Multi-point airfoil optimization for axial-flow fan

Airfoil is the element of fan blade design. It is strongly anticipated to design a fan of ave- raged high performance over a wide operation range. Multi-point optimization design of airfoil for axial flow fan was proposed over specific operation range. Weighted objective function of airfoil lift-drag ratio was constructed for several operation points around the designing one. Airfoil was defined by parametric B-spline curve of limited shape controlling points. Results show that normal standard airfoils have remained spaces to be optimized under specific operation conditions. Airfoil performance is sensitive to flow′s Reynolds number and cascade solidity. Predicting flow transition along airfoil profile is essential to search for optimized one. Optimized airfoil of wide operation range is possible to obtain with prescribed fitness function. Obtainments of multi-point optimization may be relatively lower at design point, but positive obtainments are achieved at off-design ones. Resulted airfoil is specially suitable for axial flow fans operating frequently at off-design point such as air condition coolers.

Transonic Airfoil Design and Optimization for an Unmanned Air Vehicle Concept

Design,optimization and analysis of a new energy efficient 16%thick transonic airfoil were completed for a notional air vehicle concept.The airfoil specifications included a range of Reynolds number per foot from 1.7 million to 2.5 million and Mach number from 0.4 to 0.8.Shape optimization in geometry and inverse design modules of the airfoil analysis program MSES were used to design a new 16%thick reference airfoil.The performance of the reference airfoil was then optimized with an objective of minimizing drag coefficient for 7 design points with conflicting requirements in Reynolds and Mach number by using the MSES/LINDOP optimizer.The optimization results in an upward shift of drag bucket in the direction of higher lift coefficient.Both surface pressure distribution and Mach contour plots show that supersonic compression waves on airfoil surface are terminated at Mach 0.78 with a normal shock wave and associated flow separation,which causes not only a decrease of the maximum suction pressure,but also a decrease in lift and increase in drag coefficient.The new optimized airfoil shows robust performance when operating within the specified design constraints.

基于Kriging插值代理模型的轴流式止回阀多目标优化

基于Kriging插值代理模型,对轴流式止回阀的各项性能进行综合优化,具体的优化目标为:降低正向流阻;减小阀芯振动;提升止回性能。通过试验设计方案找到影响轴流式止回阀正向流阻的主要结构参数因素,并以其作为优化对象,通过Kriging插值法拟合主要结构参数对应的性能样本点,在保证拟合精度的情况下,使用NSGA-II遗传算法同时对3个主要结构参数进行多目标优化,得到了三目标Pareto前沿,经过权衡不同因素对性能指标的影响大小,最终得到了综合性能最优的结构参数为:阀瓣丰满度系数α_(1)=2.199,阀芯长度L=386.322 mm,阀芯半径R=113.997 mm。其对应的止回阀性能为:正向出口流量Q=161.839 kg/s,正向出口流速v=3.30235 m/s,止回阀进口压力p=97632.2287 Pa。相比优化之前,阀门正向流阻减小了1.2%,阀芯振动降低了0.24%,止回性能提升了2.3%。

喷雾降尘对旋式轴流风机结构参数设计优化

随着中国城市化和工业化的快速发展,粉尘污染问题日益突出。通过对喷雾降尘对旋式轴流风机的结构参数即一级叶轮叶片数、二级叶轮叶片数和导流叶个数进行单因素实验,将风机射程、流量及全压效率等作为评价指标,获得优化方案并仿真验证。研究表明:通过单因素分析,确定各结构参数的优选数值分别为一级叶轮叶片数为9,11,13,二级叶轮叶片数为8,10,12,导流叶个数为4,5,6;通过单因素实验及优化选定,确定优化方案为一二级叶轮叶片数分别为13,12,导流叶个数为6,优化方案较初始模型在射程提高了5.90%,流量提高了69.64%,全压效率提高到70.88%。

OPTIMIZATION DESIGN OF GAS-PARTICLE TWO PHASE AXIAL-FLOW FAN

Based on the shaping theory of writhed blade in streamline design, the geometric shape of blade is designed and then computational formulas for the dynamic design of the fan with writhed blades in gas-particle two-phase axial-flow are derived with the two-phase continuum coupling model. Concurrently, the correlation between the structure of impeller and flow-field dynamic functional parameters is presented. Further, the software for the optimization design of the gas-particle two-phase axial-flow fan with writhed blades is obtained. By means of the available software, a sample fan is formed, and its all dynamic characteristic curves and its geometric shape are presented. Finally, the conclusion on the effect of particles on fan running is reached quantitatively and qualitatively, as is expected in the fan industry.

Design of Off-statistics Axial-flow Fans by Means of Vortex Law Optimization

Off-statistics input data sets are common in axial-flow fans design and may easily result in some violation of the requirements of a good aerodynamic blade design.In order to circumvent this problem,in the present paper,a solution to the radial equilibrium equation is found which minimizes the outlet kinetic energy and fulfills the aerodynamic constraints,thus ensuring that the resulting blade has acceptable aerodynamic performance.The presented method is based on the optimization of a three-parameters vortex law and of the meridional channel size.The aerodynamic quantities to be employed as constraints are individuated and their suitable ranges of variation are proposed.The method is validated by means of a design with critical input data values and CFD analysis.Then,by means of systematic computations with different input data sets,some correlations and charts are obtained which are analogous to classic correlations based on statistical investigations on existing machines.Such new correlations help size a fan of given characteristics as well as study the feasibility of a given design.

有限空间内电子芯片风冷系统的优化研究

芯片的冷却问题已经成为限制电子设备发展的技术瓶颈之一。本文通过数值模拟,对某人脸识别电子芯片在有限空间内的散热问题展开优化研究。研究芯片温升与轴流风扇流量、进风面积、芯片工作功率的关系,并通过多目标优化得到更加符合当前目标需求的芯片及风扇的工作参数。研究结果表明,轴流风扇流量从0增加到9CFM范围内,芯片温升下降约56%;风扇进风面积从0.031 m^(2)增大到0.196 m^(2),芯片温升上升13%;随着芯片功率增加,芯片稳定工作的温升呈线性提升。通过多目标优化设计,得到的芯片及风扇的工作参数为P=5.87 W,Q=1.056 CFM,A=0.041 m^(2)。

带下表面射流的超临界翼型优化

为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行数值模拟分析。研究发现,在上翼面存在激波的情况下,下表面射流在增大翼型升力的同时也增大了波阻。提出下表面射流伴随优化进程的射流翼型一体优化思路。采用基于Kriging代理模型的优化方法,以最大化升阻比为目标,对RAE2822翼型分别进行了基准外形优化和带下表面射流(cμ=0.0002)的翼型优化。结果表明:在Ma=0.73、Re=6.5×10^(6)、α=2°的工况下,相较于基准翼型,下表面射流翼型等效升阻比提高了4.9%,下表面射流优化翼型等效升阻比提高了26.2%。带下表面射流翼型的射流翼型一体优化设计方法,能够显著提高超临界翼型的等效升阻比,研究结果有助于下表面射流的应用研究。

采用仿海鸥翼型叶片提升轴流风机气动性能的研究

为提升轴流风机的气动性能,受到具有良好滑行飞行性能的海鸥翅膀独特的翼型结构的启发,本文研究通过提取海鸥翅膀特定截面位置处的翼型结构应用于轴流风机的叶片设计中,考察了叶片仿生设计对空调器用轴流风机气动性能的影响。首先采用数值计算方法求解定常流动雷诺时均Navier-Stokes方程,对仿海鸥翼型叶片的轴流风机的气动性能及其内部流场进行分析,然后采用大涡模拟方法和FW-H声类比方法对轴流风机的气动噪声进行数值预测。结果表明:在相同的设计转速下,仿海鸥翼型叶片的轴流风机的气动效率提高了3.1%;在相同风量条件下,仿海鸥翼型叶片的轴流风机的噪声相比于原型风机降低了约1.0dB(A)。采用仿海鸥翼型叶片,风机叶片表面的静压分布均匀,叶片中段的压力脉动明显减少。同时,在风机进口轮毂处和叶顶区域,流动分离被抑制,叶片尾迹涡脱落引起的气流脉动和气流不均匀性相对减弱,这就有效提升了轴流风机的气动性能。

基于小波变换的轴流风扇2阶叶频噪声机理分析及叶型优化方法研究

为了研究空调室外机轴流风扇2阶叶频噪声产生来源和抑制方法,采用大涡模拟仿真,结合能谱分析和小波分析方法,识别影响2阶叶频噪声的典型流场位置和流动结构,对风扇叶型优化设计方法进行研究和试验验证。结果表明,2阶叶频噪声主要受风扇与周围部件的间隙及叶尖出口区域流动的影响,通过增加风扇与隔板间隙9 mm,即可降低2阶叶频噪声6 dB;针对风扇的优化设计方法,前加载叶型可显著降低2阶叶频噪声,而通过调整周向积叠线,可将不同叶高区域2阶叶频噪声相位差控制在π/3,从而抑制幅值叠加,实现降低2阶叶频噪声6.7 dB。研究结果可为空调室外机轴流风扇的叶频噪声优化提供技术参考。

基于遗传算法的轴流风机气动性能分析及优化研究

为降低风机气动噪声,以某轴流风机为研究对象,基于遗传算法,提出一种将叶片表面湍动能最小值作为寻优目标的降噪方法,并对优化后的叶型降噪机理及气动性能进行了分析。首先,通过对叶片结构参数化建模,实现了空间尺寸、形状的自动控制。其次,将风量不变作为约束目标,选取3个结构参数,即轴向弯曲参数、前缘点和后缘点的切线与弦线的夹角,结合敏感因子分析,建立叶片表面湍动能和叶片结构参数的响应关系。最后,利用NSGA-Ⅱ遗传算法确定最优的叶片结构,并对比了优化前后气动性能和噪声水平的差异,验证了该方法的可行性,结果表明:(1)不同的轴向弯曲形状对风量和噪声的影响权重不同;(2)选取了两种优化方案:叶片#1通过降低转速可以实现降噪,且保证风量和原始叶片持平;叶片#2相较于原始叶片风量基本持平,在保证转速不变的前提下最大降噪量达1.6 dB(A);(3)通过试验验证发现,风量对噪声的影响大于转速,在保证风量不变的前提下,通过叶型降噪的效果要优于降低转速的方案。

轴流泵站蜗壳形进水池的优化设计及研究

文章以轴流排涝泵站为例,采用数值模拟方法,对蜗壳形进水池进行优化设计及研究。针对蜗壳形进水池的安放角、偏心距及螺旋线螺旋角3个主要参数,分析了各参数对泵站水力性能及水泵入口流速分布均匀性的影响。研究结果表明:安放角对泵站性能影响较大,需对电机功率进行复核,防止过载;偏心距为0时,水力性能最优;螺旋线形状对泵站性能影响较小,但较小的螺旋角有利于提高水泵入口流速均匀性。

A novel approach for the design of axial flow fan by increasing by-pass ratio in a constantdiameter turbofan

The present study introduces an innovative aerodynamic redesign of an axial flow fan based on constant diffusion factor and radial equilibrium.All input design parameters such as mass flow rate,hub to tip ratio,aspect ratio,tip diameter and angular velocity are taken from NASA Rotor 67 as a conventional axial flow fan.A computer program is developed to extract the three-dimensional geometry of a fan and to estimate the span-wise distribution of parameters.The new designed fan flow field is investigated in detail by CFD tool at both design and off design conditions.Finally,a turbofan cycle analysis is conducted based on thermodynamic and gas dynamic principles to evaluate the fan performance in a turbofan engine in comparison to NASA Rotor 67.Achieving a higher total pressure ratio,meeting the target pressure ratio in lower rotational speed with higher efficiency,delivering more bypass air in a constant diameter and less fuel consumption for the same specific thrust force are the main advantages for the new design strategy in comparison to the conventional designed fans such as Rotor 67.However,efficiency reduction in fan over speed is the main disadvantage.

多级轴流压气机末级串列静子三维优化设计与分析

为充分挖掘串列叶片对压气机扩稳增效的潜能,在对多级轴流压气机末级静子串列改型的基础上,选取不同叶高处前后排叶片相对位置、负载分配、弯掠特征及端壁轮廓等25个参数为设计变量,开展某工业用6.5级轴流压气机末级串列静子叶片与端壁的一体化优化设计研究,并采用随机森林方法对串列叶片几何参数进行特征重要性分析,提炼出串列参数设计指导。结果表明:优化后压气机末级在设计工况、近喘工况和近堵工况下的绝热效率分别提升4.81%、3.37%和8.195%;对于末级串列静子,最优串列参数随叶高变化而变化;调整前后叶片的弦长比与弯角比以实现串列叶片负荷前加载、调整叶片后掠与反弯以降低叶片端壁处负荷、设置叶中部分更大的周向交错度使缝隙区流体充分加速,均能有效降低末级串列叶片流动损失;串列叶片缝隙区尺寸,尤其是周向交错度,较其他参数对串列叶片性能的影响更为显著。研究成果应对压气机三维串列叶片设计具有参考价值。

基于熵产理论和响应面法的轴流式止回阀结构优化设计

为了优化轴流式止回阀结构,从而提高其流通性能,提出了一种基于熵产理论结合响应面法的轴流式止回阀结构优化设计方法,并对DN100轴流式止回阀进行了优化设计和分析。以最小熵产为目标,采用Plackett-Burman试验、最陡爬坡试验和Box-Behnken响应面试验得到最优结构参数,并对优化前后轴流式止回阀进行熵产和流场分析。结果表明:最优结构参数为入口角33.4°、阀瓣宽24.4 mm和阀芯尾角25.0°,响应面法预测准确且优化效果显著。湍流耗散熵产是造成轴流式止回阀能耗较大的主要原因,其主要发生在喉口后端和阀瓣边缘附近,优化后其数值大小和分布范围明显减小。优化前轴流式止回阀喉口后端、阀瓣边缘处和阀芯尾部存在较多漩涡,优化后漩涡显著减少,阀芯上分离点明显后移,流通性能更好。本研究为轴流式止回阀结构优化设计提供了新思路。

采用动态交互作用分析的叶轮机械优化算法研究

针对当前基于代理模型的优化算法因遭遇“维度灾难”而难以开展叶轮机械高维优化的难题,提出了自适应厘清变量间关系的动态聚合全局优化算法。该算法能在不消耗额外样本的条件下获取设计变量间的交互信息,并基于该信息一方面将高维问题分解为多个低维问题,实现高维问题的高效优化,另一方面为后续知识挖掘提供信息基础。在完成典型30维函数算例测试后,利用所提出的算法完成了包含28个设计变量的Rotor 37叶栅气动优化与设计空间知识挖掘。结果表明,优化后,Rotor 37叶栅设计工况效率相对参考设计提高了1.69%,且变工况性能相对参考设计亦有不同程度提高。在获得最优解的同时,所提出的算法还厘清了Rotor 37叶栅设计空间各变量间交互作用关系。进一步,结合算法所揭示的变量交互作用进行知识挖掘与CFD验证,证明对分离线附近型线进行微调可有效降低激波与边界层相互作用,从而提高跨声速叶栅的气动性能。由此,所提出的算法在求解高维大资源叶轮机械优化设计问题上的适用性和有效性得到验证。

轴流压气机跨音叶型前缘优化设计

叶型前缘的几何外形直接影响轴流压气机的综合气动性能,为了研究前缘椭圆度的最佳区间变化规律,对跨音叶型Stator35叶中截面进行了优化设计。基于参数化方法和元启发式算法建立了叶型前缘椭圆度的寻优模型,探讨了圆形和椭圆形前缘叶型的气动性能,对比分析了多种椭圆度前缘叶型的流场结构,并对椭圆前缘三维叶片的几何外形进行了气动寻优。结果表明:椭圆度前缘叶型在全工况范围内降低了总压损失系数,拓宽了3°攻角,提升了落后角和折转角性能;跨音叶型椭圆前缘设计存在最佳椭圆度区间[0.8,0.9],并且转捩点位置距前缘距离与分离泡长度负相关;优化后设计点处椭圆前缘叶片的绝热效率提高了0.4%,且在全流量范围内绝热效率均高于原始叶片,喘振裕度从9.8%提升到12.4%。

动叶可调轴流式风机叶片全三维气动优化方法研究

本文以某电厂660MW机组的动叶可调轴流式送风机和引风机为例,重点讨论了深调负荷下,定制化设计风机叶型的方法。根据风机现有运行情况及风机本体特性,确定了风机优化目标,通过五个步骤时风机叶型进行定制化设计并予以实施,性能测试结果说明改造后风机性能可以达到预期的效果,同时改造费用和工程量均为最低。本文对定制化叶型从选型、设计到实施后评估的全过程进行了详细描述。同时对此改造过程中出现的问题进行了分析讨论,也提出了设计定制化叶片需要关注的问题。

基于航空技术的轴流风机CFD智能仿真优化

利用航空技术对空调用轴流风机进行CFD仿真,建立了可灵活快速变形的轴流风机参数化模型,通过研究不同转速、风量、压力等工况条件下不同风机设计参数对轴流风机性能的影响,形成了一套适用于实际生产设计场景中的轴流风机智能优化平台,并对某型号风机在22000m3/h流量的工况下的性能进行优化设计。优化后模型效率提升明显,其静压效率由35.3%提高至40.8%,全压效率由59.6%提高至65.7%。

Optimization design of airfoils under atmospheric icing conditions for UAV

Natural ice accretion on the lifting surface of an aircraft is detrimental to its aerodynamic performance, as it changes the effective streamlined body. The main focus of this work considers the optimization design of airfoils under atmospheric icing conditions for the Unmanned Aerial Vehicle(UAV). The ice formation process is simulated by the Eulerian approach and the three-dimensional Myers model. A three-equation turbulence model is implemented to accurately predict the stall performance of the iced airfoil. In recognition of the real atmospheric variability in the icing parameters, the medium volume diameter of supercooled water droplets is treated as an uncertainty with an assumed probability density function. A technique of polynomial chaos expansion is used to propagate the input uncertainty through the deterministic system. The numerical results show that the multipoint/multiobjective optimization strategy can efficiently improve both the ice tolerance and the cruise performance of an airfoil. The reason for the focus on robust optimization is that the ice angle of the optimized airfoil becomes less critical to the incoming flow.The optimized airfoils are applied to a UAV platform, in which the performance improvement and the relevant key flow feature are both preserved.