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.

A New Device for Gas-Liquid Flow Measurements Relying on Forced Annular Flow

A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The swirling blades are used to transform the complex flow pattern into a forced annular flow.Drawing on the research of existing blockage flow meters and also exploiting the single-phase flow measurement theory,a formula is introduced to measure the phase-separated flow of gas and liquid.The formula requires the pressure ratio,Lockhart-Martinelli number(L-M number),and the gas phase Froude number.The unknown parameters appearing in the formula are fitted through numerical simulation using computational fluid dynamics(CFD),which involves a comprehensive analysis of the flow field inside the device from multiple perspectives,and takes into account the influence of pressure fluctuations.Finally,the measurement model is validated through an experimental error analysis.The results demonstrate that the measurement error can be maintained within±8%for various flow patterns,including stratified flow,bubble flow,and wave flow.

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.

Effects of spinal cord stimulation on cerebrovascular flow: role of sym-pathetic and parasympathetic innervations

Objective Cervical spinal cord stimulation （SCS） has been found to augment cerebral blood flow （CBF） in a number of animal models. However, the effective use of SCS is hampered by a lack of understanding of its mechanism（s） of action. In this paper, we focus on the sympathetic and parasympathetic effects of SCS on CBF. Method SpragueDawley rats were selected for the experimental series. The animals were divided into 5 groups to underwent SCS and laser Doppler flowmeter （LDF） recordings. Control group, the animal underwent SCS and LDF recordings without any surgery of the nerve fibers and ganglia. V 1 group, the animal underwent bilateral resection of the nasociliary and post-ganglionic parasympathetic nerve fibbers. SCG group, the animal underwent bilateral resection of supper cervical ganglion. V 1 ＋ SCG group, the animal underwent both surgeries as V1- and SCG-group animals did. Sham group, the animal underwent the carotid manipulation with blunt-tipped forceps as well as the dissection of nasociliary and post-ganglionic parasympathetic nerve fibers around the ethmoidal foramen, but without cutting any nerves. Results During the SCS, the LDF was no statistical difference between the V 1 or SCG group and the control group. Yet, the effects of SCS on CBF are completely abolished in V1＋ SCG group. Conclusions Surgical interruption of both the parasympathetic and sympathetic pathways has the contradict effect on SCS-induced CBF augmentation.

Application of empirical mode decomposition based energy ratio to vortex flowmeter state diagnosis

To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter.

Application of Hilbert-Huang transform to denoising in vortex flowmeter

Due to piping vibration, fluid pulsation and other environmental disturbances, variations of amplitude and frequency to the raw signals of vortex flowmeter are imposed. It is difficult to extract vortex frequencies which indicate volumetric flowrate from noisy data, especially at low flowrates. Hilbert-Huang transform was adopted to estimate vortex frequency. The noisy raw signal was decomposed into different intrinsic modes by empirical mode decomposition, the time-frequency characteristics of each mode were analyzed, and the vortex frequency was obtained by calculating partial mode’s instantaneous frequency. Experimental results show that the proposed method can estimate the vortex frequency with less than 2% relative error; and in the low flowrate range studied, the denoising ability of Hilbert-Huang transform is markedly better than Fourier based algorithms. These findings reveal that this method is accurate for vortex signal processing and at the same time has strong anti-disturbance ability.

Influence of bluff body shape on wall pressure distribution in vortex flowmeter

To investigate the influence of bluff body shape on wall pressure distribution in a vortex flowmeter,experiments were conducted on a specially designed test section in a closed water rig at Reynolds numbers of 6.2×10 4-9.3×10 4.The cross sections of the bluff bodies were semicircular,square,and triangular shaped,and there were totally 21 pressure tappings along the conduit to acquire the wall pressures.It is found that the variation trends of wall pressures are basically identical regardless of the bluff body shapes.The wall pressures begin to diverge from 0.3D(D is the inner diameter of the vortex flowmeter) in front of the bluff body due to the diversity in shape,and all reach the minimum values at 0.3D behind the bluff body.A discrepancy between the triangular or square cylinder and the semicircular cylinder in wall pressure change is observed at 0-0.1D behind the bluff body.It is also found that the wall pressures and irrecoverable pressure loss coefficients increase with flow rates,and the triangular cylinder causes the smallest irrecoverable pressure loss at a fixed flow rate.

Study on hydrodynamic vibration in fluidic flowmeter

The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.

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.

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.

Effect of Garment Pressure on Peripheral Skin Blood Flow(SBF)

To well understand the effect of garment pressure on skin blood flow(SBF) at lower limb,external pressures of various magnitudes were exerted on lower limb in supine or sitting postures respectively using sphygmomanometer.Five male subjects volunteered to participate in this study.An alternating pressure loading protocol between non-pressure and pressure was employed.The SBF was observed by laser flowmeter.No matter the subjects being sitting or supine,SBF obviously increased under low pressure;as the pressure increasing,it turned to decrease.Moreover,while lying supine,SBF turned to decrease under lower pressure than sitting;SBF at calf turned to decrease under lower pressure than at ankle.It was also confirmed that the increment of SBF was obviously higher when the pressure of the same magnitudes was exerted at ankle than at calf.The pressure around 5.32 kPa was confirmed to be a crucial value to SBF.The findings will be helpful in design and application of tight-fit garments.

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.

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.

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.

Study on Hydrodynamic Vibration in Dual Bluff Body Vortex Flowmeter

The characteristics of the dual bluff body vortex shedding is investigated, and the possibility to use dual bluff body combinations to strengthen the hydrodynamic vibration around the bluff body objects is explored. The numerical and experimental approaches were utilized to examine the time dependent flow field and the pressure oscillation around the bluff bodies. The numerical data were obtained by the advanced large eddy simulation model. The experiment was conducted on a laboratory scale of Karman vortex flowmeter with 40 mm diameter. It is revealed that the optimized dual bluff body combinations strengthened the hydrodynamic vibration. It was also found that the hydrodynamic vibration with 180° phase difference occurred at the axisymmetric points of circular pipe on the lateral faces of the equilateral triangle-section bluff bodies. Using the dual bluff body configuration and the differential sensing technique, a novel prototype of vortex flowmeter with excellent noise immunity and improved sensibility was developed.

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.

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.