梢涡空化CFD数值方法

针对梢涡空化问题,应用雷诺平均的N-S方程并结合改进VOF(volume fraction)模型,对椭圆形水翼梢涡空化特性进行了研究,采用的湍流模型为代数雷诺应力模型.为减小网格离散误差,计算中对梢涡处的网格进行了加密.对未发生空化时梢涡内轴向速度和切向速度分布进行计算,为了准确模拟梢涡涡核内系统旋转和流线曲率影响,将...     

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%.     

轴流式喷水推进泵水力设计和性能检验

基于Matlab-Simulink建立了一套轴流式喷水推进泵计算机辅助设计(CAD)程序(其中叶轮采用升力法设计,导叶采用流线法设计),实现了其水力设计参数的快速选择与计算,直接得到了叶片流面的空间坐标,可方便进行三维几何造型.采用计算流体力学(CFD)方法,通过建立计算域、划分高质量结构化网格、定义边界条件、数值计算...     

贫液泵泄漏问题技术改造研究

对中国神马集团尼龙66盐有限责任公司制氢装置贫液泵的使用效果、存在问题及其原因进行论述分析，运用新技术，对泵进行改造，实现可观的经济效益。     

纳米WC/12Co涂层在轴流式引风机叶片防磨上的研究

采用超音速火焰喷涂工艺分别制备了纳米结构和微米结构的WC/12Co涂层.通过和传统轴流式引风机叶片抗冲蚀涂层的比较,研究分析了两种涂层的显微硬度、金相结构、结合强度和抗冲蚀磨损性能.结果表明:超音速火焰喷涂WC/12Co涂层性能优于传统抗冲蚀涂层,其中纳米结构涂层性能更加优越.     

螺旋桨叶片曲面数控加工几何模型研究

目前在螺旋桨叶片曲面数控加工中,普遍存在着加工效率太低的现象,如何在保证加工精度的前提下提高加工效率已成为急待解决的问题。难过给出一般螺旋桨叶片工作面的方程,应用微分几何理论推导了数控加工所用球头铣刀的最大允许半径计算公式、走刀步长以及切削行距的计算公式,给出了根据刀具运动包络面计算实际加工误差的方法,最后通过实例验证了所建立模型的可行性和可靠性,为提高螺旋桨叶片曲面的加工效率提供了有效途径。     

吸入室角度对环形射流泵空化性能的影响

利用数值模拟的方法研究环形射流泵(AJP)内的空化发展规律,比较分析不同吸入室角度对环形射流泵空化性能的影响,得到如下结论.1)Realizable k-ε湍流模型结合mixture多相流模型及Schnerr-Sauer空化模型可以较好地模拟环形射流泵内的空化现象.2)随着环形射流泵出口压力的降低,喉管入口壁面处的空化区域会向喉管内延伸,引发的低压区会不断地向轴心线扩展.当低压区扩展到轴心线时,喉管内空化区剧烈发展,环形射流泵进入极限工况.3)当空化数大于极限空化数时,环形射流泵效率不受空化的影响;当空化数降低至极限空化数时,环形射流泵的效率陡降,空化数保持恒定不再降低,对应的值是极限空化数.4)吸入室角度越小,各个流量比对应的极限空化数越小,泵的空化性能越好.较小的吸入室角度使得环形射流泵更易诱发回流中心及剪切层空化云的产生.     

基于MATLAB的超声空化气泡动态仿真

推导出考虑了液体粘滞性、表面张力和辐射阻尼的单一空化气泡运动方程,在Matlab下仿真得到了单一空化气泡的动态曲线,为用数值方法进一步研究空化气泡的运动过程提供了参考。     

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.     

大型轴流泵站双向出水流道设计及模型试验验证

提出了一种适合于自流排灌和机电排灌相结合的低扬程大型立式轴流泵站的出水流道及其设计方法,结合上僚泵站双向进、出水流道模型装置,经过多方案的对比试验和对流态的观察分析,验证了该设计方法的可行性.同时,针对矩形有压涵洞式出水流道提出了改善其流态的具体措施.该设计方法对同类泵站的出水流道设计有参考价值.     

轴流式水轮机转轮叶片密封漏油修复方案

轴流式水轮机转轮叶片密封漏油是水电站常见故障,严重影响着水轮发电机组的安全运行。针对国内某水电站轴流机组出现的转轮叶片密封漏油故障,阐述了该故障的主要状况,根据已有资料和现场测试分析并验证了故障产生的原因,提出了具体的转轮体及叶片加工和安装的修复方案,修复方案在实际运行中已被采用并证实有效。     

叶片泵泄漏流量脉动的研究

对10片叶式轿车转向泵定子曲线进行了校系统的研究,分析其运动特性及流量脉动。在前人研究工作的基础上,建立了转向泵漏油流量的数学模型。结果表明,分段组合曲线不但运动学特性较好,而且其流量脉动显著降低,10片叶式泵而言,比通常采用的高次曲线更有推广应用价值。     

叶片泵泄漏流量脉动的研究

对 10叶片式轿车转向泵定子曲线进行了校系统的研究 ,分析其运动特性及流量脉动。在前人研究工作的基础上 ,建立了转向泵漏油流量的数学模型。结果表明 ,分段组合曲线不但运动学特性较好 ,而且其流量脉动显著降低 ,10叶片式泵而言 ,比通常采用的高次曲线更有推广应用价值     

浆液搅拌车的轴流泵喷浆流场仿真分析

对轴流泵在水煤浆储罐中的工作情况进行了研究,运用流体动力学知识建立了轴流泵工作时储罐中浆液的流体数学模型.进而使用大型有限元分析软件ANSYS对整个问题进行有限元求解,并对求得的仿真结果进行分析.为提高轴流泵的搅拌性能和选择合理的参数提供依据.最后针对轴流泵的流量及出口形状对整个流体场的影响做进一步讨论,讨论结果对轴流泵的结构设计有一定的指导意义.     

Study on leakage flow characteristics of radial inflow turbines at rotor tip clearance

Tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow caused by relative motion between casing and rotor tip, and the pressure difference between pressure side and suction side at rotor tip, play important roles in tip clearance leakage flow. The more the rotor tip speed increases and tip clearance height decreases, the more the scraping effect acts. Though the leakage velocity of tip clearance at midsection and exducer regions changes less when the rotor rotational speed is changing, the distance between passage vortex and rotor suction side varies in evidence. Main leakage flow rate of tip clearance takes place at region of exducer tip and some seal configurations will be quite effective for cutting leakage flow if these configurations are arranged over midsection and exducer of the radial inflow rotor.     

Effect of cavitation on comminution of mica powder

The cavitation abrasive water jet was used in the comminution of mica.By applying a cavitation nozzle in the abrasive water jet system to enhance the effect of cavitation and friction,better comminution results were obtained.The JME-200CX transmission electron microscope was used for observing the size distribution of particles.As using cavitation abrasive water jet,the relative comminution effect is raised by more than 25% compared with using abrasive water jet oly.It can be concluded that the effect of cavitation is much more significant than that of impacting in the comminution of mica.     

基于单叶顶传感器非接触在线测量叶片振动间断相位法的研究

提出了基于单叶顶传感器非接触在线测量汽轮机叶片振动状态的间断相位法。该方法通过测量叶顶到达安装于机壳上的传感器处的时间获得叶片的振动位移,根据多次测量得到的振动位移序列求得叶片的振幅,再通过对叶片振动位移序列的离散傅立叶变换求得叶片的振动频率。理论模拟及实验结果表明,该方法可以较准确获得叶片的振幅和频率,用于叶片振动非接触在线测量是可行的。     

螺旋桨尾流中螺旋梢涡声场的解析计算

通过将螺旋桨尾流中的螺旋梢涡近视地看成具有螺旋对称性的圆柱螺旋涡丝,本文推导出了毂涡和五根螺旋梢涡辐射声场的解析解,以及在给定参数下的数值仿真结果。计算表明速度场和压力场都是时间的基频和倍基频函数,压力脉动的特性得到体现。