基于流固耦合的电站轴流风机叶轮动力特性研究

发布时间：2018-07-12 19:42

本文选题：轴流叶轮 + 流固耦合　；参考：《华北电力大学》2014年硕士论文

【摘要】：风机在国民经济的诸多领域都有十分广泛的应用，随着电站机组容量的不断增加，大机组采用多级动叶可调轴流式风机已经成为发展趋势。作为风机的核心部件，叶轮的强度不足会对风机运行产生一定的安全隐患，有可能引发疲劳破坏。在传统的风机强度计算中，对叶轮尤其是叶片的结构进行了大量的简化，导致较大的计算误差，不利于叶轮安全性的准确预估，采用有限元法能够很好地弥补这一不足。本文采用数值模拟技术，结合流固耦合分析方法，对电站两级动叶可调轴流风机叶轮进行了静态特性分析。分析结果表明，气动力对叶轮的静态特性有较大影响，考虑流固耦合作用后，气动力与离心力对叶轮的作用效果在一定程度上相互抵消，叶片表面等效应力分布情况发生变化，等效应力最大值减小，并且叶片变形趋势有较为显著的改变。对叶轮运行的安全性进行了预估，叶轮峰值等效应力远小于叶轮材料的许用应力90MPa，故该轴流风机的静强度符合要求。本文对轴流叶轮的动力特性进行了分析，分别计算了叶片、轮盘及叶轮的模态。施加预应力后叶片固有频率有一定程度的增长，其中离心力对振动频率的影响最大，并且转速越快，振动频率越大。对单扇区叶轮模型进行模态计算，得到了叶轮不同节径下的各阶振动频率，着重对叶轮1节径各阶模态进行了详细分析，第五阶与第六阶振动频率与监测得到的气动力主频率之间的频率余量约为9.4%，，小于频率余量的工程安全裕度，即气流激振力的主频率落入第五阶与第六阶模态的局部共振区域。叶轮共振的表现形式为叶片的局部振动，考虑到叶顶位置的等效应力值很小，远小于叶片材料的屈服极限，因此叶轮该区域不会发生疲劳破坏。
[Abstract]:Fan has been widely used in many fields of national economy. With the increasing capacity of power plant units, it has become a development trend for large units to adopt multi-stage movable vane adjustable axial flow fan. As the core component of fan, the strength of impeller will cause some safety hidden trouble to fan operation, which may lead to fatigue damage. In the traditional calculation of fan strength, the structure of impeller, especially blade, is simplified, which leads to a large calculation error, which is unfavorable to the accurate prediction of impeller safety. The finite element method can make up for this deficiency. In this paper, the static characteristics of two stage adjustable axial fan impeller of power station are analyzed by using numerical simulation technique and fluid-solid coupling analysis method. The results show that aerodynamic force has great influence on the static characteristics of impeller. Considering the fluid-solid coupling, the effect of aerodynamic force and centrifugal force on impeller is offset to a certain extent, and the distribution of equivalent stress on the blade surface changes. The maximum equivalent stress decreases and the deformation trend of the blade changes significantly. The safety of impeller operation is estimated. The equal effect force of impeller peak value is much less than the allowable stress of impeller material at 90 MPa, so the static strength of the axial fan meets the requirement. In this paper, the dynamic characteristics of axial impeller are analyzed, and the modes of blade, disk and impeller are calculated. The natural frequency of the blade increases to a certain extent after prestressing. The centrifugal force has the greatest influence on the vibration frequency, and the faster the speed is, the greater the vibration frequency is. The modal calculation of the single sector impeller model is carried out, and the vibration frequencies of the impeller with different nodal diameters are obtained, and the modes of the first pitch diameter of the impeller are analyzed in detail. The frequency margin between the fifth and sixth order vibration frequency and the monitored aerodynamic main frequency is about 9.4, which is less than the engineering safety margin of the frequency margin, that is, the main frequency of the airflow excitation force falls into the local resonance region of the fifth and sixth modes. The form of the impeller resonance is the local vibration of the blade. Considering that the equal effect force at the top of the blade is very small and is far less than the yield limit of the blade material, the impeller will not have fatigue failure in this region.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM62

【参考文献】