叶片圆盘泵叶轮结构流固耦合模态特性分析

为探究流体压力、离心力对叶片圆盘泵叶轮结构模态特性的影响,采用Fluent软件计算泵叶轮不同工况下流体压力大小及分布情况,借助Workbench平台进行叶轮结构的静态模态以及流体压力和旋转离心力作用下的模态特性分析,并对结果进行对比分析。同时,探讨了连接臂半径及位置对叶轮固有频率的影响。结果表明:叶轮的静态模态与预应力模态各阶振型基本相似,固有频率及振幅差异也不大;随着连接臂半径的增大,泵叶轮固有频率逐渐增大;随着连接臂与圆盘盖板中心之间距离变大,叶轮前三阶固有频率逐渐变小,总体上差别不大,三阶及以后各阶固有频率逐渐变大。     

叶片圆盘泵叶轮结构流固耦合模态特性分析

为探究流体压力、离心力对叶片圆盘泵叶轮结构模态特性的影响,采用Fluent软件计算泵叶轮不同工况下流体压力大小及分布情况,借助Workbench平台进行叶轮结构的静态模态以及流体压力和旋转离心力作用下的模态特性分析,并对结果进行对比分析。同时,探讨了连接臂半径及位置对叶轮固有频率的影响。结果表明:叶轮的静态模态与预应力模态各阶振型基本相似,固有频率及振幅差异也不大;随着连接臂半径的增大,泵叶轮固有频率逐渐增大;随着连接臂与圆盘盖板中心之间距离变大,叶轮前三阶固有频率逐渐变小,总体上差别不大,三阶及以后各阶固有频率逐渐变大。     

基于特征值灵敏度修改的叶轮结构改进设计

在应用Ansys软件进行叶轮模态计算时，确定叶轮的结构尺寸是建立实体的重要步骤。在引入特征值灵敏度修改理论，给定第一阶固有频率修改数值的条件下，对叶轮的刚度进行了修改。确定出关键尺寸后，对叶轮进行了有限元计算和实验模态分析；比较了二者结果和分析了误差并最终给出了符合设计要求的定型叶轮。     

涡轮增压器叶片振动分析

为了控制某种型号涡轮增压器的压气机进气口存在的振动及噪声等问题，先通过三维坐标仪进行测量，然后用CAD软件进行三维建模，并利用有限元软件对涡轮和叶轮大小叶片进行了模态分析，得到了叶片的各阶固有频率以及相应振型。对比增压器的工作转速和叶轮与涡轮叶片旋转通过频率，找出了叶片共振的频率，从而为有效地控制压气机进气口振动及噪声大等问题提供了理论依据。     

几何参数对离心叶轮强度和气动性能影响的研究

使用有限元计算软件和内部流场计算软件对所设计的几个具有不同几何尺寸的离心压气机叶轮的强度和气动性能进行了计算。结果表明反弯叶片可降低叶轮出口处叶片根部附近的应力,但会造成叶片根部前缘区域应力集中,且反弯叶轮的气动性能和原型叶轮差别不大。前倾叶片能在很大程度上降低叶轮出口处叶片根部应力,前倾角越大出口叶根处应力减小越多;随前倾角增大,叶轮气动性能恶化程度加剧;叶轮的背盘形状对叶轮的应力影响较大,尤其是出口处的背盘厚度对出口处叶片根部区域的应力起主因作用。研究得出叶片几何及背盘形状因素对叶轮应力分布的影响规律,另外还得到了叶片几何形状对气动性能的影响规律,这些工作为叶轮的多学科优化设计提供良好的基础。     

采用逆向工程技术对叶轮建模的研究

在引进、消化、吸收国外先进设备的过程中,当设备中一些型面特别复杂的零件难以用测绘的方法表示其结构和尺寸时,可以用逆向工程技术对零件进行复制。整体式斜流叶轮广泛应用在微型燃气轮机等的压气机部件中。叶轮叶片的设计、制造技术直接影响压气机机组的运行性能和可靠性,对压气机起着关键性的作用。主要研究利用逆向工程技术来实现某微型燃气轮机中整体式斜流叶轮的测量、再设计。探索采用PMM-C700三坐标测量机,利用叶片的叶盆边界和叶背边界作为扫描测量边界,进行扫描叶轮叶片表面的方法,实现了叶轮零件的数字化测量。提出叶轮叶片扫描数据处理的有效方法。实现了叶轮叶片的曲面重构。应用UGNX2软件对叶轮叶片的点云数据进行曲面重构,完成了基于UGNX2的叶轮零件建模。     

用背叶片平衡多级离心泵轴向力的试验研究

设计了多级多出口离心泵轴向力测试装置,对泵的轴向力进行测试.通过改变叶轮背叶片尺寸,研究叶轮背叶片尺寸对泵轴向力的影响.     

离心压缩机叶轮冲蚀磨损的动力特性研究

为研究固粒冲蚀磨损对离心压缩机叶轮动力学特性和结构强度的影响,建立磨损损伤的叶轮的三维模型,并采用有限元方法,对有无离心预应力状态下原始叶轮和损伤叶轮的固有频率和振型进行提取,对叶轮共振特性进行研究,对因材料流失而造成的叶片强度、刚度变化进行了分析。研究结果表明:因冲蚀磨损引起的叶片局部减薄对叶轮整体振动特性影响不明显;叶轮在工作转速下其第6,7阶共振裕度较小;冲蚀磨损损伤的叶片存在应力集中和刚度降低的现象。     

考虑预应力时风扇叶片模态特征分析

简要论述了模态分析的基本理论,建立了风扇叶片的有限元模型,通过对该模型进行模态分析,得到了叶片的固有频率和相应的模态振型,并分析了各阶振型下叶片的振动情况。考虑叶片旋转工作状态下离心力会产生预应力的影响,通过加载旋转力矩,求解了预应力下叶片的固有频率。利用不同转速下叶轮旋转对叶片激振频率的计算,同该状态下有限元计算所得的固有频率比较,分析了叶片的共振特性。     

某离心压缩机首级叶轮叶片断裂事故分析与改进研究

本文研究了某离心压缩机首级叶轮叶片断裂事故。分析了该叶片发生断裂的原因,发现该事故主要是由于叶轮固有频率与进口导叶尾迹频率接近发生共振引起的。在此分析基础上,提出了以下改进措施：一方面通过增加叶片厚度来改变叶轮固有频率,以避开进口导叶尾迹频率;另一方面,同时通过叶片进口处沿轴向切除14.4mm,以减小进口导叶尾流激振力。到目前为止,改进后的叶轮现场运行情况良好。     

两自由度悬臂梁压电发电装置的宽频发电性能

研究一种两自由度悬臂梁压电发电装置,以提高悬臂梁式压电发电装置在环境振源振动频率波动情况下的发电能力。建立了两自由度悬臂梁压电发电装置的频率特性理论模型,并对该理论模型进行了有限元仿真验证,结果显示理论计算与有限元仿真结果基本一致。对两自由度悬臂梁压电发电装置的频率特性模型进行了数值模拟,模拟显示:装置的前两阶模态频率比随着长度比、宽度比、厚度比及质量块的质量比的增大均出现一个最小值,且在长度比为0.8,宽度比为2.0,厚度比为1.0,质量块的质量比为0.5时,装置的前两阶模态频率比最小,结果表明通过合理设计两自由度悬臂梁压电发电装置的结构参数,可以使得装置的前两阶模态频率最接近。最后,实例设计了两自由度悬臂梁压电发电装置,并进行了试验测试,证实了优化后的两自由度悬臂梁压电发电装置具有宽频带发电能力。     

离心式风机含裂纹叶片的试验模态分析

针对离心式风机含裂纹叶片振动特性,搭建了风机在自由悬挂状态下的试验模态分析平台,分别在无裂纹和不同裂纹深度等8种情况下对叶片固有频率及模态振型进行了试验研究。经试验研究与数据分析得:离心式风机叶轮结构固有频率随裂纹深度的增加而单调下降;裂纹越深,固有频率下降越快。该结论为风机叶片故障监测与诊断提供了基础。     

离心压缩机叶片前缘形状对强度计算的影响

以某大型离心式压缩机的闭式叶轮为研究对象,在研究叶片前缘形状对叶轮性能的影响过程中,利用CAD软件Solidworks对3个闭式叶轮进行三维实体造型,并运用有限元软件ANSYS进行数值模拟计算.主要对比研究了钝形、圆形和椭圆形前缘对叶轮强度的影响.数值计算的结果表明:叶片前缘几何形状对离心压缩机的结构强度具有影响.     

Influence of blade thickness on transient flow characteristics of centrifugal slurry pump with semi-open impeller

As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeller blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.

     

对旋轴流局部通风机叶片断裂原因分析与改进

通过建立有限元分析模型,对矿用对旋轴流式局部通风机叶轮进行应力、变形分析,分析出大机型叶片断裂的主要原因是叶轮结构与尺寸不合理,叶轮高速旋转时叶片根部的应力过大、安全系数过低.据此提出在叶片根部局部增加厚度的方法解决了该问题.同时,还对叶轮结构进行改进,减少了材料消耗,提高整机性能.样机试验及现场应用表明,改进后通风机叶轮的机械强度和刚度满足要求,叶轮质量减小20.8％,噪声降低2.31 dB,振动速度有效值降低1.5 mm/s,全压效率略有提高,稳定运行区域更广.该分析方法在同类产品中有应用的可能性.     

Modal characteristics and fatigue strength of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. The modal characteristics and endurance strength of a 5 MW gas turbine engine blade developed by Doosan Heavy Industries & Construction Co., Ltd. in HCF fracture were verified through analysis and tests to determine the reliability of the compressor blade. A compressor blade design procedure that considers HCF life was performed in the following order: airfoil and blade profile design, modal analysis, stress distribution test, stress endurance limit test, and fatigue life verification. This study analyzed the Campbell diagram and estimated resonance risk on the basis of the natural frequency analysis and modal test of the compressor blade to guarantee safe and operational reliability. In addition, the maximum stress point of the compressor blade was determined through stress distribution analysis and test. The bonding point of the strain gage was determined by using fatigue test. Stress endurance limit test was performed based on the results of these tests. This research compared and verified the modal characteristics and endurance strengths of the compressor blades to prevent HCF fracture, which is among the major causes of gas turbine engine damage. A fatigue life design procedure of compressor blades was established. The 5 MW class gas turbine compressor blade is well designed in terms of resonance stability and fatigue endurance limit.     

COMPARISON OF TWO METHODS TO INCREASE TIP CLEARANCE AND ITS EFFECT ON PERFORMANCE OF TURBOCHARGER CENTRIFUGAL COMPRESSOR STAGE

Tip clearance between the blade tip and casing of a centrifugal compressor can be varied through two methods:by changing the blade height(M1)or by changing the casing diameter(M2). Numerical simulations are carried out to compare these two methods and their effect on the stage and impeller performance.The impeller and diffuser are connected through rotor stator boundary using frozen rotor approach.Overall stage performance and the flow configuration have been investigated for nine tip clearance levels from no gap to 1 mm.Impeller and diffuser performances are also pre- sented separately.It has been found that the overall and impeller performance are comparatively better for M1 below tip clearance of 0.5 mm whereas M2 is found advantageous above 0.5 mm of tip clear- ance.Both M1 and M2 show performance degradation with the increase in tip clearance.Two models have been proposed for the stage total pressure ratio and efficiency,which are found to be in agree- ment with experimental results.The impeller efficiency and the pressure ratio are found to be maxi- mum at tip clearance of 0.1 mm for both the cases however minimum diffuser effectiveness is also observed at the same clearance level.Diffuser effectiveness is found to be maximum at zero gap for both cases.As it is practically impossible to have zero gap for unshrouded impellers so it is concluded that the optimum thickness is 0.5 mm onwards for M1 and 0.5 mm for M2 in terms of diffuser effec- tiveness.Mass averaged flow parameters,entropy,blade loading diagram and relative pressure fields are presented,showing the loss production within the impeller passage with tip clearance.