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畢業(yè)設(shè)計(jì)-同軸送粉器數(shù)值模擬-wenkub.com

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【正文】 70176。 subscripts i and j are just subscripts for the velocity ponents and the space coordinates. According to Launder’s remended numerical value and the experimental validation, where σk=, s 1:3, C1=, C2= , Cu= 0:09. Discrete phase track putation equation In FLUENT software, the track of a dispersed phase particle is solved by the force balance on the particle in a Lagrangian reference frame (following the particle coordination). The force balance equates the particle inertia with the force acting on the particle, and can be written as Where u is the pressive gas velocity, up is the particle’s velocity, gx is the acceleration of gravity at x direction. FD is the drag force per mass for powder, ρP is the density of powder, Fx is other forces in the calculation process. In Eq. 3, it loses sight of thermal force (when considering heat transfer), Brown force (to deal with the particle of inferior microcosmic size), Saffman force (to deal with the particle of inferior microcosmic size), the inertia (the additional quality force is caused by the flow field around the particles accelerating) and the gravity [8]. 3 Numerical putation of flow field in and out of the nozzle Discrete model and grid selections The multiphase behavior of the discrete model is simulated by FLUENT. Particle phase will be treated as discrete phase if its volume percentage of granule phase is less than 10%. 沈陽理工大學(xué)學(xué)士學(xué) 位論文 39 Otherwise, the particle phase will be treated as fluid. In this discrete model, the gas track, the velocity and concentration field in and out of the powder field are puted. According to focus principle and columniform putation area of the nozzle, a 2D axisymmetric model is built up, of which the putation area size is 25 mm55 mm, the inner cone angle is α and the outer cone angle is β. The putation area of the nozzle is shown in Fig. 2. As different structure of the nozzle can result in different concentration field of the powder, the distribution of powder’s concentration is studied corresponding to different cone ring gap (H=1 mm, mm, 2 mm) and different inner and outer cone angle(α, β= 45176。 σk and σs are respectively the turbulent Prandtl number of turbulent kiic energy k and ε dissipation rate。 (4) collision between particles is not considered, and particle pressure and viscosity are ignored. Gas phase turbulence control equation In the discrete phase model, pressed gas is regarded as ideal gas, and the basic turbulence control equation includes continuity equation and momentum equation if the thermal effect on particles by laser is neglected [16]. The standard turbulence k–ε model is adopted, which was put forward by Launder and Spalding [17], in which k and ε equation are as below respectively. 沈陽理工大學(xué)學(xué)士學(xué) 位論文 38 Where μt is the turbulence viscosity。 Bingheng Lu Received: 23 October 2021 / Accepted: 5 April 2021 / Published online: 25 April 2021 SpringerVerlag London Limited 2021 Abstract In the laser metal direct manufacturing, gas–solid twophase flow theory is adopted to simulate the flow field of powders in coaxial nozzle to fabricate plex parts of pact structure. The separate model in FLUENT is used to evaluate the concentration distribution rule and the focusing characteristics of the powder flow field. The results indicate that the focal concentrations of the coaxial powder nozzle in radial direction and axial direction are approximately obeyed by the Gaussian distribution. When the cone angle of coaxial nozzle is invariable, the cone ring gap is smaller, the focal point concentration in the powder flow field is bigger。 最后,向在百忙中抽出時(shí)間對(duì)本文進(jìn)行評(píng)審并提出寶貴意見的各位專家表示衷心地感謝! 新的生活即將開始,前進(jìn)的號(hào)角已經(jīng)吹響,我會(huì)繼續(xù)努力地學(xué)習(xí),生活和工作,以期用自己的微薄之力來回報(bào)母校的培育之情,并為社會(huì)的進(jìn)步做出新的貢獻(xiàn)! 參考文獻(xiàn) ,胡國清 ,劉文艷 ,林忠華 .快速原型研究綜述 [J].廈門大學(xué)機(jī)電系 .2021 ,巨麗 ,杜詩文 .快速原型制造技術(shù)與進(jìn)展 [J].太原重型機(jī)械學(xué)院學(xué)報(bào) ,2021:255258 .快速成型 先進(jìn)的 現(xiàn)代制造技術(shù) [J].《鑄造技術(shù)》 .1999,4:3739 4. 王秀峰等 . 快速原型制造技術(shù) .中國輕工業(yè)出版社, 2021 5. 胡曉冬等 . 金屬直接成型技術(shù)的發(fā)展與展望 .工具技術(shù), 2021( 10): 36 沈陽理工大學(xué)學(xué)士學(xué) 位論文 34 6. 王從軍等 . SLS 成型件的精度分析 [J]. 華中科技大學(xué)學(xué)報(bào), 2021( 6): 7779 附 錄 英文文獻(xiàn) Numerical simulation of powder flow field on coaxial powder 沈陽理工大學(xué)學(xué)士學(xué) 位論文 35 nozzle in laser metal direct manufacturing Anfeng Zhang amp。 沈陽理工大學(xué)學(xué)士學(xué) 位論文 32 致 謝 本論文是在徐麗導(dǎo)師的親切關(guān)懷和悉心指導(dǎo)下而完成的。 時(shí),粉末匯聚的體積百分?jǐn)?shù) 圖 75176。 時(shí),粉末匯聚的體積百分?jǐn)?shù) 圖 65176。 ,粉末的匯聚性能模擬結(jié)果見圖 。 選取氣腔進(jìn)口速度為 ,粉腔的錐角角度分別為 60176。 、進(jìn)口速度為 2m/s,氣腔的錐角角度為 90176。 圖 錐角相同而改變氣腔進(jìn)口速度為 5m/s時(shí),粉末匯聚的體積百分?jǐn)?shù) 沈陽理工大學(xué)學(xué)士學(xué) 位論文 22 圖 5m/s時(shí),粉末匯聚的速度矢量圖 圖 ,粉末匯聚的體積百分?jǐn)?shù) 沈陽理工大學(xué)學(xué)士學(xué) 位論文 23 圖 ,粉末匯聚的速度矢量圖 圖 10m/s時(shí),粉末匯聚的體積百分?jǐn)?shù) 沈陽理工大學(xué)學(xué)士學(xué) 位論文 24 圖 10m/s時(shí),粉末匯聚的速度矢量圖 圖 90%左右,圖 百分?jǐn)?shù)在 95%~100%之間,圖 70%~80%之間。 時(shí),粉末的匯聚性能較好。 時(shí),粉末匯聚的體積百分?jǐn)?shù) 沈陽理工大學(xué)學(xué)士學(xué) 位論文 21 圖 氣腔和粉腔錐角角度均為 75176。 時(shí),粉末匯聚的體積百分?jǐn)?shù) 沈陽理工大學(xué)學(xué)士學(xué) 位論文 19 圖 氣腔和粉腔錐角角度均為 65176。 ,粉腔的進(jìn)口速度為 2m/s,氣腔的進(jìn)口速度為 ,結(jié)果見圖 至 。 粉氣同角時(shí)匯聚特性數(shù)值模擬 兩腔錐角變化對(duì)匯聚性能影響 以下是兩腔的錐角角度同為 60176。 沈陽理工大學(xué)學(xué)士學(xué) 位論文 17 5.匯聚過程的計(jì)算結(jié)果與分析 根據(jù)同軸送粉匯聚過程的分析可知,影響同軸送粉匯聚性能和匯聚焦距的因素有很多,主要有粉腔間隙、粉腔錐角、氣腔錐角和氣腔進(jìn)口速度等。 、 65176。 粉氣非同角時(shí)匯聚特性數(shù)值模擬 氣腔進(jìn)口速度對(duì)匯聚性能影響,選取粉 腔的錐角角度為 60176。 、 70176。 然后通過 GEOMETRY FACE 將矩形分裂成兩部分 再在矩形上做( 5,25),( 5,25), ( ,25),( ,25),( ,25),( ,25),( ,25),( ,25) 八個(gè)分裂點(diǎn),以此做出四個(gè)噴口,模型建立完成。對(duì)于不同的流動(dòng)領(lǐng)域和模型, FLUENT 軟件甚至還提供了其他幾種解算器,其中包括NEKTON、 FIDAP、幾何模型。 ( 10)用一維模型計(jì)算風(fēng)扇和換熱器的性能。 ( 6)化學(xué)組元混合與反應(yīng)計(jì)算,包括燃燒模型和表面凝結(jié)反應(yīng)模型。 ( 2)熱傳導(dǎo)和對(duì)流傳熱相耦合的傳熱計(jì)算。 ( 3)定常、非定常流。 ( 4) TFRID—— FLUENT用于從表面網(wǎng)格生成空間網(wǎng)格的軟件。而 LISP 類型的語言允許高級(jí)用戶通過編制自定義函數(shù)改變軟件的外觀,使用戶在使用中可以根據(jù)自己的喜好定沈陽理工大學(xué)學(xué)士學(xué) 位論文 12 制界面,這點(diǎn)是 FLUENT 軟件的一個(gè)顯著特色。除了 GAMBIT之外,可以生成FLUENT網(wǎng)格的網(wǎng)格軟件還有 ICEMCFD、 GridGen等等。與結(jié)構(gòu)化網(wǎng)格和分塊結(jié)構(gòu)網(wǎng)格相比,非結(jié)構(gòu)網(wǎng)格劃分便于處理復(fù)雜外形的網(wǎng)格劃分,而適應(yīng)性網(wǎng)格則便于
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