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.

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.

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).

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.

船用柴油机涡轮增压叶片的计算机辅助设计优化

使用经验公式和物理试验法对涡轮增压叶片进行优化设计存在周期长、成本高的弊端,本文将计算机辅助设计方法应用到船用柴油机涡轮增压叶片设计中,完成了涡轮增压叶片二维结构、三维结构的基本设计,并对其进行气动性能仿真。使用等熵效率作为叶片优化设计的评价指标,研究了叶片进口角和等熵效率之间的关系。研究结果表明,计算机辅助设计方法可以大幅度提升设计效率,并实现了叶片设计、仿真反馈、优化设计、再反馈的闭环效果。

基于CFD的多叶可控网板水动力特性及压力流场研究

传统网板通过改变曳纲长度和拖速控制作业深度,通过改变网板与曳纲和手纲的固结点位置调整作业姿态,操作复杂。为了给可控变水层网板的设计研究提供科学参考,设计了一款多叶可控网板,通过数值模拟仿真计算流体动力学(Computational fluid dynamics,CFD)探究其不同部位(上端、下端)叶片的转动方向和转动角度(-40°~40°)对其水动力性能的变化影响。结果显示:1)叶片闭合时,多叶可控网板的升力系数在20°冲角时达到最大值0.88;其升阻比在5°冲角时达到最大值8.85。2)0°冲角时,网板两端叶片朝负方向转动,升力逐渐减小至0,并在转角为-20°时,升力变为相反方向;两端叶片朝正方向转动,升力系数先增大后减小,在转角为20°时达到最大值0.32;升阻比随叶片冲角的增加而减小。3)20°冲角时,网板两端叶片朝正方向转动,升力系数不断减小;叶片朝负方向转动,升力系数先增大后减小,在-10°转角时达到最大值1.05;升阻比在-20°转角时达到最大值5.25。4)两组冲角下,两端叶片分别朝正方向转动,Z轴分力系数均先增大后减小。

不同叶高水平的透平叶片气动特性分析

为了能够通过CFD手段优化透平叶片气动性能,本文使用雷诺平均方法针对工程上应用的66、44以及22 mm共3种典型叶高水平的透平模型进行了数值模拟,并将计算结果同实验测量结果进行了对比。同时,使用大涡模拟数值方法对22 mm叶高的模型进行非定常计算,得到了与实验结果吻合更好的等熵效率、质量流量等流场宏观参数,在三维流场上透平叶片的叶根与叶顶处的流动更为复杂。研究结果表明:雷诺平均方法可以对66和44 mm叶高的透平模型进行较准确的评估,对于22 mm叶高的透平,只有大涡模拟方法才能够清晰地捕捉到端壁区域紊乱的流动细节。叶片端部区域损失较大,雷诺平均方法处理得到的短叶片端壁区域丢失了流动的脉动细节,导致无法进行准确计算其端壁区域的流动。

基于生成对抗网络的潮流能水轮机水翼优化设计

针对水翼的全局优化需大量的计算流体动力学(CFD)模拟进而增加计算成本的问题,提出一种基于生成对抗网络(GAN)和CFD的水翼优化设计框架,利用GAN根据现有翼型库对水翼设计进行参数化,由于GAN的高维生成能力,这种参数化方法仅使用少量的参数即可生成大量光滑逼真的水翼,降低了水翼参数的维度。该优化框架结合Python脚本和OpenFOAM自动完成水翼的网格生成和流体仿真,可得到具有更高升阻比的水翼,优化总时间成本为69.8 h,提高优化效率和精度。此外,将优化水翼应用于潮流能水轮机叶片的设计,结果表明,优化水翼Optc建模的水轮机叶片最佳获能系数提升15.56%,显著提高水轮机的获能性能。

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.

A separation column for liquid mixture based on phase transform:Experiment and simulation

The concentric internally heat-integrated distillation column(HIDi C) has advantages of low energy consumption and high thermodynamic efficiency. However, its drawbacks of limited heat transfer area,complex internal structure, and large number of control parameters hinder its widespread industrial applications. To solve these challenges, in this work a novel sleeve-like concentric heat-integrated separation column, namely temperature-controlled phase change column(TCPC), was developed to separate liquid mixtures in a more effective and energy-saving way with reflux section being moved and trays being replaced with spiral corrugation blades. The comprehensive performances of TCPC in ethanol-water system was firstly evaluated by experiments. The results showed that TCPC performs well in ethanol-water separation due to the internal spiral corrugation significantly reducing the vapor-liquid contact in separation section. Meanwhile, compared to the concentric HIDi C, TCPC has a higher total heat transfer coefficient due to the larger heat transfer area. Computational fluid dynamics simulation reveals the internal design of TCPC inducing secondary vortices of the vapor, enhancing condensation heat transfer and separation efficiency. Further, increasing the mass flow rate within a certain range would enhance the comprehensive performance factor and lead to more effective separation.

叶片不同切割形状对离心泵各项性能的影响

离心泵叶片直接影响离心泵的效率与使用寿命,因此,对叶片形状进行研究具有重要意义。对离心泵叶片出口边进行单一切割以改变离心泵性能,在此基础上,对叶片前缘、尾缘进行了双向切割,研究了不同切割形状对离心泵各项性能的影响。首先,以一台n_(s)=73的离心泵作为研究对象,使用UG软件进行了离心泵三维建模与叶片切割(切割出了24种叶片模型);然后,使用ICEM软件划分了网格,选用标准k-ε湍流模型作为计算模型,在离心泵叶片与蜗壳隔舌处设置了监测点;最后,采用ANSYS CFX软件,对无切割和切割后的模型进行了离心泵数值模拟计算,得到了离心泵在0.6Q_(d)~1.4Q_(d)工况下的外特性曲线;在外特性良好的前提下,研究了其内部流动结构、压力脉动特性,以及湍动能分布。研究结果表明:在1.0Q_(d)设计工况下,切割后的模型较无切割模型的效率均提升了4%左右,对称切割的模型中前缘为椭圆、尾缘为钝形的模型7的效率提升最高,提升了4.8%,非对称切割前缘为圆形、尾缘为背面半切割的模型14效率提升了5.4%;无切割模型内部流线紊乱且内部相对速度高的区域较多,非对称切割的模型14叶轮内部流线分布均匀且相对速度值和分布区域减小;相对于无切割模型,切割后的模型内部压力升高,对称切割的模型7压力脉动减小了10%,而非对称切割的模型14压力脉动强度增加了近30%;切割后的模型湍动能分布明显改善,尾缘处湍动能值减小,对称切割的模型7湍动能随时间变化而变化不大,表现更稳定。综合不同切割模型的外特性及稳定性表现可知,将前缘切割为椭圆、尾缘切割为钝形,能有效提升离心泵的性能。

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。

3D Computation of Hydrogen-Fueled Combustion around Turbine Blade-Effect of Arrangement of Injector Holes

Recently, a number of environmental problems caused from fossil fuel combustion have been focused on. In addition, with the eventual depletion of fossil energy resources, hydrogen gas is expected to be an alternative energy resource in the near future. It is characterized by high energy per unit weight, high reaction rate, wide range of flammability and the low emission property. On the other hand, many researches have been underway in several countries to improve a propulsion system for an advanced aircraft. The system is required to have higher power, lighter weight and lower emissions than existing ones. In such a future propulsion system, hydrogen gas would be one of the promising fuels for realizing the requirements. Considering these backgrounds, our group has proposed a new cycle concept for hydrogen-fueled aircraft propulsion system. In the present study, we perform 3 dimensional computations of turbulent flow fields with hydrogen-fueled combustion around a turbine blade. The main objective is to clarify the influence of arrangement of hydrogen injector holes. Changing the chordwise and spanwise spacings of the holes, the 3 dimensional nature of the flow and thermal fields is numerically studied.

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.

基于CFD的大型风力发电机组叶片气动性能研究

为了研究大型风力发电机组叶片的气动性能,提出了基于CFD技术的叶片气动性能分析方法.该方法采用RANS方程结合SST湍流模型,以实现对大型风机叶片二维翼型气动性能和三维气动性能的分析预报.在此基础上,采用二维方法分析了NACA64-618翼型-180°～180°攻角下的气动性能,获得了其失速攻角,与试验数据的比较证明了该方法的准确性;建立了2MW大型风机三维叶轮模型,采用三维方法分析了其气动性能,与GHBladed软件计算结果比较证明了三维方法的可行性.最后,对2MW风机翼型进行了优化,改善了其气动性能.研究方法对于大型风机叶片的设计,优化及新翼型的开发具有重要参考价值.

转捩对风力机翼型和叶片失速特性影响的数值模拟

采用基于k-ωSST湍流模型的Gamma-Theta转捩模型对S809翼型和NREL Phase VI叶片进行了考虑转捩的气动力数值模拟,研究了转捩对其气动特性特别是失速特性的影响。首先对S809翼型在迎角0°～30°范围内开展了数值模拟,比较了转捩模拟和全湍流模拟获得的翼型升力系数和流场特征,发现前缘层流分离泡的存在显著影响了翼型的失速特性;然后对NREL Phase VI叶片开展了类似的数值模拟,结果显示转捩对叶片失速特性和翼型失速特性产生影响的作用方式是相似的。经过对以上数值模拟结果加以分析认为,转捩对翼型和叶片失速特性的影响主要通过前缘层流分离泡的作用体现出来,前缘层流分离泡的存在使翼型和叶片更早地进入深失速。