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.
Liquid Water Content and Droplet Sizing Shadowgraph Measuring System for Wind Turbine Icing Detection
This paper shows that the liquid water content (LWC) and the median volume diameter (MVD) can be derived from the images of water droplets using a shadowgraph imaging system with incoherent LED illumination. Icing on structures, such as a wind turbine, is the result of a combination of LWC and MVD, and other parameters, such as temperature, humidity, and wind speed. Today, LWC and MVD are not commonly measured for wind turbines. Systems for measuring these properties are often expensive or impractical in terms of location or remote reading. The aim of this paper is to gain knowledge about how to design a single instrument based on imaging that has the ability to measure these properties with enough precision and accuracy to detect icing conditions for wind turbines. A method to calculate both the LWC and the MVD from the same images is described in this paper. The size of one droplet is determined by measuring the shadow created by the droplet in background illumination. The concentration is calculated by counting the measured droplets and estimating the volumes in which these droplets can be observed. In this paper, the observation volume is shown to be dependent on the particle size and the signal-to-noise ratio for each measured particle. An expected coefficient of variation of the LWC depending on the droplet size is shown to be 2.4% for droplets 10 μm in diameter and 1.6% for 25-μm droplets. This is based on an error estimation of the laboratory measurements calibrated using a micrometer dot scale.
Substation automation based on IEC 61850 with new process-close technologies
New technologies in primary equipment like nonconventional instrument transformers require new interfaces to the substation automation system. The future standard IEC 61850 perfectly supports this requirement. With the introduction of the new technologies and the use of IEC 61850, a more decentralized architecture of the substation automation system will be possible. This provides several benefits but a careful system design is required to maintain the overall reliability of the system.