Numerical Simulation Of Ice Accretion On Aero-engine Entry Components

Ice accretion may occur on the entry components of an aero-engine, such as the struts and the centre conical body under some meteoric and flight conditions. Once the ice becomes thicker and thicker, the mass flow rate of airflow would reduce, that would lead to engine performance deterioration. If the ice accretes severely, the engine couldn't work normally and even endanger the aircraft. What is worse is that ice accretion on the aero-engine entry components would occur at some special meteoric conditions under which there would not be ice accretion on the airfoil of aircraft. In order to understand the effect of icing parameters (such as Medial Valid Diameter (MVD), velocity, and Liquid Water Content (LWC) of super-cooled water droplets) on ice accretion on entry parts of aero-engine, a numerical study is conducted in this thesis.The main research work in this thesis is as followings:(1) A wide and deep literature review is presented on the research status and trends of aircraft and aero-engine icing accretion, which includes both experimental and numerical studies, and especially the advance in numerical simulation is emphasized.(2) The computation method of two-phase flow of air and super-cooled water droplets based on Euler-Euler method is investigated. The control equations of the two-phase flow in Cartesian coordinates system are transformed into arbitrary curvilinear coordinates. The calculation methods are studied, which include the discretization of the control equations, the implementation of turbulent model and wall function for airflow, the generation of gird, and the solving procedure of the two-phase flow. The computer code based on these methods is developed for two dimensional flow.(3) The computation method for two-phase flow based on Euler-Lagrange method is investigated. The control equations for water droplets motion, based on particle random trajectory model, are derived for the arbitrary curvilinear coordinates. The numerical simulation techniques for solving the equations are discussed. A statistical method is proposed to calculate the water collection efficiency when the particle random trajectory model is used to simulate the motion of super-cooled water droplets. With this method, the mass flow rate of water droplets entering into every control volume on the impacting surface are calculated by summing every water droplet that enters into the control volume. The computer code of the statistical method is developed.(4) A two-dimensional icing model in which both mass and energy conservation are considered is established based on Messinger icing model (one dimensional, only energy conservation is considered). The energy-balancing equations for rime icing, glaze icing and mixed icing are derived respectively. The icing prediction method is presented, in which the icing type is determined by a presupposition-rectification process. Then the idea of used in the icing model of LEWICE 1.6 is introduced, in which the effects of the shedding of super-cooled water droplets after impinging and effects of surface tension on the runback water are considered. The computer code for icing is developed.(5) By integrating the icing computation code and the two-phase flow simulation code, a two-dimensional ice accretion prediction code is developed, in which the air-droplet flow computation is base on Euler-Euler method. By integrating the icing computation code and the two-phase flow simulation module of commercial software FLUENT which base on Euler-Lagrange method, a computation method and relevant computer code are developed.(6) The numerical investigation of water collection efficiency and ice accretion on the struts of aero-engine is carried out with the developed two-dimensional ice accretion prediction code. The effects of MVD, velocity, LWC of droplets and surrounding temperature on water collection efficiency, ice accretion rate and ice shape are studied.(7) The numerical study of water collection efficiency and ice accretion on the centre conical body of aero-engine is conducted with the proposed method integrating icing code and air-droplet flow computation molule of FLUENT. The effects of MVD, velocity, LWC of droplets, surrounding temperature and rotate speed of centre conical body on water collection efficiency, ice accretion rate and ice shape are analyzed.