淹没深度对离心式叶轮模态参数的影响

离心式叶轮结构振动及其幅值受周围水体附加质量和阻尼的影响.为了明确不同淹没深度对离心式叶轮动力响应特性的影响，开展了数值计算和实验研究.基于声固耦合方法，开展了空气和不同淹没深度条件下叶轮的模态分析；通过锤击法获得了在空气和不同淹没深度条件下的叶轮结构响应参数，并评价了固有频率的数值预测精度；根据数值计算和实验结果，构建了结构振型、附加质量参数和阻尼参数随淹没深度的变化规律.结果表明:随着淹没深度增大，结构振型未发生改变；但叶轮附加质量系数和阻尼比都呈线性增长趋势；完全淹没时，水体附加质量及阻尼比分别为空气中的0.39倍和1.76倍. 

Influence of Submerged Depths on the Modal Parameters of a Centrifugal Impeller

The vibration of the centrifugal impeller and its amplitude are affected by the added mass and damping of the surrounding water. In order to clarify the influence of different submerged depths on dynamic response characteristics of the centrifugal impeller, numerical and experimental studies were carried out. The modal analysis of the impeller under air and different submerged depth conditions were carried out based on coupled acoustic fluid-structure method. The response parameter of the impeller structure in air and in different submerged depth conditions were obtained through hammering method, and then the numerical prediction accuracy of natural frequency was evaluated. Based on simulation and experimental results, the variation laws of mode shape, added mass and damping ratio with different submerged depths were constructed. The results show that the mode shape does not change as the submerged depth increases. However, the added mass and damping coefficients of the impeller increase linearly with the increase of the relative submerged depth. If the impeller is fully submerged, the added mass and hydrodynamic damping ratio are 0.39 times and 1.76 times of those in air, respectively.