Performance enhancement of axial fan blade through multi-objective optimization techniques

This paper presents an axial fan blade design optimization method incorporating a hybrid multi-objective evolutionary algorithm (hybrid MOEA). In flow analyses, Reynolds-averaged Navier-Stokes (RANS) equations were solved using the shear stress transport turbulence model. The numerical results for the axial and tangential velocities were validated by comparing them with experimental data. Six design variables relating to the blade lean angle and the blade profile were selected through Latin hypercube sampling of design of experiments (DOE) to generate design points within the selected design space. Two objective functions, namely, total efficiency and torque, were employed, and multi-objective optimization was carried out, to enhance the performance. A surrogate model, Response Surface Approximation (RSA), was constructed for each objective function based on the numerical solutions obtained at the specified design points. The Non-dominated Sorting of Genetic Algorithm (NSGA-II) with local search was used for multi-objective optimization. The Pareto-optimal solutions were obtained, and a trade-off analysis was performed between the two conflicting objectives in view of the design and flow constraints. It was observed that, by the process of multi-objective optimization, the total efficiency was enhanced and the torque reduced. The mechanisms of these performance improvements were elucidated by analysis of the Pareto-optimal solutions.     

High-efficiency design optimization of a centrifugal pump

Design optimization of a backward-curved blades centrifugal pump with specific speed of 150 has been performed to improve hydraulic performance of the pump using surrogate modeling and three-dimensional steady Reynolds-averaged Navier-Stokes analysis. The shear stress transport model was used for the analysis of turbulence. Four geometric variables defining the blade hub inlet angle, hub contours, blade outlet angle, and blade angle profile of impeller were selected as design variables, and total efficiency of the pump at design flow rate was set as the objective function for the optimization. Thirty-six design points were chosen using the Latin hypercube sampling, and three different surrogate models were constructed using the objective function values calculated at these design points. The optimal point was searched from the constructed surrogate model by using sequential quadratic programming. The optimum designs of the centrifugal pump predicted by the surrogate models show considerable increases in efficiency compared to a reference design. Performance of the best optimum design was validated compared to experimental data for total efficiency and head.     

Multi-objective optimization design and experimental investigation of centrifugal fan performance

Current studies of fan performance optimization mainly focus on two aspects： one is to improve the blade profile, and another is only to consider the influence of single impeller structural parameter on fan performance. However, there are few studies on the comprehensive effect of the key parameters such as blade number, exit stagger angle of blade and the impeller outlet width on the fan performance. The G4-73 backward centrifugal fan widely used in power plants is selected as the research object. Based on orthogonal design and BP neural network, a model for predicting the centrifugal fan performance parameters is established, and the maximum relative errors of the total pressure and efficiency are 0.974% and 0.333%, respectively. Multi-objective optimization of total pressure and efficiency of the fan is conducted with genetic algorithm, and the optimum combination of impeller structural parameters is proposed. The optimized parameters of blade number, exit stagger angle of blade and the impeller outlet width are seperately 14, 43.9~, and 21 cm. The experiments on centrifugal fan performance and noise are conducted before and after the installation of the new impeller The experimental results show that with the new impeller, the total pressure of fan increases significantly in total range of the flow rate, and the fan efficiency is improved when the relative flow is above 75%, also the high efficiency area is broadened. Additionally, in 65% -100% relative flow, the fan noise is reduced. Under the design operating condition, total pressure and efficiency of the fan are improved by 6.91% and 0.5%, respectively. This research sheds light on the considering of comprehensive effect of impeller structrual parameters on fan performance, and a new impeller can be designed to satisfy the engineering demand such as energy-saving, noise reduction or solving air pressure insufficiency for power plants.     

高效低噪声地铁风机气动设计及数值模拟

主要对地铁风机设计中的空气动力学特性进行研究。首先,对各型地铁风机的原理及设计特点进行了分析总结;其次,编写了高效低噪声地铁风机C语言设计程序,并设计了一款10号地铁风机;最后,对所设计的风机用CATIA建立三维模型,并用FLUENT软件进行数值模拟。数值模拟与程序设计比较结果显示,所使用的设计方法、编制的C语言设计程序以及所使用的数值模拟方法均是可靠的、实用的,可以用于地铁风机的实际设计中。     

Aerodynamic design and optimization of a high-loaded axial fan stage using a curvature control method

This study designs and optimizes a high-loaded transonic fan stage using a curvature control method. A fan stage with a total pressure ratio of 2.49 and adiabatic efficiency of over 87 % at the design point is obtained after 3D optimizations. The geometric curvature of the blade passage has important driving and adjusting effects on the mainstream and on the flow in the boundary layer. The reasonable optimization of camber line curvature can weaken the radial secondary flow on the blade surface and decrease shock losses effectively. It can also postpone or suppress boundary layer separation by reorganizing aerodynamic load. Hence, secondary flow losses are reduced, and the overall stall margin is expanded. This method features high precision, high operability, and short design cycle, hence providing highloaded fans/compressors with new freedom to improve design ability and offering new possibility to design system development.

     

Implementation of design of experiment for structural optimization of annular jet pumps

The DOE (Design of experiments) method together with CFD (Computational fluid dynamics) was applied to optimize structural combination of the Annular jet pumps (AJPs). An AJP with an area ratio of 1.75 was selected as the simulation prototype and the numerical results were validated by experiments. According to the DOE method, four impact factors were selected for simulation. The results showed that two-factor’s reciprocal action is more applicable than that of single factor on the AJP’s performance, especially the two groups, α*l _t and l _t*β, respectively. The structure of AJPs with different area ratios ranging from 1.5 to 40 were optimized by the DOE method. The corresponding optimum structural parameters and performance curves were plotted to acquire the performance envelope lines, the efficiency envelope line and the peak efficiency lines, which are useful for AJP’s structure design and obtaining its operation condition.     

High-efficiency design of a mixed-flow pump using a surrogate model

In the present work, the fluid flow characteristics of a mixed-flow pump have beenwere investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model and hexahedral grid system were used to analyze the flow in the mixed-flow pump. The efficiency of the mixed-flow pump was evaluated using the variation of two geometric variables related to the inlet angle of the diffuser vane. The design optimization of the mixed-flow pump was performed to maximize the its efficiency at the prescribed specific speed using a surrogate model. Latin hypercube sampling was used to determine the training points for the design of the experiment, and the surrogate model was constructed using the objective function values at the training points. The results show that the efficiency of the mixed-flow pump at the prescribed specific speed is improved considerably by the design optimization.     

Structural optimization of a Cu(In,Ga)Se2 thin film solar cell using numerical simulation and design of experiment techniques

The structural optimization for a thin film solar cell module based on Cu(In,Ga)Se₂ is investigated through numerical simulation and sequential statistical analyses. First, an equivalent numerical model for solar cells is constructed with an electrical circuit consisting of large area diodes and analysis using finite element analysis (FEA). A good agreement in performance characteristic curves between the developed numerical model and practical solar cells is obtained after performing parameter adjustments. To maximize the light conversion efficiency, an optimization technique using the design of experiment (DOE) of orthogonal arrays is employed. The programmed block diagram is used to calculate electric potentials inside solar cell layers and the associated solar performances. Statistical analysis of variance (ANOVA) and F-test are used to discover the dominant design variables (DVs) which are more important on solar cell performances. The second order regression model which relates dominant DVs with solar cell efficiency is mathematically obtained by the employment of response surface model (RSM) and graphically described by the equipotential contour plots.     

发动机冷却风扇性能的优化设计研究

针对面向性能的发动机冷却风扇叶片几何形状优化的问题,将参数化建模技术应用到对冷却风扇叶片安装角的描述中,建立了冷却风扇的参数化模型,以多学科优化平台Isight和商业流体模拟软件Fluent为基础,建立了一种模型参数化、网格划分、CFD分析和多目标优化相结合的发动机冷却风扇优化集成平台,并运用非支配排序遗传算法对冷却风扇进行了优化。对优化结果与试验结果进行了对比,分析了冷却风扇的内部流场。研究结果表明,优化后的风扇模型静压提高了12.840 6%,动压和风扇效率也有所提高,冷却风扇的整体性能得到了优化。     

均速管流量计优化设计的数值模拟

根据流体力学计算方法,对300 mm口径管道对应的均速管流量计进行二维数值模拟,采用k-ωSST湍流模型及SIMPLE算法,首先得到均速管流量计流量系数随速度的变化特性;在其基础上,创新设计了一种新型的双体均速管流量计,这种新型均速管流量计较传统的威力巴流量计而言,在压力损失有限增加的前提下,能产生更高的输出压差和更低的流量系数.     

Study on flow force compensation characteristics and optimization design of jet guiding groove

A jet guiding groove is designed on the spool to compensate the steady-state flow force. The steady-state flow force model is analyzed and derived. The influence of structural parameters on steady-state flow force is studied by CFD simulation. The response surface method is used to construct the steady-state flow force polynomial regression model. The optimal structure size of the jet guiding groove is obtained. The steady-state flow force compensation coefficient is defined and calculated. Results show that the compensation effect decreases with the increase of pressure difference. However, at the same pressure difference, the absolute value of the compensation coefficient of the spool with jet guiding groove is less than that of the spool without jet guiding groove. The results show that the jet guiding groove can effectively compensate the steady-state flow force and improve the control accuracy of the valve.     

圆盘型磁流变调速风扇离合器的设计与分析

磁流变液是一种新型智能材料,其屈服强度在外加磁场作用下可在毫秒量级内发生变化,利用磁流变液剪切应力可以进行动力的传递。将磁流变液用于发动机冷却系风扇离合器的设计中,在理论上分析了盘式磁流变液调速风扇离合器的工作机理,应用Bingham模型来描述磁流变液的本构方程,建立了离合器的输出转矩与转速的计算模型．导出了离合器基本几何参数的工程设计计算公式,为盘式磁流变风扇离合器的设计提供了理论依据。     

Numerical optimization study to install air curtain in a subway tunnel by using design of experiment

Subways are a major mode of public transportation in metropolitan cities. A proper ventilation system is required to maintain indoor air quality in subway tunnels. Platform screen doors improve the platform environment but degrade air quality in subway tunnels. Trains transport fine particles from the tunnel into the platform. An air curtain installation in the subway tunnel permits traffic and reduces the transfer of bacteria and fine particles. The existing tunnel of Seoul subway was investigated by using computational fluid dynamics and design of experiment method for optimum air curtain installations. The flow field of the subway tunnel was computed by using ANSYS CFX software. Minitab software was used to generate the design process and to analyze the computational results. The computational domain of the existing tunnel included two natural ventilation shafts, one mechanical shaft, and the twin tracks. The height, width, and length of each track were 6, 4, and 400 m, respectively. The air curtain installation area was located between the natural and the mechanical ventilation shafts of Rrack 1. The design variables for the optimization study were the width, velocity, and installation location of the air curtain. The object function for optimization was mass flow rate at the natural ventilation shaft. The length of the air curtain was fixed at 4 m. The predicted mass flow rates were analyzed with the design variables by using the response surface method (RSM). The optimum values of the design variables, i.e., velocity, width, and installation location were 25 m/s, 0.2 m, and 5.8195 m, respectively. The maximum mass flow rate with the optimum design values was 114.4447 kg/s. The optimum values of the design variables were validated by computing the tunnel with the optimum values from RSM. The mass flow rate in the natural ventilation shaft 1 was 114.2 kg/s, as predicted. The optimization study can be helpful to set the optimum design conditions for the subway ventilation system.     

Physiologic consequences of high frequency jet ventilation

High frequency jet ventilation provides effective gas exchange at frequencies of 60 to 900 minute-1. The selection of mechanical ventilatory support is based on multiple factors, including potential physiologic advantages and disadvantages. Although HFJV has demonstrated no clear significant advantage over CMV in many clinical applications, because it produces significantly lower peak airway pressures than CMV, cardiac compromise and barotrauma might be prevented. In addition, in situations in which tissue movement should be minimized, e.g., microneurosurgery, HFJV may prove beneficial.     

基于FLUENT的离心吸纤维风机改进研究

某离心吸纤维风机存在着耗能大,效率不高,风压不均等问题。用Pro/E软件为该离心风机造型,应用Fluent软件进行三维数值模拟,详细得到风机内部流场情况。根据气动流场以及离心吸纤维通风机的特殊功用,进行优化设计,证明改进设计是成功的。提出了几点关于使用Fluent软件在设计计算中应注意的问题。对该类风机设计有良好的借鉴作用和现实意义。     

NURBS在风机设计中的应用

风机叶片的表面是一种复杂曲面,用传统造型方法难以取得良好效果,而NURBS(非均匀有理B样条)以其诸多优良特性正日益成为一种工业标准。首先介绍了NURBS的数学定义,然后针对风机叶片的造型设计,讨论了用NURBs方法构造曲面的插值算法。     

基于数值模拟的对旋风机功率匹配研究

针对于一台对旋风机样机,建立从集流器进口到扩散器出口的全流场作为计算域,采用SIMPLEC算法和RNG湍流模型,通过求解三维N-S方程,对全流场进行数值模拟,揭示了对旋式通风机流场内部气流的真实流动规律。通过改变运行参数,完成对旋风机两级叶轮最佳功率匹配的研究,为对旋风机的优化设计提供理论基础。     

Design of single- and multiple-dwell six-link mechanisms through design optimization

Nonlinear programming techniques are applied to a class of six-bar linkages to produce single- and multiple-dwell mechanisms. The six-bar linkage consists of a four-bar crank-rocker mechanism driving a slider crank mechanism from a coupler point. The dwell position(s) may be specified at any value of input link rotation and may last for any reasonable duration. The total stroke and the location of the slider at each dwell position may also be specified. A design optimization problem is formed which attempts to generate a linkage in which the slider link will travel in a circular path and thus produce a dwell period in the cycle at the appropriate link position. This problem is then solved by an exterior penalty function technique. The linkage model is constructed using the vector loop approach and examples for both a single- and double-dwell mechanism are included. Extensions including velocity, acceleration and transmission angle constraints are also discussed.     

基于虚拟设计制造技术的大型风洞设备开发

FL-9低速增压风洞是"十五"国家批准建设的大型航空基础设施,以其开发研制为背景,运用制造业信息化技术,构建了大型风洞设备的虚拟设计制造平台.此平台具备网络系统支持下的设备三维数字化设计、计算机辅助分析、计算机辅助工艺设计、可视化及三维交互等功能.并建立了风洞设备设计制造信息化体系,实现了设计制造全过程信息分类代码的规范和统一.基于此平台开发的FL-9低速增压风洞经5年的研制已全面建成并首次试车成功.     

2009年中国将成为世界最大的风机生产国

国际风能委员会秘书长Steve Sawver称,2009年中国将成为世界最大的风力涡轮机生产国,这将为迅速发展的可再生能源领域带来新变革。根据该机构的数据,虽然2007年风力发电仅占全球电力供应的1％,但发展迅速,到2020年风力发电将满足世界12％的电力需求,这将对控制全球气候变暖大有益处。