基于叶片载荷分布的离心泵叶轮水力性能优化

载荷分布是三元反问题设计中的关键参数,为分析叶片载荷分布规律对离心泵叶轮水力性能和气蚀性能的影响,采用软件CFX对叶轮a、b和c 3种不同叶片载荷方式的离心泵叶轮内流场进行数值模拟。由分析结果可知:不同叶片载荷对离心泵叶轮外特性存在较大影响,外特性性能最好的是叶轮b,但其吸力面进口处静压值最小,外特性性能其次的为叶轮a,其吸力面进口处静压值最大,所以在兼顾离心泵叶轮效率与气蚀性能的条件下,优化出最佳载荷分布方式为叶轮a,即外特性和气蚀性最好,在其最佳载荷的基础上对其载荷分布再次进行优化可知:叶轮a-3的载荷分布水力性能和气蚀性能较好。分析结果为离心泵叶轮三元反设计提供一定参考。     

Novel method for operating characteristics test of a hydraulic pump

The traditional testing method of a hydraulic pump requires a large amount of test data from a variety of pump working conditions. The test is usually time-consuming and energy-consuming. And the accurate characteristic curves of the pump were hardly obtained due to a limited amount and discreteness of the test data.In order to simplify the test procedure and improve the test accuracy,a novel method for measuring hydraulic pump operating characteristic based on multi-element nonlinear regression( NLMR) modeling is proposed in this paper. The main idea of this modeling method is establishing a mathematical model to predict the performance parameters of the hydraulic pump,only a small amount of test data is needed. Consequently,the pump operating characteristics in any working conditions are obtained. And the test results of the pump are easily characterized in the graphs,charts,tables and so on. The evaluations of the model are carried out and discussed in this paper. The result shows that the test error of the novel method can be controlled to be about 0. 1%. Compared with the traditional test method,the proposed method reduces greatly the test time and the random error of the test data,and improves the efficiency and accuracy of the pump test.     

叶片积垢对压气机性能衰退的影响

空气中的粉尘、微粒容易随空气进入压气机,导致叶片、通道壁面等表面粗糙度增大,降低部件的效率和流通能力,进而影响整机性能。通过对某1.5级轴流压气机进行三维CFD数值模拟,采用基于表面粗糙度与随机尺寸的积垢模拟方法,对积垢造成压气机性能衰退的机理进行对比分析,得到积垢后压气机的效率、压比、轴向力的衰退与转速的关系,以及压气机积垢后的流场变化情况。研究结果可为确定压气机清洗周期和预防叶片积垢提供借鉴。     

Experimental study of the effect of blade tip clearance and blade angle error on the performance of mixed-flow pump

The hydraulic performance test of the mixed-flow pump has been carried out through selecting different blade tip clearances and various blade angle errors.The ratio of the mixed-flow pump efficiency reduction and the blade tip clearance variation(η/δ) varies with the flow rate coefficient revealing a parabolic trend.An empirical equation has been developed for the mixed-flow pump model by parabolic fitting.For the same blade tip clearance variation δ,the mixed-flow pump efficiency reduction η increases rapidly as the flow rate rises.For any given flow rate,the efficiency,the head and the shaft power of the mixed-flow pump all decrease with the increase of the blade tip clearance.Among them,the efficiency reduction η varies approximately linearly with the blade tip clearance variation δ.When the angle of an individual blade of the mixed-flow pump has a deviation,the performance curves will move and change.These curves have consistent change directions with the performance curves under the condition of all the blades rotated at the same time,but have smaller offset and lower range of variation.When an individual blade angle error changes to ±2°,the optimal efficiency of the mixed-flow pump will have no significant difference.When the individual blade angle error increases to ±4°,the optimal efficiency will decrease by 1%.     

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine（S-VAWT） appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.     

混流泵叶片角对泵性能的影响

根据对已有试验成果的分析,提出了混流泵叶片角对效率、轴功率系数、叶轮出口液流角、阻力系数和摩擦系数等有关性能参数影响的表达式,为进一步研究混流泵性能提供了理论基础。     

风机叶片设计二次开发与气动性能仿真

为了提高叶片设计的精度和效率,根据风机叶片设计的相关理论和方法,对叶片气动外形设计进行研究.以20 kW风机叶片为例,在Wilson法的基础上,利用VB、VC++等编程语言在SolidWorks平台上开发叶片气动外形设计及建模的应用系统.根据输入的设计参数自动生成叶片的三维实体模型,省去了以往设计过程中生成的大量数据的转换和存储,实现叶片的高效,智能化设计.为了对设计结果进行评估,同时验证设计的有效性,针对设计好的叶片模型进行流场仿真分析.结果表明,提出的叶片设计与建模方法能够有效提高风能利用率,缩短风机叶片设计周期,可用于企业对叶片的设计研发,并为叶片结构有限元分析和优化设计平台奠定基础.     

喷嘴偏心距对射流泵性能影响的数值模拟

对射流泵内部流动进行了数值模拟,计算了射流泵在不同喷嘴偏心距下的性能参数,分析了射流泵喷嘴轴线偏离泵体轴线的偏心距对其性能和流场的影响.结果表明:喷嘴偏心距对射流泵大流量比工况的性能有较大的影响,而对小流量比工况影响较小,可忽略不计;随着偏心距的增加,射流泵效率最高点下降并向流量比小的方向移动.在工程应用中,射流泵同轴度精度要求可以定为12级以上.     

叶片周向弯曲角度对扩压叶栅气动性能的影响

为了改善扩压叶栅气动性能,采用拟压缩性方法对不同周向弯曲角度的正弯曲叶片压气机叶栅内三维粘性流场进行了数值模拟.结果表明,随着弯曲角度的增加,端部流动状况逐渐得到改善,叶栅中部流动损失逐渐增加.正弯20°时可基本控制端部扩压因子至0.6以下.叶片弯曲角度的选择应以能满足设定目标的最小角度为最佳,过大的角度将会导致动静叶间匹配困难和较大的吸力面尾缘回流区     

射流泵性能的数值计算

采用贴体坐标变换技术 ,结合混合有限分析法和k-ε紊流模型 ,用数值方法计算了射流泵的宏观性能 .结果表明 ,该方法的计算结果与现有理论及实验值吻合较好 ,其精度可满足工程实际要求 ,可用于替代射流泵的性能试验 .     

角钢耗能自复位混凝土框架节点的耗能性能

提出角钢耗能自复位混凝土框架设计方法，建立节点的有限元数值模型，并试验验证其有效性。对抗弯承载力比φdes预应力筋不同的节点进行模拟分析，研究其在地震作用下的自复位性能、耗能能力和材料损伤等性能指标。为提高该类节点耗能能力，通过改变角钢竖肢螺杆标距做进一步研究。结果表明：角钢耗能节点具有良好的自复位性能，但耗能能力不足；减小抗弯承载力比φdes，自复位能力降低、残余变形加大，但耗能能力增强。与混合连接节点相比，应适当降低节点抗弯承载力比φdes的最低取值，以弥补其耗能能力的不足。角钢竖肢塑性变形是节点的主要耗能方式，且集中在竖肢的螺栓孔高度和竖肢转角位置；减小竖肢螺杆标距，且保持材料其他参数不变，将导致抗弯承载力比φdes减小、截面抗弯承载力提高，节点耗能能力将随之增强。     

液压泵气穴故障分析

文章分析了液压泵产生气穴的原因,指出了检测与判断方法,提出了预防措施,并给出典型故障实例.     

混流式粮食烘干塔动态热力信号系统特性分析

建立了混流式粮食烘干塔动态热力模型,利用实际运行记录验证了该模型的正确性;详细分析了影响烘干塔出口粮食水分的关键因素,指出热风温度和原粮水分的变化影响较大,而环境温度和原粮温度则影响较小。建立的粮食烘干过程信号系统优化模型为烘干塔的自动控制奠定了基础。     

转向泵性能测试软件的研究

介绍了转向泵性能测试软件的设计思想、实现方法．分析了数据采集及数据处理的方法．该软件具有实时显示、自动测试、实时采集并自动记录实验数据的功能．经使用证明,该软件界面友好、功能齐全、测试数据准确可靠、使用方便．     

液力减速器叶片前倾角度三维集成优化

为了对液力减速器叶片前倾角度进行参数优化,建立了液力减速器叶栅参数三维集成优化仿真平台。以叶片倾角为设计变量,三维CFD分析作为求解器进行试验设计,并根据试验样本结果构建响应面法模型(RSM)进行优化,得到一套最优的动、定轮叶片倾角参数。就叶片倾角参数对液力减速器内流场特性、制动外特性的影响进行了分析,并结合试验数据对优化前后制动性能进行了对比。结果表明,优化仿真平台精度较高,结果可信。优化后的液力减速器制动性能显著提高。     

自吸旋涡泵的试验研究

在25WZ1-12型样泵型式试验基础上,得出旋涡泵外特性曲线。利用计算流体动力学（CFD）原理,基于雷诺时均方程和k-ω双方程湍流模型,获取自吸旋涡泵内部流场数值模拟分布状况。通过对比分析数值模拟和试验结果,阐明旋涡泵抽吸及扬程形成原理、汽蚀性能特点和自吸过程。     

射流泵内流场的大涡模拟

阐述了二维弱可压缩流体流动控制方程和大涡模拟湍流模型.基于该模型对射流泵各种运行工况进行了一系列数值模拟计算.计算中模拟了异常边界条件下射流泵的流场特性,重点模拟喷嘴出口回流旋涡并给出了可视化描述.对不同计算网格数和大涡模拟系数对计算结果的影响也作了论述.提出的网格生成和数值模拟方法具有较高的效率,计算结果可靠.     

液力变矩器叶片三维成型法及其性能分析

探讨了液力变矩器叶片三维成型方法,提出了叶片三维成型方法的基本设计流程。通过对不同参数变化规律生成的泵轮、涡轮、导轮的叶型进行对比分析,总结出液力变矩器叶片角变化对液力变矩器性能影响的基本规律。通过CAD/CFD技术完成叶片的设计和相应变矩器性能的计算。同时,通过与作为基型的W305型液力变矩器的比较,证明了研究结论的可靠性。     

Tests and numerical simulation on curved blade of super-critical adjust stage

Tests and numerical simulations of super-critical adjust stage blade were carried out and the effect of bowed blade on flow characteristics and the secondary flow were analyzed. The simulation and test results show that the adjust stage blade with aft-loading and big front-edge radius has good flow characteristics by meridian shrink. The numerical studies were carried out with software of NUMECA in order to investigate the aerodynamic characteristics of adjust stage blades,which include prototype blade(tested blade) ,positive curved blade (15°) and negative curved blade(-15°) . The simulation results show that the positive curved blade forms a negative static pressure gradient in the lower region of the cascade along the blade height and a positive static pressure gradient in the upper region. This leads to the reduction of the streamwise vortices intensity and the aerodynamic load on both sides of the blade and the endwall. Therefore,the crosswise secondary flow losses of endwall can be decreased considerably.     

液压系统液压脉动研究

液压脉动研究是液压系统动态特性分析计算中最重要部分.液压脉动对液压系统是非常有害的,不仅使系统的动态特性变劣,甚至产生共振或谐振使系统元件损坏造成事故.揭示液压脉动的变化规律,改善系统的动态性能,消除或减少压力脉动幅值,对系统的建设和使用有特别重要的意义.该论文在液压传输线理论基础上运用频率法和液电比拟法研究系统,采用理论和试验推导相结合建立数学模型,设计了液压脉动分析计算程序,并进行了实例仿真,得出了系统的振动频率及脉动压力和流量,仿真结果与试验数据很吻合,证明研究方法的正确性和可行性,具有较高的实用价值.