科氏力对高速旋转汽轮机叶片动态特性的影响

Effect of Coriolis Acceleration on Dynamic Characteristics of High Speed Spinning Steam Turbine Blades

采用解析的方法,建立了高速旋转汽轮机叶片中科氏力和科氏动应力的计算模型.该模型克服了以往在叶片动态特性分析时难以考虑科氏力影响的问题,导出了科氏动应力和非稳态气流动应力比值的计算公式以及科氏力和离心力比值的计算公式,并进行了实例分析.计算结果表明,科氏力对叶片轴向振动和扭转振动的固有频率没有影响,对切向振动的影响很小,可以忽略不计;科氏力所产生的动应力不到非稳态气流动应力的1%.

In order to study the effect of Coriolis acceleration on the natural frequency and dynamic stress of high spinning steam turbine blades, a computational model of Coriolis force and dynamic stress induced by Coriolis acceleration in blades is presented using analytic method. In the model, blades are modeled as continuous beam. The mathematic expression of the ratio of the maximum amplitude of dynamic stress from Coriolis force to the maximum amplitude of dynamic stress yielded by unsteady airflow force is derived. The ratio of the maximum amplitude of Coriolis force to centrifugal force is also derived. Finally, two sets of blades are analyzed using the model. The study shows the Coriolis force has no influence on axial and torsional vibration of spinning baldes, and the effect on tangential vibration is very small and can be neglected. The effect of Coriolis force on dynamic stress of blades of power plant steam turbines is less than one percent of the amplitude of the dynamic stress from unsteady airflow.