钢包长水口应用于中间包湍流控制的基础研究与实践

发布时间：2018-01-29 16:37

本文关键词： 长水口中间包湍流控制数值模拟洁净度　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：本文采用数值模拟、物理模拟和工业实验相结合的方法研究了不同钢包长水口对中间包内的湍流控制机理以及对钢液洁净度的影响,从而探索了采用钢包长水口用于中间包流动控制的理论基础和工业可行性。首先,针对目前比较流行的几种模拟水口和中间包流动的数学模型进行了评估,包括标准k-ε数学模型、雷诺应力模型和大涡模拟模型。结果表明,通过合理安排结构网格的设计和计算方法,大涡模拟模型能够较好地捕捉水口和中间包内的瞬态湍流结构,能够获得较小尺度的湍流脉动信息,有利于湍流结构的深入研究和探讨。同时,通过建立物理模型对大涡模拟的计算结果进行了对比验证,两者的速度场匹配度较好。论文采用大涡模拟对目前已经工业化的传统型和喇叭型钢包长水口模型的内部湍流结构进行了对比研究。为了便于对比验证,水口模型为1/3比例的水模型。研究结果表明,喇叭型水口的扩张段一方面促进了水口内涡流的产生和湍动能的耗散,另一方面增加了水口内有效流动容积和出口面积。这使得喇叭型水口的出口速度较小,主流股不是直流向下而是呈摇摆形向下流动。长水口的出口流股特征影响着中间包内的钢液流动。传统型直筒水口的出口流股速度较大,对中间包底部冲击相对较大,中包表面流速也相对较大。喇叭型水口的出口流股速度较小,摇摆形的流股能与更多体积的中间包流体进行混匀,湍动能得到进一步耗散,从而缓和了对中包底部的冲击,获得了相对平缓的表面流速。同时,物理模拟验证了数值模拟关于喇叭型水口的作用,在钢包开浇时渣层裸露面积较小,在稳定浇注时液面也更加平稳。这部分模拟结果揭示了喇叭型水口在提高连铸运作效率和改善钢液洁净度方面的作用机理。然后,论文将大涡模拟的应用扩展到了实际钢包长水口和中间包内,探讨了典型喇叭型钢包长水口内的钢液流动的三段式湍流结构。研究发现,喇叭段长度H与出口直径D的比例对水口内流动特征影响较大。为了获得发展更为充分的水口湍流运动和避免出口回流的产生,两者比例的建议值为H/D≥4,该值适用于市场上的两类喇叭型钢包长水口。工艺参数也影响着水口内的湍流运动。当滑动水口的开口面积为一半时,在水口入口主流股的两侧形成了不同尺度的漩涡。主流股的运动轨迹呈曲率较小的弧形曲线,最终在偏向滑动水口开口侧的出口处流出,造成了出口流股的不对称性。为了进一步研究两类工业化长水口的不同冶金效果,文章进行了工业化实验研究。工业实验首先对比研究了喇叭型水口和传统型水口开浇、钢包下降和稳态浇注时的中包内的钢液飞溅、冒烟和钢液裸露的现象。结果表明,在非稳态浇注时,喇叭型水口能缓解钢液飞溅;在稳态浇注时,能获得更为平静的中包液面,这体现了该水口在改善现场操作和钢液洁净度方面的潜在作用。通过在开浇前、开浇完成时(3 min)和稳态浇注时取样分析,[Al]、[N]和T.O.检测结果表明,使用喇叭型水口时,T.O.和[N]含量相比传统型水口的都较低,相对传统型水口分别降低7.8%和8.3%。喇叭型水口对于减少[Al]损失的贡献值为21 ppm,相比传统型水口的提高幅度为6.1%。同时,文章也对比了长水口和其他控流装置的洁净化钢液的效果,结果表明,考虑到钢包长水口简单的结构设计和易操作性,钢包长水口是一个具有市场竞争力的中间包控流装置。最后,文章探索了一种新型的具有三个扩张段的耗散型钢包长水口内的湍流控制机制和应用的可能性。三个扩张段的作用主要在于促使水口内的湍流自耗散,模拟结果表明水口内最大涡量值和应变率明显增加,促进了水口内的湍动能耗散。配合喇叭型的出口段,耗散型水口的出口流股速度明显减低,且摆动较为剧烈。这些出口流股特征促进了中包内活塞区的增加,改善了中包内的整体混匀情况。然而,耗散型水口目前只停留在一个理念探索的阶段,仍然存在加工制作和实际应用方面的问题。
[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.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF777

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