Foreign Object Damage to Fan Rotor Blades of Aeroengine Part II: Numerical Simulation of Bird Impact

Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carded out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.

Foreign Object Damage to Fan Rotor Blades of Aeroengine Part I:Experimental Study of Bird Impact

The conditions of experiment for bird impact to blades have been improved. The experiment of bird impact to the fan rotor blades of an aeroengine is carried out. Through analyzing the transient state response of blades impacted by bird and the change of blade profile before and after the impact, the anti-bird impact performance of blades in the first fan rotor is verified. The basis of anti-foreign object damage design for the fan rotor blades of an aeroengine is provided.

Aeroelastic prediction and analysis for a transonic fan rotor with the“hot”blade shape

This paper focuses on aeroelastic prediction and analysis for a transonic fan rotor with only its“hot”(running)blade shape available,which is often the case in practical engineering such as in the design stage.Based on an in-house and well-validated CFD solver and a hybrid structural finite element modeling/modal approach,three main aspects are considered with special emphasis on dealing with the“hot”blade shape.First,static aeroelastic analysis is presented for shape transformation between“cold”(manufacturing)and“hot”blades,and influence of the dynamic variation of“hot”shape on evaluated aerodynamic performance is investigated.Second,implementation of the energy method for flutter prediction is given and both a regularly used fixed“hot”shape and a variable“hot”shape are considered.Through comparison,influence of the dynamic variation of“hot”shape on evaluated aeroelastic stability is also investigated.Third,another common way to predict flutter,time-domain method,is used for the same concerned case,from which the predicted flutter characteristics are compared with those from the energy method.A well-publicized axial-flow transonic fan rotor,Rotor 67,is selected as a typical example,and the corresponding numerical results and discussions are presented in detail.

Numerical Investigation on Super-cooled Large Droplet Icing of Fan Rotor Blade in Jet Engine

Icing(or ice accretion) is a phenomenon in which super-cooled water droplets impinge and accrete on a body.It is well known that ice accretion on blades and vanes leads to performance degradation and has caused severe accidents.Although various anti-icing and deicing systems have been developed,such accidents still occur.Therefore,it is important to clarify the phenomenon of ice accretion on an aircraft and in a jet engine.However,flight tests for ice accretion are very expensive,and in the wind tunnel it is difficult to reproduce all climate conditions where ice accretion can occur.Therefore,it is expected that computational fluid dynamics(CFD),which can estimate ice accretion in various climate conditions,will be a useful way to predict and understand the ice accretion phenomenon.On the other hand,although the icing caused by super-cooled large droplets(SLD) is very dangerous,the numerical method has not been established yet.This is why SLD icing is characterized by splash and bounce phenomena of droplets and they are very complex in nature.In the present study,we develop an ice accretion code considering the splash and bounce phenomena to predict SLD icing,and the code is applied to a fan rotor blade.The numerical results with and without the SLD icing model are compared.Through this study,the influence of the SLD icing model is numerically clarified.

Modeling and Sliding Mode Control with Boundary Layer for Unmanned Coaxial Rotor Ducted Fan Helicopter

The structure and modeling of a novel unmanned coaxial rotor ducted fan helicopter(RDFH)are introduced,and then,based on the helicopter air dynamics and kinematics principles,a nonlinear model of the coaxial rotor ducted fan helicopter is developed and implemented on the basis of the wind tunnel experiment.After that,the helicopter′s stability and coupling characteristics of manipulation are analyzed through time-domain.Finally,a sliding mode controller(SMC)with boundary layers is developed on a hardware in the loop platform using digital signal processor(DSP)as the flight control computer.The results show that the RDFH′s tracking ability performs well under the use of proposed controller.

Internal Flow Condition between Front and Rear Rotor of Contra-Rotating Small-Sized Axial Fan at Low Flow Rate

Contra-rotating small-sized fans are used as cooling fans for electric equipment. The internal flow condition between the front and rear rotors of the contra-rotating small-sized fan is not known well especially at the low flow rate. Furthermore, the blade row distance between the front and rear rotors is an important parameter for the contra-rotating small-sized fan and its influence on the internal flow condition is not clarified at the low flow rate. Therefore, the internal flow condition of the contra-rotating small-sized fan at the low flow rate is investigated by the numerical analysis in this research. The numerical analysis results are validated by comparing the fan static pressure curves of the numerical results to the experimental results. The internal flow condition at the low flow rate is clarified using the numerical models of the different blade row distance L = 10 mm and 30 mm. In the present paper, pressure fluctuations phase locked each front and rear rotor’s rotation are shown and the influences of the wake and the potential interference are discussed by the unsteady numerical analysis results at the low flow rate.

An Attempt to Evaluate the Cycloidal Rotor Fan Performance

In this work, the cycloidal rotor fan (CRF) performance was estimated by means of a numerical method based on Unsteady Reynolds Averaged Navier-Stokes equations (URANS). The fan with a cycloidal rotor belongs to the positive displacement machines of the rotary type. The numerical algorithm for simulation of the flow in the cycloidal rotor as well as postprocessing of the CFD results was prepared using Ansys CFX CEL. The methodology for the assessment of the CRF performance was proposed and verified. It was found out that the CRF performance strongly depends on the shape of the profile of the applied rotor blade. The NACA 0012 and CLARK Y profiles were tested for the same CRF structure and flow conditions. Also, the crucial importance for the CRF performance has the range of the blade pitch angle change.

Effect of Hub-Ratio on Performance of Asymmetric Dual-Rotor Small Axial Fan

Currently, domestic and abroad scholars put more attention on contra-rotating dual-rotor axial fan. But there is less scholars study on asymmetric dual-rotor small axial fan, which is one of the contra-rotating dual-rotor axial fans. Like axial fan, many factors have influence on the performance of the asymmetric dual-rotor small axial flow fan, such as the wheel hub ratio, blade shape, blade number, stagger angle and the tip clearance. Because wheel hub ratio has great impact on the performance of the fan, we choose the size of wheel hub ratio as a variable factor to study the model change. There is a different wheel hub ratio between front stage impeller and rear stage of asymmetric dual-rotor small axial fan, so it is very beneficial to select the greater wind area that the fan area of external diameter minuses the area occupied by the blades and the hub as front stage impeller. In this paper, the hub-ratio of front stage impeller is 0.72, and that of rear stage is 0.72, 0.67 and 0.62 respectively along with the front stage impeller. Three kinds of models with different hub ratio of rear stage are simulated using the CFD software and the static characteristics are obtained. Based on the experimental test results, the internal flow field of the asymmetric dual-rotor small axial fan is analyzed in detail, the impact trends of different hub-ratio on the performance of asymmetric dual-rotor small axial fan are obtained and the argument of structure optimization for dual-rotor small axial fan is provided.

混合转子永磁电机双风道冷却系统设计

混合转子永磁电机具有高功率密度的优势,但也导致电机散热空间和散热能力不足等问题。为此,根据其特有的转子结构提出一种双风道冷却系统,并采用计算流体力学(Computational fluid dynamics,CFD)的方法对电机温度场进行验证。首先,根据电机损耗和尺寸设计一个适合双风道的轴流风扇。其次,对不同进、出风口的结构参数进行仿真,对比和分析仿真结果,选出冷却性能较好的参数组合。最后对单风道和该参数组合下的双风道进行数值模拟,仿真结果表明,使用双风道冷却结构后电机散热能力显著提升。

翼型加厚对桨扇性能的影响研究

为研究翼型加厚对桨扇性能的影响,通过两种不同的加厚方式对桨扇翼型进行加厚,采用NUMECA软件对加厚前后的对转桨扇进行三维流场数值模拟,对比加厚前后对转桨扇的性能变化。结果表明:在同一飞行状态下,无论是翼型整体加厚,还是只改变翼型最大厚度,对转桨扇的性能都会下降;相比于整体加厚,只改变最大厚度则性能下降得更多;在不同来流攻角条件下,攻角越大,加厚前后的对转桨扇性能差值越大。

离心风机的故障验证技术研究

针对离心风机开展了故障注入试验与数据分析研究,阐述了风机叶轮不平衡、转子不平衡和轴承断裂故障对振动数据的影响。研究特征值变化规律,提取出其中有效的故障信号,为离心风机在线监测奠定了基础,对离心风机的运行维护具有极其重要的意义。

转炉煤气离心风机转子动平衡修复技术要点

离心风机是一种高效、节能的气体输送设备,在钢铁企业广泛应用于各类煤气的加压和输送。由于转炉煤气介质含尘、含水量大,风机转子动平衡易遭其破坏,导致转炉煤气离心风机工况劣化,因此,掌握离心风机转子动平衡修复技术,可快速准确完成对转子动平衡修复,使其达到允许的平衡精度等级,将风机机械振动降至允许的范围内。介绍了转炉煤气离心风机悬臂式转子动平衡修复前、修复校正过程以及动平衡校正合格后的注意事项和技术要点,为提高动平衡修复效果和类似转子的动平衡修复提供借鉴经验。

宽弦空心风扇转子叶片鸟撞损伤数值仿真

为解决航空发动机宽弦空心风扇转子叶片抗鸟撞设计问题,对宽弦空心风扇转子叶片鸟撞损伤进行了数值仿真。采用光滑质点流体动力学(SPH)算法建立鸟体模型,采用J-C本构模型和失效模型定义材料冲击下动态性能,建立旋转状态下叶片鸟撞数值仿真方法,经过试验验证能够较准确预测叶片损伤。开展相同条件下鸟撞击宽弦空心和实心风扇转子叶片仿真,对比鸟撞击叶片过程、撞击时叶片叶尖最大轴向和径向变形、撞击后叶片永久变形,研究被鸟撞击后空心叶片相比实心叶片的损伤特征。结果表明:空心和实心叶片鸟撞击过程相同;空心叶片被鸟撞击后叶尖轴向和径向变形更小;空心叶片被鸟撞击后前缘卷边变形更严重,对风扇气动性能和稳定性影响更大;在结构设计时应适当增加前缘空心区域局部刚度,或者适当增大前缘实心区域范围,用于提高空心叶片的抗鸟撞能力。

FLADE带冠转子对超声速风扇性能影响分析及改进设计研究

风扇转子带冠可有效抑制弯掠叶片振动,但随着转子进口马赫数的不断提高,带冠结构对风扇流场及气动性能产生显著影响。本文基于叶尖风扇构型,选取某高负荷两级风扇为研究对象,结合单通道三维数值模拟,在设计转速工况下,分析了第2级转子带冠后对风扇工作特性的影响机理及规律,并探索了转子叶片积叠线和冠体型线优化对带冠转子性能的改善效果。计算结果表明:带冠转子所引起的进口相对马赫数变化,会引起叶顶端区流动恶化,出现大面积分离区域,导致风扇的稳定工作压比、效率和裕度都显著降低;带冠转子采用周向正弯的积叠线分布以及局部弯曲的冠体型线后,在设计转速各工况下有效抑制了叶顶端区分离流动,带冠转子工作性能相比于改进前得到明显改善,压比升高5.0%,效率提高1.6%,裕度提升5.3%。

浅谈离心风机安装技术要点

基于离心风机的构造特性和现场安装经验,详细探讨了影响风机安装品质的关键步骤,包括基础验收、轴承座调整、轴承安装、转子叶轮、主轴水平度、风机机壳、主轴密封、联轴器对中安装等环节。

通风机轴流式转子轮毂静力学分析及优化措施

轴流式通风机由于其结构紧凑、流量和压头适中而成为目前矿用主通风机主要选用的机型。为进一步探究通风机节能降耗的优化路径,该文以轴流式通风机转子和轮毂作为研究对象,重点分析转子和轮毂部位的静力学特征及可行性节能路径。通过有限元分析和数值计算后,确定转子和轮毂的中空区域可进行优化,并采用多孔材料焊接的方法进行优化。结果显示,优化后转子和轮毂中空区域的能耗显著降低,这表明此次优化达到了技术要求。

基于CFD的多级轴流风机动静干涉及激励特性研究

为了探究多级轴流风机的动静干涉及激励特性,分析每级叶轮不同相位排布对风机气动性能和流场激励的影响,对五级一体化轴流风机模型进行数值模拟。分别改变每级叶轮的相位排布角度为0°、2°、4°、6°,获得轴流风机内部流场和性能参数以及每级叶轮受力情况。结果表明:随着排布角度增大,叶轮对流体挤压增大,后半段流场流动恶化,效率约下降2.1%。每级叶轮受力的主要特征频率为叶频(fBPF)及其倍频,且幅值随频率增加而快速减小。同时,排布角度对每级叶轮受力的影响也体现在流场性能和流体能量上,越稳定的流场,其特征频率越集中且振幅较高。

Performance and Internal Flow of Contra-Rotating Small-Sized Cooling Fan

High pressure and large flow rate small-sized cooling fans are used for servers in data centers and there is a strong demand to increase its performance because of increase of quantity of heat from servers. Contra-rotating rotors have been adopted for some of high pressure and large flow rate cooling fans to meet the demand. The performance curve of the contra-rotating small-sized cooling fan with 40 mm square casing was investigated by an experimental apparatus and its internal flow condition was clarified by the numerical analysis. The fan static pressure of the front rotor was extremely low and it increased significantly at the rear rotor. The uniform flow was achieved at the inlet of the rear rotor because of the special shape of the casing between the front and rear rotors. On the other hand, the tip leakage flow was large enough to influence on the main flow of the test cooling fan by the design specification of high pressure with compact rotor diameter.

基于表面热膜测试的低速风扇附面层流动研究

压气机转子叶片表面附面层分离/再附、转捩机制较为复杂,数值模拟方法受到了极大的限制,因此需要新的试验技术测量旋转状态下转子叶片表面附面层的发展状态。本文采用表面热膜测试技术对某风扇叶片表面附面层分离/再附、转捩等流动现象进行了试验研究,获得了旋转状态下风扇叶片表面的准壁面剪切应力。试验结果表明,在上游尾迹周期性扫掠的作用下,叶片表面附面层转捩、再附点提前,分离泡范围减小。表面热膜测试技术可较为准确地捕捉旋转叶片表面附面层的转捩、再附点,为旋转状态下转子表面附面层的流动测量提供了一种解决途径。

跨声速串列转子气动耦合机制分析及优化设计

串列叶片可以突破常规压气机气动负荷的限制,具有良好的工程应用前景。但跨声速串列转子通道内激波系结构复杂,控制难度较大,导致气动效率偏低。为解决上述问题,利用数值模拟的方法对比了串列转子前排在串列和单转子条件下气动参数、流场的变化规律,分析了跨声速串列转子前/后排气动耦合机理,并完成了优化设计。结果表明:(1)串列条件下,前排落后角、总压比沿叶高分布规律发生变化,槽道正激波显著增强,是导致跨声速串列转子效率水平低下的根本原因;(2)针对跨声速串列叶型的优化可以实现流场的定制设计,优化后前/后排匹配工作状态及激波结构显著改善;(3)优化后的串列转子失速裕度提升约6%、设计点等熵效率提升约1.5%,证明了本文提出的优化设计思路及方法的有效性。