Numerical Investigation on Transmission Line Conductor Icing

2014 ◽  
Vol 672-674 ◽  
pp. 1105-1108
Author(s):  
Xian Yi ◽  
Han Jie Huang ◽  
Zhi Hong Zhou
Keyword(s):  
Wind Tunnel ◽  
Transmission Line ◽  
Numerical Method ◽  
Liquid Water ◽  
Droplet Diameter ◽  
Liquid Water Content ◽  
Ice Thickness ◽  
Ice Accretion ◽  
Protection Technology ◽  
Air Speed

Ice accretion on transmission line conductor exists widely in nature, which can bring a lot of hazards. It is important and necessary to obtain characteristics of ice on different conductors for analyzing ice hazards or developing ice protection technology. A numerical method based on CFD technology for predicting ice accretion on transmission line conductor was presented in the present paper. Ice accretion on a conductor with a diameter of 26 mm was then predicted with the numerical method and an icing wind tunnel experiment. The results showed that it was acceptable to use clear cylinder as actual conductor for icing study, and the numerical results were credible. The effects of droplet diameter, liquid water content, air speed and time on icing were then investigated with the numerical method. The law that ice thickness, limit and volume varied with different icing conditions was obtained, which built a good foundation for further research.

scholarly journals Icing Measurements on Fixed and Rotating Cylinders

1983 ◽  
Vol 4 ◽  
pp. 174-179
Author(s):  
P. McComber ◽  
J.-L. Laforte ◽  
D. Bouchard ◽  
D. D. Nguyen
Keyword(s):  
Transmission Lines ◽  
Liquid Water ◽  
Collection Efficiency ◽  
Droplet Diameter ◽  
Ice Accretion ◽  
Rotating Cylinders ◽  
Wind Velocities ◽  
Method Of Measurement ◽  
Temperature Constant ◽  
Water Contents

There is at present a need to develop a better technique for measuring the rate of icing on structures such as, for example, overhead transmission lines. For aircraft and helicopter icing, the most widely used method of measurement is the rotating cylinder. However, for measuring the icing of structures, this method is difficult to apply and also less accurate due to lower wind velocities. Different approaches are now being developed using fixed cylinders.Icing tests were conducted with fixed and rotating cylinders in a wind tunnel. The rate of icing was obtained through measurements of volume, accretion cross-section and time of deposition. Tests were made using five different liquid water contents and droplet diameter spectra, and four cylinder diameters, keeping the wind velocity and temperature constant. The rate of icing is presented as a function of the diameters of the fixed and rotating cylinders for each of the liquid water contents tested. Results indicate that at lower wind velocities the accretion rate is overestimated for the smaller rotating cylinders. This difference is probably due to the variation of the collection efficiency with diameter. From these results it is suggested that the rate of ice accretion on structures should be based on at least two fixed cylinders of different small sizes in order to take into account the effect of the collection efficiency.

scholarly journals Experiments on the Growth of Spongy Ice Near a Stagnant Point

1990 ◽  
Vol 36 (123) ◽  
pp. 143-150 ◽  
Author(s):  
G.S.H. Lock ◽  
I.B. Foster
Keyword(s):  
Air Temperature ◽  
Liquid Water ◽  
Cross Flow ◽  
Supercooled Water ◽  
Liquid Water Content ◽  
Air Temperatures ◽  
Stagnant Point ◽  
Air Speed ◽  
Temperature Liquid ◽  
Ice Fraction

AbstractThe paper presents experimental observations on the growth of spongy ice in the vicinity of the forward stagnation point of a disc situated in a cross flow containing supercooled water droplets. Following some preliminary observations, the discussion focuses on two quantities: the ice fraction and the rate of growth of the accretion. The data presented reveal the effects of air speed, air temperature, liquid-water content, and salinity. They also suggest two morphological regimes: at higher air temperatures, the growth appeared to be crystalline columnar; at lower temperatures, smaller crystals appeared to be randomly distributed, producing a mushy accretion.

scholarly journals Wind tunnel experiments on the retention of trace gases during riming: nitric acid, hydrochloric acid, and hydrogen peroxide

2011 ◽  
Vol 11 (6) ◽  
pp. 17447-17472
Author(s):  
N. von Blohn ◽  
K. Diehl ◽  
S. K. Mitra ◽  
S. Borrmann
Keyword(s):  
Hydrogen Peroxide ◽  
Wind Tunnel ◽  
Hydrochloric Acid ◽  
Liquid Water ◽  
Trace Gases ◽  
Supercooled Liquid ◽  
Liquid Water Content ◽  
Ice Particles ◽  
Trace Species ◽  
Ice Phase

Abstract. Laboratory experiments were carried out in a vertical wind tunnel to study the retention of different atmospheric trace gases during riming. In the experiments, the rimed ice particles floated in a laminar air stream carrying a cloud of supercooled droplets with radii between 10 and 20 μm. Ice particles, dendritic ice crystals, and snow flakes with diameters between 6 mm and 1.5 cm were allowed to rime at temperatures between −5 and −12 °C where riming mainly proceeds in the atmosphere and with cloud liquid water contents between 1 and 1.5 g m−3 which are values typically found in atmospheric mixed phase clouds. Three trace species were investigated, nitric and hydrochloric acid, and hydrogen peroxide. They were present in the supercooled liquid droplets in concentrations from 1 to 120 ppmv, i.e. similar to the ones measured in cloud drops. The chemical analyses of the rimed ice particles allow to determine the trace species concentration in the ice phase. Together with the known liquid phase concentration the retention coefficients were calculated in terms of the amount of the species which remained in the ice phase after freezing. It was found that the highly soluble trace gases nitric and hydrochloric acid were retained nearly completely (98.6 ± 8 % and 99.7 ± 9 %, respectively) while for hydrogen peroxide a retention coefficient of 64.3 ± 11 % was determined. No influence of the riming temperature on the retention was found which can be explained by the fact that in the observed range of temperature and liquid water content riming proceeded in the dry growth regime.

scholarly journals In-Cloud Icing in the Columbia Basin

2009 ◽  
Vol 137 (12) ◽  
pp. 4369-4381 ◽  
Author(s):  
Ronald M. Thorkildson ◽  
Kathleen F. Jones ◽  
Maggie K. Emery
Keyword(s):  
Transmission Line ◽  
Water Content ◽  
Transmission Lines ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Weather Data ◽  
Cloud Base ◽  
Columbia Basin ◽  
Electrical Transmission ◽  
Dewpoint Temperature

Abstract On 24 November 2005, 11 lattice steel towers of a high-voltage electrical transmission line running along the edge of an escarpment were damaged by an accumulation of rime on overhead ground wires. Cold air pooling in the Columbia basin of eastern Washington several days before the failure led to the formation of low-level fog and low clouds with temperatures below freezing at the elevation of the transmission line. The liquid water content profile of the cloud formed by air rising over Badger Mountain north of Wenatchee, Washington, is estimated using the air temperature, dewpoint temperature, and air pressure as measured at Wenatchee in the Columbia River valley below the line. Cloud median volume droplet diameters are estimated using typical droplet concentrations. The validity of the computed liquid water content is determined by comparing the measured cloud-base heights at Wenatchee with the calculated cloud-base heights. The mass and density of ice accreted on the ground wires and conductors of the transmission line are modeled using assumed wind speeds at the top of the escarpment with the estimated cloud properties. Results are compared with the density and mass of an ice sample retrieved from the field. This event is compared with other modeled in-cloud icing events from 1973 to 2007 using the period of record of Wenatchee weather data. This paper illustrates an approach for estimating the severity of in-cloud icing on the wires of transmission lines subject to cloud liquid water contents that have been enhanced by the local terrain.

scholarly journals Wind Tunnel Tests on Aerodynamic Characteristics of Ice-Coated 4-Bundled Conductors

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Li Xin-min ◽  
Nie Xiao-chun ◽  
Zhu Yong-kun ◽  
You Yi ◽  
Yan Zhi-tao
Keyword(s):  
Wind Tunnel ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Coated Conductors ◽  
Ice Thickness ◽  
Ice Accretion ◽  
Aerodynamic Coefficients ◽  
Wind Tunnel Tests ◽  
Moment Coefficient ◽  
The Moment

Wind tunnel tests were carried out to obtain the static aerodynamic characteristics of crescent iced 4-bundled conductors with different ice thicknesses, initial ice accretion angles, bundle spaces, and wind attack angles. The test models were made of the actual conductors and have a real rough surface. Test results show that the influence of wake interference on the drag coefficients of leeward subconductors is obvious. The interference angle range is larger than 20° and the drag coefficient curves of leeward subconductors have a sudden decrease phenomenon at some certain wind attack angles. The absolute value of the lift and moment coefficient increases with the increase of the ice thickness. In addition, the galloping of the iced subconductor may occur at the angle of wind attack near ±20° and the wake increases the moment coefficient. The variation of initial ice accretion angle has a significant influence on the aerodynamic coefficients. The aerodynamic coefficient curves exhibit a “moving” phenomenon at different initial ice accretion angles. The bundle spaces have a great influence on the moment coefficient of leeward thin ice-coated conductors. With the increase of ice thickness, the bundle spaces generally have little influence on the aerodynamic coefficients.

scholarly journals On the Use of Hot-Wire Anemometers for Turbulence Measurements in Clouds

2007 ◽  
Vol 24 (6) ◽  
pp. 980-993 ◽  
Author(s):  
Holger Siebert ◽  
Katrin Lehmann ◽  
Raymond A. Shaw
Keyword(s):  
Wind Tunnel ◽  
Flow Velocity ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Hot Wire ◽  
Mean Flow ◽  
Velocity Signal ◽  
Turbulence Measurements ◽  
Mean Flow Velocity

The use of a hot-wire anemometer for high-resolution turbulence measurements in a two-phase flow (e.g., atmospheric clouds) is discussed. Experiments in a small wind tunnel (diameter of 0.2 and 2 m in length) with a mean flow velocity in the range between 5 and 16 m s−1 are performed. In the wind tunnel a spray with a liquid water content of 0.5 and 2.5 g m−3 is generated. After applying a simple despiking algorithm, power spectral analysis shows the same results as spectra observed without spray under similar flow conditions. The flattening of the spectrum at higher frequencies due to impacting droplets could be reduced significantly. The time of the signal response of the hot wire to impacting droplets is theoretically estimated and compared with observations. Estimating the fraction of time during which the velocity signal is influenced by droplet spikes, it turns out that the product of liquid water content and mean flow velocity should be minimized. This implies that for turbulence measurements in atmospheric clouds, a slowly flying platform such as a balloon or helicopter is the appropriate instrumental carrier. Examples of hot-wire anemometer measurements with the helicopter-borne Airborne Cloud Turbulence Observation System (ACTOS) are presented.

scholarly journals Comparison of different droplet measurement techniques in the Braunschweig Icing Wind Tunnel

2021 ◽  
Vol 14 (2) ◽  
pp. 1761-1781
Author(s):  
Inken Knop ◽  
Stephan E. Bansmer ◽  
Valerian Hahn ◽  
Christiane Voigt
Keyword(s):  
Wind Tunnel ◽  
Mass Flow ◽  
Liquid Water ◽  
Measurement Techniques ◽  
Wind Tunnel Test ◽  
Cloud Droplet ◽  
Liquid Water Content ◽  
Liquid Droplets ◽  
Spray System ◽  
Phase Doppler Interferometry

Abstract. The generation, transport and characterization of supercooled droplets in multiphase wind tunnel test facilities is of great importance for conducting icing experiments and to better understand cloud microphysical processes such as coalescence, ice nucleation, accretion and riming. To this end, a spray system has been developed, tested and calibrated in the Braunschweig Icing Wind Tunnel. Liquid droplets in the size range of 1 to 150 µm produced by pneumatic atomizers were accelerated to velocities between 10 and 40 m s−1 and supercooled to temperatures between 0 and −20 ∘C. Thereby, liquid water contents between 0.07 and 2.5 g m−3 were obtained in the test section. The wind tunnel conditions were stable and reproducible within 3 % standard variation for median volumetric diameter (MVD) and 7 % standard deviation for liquid water content (LWC). Different instruments were integrated in the icing wind tunnel measuring the particle size distribution (PSD), MVD and LWC. Phase Doppler interferometry (PDI), laser spectroscopy with a fast cloud droplet probe (FCDP) and shadowgraphy were systematically compared for present wind tunnel conditions. MVDs measured with the three instruments agreed within 15 % in the range between 8 and 35 µm and showed high coefficients of determination (R2) of 0.985 for FCDP and 0.799 for shadowgraphy with respect to PDI data. Between 35 and 56 µm MVD, the shadowgraphy data exhibit a low bias with respect to PDI. The instruments' trends and biases for selected droplet conditions are discussed. LWCs determined from mass flow calculations in the range of 0.07–1.5 g m−3 are compared to measurements of the bulk phase rotating cylinder technique (RCT) and the above-mentioned single-particle instruments. For RCT, agreement with the mass flow calculations of approximately 20 % in LWC was achieved. For PDI 84 % of measurement points with LWC<0.5 g m−3 agree with mass flow calculations within a range of ±0.1 g m−3. Using the different techniques, a comprehensive wind tunnel calibration for supercooled droplets was achieved, which is a prerequisite for providing well-characterized liquid cloud conditions for icing tests for aerospace, wind turbines and power networks.

scholarly journals Experiments on the Growth of Spongy Ice Near a Stagnant Point

1990 ◽  
Vol 36 (123) ◽  
pp. 143-150
Author(s):  
G.S.H. Lock ◽  
I.B. Foster
Keyword(s):  
Air Temperature ◽  
Liquid Water ◽  
Cross Flow ◽  
Supercooled Water ◽  
Liquid Water Content ◽  
Air Temperatures ◽  
Stagnant Point ◽  
Air Speed ◽  
Temperature Liquid ◽  
Ice Fraction

AbstractThe paper presents experimental observations on the growth of spongy ice in the vicinity of the forward stagnation point of a disc situated in a cross flow containing supercooled water droplets. Following some preliminary observations, the discussion focuses on two quantities: the ice fraction and the rate of growth of the accretion. The data presented reveal the effects of air speed, air temperature, liquid-water content, and salinity. They also suggest two morphological regimes: at higher air temperatures, the growth appeared to be crystalline columnar; at lower temperatures, smaller crystals appeared to be randomly distributed, producing a mushy accretion.

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