本文關(guān)鍵詞： 長水口 中間包 湍流控制 數(shù)值模擬 潔凈度　出處：《北京科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：本文采用數(shù)值模擬、物理模擬和工業(yè)實(shí)驗(yàn)相結(jié)合的方法研究了不同鋼包長水口對中間包內(nèi)的湍流控制機(jī)理以及對鋼液潔凈度的影響,從而探索了采用鋼包長水口用于中間包流動(dòng)控制的理論基礎(chǔ)和工業(yè)可行性。首先,針對目前比較流行的幾種模擬水口和中間包流動(dòng)的數(shù)學(xué)模型進(jìn)行了評估,包括標(biāo)準(zhǔn)k-ε數(shù)學(xué)模型、雷諾應(yīng)力模型和大渦模擬模型。結(jié)果表明,通過合理安排結(jié)構(gòu)網(wǎng)格的設(shè)計(jì)和計(jì)算方法,大渦模擬模型能夠較好地捕捉水口和中間包內(nèi)的瞬態(tài)湍流結(jié)構(gòu),能夠獲得較小尺度的湍流脈動(dòng)信息,有利于湍流結(jié)構(gòu)的深入研究和探討。同時(shí),通過建立物理模型對大渦模擬的計(jì)算結(jié)果進(jìn)行了對比驗(yàn)證,兩者的速度場匹配度較好。論文采用大渦模擬對目前已經(jīng)工業(yè)化的傳統(tǒng)型和喇叭型鋼包長水口模型的內(nèi)部湍流結(jié)構(gòu)進(jìn)行了對比研究。為了便于對比驗(yàn)證,水口模型為1/3比例的水模型。研究結(jié)果表明,喇叭型水口的擴(kuò)張段一方面促進(jìn)了水口內(nèi)渦流的產(chǎn)生和湍動(dòng)能的耗散,另一方面增加了水口內(nèi)有效流動(dòng)容積和出口面積。這使得喇叭型水口的出口速度較小,主流股不是直流向下而是呈搖擺形向下流動(dòng)。長水口的出口流股特征影響著中間包內(nèi)的鋼液流動(dòng)。傳統(tǒng)型直筒水口的出口流股速度較大,對中間包底部沖擊相對較大,中包表面流速也相對較大。喇叭型水口的出口流股速度較小,搖擺形的流股能與更多體積的中間包流體進(jìn)行混勻,湍動(dòng)能得到進(jìn)一步耗散,從而緩和了對中包底部的沖擊,獲得了相對平緩的表面流速。同時(shí),物理模擬驗(yàn)證了數(shù)值模擬關(guān)于喇叭型水口的作用,在鋼包開澆時(shí)渣層裸露面積較小,在穩(wěn)定澆注時(shí)液面也更加平穩(wěn)。這部分模擬結(jié)果揭示了喇叭型水口在提高連鑄運(yùn)作效率和改善鋼液潔凈度方面的作用機(jī)理。然后,論文將大渦模擬的應(yīng)用擴(kuò)展到了實(shí)際鋼包長水口和中間包內(nèi),探討了典型喇叭型鋼包長水口內(nèi)的鋼液流動(dòng)的三段式湍流結(jié)構(gòu)。研究發(fā)現(xiàn),喇叭段長度H與出口直徑D的比例對水口內(nèi)流動(dòng)特征影響較大。為了獲得發(fā)展更為充分的水口湍流運(yùn)動(dòng)和避免出口回流的產(chǎn)生,兩者比例的建議值為H/D≥4,該值適用于市場上的兩類喇叭型鋼包長水口。工藝參數(shù)也影響著水口內(nèi)的湍流運(yùn)動(dòng)。當(dāng)滑動(dòng)水口的開口面積為一半時(shí),在水口入口主流股的兩側(cè)形成了不同尺度的漩渦。主流股的運(yùn)動(dòng)軌跡呈曲率較小的弧形曲線,最終在偏向滑動(dòng)水口開口側(cè)的出口處流出,造成了出口流股的不對稱性。為了進(jìn)一步研究兩類工業(yè)化長水口的不同冶金效果,文章進(jìn)行了工業(yè)化實(shí)驗(yàn)研究。工業(yè)實(shí)驗(yàn)首先對比研究了喇叭型水口和傳統(tǒng)型水口開澆、鋼包下降和穩(wěn)態(tài)澆注時(shí)的中包內(nèi)的鋼液飛濺、冒煙和鋼液裸露的現(xiàn)象。結(jié)果表明,在非穩(wěn)態(tài)澆注時(shí),喇叭型水口能緩解鋼液飛濺;在穩(wěn)態(tài)澆注時(shí),能獲得更為平靜的中包液面,這體現(xiàn)了該水口在改善現(xiàn)場操作和鋼液潔凈度方面的潛在作用。通過在開澆前、開澆完成時(shí)(3 min)和穩(wěn)態(tài)澆注時(shí)取樣分析,[Al]、[N]和T.O.檢測結(jié)果表明,使用喇叭型水口時(shí),T.O.和[N]含量相比傳統(tǒng)型水口的都較低,相對傳統(tǒng)型水口分別降低7.8%和8.3%。喇叭型水口對于減少[Al]損失的貢獻(xiàn)值為21 ppm,相比傳統(tǒng)型水口的提高幅度為6.1%。同時(shí),文章也對比了長水口和其他控流裝置的潔凈化鋼液的效果,結(jié)果表明,考慮到鋼包長水口簡單的結(jié)構(gòu)設(shè)計(jì)和易操作性,鋼包長水口是一個(gè)具有市場競爭力的中間包控流裝置。最后,文章探索了一種新型的具有三個(gè)擴(kuò)張段的耗散型鋼包長水口內(nèi)的湍流控制機(jī)制和應(yīng)用的可能性。三個(gè)擴(kuò)張段的作用主要在于促使水口內(nèi)的湍流自耗散,模擬結(jié)果表明水口內(nèi)最大渦量值和應(yīng)變率明顯增加,促進(jìn)了水口內(nèi)的湍動(dòng)能耗散。配合喇叭型的出口段,耗散型水口的出口流股速度明顯減低,且擺動(dòng)較為劇烈。這些出口流股特征促進(jìn)了中包內(nèi)活塞區(qū)的增加,改善了中包內(nèi)的整體混勻情況。然而,耗散型水口目前只停留在一個(gè)理念探索的階段,仍然存在加工制作和實(shí)際應(yīng)用方面的問題。
[Abstract]:This paper uses the numerical simulation method, physical simulation and industrial experiment on the combination of different ladle nozzle of tundish turbulence control mechanism and the effect on steel cleanliness of liquid, which is used to explore the ladle nozzle for tundish flow control theory and industrial feasibility. Firstly, according to several popular the nozzle and the tundish flow mathematical model simulation was evaluated, including the standard k- turbulence model, Reynolds stress model and large eddy simulation model. The results show that the design and calculation method of reasonable arrangement structure of the grid, the large eddy simulation model can better capture the nozzle and the tundish transient turbulence structure, turbulent fluctuation information can be obtained in smaller scale, is conducive to the in-depth study and Discussion on the turbulence structure. At the same time, through the establishment of physical model for the calculation of large eddy simulation results were Contrast testing, both the velocity matching degree is better. The large eddy simulation of turbulent current internal structure of the traditional type has been industrialized and horn type ladle nozzle model was studied. In order to facilitate the comparison and validation of water model nozzle model for 1/3 ratio. The results show that a horn shaped nozzle divergent section the promotion of the dissipative nozzle vortex and turbulent kinetic energy, on the other hand, the increase in the effective flow volume and nozzle exit area. This makes the horn shaped nozzle exit velocity is small, but is not the main stream of DC downward swing shaped flow down. Long nozzle outlet stream characteristics influence the flow of molten steel in tundish in the traditional straight nozzle outlet stream velocity is larger, the tundish bottom impact is relatively large, the package surface velocity is relatively large. Horn type nozzle outlet stream speed Small swing shaped stream to middle and more volume package fluid mixing, turbulent kinetic energy dissipation further, thus easing the impact on the bottom of the package, the surface velocity is relatively flat. At the same time, the physical simulation results validate the numerical simulation on horn type nozzle, in the ladle during casting slag layer exposed area is small, stable in pouring liquid is more stable. The simulation results reveal the horn type nozzle in the mechanism to improve the operation efficiency of continuous casting and improving the cleanliness of liquid steel. Then, the paper will expand the application of large eddy simulation to actual ladle nozzle and tundish, discusses three a turbulent structure of molten steel flow typical horn type ladle nozzle. The study found that the horn length H and D ratio of nozzle exit diameter flow characteristics have a great effect. In order to obtain more sufficient water development The turbulent motion and avoid the export return, both the proportion of the recommended value of H/D = 4, the value for the market of two kinds of horn type ladle nozzle. The process parameters also affect the turbulence in the nozzle opening area. When the sliding gate is half, on both sides of the nozzle entrance formed the mainstream shares the different scale vortex. Trajectory of mainstream shares is a curve of curvature smaller, the final exit in the biased sliding gate opening side of the outflow, causing the asymmetry of the outlet stream. In order to further study on two kinds of different metallurgical industrial long nozzle, the experimental research on industrialization. After comparing the industrial experiment horn type nozzle and the traditional nozzle casting, ladle pouring down and steady in the molten steel in the splash, smoke and liquid steel exposed phenomenon. The results show that in the non steady state casting, horn type The nozzle can relieve the splash of liquid steel; in steady casting, tundish can obtain more calm, which reflects the gap in improving on-site operation and cleanliness of molten steel and the potential role. Through the pouring, pouring is completed (3 min) and steady state casting samples, [Al] [N] and T.O., the detection results show that the use of horn type nozzle, T.O. and [N] were compared with the traditional type of nozzle are low, compared to the traditional type of nozzle were decreased by 7.8% and 8.3%. type nozzle to reduce the loss of [Al] horn's contribution value was 21 ppm, the traditional type of nozzle increases compared to 6.1%. at the same time, the article also comparison of liquid steel purification effect, long nozzle and other flow control device for cleaning. The results show that considering the structure design of ladle nozzle has the advantages of simple and easy operation, ladle nozzle is an intermediate competitive market with the flow control devices. Finally, the paper explores a The possibility of turbulence model has three expansion section of the dissipative type ladle nozzle inside control mechanism and application. The three section is mainly to promote the expansion of the turbulence in the nozzle from dissipation, the simulation results show that the maximum vorticity value within the nozzle and the strain rate increased significantly, promote the turbulent kinetic energy dissipation in the nozzle. With the exit section of horn, dissipative type nozzle outlet stream velocity decreased, and swing violently. These characteristics of outlet stream has increased in the bag piston area, improve the whole package mix. However, dissipative type nozzle is only explored in a concept stage still, manufacture and application problems.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TF777

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本文編號(hào)：1473852