Wind Tunnel Test and Numerical Computation on Ice Accretion on Blade Airfoil for Straight-bladed VAWT

To invest the condition of ice accretion on the blade used for straight-bladed vertical axis wind turbine （SB-VAWT）, wind tunnel tests were carried out on a blade with NACA0015 airfoil by using a small simple icing wind tunnel. Tests were carried out at some typical attack angles under different wind speeds and flow discharges of a water spray with wind. The icing shape and area on blade surface were recorded and measured, Then the numerical computation was carded out to calculate the lift and drag coefficients of the blade before and after ice accretion according to the experiment result, the effect of icing on the aerodynamic characteristics of blade were discussed.

Computational Fluid Dynamics Analysis of Multi-Bladed Horizontal Axis Wind Turbine Rotor

The principal objective of this work was to investigate the 3D flow field around a multi-bladed horizontal axis wind turbine (HAWT) rotor and to investigate its performance characteristics. The aerodynamic performance of this novel rotor design was evaluated by means of a Computational Fluid Dynamics commercial package. The Reynolds Averaged Navier-Stokes (RANS) equations were selected to model the physics of the incompressible Newtonian fluid around the blades. The Shear Stress Transport (SST) k-ω turbulence model was chosen for the assessment of the 3D flow behavior as it had widely used in other HAWT studies. The pressure-based simulation was done on a model representing one-ninth of the rotor using a 40-degree periodicity in a single moving reference frame system. Analyzing the wake flow behavior over a wide range of wind speeds provided a clear vision of this novel rotor configuration. From the analysis, it was determined that the flow becomes accelerated in outer wake region downstream of the rotor and by placing a multi-bladed rotor with a larger diameter behind the forward rotor resulted in an acceleration of this wake flow which resulted in an increase the overall power output of the wind machine.

整体叶盘五轴数控加工技术研究

整体叶盘作为航空发动机的关键部件,其加工技术受到了广泛关注。五轴数控加工技术作为一种先进的加工方法,在整体叶盘加工中具有广泛的应用前景。基于此,探讨整体叶盘五轴数控加工技术的关键技术、应用与发展趋势,以及整体叶盘五轴数控加工及仿真。

叶形仿生优化对离心血泵水力性能及溶血特性的影响

离心血泵的优化对于体外膜肺氧合的临床应用具有重要意义。本研究参考座头鲸在深海中作原地转身运动时其鳍状肢的流线形,重新设计血泵的叶片。采用计算流体动力学对血泵性能进行预测和评估;通过水力试验来验证数值计算的准确性;溶血预测模型采用渐进一致数值近似方法。仿真结果表明,叶片尾缘形状对出口隔舌处的流场分布和该区域的壁面剪应力分布均有显著影响;当叶片尾缘达到一定扭转角度时,叶片结构能较好地适应泵内的流场环境,但当扭转角度不足时,流场扰动反而会增大。与原模型相比,扭转角为20°的模型在转速为2500 rpm、流量为5 L/min的工况下,扬程试验结果增加11.6%,水力效率提升3.1%,溶血指数下降40.1%。总的来说,具有一定扭转角度的仿生叶片尾缘结构可以提高半开放式离心血泵的性能。

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.

CFD Simulation and Experimental Study of a New Elastic Blade Wave Energy Converter

Small moving vehicles represent an important category of marine engineering tools and devices(equipment)typically used for ocean resource detection and maintenance of marine rights and interests.The lack of efficient power supply modes is one of the technical bottlenecks restricting the effective utilisation of this type of equipment.In this work,the performance characteristics of a new type of elastic-blade/wave-energy converter(EBWEC)and its core energy conversion component(named wave energy absorber)are comprehensively studied.In particular,computational fluid dynamics(CFD)simulations and experiments have been used to analyze the hydrodynamics and performance characteristics of the EBWEC.The pressure cloud diagrams relating to the surface of the elastic blade were obtained through two-way fluid-solid coupling simulations.The influence of blade thickness and relative speed on the performance characteristics of EBWEC was analyzed accordingly.A prototype of the EBWEC and its bucket test platform were also developed.The power characteristics of the EBWEC were analyzed and studied by using the blade thickness and motion cycle as control variables.The present research shows that the EBWEC can effectively overcome the performance disadvantages related to the transmission shaft torque load and power curve fluctuations of rigid blade wave energy converters(RBWEC).

Study on the solid-liquid suspension behavior in a tank stirred by the long-short blades impeller

We investigated the solid–liquid suspension characteristics in the tank with a liquid height/tank diameter ratio of 1.5 stirred by a novel long-short blades(LSB) impeller by the Euler granular flow model coupled with the standard k–ε turbulence model. After validation of the local solid holdup by experiments,numerical predictions have been successfully used to explain the influences of impeller rotating speed,particle density, particle size, liquid viscosity and initial solid loading on the solid suspension behavior,i.e. smaller particles with lower density are more likely to be suspended evenly in the liquid with higher liquid viscosity. At a low impeller rotating speed(N), increase in N leads to an obvious improvement in the solid distribution homogeneity. Moreover, the proposed LSB impeller has obvious advantages in the uniform distribution of the solid particles compared with single Rushton turbine(RT), dual RT impellers or CBY hydrofoil impeller under the same power consumption.

Effect of pitched short blades on the flow characteristics in a stirred tank with long-short blades impeller

This work focuses on the design improvement of the long-short blades(LSB)impeller by using pitched short blades(SBs)to regulate the flow field in the stirred vessel.After mesh size evaluation and velocity field validation by the particle image velocimetry,large eddy simulation method coupled with sliding mesh approach was used to study the effect of the pitched SBs on the flow characteristics.We changed the inclined angles of the SBs from 30°to 60°and compared the flow characteristics when the impeller was operated in the down-pumping and up-pumping modes.In the case of down-pumping mode,the power number is relatively smaller and vortexes below the SBs are suppressed,leading to turbulence intensification in the bottom of the vessel.Whereas in the case of up-pumping mode,the axial flow rate in the center increased significantly with bigger power number,resulting in more efficient mass exchange between the axial and radial flows in the whole vessel.The LSB with 45°inclined angle of the SBs in the up-pumping mode has the most uniform distributions of flow field and turbulent kinetic energy compared with other impeller configurations.

Application Study on 3D Modeling of Axial Compressor Blades Based on CFD and CAD

A new method for design of turbomachinery blades is presented. The parameters of a compressor blade are created from the Computational Fluid Dynamics （CFD） software CFX-BladeGen, and are inputted to the Computer Aided Design （CAD） software UG for building a curve surface model to create an entity model in UG. The result shows that the blade model is favorable from the entity effect and reflection analysis and the model process is useful for the CAD model creation of turbomachinery blades.

Rapid Airfoil Design for Uncooled High Pressure Turbine Blades

The aero-engine design process is highly iterative,multidisciplinary in nature and complex.The success of any engine design depends on best exploiting and considering the interactions among the numerous traditional engineering disciplines such as aerodynamics and structures.More emphasis has been placed lately on system integration,cross disciplines leveraging of tools and multi-disciplinary-optimization at the preliminary design phase.This paper investigates the automation of the airfoil generation process,referred to as Rapid Airfoil3D(RAF-3D),for uncooled high pressure turbine blades at the preliminary design phase.This approach uses the TAML(Turbine Aero Mean Line)program in parallel with a database of previously designed P&WC airfoils,in-house design rules and best practices to define a pre-detailed airfoil shape which can be fed back to other analytical groups for pre-detail analyses,such as for structural integrity and vibrations.Resulting airfoil shapes have been aerodynamically validated using an in-house three dimensional Reynolds averaged Navier-Stokes code.RAF-3D will shorten the turnaround time for Pratt&Whitney turbine aerodynamics group to provide a preliminary3D airfoil shape to turbine structures group by up to a factor of ten.Additionally,the preliminary assessments of stress and vibration specialists will be more accurate as their assessments will be based on an airfoil that has had inputs from all functional groups even though it is"first pass"design.

基于DSST计算机视觉算法的风力机叶片动力特性测试

针对传统风力机叶片监测以人巡检为主耗时、费力且效率低下的问题,提出一种基于计算机视觉的风力机叶片动力特性自动识别方法。首先,对比颜色匹配算法、模板匹配算法和分辨尺度空间跟踪器(DSST)算法的性能,提出基于DSST动力特性识别算法,并对其性能进行对比分析;其次,结合叶片振动视频,利用叶片固有角点或边缘进行跟踪,在叶片表面无附加任何标志物的情况下,识别风力机叶片的动态位移;最后,基于视觉方法识别风力机叶片的动态数据对叶片结构进行评估,并与传统监测手段分析结果进行试验对比。结果表明:采用基于DSST计算机视觉算法可准确识别风力机叶片的动力特性,并在时域和频域均有较高精度,可为风力机叶片的状态评估提供依据。

共轴对转螺旋桨气动与噪声特性研究进展

共轴对转螺旋桨由于拉力大、气动效率高而备受人们的关注。本文从共轴对转螺旋桨的试验研究、气动性能评估、气动模拟、气动噪声预测、气动噪声优化设计等方面进行了综述。首先,总结了目前国内外在共轴对转螺旋桨气动及噪声方面的试验成果;随后,介绍了共轴对转螺旋桨气动力计算的工程方法,并详细阐述了北京航空航天大学陆士嘉实验室提出的共轴对转螺旋桨气动力评估的片条理论发展与参数选择;然后,介绍了共轴对转螺旋桨数值模拟方法,并针对共轴对转螺旋桨气动噪声预测的频域方法和时域方法进行了论述;最后,介绍了目前共轴对转螺旋桨气动噪声优化设计的研究成果。

鹰勾齿形双金属带锯条锯切过程数值模拟研究

研究了鹰勾齿形参数对锯切过程的影响,利用仿真模拟方法对该齿形进行优化设计,分析鹰勾齿的前角、后角、齿尖圆弧、分齿量、分齿高度以及分齿组合对锯切过程的影响规律。研究结果表明,改变齿形参数对锯切力和切削温度的影响较大,这会影响锯齿寿命和切削质量,通过齿形参数的优化设计,可以获得性能优良的鹰勾齿形带锯条。

圆盘涡轮式搅拌器的搅拌性能比较分析

在椭圆封头搅拌槽中根据行业标准建立了4种圆盘涡轮式搅拌器的几何模型,利用标准k-ε湍流模型和多参考系(MRF)方法,研究了叶片形状、搅拌速度、旋转方向和流型转变对搅拌功率、排出流量、泵出效率和剪切速率的影响。结果表明:叶片形状对功率、排出流量、泵出效率和流型转变的临界安装高度均有影响;径向流条件下,泵出效率排序为圆弧叶(反)>弯叶(正)>箭叶(反)>圆弧叶(正)>平直叶>箭叶(正)>弯叶(反);流型由径向流转变为轴向流后,搅拌功率及径向排出流量均下降。对标准搅拌器的性能评估为工业搅拌设备的选型和设计提供了参考依据。

诱导轮叶片参数对大流量离心泵汽蚀性能的影响

诱导轮作为离心泵的重要辅助部件之一,对水泵汽蚀性能的改善有重要作用。针对某大流量离心泵汽蚀性能不佳的问题,采用响应面分析和数值模拟的方式,对该离心泵的诱导轮叶片参数进行了优化,探究了诱导轮导程、叶片厚度和叶片数对大流量离心泵汽蚀性能的影响规律。首先,构建了大流量离心泵的仿真模型,对其进行了外特性计算,将计算结果与试验结果进行了对比,对仿真结果的可靠性进行了验证;然后,根据诱导轮扬程与泵汽蚀性能呈正相关的规律,以诱导轮的叶片参数(导程L、厚度T、叶片数Z)为变量因素,以诱导轮扬程最大为优化目标,对诱导轮进行了响应面计算分析,得到了响应面优化后的诱导轮叶片参数,并对比分析了优化前后诱导轮的扬程;最后,针对诱导轮优化前后的离心泵,在不同工况下进行了叶轮汽蚀情况和临界汽蚀余量对比分析。研究结果表明:叶片导程对诱导轮扬程的影响不大,而减小叶片厚度、增加叶片数可以大幅提高诱导轮扬程;额定工况下,经响应面优化后的诱导轮扬程提高了0.6 m,泵的临界汽蚀余量相比原型泵降低了0.15 m。该结果可以为大流量离心泵诱导轮的优化设计提供理论参考。

叶片型面视觉检测系统设计与实现

航空发动机压气机叶片审理和验收是其研制周期中不可或缺的环节,为改善传统人工叶片审理流程费时费力、不确定性高等问题,设计了一种基于机器视觉的发动机叶片型面检测系统。首先,针对工业生产中普遍使用的三坐标检测仪叶片测量法,完成对便携文件格式的批量图像提取,并利用颜色匹配和霍夫变换的方法完成叶片图像的超差判断;其次,对于无超差的叶片图像,利用颜色匹配和形态学算子等手段完成叶片图像的增强,提高有效信息占比,并训练残差网络完成叶片前后缘形态异常的分类任务;最后,针对大量图像数据的标注任务,设计普适性高的图像分类标注程序,并设计叶片质量检测程序在叶片图像数据集上验证了系统对叶片超差判断和异常识别的有效性。实验表明,该系统对叶片有超差和无超差异常的识别准确率分别达到100%和92.9%,可以满足工业生产实际需求。

海水循环泵叶轮多参数组合变型设计研究

在某核电站海水循环泵实际运行中,其选型扬程高于实际需要扬程的上限值,针对这一问题,以原模型额定工况点扬程的80%为变型目标,提出了一种基于多参数组合变型的叶轮改造设计方法。首先,在原有模型的基础上,选择叶轮外径、叶片出口安放角、叶片包角和叶轮出口宽度为研究因素,通过基于计算流体力学(CFD)数值模拟的正交试验设计,进行了变型参数分析;然后,总结了各参数与海水循环泵性能之间的关系,进行了变型方案设计,并比较了单因素变型设计与多因素耦合变型设计之间的区别,得到了主要参数的组合变型方案;最后,通过适配其他变型参数,得到了最优变型组合方案,分析了降低扬程和提升效率的流场特点,得到了多参数组合变型对海水循环泵叶轮性能的影响规律。研究结果表明:在额定工况点,变型后的海水循环泵扬程降低了18.57%,效率提升了0.63%,相比仅改变叶轮外径和仅改变叶片出口安放角降低扬程,循环泵的效率分别提高了7.52%和3.27%。

大尺度风轮高精度CFD缩比模型构建及其分析

针对大功率风电机组气动分析过程中叶素动量(BEM)理论计算精度不高、三维计算流体力学(CFD)仿真分析计算时间长的问题,以某5 MW风电叶片翼型数据为参考,分析不同风轮尺度下BEM与CFD的计算精度和效率;基于几何相似、运动相似和动力相似理论,推导缩比模型与原型之间的几何、运动、力学参数的比例关系,比较不同几何比例尺下风电叶片的气动性能;以几何比例尺为参考,建立大尺度风轮高精度缩比模型,分析多种工况下缩比模型CFD仿真的计算精度与效率。研究结果表明:风轮尺度越大,CFD与BEM分析的结果相对差值越大,多种工况下大尺度风轮缩比模型气动性能基本与原型保持一致,但计算效率获得大幅提升。

Comparison of Aerodynamic Forces and Moments Calculated by Three-dimensional Unsteady Blade Element Theory and Computational Fluid Dynamics

In previous work, we modified blade element theory by implementing three-dimensional wing kinematics and modeled the unsteady aerodynamic effects by adding the added mass and rotational forces. This method is referred to as Unsteady Blade Element Theory （UBET）. A comparison between UBET and Computational Fluid Dynamics （CFD） for flapping wings with high flapping frequencies （〉30 Hz） could not be found in literature survey. In this paper, UBET that considers the movement of pressure center in pitching-moment estimation was validated using the CFD method. We investigated three three-dimensional （3D） wing kinematics that produce negative, zero, and positive aerodynamic pitching moments. For all cases, the instantaneous aerodynamic forces and pitching moments estimated via UBET and CFD showed similar trends. The differences in average vertical forces and pitching moments about the center of gravity were about 10% and 12%, respectively. Therefore, UBET is proven to reasonably estimate the aerodynamic forces and pitching moment for flight dynamic study of FW-MAV. However, the differences in average wing drags and pitching moments about the feather axis were more than 20%. Since study of aerodynamic power requires reasonable estimation of wing drag and pitching moment about the feather axis, UBET needs further im- provement for hilzher accuracy.

尾随涡对风力机叶片气动性能影响机理研究

以PhaseⅥ风力机叶片为研究对象,以r/R=30%、63%和95%处叶素为参考,建立与7、9、15 m/s试验风速下该风力机叶片附着涡环量沿展向分布相同的叶片模型,分析尾随涡对风力机当地翼型气动性能的影响机理。采用带转捩效应的SST k-ω湍流模型,对所建立的叶片模型和二维S809翼型的气动特性进行研究和对比分析。结果表明:旋转叶片尾随涡对分离现象产生抑制作用且随攻角的增大减弱;尾随涡的影响表现出多重效应,除了减小当地翼型的攻角,还降低其吸力面负压系数和压力面正压系数。