Flow characteristics of V-Cone flowmeter in wet steam
Wet steam is a common two-phase flow whose mass flow-rate can be measured by V-Cone flowmeter. The mass flow coefficient CD of V-Cone is no longer approximately constant which affects the measuring accuracy subject to the complex flow characteristics of wet steam and discrete droplets. Firstly, five main impact factors for CD of V-Cone were obtained by dimensional analysis, namely, vapor Reynolds number, liquid-vapor density ratio, mass loading ratio, potential to kinetic energy ratio and dimensionless droplet diameter respectively. Then CFD simulation was carried out to study the influence of these parameters. Eulerian multiphase model and SST k-ω turbulence model were adopted for steady simulation. The simulation results coincided well with the experimental results. The results indicate that CD is almost not affected by vapor Reynolds number and potential to kinetic energy ratio; it increases with the liquid-vapor density ratio, mass loading ratio and dimensionless droplet diameter, among which mass loading ratio is the main factor.
Online measurement of gas and liquid flow rate in wet gas through one V-Cone throttle device
Abstract In the present study, an accurate cost-effective online system for metering both the gas flow rate and the liquid flow rate in wet gas with only one V-Cone throttle device is developed. The two-phase mass flow coefficient is employed to correct the measurement deviation of the V-Cone throttle device. The effects of the liquid densiometric Froude number, the gas densiometric Froude number and the ratio of gas density to liquid density on the two-phase mass flow coefficient are experimentally investigated. The equivalent diameter ratio of the V-Cone throttle device is 0.55. The experimental fluids are air and tap water. The operating pressure, the superficial gas velocity and superficial liquid velocity range from 0.1 MPa to 0.3 MPa, 4.87 m/s to 25.26 m/s and 0 to 0.38 m/s, respectively. The results show that the two-phase mass flow coefficient linearly increases with the liquid densiometric Froude number and is affected by the gas densiometric Froude number and the ratio of gas density to liquid density. On the basis of the two-phase mass flow coefficient, the correlation for measuring the gas flow rate of the wet gas is developed. To reflect the influences of the liquid on the measurement, the pressure loss ratio of the V-Cone throttle is proposed. By incorporating the gas measurement correlation of the wet gas, the wet gas correlations to simultaneously meter the gas and liquid flow rate are concluded. In the present cases, the relative error of the gas mass flow rate predicted by the correlations is within ±5.0% and the mean absolute percentage error is 2.52%; the full scale relative error of the liquid mass flow rate is within ±5.0% and the mean absolute percentage error is 7.03%. The method proposed in this study creates a simple inexpensive wet gas metering system that can operate well in a significant range of industrial applications.
Simulation and Experimental Research on the Expansibility Factor for Cone Flowmeters with L-Cantilever
In order to acquire a higher accuracy mathematical model of expansibility factor for cone flowmeters with L-cantileve,a set of test prototypes with the equivalent diameter ratios of 0.45,0.55,0.65,0.75 and 0.85 respectively were designed. Using computational fluid dynamics(CFD)method,a simulation research for the expansibility factor was carried out, resulting in a CFD predictive equation of the expansibility factor. Meanwhile,a fitting equation of the expansibility factor was obtained from the corresponding experimental research,which was completed on the gas flow calibration device based on the critical flow sonic nozzles using the positive pressure method. Comparing the two predictive equations and the experiment results respectively,the average and the biggest values of the relative error of CFD predictive equation are 0.77% and 1.66% respectively. As for the experiment predictive equation,0.25% and 0.42% respectively. Besides,the square averaged root error was also analyzed as following:the average and the biggest values of CFD predictive equation are 0.92% and 1.97% respectively;as for the experiment predictive equation,0.30% and 0.51% respectively.