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在自然循环工况下,倒U型蒸汽发生器(U-tube steam generator,UTSG)内有部分倒U型管会发生倒流现象,严重影响一回路系统的自然循环能力。本文采用计算流体动力学(computational fluid dynamics,CFD)方法对自然循环工况下UTSG一次侧流体的流动特性进行三维数值模拟研究。结果表明,在低流量下,倒流集中发生在短管侧。等长倒U型管中同时出现了倒流和正流的现象,与入口腔室给予各个倒U型管分配的初始流量有关。随着UTSG入口总流量的增加,蒸汽发生器倒流管数减少;随着一次侧入口温度的升高,蒸汽发生器进出口压降为负值,压差绝对值逐渐增大,倒流管数增多。
Under the natural circulation condition, some inverted U-shaped tubes in U-tube steam generator (UTSG) flow backwards, seriously affecting the natural circulation capacity of the primary loop system. In this paper, computational fluid dynamics (CFD) method is used to study the three-dimensional numerical simulation of the flow behavior of UTSG primary fluid under natural circulation. The results show that, at low flow rates, backflow occurs centrally on the short tube side. Isometric inverted U-tube at the same time there is a backflow and positive flow phenomenon, and the inlet chamber to give each inverted U-shaped tube initial flow distribution. As the total inlet flow of UTSG increases, the number of steam generator backflow tubes decreases. With the increase of primary inlet temperature, the pressure drop at the inlet and outlet of steam generator is negative, the absolute value of pressure differential increases, and the number of backflow tubes increases .