Simulation and Experimental Study of Break-Up Characteristics of Water Streams in Rod-Plate Air Gap under Heavy Rain Conditions

Under heavy rain conditions, the rain streams between the high-voltage wire and the tower is prone to break up, which causes the electric field distortion and reduces the electrical insulation performance of the wire-tower gap. In order to study the break-up characteristics of rain streams in air gap under heavy rain conditions, this paper took rain streams in the short air gap between rod and plane as the research object and established a two-dimensional non-axisymmetric simulation model developed by coupling the continuity equation, Navier-Stokes equation, electric field equation of an incompressible fluid. And then the morphology and stress of the rain streams during the break-up process was analyzed. The changes of break-up characteristic parameters under different external voltages and rain streams flow rates was calculated and studied. Finally, a rod-plane gap rain streams break-up test platform was established with nozzle electrode to carry out break-up characteristic test, and the simulation results were verified. On this basis, the influence law of DC voltage polarity on break-up characteristic parameters was further studied. The results showed that the break-up process of rain streams in the rod-plane gap is subject to the joint action of the electric force, surface tension and viscous force. The break-up process of rain-streams with rod-plane gap goes through three stages int turn: jet zone, transition zone and break-up zone. Increasing the applied voltage increases the spiral diameter of the rain streams, the number of break-up and the deformation degree of raindrops, and accelerates the spiral motion in the transition zone. Among them, the spiral diameter of the rain streams increases from 4.0 mm at 20 kV to 7.8 mm at 80 kV, the number of raindrops increases from 13 at 0 kV to 18 at 80 kV, and the ratio of the long to short axis of the raindrops increases from 0.88 at 20 kV to 2.3 at 80 kV. The critical break-up length and break-up diameter of the rain streams are linearly reduced with the increase of the applied voltage, and are positively correlated with the flow rates of the rain streams. The critical break-up length and diameter of the rain streams at 1.55 m/s flow rate under 80kV are reduced by 18% and 13% respectively. The critical break-up length of rain streams at negative polarity voltages are greater than those at positive polarity under the same conditions. The maximum radial surface tension of the rain streams decreases slightly with increasing applied voltage and is negatively correlated with the flow rates; the maximum radial electric force increases with the increase of applied voltage, and the larger the flow rates, the larger the force. The maximum radial electric force on the rain streams with a rate of 1.55 m/s increases from 3 684 N/m3 at 20 kV to 25 148 N/m3 at 80 kV, and when the rate of the rain streams increases from 1.25m/s to 1.55m/s at 80 kV, the maximum radial electric force increases by 86%. The experimental results of the break-up diameter and break-up length are in good agreement with the calculated values. At the flow rate v=1.25 m/s, the maximum deviation between the calculated results of the raindrops break-up diameter and the experimental value is less than 10%, the deviation of the critical break-up length is 9.6%, and the overall maximum deviation is less than 10%. © 2023 Chinese Machine Press. All rights reserved.