Research On The Prediction Of Movement And Solidification Of Thin Water Film On A Rotating Surface And Icing Experiments

During the icing climate conditions,ice will accrete on the upwind surface of the aircraft due to the impact of supper-cooled water droplets.The accreted ice can be very dangerous for the flight.Ice can accrete on the stationary components like the fixed wings and inlet lip of the engine;it can also accrete on the rotating components such as rotor and spinner of the engine.The Coriolis force and centrifugal force can affect both the multi-phase flow of air and droplets outside the components,and the movement of the unfrozen water film on the rotating surface,which makes icing on the rotating surface physically different from icing on a stationary surface.With these backgrounds,in this thesis we developed a model for multi-phase flow of air and droplets in the rotating coordinate system based the model in the stationary coordinate system.We also developed a model for the flow and solidification of the thin water film on the rotating surface via the analysis of conservation of mass,momentum and energy.The solution scheme for the model was also given,based on which a software was developed.The features of icing on a rotor were numerically studied by using the developed software.We also studied the icing phenomenon on a rotating spinner in an icing research tunnel.The work of this thesis consists of three parts: model development,numerical simulation,and experimental research in an icing research tunnel.Model development:(1)Adapted the Eulerian multi-phase flow model into the simulation of the double phase flow of air and water droplets around the rotating surface.The effects of centrifugal force and Coriolis force on the movement of air and water droplets are considered in the model.Two different methods for calculation of water catching efficiency on the rotating surface were compared.(2)Developed a mathematic model for the move and solidification of the unfrozen water film in the rotating body-fitted non-orthogonal curvilinear coordinate system.The model was developed based on the analysis of the conservation of mass,momentum,and energy.And the effects of centrifugal force and Coriolis force on the movement of the film were considered.The solution for the model was also given.(3)A numerical simulation code,which was used to simulate the flow and solidification of the water film on a rotating surface,was developed based on the model and its solution scheme.The software's ability to predict the flow and solidification of the thin water film on a rotating surface was verified with the experimental data from literature.The results show that the software developed in this thesis can predict the flow and solidification of the thin water film on a rotor's surface well.Experimental research in an icing research tunnel: Research of ice accretion on a rotating spinner was done in an icing research tunnel with a scaled spinner model,based on the similar experimental theory for multiphase flow and ice accretion.A data analysis method and error analysis method was developed for the high speed camera recorded experimental data.In the experiment,we found that the ice accreted on the rotating spinner changes from "Uneven glaze ice" to "Particle ice" and to "Feather ice",with the increase of the rotating speed.And "Particle ice" and "Feather ice" was found to be formed due to the unsteady of the water film under the effect of centrifugal force.The data of ice profile on the rotating spinner from the experiment was also used to verify the software developed in this thesis,and results show that the software can predict the smooth ice accretion on the spinner's surface well,while when the ice shape changes to "Particle ice" or "Feather ice" the software no longer suits.Numerical simulation: The effect of rotating speed on ice accretion on the propeller(similar to rotor)was simulated by using the developed code.Results show that,rotating speed can affect the flow and solidification of the water film through rotating linear speed and centrifugal force.When the rotating speed is larger,the rotating linear speed at the same section of the propeller is larger,the inertia of the income water droplet is larger,the mass of the impinged water and the impact limits are larger,and the heat transfer coefficient is larger,which lead to a tendency of accretion of thicker ice on the section of the propeller.However,when the rotating speed is larger,the centrifugal force will be larger,which will drive the water film flow along the span direction.Therefore,there will less water on the surface,which will cause a tendency of accretion of less ice on the section of the propeller.The effect of rotating linear speed is larger than the effect of centrifugal force.