足材料温度、压降限值等指标要求。冷却剂在燃料区横向流动不明显，不存在复杂涡结构，流动现象相对较为简单。稳态热工计算结果对环境温度的改变并不敏感，但发射率的改变影响相对较大。Abstract: High temperature gas cooled reactor combined with magnetohydrodynamic (MHD) power generation is an efficient space power system. It can meet the requirements in space tasks for high power and high efficiency and thus has broad application prospects. In this paper, a core scheme composed of 217 fuel rods in a triangular arrangement is proposed in accordance with the design conditions to be met for MHD power generation and with the reference to the open lattice scheme in Prometheus Project. The three-dimensional modeling of the space reactor is carried out after determining the flow model through the experimental data. The thermal-hydraulic characteristics are studied on the basis of taking into consideration the gap structure, the fuel rod power distribution and the in-reactor radiation. Finally, sensitivity analysis on thermal parameters is carried out mainly for the ambient temperature and the external surface emissivity. The calculation results show that the thermal design of the core meets the requirements of material temperature and pressure drop limit. The transverse flow of coolant in the fuel area is not obvious and there is no complex vortex structure. The flow phenomenon is relatively simple. The steady-state thermal calculation results are not sensitive to the change of ambient temperature, but the change of emissivity has a relatively large impact.
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图 1 棒状燃料空间堆结构示意图
Figure 1. Schematic Diagram of Rod-shaped Fuel Space Reactor Structure
图 2 试验段示意图及模拟件示意图
Figure 2. Schematic Diagram of Experimental Section and Schematic Diagram of Analog Parts
图 3 其他工况条件下不同特征棒在不同高度处平均温度的测量值与模拟值
Figure 3. Measured and Analog Values of Average Temperature of Different Characteristic Rods at Different Heights under Other Working Conditions
图 6 轴向功率因子随轴向无量纲高度变化关系式
R2—拟合系数
Figure 6. Relationship between Axial Power Factor and Axial Dimensionless Height
图 8 特征面选取位置示意图
Figure 8. Schematic Diagram of Selected Location of Characteristic Surfaces
图 9 冷却剂在三个特征面的速度矢量图
Figure 9. Velocity Vector Diagram of Coolant on Three Characteristic Surfaces
图 10 冷却剂在三个特征截面的压强分布云图
Figure 10. Pressure Distribution Nephogram of Coolant on Three Characteristic Surfaces
图 11 冷却剂在三个特征截面的温度分布云图
Figure 11. Temperature Distribution Nephogram of Coolant on Three Characteristic Surfaces
表 1 棒状燃料空间堆基本参数表
Table 1. Basic Parameters of Rod-shaped Fuel Space Reactor
参数名 参数值 参数名 参数值 燃料棒数目 217 铼包壳外半径/cm 0.775 堆芯对边距/cm 26 单栅格边距/cm 1.75 堆芯活性区高度/cm 50 燃料富集度/% 75 反应堆直径/cm 44 235U装载量/kg 155 反应堆高度/cm 72.5 金属铀装量/kg 207 轴向空腔高度/cm 2 反应堆总重量/kg 523 径向流道高度/cm 1 功率密度/(MW·m−3) 34.2 压力容器厚度/cm 0.25 轴向反射层开孔基准孔径/cm 0.35 轴向反射层厚度/cm 8 端塞直径/cm 0.2 UN芯块半径/cm 0.688 包壳内半径/cm 0.69 
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表 2 不同流量及功率下的试验工况
Table 2. Experimental Conditions under Different Flow Rates and Powers
试验编号 期望流量/(kg·h−1) 功率/W 备注 2-100 48.68 37×73 基准工况，实际流量48.57 kg/h 2-110 58.42 37×73 120%高流量 2-120 48.68 37×73/2 50%低功率 2-130 24.34 37×73/2 50%低功率低流量 2-140 48.68 37×73 带功率分布
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表 3 径向功率因子
Table 3. Radial Power Factor
棒编号 径向功率因子 棒编号 径向功率因子 棒编号 径向功率因子 1 1.126 10 1.106 19 0.962 2 1.117 11 1.075 20 0.933 3 1.099 12 1.036 21 0.997 4 1.063 13 0.990 22 0.967 5 1.018 14 0.942 23 0.941 6 0.966 15 0.907 24 1.019 7 0.917 16 0.958 25 1.008 8 0.874 17 1.044 9 0.928 18 1.006
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表 4 不同网格下的计算结果
Table 4. Calculation Results under Different Meshes
网格编号 网格数
目/万反应堆压
降/kPa压降相对
偏差/%包壳最高
温度/K温度相对
偏差/%mesh 1 284 23.68 3.58 2135 0.19 mesh 2 386 23.71 3.46 2137 0.09 mesh 3 523 24.48 0.32 2139 0 mesh 4 613 24.56 2139
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表 5 空间堆三维稳态热工水力计算结果
Table 5. Three-dimensional Steady-state Thermal-hydraulic Calculation Results of Space Reactor
物理量 计算值 物理量 计算值 入口温度/K 1100 出口温度/K 1734.5 运行压力/MPa 0.4 反应堆压降/kPa 23.75 燃料最高温度/K 2146.7 压力容器最高温度/K 1774.7 包壳最高温度/K 2103.0 反射层最高温度/K 1957.4 气隙最高温度/K 2118.3 冷却剂空腔区最高温度/K 2062.9 冷却剂燃料区最高温度/K 2101.0 冷却剂进出口区最高温度/K 1899.9 冷却剂开孔区最高温度/K 1985.8
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表 6 不同环境温度及壁面发射率条件下的稳态热工计算结果
Table 6. Steady-state Thermal Calculation Results under Different Ambient Temperatures and Wall Emissivities
环境温度/K 外壁面发射率 燃料最高温度/K 包壳最高温度/K 反应堆出口温度/K 反应堆压降/kPa 200 0.5 2146.7 2103.0 1734.5 23.75 300 0.5 2146.8 2103.9 1734.7 23.76 400 0.5 2148.0 2104.3 1734.8 23.77 200 0.3 2169.0 2126.0 1752.3 24.00 200 0.7 2105.8 2060.0 1715.3 23.50
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