INVESTIGATION OF VORTEX SHEDDING INDUCED HYDRODYNAMIC VIBRATION IN VORTEX STREET FLOWMETER

Vortex street flowmeter has been used in steady flow measurement for about three decades The benefits of this type of flowmeter include high accuracy,good linearty,wide measuring range,and excellent reliability However,in unsteady flow measurement,the pressure disturbance as well as the noise from the system or surrounding can reduce the signal to noise ratio of the flowmeter seriously Aimed to use vortex street flowmeters in unsteady flow measurement,the characteristics of the vortex shedding induced hydrodynamic vibration around the prism bluff body in a vortex street flowmeter are investigated numerically and by expriments The results show that the hydrodynamic vibrations with 180° phase shift occur at the axisymmetric points of the channel around the bluff body The most intense vibration occurs at the points on the lateral faces close to the base of the prism The results provide therefore a useful reference for developing an anti interference vortex flowmeter using the different ial sensing technique.

Numerical Solution of the Weight Function for Electromagnetic Flowmeter

A numerical solution of the weight function for a two-electrode electromagnetic flowmeter was proposed. The solution was obtained by using the finite element method based on the basic equation of a traditional two-electrode electromagnetic flowmeter. The two-dimensional distribution of the weight function of the electromagnetic flowmeter obtained was verified by the analytical solution. Three-dimensional distribution of the weight function was also presented in the paper. It can be employed to analyze the sensitivity and linearity of the electromagnetic flowmeter with non-uniform magnetic field, and even to assist the design of the excitation coil pair.

Research and Development on β Ray Ionization Gas Flowmeter

A new method of measuring gas flow in heavy or medium pipe based on the ionization effect of gas irradi ated with rays is presented. The mesurement principle of the flowmeter has been theoretically analyzed,the structure form and the base of relevant parameter’s choice of the flowmeter have been given, and theintellectual instrument is developed. The results of experiment show that the per formance of the flowmeter is stable, the precision can reach 1 to 1. 5 percent, and it has fairly capability to resist disturbance and pollution.

Development of DSP-Based Dynamic Signal Processing Module for Turbine Flowmeter

Traditional signal processing methods for turbine flowmeter are unable to solve the contradiction between the real-time performance and the accuracy during the aeroengine bench test or hardware in the loop(HIL)simulation of aeroengine control system.A dynamic flow measurement method based on cycle number of the flowmeter is proposed.And a DSP-based multi-functional dynamic signal processing module for turbine flowmeter is built to validate the method.The developed system can provide three types of output modes including PWM,frequency and D/A.At the same time,the results can be displayed instantly with the module of serial communication interface to obtain dynamic flow signal with good precision.Experimental results show that the stability of flow measurement is greatly improved with precision guaranteed and the real-time response reaches the maximum limit of turbine flowmeter.

Research on double differential pressure dynamic flowmeter

When testing an electrohydraulic proportional valve,it is necessary to test the high frequency dynamic flow with bias.Because of the limitation of the piston stroke,a no-load hydraulic cylinder is only suitable for a reciprocating symmetrical dynamic flow test.Since the traditional differential pressure flowmeter is affected by viscosity and inertia of the fluid,it is only suitable for measuring steady flow.Therefore,a new type of double pressure differential dynamic flowmeter is designed to improve the traditional differential pressure flowmeter.The influence of fluid viscosity and inertia in the flow process are negated by subtracting the differential pressure in section expansion from the differential pressure in section contraction.The double differential pressure flowmeter is modeled and a flow meter prototype is designed.Then,the flow coefficients are identified and corrected by a practical test.Finally,the dynamic performance and steady-state precision of the flowmeter are verified by comparing with the test results of the no-load hydraulic cylinder.The double differential pressure dynamic flowmeter is proven to measure dynamic flow accurately,especially at higher dynamic frequencies.

DESIGN,FABRICATION,TESTING AND MECHANICAL ANALYSIS OF BULK-MICROMACHINED FLOWMETERS

Micromachined piezoresistive flowmeters with four different types of sensing struc- tures have been designed,fabricated and tested.Piezoresistors were defined at the end of the sensors through p-diffusion,and their values were about 3.5kΩ.Wheatstone bridge was configured with the piezoresistors in order to measure the output response.The output voltage increases with increasing flow rate of air,obeying determined relationships.The testing results show that the sensors that are designed for measuring 10L/M in full operational range have desired sensitivities.The sensor chip is manufactured with bulk-micromachining technologies,requiring a set of seven masks.

Accuracy of Medical Oxygen Flowmeters: A Multicentric Field Study

The accuracy of 476 oxygen flowmeters was investigated using a thermal mass flowmeter in eight hospitals in France and Belgium. Different oxygen flow rates (2 to 15 l/min) were evaluated at the patient’s bed. When the sample was considered as a whole, the accuracy of delivered flow was acceptable but precision was poor. The variability of the delivered flow between devices was greater when a low flow rate was required. Compensated-pressure oxygen flowmeters for these low rates were more accurate than their non-compensated counterparts. This study emphasizes the need to individually adapt the oxygen flow rate each time a patient has to move from one flowmeter to another.

Design of the target type flowmeter based on fiber Bragg grating and experiment

The target type flowmeter based on fiber Bragg gratings （FBGs） is experimentally studied. The relationship between the central wavelength shift of FBG and the flux is derived and the analytic expression is also given. Simulation and preliminary experiments have been carried out, and experimental validation of the water further proves the feasibility of the sensor. The experimental results verify the proposed sensor which can measure flux range from 200 to 1200 cm^3/s. And on this basis, the improvement program is raised.

Flow-induced vibration characteristics of the U-type Coriolis mass flowmeter with liquid hydrogen

Compared with liquid nitrogen(LN_(2))and water,the density of liquid hydrogen(LH_(2))is more than one order of magnitude smaller,which leads to significantly different flow-induced vibration characteristics in the coriolis mass flowmeter(CMF).Based on the Euler beam theory,the complex set of equations of fluid-solid interactions for the U-type pipe Coriolis flowmeter with LH_(2)is solved.The calculation results are firstly validated by comparing the dimensionless frequency,displacement,and twist mode shape with the theoretical and experimental results in the other publications with water and kerosene as the working fluids.Then,the results of dimensionless frequency,phase difference,and time lag for LH_(2)are compared with those for LN_(2)and water,and the effects of the dimensionless flow velocity,sensor position,and the radius of the curved pipe are analyzed in detail for LH_(2).Results show that the time lag of LH_(2)is an order of magnitude smaller than that for LN_(2)or water.The excitation frequency for LH_(2)is much larger than that for LN_(2).Effects of geometric parameters on the time lag are also analyzed for the three fluids and the results contribute to the design optimization of a CMF for LH_(2).

Improvement of signal processing in Coriolis mass flowmeters for gas-liquid two-phase flow

As an increasingly popular flow metering technology,Coriolis mass flowmeter exhibits high measurement accuracy under single-phase flow condition and is widely used in the industry.However,under complex flow conditions,such as two-phase flow,the measurement accuracy is greatly decreased due to various factors including improper signal processing methods.In this study,three digital signal processing methods—the quadrature demodulation(QD)method,Hilbert method,and sliding discrete time Fourier transform method—are analyzed for their applications in processing sensor signals and providing measurement results under gas-liquid two-phase flow condition.Based on the analysis,specific improvements are applied to each method to deal with the signals under two-phase flow condition.For simulation,sensor signals under single-and two-phase flow conditions are established using a random walk model.The phase difference tracking performances of these three methods are evaluated in the simulation.Based on the digital signal processor,a converter program is implemented on its evaluation board.The converter program is tested under single-and two-phase flow conditions.The improved signal processing methods are evaluated in terms of the measurement accuracy and complexity.The QD algorithm has the best performance under the single-phase flow condition.Under the two-phase flow condition,the QD algorithm performs a little better in terms of the indication error and repeatability than the improved Hilbert algorithm at 160,250,and 420 kg/h flow points,whereas the Hilbert algorithm outperforms the QD algorithm at the 600 kg/h flow point.

矿井主排水系统的集中控制改造设计

为了响应单位精简机构,大幅度减员提效,实现矿井综合自动化办公,减少人员职责不清、缺乏效率的状况,现将我单位井下主排水泵房进行自动化改造。实现井下中央泵房的自动控制后,可以达到无人值守,提高矿井的自动化水平。

On Switching of a Flip-Flop Jet Nozzle with Double Ports by Single-Port Control

This research deals with the oscillation mechanism of a flip-flop jet nozzle with a connecting tube, based on the measurements of pressures and velocities in the connecting tube and inside the nozzle. The measurements are carried out varying: 1) the inside diameter d of the connecting tube;2) the length L of the connecting tube and 3) the jet velocity VPN from a primary-nozzle exit. We assume that the jet switches when a time integral reaches a certain value. At first, as the time integral, we introduce the accumulated flow work of pressure, namely, the time integral of mass flux through a connecting tube into the jet-reattaching wall from the opposite jet-un-reattaching wall. Under the assumption, the trace of pressure difference between both the ends of the connecting tube is simply modeled on the basis of measurements, and the flow velocity in the connecting tube is computed as incompressible flow. Second, in order to discuss the physics of the accumulated flow work further, we conduct another experiment in single-port control where the inflow from the control port on the jet-reattaching wall is forcibly controlled and the other control port on the opposite jet-un-reattaching wall is sealed, instead of the experiment in regular jet’s oscillation using the ordinary nozzle with two control ports in connection. As a result, it is found that the accumulated flow work is adequate to determine the dominant jet- oscillation frequency. In the experiment in single-port control, the accumulated flow work of the inflow until the jet’s switching well agrees with that in regular jet’s oscillation using the ordinary nozzle.

Application of MCU in refrigerant charging system

The technique of Microprocessor Control applicable to the refrigerant charging system is introduced while the technique of interface between LCD module MCG12864A4-2 and MCU is described, and the work flow and the idea of software are presented as well.

The Effects of DPPH on Cochlear Microcirculation

To investigate the effects of the free radical, 1, l-Diphenyl-2-picylhydrazyl, on cochlear blood flow, 20 guinea pigs were divided into 3 groups at random, 6 for control group, 6 for 1 mmol/ L group and 8 for 0. 1 mmol/L group. 2 μl vehicle or drugs were dropped into round window membrane (RWM). Cochlear microcirculation was monitored by laser Doppler flowmeter (LDF), and mean arterial blood flow (MABP), which was transferred by pressure conductor sensor and preamplifier, was simultaneously recorded on the computer. Our results showed that MABP was stable throughout the experiment. Cochlear blood flow (CBF) increased by 10. 32 % (P<0. 05) in 1 mmol/L group, and decreased by 4. 89 % in 0. 1 mmol/L group (P<0. 05). In control group cochlear microcirculation showed no significant changes. It is concluded that DPPH exerted effects on cochlear microcirculation.

EXPERIMENTAL STUDY OF VELOCITY DISTRIBUTIONS IN THE TRANSITION REGION OF PIPES

The accuracy of an ultrasonic flowmeter meaurement depends on the profile-linear average velocity. But this velocity in the transition region is not available at the present. In this article, the velocity in the transition region in pipes is studied by experimental methods. The Particle Image Velocimetry （ PIV ） is used to measure the flow field in the transition region in pipes, and the measured results from PIV are in good agreement with the Westerwell＇s experimental data. Based on the experimental data of PIV, the curves of the profile-linear average velocity in the transition region against the Reynolds number in the range from 2 000 to 20 000 are obtained, and it is shown that the coefficient k is constant when the Reynolds number is in the range of 2 000-2 400 and 6 000-20 000, and the coefficient k is increasing when the Reynolds number is in the range of 2 400-6 000. The results of this article can be used to improve the measurement accuracy of the ultrasonic flowmeters and as a theoretical basis for the research on the transition flow.

Estimation of vehicle queuing lengths at metering roundabouts

Signalized metering roundabouts are equipped with advanced loop detectors and traffic signals that can reduce vehicle queuing lengths, especially on the dominant approach, when unbalanced traffic flow conditions occur. At a metering roundabout, changeable queuing lengths and the location of detectors determine signal phase times, which in turn affect queuing length on each approach. To date, most studies have focused on perfor- mance comparisons between normal and metered roundabouts, but have failed to evaluate the effect of detector locations on queuing formations. In addition, no guidelines have been developed to enable practitioners to select the appropriate detector location that would lead to optimum roundabout performance. This study, therefore, formulated a numerical model for the estimation of queuing length at a metering roundabout. The model consists of advance vehicle detectors on two approaches and one traffic signal. In order to calibrate and verify the model, queuing lengths were recorded using two drones for the Old Belair Road metering roundabout in Adelaide, South Australia. In order to assess the fitness of the model, an R2 test was conducted, and the results showed that the numerical model can predict queuing lengths on the controlling and metered approaches with up to 83% of R2 value. Moreover, the estimated queuing lengths were compared against those predicted by the software AIMSUN for the same location and under the same conditions. It is expectedthat the model will assist and guide practitioners in determining the best detector locations for metering roundabouts.

8800DF（R）涡街流量计在铜冶炼中的应用

本文简述8800DF（R）涡街流量计在铜冶炼生产中的使用特点．介绍了8800DF（R）涡街流量计工作原理、优缺点、分类．使用注意事项、选型等。