专用堆型对应的核主泵正反转流动数值模拟

为了研究核主泵在定转速工况下的正反转特性,采用相似换算法,基于SST k-ω 湍流模型与块结构化网格,对缩比系数为0.5 的核主泵模型泵进行数值模拟.定义流量从泵进口流向出口为“+”,反之为“-”.在正转工况下分别对-0.8Q_d到+2.0Q_d流量范围内的16个工况点进行计算、反转工况下对-1.4Q_d到+1.0Q_d流量范围内的14个工况点进行计算,得到其全特性曲线.计算结果表明:在相同流量工况下,核主泵正转时的扬程与转矩总是高于反转时的扬程与转矩,叶轮扬程与泵扬程存在不同的变化趋势;在正转工况下,在 -0.1Q_d到+0.4Q_d流量范围内,叶轮扬程曲线呈现反“N”型变化趋势;在反转工况下,在-0.4Q_d到+0.1Q_d流量范围内,叶轮扬程曲线呈一个明显的“V”型变化趋势;叶轮出口处产生二次流回流现象,这是正转小流量工况下叶轮扬程降低的主要原因,而叶轮与导叶之间过渡段区域内的环形高速带和叶轮流道内的大尺度涡是反转小流量工况下叶轮扬程降低的主要原因.

Numerical simulation of flow in coolant pump for special nuclear reactor under positive and negative rotational speeds

To identify the characteristics of reactor coolant pump(RCP)under positive and negative constant speeds, numerical simulations of the flow in the model coolant pump scaled down from the real pump with 0.5 scaling factor based on the pump affinity laws were carried out by using the SST k-ω turbulence model and structured-mesh. The flow rate was defined as “+” when the fluid flows into the pump from the inlet, otherwise, it was defined as “-”. The complete characteristic curves were predicted respectively with 16 operating points in the flow range of -0.8Q_d - +2.0Q_d under positive rotational speed, and 14 operating conditions in the flow range of -1.4Q_d - +1.0Q_d under negative rotational speed. The results show that at the same flow rate, the head and torque of the RCP under positive rotational speed are always higher than that under negative rotational speed. The impeller head and pump head have different variation trends. The impeller head curve is in upside-down “N” shape as the flow rate in the range of -0.1Q_d - +0.4Q_d under positive rotational speed, but it is in “V” shape when the flow rate is in the range of -0.4Q_d - +0.1Q_d under negative rotational speed. The internal flow results show that there is a secondary flow phenomenon in the impeller outlet. This flow pattern is mainly responsible for the drop in the impeller head under low flow rate conditions under positive rotational speed. The large-scale vortices in the impeller and the high-velocity region between the impeller and the radial diffuser are the main reason for the drop in the impeller head curve with negative rotational speed under low flow rate conditions.