不同四塔组合形式对特大型冷却塔局部非高斯风压分布影响研究

RESEARCH ON NON-GAUSSIAN WIND PRESSURE OF FOUR SUPER-LARGE COOLING TOWERS UNDER DIFFERENT LAYOUTS

非高斯脉动风压是引起冷却塔局部风荷载过大的重要因素之一,群塔干扰会显著改变冷却塔表面风压非高斯分布模式。四塔组合是火/核电厂冷却塔群最常见的组合形式之一,以在建世界最高冷却塔(220 m)为研究对象,针对工程中最典型的串列、矩形、菱形、L形和斜L形五种四塔方案进行刚体测压风洞试验。在此基础上,系统研究不同四塔组合形式冷却塔风压信号的幅域和时域特性,并针对考虑四塔干扰效应的冷却塔二维和三维峰值因子取值问题进行对比探讨,分析不同四塔组合方案对冷却塔风压非高斯特性的影响规律。研究表明,串列、矩形、菱形、L形和斜L形方案分别较单塔工况非高斯区域增加了11%、63%、56%、89%和30%,采用基于高斯分布假定的峰值因子法进行冷却塔群极值风压计算将引起较大的误差。串列和斜L形四塔方案峰值因子分布受塔群干扰影响较小,而矩形、菱形和L形方案峰值因子较单塔明显增大,部分区域峰值因子达到6.5以上。该文研究从机理上分析四塔组合冷却塔群局部风压过大的形成原因,也为进一步探讨不同四塔组合冷却塔群表面极值风压奠定了基础。

Non-Gaussian wind pressure is one of the important factors which cause excessive local wind pressure of cooling tower,and the interference effect of tower group will significantly change the non-Gaussian distribution of wind pressure.Four-tower arrangements are the most common patterns for super-large cooling towers.With the highest cooling tower(220 m)in the world under construction,wind tunnel tests for rigid body were performed under five typical four-tower arrangements in engineering practice,i.e.,single row,rectangular,rhombic,L-shaped,and oblique L-shaped.On this basis,statistical analyses were performed on the wind pressure signals in the amplitude and time domains under different four-tower combination.Contrastive study on the two-dimensional(2-D)and 3-D peak factor of cooling tower considering the four-tower disturbance effect were analyzed.The influence of different four-tower combination on the non-Gaussian characteristics of wind pressure was discussed.The results show that the magnitude of non-Gaussian wind pressure signals under the single-row,rectangular,rhombic,L-shaped and oblique L-shape arrangements increases by 11%,63%,56%,89%and 30%,respectively,as compared with the single tower.The peak factor method based on the Gaussian distribution assumption will cause greater errors than the Sadek-Simiu method.The peak factors of the single-row and oblique L-shaped arrangements are less affected by the interference effect,while the peak factors of rectangular,rhombic and L-shaped arrangements increase dramatically;the peak factors in some positions of the cooling tower are above 6.5 for the rectangular,rhombic and L-shaped arrangements.In this paper,the causes of excessive local wind pressure of cooling tower under the four-tower combination were analyzed from the perspective of formation mechanism,which could be used to calculate the extreme wind pressure of cooling tower under different four-tower combinations.