Papers by Keyword: Ice Accretion

Abstract: 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.

Abstract: Ice accretion on 3D complex configuration is studied by numerical methods. The flow field is obtained by using Fluent 6.0 with a S-A turbulence model. Droplet trajectories and impingement characteristics are obtained by using the Eulerian approach. Ice shape is calculated based on the improved Messinger model with a new runback distribution scheme. By applying the method presented in this paper, ice accretion on NACA0012 is computed and the results are in good agreement with the available experiment data. It preliminarily shows that the improved method in this paper is feasible, Meanwhile, ice accretion on a four-element wing is studied. According to the analysis of the calculated result, the method presented in the paper can correctly simulate the ice accretion on 3D complex configuration.

Abstract: To increase the prediction speed of ice accretion on the 3D engine inlet, the Proper Orthogonal Decomposition (POD) method was introduced. Taking the ice shapes from CFD numerical calculation results as samples, in view of the change of icing temperature, the procedures of predicting the ice shapes by POD method were introduced, which used ice shapes’ coordinates and ice accretion height as compute parameters, respectively. The POD and CFD ice shapes were found coincident, which indicates that the POD method can fast and accurately calculate the 3D engine inlet ice shapes. The results from the two different POD parameters were shown and compared, and the ice shapes were nearly the same, which means they have the same effect. However, the POD method based on ice accretion height is simpler and more appropriate

Abstract: For conductor commonly used in power project, research was conducted on its ice accretion and aerodynamic characteristics. Ice mass and ice shape were examined under various icing condition: time, temperature and wind speed. Ice mass increases linearly with time, while the growth rate varies significantly with wind speed. Ice mass does not increase with the fall of temperature; it reaches the max value in a relatively high temperature range of-5°C~-10°C. Ice shape and ice thickness are both important factors that determine conductors aerodynamic characteristics. Sudden increase of lift coefficient may happen at low attack angle for conductor with thick crescent ice shape.

Abstract: Aircraft icing cause significant degradation in aerodynamics performance and flight safety. Numerical methods are developed and presented to simulate two icing-related problems for airfoils, namely ice accretion and icing effects. Ice accretion on the leading edge of the NACA 0012 airfoil is predicted using CFD method based on spring analogy. A four-order Runge-Kutta method is used to solve the droplet trajectory equation. Besides, we use the integral form of Navier-Stokes equations and the Spalart-Allmaras turbulence model to study the icing effects. Designing three different icing models, the flow fields are analyzed. The results are in good agreement with the experimental data and show preliminarily that numerical method is feasible and effective.

Abstract: A design approach of ice detection system for wind turbine is presented in this paper. Basic steps for design are proposed. Numerical arithmetic used for design configuration and shape of the icing prober is given. The arithmetic is composed of the Multiple Reference Frame (MRF) method to calculate flowfield of air, a Lagrangian method to compute droplet trajectories and a technique for fast computing ice accretion. Icing prober configuration for a 1.5 MW horizontal axis wind turbine is then obtained with the approach. The state of wind turbine icing can be reflected by the prober in real time. All these achievements build a good base for future research.

Abstract: An improved model for heat transfer process is established to study the ice accretion on airfoil, which takes into consideration the influence of conduction through ice and water film compared with the classical Messinger model. Incorporating the calculation of collection efficiency by the Eulerian two-phase theory, ice accretion in specific condition on a NACA0012 airfoil is simulated with the classical model and the improved model respectively. It is shown that the simulation result with the improved model agrees well with experiment data, and the model is demonstrated to be valid in ice shape prediction and complement the shortage of the Messinger model in the estimation of freezing fraction in glaze ice condition, especially in the initial stage of ice accretion.

Abstract: A three dimensional numerical method and its computer codes, which are suitable to predict the process of horizontal axis wind turbine icing, are presented. The method is composed of the Multiple Reference Frame (MRF) method to calculate flowfield of air, an Eulerian method to compute collection efficiency and a three dimensional icing model companying with an iterative arithmetic for solving the model. Ice accretion on a 1.5 MW horizontal axis wind turbine is then computed with the numerical method, and characteristics of droplet collection efficiency and ice shape/type are obtained. The results show that ice on the hub and blade root is slight and it can be neglected comparing with ice near blade tip. From blade tip to root, ice becomes thinner and glaze ice may changes into rime ice.

Abstract: Ice accretion on aircraft components is an enormous threat to flight safety. In this paper, ice accretions on the leading edge of the NACA 0012 airfoil and the NLR 7301 multi-element airfoil with flap are predicted using the icing code developed by us. This code mainly contains five modules which are grid module, airflow module, droplet module, heat module, and boundary reconstruction module. The effectiveness and robustness of this code are tested by executing the five modules orderly and repeatedly. The Spalart-Allmaras one-equation turbulence model is adopt to calculate the viscous airflow field and the four-order Runge-Kutta method is used to solve the droplet trajectory equations. In order to enhance the efficiency of the icing calculations, the multi-block grid technique is integrated into the grid module. Based on the above methods, numerical results in both two cases are presented and the necessary comparisons with the experimental data are given in corresponding chapters. The computational results show that performance of the icing code is very good for the wide range of icing conditions.

Abstract: In connection with the process of glaze ice, prediction models about height and thickness of ice coating under uniform and non-uniform ice accretion of wire are presented by taking into account local collision efficiency, freeze coefficient and collection coefficient based on the existing model at home and abroad. The time-dependent ice models on the conditions of different median volume diameter of super-cooled droplets, wind speed and wire diameter are analyzed. Compared with the existing model, the proposed ice accretion model performed well in predicting ice’s weight and thickness. At the same time, it can give some lights on ice disaster and anti-icing design for power transmission lines.