Numerical Study On 3D Ice Accretion On The Aero-engine Entry Components Under The Influence Of An Inlet

When an aircraft flies in the atmosphere containing super-cooled water droplets or flies through the clouds, super-cooled water droplets will directly impinge on the wing and cockpit windshield of the aircraft or impinge on the surface of struts and the spinner of the aero-engine after flowing through the inlet. The breakup of water droplets after their impingement will result in ice accretion on the up wind surface. In terms of aero-engines, icing can cause the decrease of engine's air flowing area and engine's thrust. Vibration and noise will follow the icing on the surface of the engine's rotor. Once sucked into the engine, shedded ice particles will damage the compressor blades or even lead to failure of the whole engine. At present, domestic and overseas three-dimensional numerical simulation of ice accretion is mostly based on the wing or a simple spinner as the geometric model and takes the uniform air flow as the boundary conditions of the two-phase flow field around the geometric model. Large error will be brought to the icing calculation of the aero-engine entry components due to the inlet influence on freezing parameters, which is not taken into account in above method. In this article, a type of serpentine inlet and a typical turbofan engine entry section were taken as the geometric model to study the icing characteristic on the surface of the aero-engine entry components under the influence of inlet and an automatic update approach for grid due to the growth of ice thickness was developed.Firstly, two-phase flow of air and water droplets in the serpentine inlet was calculated using the Eulerian-Eulerian approach and icing parameters changing regularities along the inlet were analyzed at the Mach number 0.3. Thus the flow field distribution features at the out plane of the inlet was obtained. The result shows that a local lower liquid water content area have appeared at a specific location of the out plane of the inlet by reason of the passage secondary flow when air and water droplets flows through the serpentine inlet. In addition, the droplets velocity in that area is lower than the values at other locations around.Secondly, secondary development of the dynamic mesh function of Fluent software was implemented in this article to realize automatic mesh movement due to ice thickness growth in the process of numerical simulation of icing. Ice accretion on the surface of the strut in the entry section of a typical turbojet engine was taken as an example to test the mesh movement method. The test result proved that this method could quickly and effectively realize the automatic update of grid and guarantee a good vertical degree at the first layer of grid near the wall.Finally, the flow field data was extracted from the out plane of the inlet and taken as the boundary conditions of the entry of a kind of large bypass ratio turbofan aero-engine that imitated the CFM56-C, and then two-phase flow of air and water droplets was simulated using the EulerianEulerian approach. After the flow field calculation ended, a kind of coupled solving method of ice thickness growth and water film flowing was used to simulate the three-dimensional ice accretion on the surface of struts and the spinner located in the aero-engine entry section and obtain the water droplets impingement features, ice shapes at different instants of time and the distribution of icing. The result shows that the mass of ice accreted on the strut, which is perpendicular to symmetric plane of the inlet, is the largest compared with other struts at the same moment. The lower surface and leading edge of that strut is the main icing area. The region, which is located on the lower surface of the spinner and near the conical tip, is the main icing area of the spinner while the rear and most of the upper surface of the spinner has no ice accreted on it.