Time-dependent Vibration Frequency Reliability Analysis of Blade Vibration of Compressor Wheel of Turbocharger for Vehicle Application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application. The existing models for evaluating the reliability of blade vibration of compressor wheel are static, and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter. For the blade vibration failure mode of compressor wheel of turbocharger, the reliability evaluation method is studied. Taking a compressor wheel of turbocharger for vehicle application as an example, the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed. The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram, and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account, time-dependent reliability models of compressor wheel with blade vibration failure mode are derived, which embody the parameters of blade natural vibration frequency, turbocharger operating speed, the blade number of compressor wheel, life index and minimum number of resonance, etc. Finally, the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented. A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Study of modeling unsteady blade row interaction in a transonic compressor stage part 2:influence of deterministic correlations on time-averaged flow prediction

The average-passage equation system （APES） provides a rigorous mathematical framework for account- ing for the unsteady blade row interaction through multistage compressors in steady state environment by introducing de- terministic correlations （DC） that need to be modeled to close the equation system. The primary purpose of this study was to provide insight into the DC characteristics and the in- fluence of DC on the time-averaged flow field of the APES. In Part 2 of this two-part paper, the influence of DC on the time-averaged flow field was systematically studied; Several time-averaging computations boundary conditions and DC were conducted with various for the downstream stator in a transonic compressor stage, by employing the CFD solver developed in Part 1 of this two-part paper. These results were compared with the time-averaged unsteady flow field and the steady one. The study indicat;d that the circumferential- averaged DC can take into account major part of the unsteady effects on spanwise redistribution of flow fields in compres- sors. Furthermore, it demonstrated that both deterministic stresses and deterministic enthalpy fluxes are necessary to reproduce the time-averaged flow field.

Study of modeling unsteady blade row interaction in a transonic compressor stage part 1:code development and deterministic correlation analysis

The average-passage equation system （APES） provides a rigorous mathematical framework for account- ing for the unsteady blade row interaction through multi- stage compressors in steady state environment by introduc- ing deterministic correlations （DC） that need to be modeled to close the equation system. The primary purpose of this study is to provide insight into the DC characteristics and the influence of DC on the time-averaged flow field of the APES. In Part 1 of this two-part paper, firstly a 3D viscous unsteady and time-averaging flow CFD solver is developed to investi- gate the APES technique. Then steady and unsteady simu- lations are conducted in a transonic compressor stage. The results from both simulations are compared to highlight the significance of the unsteady interactions. Furthermore, the distribution characteristics of DC are studied and the DC at the rotor/stator interface are compared with their spatial cor- relations （SC）. Lastly, steady and time-averaging （employing APES with DC） simulations for the downstream stator alone are conducted employing DC derived from the unsteady re- suits. The results from steady and time-averaging simula- tions are compared with the time-averaged unsteady results. The comparisons demonstrate that the simulation employing APES with DC can reproduce the time-averaged field and the 3D viscous time-averaging flow solver is validated.

Vibration reliability analysis for aeroengine compressor blade based on support vector machine response surface method

To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.

Investigation of Microstructure of Fine Grain Cast IN718 Compressor Blade from Abroad

Fine grain cast IN718 compressor blade form abroad has been analyzed. There is no columnar grain, uniform equiaxed grain, less segregation and no porosity cast defect in essence in the section of blade body with fine grain, in which grain size is about ASTM 2 ～4. Its microstructure is approachable to that of forging. It is hopeful to achieve the goal of replacing forging by casting.

Nonlinear Pre⁃deformation Method for Compressor Rotor Blade

A cold compressor blade deforms elastically under aerodynamic and centrifugal loads during operation,transforming into a hot blade configuration.Blade deformation has a significant effect on the performance of compressor.A nonlinear pre⁃deformation method for compressor rotor blade was developed with consideration of the nonlinear features of blade stiffness and load which varies with blade configuration.In the blade profile design phase,the method can be used to compensate the aeroelastic deformation of the blade during operation.The adverse effects of blade deflection on compressor performance and structure can be avoided by the pre⁃deformation method.Due to the fact that the nonlinear method is sensitive to initial value,a load incremental method was applied to calculate initial blade deformation to stabilize and accelerate the pre⁃deformation method.The developed method was used to predict the manufactured configuration of the Stage 37 rotor blade.The variation rules of aerodynamic and structure parameters of the pre⁃deformed blade were analyzed under off⁃design conditions.Results show that the developed method ensures that under the design condition there was a good match between the actual blade configuration during operation and the intended design blade profile.The blade untwist angle of pre⁃deformed blade could be 0°at design point.Meanwhile,the tip clearance only decreased 0.2%.When the working speed was faster than 80%design speed,the performance of the pre⁃deformed blade agreed with that of the design blade.However,the mass flow rate and the total pressure ratio of the pre⁃deformed blade were lower at low speeds.

Vibration Modal Analysis of Compressor Blade based on ANSYS

Compressor is an important part of aero engine. In the environment of high temperature and high pressure,compressor blade will suffer from several physical and chemical processes,such as centrifugal force,aerodynamic force vibration and oxidation. These processes will lead compressor blade to fatigue fracture,and at the same time,make negative effects on the engine’ s overall performance. Based on the software ANSYS15. 0,we made strength analysis and modal analysis of compressor blade in this paper. As a result,we got its natural frequencies,relevant modal parameters and vibration mode cloud pictures. After analyzing the influence that centrifugal force made on modal parameters,we predicted the expected damage of the blade. Eventually the analysis results will provide the basis for overall performance evaluation,structural crack detection,fatigue life estimation and strength calculation of aircraft engine compressor.

考虑叶片造型的压气机流动稳定性模型研究进展

压气机实际稳定裕度是否达到指标直接决定了发动机是否可以投入使用.目前的压气机气动设计体系中缺乏一种高效、准确的评估失稳边界的工具,导致在设计定型后依然存在实际稳定裕度不足的风险.因此迫切需要发展快速可靠的压气机稳定性预测工具以供设计阶段使用.现代航空压气机叶片的气动设计朝着三维精细化方向发展,如何在设计阶段考虑叶片三维造型的变化对稳定性的影响愈发关键.传统的激盘/半激盘模型难以精细捕捉到三维叶片造型对流动稳定性的影响,而非定常数值模拟方法对计算资源的消耗在压气机设计阶段难以承受.为了在精细考虑叶片造型影响的同时提高计算效率,为气动设计阶段提供稳定性评估工具,本团队首先在2013年提出了叶轮机流动稳定性通用理论,通过分布式叶片力源项建模考虑复杂叶片造型的影响,通过系统特征值描述流动稳定性.继而针对不同的预测目标和应用条件,发展了3种简化模型:子午面模型、流线模型和径向展开模型.其中子午面模型能够准确刻画叶尖间隙、叶片掠和叶片加载方式等关键设计参数对流动稳定性的影响,为设计阶段提供了一种可靠的失稳边界预测工具;流线模型可以快速评估展向各条流线系统的流动稳定性,并定量地给出流动稳定性最为薄弱的区域,从而有针对性地指导叶片扩稳设计;径向展开模型可以快速地预测离心压气机的流动失稳点,定量评估离心压气机流动稳定性.以上模型可以应用于压气机气动设计体系,为设计定型的压气机提供了可靠的稳定性评估方法,为压气机气动/稳定性一体化设计提供了技术储备.

基于运营数据的发动机压气机叶片裂纹扩展规律研究

为研究航空发动机实际服役中转子叶片在复杂载荷作用下的裂纹损伤扩展规律,基于航空发动机运营数据构建叶片的裂纹扩展寿命曲线,同时采用断裂力学理论建立裂纹扩展速率公式。以高压压气机叶片为实例,通过流固耦合方法构建压气机叶片结构的载荷模型,分别采用Paris、Walker、Newman裂纹扩展速率公式对压气机叶尖区域进行三维裂纹扩展分析。仿真结果表明,三种裂纹扩展速率公式在裂纹扩展前期预测结果与发动机运营数据裂纹扩展曲线具有一致性,可较好地描述叶片裂纹扩展规律;在裂纹稳定扩展阶段,Walker和Newman公式预测结果相对危险,Paris公式预测结果吻合度较高,并且能与厂家技术手册中关于其损伤发展控制要求相互印证。

双级可转导叶压气机性能研究

压气机的稳定性是保证压气机其他性能及燃气轮机正常运行的基础,而压气机存在着失速、喘振等不稳定现象,这种不稳定流动会严重影响整机运行的稳定性。导叶/静叶可调是一种防止喘振从而避免压气机进入失稳流动的有效措施。该文介绍了一个集成式压气机实验台,除了可进行高精度可转导叶性能研究外,还可进行压气机不同叶片综合性能和局部特性实验测量工作,且其数据采集集成系统可满足实时准确观测实验台相关参数的需求。通过实验与数值模拟相结合的方法对2.5级轴流压气机进行了研究,通过逐级调节进口导叶和一级静叶的旋转角度,获得了叶片调节角度与压气机效率之间的对应关系。

压气机叶片的磨削路径生成算法

针对当前航空发动机压气机叶片的打磨过程繁琐且路径生成算法普遍未适配压气机叶片的几何形貌和加工姿态等问题,提出一种基于压气机叶片的点云数据并自适应压气机叶片的加工姿态和形貌的磨削路径生成算法。以面结构光扫描获取叶片的3维点云信息,对叶片点云进行位姿矫正并在叶片待加工区域创建一系列间距适宜且相互平行的切平面进行切片处理,获取切片数据后计算切平面与叶片点云的交点,拟合所有切片所得交点并计算磨削抛光路径的路径点及刀具姿态。结果表明:通过计算对不同姿态下不同压气机叶片的路径信息进行了仿真,验证了所提出的算法具有自适应压气机叶片加工姿态和形貌的特性,避开了传统逆向工程中的曲面重构误差,证明了算法的可行性与有效性,可进一步应用于后续实际磨削抛光加工作业。

叶片破损对压气机性能的影响

为了研究叶片破损对压气机内部流场的影响机理,本文针对带有破损的跨音速压气机叶片进行气动性能变化规律和机理研究。通过NASA rotor 37实验结果验证了计算方法的准确性,利用数值仿真研究了叶片破损对压气性能的影响规律,并对2种典型工况下叶片破损前后的流场结构进行对比分析,探讨引起性能变化的具体原因。研究表明:叶片破损会导致压气机的压比降低0.6631%、绝热效率降低0.7877%,且压气机的稳定裕度降低更为明显。叶尖破损主要对叶顶流场结构产生影响,使叶顶区域泄漏流增强,当其与激波相互作用时,通道内产生了流动堵塞和流动损失。本文研究成果可为实际服役中的航空发动机特性评定提供理论参考。

基于CCD的激光熔覆熔池平滑度在线监测系统研究

由于激光熔覆过程高温高亮,无法实时准确判断熔覆效果。使用CCD相机结合平滑度监测算法,对不同功率下的熔池形貌进行监测,验证算法性能,判断熔覆效果,同时尝试叶片修复。结果表明:激光功率过大或者扫描速度过慢,均会导致熔池边缘平滑度较差,进而认为熔覆参数不合适;为防止熔坏基材,可根据监测效果及时停机;发现激光功率与熔池边缘平滑度呈负相关。

压气机内部旋转不稳定的研究综述

旋转不稳定是压气机工作在高负荷近失速工况时的一种常见现象。研究旋转不稳定在降低压气机工作噪声、减小流致振动以及保障航空发动机稳定工作等方面具有重要意义。首先对旋转不稳定现象进行了回顾,详细讨论了旋转不稳定的特征。其次,重点调研了旋转不稳定的起源和机理,将旋转不稳定产生的原因归纳为叶尖泄漏流、涡脱落以及流动剪切等类别。此外,回顾了模拟旋转不稳定的数值方法,讨论了多种流动控制手段对旋转不稳定的作用效果。最后,对旋转不稳定的研究现状进行了总结,对未来的研究趋势进行了展望。

基于流固耦合的压气机转子叶片非同步振动分析

压气机转子叶片非同步振动是近年来发现的一类新气动弹性问题,表现为叶片振动频率与转频不同步且具有锁频现象,严重影响航空发动机的可靠性和运行安全,目前对其产生机理并不完全清楚.为了深入研究压气机内不稳定流动与叶片非同步振动之间的耦合机制,基于时间推进的方法建立了多级压气机转子叶片全环的双向流固耦合模型,数值研究了刚性叶片与非同步振动柔性叶片的非定常流场、气流激励频率和结构响应特征,揭示了压气机转子叶片非同步振动的流固耦合机制.结果表明:近失速工况下,转子叶尖吸力面径向分离涡的周期性脱落及再附过程是导致叶尖压力剧烈波动的主要原因,其3倍谐波激励频率与转子一阶弯曲固有频率接近,提供了叶片非同步振动的初始气流激励源.叶片非同步振动发生时,位移响应表现为等幅值的极限环特征,振动以一阶弯曲模态主导,径向分离涡产生的非整数倍气流激励频率及其谐波频率最终锁定为叶片一阶弯曲固有频率,非同步振动的运动胁迫使得相邻通道叶尖流场周向趋于一致.研究成果及对叶片非同步振动流固耦合机制的认识可为压气机内部不稳定流动诱发的叶片振动失效分析提供有益参考.

涡喷压气机叶片精密铸造工艺探究

叶片精密铸造是熔模精密铸造技术在叶片制造中的应用。本文对涡喷压气机叶片精密铸造工艺进行研究,利用SolidWorks软件建立三维模型,对压气机叶片进行充型凝固数值模拟,并总结出一套合适的铸造工艺。

基于自适应带宽核密度估计的压气机叶片加工误差统计分析方法

针对压气机叶片的加工误差统计分析建模问题,本文提出了一种自适应带宽的非参数核密度估计方法,实现了压气机叶片加工误差的概率密度建模。首先,基于拇指法则求解固定带宽核密度估计中的固定最优带宽作为起始带宽。然后,在固定最优带宽的基础上引入灵敏因子构建了自适应带宽函数,并通过自适应带宽函数对核密度估计进行调控。在此基础上,以核密度估计的精度均方差(MSE)与灵敏度S为目标函数,采用精英策略遗传算法对灵敏因子进行优化获得最优灵敏因子。进而计算出不同数据样本点对应的最优带宽,使得带宽能够根据数据样本疏密程度进行自适应调整。最后,对134组机械加工叶片的叶型截面的6种叶型误差进行统计建模,并采用交叉检验法验证了自适应带宽核密度估计的泛化性能。实验结果表明该方法的适用性好精度高,且拟合优度均在0.9以上,同时避免了传统固定带宽核密度估计的局部适应性问题。本文所提出的统计分析方法能够准确获得现有工艺能力下压气机叶片加工误差的分布特性,为叶片气动设计优化改进提供了一种有效手段。

压气机叶片激光熔化沉积修复的机器人路径自动规划和试验研究

针对航空发动机TC17高压压气机叶片服役损伤后的修复问题,本文基于工业机器人的激光熔化沉积路径生成策略,提出使用模型布尔运算来分析叶片损伤区域,并在RobotStudio离线编程软件中嵌入二次开发插件分别生成Zigzag轴向扫描、中心线偏移扫描和边缘螺旋扫描路径。路径的仿真和沉积形貌分析表明,在设定扫描速度5 mm/s、沉积层厚度0.3 mm、搭接率50%时,中心线偏移扫描在95.97%时间内保持速度稳定,折返点处的速度下降幅度更小,同时沉积后表面高度接近0.3 mm,高度波动方差更小,保持了较高的平整度。此外,矩形平板区域的沉积模拟和试验表明,类似Zigzag扫描的连续路径可以显著降低成形表面的残余应力。

雾滴冷却对压气机边界层分离流动的影响研究

采用欧拉-拉格朗日坐标系对喷雾减温过程进行数值研究,研究喷雾条件下NASA stage 35的流场特性,以及雾滴冷却对边界层分离的影响,探究对边界层分离产生的黏性损失。结果表明,喷雾冷却使流场进口质量流量增加和温度降低。雾滴的蒸发使流体组份发生变化,流场的运动黏度增加,导致边界层分离延迟和边界层厚度变薄。在干空气条件下边界层在25%弦长发生分离。喷雾使边界层移动至29%弦长发生分离。尽管雾滴冷却下边界层分离产生的黏性损失增大,但是边界层分离延迟和变薄对叶型损失起主导作用,喷雾冷却工况下叶型损失减小3.68%。

叶片变形对涡轮增压器用离心压气机气动性能的影响及机理

为了研究叶片变形对涡轮增压器用离心压气机气动性能的影响,采用流固耦合方法计算设计转速下近喘振点、最高效率点和近阻塞点三个工况处的压气机性能。研究结果表明:叶片变形主要受离心载荷的影响,其影响占比为92.11%~97.22%,叶片最大变形发生在主叶片前缘叶顶处,叶轮最大应力发生在叶轮轴孔底部;从近阻塞点到近喘振点,气动载荷引起的叶片变形不断增大,约占叶片总变形的2.78%~7.89%;变形后压气机效率和压比分别提高0.3%和0.06%,阻塞流量有所减小;发现气动载荷导致的变形方向与离心载荷导致的变形方向相反,叶片变形主要通过改变叶顶间隙来影响离心压气机的气动性能。研究成果为离心压缩机气动及预变形设计优化提供了参考依据。