Fatigue Life Estimation for an Aircraft Engine Fan Blade

In this paper,stress states under corresponding condition of an aero-engine fan blade using finite element stress-strain analysis for three work cycles in the 900 h load spectrum are obtained.Through the nominal stress method,we calculated the fatigue notch factor and combined the material characteristics of TC6 to correct the material curve to the fan blades curve. Finally,the fatigue life of a fan blade was estimated using the linear cumulative damage rule and nonlinear cumulative damage theory.

NON-DIMENSIONAL DESIGN PARAMETERS FOR FOD TOLERANT FAN BLADES

Non-dimensional design concept for FOD tolerant fan blades is introduced based on the analyses of simplified impact models. The fan blades arc idealized as either beams or plates of elastic or rigid-plastic materials. The case of constant force impact as well as that of mass impact is analyzed. The centrifugal force effects are also considered in the beam models. The critical fracture conditions arc shown in simple npn-dimensional formulae or diagrams for each case.

Numerical Study on the Duct Noise Control of Single-Stage Axial Flow Fan with Wave Leading Edge Stator Blade Configurations

This study focuses on a single-stage axial flow fan, investigating the effect of three kinds of wave leading edge stator blades on its noise reduction. The DDES method and the duct acoustic analogy theory based on the penetrable data surface were used for noise prediction. The results showed that the three kinds of wave leading edge blades were effective in reducing the rotor-stator interaction tonal noise and also have a certain inhibitory effect on broadband noise. The A10W15 stator blade can effectively reduce broadband noise in the frequency range of 2200 - 4200 Hz. When the amplitude is increased to 20, the noise reduction effect is further enhanced. However, when the amplitude is increased to 30, the broadband noise reduction effect is no longer significant. Further research shows that the wave leading edge stator blades can significantly change the pressure fluctuation distribution on the leading edge and suction surface, which control the modal energy distribution. Finally, this paper analyzed multiple factors affecting the broadband noise reduction, such as the noise source cut-off and cut-on effect and correlation. The purpose of this paper is to explore the laws of the influence of wave leading edge blades on the duct noise of real fan, and to reveal its noise control mechanism. .

Internal structural optimization of hollow fan blade based on sequential quadratic programming algorithm

Several structural design parameters for the description of the geometric features of a hollow fan blade were determined.A structural design optimization model of a hollow fan blade which based on the strength constraint and minimum mass was established based on the finite element method through these parameters.Then,the sequential quadratic programming algorithm was employed to search the optimal solutions.Several groups of value for initial design variables were chosen,for the purpose of not only finding much more local optimal results but also analyzing which discipline that the variables according to could be benefit for the convergence and robustness.Response surface method and Monte Carlo simulations were used to analyze whether the objective function and constraint function are sensitive to the variation of variables or not.Then the robust results could be found among a group of different local optimal solutions.

Three-dimensional modeling and reconstructive change of residual stress during machining process of milling, polishing, heat treatment, vibratory finishing, and shot peening of fan blade

Residual stress during the machining process has always been a research hotspot,especially for aero-engine blades.The three-dimensional modeling and reconstructive laws of residual stress among various processes in the machining process of the fan blade is studied in this paper.The fan blades of Ti-6Al-4V are targeted for milling,polishing,heat treatment,vibratory finishing,and shot peening.The surface and subsurface residual stress after each process is measured by the X-ray diffraction method.The distribution of the surface and subsurface residual stress is analyzed.The Rational Taylor surface function and cosine decay function are used to fit the characteristic function of the residual stress distribution,and the empirical formula with high fitting accuracy is obtained.The value and distribution of surface and subsurface residual stress vary greatly due to different processing techniques.The reconstructive change of the surface and subsurface residual stress of the blade in each process intuitively shows the change of the residual stress between the processes,which has a high reference significance for the research on the residual stress of the blade processing and the optimization of the entire blade process.

Numerical simulation of a UAV impacting engine fan blades

A 3D digital model of a small Unmanned Aerial Vehicle(UAV)is obtained by using the method of scanning reverse modeling and joint mapping.A numerical simulation of a small UAV strikes on rotary engine blades,presented in this paper,was performed with a Transient Nonlinear Finite Element code PAM-CRASH software.A test of motor strike on plate was developed and the dynamic response of the plate were obtained to validate the numerical simulation method of a UAV strike on blades.Based on this,dynamic damage response caused by UAV on the engine blades were studied.It is indicated that the impact process between the UAV and a single blade can be divided into two typical stages:cutting and impact.Cutting mainly leads to the failure of the leading edge material,and impact mainly leads to the plastic deformation of the blade.At the same time,it is compared with the damage impacted by bird with the same mass.For the same mass of bird and UAV,the damage caused by UAV striking fan blade is more serious,and 1.345 kg UAV striking fan blade of typical civil aviation engine is enough to cause damage to flight safety.

Influence Factors for Impact Actions and Transient Trajectories of Fan Blades after Fan Blade Out in Typical 2-Shaft High Bypass Ratio Turbofan Engine

To enhance the understanding of design characters, which have prominent influences during the fan blade out event, a simplified geometrical and dynamic analysis method was derived, and a typical 2-shaft high bypass ratio turbofan engine was selected and modeled. Based on analytical deriving and engineering experience learned from the real engine failure case, three determinative impact actions were recognized from the fan blade out process. The transient trajectories of these impact actions were researched in analytical method, and then thickness of acoustic lining, quantity of fan blades and threshold load of structural fuse were analyzed as key design characters. 36 serialized fan blade out transient dynamic simulations were conducted by using the 2-shaft high bypass ratio turbofan engine model within different combinations of the three key design factors. The results from geometrical and dynamic analysis matched mainly well with the results from simulations. Characteristic phenomenon in simulation can be explained theoretically. Five conclusions can be summarized from these results. (1) If thickness fan acoustic lining was thinner, the deviation between simplified analytical calculation and simulation were not outstanding to predict Blade-Casing the first impact time and angular position. (2) An appropriate thickness of acoustic lining could make a lower impact stress of fan casing at the first impact. (3) Different thickness of acoustic linings leaded to two impact modes for blade 2, which were tip impact and root impact. (4) Different impact conditions between blade 1 and blade 2 caused remarkable speed components distinction of blade 1, and leaded to a wide range of transient trajectory of blade 1 during FBO event. (5) Thicker acoustic lining in this research can usually find the porper threshold loads setting, which can give a satisfactory outbound vibration. Two details were raised for further research, which were impact behavior of composite material fan blade and honeycomb and influences of wider FBO threshold load ranges in design cases with thinner acoustic lining.

Parametric study on the flutter sensitivity of a wide-chord hollow fan blade

In recent years, the hollow fan blades have been widely used to meet the demand for light weight and good performance of the aero-engine. However, the relationship between the hollow structure and the aeroelastic stability has not been studied yet in the open literature. In this paper,it has been investigated for an H-shaped hollow fan blade. Before studying the flutter behavior, the methods of parametric modeling and auto-generation of Finite Element Model(FEM) are presented. The influence of the feature parameters on the vibration frequency and mode shape(as the input of flutter calculation) of the first three modes are analyzed by the Orthogonal Experimental Design(OED) method. The results show that the parameters have a more remarkable impact on the first torsional mode and thus it is concerned in the flutter sensitivity analysis. Compared with the solid blade, the minimum aerodynamic damping of the hollow blade decreases, indicating that the hollow structure makes the aeroelastic stability worse. For the parameters describing the hollow section, the rib number N has the greatest influence on the minimum aerodynamic damping, followed by the wall thickness W5. For the parameters in the height of hollow segment, the aerodynamic damping increases with the increase of parameters M1 and M2. This means that reducing the height of the hollow segment is helpful to improve the aeroelastic stability. Compared with the impact of parameters in hollow section, the variation of aerodynamic damping caused by the height of the hollow segment is small.

Motion Characteristic Analysis of a Parallel Mechanism with 2-DOF for Industrial Fan Blades' Scribing

Abstract：With the application background of 16 inch industrial fan blades＇ scribing process, a simple and prac tical 2DOF parallel plane scribing device is proposed to replace the traditional manual scribing. The direct and inverse kinematics solutions, workspace and singular configuration of the mechanism are analyzed and solved. Some contour curve equations are fitted based on the data points which are measured by a three coordinate meas uring machine. According to the blade＇s contour curve, each input link＇s motion characteristic is obtained by u sing MATLAB, which provides a new way to realize blades＇ automatic scribing process technology.

Numerical Simulation of Axial Inflow Characteristics and Aerodynamic Noise in a Large-Scale Adjustable-Blade Fan

Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from−12°to 12°.In such a range the maximum static(gauge)pressure at the inlet changes from−2280 Pa to 382 Pa,and the minimum static pressure decreases from−3389 Pa to−8000 Pa.As for the axial intermediate flow surface,one low pressure zone is located at the junction of the suction surface and the hub,another is located at the suction surface close to the casing position.At the outlet boundary,the low pressure is negative and decreases from−1716 Pa to−4589 Pa.The sound pressure level of the inlet and outlet noise tends to increase monotonously by 11.6 dB and 7.3 dB,respectively.The acoustic energy of discrete noise is always higher than that of broadband noise regardless of whether the inlet or outlet flow surfaces are considered.The acoustic energy ratio of discrete noise at the inlet tends to increase from 0.78 to 0.93,while at the outlet it first decreases from 0.79 to 0.73 and then increases to 0.84.

Effects of circumferential configuration concerning splitter blade on the aerodynamic performance in a transonic axial fan

For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential distributions concerning the splitter cascades upon the aerodynamic performance were investigated. The studies show that the optimum splitter cascade is not very close to the suction side of main blade. The load between the main blade and the splitter blade can be soundly distributed in terms of the adjustment of circumferential position of the splitter blade. The best aerodynamic performance can be successfully obtained according to the optimum shape of the expanding fluid channel reasonably formed by the splitter blade and the main blade.

Effect of Tip-Blade Cutting on the Performance of Large Scale Axial Fan

The effect of tip-blade cutting on the performance of a large scale axial fan was investigated using computational fluid dynamics(CFD)methods.Experiments verified the numerical simulations.The original fan was compared with the one with tip-cutting in terms of dimensionless characteristic and aerodynamic performance in tip region under the conditions of the maximum efficiency point and near-stall point.The results showed that double leakage flow occurred in tip clearance at maximum efficiency point and spillage of leakage flow from leading edge occurred in tip-blade region at near-stall point for the both two fans;and that tip-cutting with 6% of blade height could reduce the intensity of tip-leakage vortex and increase flow capacity in tip blade region,and hold the stall margin almost the same as the original fan.The maximum efficiency of the fan with tip-cutting was improved by1%,and the ability of total pressure rising was obviously greater than the original fan.

Numerical Study on Internal Flow of Small Axial Flow Fan with Splitter Blades

The splitter blades are widely used in axial compressors and play an active role in the improvement of the overall performance of compressors. However, little research on the application of splitter blades to small axial flow fans is conducted. This paper designs a splitter blade small axial flow fan (model B) with a small axial flow fan as the prototype fan (model A) by adding short blades at the second half part of the passageway among long blades of model A. The steady simulation for the two models was conducted with the help of RNG k-ε turbulence model provided by software Fluent, and static characteristics and internal flow characteristics of the two models were compared and analyzed. Results show that splitter blades can improve the unsteady flow in the small flow rate region and also have a positive role to increase static pressure rise and efficiency in the higher flow rate region. The variation of static pressure gradient on the meridian plane in model B is well-distributed. The static pressure on the blade surface of model B distributes more uniformly. Splitter blades can suppress the secondary flow from pressure side to suction side in the leading edge because the pressure difference between suction side and pressure side in model B is generally lower than that of model A. And it also can restrain the vortex shedding and flow separation, and further it may be able to get the aerodynamic noise lower because static pressure gradient on the blade surface is well-distributed and the vortex shedding is not developed. Therefore, the performance of the fan with splitter blades is better than that of the prototype fan. The findings of this paper can be a basis for the design of high performance small axial flow fans.

多翼离心风机蜗壳气动性能与出风均匀性优化设计

以某型号风暖浴霸吹风系统的多翼离心风机为研究对象,利用ANSYS Fluent 2020 R2对原型风机的出口风量与均匀度进行仿真分析,结果显示仿真与实测误差在5%以内,验证了用CFD数值模拟方法来优化浴霸多翼离心风机的可靠性.将蜗壳型线参数化,通过正交试验设计,针对蜗舌放置角α、蜗舌半径R、等角螺线常数A(蜗壳周向面积)与风轮移动距离L(蜗舌与叶轮间隙)4个因素,制定了16组参数组合方案并进行了CFD数值模拟,得到各方案的出口风量与均匀度,并由均值与极差分析确定了最优参数组合.通过数值计算结果可知,优化后的风机在蜗舌附近区域湍流强度减小,内部流动改善.测试结果显示,优化后的风机出口风量提升7.3%,均匀度提升4.5%,全压效率提升5.9%.显著提升了风暖浴霸离心风机的出风性能和出口风速分布均匀性,对提高风暖浴霸取暖效率和增强人体舒适性有重要意义.

风机叶片新型耐磨超疏水涂层的防覆冰性能研究

风力发电机叶片在服役过程中经常会受到覆冰影响,超疏水材料由于其特殊的湿润性,在防冰领域具有较大的应用潜力。基于此,以风力发电机叶片为基底,在其表面旋涂由环氧树脂(EP)、聚二甲基硅氧烷(PDMS)和改性的SiO2等配制的无氟悬浮液,固化后制得耐磨防冰的超疏水试样。采用扫描电镜、红外光谱仪和接触角测量仪分别对超疏水涂层的微观形貌、成分组成和疏水性能进行研究。结果表明:超疏水涂层的接触角为166.65°,滚动角为2.5°。相比于无涂层风机叶片,涂层在-10℃和-15℃延长结冰时间40%左右,并且涂层结冰后冰层的粘结强度明显小于风机叶片的。涂层在800目砂纸上磨损10 m后接触角为150.5°。制备的耐磨超疏水涂层具有超疏水效果和良好的防冰性能。

涵道风扇部件耦合设计方法及初步应用

涵道风扇是未来绿色航空动力的重要发展方向,快速、准确的涵道风扇设计方法成为工程领域的迫切需求。在传统的涵道风扇设计方法中,部件间的耦合效应需要建立在完善的三维数值计算或试验数据的基础之上。而本文发展了考虑涵道风扇关键部件耦合效应的设计方法,形成了涵道风扇一体化设计手段,并以此为基础开展了涵道风扇的一体化设计及验证工作。结果表明:相比于简单叠加设计方法,耦合设计使叶片推力设计误差由15%减小到3.5%;采用部件耦合方法设计的带有扩张喷管涵道风扇和等直径喷管涵道风扇的转静叶片推力设计误差满足工程需求,确认了部件耦合的设计方法正确传递了部件间的影响关系;通过试验对设计结果进行了推力校验,试验结果与设计点的总推力误差为1.25%,证明了本文发展的耦合设计方法的准确性。

航空发动机鸟撞适航符合性数值模拟研究

航空发动机鸟撞适航认证通常基于整机试验,整机鸟撞数值仿真,受发动机结构复杂性影响,存在计算效率、吸鸟关键参数不易确定等问题,而不被工程采纳。而为验证航空发动机吸鸟符合性,进行整机鸟撞数值分析是一种经济高效的方式。基于航空发动机整机鸟撞数值仿真需求,开展航空发动机模型简化建模和关键吸鸟参数提取方法研究。首先,基于光滑流体动力学方法,考虑工作条件下发动机鸟撞损伤和传力路径上关键部件关系和相互作用,建立了基于航空发动机整机关键零部件等效建模的鸟撞有限元模型。其次,对航空发动机鸟撞适航符合性要求进行分解,确定了造成叶片结构损伤的关键吸鸟参数。最后,基于最严苛情况的整机鸟撞有限元模型,研究了大鸟、中鸟鸟群和大型群鸟导致的转动不平衡、不平衡载荷传递和叶片损伤。数值模拟结果表明大鸟的撞击对航空发动机结构安全的威胁最大,鸟群撞击导致的叶片损伤范围更广。基于整机的鸟撞数值模拟对于航空发动机的结构安全性设计和适航认证是非常具有价值的。

多翼离心风机叶轮内油性粒子沉积特性的数值研究

为了揭示多翼离心风机内部油性粒子沉积分布规律,减少风机内粒子沉积,采用Fluent离散相模型描述粒子运动,同时结合临界速度模型和用户自定义函数(UDF)建模油性粒子在壁面上的沉积,模拟研究了多翼离心风机内油性粒子的运动轨迹和沉积特性,并探究了颗粒直径对沉积分布的影响。结果表明:油性粒子沉积主要分布在叶片压力面,且靠近出口尾缘段尤为严重;由于进气条件不稳定,整机下内部流场更为紊乱,沉积情况也更为严重;大直径粒子受惯性力主导更容易沉积在叶片表面。针对油性粒子沉积分布规律及成因,提出了切割叶片减小叶片出口安装角从而减少叶轮内油性粒子沉积的方法。对于切割后的叶片,叶轮出口处流动分离区域减小,叶片尾缘段涡量减小,通过数值模拟和实验研究发现,叶轮内油性粒子沉积率分别下降了30.75%和30.66%,两者吻合良好,证实了提出的减小叶轮油性粒子沉积方法的有效性。

复材风扇叶片榫头元件低周疲劳和损伤模式

为考核层合结构复材风扇叶片在1.5倍离心载荷下的低周疲劳寿命,制备一批风扇叶片,在薄弱部位取样。通过建立层合结构风扇叶片有限元模型,模拟榫头的应力状态,从而确定拉伸载荷水平,开展拉-拉载荷低周疲劳测试。在相邻铺层间引入内聚力单元,并考虑榫头试样单向带面内损伤,模拟损伤变量随循环数累积的过程,增加虚拟拉伸载荷,得到榫头低周疲劳失效时刻的损伤状态。试验结果说明榫头元件形成分层裂纹的平均寿命为17207次循环,首次出现分层裂纹的位置基本一致。数值仿真结果表明榫头单向带基体和层间损伤累积引起裂纹扩展,导致低周疲劳失效。本研究可为建立层合结构复材风扇叶片低周疲劳寿命试验流程和疲劳失效判据提供支撑。

叶片背面改型对轴流风机性能和压力脉动特性的影响

以小型轴流风机为研究对象,设计了光滑、凸槽、凹槽3种不同叶片背面形式的风机模型,并采用SST k-ω湍流模型研究其定常性能和非定常压力脉动特性。研究结果表明,3种轴流风机模型的全压-流量特性曲线基本一致,差别不明显,即叶片背面增加凸槽或者开槽对轴流风机的外特性影响较小。此外,叶轮和导叶各个监测点处的压力脉动规律一致,其脉动主频均位于叶频及其倍频处,脉动幅值随着倍频增加而减小。模型model 1由于凸槽叶型对流体的调制作用,叶轮流域内流体分布更加均匀,其压力脉动强度最低,而模型protype 0和model 2的叶片调制作用较弱,其内部流体脉动较为强烈,压力脉动的幅值也较高。综合轴流风机效率和噪声指标,模型model 1不仅能保证风机的全压性能,还能实现较小的脉动,其综合性能最佳。