压缩机多级叶轮转子系统的静动强度及气动载荷研究

发布时间：2018-06-02 19:18

本文选题：离心式压缩机 + 转子系统　；参考：《东北大学》2012年硕士论文

【摘要】：转子系统是离心压缩机的核心部件,其性能的好坏对整个压缩机安全可靠运行至关重要。离心压缩机转子系统的强度校核和可靠性计算越来越受到重视,已经成为压缩机设计中的重要一环。但传统上,研究人员只注重转子系统离心载荷的计算,对气动载荷的重视程度明显不足。随着化工行业的快速发展,离心压缩机进口流量不断增大,气动激振力对转子系统的影响也越来越大,其对转子系统强度的削弱作用日趋明显。因此,在对转子系统进行结构分析的过程中,单纯的由离心力导致的静应力分析已不能满足可靠性要求。本文依托973课题的研究背景,以制氧系统中的离心压缩机为研究对象,借助有限元方法和CFD数值模拟技术研究离心压缩机转子系统性能,分析了转子系统的关键零件的静强度和动强度,计算出转子系统叶轮内部气体的流动规律,近而分析出压缩机工作过程中的气动载荷对系统的影响。主要完成如下几个研究内容。 (1)利用大型有限元分析软件ANSYS分别对半开式和闭式离心压缩机计算,得出了叶片的前六阶固有频率。分别对叶轮和叶片的静强度和动强度特性进行了分析。通过分析发现：在给定模型中,无论是半开式离心压缩机叶轮,还是闭式离心压缩机叶轮,其叶片的动强度设计比较合理,可靠性很高。而叶轮由于自振频率比较低,容易与高频激振力发生倍频共振,因此,建议修改导叶个数改变激振力频率或者通过其他措施改变叶轮的固有频率,使高频激振力频率与叶轮固有频率的倍频满足15%的避开率,以免叶轮出现倍频共振,发生屈服性破坏。 (2)通过CFD软件分别对半开式、闭式叶轮流场进行模拟计算与性能预测,分别计算出半开式、闭式叶轮和叶片不同工作情况下的受力、变形及流场分布情况,为后续计算和分析整个转子系统气动载荷做必要准备。分别讨论了叶片只受气动载荷、只受离心力载荷、同时受气动载荷和离心力载荷三种载荷情况。计算结果表明：叶片的应力分布和总体变形趋势在三种情况下是相似的；半开式叶轮流场的最大气流速度出现在流场入口处和出口处,而非中间部位,整体上呈现从入口到出口逐渐增大趋势,并且流场平均速度随着气体质量流速率的增大而增大。对于闭式叶轮,在叶轮转速不变的情况下,增加气体质量流率,叶轮内部流场边界压力随之增加；叶轮气体质量流率不变,增大叶轮转速,叶轮内部流场边界压力基本不变；另外,流场边界压力呈现由入口向出口逐渐增大的规律。 (3)对离心压缩机的低压转子系统主轴进行了模态分析,计算了前六阶固有频率；对整个转子系统不同工作情况下的气动载荷进行仿真分析,计算出转子系统在不同气动载荷作用下受力和变形情况,分析了气动载荷对转子系统的影响。通过分析发现：气动载荷下转子系统主轴的应力和变形都比较小,表明气动载荷对主轴或轴承造成伤害不是气动载荷产生的绝对应力和变形值引起的,而是气动载荷的交变作用造成主轴或轴承的疲劳破坏。
[Abstract]:The rotor system is the core component of the centrifugal compressor. Its performance is very important for the safe and reliable operation of the compressor. The strength checking and reliability calculation of the rotor system of the centrifugal compressor have been paid more and more attention, and it has become an important part of the compressor design. However, the researchers have traditionally paid attention to the centrifugal load of the rotor system. With the rapid development of the chemical industry, the inlet flow of the centrifugal compressor is increasing, and the effect of the aerodynamic force on the rotor system is becoming more and more, and its effect on the strength of the rotor system becomes more and more obvious. So, in the process of structural analysis of the rotor system, the simple The static stress analysis caused by centrifugal force can no longer meet the reliability requirements.
Based on the research background of the 973 subject, this paper takes the centrifugal compressor in the oxygen making system as the research object. Using the finite element method and the CFD numerical simulation technology to study the performance of the rotor system of the centrifugal compressor, the static strength and the dynamic strength of the key parts of the rotor system are analyzed, and the flow law of the internal gas in the impeller of the rotor system is calculated. The influence of the aerodynamic load on the system during the working process of the compressor is separated. The following research contents are mainly completed.
(1) using the large finite element analysis software ANSYS to calculate the semi open and closed centrifugal compressors respectively, the first six order natural frequencies of the blades are obtained. The static strength and dynamic strength characteristics of the impeller and blade are analyzed respectively. The analysis shows that in the given model, the impeller of the semi open centrifugal compressor and the closed centrifugal centrifugal compressor are found in the given model. The dynamic strength of the compressor impeller is reasonable and the reliability is very high, and the impeller is easily resonate with the high frequency excitation force because of the low frequency of self vibration. Therefore, it is suggested to modify the number of the guide vane to change the frequency of the exciting force or to change the inherent frequency of the impeller through other measures, so that the frequency of the high frequency excitation force and the inherent frequency of the impeller can be changed. The frequency doubling of the rate satisfies the avoidance rate of 15%, so as to avoid the frequency doubling resonance and yielding failure of the impeller.
(2) through the CFD software, the simulation calculation and performance prediction of the semi open and closed impeller flow field are carried out respectively. The force, deformation and flow field distribution of the semi open, closed impeller and blade are calculated respectively, and the necessary preparation for the subsequent calculation and analysis of the aerodynamic load of the whole rotor system is made. The load is only subjected to the centrifugal load, and it is subjected to three loads of the aerodynamic load and the centrifugal force. The calculation results show that the stress distribution and the overall deformation trend of the blade are similar in three cases. The maximum airflow velocity of the semi open impeller flow field appears at the entrance and exit of the flow field, not the middle part. The entrance to exit is gradually increasing, and the average velocity of the flow field increases with the increase of gas mass flow rate. For the closed impeller, the flow boundary pressure in the impeller increases with the increase of the gas mass flow rate when the impeller speed is constant, and the mass flow rate of the impeller is constant, the impeller speed is increased, and the flow field inside the impeller is on the edge. The boundary pressure basically remains unchanged, and the boundary pressure of the flow field increases gradually from the inlet to the outlet.
(3) the modal analysis of the spindle of the low pressure rotor system of the centrifugal compressor is carried out and the first six natural frequencies are calculated. The aerodynamic load of the whole rotor system under different working conditions is simulated and analyzed. The force and deformation of the rotor system under different aerodynamic loads are calculated, and the influence of the aerodynamic load on the rotor system is analyzed. Through the analysis, it is found that the stress and deformation of the spindle of the rotor system are relatively small, which indicates that the damage caused by the aerodynamic load on the spindle or bearing is not caused by the absolute stress and deformation value produced by the aerodynamic load, but the fatigue damage of the spindle or bearing caused by the alternating action of the aerodynamic load.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH45

【参考文献】