Review on Stress Corrosion and Corrosion Fatigue Failure of Centrifugal Compressor Impeller

Corrosion failure,especially stress corrosion cracking and corrosion fatigue,is the main cause of centrifugal compressor impeller failure.And it is concealed and destructive.This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments,and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution（AD）,the hydrogen-induced cracking（HIC）,and the combined AD and HIC mechanisms.The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking.The effects of stress ratio,loading frequency,and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized.The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments,which contain sulfide,chlorides,and carbonate,are analyzed.The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments.The current research methods for centrifugal compressor impeller corrosion failure are analyzed.Physical analysis,numerical simulation,and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.

Method for Evaluating the Reliability of Compressor Impeller of Turbocharger for Vehicle Application in Plateau Area

As turbocharging diesel engines for vehicle application are applied in plateau area, the environmental adaptability of engines has drawn more attention. For the environmental adaptability problem of turbocharging diesel engines for vehicle application, the present studies almost focus on the optimization of performance match between turbocharger and engine, and the reliability problem of turbocharger is almost ignored. The reliability problem of compressor impeller of turhocharger for vehicle application when diesel engines operate in plateau area is studied. Firstly, the rule that the rotational speed of turbocharger changes with the altitude height is presented, and the potential failure modes of compressor impeller are analyzed. Then, the failure behavior models of compressor impeller are built, and the reliability models of compressor impeller operating in plateau area are developed. Finally, the rule that the reliability of compressor impeller changes with the altitude height is studied, the measurements for improving the reliability of the compressor impellers of turbocharger operating in plateau area are given. The results indicate that when the operating speed of diesel engine is certain, the rotational speed of turbocharger increases with the increase of altitude height, and the failure risk of compressor impeller with the failure modes of hub fatigue and blade resonance increases. The reliability of compressor impeller decreases with the increase of altitude height, and it also decreases as the increase of number of the mission profile cycle of engine. The method proposed can not only be used to evaluating the reliability of compressor impeller when diesel engines operate in plateau area but also be applied to direct the structural optimization of compressor impeller.

Investigation into the Interaction of Centrifugal Compressor Impeller and Vaneless Diffuser

Centrifugal compressors with parallel-wall and contracting wall vaneless diffuser are designed by using centrifugal compressor computer-aided integrated design system. The internal flow fields of the compressor are calculated by solving three-dimensional Navier-Stokes equation. Four aspects are investigated and calculation results show that the total efficiencies and total pressure ratios of the compressor with contracting wall vandess diffuser is higher than that of the compressor with parallel-wall. The jet and wake don＇t mix rapidly inside vandess diffuser. The outlet blade lean angle doesn＇t affect the compressor performance. The greater the mass flow rate through impeller, the more uneven the velocity distribution at impeller outlet is.

Study of Secondary Flow Modifications at Impeller Exit of a Centrifugal Compressor

A computational study has been conducted to analyze the performance of a centrifugal compressor under various levels of impeller-diffuser interactions. The study has been conducted using a low solidity vaned diffuser (LSVD), a conventional vaned diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using Reynolds-Averaged Navier- Stokes simulations. A commercial software ANSYS CFX is used for this purpose. The extent of diffuser influence on impeller flow is studied by keeping the diffuser vane leading edge at three different radial locations. Detailed flow analysis inside the impeller passage shows that the strength and location of the wake region at the exit of impeller blade is heavily depended upon the tip leakage flow and the pressure equalization flow. Above design flow rate, the diffuser vane affects only the last twenty percent of the impeller flow. However, below design flow rate, keeping vane closer to the impeller can cause an early stall within the impeller. Small negative incidence angle at the diffuser vane is helpful in order to reduce the losses at the impeller exit.

OPTIMIZATION DESIGN OF CENTRIFUGAL IMPELLER WITH SPLIT BLADES

An automatic aerodynamic optimization design system for centrifugal compressor impellers is developed. The system utilizes the combined optimization of blade profiles and meridional geometries. In the construction of objective functions, non-design point performances are considered to realize the performance optimization in whole work ranges of the impeller. An impeller with one row of split blades is redesigned using the proposed optimization system. Results show that for the optimal impeller, the efficiency is obviously improved in the whole mass flow ranges, while the total pressure ratio hardly varies.

两级液环压缩机内流场及外特性

采用数值模拟与试验相结合的方法,以2SY-6两级液环压缩机为研究对象,对多级液环压缩机在不同工况、不同叶轮宽度比下内流场及性能进行对比分析,结果表明:二级叶轮叶片载荷小于一级叶轮,其排气口区域锯齿形气液交界面较一级叶轮更为光滑.一级叶轮吸气口区域回流强度相对于二级叶轮吸气口区域更强,一级叶轮吸气口区域湍动能明显大于二级叶轮.等外径设计的二级叶轮进出口压缩比远小于一级叶轮,二级叶轮的做功能力小于一级叶轮.由于一级叶轮的进出口压缩比较大且均位于效率极值点的右侧,一级叶轮效率随泵的压缩比增大而逐渐下降,而二级叶轮压缩比范围包含极值点,所以其效率先增后减.液环压缩机随着二级叶轮宽度的增大,其吸气能力越强,各个工况下的流量均逐渐增大.低压缩比工况下的效率随k值减小逐渐增大,高压缩比工况下的效率随k值减小先增后减.随首次级叶轮宽度比k值的减小,二级叶轮的压缩比曲线逐渐向上平移,而一级叶轮的压缩比曲线逐渐向下平移.随泵出口压力的增大,首次级叶轮压缩比的比值曲线下降趋于平缓,k值为2.2时两级叶轮压缩比的比值趋于1.1.

整机环境下离心压气机叶轮流固耦合不确定性量化分析

针对流固耦合不确定性量化计算中精度和成本难以有效平衡的问题,从某涡轮增压器离心压气机双向流固耦合计算出发,提出了考虑叶片热态变形和蜗壳非对称影响的离心压气机内流场计算简化模型,并结合集成代理模型和蒙特卡罗方法,开展了整机环境下离心压气机叶轮流固耦合的不确定性量化分析。数值结果表明:在保证计算精度的前提下,相较于整机流固耦合模型,提出的简化模型将计算时间缩短了83%~98%;材料属性不确定性对叶轮效率的影响大于转速不确定性,密度、泊松比和弹性模量3种不确定性因素对叶轮效率的影响程度相当,转速对叶片热态变形不确定性的影响程度在转速不确定性中最为显著;叶片热态变形不确定性对叶轮效率的影响主要体现在效率均值的变化,而与热态变形无关的转速自身、叶轮出口非对称流场等不确定性因素对叶轮效率的影响主要体现在分散度的变化。研究工作突显了流固耦合分析在离心压气机不确定性量化分析中的必要性,为今后开展鲁棒优化设计提供了理论基础。

基于可调叶高扩压器的离心压气机构型流动机理研究

离心叶轮/扩压器匹配关系恶化直接限制了离心压气机的稳定工作范围.以Radiver离心压气机为研究对象,借助经过校核的数值模拟方法开展了基于可调叶高扩压器的离心压气机叶轮/扩压器匹配关系及流动机理研究.结果表明:通过建立能够指导扩压器叶高调节方向和量值的“压气机工作流量-扩压器最佳叶高”正相关对应关系,即可在压气机近失稳点等小流量点主动降低扩压器叶高以改善压气机稳定工作裕度.在设计转速下,引入可调叶高扩压器能够使离心压气机的稳定裕度提升18.8%、流量范围拓宽385%且峰值效率提高0.45%;随着压气机工作点向小流量工况偏移,降低扩压器叶高可以抑制扩压器来流正攻角,优化重构其通道内部涡系结构,减小扩压器吸力面和压力面/轮毂角区的低速区,进而改善叶轮/扩压器匹配关系,抑制扩压器内部流动失稳发生,提升离心压气机稳定裕度和效率指标.

小排量国Ⅵ柴油机涡轮增压器喘振优化设计

匹配某小排量国Ⅵ柴油机时,增压器压气机出现了喘振现象,导致发动机扭矩明显降低,需要设计一款新型压气机。通过加大压气机叶片θ角、叶片出口β角、叶片弦长、叶轮进口尺寸、叶轮出口宽度,减小扩压器出口与叶轮出口直径的比值,设计了优化方案。进行了优化方案和原方案的压气机性能仿真计算、增压器台架压气机性能试验、发动机台架增压器性能匹配试验,结果表明:优化方案改善了压气机小流量区域的稳定性,提高了堵塞流量;在发动机全转速范围内,流量减小时压比特性曲线斜率始终为负,压气机运行稳定,未发生喘振;发动机可以加载到最大设计扭矩,提升了发动机的动力性能。

管道离心式压缩机叶轮的流固耦合数值模拟及可靠性评估

离心式压缩机是天然气长输管道的核心设备,其叶轮在长期承受交变载荷的情况下可能出现疲劳失效。针对管道压缩机的叶轮全流道进行几何建模,基于实际运行参数开展流场计算及固体应力场有限元分析,在叶轮静力分析基础上加载气动载荷实现流固耦合计算,以此获得运行状态下的叶轮应力分布。基于模拟结果并结合叶轮材料特性,首先建立了叶轮疲劳寿命计算模型,进一步采用极大似然估计法估计了三参数威布尔分布的参数(η=1.001 9,β=536.88,γ=-0.900 1),以考虑叶轮疲劳寿命的不确定性,最后利用蒙特卡洛方法计算得到叶轮疲劳寿命的概率分布以及可靠性曲线。结果表明,在额定运行工况下,压缩机叶轮的循环次数达1010次后,其可靠度仍维持在90%以上,处于无限疲劳寿命状态。利用不同应力幅值下的叶轮运行可靠性曲线,实现了管道压气站不同工况下离心压缩机叶轮的寿命预测。

天然气管道压缩机叶轮冲蚀磨损数值计算及优化

为了研究天然气管道压缩机叶轮磨损问题,揭示压缩机允许安全运行的颗粒物类型及其粒径,识别影响磨损严重程度的条件,基于ANSYS CFX软件中的Tabakoff和Grant的侵蚀模型,对压缩机内部流场进行了气固两相流数值模拟,着重开展了不同固体颗粒粒径对叶轮叶片冲蚀的数值模拟计算。模拟计算结果表明,粒径越大,对叶轮叶片冲蚀磨损越严重;当颗粒粒径保持不变时,颗粒密度越高,对叶轮叶片的摩擦力也就越强。根据模拟计算结果对叶片厚度进行了优化,兼顾了叶轮气动性能和耐冲刷的能力。研究成果对天然气管道压缩机乃至管道系统的安全稳定运行具有现实指导意义。

进口和国产离心式氯气压缩机转子的比较

离心式氯气压缩机是氯碱厂最核心的动设备,用来压缩和输送氯气,而转子是离心式氯气压缩机的核心部件。从结构和组装等方面对进口和国产离心式氯气压缩机的转子进行了比较,为国内氯气压缩机生产企业优化转子提供参考。

浅析空压机高压缸振动异常波动原因

分析空压机组高压缸的运行情况,排查机组异常波动的原因,对各个因素逐一论证,确认引起高压缸振动异常波动的原因是段间冷却器的腐蚀物及涂抹的二硫化钼润滑脂被携带至叶轮而导致叶轮结垢。通过计算高压缸各段多变效率评判了出现异常波动之后机组的稳定性和可靠性,并对机组各段间冷却器进行改造,通过更换管板和管束材质后,机组运行工况大大改善,为装置长周期运行提供参考依据。

带泄漏通道的半开式离心叶轮轴向力推力数值模拟分析

离心叶轮轴向力的计算是大型、高速离心压缩机设计的关键技术之一。本文以某0.17流量系数离心压缩机半开式叶轮为研究对象,采用数值模拟的方法对该叶轮在设计工况、变工况和变关键几何尺寸条件下的轴向力展开了计算和模拟分析。结果表明:半开式离心叶轮轴向力一维计算方法与本文所采用的数值模拟方法相比,两者误差为5.8%;轴向力随流量的增加呈现先增加后减小的趋势;当叶轮的转速增加时,叶轮轴向力在全流量范围内增加;当进气温度增加时,轴向力呈现线性下降趋势;当进气压力增加时,轴向力呈现线性增长趋势;当密封齿数增加时,叶轮轴向力线性增大,泄漏量逐渐减小。当密封轴颈增加时,叶轮轴向力先减小至平衡状态后再反向继续增加,泄漏量成倍数增长趋势。

基于多岛遗传算法的离心压缩机叶轮结构优化研究

为保证离心压缩机的稳定运行,以水利工程离心压缩机使用的叶片钢叶轮为例,提出基于多岛遗传算法的离心压缩机叶轮结构优化方法.采用三阶Bezier曲线对叶轮叶片的进出口安放角以及叶片包角等参数进行设计;利用CFD软件构建叶轮的计算域以及模型,对叶轮结构模型进行相关条件假设和处理后,完成模型计算;定义重量最轻、扬程最大、水利效率最高为叶轮结构优化目标函数,结合等效应力、轴向变形约束条件,通过多岛遗传算法优化叶轮结构参数.试验结果满足叶轮结构优化的约束条件.

微型涡喷发动机离心压气机叶轮强度分析

发动机旋转部件的强度分析是微型涡喷发动机设计过程中的重要组成部分,具有足够的结构强度是发动机正常稳定运行的保证。首先介绍了微型涡喷发动机离心压气机的国内外研究现状,并以KJ66涡喷发动机的离心压气机叶轮为例,分析了其结构组成及特点,并基于SolidWorks软件建立了离心压气机叶轮的三维模型;然后利用有限元软件ANSYS Workbench建立了有限元模型并进行了力学仿真研究。通过对离心压气机叶轮力学强度的模拟分析,为离心压气机叶轮结构进一步优化设计提供了一定的理论参考。

Design and Key Technology of Oil-Free Centrifugal Air Compressor for Hydrogen Fuel Cell

For a 120 kW hydrogen fuel cell system,a centrifugal air compressor with fixed power of 22 kW fuel cell is designed.Firstly,the theoretical calculation is carried out for the aerodynamic characteristics of a ultra-high-speed permanent magnet synchronous motor,an air compressor,and an aerodynamic foil bearing.Then,a prototype is trial-produced and a related test bench is built for test verification.Finally,both the simulation and test results indicate that the designed centrifugal air compressor meets the overall requirements of the hydrogen fuel cell system,and the relevant conclusions provide both theoretical and experimental references for the subsequent series development and design of the centrifugal air compressor.

Shape Optimization of a Modified Centrifugal Compressor Using the Adjoint Method

Centrifugal compressors can realize a high pressure ratio within a relatively small spatial space,therefore largely used in aviation impeller machinery.Pursuing less size and weight while no penalty of efficiency and aerodynamic loading is the development trend,while both the complex geometry and tough flow conditions bring challenges on the flow calculation and aerodynamic shape optimization.Considering the Adjoint method is an efficient local optimization algorithm,this paper uses the continuous Adjoint method to optimize the geometry of a modified Krain impeller.The results show that the isentropic efficient is improved 0.53%point at near peak-efficiency operating condition,while the mass flow rate and total pressure ratio keep relatively constant.Besides,the whole characteristic line shows a positive improvement,indicating the significance of theAdjoint optimization method.

多轴式离心压缩机损坏原因分析

本文针对多轴式离心压缩机因振动跳车,初次检查后设备二次启动发生叶轮叶片断裂事件。对压缩机进行解体,检查各级零部件的状态,通过对断口进行宏观和微观分析,找出根本原因是叶轮原材料中含有杂质金(Au)元素,同时压缩机运行过程中气流对叶片产生的机械疲劳共同作用,使得叶片发生断裂。在设备启动后,因叶片脱落导致转子平衡破坏,振动升高,造成叶轮与蜗壳摩擦后压缩机损坏。

仿鸮翼离心压缩机叶轮的参数优化及性能研究

受高效飞行鸟类翼型结构启发,尝试采用叶轮仿鸮翼设计结合子午流道型线参数优化设计提高离心压缩机的气动性能。首先,提取具有优良气动性能的长耳鸮翅膀展向40%截面处翼型进行仿生逆向重构,基于鸮翼厚度分布特征进行离心压缩机叶轮的仿生设计;然后,采用拉丁超立方抽样、BP神经网络拟合、遗传算法寻优对叶轮叶顶侧子午流道型线进行参数优化,并对优化设计前后的离心压缩机气动性能及其流动特性进行数值分析。结果表明:采用提出的叶轮仿生设计耦合子午流道参数优化方法,离心压缩机内部流场得到改善,气动性能得到提升。设计工况下,优化后的离心压缩机多变效率提高了3.16%,压比提升了2.61%;叶轮内部及叶片扩压器出口的高熵区域缩小,流动分离得到有效抑制,同时叶片表面载荷增大且分布更加均匀,叶轮做功能力增强。