Numerical Simulation And Experimental Verification Of Icing Form On Transmission Lines Based On Fluid Dynamics

The mechanism of icing on conductor is still a technical problem at home and abroad which urgently needs to be solved. The icing on conductor contains multiple disciplines of knowledge that relates to fluid dynamics, thermodynamic and electromagnetism. Although the discipline of rime ice is relatively mature, the micro-physical processes of thermal equilibrium on glaze ice surface and mathematical physical model have not been developed substantially. From the point of view of fluid dynamics, this paper establishes a time-varying icing model that contains motion characteristics of super cooled droplets and thermodynamic process. In the model, the microscopic mechanism of icing processes on conductor has been studied. The achievements have important theoretical and engineering application value for icing prediction, which also can be further providing related data on conductor twisting and galloping.Three fundamental steps of numerical simulation on icing accretion(calculation for flow field, trajectories and impingement characteristics of droplets, thermodynamic equilibrium equations and Icing form calculation) are respectively investigated. Firstly a conductor wind tunnel model is built, and the air flow field around conductor before and after icing is analyzed by fluid dynamics software FLUENT. Then the data of the wall static pressure and air velocity flow field can be exported. In order to find out the local collision efficiency of droplets on object surface, the equations of motion of water droplets in the air are set up according to Lagrangian method, and solved by fourth order Runge-Kutta algorithm. After the impingement characteristics of droplets are verified to be available, the local collision efficiency of multi-droplets size distribution is introduced based on the mono-droplets. A series of equations of mass and energy balance are established based on improved Messinger thermodynamic model. The key parameters f and Ts are obtained by using an iterative technique, so as to solve the icing quality mso. Finally, an icing forms calculation with different time step is achieved according to Macklin density formula.A fixed variable method is used for icing simulation with different temperature, wind speed, droplet diameter, liquid water content and conductor diameter, from which we can know how they affect icing types and forms. Finally, an array of icing experimental tests on cylinder is carried out under three typical temperatures. In particular, the ice shapes from both test results and model simulations are illustrated and compared within this thesis so as to validate the icing model. It shows that the icing area, thickness and shapes predicted by icing model are in satisfactory agreement with those obtained from experimental tests. In summary, it may be concluded that the icing model is valid with good prediction performance.