进气道影响下发动机进口段三维积冰的数值模拟研究

发布时间：2018-09-18 06:55

【摘要】：飞机飞行于含有过冷水滴的大气或者穿过云层时,过冷水滴会直接撞击机翼和驾驶舱的挡风玻璃之上或者流经进气道后再撞击到航空发动机整流帽罩和支板表面。撞击后破碎的过冷水滴将在上述的迎风表面产生结冰,结冰的发生对于航空发动机而言将导致其气流流通面积的降低、推力的下降、由于转子结冰所带来的振动与噪声的产生、脱落的冰块被吸入发动机后还会损伤压气机的叶片并导致整个发动机的损坏。目前国内外对于三维积冰的数值模拟大都采用机翼或者单独的整流帽罩作为几何模型,将均匀的大气来流最为两相流场计算的边界条件。这样的处理由于并未考虑航空发动机前端的进气道对结冰参数的影响,将会给发动机进口部件的积冰计算带来较大的误差。本文将以一种蛇形进气道和典型涡扇发动机进口段作为物理模型来研究进气道影响下航空发动机进口部件的积冰特性,同时开发冰生长时的网格自动更新方法。首先,本文采用欧拉-欧拉法对亚声速蛇形进气道进行了空气-过冷水滴两相流场的计算,分析了来流马赫数0.3时结冰参数在进气道中的沿程变化规律,获得进气道出口的流场分布特征。计算结果表明空气和过冷水滴流经蛇形进气道后由于通道二次流的原因会在其出口的特定位置形成液态水含量较低的局部区域,同时该区域的水滴速度也低于周围其它位置处的数值。其次,本文对Fluent的动网格功能进行二次开发以实现积冰数值模拟过程中由于冰层增长所需的网格的自动更新。以典型的涡喷发动机进口段支板表面积冰为算例进行网格的移动方法的测试,测试结果证明该方法在满足壁面第一层网格一定垂直度的前提下能有效且快速地实现网格的自动更新。最后,本文提取进气道出口的流场数据作为一种仿CFM56-C型大涵道比涡扇发动机进口的边界条件并使用欧拉-欧拉法对其进口段进行空气-过冷水滴亮相流场的数值计算。之后基于流场的计算结果采用冰的生长和水膜流动耦合求解的三维积冰数值模拟方法对该发动机进口段的支板和整流帽罩进行积冰计算,获得迎风表面的水滴撞击特性、不同时刻的冰形或者结冰的分布情况。计算结果表明:同一时刻与进气道对称面垂直的支板表面积冰量最大,其下表面及前缘位置为主要的结冰区域,其它支板的积冰量都相对较小。整流帽罩的下表面靠近圆锥顶点的位置为主要的结冰区域,帽罩的后缘及上表面的绝大部分区域均未发生结冰。
[Abstract]:When an aircraft flies in the atmosphere containing subcooled water droplets or through clouds, the droplets will impact directly on the windshield of the wings and cockpit or flow through the intake port before hitting the surface of the aero-engine fairing and supporting plates. The broken subcooled water droplets after impact will freeze on the above upwind surface. The occurrence of ice formation will lead to the decrease of the airflow area and the decrease of the thrust of the aero-engine due to the vibration and noise caused by the icing of the rotor. Falling ice can also damage the compressor's blades and cause damage to the entire engine when sucked into the engine. At present, most of the numerical simulation of three-dimensional ice deposition at home and abroad uses the wing or a single fairing as the geometric model, and the uniform atmospheric flow is the boundary condition of the two-phase flow field calculation. Because the influence of the inlet port at the front end of the aero-engine on the icing parameters is not considered, the calculation of the ice accumulation in the inlet of the engine will lead to a large error. In this paper, a snake-shaped inlet and a typical turbofan engine inlet section are used as physical models to study the ice accumulation characteristics of aeroengine inlet components under the influence of intake ports, and an automatic grid updating method for ice growth is developed. Firstly, the air-subcooled water droplet two-phase flow field in the subsonic snake-shaped inlet is calculated by using Euler-Euler method, and the variation of ice formation parameters in the inlet at Mach number 0.3 is analyzed. The flow field distribution characteristics of inlet outlet are obtained. The results show that air and subcooled water droplets flow through the snake-shaped inlet, and because of the secondary flow in the channel, a local area with low liquid water content will be formed at the specific location of the outlet. At the same time, the velocity of water droplets in this area is lower than that in other locations around it. Secondly, in this paper, the dynamic grid function of Fluent is redeveloped to realize the automatic updating of the grid required by ice layer growth in the course of numerical simulation of ice deposition. The method of grid moving is tested by taking the surface area ice of the branch plate in the inlet section of a typical turbojet engine as an example. The test results show that this method can effectively and quickly realize the automatic grid updating under the premise of satisfying the vertical degree of the first layer grid on the wall. Finally, the flow field data of inlet outlet are extracted as a boundary condition for the inlet of a large ducted ratio turbofan engine similar to CFM56-C, and the flow field of the inlet section is calculated by using Euler-Euler method. Based on the calculation results of the flow field, a three-dimensional ice deposition numerical simulation method based on the ice growth and the coupled solution of the water film flow is used to calculate the ice accumulation of the branch plate and the fairing cap in the inlet section of the engine, and the impingement characteristics of the water droplet on the upwind surface are obtained. The distribution of ice or ice at different times. The results show that the surface area of the branch plate perpendicular to the symmetrical plane of the inlet at the same time is the largest, the lower surface and the leading edge are the main icing areas, and the ice accumulation of the other branches is relatively small. The position of the lower surface of the fairing cap near the top of the cone is the main icing area, and there is no ice on the back edge of the cap cover and most of the areas on the upper surface.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V231

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