不同叶型双循环圆液力缓速器制动性能与流动特性对比分析#br#

为比较不同叶型双循环圆液力缓速器制动性能,开展了弯叶片与不同倾角直叶片液力缓速器的制动性能研究。对各叶型缓速器内流场进行三维数值模拟,获取了不同转速全充液工况下的制动力矩曲线,得到循环流道速度场、压力场、湍流动能分布状态以及空转工况下的空损功率曲线,并进行对比分析。分析结果表明,数值计算方法具有较高精度,弯叶片双循环圆液力缓速器有良好的制动性能,有利于保证缓速器叶片的强度与刚度,且空损较小。     

Experimental and computational studies on flow behavior around counter rotating blades in a double-spindle deck

Experimental and computational studies were performed to determine the effects of different blade designs on a flow pattern inside a double-spindle counter rotating mower deck. In the experimental study, two different blade models were tested by measuring air velocities using a forward-scatter LDV system. The velocity measurements were taken at several different azimuth and axial sections inside the deck. The measured velocity distributions clarified the air flow pattern caused by the rotating blades and demonstrated the effects of deck and blade designs. A high-speed video camera and a sound level meter were used for flow visualization and noise level measurement. In the computational works, two-dimensional blade shapes at several arbitrary radial sections have been selected for flow computations around the blade model. For three-dimensional computation applied a non-inertia coordinate system, a flow field around the entire three-dimensional blade shape is used to evaluate flow patterns in order to take radial flow interactions into account. The computational results were compared with the experimental results.     

带摩擦阻尼器长叶片振动特性优化研究

为了防止透平机械长叶片因振动而导致的疲劳损坏,目前普遍采用的方法是在叶片上增加摩擦阻尼结构.针对带摩擦阻尼器长叶片的结构特点,采用扭曲梁与空间直梁单元模化叶片,推导叶片阻尼连接单元的力学模型,由此建立叶片总的动力特性分析方程.然后详细分析某阻尼围带长叶片具有不同围带厚度和围带间隙的振动响应,由此获得优化的阻尼围带结构,该分析结果还与自由叶片的响应数值进行对比,发现共振时由于围带的阻尼效果,优化阻尼结构的最大响应值只有自由叶片的42.4%.最后分析添加整圈松拉金结构的叶片振动响应,发现松拉金的加入将进一步降低叶片振动响应值.分析结果表明,该数值模型可以应用于多种摩擦阻尼器长叶片的振动特性分析及优化设计,将为阻尼叶片的设计提供实用工具.     

带缘板摩擦阻尼器叶片的非线性振动响应研究

发展了一种用于计算带摩擦阻尼器叶片非线性响应的时频转换方法。该方法能够方便地计算接触面非线性摩擦力，考虑响应的高次谐波以及叶片高阶振型的影响。对带缘板阻尼器的双平板叶片进行了振动试验并对试验模型进行了理论计算，讨论了各模型参数对缘板阻尼器减振效果的影响。通过试验结果与理论结果的比较，验证了理论方法的正确性。该方法稍加推广即可研究循环叶片组的振动特性，为指导带缘板阻尼器叶片的减振设计奠定了基础。     

叶片反弯曲对涡轮静叶栅流场影响的试验研究

对一典型涡轮静叶型开展了叶片反弯曲对涡轮静叶栅流场性能影响的试验研究。测量了直叶片叶栅和-10°、-20°弯曲叶片叶栅出口流场。结果表明,对该叶型叶栅,随着叶片反弯曲角的增加,叶栅出口通道涡的强度和尺度稍有增大,但位置变化不太明显,尾缘涡有所减弱,叶栅中部和端部横向二次流均增强;随着叶片反弯曲角的增加,叶栅中部损失变化不大,而端部附近损失明显增大,使叶栅总损失增大,直叶栅总损失最小。     

超低比转数离心鼓风机4种叶片形状性能试验对比

针对某一工业用超低比转数离心鼓风机,选取直叶片、后弯叶片、前弯叶片和径向变厚度前弯叶片(VTB)4种叶片作为试验叶片,通过性能试验得到了4种不同形状的叶片对该风机性能的影响。再进一步采用可视化流动试验来观察其叶轮内部空气的流动状况,分析产生性能差异的原因。通过对使用这4种形状叶片的风机的性能试验以及可视化流动研究,为超低比转数离心鼓风机的叶片优化设计提供有益的参考。     

缘板干摩擦阻尼器叶片减振实验研究

为了减小叶片振动,在叶片缘板部位设置干摩擦阻尼器,以引入外加阻尼。本文介绍缘板干摩擦阻尼器叶片减振实验研究方法;针对带阻尼器的单叶片、双叶片,在3种激振力、9种正压力情况下,进行1阶弯曲、1阶扭转、2阶弯曲强迫振动实验;对试验结果进行分析,获得阻尼器对不同振型下振动响应和谐振频率的基本影响规律。实验结果表明:干摩擦阻尼器对1阶弯曲、1阶扭转振动有一定的减振效果;对2阶弯曲振动没有减振作用。     

低展弦比涡轮静叶栅叶片正弯曲作用的试验研究

对弯曲叶片研究中代表性的HIT涡轮静叶型重新开展了叶片弯曲对低展弦比涡轮静叶栅流场影响的试验研 究。测量了直叶片叶栅、+10°、+20°和+30°弯曲叶片叶栅的进、出口流场,分析了叶片弯曲对叶栅出口二次流、 总压损失和气流角的影响。结果表明:对该叶型叶栅,叶片正弯曲既不能大幅度降低叶栅二次流损失,也不能改 善叶栅出口气流角沿叶高的分布:叶栅出口二次流动、尾缘涡及壁角涡随叶片正弯曲角的增大而增强,而通道涡 强度和位置变化不大;该研究结果同以往有关文献的研究结果完全不同。     

非均匀气流场中的汽轮机短叶片间隙气流激振力分析

从流体动力学出发 ,应用动量定理研究了定叶片出气边具有一定厚度的非均匀气流场中汽轮机的间隙气流激振力 ,将气流速度展开成 Fourier级数 ,并综合考虑了叶片的各项设计参数 ,并应用理论分析的方法导出了在非均匀气流场中汽轮机直叶片级、扭叶片级短叶片的间隙气流激振力计算公式     

一类金属橡胶阻尼器的建模与参数识别

研究了一类金属橡胶阻尼器的非线性特性,根据实验数据建立了具有迟滞非线性特性的阻尼器力学模型,通过实验获得了金属橡胶阻尼器特性数据,并提出了两种识别阻尼器迟滞恢复力参数的方法:二维拉格朗日插值法和人工神经网络方法。研究结果表明:拉格朗日插值法可以保证实验值与理论值在插值结点完全重合,具有较高的精度;人工神经网络具有较快的训练速度和很强的学习功能。通过将实验数据与理论计算数据进行对比表明,本文提出的两种方法都可以取得较好的识别效果,曲线拟合的均方差较小,在提高识别效率的同时保证了计算精度。     

螺旋锥齿轮数控加工中刀盘误差的补偿

在进行螺旋锥齿轮数控加工过程中,用直廓截形代替盘状铣刀刀刃理论截形所产生的偏差会影响螺旋锥齿轮齿面加工精度。针对该问题,分析了螺旋锥齿轮数控加工原理,并在此基础上建立了从刀刃到形成齿面的数学模型;依据空间啮合理论计算盘状铣刀刀刃实际截形,分析并建立了盘状铣刀刀盘半径偏差与齿面误差的关系;进一步推导出刀具实际截形误差的计算过程;最后根据螺旋锥齿轮的加工原理对刀具的误差进行了补偿计算,并对补偿结果进行了仿真实验验证,证明了该算法的可靠性。     

关于砼搅拌车螺旋叶片设计研究

根据搅拌筒前锥、圆柱、尾锥三部分螺旋叶片的功能,规划出三部分螺旋叶片的叶片型式。确定三部分叶片之根部和顶部的螺旋线线型,重点给出搅拌筒圆锥螺旋叶片根部和顶部螺旋线数学方程,并利用三维软件Pro/E的关系参数表达式来实现叶顶、叶根螺旋线。通过边界混合命令建出圆锥对数直纹斜螺旋面,为螺旋叶片的设计建模提供了理论基础。     

离心压缩机二元和三元叶轮内流分析

选择两个不同相对轴向尺寸和相对宽度的叶轮,在各自子午型线保持不变的情况下,分别对每一个叶轮构造普通圆弧叶片和三元扭曲叶片。利用Ｓ１,Ｓ２流面理论简化计算模型对所构成的具有不同叶片形式的叶轮进行了内部流场计算。着重对比了叶片表面的速度分布,对其起因进行了分析讨论。     

扭曲叶片贯流风机流场及扭曲角对性能的影响研究

研究了电壁炉用贯流风机在扭曲叶片下的三维内部流场,数值比较了不同扭曲角对贯流风机出风口体积流率的影响,从而得到贯流风机叶轮在一定转速下,叶片扭曲角取60°时,风机出风口风量最大,性能最优.通过自建的贯流风机性能参数检测台,实验测试了扭曲叶片贯流风机出风口平均风速和直叶片贯流风机出风口平均风速大小,并且和数值计算结果基本吻合.为贯流风机叶片优化设计提供了重要的理论基础.     

Lifting-surface theory of straight cascades of swept blades

Lifting-line and lifting-surface expressions are derived for the steady irrotational incompressible flow through a straight cascade of swept blades of finite length and constant loading along the span, the main object being to study the three-dimensional perturbations arising from the presence of the end walls and to determine the warped shape of the blade camber surface. The blade axis is taken perpendicular to the blade-to-blade direction, as an approximation to conical flow with radially set blades. The solution, in terms of the velocity potential, is based on the author's analytical expressions for cascades of unswept blades of varying circulation along the span. Numerical results are presented for a wide range of cascade geometries, and the effects of several cascade parameters upon the wall-induced three-dimensional perturbations are discussed. In particular, it has been found, for most geometries used in practice, that a good approximation is obtained by superposing the disturbances due to the two walls separately.     

三叶片直线翼垂直轴风力机非定常流场速度分析

垂直轴风力机在回转过程中,叶片尾流的相互干涉和叶片攻角变化,使垂直轴风力机周围流场异常复杂。为探明直线翼垂直轴风力机在二维流场中速度分布及风力机叶片迎风角度变化关系,在风洞试验中采用激光多普勒测速仪(Laser Doppler velocimetry,LDV)技术,对所设计的三叶片直线翼垂直轴风力机流场风速进行试验研究,获得了该风力机叶片周围流场的速度分布情况。在建立直线翼垂直轴风力机在不同转速下叶片迎风角度变化的数学模型基础上,应用仿真软件对被测风力机流场进行分析计算。通过数学模型得知,来流风速夹角随回转角的变化情况可用正弦函数近似表示, 并且随着叶尖速比的增大逐渐减小。风洞试验和CFD结果表明,风力机在回转过程中,叶片前缘场域有乱流生成,并且该域风速值偏大;而在叶片旋转内部以及下流区域内会形成一个宽大的低速区域,并且伴随叶尖速比的增加,低速区域具有扩大趋势。     

Turbulent flow field structure of initially asymmetric jets

The near field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemometry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. Three pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the pipe exit, secondary flow through the bend and mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameter-long straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases.     

一种干摩擦缘板阻尼系统分析的新方法

干摩擦缘板阻尼器已广泛应用于涡轮叶片减振设计中。为了进一步提供有效的缘板阻尼器设计资料,采用改进后的整体滑动模型,提出一种新的缘板干摩擦分析方法,比以往的谐波平衡法更为准确科学。由此分析不同正压力下干摩擦缘板阻尼系统的动力响应,得到阻尼器达到最佳减幅效果时的正压力值。最后分析阻尼器附加正压力对叶片阻尼系统共振频率的影响。     

Postprocessor development for ultrasonic cutting of honeycomb core curved surface with a straight blade

When ultrasonically cutting honeycomb core curved parts, the tool face of the straight blade must be along the curved surface’s tangent direction at all times to ensure high-quality machining of the curved surface. However, given that the straight blade is a nonstandard tool, the existing computer-aided manufacturing technology cannot directly realize the above action requirement. To solve this problem, this paper proposed an algorithm for extracting a straight blade real-time tool face vector from a 5-axis milling automatically programmed tool location file, which can realize the tool location point and tool axis vector conversion from the flat end mill to the straight blade. At the same time, for the multi-solution problem of the rotation axis, the dependent axis rotation minimization algorithm was introduced, and the spindle rotation algorithm was proposed for the tool edge orientation problem when the straight blade is used to machine the curved part. Finally, on the basis of the MATLAB platform, the dependent axis rotation minimization algorithm and spindle rotation algorithm were integrated and compiled, and the straight blade ultrasonic cutting honeycomb core postprocessor was then developed. The model of the machine tool and the definition of the straight blade were conducted in the VERICUT simulation software, and the simulation machining of the equivalent entity of the honeycomb core can then be realized. The correctness of the numerical control program generated by the postprocessor was verified by machining and accuracy testing of the two designed features. Observation and analysis of the simulation and experiment indicate that the tool pose is the same under each working condition, and the workpieces obtained by machining also meet the corresponding accuracy requirements. Therefore, the postprocessor developed in this paper can be well adapted to the honeycomb core ultrasonic cutting machine tool and realize high-quality and high-efficient machining of honeycomb core composites.     

Fast-response total pressure probe for turbomachinery application

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe for the measurement of the total pressure field at the exit of blades. The result of measurement in a one-stage axial turbine is also presented. The fast-response total pressure probe is fabricated by installing a fast-response pressure sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use more than four sensors. The probe is applied to the one-stage axial turbine in order to measure the instantaneous total pressure downstream of rotor blades. The measured instantaneous signal is decomposed to obtain the blade-to-blade pressure distribution. The pressure distribution due to blade passing is clearly captured. Due to the loss generation in the casing region, the total pressure and its amplitude of fluctuation by the blade passing are lower in the shroud and hub region than in mid-span. The total pressure distribution at the exit of the rotor blade is found to be slightly different from blade to blade due to the geometric difference and the different relative positions of the rotor blades and stator vanes. The developed probe successfully measures the accurate total pressure distribution at the rotor exit, and allows the evaluation of the loss distribution and the accurate performance of turbomachinery.