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Effect of End Shape on flow and Heat Transfer characteristics of Two Parallel Plates

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Journal of Thermal Science 2024年第3期33卷 815-832页

作者： ZHANG Guang HONG Tianxiao WANG Dongrui XIN Jialin TAO Junyu LIN Zhe Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou310018China

flow around a pair of flat plates is a basic hydrodynamics problem.In this paper,the flow and heat transfer characteristics of two parallel plates with different edge shapes are numerically calculated.Under different inclined angles,the influence of chamfered and rounded structures with different sizes at the end-edge on unsteady flow and heat transfer characteristics of two parallel plates are analyzed.It is found that the instability and unsteadiness of flow decrease with the increase of end-edge size,and the non-uniformity of wake velocity of both rounded and chamfered plates decreases gradually.The non-uniformity of wake temperature increases firstly and then decreases at a small inclined angle,and the amplitude becomes the largest when S_(rou)(S_(cha))=3,while it basically keeps monotonically increasing at a large inclined angle.Moreover,the global heat transfer performance of the flat plate is obviously affected by the end-edge modification,especially the chamfered structure.With the increase of chamfered size,the global Nusselt number basically shows the decreasing trend.This study provides a theoretical basis for the application of plate-shape structure in engineering fields.

关键词： two parallel plates end shape flow characteristic heat transfer numerical simulation

Study on characteristics of a High-Precision Cold Gas Micro Thruster

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Engineering（科研） 2024年第1期16卷 38-45页

作者： Zhaoli Wang Changbin Guan Xudong Wang Weijie Zheng Longfei Su Advanced Space Propulsion Lab Beijing Institute of Control Engineering Beijing China

In order to improve the reliability of the spacecraft micro cold gas propulsion system and realize the precise control of the spacecraft attitude and orbit, a micro-thrust, high-precision cold gas thruster is carried out, at the same time due to the design requirements of the spacecraft, this micro-thrust should be continuous working more than 60 minutes, the traditional solenoid valve used for the thrusts can’t complete the mission, so a long-life micro latching valve is developed as the control valve for this micro thruster, because the micro latching valve can keep its position when it cuts off the outage. Firstly, the authors introduced the design scheme and idea of the thruster. Secondly, the performance of the latching valve and the flow characteristics of the nozzle were simulated. Finally, from the experimental results and compared with the numerical study, it shows that the long-life micro cold gas thruster developed in this paper meets the mission requirements.

关键词： High-Precision Micro Thruster Performance flow characteristic Experiment

Dynamic performance and temperature rising characteristic of a high-speed on/off valve based on pre-excitation control algorithm

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Chinese Journal of Aeronautics 2023年第10期36卷 445-458页

作者： Qi ZHONG Enguang XU Geng XIE Xiele WANG Yanbiao LI College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology Ministry of Education and Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310023China

High speed on/off valve(HSV)is an essential component in aerospace digital hydraulic systems(ADHS).Dynamic performance and temperature rising characteristic are two important features,which determine the performance of HSV,and affect the response speed and reliability of ADHS.Increasing the driving voltage is an effective method for improving the dynamic performance of HSV.However,continuous high voltage excitation will lead to more wasted energy,higher temperature rising and lower reliability.To solve this problem,a pre-excitation control algorithm(PECA)is proposed in this paper based on the theoretical model of the influence of electrical parameters on dynamic performance and temperature rising characteristics.In PECA,an appropriate initial coil current is generated by pre-excitation instead of increasing driving voltage,which significantly shortens the switching delay time.Then,based on real-time current online calculation and feedback mechanism,the adaptive switching of five equivalent voltages is realized.Consequently,the coil current can be rapidly kept at the expected state without consuming more energy and generating more heat.Results indicate that compared with conventional PWM control algorithm,the PECA can improve dynamic performance of HSV,shorten the total switching time by 71.5%,and increase the maximum operation frequency.Therefore,the linear area of flow characteristic is expended by 80.0%,the adjusting time of HSV-controlled system is reduced by 23%,while shortening steady error by 46.7%.Moreover,the temperature rising characteristics of HSV are better,the maximum operation temperature is reduced by 68.6%,and the time to reach the steady state temperature is shortened by 20%.From the results,it can be concluded that the PECA is not only an effective and practical control algorithm for improving the performance of HSVs and HSV-controlled systems while reducing the heat generation and decreasing the temperature rising of HSV,but also can be a potential solution in ADHS.

关键词： High speed on/off valve Dynamic performance Pre-excitation Temperature rising flow characteristic

Systematic analysis of distinct flow characteristics and underlying microstructural evolution mechanisms of a novel fine-grained P/M nickel-based superalloy during isothermal compression

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Journal of Materials Science & Technology 2023年第31期162卷 57-73页

作者： Hongning Wen Junsong Jin Xuefeng Tang Xinyun Wang Heyang Yang Yiding Zhang Lei Deng Pan Gong Qingsong Wei Yingjie He Jianzheng Guo State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Shenzhen Wedge Central South Research Institute Co. Ltd.Shenzhen 518000China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Isothermal forging(IF)is an effective method for forming difficult-to-deform materials like P/M superalloys.Understanding the isothermal compression microstructural evolution mechanism of a novel P/M s-peralloy provides the basis for its optimized IF planning.In this study,the isothermal compression tests of a novel fine-grained P/M nickel-based superalloy were carried out at 1000-1150℃with strain rates of 0.001-0.01 s^(−1).The results indicated that the alloy exhibits three distinct flow characteristics:continuous softening after reaching the peak stress,near-steady superplastic flow,and discontinuous hardening,corresponding to different strain rate sensitivity exponent(m)values.Varied microstructural evolution mechanisms,including grain boundary sliding(GBS),dynamic recrystallization(DRX),and grain growth,are dominated in different m-value domains.Meanwhile,different roles of primaryγ’play in microstruc-tural evolution were clarified.A moderate fraction of primaryγ’with 8.5%-14.2%can well coordinate the GBS and hinder excessive grain growth at a high m value domain(m>0.4).When 0.2

关键词： P/M nickel-based superalloy flow characteristic Microstructural evolution Superplastic flow Dynamic recrystallization

The Effect of the Gap Ratio on the flow and Heat Transfer over a Bluff Body in Near-Wall Conditions

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Fluid Dynamics & Materials Processing 2022年第1期18卷 109-130页

作者： Shaohua Zhai Guannan Xi School of Mechanical Engineering Nantong UniversityNantong226019China School of Mechanical Engineering Nantong Institute of TechnologyNantong226019China

In order to study the effect of different gap ratios on the thermofluid-dynamic field around a bluff body located in proximity to a heated wall,a series of experiments and numerical simulations have been conducted.The former were carried out using an open circulating water tank experimental platform and a single cylinder and square column as geometrical models(their characteristic length being D).The latter were based on the well-known SIMPLE algorithm for incompressible flow.The results show that the gap ratio is an important factor affecting the wake characteristics of near-wall bluff bodies.When the gap ratio is small,the influence of the wall on the bluff body wake is large.With an increase in the gap extension,periodic vortex shedding is enabled and heat transfer is strengthened accordingly;in addition,the vortex shedding period is larger for the square column.The square column displays hysteresis compared with the cylinder at the same gap ratio(the critical gap ratio of cylinder is 0.2~0.4,while that of square column is 0.40.6).

关键词： Transition flow gap ratio near-wall flow characteristic enhanced heat transfer

Study of the flow Mechanism of Wind Turbine Blades in the Yawed Condition

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Energy Engineering 2022年第4期119卷 1379-1392页

作者： Shuang Zhao Xijun Li Jianwen Wang College of Energy and Power Engineering Inner Mongolia University of TechnologyHohhot010051China Key Laboratory ofWind Energy and Solar Energy Technology Ministry of EducationHohhot010051China Key Laboratory of Wind and Solar Energy Utilization andOptimization in Inner Mongolia Autonomous Region Hohhot010051China Beijing Jingneng International Integrated Smart Energy Co. Ltd.Beijing100073China

The computational fluid dynamics method was used to simulate the flow field around a wind turbine at the yaw angles of 0°,15°,30°,and 45°.The angle of attack and the relative velocity of the spanwise sections of the blade were extracted with the reference points method.By analyzing the pressure distribution and the flow characteristics of the blade surface,the flow mechanism of the blade surface in the yawed condition was discussed.The results showed that the variations of the angle of attack and the relative velocity were related to the azimuth angle and the radius in the yawed condition.The larger the yaw angle was,the larger the variation was.The pressure distribution in the spanwise sections was affected by both the angle of attack and the relative velocity.The angle of attack was more influential than the relative velocity.At the same yaw angle,when the angle of attack decreased,the c_(p)∼x/c curve shrunk inward and the lift force decreased.The larger the yaw angle was,the more obvious the shrink was.The effect of the yaw on the blade root region was higher than its effect on the blade tip region.

关键词： flow characteristic angle of attack relative velocity pressure coefficient flow separation

Numerical Study on the 3-D Complex characteristics of flow Around the Hull Structure of TLP

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China Ocean Engineering 2015年第4期29卷 535-550页

作者：谷家扬朱新耀杨建民卢燕祥肖龙飞 School of Naval Architecture and Marine Engineering Jiangsu University of Science and Technology State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University

Vortex-induced motion is based on the complex characteristics of the flow around the tension leg platform （TLP） hull. By considering the flow field of the South China Sea and the configuration of the platform, three typical flow velocities and three flow directions are chosen to study the numerical simulation of the flow field characteristics around the TLP hull. Reynolds-averaged Navier-Stokes equations combined with the detached eddy simulation turbulence model are employed in the numerical study. The hydrodynamic coefficients of columns and pontoons, the total drag and lift coefficients of the TLP, the formation and development of the wake, and the vorticity iso-surfaces for different inlet velocities and current directions are discussed in this paper. The average value of the drag coefficient of the upstream columns is considerably larger than that of the downstream columns in the inlet direction of 0°. Although the time history of the lift coefficient demonstrates a ＂beating＂ behavior, the plot shows regularity in general. The Strouhal number decreases as the inlet velocity increases from the power spectral density plot at different flow velocities. The mean root values of the lift and drag coefficients of the front column decrease as the current direction increases. Under the symmetrical configuration of 45°, the streamwise force on C4 is the smallest, whereas the transverse force is the largest. The broken vortex conditions in current directions of 22.5° and 45° are more serious than that in the current direction of 0°. In addition, turbulence at the bottom of the TLP becomes stronger when the current direction changes from 0° to 45°. However, a high inlet velocity indicates a large region influenced by the broken vortex and shows the emergence of the wake behind the TLP under the same current angle.

关键词： TLP flow characteristic Strouhal number hydrodynamic coefficient vorticity ISO surface

Physical model of fluid flow characteristics in RH-TOP vacuum refining process

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International Journal of Minerals,Metallurgy and Materials 2012年第6期19卷 483-489页

作者： Lu Lin Yan-ping Bao Feng Yue Li-qiang Zhang Hong-lin Ou State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing Beijing 100083 China Engineering Research Institute University of Science and Technology Beijing Beijing 100083 China

To understand the characteristic of circulation flow rate in 250-t RH-TOP vacuum refining process, the 1：4 water model test was established through the bubble behavior and gas holdup in the up-leg to investigate the effects of different processes and equipment parame- ters on the RH circulation flow rate. With the increases of lifting gas flow rate, liffing bubble travel, and the internal diameter of the up-leg, and the decrease of nozzle diameter, the work done by bubble floatage and the circulation flow rate increase. The expression of circulation flow rate was derived fi＂om the regression analysis of experiment data. Meanwhile, the influences of vacuum chamber pressure and nozzle blockage situation on the circulation flow rate were discussed in detail by the bubble behavior and gas holdup in the up-leg. It is necessary to maintain a certain vacuum chamber liquid level in the molten steel circulation flow. Compared with a nozzle with symmetrical blockage in the up-leg, when a nozzle with non-symmetrical blockage is applied, the lifting gas distribution is non-uniform, causing a great effect on the molten steel circulation flow and making the circulation flow drop largely.

关键词： steelmaking refining molten steel flow characteristic bubbles nozzles

THE RELATIONSHIP BETWEEN flow characteristicSAND AERODYNAMIC DRAG OF VAN-BODY TRUCK

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Journal of Hydrodynamics 1999年第2期11卷 71-76页

作者： Du Guang-sheng Wang Zhi Feng Yuan Liu Li-ping Zhu Hui-min(Shandong University of Technology, Jinan 250061, P. R. ChinaLiu YiTsinghua University, Beijing 100084, P. R. China) Shanghai Univ of Technology Shanghai China

The surface airflow characteristics of a van-body truck are investigated bymeans of force measurement, pressure measurement and flow visualization. The influenceof the surface airflow is examined by adjusting the gap and height difference between driver cab and van. And the relationship between the flow characteristic and aerodynamicdrag are analyzed to provide a reference for designing aerodynamic shape of van-bodytruck and drag-reducing attachments.

关键词： van-body truck flow characteristic aerodynamic drag