【摘要】：飛機飛行于含有過冷水滴的大氣或者穿過云層時,過冷水滴會直接撞擊機翼和駕駛艙的擋風玻璃之上或者流經(jīng)進氣道后再撞擊到航空發(fā)動機整流帽罩和支板表面。撞擊后破碎的過冷水滴將在上述的迎風表面產(chǎn)生結(jié)冰,結(jié)冰的發(fā)生對于航空發(fā)動機而言將導(dǎo)致其氣流流通面積的降低、推力的下降、由于轉(zhuǎn)子結(jié)冰所帶來的振動與噪聲的產(chǎn)生、脫落的冰塊被吸入發(fā)動機后還會損傷壓氣機的葉片并導(dǎo)致整個發(fā)動機的損壞。目前國內(nèi)外對于三維積冰的數(shù)值模擬大都采用機翼或者單獨的整流帽罩作為幾何模型,將均勻的大氣來流最為兩相流場計算的邊界條件。這樣的處理由于并未考慮航空發(fā)動機前端的進氣道對結(jié)冰參數(shù)的影響,將會給發(fā)動機進口部件的積冰計算帶來較大的誤差。本文將以一種蛇形進氣道和典型渦扇發(fā)動機進口段作為物理模型來研究進氣道影響下航空發(fā)動機進口部件的積冰特性,同時開發(fā)冰生長時的網(wǎng)格自動更新方法。首先,本文采用歐拉-歐拉法對亞聲速蛇形進氣道進行了空氣-過冷水滴兩相流場的計算,分析了來流馬赫數(shù)0.3時結(jié)冰參數(shù)在進氣道中的沿程變化規(guī)律,獲得進氣道出口的流場分布特征。計算結(jié)果表明空氣和過冷水滴流經(jīng)蛇形進氣道后由于通道二次流的原因會在其出口的特定位置形成液態(tài)水含量較低的局部區(qū)域,同時該區(qū)域的水滴速度也低于周圍其它位置處的數(shù)值。其次,本文對Fluent的動網(wǎng)格功能進行二次開發(fā)以實現(xiàn)積冰數(shù)值模擬過程中由于冰層增長所需的網(wǎng)格的自動更新。以典型的渦噴發(fā)動機進口段支板表面積冰為算例進行網(wǎng)格的移動方法的測試,測試結(jié)果證明該方法在滿足壁面第一層網(wǎng)格一定垂直度的前提下能有效且快速地實現(xiàn)網(wǎng)格的自動更新。最后,本文提取進氣道出口的流場數(shù)據(jù)作為一種仿CFM56-C型大涵道比渦扇發(fā)動機進口的邊界條件并使用歐拉-歐拉法對其進口段進行空氣-過冷水滴亮相流場的數(shù)值計算。之后基于流場的計算結(jié)果采用冰的生長和水膜流動耦合求解的三維積冰數(shù)值模擬方法對該發(fā)動機進口段的支板和整流帽罩進行積冰計算,獲得迎風表面的水滴撞擊特性、不同時刻的冰形或者結(jié)冰的分布情況。計算結(jié)果表明:同一時刻與進氣道對稱面垂直的支板表面積冰量最大,其下表面及前緣位置為主要的結(jié)冰區(qū)域,其它支板的積冰量都相對較小。整流帽罩的下表面靠近圓錐頂點的位置為主要的結(jié)冰區(qū)域,帽罩的后緣及上表面的絕大部分區(qū)域均未發(fā)生結(jié)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.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：V231

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