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“流量测量技术与仪表选用”讲座:第十八讲 涡街流量计(一) 总被引:6,自引:0,他引:6
一、概述涡街流量计是在流体中安放一根非流线型旋涡发生体,流体在发生体两侧交替地分离释放出两串规则的交错排列的旋涡,在一定的流量范围内旋涡分离频率正比于管道内的平均流速(流量),通过采用各种形式的检测元件测出旋涡频率以测出流体的流量.涡街流量计依据流体力学振动现象中振动频率与 相似文献
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涡街流量计是利用卡玛涡街原理制成的一种新型流量计。在流体中安装涡街发生体,则可产生涡列。设在发生体处流体流速为V,涡街发生体的直径为d;流体在管内流速为V,管径为D,并设断面收缩比a=V/v,则涡列所产生的周波数f和它们的关系为 f=st v/d=st V/ad (1) st叫做斯多哈尔值。它和涡街发生体的β值(β=d/D)以及纵横比h/d有关。设Q为流体流量,则 相似文献
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带狭缝圆柱钝体流量测量特性研究 总被引:1,自引:0,他引:1
涡街流量计的流量特性与旋涡发生体的形状和几何尺寸密切相关,本文提出了一种新型的带狭缝圆柱发生体结构并应用于涡街流量计。理论分析表明狭缝可以看作是一个反馈通道,可有效加快旋涡脱落并增强旋涡强度。在内径为50mm的管道中进行实验,采集不同流量下带狭缝圆柱与梯形柱绕流产生的涡街信号,重点讨论带狭缝圆柱的小流量测量性能。实验表明,与梯形柱相比,带狭缝圆柱涡街信号更强,信噪比高,雷诺数测量范围可低至9.5?103,斯特劳哈尔数线性度更好。理论分析与实验结果表明,带狭缝圆柱具有较好的流量测量特性,可应用于涡街流量计。 相似文献
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介绍了一种新型的低雷诺数涡街流量计。其主要的特点是采用了独有的流体整流技术和压力检测技术,可以测雷诺数低至500的流体,这种流量计由整流部件、旋涡发生体、压力检测器和壳体等组成。 相似文献
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涡街流量计作为一种新型流量计发展迅速,但其依据的理论基础是基于开放的均匀流场,与流量计的实际使用条件不一样.因对于涡街流量计还需要开展一些基础研究,为设计和开发涡街流量计提供理论依据和设计准则,要以电容式涡街流量计,对其进行了建模与仿真分析,并在仿真分析的基础上提出了如何改善涡街流量计的设计以拓宽其在低速气体流量测量上的应用. 相似文献
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This paper is focused on numerical investigation of subsonic flow separation over a NACA0012 airfoil with a 6° angle of attack and flow separation control with vortex generators. The numerical simulations of three cases including an uncontrolled baseline case, a controlled case with passive vortex generator, and a controlled case with active vortex generator were carried out. The numerical simulation solves the three-dimensional Navier-Stokes equations for compressible flow using a fully implicit LU-SGS method. A fourth-order finite difference scheme is used to compute the spatial derivatives. The immersed-boundary method is used to model both the passive and active vortex generators. The characteristic frequency that dominates the flow is the natural frequency of separation in the baseline case. The introduction of the passive vortex generator does not alter the frequency of separation. In the case with active control, the frequency of the sinusoidal forcing was chosen close to the natural frequency of separation. The time- and spanwise-averaged results were used to examine the mean flow field for all three cases. The passive vortex generators can partially eliminate the separation by reattaching the separated shear layer to the airfoil over a significant extent. The size of the averaged separation zone has been reduced by more than 80%. The flow control with active vortex generator is more effective and the separation zone is not visible in the averaged results. The three-dimensional structures of the flow field have also been studied. 相似文献
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A numerical model of delta-wing type vortex generator was developed in two steps.The first step was to obtain a parameterized model of the shedding vortex based on delta-wing theory,which relates the geometry parameters and flow field parameters to the strength of shedding vortex which directly decides the source term.In the second step,a method was proposed to add source terms into the flow control equations so that the shedding vortex could be simulated numerically.As soon as the numerical model was compl... 相似文献
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In this study, temporal large-eddy simulations of the interaction between a turbulent jet flow and a trailing vortex are described. Three cases are analyzed: in the first one, the jet and the vortex axes are sufficiently well separated to not interact immediately, while in the second case, the distance between the jet and the vortex is reduced by half. In the last case the jet blows in the vortex core. In the two first cases, as the jet spreads it is progressively deflected by the continuous input of crossflow momentum. Thus it acquires azimuthal and radial components of velocity, causing the emergence of three-dimensional structures of azimuthal vorticity around it. When the jet and the vortex are superimposed, the turbulent kinetic energy does not increase, the vortex core is very buffeted. Numerical simulation results of the convection-diffusion of a passive scalar show that its distribution (initially in the jet) cannot penetrate inside the vortex core due to its solid rotation. For the cases where the jet is initially outside the vortex and when it is injected in the vortex wake, its value remains very high and cannot get out of the vortex core. This phenomenon confirms the existence of a stabilizing “dispersion buffer”, adjacent to the core, which prevents amplification of the turbulence generated inside the core. 相似文献
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流量是工业控制与生产中的一个重要参数.目前,涡街流量计应用相当广泛.但是,由于其工作原理的关系,它对外界的各种干扰非常敏感,使其现场测量精度大大低于实验室标定的精度.本文的主要目的是以数字信号处理的理论为基础,采用自回归模型谱估计的方法对涡街流量计的输出信号进行分析和处理,得出要测量的流量值.论文中分别采用计数的方法和自回归模型谱估计的方法进行实验.通过实验验证,自回归模型谱估计可以作为一种较好的方法,应用于处理流量计的输出信号,并且此方法得出的结果比脉冲计数方法得出的结果精度高. 相似文献
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R. Andrew RussellAuthor Vitae 《Robotics and Autonomous Systems》2011,59(2):65-73
This project investigates the biomimetic implementation of a form of communication observed in cave dwelling crickets. The cricket Phaeophilacris spectrum uses air vortices as a form of short-range communication. This project aims to mimic this communication technique for use in robotic systems and to assess its capabilities in terms of technical requirements, range and the data it can provide. The design of an air vortex generator and receiver are described. Results of practical experiments to code information into sequences of vortices as well as to determine range of the source and direction of arrival are also presented. 相似文献
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Various vortex generators which include ramp, split-ramp and a new hybrid concept “ramped-vane” are investigated under normal shock conditions with a diffuser at Mach number of 1.3. The dimensions of the computational domain were designed using Reynolds Average Navier–Stokes studies to be representative of the flow in an external-compression supersonic inlet. Using this flow geometry, various vortex generator concepts were studied with Implicit Large Eddy Simulation. In general, the ramped-vane provided increased vorticity compared to the other devices and reduced the separation length downstream of the device centerline. In addition, the size, edge gap and streamwise position respect to the shock were studied for the ramped-vane and it was found that a height of about half the boundary thickness and a large trailing edge gap yielded a fully attached flow downstream of the device. This ramped-vane also provided the largest reduction in the turbulent kinetic energy and pressure fluctuations. Additional benefits include negligible drag while the reductions in boundary layer displacement thickness and shape factor were seen compared to other devices. 相似文献
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在弱信号检测技术中,自相关滤波是滤除噪声干扰的有效方法,但由于计算量太大,一般的单片机很难实时地完成运算。针对涡街传感器在低流速时信号特征,设计了自相关数字滤波器,采用抽样计算的方法使计算时间缩短到典型算法的1/10~1/20,将流速下限降到1.8 m/s,并在气体涡街流量计中得到很好的应用。 相似文献
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Jacques Cohen 《Software》1975,5(2):169-180
The author describes some of his experience gained by working in the area of syntax-directed compilers and parser generating systems during the past ten years. His most recent work in this area was designing and supervising the implementation of a conversational parser generator which has been operational for about two years. The paper describes this generator, its implementation, usage and the characteristics which make it practical to use. The author's main conclusion is that althouth it is relatively easy to implement nuclei of parser generating systems which are of educational value, the implementation of a practical system requires a major programming effort. 相似文献