發(fā)布時間：2018-12-17 18:21

【摘要】：航天飛機和X-37B等長時間再入式高超聲速飛行器在飛行過程中需要克服嚴重的氣動加熱,為容納由此引起的結(jié)構(gòu)間熱膨脹,防熱瓦之間必須預(yù)留一定的縫隙。另外,為了能夠順利完成變舵偏、部件彈出等飛行動作,縫隙的存在同樣不可避免�？p隙的存在將導致飛行器表面局部流場結(jié)構(gòu)及傳熱特性發(fā)生較大變化,縫隙入口處由于邊界層分離與再附將產(chǎn)生局部高熱流區(qū);在某些工況下縫隙入口處會產(chǎn)生激波;縫隙內(nèi)會卷起渦旋結(jié)構(gòu)等。渦旋結(jié)構(gòu)將大量熱量卷入縫隙中,使得對流傳熱明顯增強,加之縫隙極其狹小,輻射散熱效應(yīng)受阻,縫隙內(nèi)壁極易產(chǎn)生較高的壁溫,進而引起較為嚴重的局部燒蝕。因此,認識高超聲速飛行器縫隙內(nèi)的流場結(jié)構(gòu),研究來流參數(shù)、幾何參數(shù)等對縫內(nèi)渦旋結(jié)構(gòu)及壁面熱流分布的影響極為重要。世界各航天大國均對縫隙流動進行了研究,如美國在研制航天飛機時,曾投入了巨大的人力物力進行防熱瓦縫隙熱環(huán)境和熱結(jié)構(gòu)試驗。但受限于數(shù)值計算技術(shù)的發(fā)展,早期主要依靠地面試驗進行研究,成本較高,周期較長。本文針對這一問題,利用自主研發(fā)的CFD軟件,對高超聲速飛行器縫隙流動進行了較為精細的數(shù)值模擬研究。首先重點闡述了在縫隙流動機理分析、試驗測量以及數(shù)值模擬方面取得的成果及存在的不足。針對這些不足和縫隙流動的特點,在van Leer通量分裂的基礎(chǔ)上引入了焓守恒修正,很好地改善了van Leer通量分裂方法在邊界層、剪切層中耗散過大的問題,有效提高了縫隙中的流場分辨率。在此基礎(chǔ)之上分別從渦旋結(jié)構(gòu)和壁面熱流兩個方面對本文的計算方法進行了有效性驗證,并發(fā)現(xiàn)合理捕捉旋渦結(jié)構(gòu)對于縫隙壁面熱流的準確模擬具有重要意義。接著對縫隙流動機理進行了分析。針對平板模型上的無限長縫隙,從渦量的角度出發(fā),分析了縫隙內(nèi)渦旋結(jié)構(gòu)的形成、發(fā)展及耗散過程,并得出縫內(nèi)的黏性耗散作用對縫隙流動的研究至關(guān)重要。結(jié)合機理分析,研究了來流參數(shù)、幾何參數(shù)對縫隙流動的影響。給出了縫內(nèi)渦旋結(jié)構(gòu)及壁面熱流隨來流雷諾數(shù)、馬赫數(shù)、迎角、縫隙深寬比及縫隙倒圓半徑的變化規(guī)律,得出了縫內(nèi)主渦個數(shù)是否滿足與縫隙深寬比大致成正比的一個判別準則,其結(jié)論可為防熱設(shè)計提供參考。最后對全文的研究工作及得到的相關(guān)結(jié)論進行了歸納總結(jié),并對論文中存在的不足和下一步的研究方向進行了簡要闡述。
[Abstract]:The space shuttle and X-37B long-time reentry hypersonic vehicle need to overcome the severe aerodynamic heating in flight. In order to accommodate the thermal expansion between the structures caused by it, a certain gap must be reserved between the heat resistant tiles. In addition, the existence of cracks is also inevitable in order to successfully complete the variable rudder deviation and the ejection of components. The existence of the gap will lead to great changes in the structure of the local flow field and the heat transfer characteristics of the aircraft surface. The gap entrance will produce a local high heat flux region due to the separation and reattachment of the boundary layer, and a shock wave will occur at the gap entrance under some working conditions. The vortex structure will be rolled up in the crevice. The vortex structure involves a large amount of heat in the gap, which makes the convection heat transfer obviously enhanced, and the gap is extremely narrow, the radiation heat dissipation effect is blocked, and the inner wall of the gap easily produces higher wall temperature, which leads to serious local ablation. Therefore, it is very important to understand the structure of flow field in the slot of hypersonic vehicle, and to study the influence of the parameters of incoming flow and geometry on the vortex structure and the heat flux distribution on the wall. The gap flow has been studied in all the major spaceflight countries in the world. For example, the United States has invested huge manpower and material resources to test the thermal environment and thermal structure of the slot in the space shuttle. However, limited by the development of numerical calculation technology, the early research mainly depends on the ground test, which has high cost and long period. In order to solve this problem, a detailed numerical simulation of slot flow in hypersonic vehicle is carried out by using CFD software developed by ourselves. Firstly, the achievements and shortcomings in the analysis of slot flow mechanism, experimental measurement and numerical simulation are described. In view of these shortcomings and the characteristics of slot flow, the enthalpy conservation correction is introduced on the basis of van Leer flux splitting, which improves the problem of excessive dissipation of van Leer flux splitting method in the boundary layer and shear layer. The flow field resolution in the slot is improved effectively. On this basis, the validity of the method is verified from the vortex structure and the wall heat flux, and it is found that the reasonable capture of the vortex structure is of great significance for the accurate simulation of the gap wall heat flux. Then the mechanism of slot flow is analyzed. In this paper, the formation, development and dissipation process of vortex structure in the plate model are analyzed from the point of view of vorticity, and it is concluded that the viscous dissipation in the slot is very important to the study of slot flow. Based on the mechanism analysis, the effects of flow parameters and geometric parameters on slot flow are studied. The variation of vortex structure and wall heat flow with Reynolds number, Mach number, angle of attack, slit depth to width ratio and the radius of the reverse circle of the slot are given. A criterion for determining whether the number of main vortices in a slot is in direct proportion to the ratio of slit depth to width is obtained. The conclusion can be used as a reference for the design of heat protection. Finally, the research work and related conclusions are summarized, and the shortcomings of the paper and the next research direction are briefly described.
【學位授予單位】：中國空氣動力研究與發(fā)展中心
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：V445.1;V416

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