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Analysis of transient temperature field in coke drums

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Applied Mathematics and Mechanics(English Edition) 2010年第3期31卷 291-304页

作者：宁志华刘人怀 Key Laboratory of Disaster Forecast and Control in Engineering Ministry of Education of ChinaJinan University Institute of Applied Mechanics and Department of Mechanics and Civil Engineering Jinan University

One of the primary reasons leading to bulging and cracking in a coke drum is the severe temperature gradient due to cyclic temperature variation. Based on the twodimensional heat conduction theory, an analytical solution of the transient temperature field in the coke drum is obtained, which is different from the known FEM results. The length of the coke drum is considered finite. The dynamic boundary conditions caused by fluid uninterrupted rising in oiling and watering stages are simulated with the iteration method. Numerical results show that the present theoretical model can accurately describe basic features of the transient temperature field in the coke drum. Effects of the geometry of the coke drum and the rising velocity of quench water on the axial temperature gradient are also discussed.

关键词： coke drum cylindrical shell transient temperature field temperature gradient

Analysis Method of transient temperature field for Fuel Tank ofHigh-Altitude Large UAV

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Journal of Harbin Institute of Technology(New Series) 2016年第6期23卷 41-46页

作者： Qing Ai Liang Chen Xiaojing Xu Shiyu Liu Zhenwen Hu Xinlin Xia School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150000China AVIC Chengdu Aircraft Industry(Group)Co.Ltd. Chengdu 610091China

Based on the analysis of factors affecting transient temperature field of aircraft fuel tank and coupled heat transfer mechanism,a mathematical model of transient coupled heat transfer,including the dynamic change of fuel quality,the internal heat transfer,the external aerodynamic convection and the radiation heat transfer,is established. Taking the aerodynamic convection and radiation heat transfer outside the tank as the third kinds of thermal boundary conditions for the thermal analysis of the fuel tank,calculation of internal and external coupling heat of fuel tank is decoupled. Thermal network method combined with hierarchical dynamic grid is used to deal with the fuel consumption,and carry on the heat transfer analysis of the fuel tank. The numerical method for the transient temperature field of aircraft fuel tank is established. Through the simulation calculation,the transient temperature distribution of the fuel tank under different flight conditions is obtained,and the influence of the fuel mass and the external thermal environment on the temperature field is analyzed.

关键词： unmanned aerial vehicle fuel tank transient temperature field numerical simulation

Impacts of Startup,Shutdown and Load Variation on transient temperature and Thermal Stress fields within Blades of Gas Turbines

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Journal of Thermal Science 2022年第3期31卷 727-740页

作者： CAI Liuxi HOU Yanfang LI Fang LI Yun WANG Shunsen MAO Jingru School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

Based on the actual operation parameters and temperature-dependent material properties of a gas turbine unit,composite cooling blade model and corresponding reliable boundary conditions were established.transient thermal-fluid-solid coupling simulations were then comprehensively conducted to analyze the transient flow and the temperature field of the blade under startup,shutdown,and variable loads condition.Combined with the obtained transient temperature data,the non-linear finite element method was exploited to examine the effect of these transient operations on the turbine blade thermal stress characteristics.Results show that the temperature and pressure on the blade surface increase with the load level and vice versa.As the startup process progresses,the film cooling effectiveness and the heat convection of airflows inside the blade continuously grow;high-temperature areas on the pressure surface and along the trailing edge of the blade tip gradually disappear.Locally high-temperature zones with the maximum of 1280 K are generated at the air inlet and outlet of the blade platform and the leading edge of the blade tip.The high thermal stresses detected on the higher temperature side of the temperature gradient are commonly generated in places with large temperature gradients and significant geometry variations.For the startup/shutdown process,the rate of increase/decrease of the thermal stress is positively correlated with the load variation rate.A slight variation rate of the load(1.52%/min)can lead to an apparent alteration(41%)to the thermal stress.In operations under action of the variable load,although thermal stress is less sensitive to the load variation,the rising or falling rate of the exerted load still needs to be carefully controlled due to the highly leveled thermal stresses.

关键词： composite cooling blade thermal-fluid-solid coupling method transient temperature field load variation thermal stress

Thermomechanical Behavior of Brake Drums Under Extreme Braking Conditions

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Computers, Materials & Continua 2022年第8期72卷 2259-2273页

作者： T.Khatir M.Bouchetara K.Derrar M.Djafri S.Khatir M.Abdel Wahab Institute of Science and Technology University Center Salhi Ahmed NaamaAlgeria Laboratory of Gas Combustion and Environment University of Sciences and Technology of OranL.P 1505 El-MenaouerOranUSTO 31000Algeria High School of Aeronautic Techniques Dar El Beida Algeria Ho Chi Minh City Open University Ho Chi Minh CityViet Nam Faculty of Engineering Van Lang UniversityHo Chi Minh CityVietnam Soete Laboratory Faculty of Engineering and ArchitectureGhent UniversityTechnologieparkZwijnaarde 903B-9052 ZwijnaardeBelgium

Braking efficiency is characterized by reduced braking time and distance,and therefore passenger safety depends on the design of the braking system.During the braking of a vehicle,the braking system must dissipate the kinetic energy by transforming it into heat energy.A too high temperature can lead to an almost total loss of braking efficiency.An excessive rise in brake temperature can also cause surface cracks extending to the outside edge of the drum friction surface.Heat transfer and temperature gradient,not to forget the vehicle’s travel environment(high speed,heavy load,and steeply sloping road conditions),must thus be the essential criteria for any brake system design.The aim of the present investigation is to analyze the thermal behavior of different brake drum designs during the single emergency braking of a heavy-duty vehicle on a steeply sloping road.The calculation of the temperature field is performed in transient mode using a three-dimensional finite element model assuming a constant coefficient of friction.In this study,the influence of geometrical brake drum configurations on the thermal behavior of brake drums with two different materials in grey cast iron FG200 and aluminum alloy 356.0 reinforced with silicon carbide(SiC)particles is analyzed under extreme vehicle braking conditions.The numerical simulation results obtained using FE software ANSYS are qualitatively compared with the results already published in the literature.

关键词： Drum brake finite element method braking energy distribution friction heat power friction heat flux transient temperature field

A Mathematical Model of Heat Transfer in Problems of Pipeline Plugging Agent Freezing Induced by Liquid Nitrogen

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Fluid Dynamics & Materials Processing 2022年第3期18卷 775-788页

作者： Yafei Li Yanjun Liu Southwest Petroleum University Chengdu610500China

A mathematical model for one-dimensional heat transfer in pipelines undergoing freezing induced by liquid nitrogen is elaborated.The basic premise of this technology is that the content within a pipeline is frozen to form a plug or two plugs at a position upstream and downstream from a location where work a modification or a repair must be executed.Based on the variable separation method,the present model aims to solve the related coupled heat conduction and moving-boundary phase change problem.An experiment with a 219 mm long pipe,where water was taken as the plugging agent,is presented to demonstrate the relevance and reliability of the proposed model(results show that the error is within 18%).Thereafter,the model is applied to predict the cooling and freezing process of pipelines with different inner diameters at different liquid nitrogen refrigeration temperatures when water is used as the plugging agent.

关键词： Pipeline freezing and plugging liquid nitrogen refrigeration heat transfer model transient temperature field phase change prediction

NUMERICAL SIMULATION OF THE THREE-DIMENSIONAL temperature field IN LASER CLADDING FORMING PROCESS

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NUMERICAL SIMULATION OF THE THREE-DIMENSIONAL TEMPERATURE FI...