火箭推进

核热推进反应堆一般选用氢气做工质,通过堆芯燃料颗粒加热到高温,以实现较高的发动机推力和比冲。基于美国核热推进火箭发动机的典型堆芯设计方案,在高温气冷堆球床有效导热系数模型的基础上,对更小直径的燃料颗粒与更高温度的氢气工质组成的颗粒床混合介质进行了初步计算,获得了燃料种类、颗粒直径、孔隙率等关键参数对堆芯导热能力的影响规律。同时,考虑到燃料颗粒采用多种材料复合而成的包覆型结构,采用均匀化方法对不同材料的基础热物性进行了等效计算,从而为有效导热系数模型提供固体域平均导热参数。从计算结果来看,颗粒直径和孔隙率对有效导热系数的影响更大,特别是高温条件下辐射换热作用占主导,使得材料自身导热系数的贡献很小。

Nuclear thermal propulsion(NTP)is a new-type nuclear reactor application which chooses hydrogen gas as the working medium, heated by fuel pellets in the reactor core to extremely high temperature, so as to achieve huge thrust and high specific impulse. Based on the typical design of reactor core in American NTP rocket engine programs, the effective thermal conductivity model of high temperature gas-cooled reactors was used and preliminary applied, for the analysis of the pellet bed mixed with smaller fuel particles and higher temperature hydrogen gas. The influences of fuel type, pellet diameter and pellet bed porosity on the thermal conductivity of the reactor core were also obtained in this paper. Meanwhile, considering that the fuel pellet was usually coated by multi-layers with different materials, the homogenization method was used for equivalent calculation in thermal properties of these materials, aimed to provide the average thermal conductivity parameters of solid domain for the effective thermal conductivity model. According to the calculation results, the pellet diameter and pellet bed porosity have a greater impact on the effective thermal conductivity, relative to the components thermal conductivity, especially under high temperature conditions that the radiation heat transfer is dominant.

引言
1 颗粒床反应堆典型设计方案
2 有效导热系数计算模型
3 模型应用及初步计算分析
4 结论

表1 核热推进堆芯方案及主要参数对比<br/>Tab.1 Comparison of reactor core and primary parameters for NTP

表1 核热推进堆芯方案及主要参数对比
Tab.1 Comparison of reactor core and primary parameters for NTP

图1 颗粒床反应堆堆芯结构示意图<br/>Fig.1 Structure diagram of the PBR core

图1 颗粒床反应堆堆芯结构示意图
Fig.1 Structure diagram of the PBR core

图2 颗粒床反应堆的氢气流动过程<br/>Fig.2 Flow process of hydrogen gas in the PBR

图2 颗粒床反应堆的氢气流动过程
Fig.2 Flow process of hydrogen gas in the PBR

图3 颗粒床反应堆的燃料球结构类型<br/>Fig.3 Structure types of fuel pellet in the PBR

图3 颗粒床反应堆的燃料球结构类型
Fig.3 Structure types of fuel pellet in the PBR

图4 包覆型燃料颗粒的均匀化<br/>Fig.4 The homogenization of multi-layer coated fuel pellets

图4 包覆型燃料颗粒的均匀化
Fig.4 The homogenization of multi-layer coated fuel pellets

图5 3种燃料颗粒的均匀导热系数<br/>Fig.5 The homogeneous thermal conductivity of three different fuel pellets

图5 3种燃料颗粒的均匀导热系数
Fig.5 The homogeneous thermal conductivity of three different fuel pellets

表2 燃料颗粒的核芯及包覆层尺寸<br/>Tab.2 Dimension of fuel kernel and multi-layers of the fuel particle

表2 燃料颗粒的核芯及包覆层尺寸
Tab.2 Dimension of fuel kernel and multi-layers of the fuel particle

表3 氢气导热系数的数据对比<br/>Tab.3 Parameter comparison of thermal conductivity for hydrogen gas

表3 氢气导热系数的数据对比
Tab.3 Parameter comparison of thermal conductivity for hydrogen gas

图6 氢气导热系数的计算结果<br/>Fig.6 Thermal conductivity of hydrogen gas

图6 氢气导热系数的计算结果
Fig.6 Thermal conductivity of hydrogen gas

图7 3种规则结构的颗粒床堆积方式<br/>Fig.7 Three typical regular stacking of pellet bed reactors

图7 3种规则结构的颗粒床堆积方式
Fig.7 Three typical regular stacking of pellet bed reactors

表4 3种规则结构的颗粒床几何参数<br/>Tab.4 Geometry parameters of PBR for three regular stacking

表4 3种规则结构的颗粒床几何参数
Tab.4 Geometry parameters of PBR for three regular stacking

图8 核燃料对颗粒床有效导热系数的影响<br/>Fig.8 The influence of nuclear fuel on the effective thermal conductivity of pellet beds

图8 核燃料对颗粒床有效导热系数的影响
Fig.8 The influence of nuclear fuel on the effective thermal conductivity of pellet beds

图9 燃料颗粒直径对颗粒床有效导热系数的影响<br/>Fig.9 The influence of fuel pellet diameter on the effective thermal conductivity of pellet beds

图9 燃料颗粒直径对颗粒床有效导热系数的影响
Fig.9 The influence of fuel pellet diameter on the effective thermal conductivity of pellet beds

图10 孔隙率对颗粒床有效导热系数的影响<br/>Fig.10 The influence of porosity on the effective thermal conductivity of pellet beds

图10 孔隙率对颗粒床有效导热系数的影响
Fig.10 The influence of porosity on the effective thermal conductivity of pellet beds

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备注

引言

1 颗粒床反应堆典型设计方案

2 有效导热系数计算模型

3 模型应用及初步计算分析

4 结论

期刊信息