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Effects of argon blowing at tundish upper nozzle on multiphase flow behavior in nozzle

Journal of Iron and Steel Research(International) 2022年第4期29卷 588-600页

作者： Xu-feng Qin Chang-gui Cheng Yang Li Wei-li Wu Yan Jin The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan 430081HubeiChina

In continuous casting,the argon blowing at the tundish upper nozzle is usually used to prevent nozzle clogging,whose effect is closely related to the migration of argon bubbles and the flow behavior of the liquid steel in the nozzle.Here,to investigate the effects of argon blowing at the tundish upper nozzle on multiphase flow behavior in nozzle,a threedimensional model of the tundish–nozzle–mold was established for numerical simulation.The results indicate that the argon bubbles injected from the inner wall of the tundish upper nozzle first move downward along the nozzle wall under the action of the liquid steel.As the distance from the tundish upper nozzle increases,the argon bubbles gradually diffuse to the center of the nozzle.Compared with no argon blowing,the liquid steel velocity increases in the center of the nozzle and decreases near the wall with argon blowing.With increasing the argon flow rate,the concentration of bubbles in the nozzle increases,and the process of bubble group diffusion to the center region of the nozzle speeds up.This in turn increases the liquid steel velocity at the center of the nozzle but reduces near the wall.With increasing the casting speed,the concentration of bubbles in the nozzle decreases,the length of the bubble group near the nozzle wall is extended,and the liquid steel velocity at the center region and near-wall region of the nozzle increases.The mechanism of argon blowing at the tundish upper nozzle to prevent nozzle clogging is mainly realized by the isolation effect of the argon bubble group on the inner wall of the nozzle.

关键词： Argon blowing Tundish upper nozzle nozzle clogging Numerical simulation

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Relationships and Mechanisms of Sand Grain Promotion on nozzle Cavitation Flow Evolution: A Numerical Simulation Investigation

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Journal of Thermal Science 2022年第6期31卷 2385-2410页

作者： HAN Xiangdong XIAO Jingping YU Fangyan ZHAO Weiguo Aerospace Technology Institute China Aerodynamics Research and Development CenterMianyang 621000China School of Civil Engineering Nanchang Institute of TechnologyNanchang 330044China College of Energy and Power Engineering Lanzhou University of TechnologyLanzhou 730050China

The objective of this study was to primarily investigate the effects of sand grains with different mean diameters and concentrations on cavitation flow development in a nozzle. One new solid-liquid-vapor three-phase coupling numerical method was presented and a cavitation model was changed to perform numerical simulations. Results indicated that sand grain-pure water-cavitation flow(SG-PW-CF) vapor contents were greater than in pure water-cavitation flow(PW-CF). Sand grains were found to promote cavitation flow development, with the concentration promotion range becoming smaller with increased mean diameter. The mechanisms for these effects were explored and revealed as well. In SG-PW-CF, cavitation nuclei number was greater and tensile stress was also greater than in PW-CF. The maximum and absolute minimum slip velocities and maximum and minimum turbulent kinetic energies of SG-PW-CF were greater than in PW-CF. These effects on SG-PW-CF evolution were large, involving primary factors. The calculated magnitude of the Saffman lift force in SG-PW-CF was small(10^(-2)), with its effects relatively weak and it was thus a secondary factor. Effects of variations of flow fields were more significant than force changes. In SG-PW-CF, variations of a single parameter with the concentration could not reflect the alternating relationships of vapor content with the concentration. Indeed, it was a combination of variations of all parameters.

关键词： nozzle cavitation sand grain mean diameter sand grain concentration numerical simulation

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Optimization of a Diesel Injector nozzle

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Fluid Dynamics & Materials Processing 2023年第11期19卷 2933-2951页

作者： Yaofei Zhang Guoxiang Li Shuzhan Bai Ke Sun Guihua Wang Yujie Jia Zhengxian Fang School of Energy and Power Engineering Shandong UniversityJinan250061China Longkou Longbeng Diesel Injection High Technology Equipment Co. Ltd.Longkou265018China

Multiphase simulations based on the VOF(Volume of Fluid)approach,used in synergy with the cavitation Schnerr-Sauer method and the K-Epsilon turbulence model,have been conducted to study the behavior of an injector nozzle as a function of relevant structural parameters(such as the spray hole diameter and length).The related performances have been optimized in the framework of orthogonal experimental design and range analysis methods.As made evident by the results,as the spray hole diameter increases from 0.10 to 0.20 mm,the outlet massflow rate grows by 243.23%.A small diameter of the spray hole,however,has a beneficial effect in terms of cavitation suppression.Moreover,rounding the spray hole can effectively increase the outlet massflow rate and improve theflow characteristics while mitigating the cavitation phenomenon inside the spray hole.In particular,with the optimized nozzle design,the outlet massflow rate can be increased by 13.33%,while the fuel vapor volume is reduced by 33.53%,thereby,leading to significant improvements in terms offlow characteristics and cavitation control.

关键词： nozzle numerical simulation structural parameter cavitation

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nozzle Optimization for Water Jet Propulsion with A Positive Displacement Pump

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China Ocean Engineering 2014年第3期28卷 409-419页

作者：杨友胜谢迎春聂松林 College of Engineering Ocean University of China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology

In the water jet propulsion system with a positive displacement （PD） pump, the nozzle, which converts pressure energy into kinetic energy, is one of the key parts exerting great influence on the reactive thrust and the efficiency of the system due to its high working pressure and easily occurring cavitation characteristics. Based on the previous studies of the energy loss and the pressure distribution of different nozzles, a model of water jet reactive thrust, which fully takes the energy loss and the nozzle parameters into consideration, is developed to optimize the nozzle design. Experiments and simulations are carried out to investigate the reactive thrust and the conversion efficiency of cylindrical nozzles, conical nozzles and optimized nozzles. The results show that the optimized nozzles have the largest reactive thrust and the highest energy conversion efficiency under the same inlet conditions. The related methods and conclusions are extended to the study of other applications of the water jet, such as water jet cutting, water mist fire suppression, water injection molding.

关键词： energy loss nozzle PD pump reactive thrust waterjet propulsion

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Robust design and analysis of a conformal expansion nozzle with inverse-design idea

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Chinese Journal of Aeronautics 2018年第1期31卷 79-88页

作者： Wenbiao GAN Xiaocui ZHANG Tielin MA Qinling ZHANG Wu YUAN Research Institute of Unmanned System Beihang University The First Aircraft Institute Aviation Industry Corporation of China Computer Network Information Center Chinese Academy of Sciences

This paper examines robust optimization design and analysis of a conformal expansion nozzle of flying wing Unmanned Aerial Vehicle （UAV） with the inverse-design idea. In view of flow features and stealth constraints, the inverse-design idea is described and the uncertainty-based robust design model is presented. A robust design system employs this model to combine deterministic optimization and robust optimization and is applied into design of a conformal expansion nozzle. The results indicate that design optimization can conform to the anticipation of the inversedesign idea and significantly improve the aerodynamic performance that meet the requirement of 6σ. The present method is a feasible nozzle design strategy that integrates robust optimization and inverse-design.

关键词： Aerodynamic analysis Inverse-design nozzle Off-design Robust optimization

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Numerical simulation of A1203 deposition at a nozzle during continuous casting

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Journal of University of Science and Technology Beijing 2008年第3期15卷 227-235页

作者： Fangming Yuan Xinghua Wang Jiongming Zhang Li Zhang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Metallurgical Equipment Company of China （MECC） Sinosteel Corporation Beijing 100080 China Baosteel Advanced Technology Institute Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China

The effects of various factors, such as argon flow rate and slide gate opening ratio, on the alumina deposition rate were researched by the numerical simulation method. The pressure in the nozzle is significantly affected by argon flow rate and slide gate opening ratio. To keep positive pressure in the nozzle, the argon flow rate should be increased with a decrease in slide gate opening ratio. The effect of argon flow rate on the alumina deposition rate depends on the condition of opening ratio or casting speed. The effect of increasing the argon flow rate on the deposition rate is not obvious when the opening ratio is small. The A1203 deposition rate decreases significantly with an increase in argon flow rate when the argon flow rate is low, but it decreases slowly when the argon flow rate reaches a certain value. The alumina deposition rate is linear with alumina content at different slide gate opening ratios and argon flow rates. The observed thickness of the deposition layer at the bottom and outlet of a real clogged nozzle is almost equal to the result of the numerical simulation.

关键词： continuous casting nozzle clogging numerical simulation

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Acoustic measurements of models of military style supersonic nozzle jets

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Chinese Journal of Aeronautics 2014年第1期27卷 23-33页

作者： Ching-Wen Kuo Jérémy Veltin Dennis K.McLaughlin Department of Aerospace Engineering The Pennsylvania State UniversityUniversity Park TNO Science and Industry

Modern military aircraft jet engines are designed with variable-geometry nozzles to provide optimal thrust in different operating conditions, depending on the flight envelope. How- ever, acoustic measurements for such nozzles are scarce, due to the cost involved in making full- scale measurements and the lack of details about the exact geometries of these nozzles. Thus the present effort at Pennsylvania State University （PSU） in partnership with GE Aviation and the NASA Glenn Research Center is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles, and to identify and test promising noise reduction techniques. An equally important objective is to develop methodology for using data obtained from small- and moderate-scale experiments to reliably predict the full-scale engine noise. The experimental results presented show reasonable agreement between small-scale and medium-scale jets, as well as between heated jets and heat-simulated ones.

关键词： Aeroacoustics Acoustic noise measurement Jet noise Jets nozzle Supersonic flow

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Design and implementation of rigid-flexible coupling for a half-flexible single jack nozzle

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Chinese Journal of Aeronautics 2016年第6期29卷 1477-1483页

作者： Chen Pengfei Wu Feng Xu Jinglei Feng Xudong Yang Qiao Aviation Key Laboratory of Science and Technology on Aero-Engine Altitude Simulation China Gas Turbine Establishment Aviation Engine Corporation of China Department of Power Engineering Nanjing University of Aeronautics and Astronautics

The aerodynamic design of a rigid-flexible coupling profile is the decisive factor for the flow-field quality of a supersonic free jet wind tunnel nozzle, and its mechanic dynamic features are the key for engineering implementation of continuous Mach number regulations. To fulfill the requirements of a free jet inlet/engine compatibility test within a wide simulation envelop, both uniform flow-fields of continuous acceleration and deceleration are necessary. In this paper, the aerodynamic design methods of an expansion wall and machinery implementation plan for the halfflexible single jack nozzle were researched. The profile control in nozzle flexible plate design was studied with a rigid-flexible coupling method. Design and calculations were performed with the help of numerical simulation. The technique of axial free stretching of the flexible plate was used to improve the matching performance between the designed elasticity profile and the theoretical one, and the rigid-flexible coupling structure was calibrated by wind tunnel tests. Results indicate that the flexible plate aerodynamic design method used here is effective and feasible. Via rigidflexible coupling design, the flexible plate agrees with the rigid body very well, and continuous Mach number changes can be achieved during the tests. The nozzle's exit flow-field uniformity meets the requirements of China Military Standard(GJB).

关键词： Aerodynamic profile Flow-field quality Free jet nozzle Rigid-flexible coupling Variable Mach number Wind tunnel

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Influences of Geometric Parameters upon nozzle Performances in Scramjets

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Chinese Journal of Aeronautics 2008年第6期21卷 506-511页

作者： Li Jianping Song Wenyan Xing Ying Luo Feiteng School of Power and Energy Northwestern Polytechnical University Xi 'an 710072 China

This article investigates and presents the influences of geometric parameters of a scramjet exerting upon its nozzle performances. These parameters include divergent angles, total lengths, height ratios, cowl lengths, and cowl angles. The flow field within the scramjet nozzle is simulated numerically by using the CFD software--FLUENT in association with coupled implicit solver and an RNG k-ε turbulence model.

关键词： scramjet nozzle numerical simulation geometric parameters

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The measurement of internal surface characteristics of fuel nozzle orifices using the synchrotron X-ray micro CT technology

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Science China(Technological Sciences) 2018年第11期61卷 1621-1627页

作者： LI ZhiLong ZHAO WenBo WU ZhiJun GONG HuiFeng HU ZongJie DENG Jun LI LiGuang School of Automotive Studies Tongji University

The design of fuel nozzle orifices at micrometer scales is crucial for generating desired fuel spray patterns, and consequently optimizing fuel combustion and emission in internal combustion engines. Although there have been several recent advancements in the characterization of orifice internal geometries, quantitative studies on the orifice internal wall surface characteristics are still challeges due to the lack of effective measuring methods. A new method for quantifying the internal wall surface characteristics of fuel nozzle micro-orifices is presented in this study to achieve a better understanding and prediction of spray characteristics: Firstly, by using the synchrotron X-ray micro CT technology, a three-dimensional digital model of the fuel nozzle tip was constructed. Secondly, a data post-processing technique was then applied to unfold the orifice internal wall surface to a flat base plane. Finally, the conventional surface characteristic quantification techniques can be used to evaluate the wall surface characteristics. Two diesel nozzles with identical orifice geometry design but different hydraulic grinding time were measured using this method. One nozzle was hydro-ground for 2 s while the other was not. The internal wall surfaces of the two orifices were successfully unfolded to base planes and their surface characteristics were respectively analyzed. The surface fluctuation data were perfectly reproduced by a Gaussian distribution function. The standard deviations of the distribution demonstrate the fluctuation range and the distribution of the entire surface fluctuation profiles. As an effective parameter to evaluate the hydraulic grinding process and the spray behaviors, the standard deviation was considered feasible for the analysis of the orifice internal wall surface characteristics.

关键词： automotive fuel spray nozzle orifice wall surface characteristics synchrotron X-ray micro CT

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