Application of variable area cavitating venturi as a dynamic flow controller

The variable area cavitating venturi is an effective means to throttle the mass flow rate of liquid. The mass flow rate is a function of the upstream pressure, the pintle stroke, the density and saturation pressure of the liquid, independent of the downstream pressure. In this paper, a variable area cavitating venturi is designed and four different sets of experiments are conducted to investigate the performance of the variable area cavitating venturi. In these experiments, the mass flow rates are examined under different pintle positions, upstream pressures, downstream pressures and dynamic motions of the pintle. The experimental results indicate that the mass flow rate is independent of the downstream pressure when the ratio of the downstream pressure to upstream pressure is less than 0.8. The mass flow rate is almost linearly dependent on the pintle stroke for a constant upstream pressure. The discharge coefficient is a function of the pintle stroke, whereas the upstream and downstream pressures have rare influence on the discharge coefficient. The variable area cavitating venturi can control and measure the mass flow rate dynamically by determining the pintle stroke and the upstream pressure.     

An investigation of a cavitating venturi flow control feature in a cryogenic propellant delivery system

This study details the design and performance characterization for a cryogenic cavitating venturi. This flow control system is intended for mass flow regulation of cryogenic propellants, such as liquid oxygen and liquid methane, in reaction control propulsion systems. Through in situ flow tests, the discharge coefficient for the venturi was calculated and utilized to determine the mass flow rate for specified inlet pressures of the propellants. The test results revealed that the cavitating venturi indeed performed as a flow rate control feature in both liquid water and LCH₄ flow under a steady state operating within pressure ratios below 0.69.     

Experimental and numerical investigation on the performance of small-sized cavitating venturis

Cavitating venturis (CVs) are simple devices which can be used in different industrial applications to passively control the flow rate of fluids. In this research the operation of small-sized CVs is characterized and their capabilities in regulating the mass flow rate were experimentally and numerically investigated. The effect of upstream and downstream pressures, as well as geometrical parameters such as the throat diameter, throat length, and diffuser angle on the mass flow rate and critical pressure ratio were studied. For experimental data acquisition, three CVs with throat diameters of 0.7, 1 and 1.5 mm were manufactured and tested. The fabricated CVs were tested at different upstream and downstream pressures in order to measure their output mass flow rate and to obtain their characteristic curves. The flow inside the CVs was also simulated by computational fluid dynamics. The numerical results showed agreement with the experimental data by a maximum deviation of 5–10% and confirmed that the numerical approach can be used to predict the critical pressure ratio and mass flow rate at cavitaing condition. It is found that despite the small size of venturis, they are capable of controlling the mass flow rate and exhibit the normal characteristics. By decreasing the throat diameter, their cavitating mode became more limited. Results also show that increasing the diffuser angle and throat length leads to a decrease in critical pressure ratio.     

Experimental investigation of a cavitating Venturi and its application to flow metering

An experimental investigation has been carried out to evaluate the performance of a cavitating Venturi flow. For that purpose, a closed loop circuit with a centrifugal pump and a transparent asymmetric converging-diverging test section has been built which allows to set the pressure level and the flow rate. The system is instrumented with several pressure sensors and temperature probes that are continuously monitored during the tests. The experiments have consisted in generating non-cavitating and cavitating flows inside the Venturi under controlled conditions. The obtained results, which have been characterized as a function of the Venturi's discharge coefficient, pressure ratio and pressure loss coefficient, are in good agreement with previous studies carried out with standard Venturi geometries, specially under non-cavitating flows. The Venturi's performance under cavitation flows has been found to be dependent on the Venturi's inlet pressure and similar to a chocked flow condition with constant volumetric flow rate. On the basis of these observations and the analogous behaviour with compressible gas nozzles, a new flow coefficient has been derived which remains constant at any cavitating regime. Thus, this coefficient permits to use a Venturi as a flow meter on cavitation conditions.     

Flow measurement and instrumentation flow control characteristics of throttling venturi valve with adjustable area

In this study, a throttling venturi valve with adjustable area was designed to control the thrust of a monopropellant thruster using hydrogen peroxide. The flow rate control characteristics of the throttling venturi valve were investigated based on the pintle stroke and upstream pressure of the venturi. Three kinds of experiments were conducted: pressure and flow rate measurement according to pintle stroke and venturi upstream pressure, determination of critical pressure ratios under various conditions, flow rate control performance through open-loop control and feedback control of an actuator. The pressures were measured at the upstream, throat, and downstream of the venturi. It was observed that the flow rate changed in proportion to the stroke and upstream pressure. Below a stroke of 10 mm, the critical pressure ratio gradually decreased as the stroke and upstream decreased. However, above a stroke of 10 mm, the critical pressure ratio converged to a value between 0.7 and 0.8 regardless of the upstream pressure. The results of automatic flow rate control tests using open-loop control and feedback control showed that the measured flow rate satisfactorily followed the target flow rate profile.     

Novel mass air flow meter for automobile industry based on thermal flow microsensor. II. Flow meter,test procedures and results

A prototype of mass air flow meter for automobile industry was developed on the basis of thermal flow microsensor. Design and manufacturing technology of the flow meter are described. Test procedure and results are presented. Developed prototype of flow meter can diagnose gas flow rates in a wide range.     

Theoretical and experimental investigation for developing a gas-liquid two-phase flow meter

Despite the intricacy, inline metering of two-phase flow has a significant impact in multitudinous applications including fusion reactors, oil, nuclear, and other cryogenic systems. Since measurement of individual flow rate is prominent in various systems, it warrants the establishment of a flow meter system that can monitor the mass flow rates of liquid. In this regard, an approach was taken towards the development of a two-phase flow meter system in the present study. The concept involves two-phase flow through narrow parallel rectangular channels resulting in laminar, stratified flow with a slope at the liquid-vapor interface. The height of the liquid column at specific channel locations is measured for determining the flow rate. However, the geometric configurations of the channels and fluid properties are pivotal in ensuring accurate measurement. Consequently, theoretical and experimental studies are performed to investigate the correspondence between flow rate and change in liquid height. Based on the governing equations, a theoretical model is established using MATLAB®. The model investigated the intricate influence of various flow and fluid properties in the estimation of the mass flow rate. The experimental investigation was done with various conditions under different liquid and vapor volume flow rates for validating the proposed supposition and the theoretical model. Both the theoretical and experimental analyses showed fair correspondence. The proposed system estimated the mass flow rate within a tolerance of ±10% and showed potential towards the development of the cryogenic two-phase flow meter.     

Model analysis for differential pressure two-phase flow rate meter in intermittent flow

Multiphase flow rate metering is a challenging problem, specially for flow patterns other than wet-gas. This paper brings forward a new comparative analysis of three differential pressure calibration models suited for liquid dominated two-phase flows, in a total of seven model configurations. First, the models are compared theoretically and classified in terms of the type of input data required. Then, experimental data of over 300 horizontal air–water experiments, for $1$” and $2$” pipe diameters, supports quantitative analyses of the prediction accuracies and sensitivity of the superficial velocities of gas and liquid to measurement errors in the model input variables. Finally, a method for assessing the decoupled measurement errors for the void fraction and gas velocity is shown, as these variables are typically subject to higher uncertainties. It results that, though the void fraction is shown to be systematically under evaluated in more than 10%, the total mass flow rate is estimated through the Paz et al. (2010) model with an overall root mean squared deviation (RMSD) of 5.75% for the $2$” data. Also, the use of gas velocity measurements, even if subject to considerable errors, decreased the RMSD for the gas superficial velocity by more than half for the $1$” data.     

Measurements of the flow of supercritical pressure carbon dioxide through Venturi flow meter

The Venturi flow meter exhibits relatively low pressure loss, simple design, and low manufacturing costs. This study describes flow rates measurements for supercritical pressure CO₂ using the Venturi flow meter with pressure ranging 7.379–7.836 MPa and 5.84–7.272 MPa for in supercritical and gaseous regions, respectively. The flow rates of supercritical pressure CO₂ were accurately measured using a Venturi flow meter with a diameter ratio of 0.6468, having large and small diameters of 87.32 mm and 56.48 mm, respectively. The convergent and divergent angles were 21 $°$ ± 1 $°$ and 15 $°$ ± 1 $°$, respectively. The averaged discharge coefficient of 0.9975 was obtained, which was independent of the pressure ratio. Additionally, the expansion factors were also calculated using the experimental results, which ranged from 0.99976 to 0.99987 and 0.99945–0.99995 for the supercritical and gaseous regions, respectively. The experimental results showed that the Venturi flow meter had uncertainties ranging from 0.1 to 2.8%.     

基于模糊PID控制器的流量控制设计

现今流量控制系统很多都使用常规PID控制器,这样虽然比较方便,但不能在线整定参数,因而不能很好地控制非线性等复杂系统.在本系统中,采用模糊PID控制器来设计控制流量.模糊PID控制器将PID控制和模糊控制两种方法结合起来,既能消除稳态误差,又能对复杂系统进行简单有效的控制,从而达到控制要求.     

A novel technique of using a thyristor driven pump as the final control element and flow indicator of a flow control loop

In the present paper, design of a flow control loop using a thyristor driven pump as final control element has been described. In this technique, the load current of a thyristor driven pump motor has been utilized as a mass flow sensing parameter of a fluid passing through a pipeline. This thyristor driven pump has been utilized as a final control element of a flow control loop and the speed of the pump has been selected as the manipulated variable. The non-linearity between the thyristor input signal and pump output has been eliminated by using a modified PID control technique with inverse derivative control action. Thus without using any conventional flow meter and control valve only the thyristor driven pump has been utilized both as the final control element and flow indicating device by using the proposed technique. The whole system has been designed, fabricated and tested by using tap water as the flowing liquid through a pipe line. The experimental results along with the theoretical analysis are compared and reported in the paper.     

Blow-down calibration of a large ultrasonic flow meter

Oil and gas production industries use large (diameter > 0.8 m) ultrasonic flow meters (USMs) to measure exhaust gas from flare stacks, emissions from smokestacks, flow of natural gas, etc. Since most flow laboratories do not have compressors with sufficient flow capacity (>10 kg/s) to calibrate large flow meters, calibrations are performed using the blow-down method where flow is generated by discharging high pressure tanks, leading to significant flow transients. We used an array of critical flow venturis (CFVs) in a blow-down facility to calibrate a large (D = 89.5 cm) 8-path ultrasonic flow meter. The flow transients associated with the blow-down process caused large spatial and temporal variations in temperature that dominated (40%–67%) the uncertainty budget. Our uncertainty analysis accounts for transient-generated uncertainties and provides guidelines for improving blow-down calibrations of large flow meters.     

Development of a transfer standard with sonic Venturi nozzles for small mass flow rates of gases

We have developed a transfer standard system with sonic Venturi nozzles for small mass flow rates of gases. The system is composed of a newly developed automatic pressure controller, two pressure sensors and one temperature sensor to measure the flow conditions in the upstream and downstream sides of a nozzle. The whole system is packed in a portable aluminum trunk. The data are sent to a laptop computer, and the results are displayed on the screen and are written to files. The system can calibrate a flow meter in the flow rate range from 10 mg/min to 100 g/min using ten different sonic Venturi nozzles with the expanded standard uncertainty (k=2) being less than 0.2% for nitrogen. Examples of mass flow controller calibrations are given.     

Experimental investigation of gas-liquid flow in a vertical venturi installed downstream of a horizontal blind tee flow conditioner and the flow regime transition

A venturi device is commonly used as an integral part of a multiphase flowmeter (MPFM) in real-time oil-gas production monitoring. Partial flow mixing is required by installing the venturi device vertically downstream of a blind tee pipework that conditions the incoming horizontal gas-liquid flow (for an accurate determination of individual phase fraction and flow rate). To study the flow-mixing effect of the blind tee, high-speed video flow visualization of gas-liquid flows has been performed at blind tee and venturi sections by using a purpose-built transparent test rig over a wide range of superficial liquid velocities (0.3–2.4 m/s) and gas volume fractions (10–95%). There is little ‘homogenization’ effect of the blind tee on the incoming intermittent horizontal flow regimes across the tested flow conditions, with the flow remaining intermittent but becoming more axis-symmetric and predictable in the venturi measurement section. A horizontal (blind tee) to vertical (venturi) flow-pattern transition map is proposed based on gas and liquid mass fluxes (weighted by the Baker parameters). Flow patterns can be identified from the mean and variance of a fast electrical capacitance holdup measured at the venturi throat.     

Multiphase flow measurements using coupled slotted orifice plate and swirl flow meter

Multiphase flow metering is a major focus for oil and gas industries. The performance of a modified version of a close coupled slotted orifice plate and swirl flow meter for multiphase flow was evaluated to provide further development of a new type of multiphase flow meter. The slotted orifice provides well homogenized flow for several pipe diameters downstream of the plate. This characteristic provides a homogeneous mixture at the inlet of the swirl meter for a wide range of gas volume fractions (GVF) and flow rates. In order to evaluate the performance of the designed flow-meter, its response was investigated for varying pressures and water flow rates. The proper correlations were established to provide high accurate two-phase flow measurements. The new proposed approach provides the GVF measurement with less than ±0.63% uncertainty for GVF range from 60% to 95%.     

温差为源信号的流量控制器

本文介绍一种温差为源信号的流量控制器．是用于采暖供热系统中调控同轴差速式热量表两个固定式叶轮腔中流量的控制装置。由设置于进．出水流腔体内的一对装有饱和蒸汽工质的密闭腔体通过同轴密封联接的弹性波纹管带动串联于卸流旁路中的节流阀的阀芯相对阀壳滑动．从而改变节流阀的开度，达到用两个流体腔内的温度差间接控制出水流道中的流量，使进、出水流道产生相应的流量差．以达到准确热计量的目的。控制器由机械组件构成，自动运作，不依赖外部能量，工作稳定可靠。     

Optimal design and development of electromagnetic linear actuator for mass flow controller

In this paper, we constructed the analytic model of control valve as a function of electric and geometric parameters, and analyzed the influence of the design parameters on the dynamic characteristics. For improving the dynamic characteristics, optimal design is conducted by applying sequential quadratic programming method to the analytic model. This optimal design aims to minimize the response time and maximize force efficiency. By this procedure, control valve can be designed to have fast response in motion.     

Experimental investigation on characteristics of venturi cavitating flow and Rhodamine B degradation in methanol solution

Hydrodynamic cavitation (HC) commonly occurs within industrial pipelines and its unsteady flow characteristics are of great significance for energy conservation and efficiency improvement. This study investigates the effects of methanol concentration (0–20 wt%) on the cavitating flow characteristics and the degradation of Rhodamine B (RhB) under operating conditions of a 0.7 MPa pressure drop, temperature of 30 °C, 200 passes through a venturi reactor, and an initial RhB concentration of 40 μmol/L. The transient cavitation behavior was monitored using a high-speed camera. The cavitation images show that the presence of methanol generates more stable bubbles, which results in less violent bubble collapse. The pressure pulsation and vibration induced by cavitation flow were synchronously measured using high-frequency pressure and acceleration sensors. The spectral analyses of the pressure pulsation indicate that methanol has no effect on the dominant frequency (∼5.5 Hz) at different positions, and the amplitude initially increases with increasing methanol concentration and then stabilizes. The pressure pulsation intensity increases due to the increased vapor pressure of the solution. The vibration spectral analyses show that methanol has little effect on the peak frequencies, which occur near 4.0 kHz and 14.3 kHz of the low and high-frequency bands, respectively, whereas the peak amplitude decreases with increasing methanol concentration. The per-pass degradation model of RhB in methanol solution considering pyrolysis of methanol was verified for the first time and show to adequately describe the experimental data. The degradation percentage and per-pass degradation factor decrease with increasing methanol concentration. The reduced surface tension of the solution prolongs the bubble lifespan and prevents bubble coalescence, thus weakening the vibration and degradation performance. The results provide important insight for cavitation applications and degradation modeling of mixed solutions.     

A study of a pressure differential flow meter that is insensitive to inlet conditions

Orifice meters are a type of differential pressure flow meter widely used in industry and their behaviour is very well understood. The standard discharge coefficient can only be used if the flow approaching the meter is perfectly settled and fully developed. Thus the installation of these meters is subject to many constraints. Normally the required flow regime is established by the use of a combination of a flow conditioner and a settling length.

This paper describes the initial work carried out to show the concept of an orifice meter whose performance is independent of the inlet conditions by the introduction of a standard swirl before the meter. These results show that a swirler renders the measurements independent of the influence of upstream disturbance. This is for both a partial blockage in the pipe and also upstream swirl, and is likely to be universal.

A proposal for a new calibration equation is also made for the particular swirler employed. However, more data need to be acquired over a wide range of geometries, flow and operating conditions.     

配电站直流系统控制器设计

以PLC为核心处理器,实现对配电站直流系统进行自动化管理.具体分析了该系统的组成与功能,以及系统通信功能的实现,介绍了PLC的部分控制程序.