基于移动边界模型的空冷阵列动态性能数值研究

Numerical Study on Transient Thermo-hydraulic Characteristics of ACCs Array Based on Moving-boundary Model

研究动态自然风扰动下空冷阵列的热力学特性,对设计轴流风机的转速控制器具有重要意义。文中以6×5空冷阵列物理模型为数值模拟对象,基于移动边界模型和滑移网格方法,建立与求解时变风速和时变风向下的空冷阵列瞬态数学模型,并通过对比风机入口风速的实验数据和数值解,验证模型的有效性。数值结果表明,空冷阵列的风机入口平均温度和平均速度对环境风速的变化响应快速无时滞;在连续型环境风速变化下,迎风面第2行轴流风机入口空气流量可定性为风速的负系数比例对象;在脉冲型环境风速变化下,空冷阵列入口热风回流率可定性为环境风速的有差自平衡对象。空冷阵列在风向变化过程中,迎风面第1行风机的入口流量受自然风影响最大,并且迎风面位置随风向变化动态移动,移动带有2s左右的时间延迟;在风向反转下,风向边缘侧出现热风回流的轴流风机会发生位置对调。根据数值模拟结果,给出了5点关于轴流风机群分区与转速控制的建议。

It is of great significance to studying the thermodynamic characteristics of air-cooled arrays(ACA)under dynamic natural wind disturbance is of great significance for designing the speed controller of axial flow fans.Based on the moving boundary model and sliding grid method,a transient mathematical model to cooling-air flow through a 6×5 ACA under the nature wind with time-varying speed and direction was developed and calculated numerically,moreover,the predicted air velocity at the inlet of fans were compared with experimental results to verify the model.The numerical results show the following:1)The inlet temperature and velocity of ACA response to wind speed without time delay;under the nature wind with continuous-varying velocity,the air flow of the second-row axial fans in the upwind stream can be classified to a negative proportional object to the wind velocity;the inlet hot wind reflux rate can be classified to a self-balance object with final bias to the pulse of wind velocity.2)The inlet air flow of upwind row is most affected by the natural wind,and the dynamic movement has a time delay of about 2s;during the wind direction reverses,the hot reflux phenomenon is observed in the inlet of axial fans on the two side of wind direction,furthermore,these fans transpose in a delay of about 10s with the wind reversing.According to numerical results,5 recommendations are proposed to the sub-grouping of fans cluster and controlling of fans rotation.