基于Bezier曲线的卷曲水草模拟

水生植物的模拟一直是计算机图形学研究的热点和难点。对于叶片较长且卷曲的水草仿真,采用Bezier曲线生成叶片的主脉(中线)及边缘曲线,通过偏移中线或边缘曲线上的控制点进行曲线插值生成侧中线,采用三角化方法生成叶片框架的网格,直接使用多重纹理产生叶子上的暗斑。实验结果表明,该方法能较好地表现水草的形态并有较高的绘制效率。     

基于闭合B样条插值的汽轮机叶片测量路径规划

如何根据汽轮机叶片型面模型的理论数据点及测量路径约束条件,准确获取实际测头位置是叶片型面测量的关键所在。在已知汽轮机叶片型面模型设计型线理论点的情况下,提出了采用闭合B样条插值法求叶片型面理论曲线,并采用拟追赶法反求B样条插值曲线控制顶点的基于闭合B样条插值的汽轮机叶片测量路径规划模型及其相应算法。数据表明,测量路径符合叶片曲率变化,且路径变化在景深范围内,可以很好地满足高精度叶片型面的测量要求。     

关于采用复合型线的圆柱型叶片的研究

本文作者介绍了以两种不同类型的曲线合成圆柱型叶片型线新方法，这种复合曲线的包角值和安放角具有较为理想的分布规律，从而将改善柱形叶片性能。     

离心泵叶轮内流体流动的有限元分析

应用有限元法,在二维、定常、不可压缩理想流体的假设下,对离心泵叶轮内流体的流动进行了分析,给出了叶片表面相对速度分布曲线及其压力分布曲线,反映了流体在叶片二侧相对运动及压力分布的不均匀性．     

滚柱叶片式双定子多速马达的原理与实验验证

为了解决双定子多速马达叶片尖端对内、外定子曲线的磨损及径向间隙补偿的问题,提出了一种新型的滚柱叶片式结构,该结构将叶片尖端与定子曲线间的滑压变为滚压,并依靠工作中产生的离心惯性力与液压力,将滚柱分别与内、外定子曲线压紧,形成密封容积。对4种不同工况下的双定子多速液压马达进行了受力分析,同时搭建实验台对双定子多速马达样机进行了测试。结果表明,滚柱叶片式结构能够在实现滚压的同时保持容积效率,转移了叶片尖端与定子曲线间的矛盾,为双定子多速液压马达的设计提供了一个新的思路。     

离心泵叶片的三维造型及优化

利用NURBS方法对离心泵叶片进行建模,建立了离心泵叶片的空间样条曲线,并应用类流线方法对叶片进行优化,使叶片在保持原有形状的基础上更为光滑。结果表明,利用该方法建立的模型,可以真实完整地反映叶片的形状,优化后的叶片表面的褶皱和凹凸消失,为叶片的性能分析、数控加工等工作提供了方便。     

水泵叶轮的自动编程和数控加工

通过合理选择参变量,建立了叶片曲面的数学模型。文中采用等误差法,用直线去逼近刀具中心规迹曲线。并将边界面的法向等距面与叶片上各曲线的刀具中心规迹的交点,作为终止点,保证了叶片曲面与边界面的光滑连接。笔者完成了叶轮的数控加工并对数控加工工艺作了初步的探讨。     

S形叶片空气阻力系数的仿真计算

为确定双叶片立轴风力机的性能参数,根据S形叶片结构和运动特点,建立S形叶片与流场的有限元模型,对给定位姿叶片周围的流场进行CFD仿真计算与分析,揭示S形叶片周围流场的速度和压力分布规律.基于叶片迎风面和背风面的压力分布曲线,给出叶片凹、凸面的空气阻力系数的计算方法.根据模拟结果对不同风速下叶片凹、凸面的空气阻力系数进行...     

耐寒植物叶片比热参数的测定

采用DSC差式扫描量热仪测定不同温度下耐冬(Common Camellia)、大叶冬青(Ilex latifolia Thunb.)和碧玉(Fes.Rub.cv.Jas.)3种植物叶片的比热容,并得到不同温度范围内叶片比热容与温度间的近似关系式。通过对比分析比热容曲线得出结论:耐寒植物叶片比热在-4~0℃温度范围内快速增长,在0℃达到峰值,在0~2℃温度范围内急剧下降,随后比热容随着温度升高而小幅度上升;虽然耐寒植物叶片比热容曲线相似,但不同耐寒性植物叶片其比热容峰值差异较大;非耐寒植物叶片的比热容在生长温度范围内呈二次函数关系平缓增加。     

高压叶片泵的三种类型叶片受力分析

针对叶片泵的各种类型叶片受力特性不同的问题，以无厚叶片、顶部为圆弧的单面后倾叶片及对中圆弧叶片三种类型为例，对吸油区的叶片受力进行分析建模，仿真得到一系列叶片所受接触反力的变化曲线。结果表明：忽略叶片厚度得到的结果与实际情况有很大的差异，顶部有圆弧的叶片比单面后倾叶片受力状况要好。     

离心泵双圆弧圆柱形叶片的几何方程

介绍了一种离心泵双圆弧圆柱形叶片的几何作图方法。推导了这两段圆弧的直角坐标方程和极坐标方程,该方程以离心泵叶片基本参数（内、外半径、叶片包角及进、出口安放角）为变量。通过计算实例验证了该方法的准确性及相关公式的正确性。探讨了两段圆弧半径、圆弧上各点安放角随作图参数α变化的规律。分析表明:在该参数取60°时,本几何作图法所得到的叶片叶轮有较高的水力效率。该方法不需要根据经验多次调节圆弧的半径,也不需要进行数值迭代计算。     

UG技术在低比转速叶片设计中的应用

圆柱形叶片广泛应用于低比转速叶轮,本文作者以UG技术对常用的圆柱形叶片进行了造型,从而有利于帮助设计人员及时、直观地发现叶片的水力特性和机械特性,可以看出将UG技术引入叶片水力设计领域,将对提高叶片性能产生积极的重要影响。     

风力机叶片二元翼段静气动弹性机理

针对风力机叶片翼型静气动弹性的发散速度、载荷重新分布等问题,在线弹性范围内,基于气动弹性力学理论,推导出适用于风力机叶片二元翼段静气动弹性的基本方程.以攻角为输入量,压力为输出量,翼型的弹性扭角为系统的反馈量,建立了风力机叶片弹性翼型的气动弹性反馈模型.在危险风速工况下,对3种典型翼型的风力机叶片二元翼段进行了计算分析,得到了扭转刚度、刚心与气动中心距离对风力机叶片二元翼段的发散速度、附加扭角和升力分布的影响.研究了不同翼型对风力机叶片二元翼段附加扭角和升力分布的影响,结果表明,当扭转刚度较小时,附加扭角的增加在一定程度上提高了翼型的气动性能;当扭转刚度较大时,附加扭角增加较小,对翼型的气动性能影响较小.     

Effects of blade rotation angle deviations on mixed-flow pump hydraulic performance

By model test and numerical simulation,this paper analyzed the effects of different blades with varying rotation angle deviations on the hydraulic performance of a mixed-flow pump.It was found that when some blades had rotation angle deviations,the hydraulic performance curves of the mixed-flow pump would move.With a positive deviation,the curves moved towards the large flow rate;with a negative deviation,the curves moved towards the small flow rate.When some blades had rotation angle deviations,the symmetry and uniformity of the pressure distribution inside the mixed-flow pump flow passage both decreased;the larger the deviation,the greater the decrease.When a single blade had a large rotation angle deviation,a rather clear low pressure area was formed,lowering the cavitation performance.When two adjacent blades changed simultaneously,under the small flow rate condition,adverse pressure gradient and flow separation occurred in the flow field,and a hump appeared in the head curve and the operation stability of the mixed-flow pump dropped significantly.Near the best efficiency point(BEP),the simultaneous change of two alternate blades produced a more significant change of pressure in the flow passage,with an even larger area.Compared to the effect of two adjacent blades,two alternate blades,when changed simultaneously,made the mixed-flow pump slightly less efficient,but with a flatter efficiency curve and relatively wider high efficiency area.By fitting the test results,a functional relation among the BEP of the mixed-flow pump QBEP,the number of deviated blades N,and blade rotation angle deviationαwas established,thus realizing an effective prediction of the BEP of the mixed-flow pump when blade rotation angles have deviations.By model test and numerical simulation,this paper analyzed the effects of different blades with varying rotation angle deviations on the hydraulic performance of a mixed-flow pump.It was found that when some blades had rotation angle deviations,the hydraulic performance curves of the mixed-flow pump would move.With a positive deviation,the curves moved towards the large flow rate;with a negative deviation,the curves moved towards the small flow rate.When some blades had rotation angle deviations,the symmetry and uniformity of the pressure distribution inside the mixed-flow pump flow passage both decreased;the larger the deviation,the greater the decrease.When a single blade had a large rotation angle deviation,a rather clear low pressure area was formed,lowering the cavitation performance.When two adjacent blades changed simultaneously,under the small flow rate condition,adverse pressure gradient and flow separation occurred in the flow field,and a hump appeared in the head curve and the operation stability of the mixed-flow pump dropped significantly.Near the best efficiency point(BEP),the simultaneous change of two alternate blades produced a more significant change of pressure in the flow passage,with an even larger area.Compared to the effect of two adjacent blades,two alternate blades,when changed simultaneously,made the mixed-flow pump slightly less efficient,but with a flatter efficiency curve and relatively wider high efficiency area.By fitting the test results,a functional relation among the BEP of the mixed-flow pump QBEP,the number of deviated blades N,and blade rotation angle deviationαwas established,thus realizing an effective prediction of the BEP of the mixed-flow pump when blade rotation angles have deviations.     

Turbocharger Noise Prediction Using Broadband Noise Source Model

The noise prediction of the turbocharger is studied. The broadband noise source model is employed to predict the near-field noise of the turbocharger. The 3D software Solidworks is adopted to establish the model blades and inlet of turbocharger compressor, then this 3D model is introduced into the software CFD to calculate the flow-field under different inlet shapes, different blades shapes and different clearances between casing and impeller. On the base of the above simulation, the broadband noise source model is employed to calculate and analyze the near-field noise. The calculation shows that compressor static pressure values and the sound power values near the impeller outlet are the largest. Through the noise calculation by using broadband noise source model under different inlet shapes and blade shapes, we find that the noise level of the inlet of cylindrical and cone types are smaller. Compared with the current widespread used backward skewed or radial blades, there is little difference of the noise value of the inlet of the forward skewed blades.     

圆柱齿轮螺旋角的精密测量

介绍利用直线和圆感应同步器测量圆柱齿轮螺旋角的原理和方法,通过计算机数据处理系统可以精确测量和计算出被测圆柱齿轮的螺旋角．     

直升机桨叶动平衡试验中的稳定性分析

直升机标准桨叶的动态特性参数通过动平衡试验来校准,为了确定标准桨叶动平衡试验参数,利用叶素理论,把桨叶的挥舞角分解到二阶小量,建立了动平衡试验中孤立桨叶的带三次非线性项的Duffing型挥舞运动方程,用解析的Melnikov函数方法分析Duffing型挥舞方程对风速的稳定性阈值.把桨叶Duffing型挥舞方程与只精确到一阶项的挥舞方程进行数值比较,仿真试验表明在环境风速增大和桨叶挥舞角增大时二者误差变大,并通过仿真试验分析确定了满足标准桨叶动平衡试验的环境风速条件,实测结果与法国直升机桨叶动平衡试验环境风速的技术参数要求很接近.结果表明在动平衡试验中标准桨叶的挥舞对于环境风速是稳定的,并确定了标准桨叶动平衡试验环境的风速范围要求.     

攻角对螺旋桨非定常特性的影响分析

为了分析入流速度攻角的连续变化对螺旋桨非定常特性的影响,应用滑移网格技术对螺旋桨运动进行了数值分析。结果表明:螺旋桨的时均拉力会随攻角的增大而增加;对于各单独叶片而言,向下运动时,随着攻角的增大,拉力会逐渐增加,向上运动时,拉力则会减小;在特定方位角时,随着攻角的增大,桨叶前端的轴向速度会略微增大,桨叶后端的轴向速度在小攻角时也会发生略微的变化,但在攻角较大时变化较明显;随着攻角的增大,桨叶所受到的周期性非定常载荷的波动会逐渐加剧。     

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。     

极端运行阵风下后掠型风力机叶片的气动特性研究

基于多体系统动力学和升力线气动模型,考虑柔性后掠叶片动态失速和气动弹性耦合问题,建立了风力机气弹耦合模型,研究极端运行阵风及阵风作用时间对某5 MW后掠风力机叶片气动性能的影响。结果表明：极端运行阵风对叶根挥舞力矩、功率、攻角、升力系数和轴向推力等气动特性具有较大影响。研究工作对风力机的结构优化设计和疲劳寿命设计具有重要作用。