涡街流量传感器动态压力场分布特性

利用数值计算的方法,实现对涡街流量传感器中压力场动态分布特性的研究。数值计算采用湍流理论中的k- 模型并结合CFD技术进行,以SIMPLE算法解离散控制方程。数值计算得到的旋涡脱落频率与试验结果相近,误差不超过7%,证明数值计算方法的有效性,并在此基础上通过对涡街流场中压力场分布特点的分析,给出检测旋涡信号的最佳区域。从分析旋涡在流场中动态变化过程入手,深入探讨引发压力场变化规律的流场内部机理。     

涡街流量计信号估计的自适应陷波方法

本文提出采用自适应陷波方法计算涡街流量计输信号的频率,并给出实验结果。流量计信号为一窄带信号,自适应陷波抑制一个特定的涡街频率,并且几乎不受位于带宽以外频率的影响。此自适应陷波器只需估计一个参数,频率计算非常简单,与以前的频率估计方法相比,它以前的频率估计方法相比,它有许多优点,是一种有效的新方法。     

STUDY ON MECHANISM OF HYDRODYNAMIC OSCILLATION IN VORTEX PRECESSION METER USING LARGE EDDY SIMULATION

0　ＩＮＴＲＯＤＵＣＴＩＯＮＶｏｒｔｅｘｐｒｅｃｅｓｓｉｏｎｍｅｔｅｒ (ＶＰＭ )ｈａｓｂｅｅｎｕｓｅｄｔｏｍｅａｓｕｒｅｔｈｅｖｏｌｕｍｅｆｌｏｗｒａｔｅｏｆｇａｓａｎｄｌｉｑｕｉｄｆｌｕｉｄｉｎ ｐｅｔｒｏｌｅｕｍａｎｄｃｈｅｍｉｃａｌｉｎｄｕｓｔｒｉｅｓ Ｉｔｇａｕｇｅｓｖｏｌｕｍｅｆｌｏｗｒａｔｅｓｂｙｍｅａｓｕｒｉｎｇｔｈｅｆｒｅｑｕｅｎｃｙｏｆｈｙｄｒｏｄｙｎａｍｉｃｏｓｃｉｌｌａｔｉｏｎｓ ｐｒｏｄｕｃｅｄｂｙｔｈｅｖｏｒｔｅｘｐｒｅｃｅｓｓｉｏｎｓｉｎｓｉｄｅｔｈｅｃｈａｎｎｅｌｏｆＶ…     

涡街流量传感器压力损失系数的试验研究与计算

在天津大学电气与自动化工程学院流量实验室的气体流量试验装置上,通过改变管道内气体的压力,对涡街流量传感器的压力损失系数进行试验研究。对大量试验数据进行处理后发现,涡街流量传感器的压力损失系数会随着管道内气体压力的变化而有所变化。当管道内气体压力在0.1～1.1 Mpa的范围内变化时,压力损失系数会随着气体压力的增大而减小,变化幅度最大达到了7%。对压力损失系数随气体压力变化的规律进行分析,并给出压力损失系数随管道内气体压力变化的计算公式。     

INVESTIGATION OF VORTEX SHEDDING INDUCED HYDRODYNAMIC VIBRATION IN VORTEX STREET FLOWMETER

0 INTRODUCTIONWhen a bluff body is placed in a flow stream,vortices form behind it and shed alternately from eachside. The shedding frequency keeps in a direct ratiowith the mean velocity over a wide range of Reynoldsnumbers.The idea of building a flow meter based on theassumption of a constant Strouhal number was firstproPOsed by Roshko, whose work indicated that theStrouhal number remains at an almost constant valueof 0.2 in the Reynolds number ranged 300 < Re <2 x l0s .For about thr…     

A computational study of annular cascade flows using aq-ω turbulence model with a wall function

A computational code has been developed for steady viscous flows in three dimensional annular cascades. This code solves a special form of the thin-layer Navier-Stokes equations with a two-equationq-ω turbulence model in curvilinear coordinates using a time asymptotic method for steady state solutions. It employs a scalar implicit approximate factorization in time and a finite volume formulation with second-order upwind-differencing in space. A wall function treatment is implemented at solid boundaries for turbulence equations instead of integration to the wall to relieve gridding requirements. In order to validate the effectiveness of this code, computational studies have been made to access modeling capability for complex turbulent flow fields in three dimensional annular cascade geometries which typically include laminar-turbulent boundary layer transition. The results have been compared with both the computational studies with integration to the wall and the experimental studies. The wall function treatment was found to be reliable by predicting secondary flows and loss contours reasonably well.     

用于测量石油天然气管道流量的复合式传感器

基于流体力学皮托管测量流体流速的原理,提出了一种用于测量流体流速的复合式传感器,由一个静压和一个差压传 感器构成。介绍了这种新型传感器的测量原理、结构设计和芯片制作,并列举了实验数据。此传感器能同时显示流体的静压和 差压,并且实现了智能化,能被用于无人流体观测站。     

多点位压力流量检测仪研究

对液压系统中多个关键点的压力、流量值进行自动检测,是液压系统状态监测和故障诊断的基础,本文针对某设备状态监测系统中的关键仪器kk多点压力流量检测仪研制中的硬件、软件设计和数据处理方法进行了讨论。简要介绍了检测仪的原理,重点说明了仪器硬件、软件结构和检测数据处理等关键问题。根据液压系统工作环境恶劣,各种随机干扰对检测信号影响大等特点,将数据平滑方法用于压力、流量信号检测数据处理中,有效地减小了各种随机噪声的影响,具有很好的效果。     

Influence of blockage and upstream disturbances on the performance of a vortex flowmeter with a trapezoidal bluff body

Experimental investigations are conducted on vortex flowmeter with the differential wall pressure measurement method. The bluff body employed is trapezoidal in shape and water is used as the working fluid. Three different blockages (0.14, 0.24 and 0.3) are considered in this study. The performance of the vortex flowmeter is studied both under fully developed condition and in the presence of flow disturbances. The flow disturbance is created using 45° swirl generator and gate valve placed at different upstream distances. The performance of the flowmeter is also evaluated in the presence of a Laws Vanes flow conditioner placed downstream of the swirl generator. The blockage ratio of 0.3 is found to be the best among all the blockages studied under both disturbed and undisturbed conditions.     

Theory of errors in Coriolis flowmeter readings due to compressibility of the fluid being metered

The compressibility of fluids in a Coriolis mass flowmeter can cause errors in the meter’s measurements of density and mass flow rate. These errors may be better described as errors due to the finite speed of sound in the fluid being metered, or due to the finite wavelength of sound at the operating frequency of the meter. In this paper, they are investigated theoretically and calculated to a first approximation (small degree of compressibility). The investigation is limited to straight beam-type (and does not consider shell-type) Coriolis meters. A lumped-parameter (coupled oscillator) model is used to explain the process causing the errors, and a simple 2-D continuum mechanics model is used to derive expressions for the magnitudes of the errors. Applications might be to Coriolis metering of gases, or to two-phase mixtures in the form of aerated liquids.     

Pressure effects on Coriolis mass flowmeters

The current status of available work regarding the pressure effect on Coriolis mass flowmeters is reviewed, which shows significant improvement in the latest generation of Coriolis flowmeters. A theoretical method using the linear damping model is proposed to understand the pressure effect. This new method applied to Coriolis flow sensors provides intuitive insight into the flow-generated signal by studying undamped natural frequencies and mode shapes. Most importantly this method can be used to model virtually any shape and configuration of flow sensors as found in the practical design. It is found that when the pressure changes it alters the superimposed contribution and the mass flow measurement can deviate from the reference condition. Experimental results from both low and high pressure flow tests are reported, which are in general agreement with the theoretical prediction. Further specific work is finally suggested which may advance our understanding and improve the Coriolis mass flow measurement technology.     

Wavelet denoising applied to vortex flowmeters

For the problems of signal extraction from noisy data, wavelet denoising has been proven to be a powerful tool from both an empirical and an asymptotic point of view. In this context of wavelet denoising, we study the specifically modified criteria as flexible forms of thresholding for practical vortex flowmeter signals. Four key factors are discussed. Analysis based on practical signals shows that this method can be used to extend the lower measurement limit of the vortex flowmeters.     

信号滤波和传感器特性对相关测速影响的研究

本文介绍在测量管内流动的高温烟气流速的实验中采用FIR低通数字滤波器方法可以排除干扰信号的影响的研究,实验结果证明,经过滤 处理后的信号互相关函数的图形不会出现大小相当的多个峰值,符合理论分析的结果;其次,本文还介绍了用热电偶和压力传感器采集的烟气温度和压力脉动信号,分析了传感器特性对相关测速的适应性。