Convergence Analysis of the Numerical Solution for Cathode Design of Aero-engine Blades in Electrochemical Machining

As a main difficult problem encountered in electrochemical machining （ECM）, the cathode design is tackled, at present, with various numerical analysis methods such as finite difference, finite element and boundary element methods. Among them, the finite element method presents more flexibility to deal with the irregularly shaped workpieces. However, it is very difficult to ensure the convergence of finite element numerical approach. This paper proposes an accurate model and a finite element numerical approach of cathode design based on the potential distribution in inter-electrode gap. In order to ensure the convergence of finite element numerical approach and increase the accuracy in cathode design, the cathode shape should be iterated to eliminate the design errors in computational process. Several experiments are conducted to verify the machining accuracy of the designed cathode. The experimental results have proven perfect convergence and good computing accuracy of the proposed finite element numerical approach by the high surface quality and dimensional accuracy of the machined blades.

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.

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. .

Aero-engine Blade Fatigue Analysis Based on Nonlinear Continuum Damage Model Using Neural Networks

Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the blade.Fatigue tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training set.Comparing with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load range.It has significant accuracy when the load is below 500 MPa.Especially,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement technology.The loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN model.The final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.

An Error Area Determination Approach in Machining of Aero-engine Blade

As a result of the recently increasing demands on high-performance aero-engine,the machining accuracy of blade profile is becoming more stringent. However,in the current profile,precision milling,grinding or near-netshape technology has to undergo a tedious iterative error compensation. Thus,if the profile error area and boundary can be determined automatically and quickly,it will help to improve the efficiency of subsequent re-machining correction process. To this end,an error boundary intersection approach is presented aiming at the error area determination of complex profile,including the phaseⅠof cross sectional non-rigid registration based on the minimum error area and the phaseⅡof boundary identification based on triangular meshes intersection. Some practical cases are given to demonstrate the effectiveness and superiority of the proposed approach.

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.

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 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.

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.

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.

钛合金包边复合材料风扇叶片的鸟撞数值仿真

为降低鸟体撞击航空发动机中带钛合金包边树脂基复合材料风扇叶片的试验成本,开展了数值仿真研究,为钛合金包边在航空发动机风扇叶片上的应用提供参考和依据。对风扇叶片进行简化,采用ABAQUS有限元软件构建了鸟撞带钛合金包边和不带钛合金包边的风扇叶片模型,其中,钛合金包边和复合材料叶片之间用粘结界面单元进行粘接,研究了不同鸟体冲击角度和速度下2种风扇叶片的损伤。结果表明:在鸟体冲击速度相同时,随着冲击角度的增大,风扇叶片的损伤增大且能量吸收率提高,在冲击角度也相同时,带钛合金包边的风扇叶片损伤更小且能量吸收率更高;在鸟体冲击角度相同时,随着冲击速度的加快,风扇叶片的损伤增大且能量吸收率提高;在鸟体冲击下,粘结界面单元最终发生拉伸破坏,在低速度冲击下还会发生剪切损伤。

基于改进YOLOv8的风机桨叶缺陷检测算法

叶片作为风力发电机组的重要部件,容易受到自然环境的影响,导致出现侵蚀、裂纹、胶衣脱落等损伤,从而影响风力发电效率和机组的安全运行。针对复杂环境下风机桨叶缺陷检测精度较低的问题,提出了一种改进YOLOv8的风机桨叶缺陷检测算法。通过对骨干特征提取网络中的单一模块SPPF融入LSKA注意力机制,以增强网络对于重要特征的关注度,提高模型的性能;其次,Neck部分采用加权双向特征金字塔Bi-FPN结构,并使用FasterBlock改进C2f模块,提出了Bi-YOLOv8-faster轻量级网络结构,增强模型多尺度特征融合能力,提高小目标检测精度;最后,采用辅助边框计算损失的Inner-IoU方法对损失函数进行优化,提高模型缺陷检测的准确率和泛化能力。通过对风机桨叶图像进行缺陷检测实验,结果表明,所提方法对缺陷检测的精确率提升了7.3%、mAP50提升了3.3%、参数量降低了27%。

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.

多翼离心风机气动噪声数值预测

文章采用计算流体力学软件Fluent对多翼离心风机的内部流场进行三维的定常和非定常数值模拟,并对数值结果进行了分析。数值结果与试验结果的对比分析表明了数值模拟具有较好的准确性和可信度。随后,基于流场的计算结果进行声场的数值计算,结果表明:基于非定常流动的FW-H声压模型可获得多翼离心风机气动噪声主要噪声源在声学接收点处的噪声频谱,有助于更深层地了解声源的噪声特性以及明确噪声峰值所对应的频率段,为下一步进行有针对性的噪声控制研究提供有力的依据。

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。

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。

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。

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。