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Asymmetric flow effect in a horizontal natural ventilated tunnel with different aspect ratios under the influence of longitudinal fire locations

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Building Simulation 2021年第4期14卷 1311-1323页

作者： Longxing Yu Huaxian Wan Jie Ji State Key Laboratory of Fire Science University of Science and Technology of ChinaJinZhai Road 96HefeiAnhui230026China College of Environment and Resources Fuzhou UniversityXueyuan Road 2FuzhouFujian350116China

This paper has analyzed the asymmetric flow effect of fire-induced thermal flow in a horizontal tunnel under the natural ventilation condition by conducting large eddy simulations (LES). The key objective is to reveal and to have a better understanding of the asymmetric flow effect caused by the upstream and downstream tunnel length difference. The mechanism behind it can be explained based on the conservation of mass and dynamic force analysis on the smoke and fresh air. The strength of the asymmetric flow effect is characterized by the mass flow rate of the induced longitudinal flow (net mass flow rate of a cross-section). An empirical correlation to predict the induced longitudinal mass flow rate is proposed. Furthermore, the law of smoke and air flow distribution within a horizontal tunnel is established. The proportion of smoke (or air) flowing out (or coming in) through the opening increase (or decrease) linearly with the increasing distance between that opening to the fire location. The variation of the air flow with the longitudinal fire location in a tunnel is more sensitive than the smoke flow. Results have shown that as the fire approaches the tunnel exit from the middle of the tunnel, the smoke spilling out through this opening is reduced from 50% to 40%, while the fresh air incoming from this opening is increased from 50% to 100% and vice versa.

关键词： asymmetric flow effect fire location thermal flow smoke tunnel fire CFD

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Piston-ring and Cylinder-liner Lubrication in Internal Combustion Engines Based on Thermo-hydrodynamic

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Chinese Journal of Mechanical Engineering 2011年第6期24卷 971-975页

作者： ZHANG Junhong GAO Hongge NI Guangjian State Key Laboratory of Engine Tianjin UniversityTianjin 300072China Tianjin Internal Combustion Engine Research Institute Tianjin 300072China

Currently the extruded effect,roughness to the lubricant shear thinning,temperature changes and other factors or some combination of a single factor mainly considered in the lubrication study of piston *** the study of the energy equation,the oil viscosity-temperature properties,adsorption layer characteristics are usually not *** the theoretical research is different from the actual situation of *** lubrication of piston ring-cylinder liner system in internal combustion(IC) engines is studied here based on the theory of thermal *** unsteady and compressible hydrodynamic lubrication model with an equivalent viscosity based on shear and extruded flow factor is derived by employing the viscosity-temperature relationship,meanwhile,characteristics such as lubricating oil’s density varying with pressure and temperature,thickness of adsorbent layer and oil film’s geometry are also considered in this *** setting up the energy equation,the effect of lubricating oil’s volume expansion and viscous dissipation on temperature,the heat conduction along oil film’s thickness direction are *** difference equation is formed by using a first-order difference scheme in time scale and second-order difference scheme in space scale.A common diesel engine is introduced as an instance to predict the distribution of the minimum oil film thickness in the piston ring-cylinder liner *** results of simulation calculation show that the minimum oil film thickness will decrease especially around the top dead center when the oil’s volume expansion,viscous dissipation and heat conduction are considered,which implies that:it is essential to take the thermal flow idea into account during investigating piston ring-cylinder liner system’s lubrication.A more complete piston ring-cylinder liner lubrication theory was established according to thermal fluids from the perspective of *** is more helpful to guide the practical applicat

关键词： thermal flow piston ring-cylinder liner adsorbent layer viscosity-temperature revision

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Thermographic Observation of High-Frequency Ethanol Droplet Train Impingement on Heated Aluminum and Glass Surfaces

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Fluid Dynamics & Materials Processing 2022年第6期18卷 1711-1718页

作者： Baris Burak Kanbur Sheng Quan Heng Fei Duan School of Mechanical and Aerospace Engineering Nanyang Technological University639798Singapore

The present study considers the impingement of a train of ethanol droplets on heated aluminum and glass *** surface temperature is allowed to vary in the interval 140℃–240℃.Impingement is considered with an inclination of 63 *** droplet diameter is 0.2 mm in both aluminum and glass surface *** gradients are observed with a thermographic *** is found that in comparison to glass,the aluminum surface displays very small liquid accumulations and better evaporation performance due to its higher thermal *** relatively low thermal conductivity of glass results in higher thermal gradients on the *** droplet impact area on the aluminum surface is smaller than the corresponding area for the glass ***,the liquid accumulation area is not ***,the extension of the droplet train impact region decreases on increasing the surface temperature because higher temperature values allow greater surface energy levels that enhance significantly the evaporation rate.

关键词： Droplet impingement boiling thermal flow droplet spreading two phase flow heat transfer

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Optimization of the Cooling System of Electric Vehicle Batteries

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Fluid Dynamics & Materials Processing 2022年第3期18卷 835-850页

作者： A.Heri Iswanto Iwan Harsono Alim Al Ayub Ahmed Sergushina Elena Sergeevna Stepan Krasnikov Rustem Zalilov John William Grimaldo Guerrero Liliya N.Latipova Safa Kareem Hachim Public Health Department Faculty of Health ScienceUniversity of Pembangunan Nasional Veteran JakartaJakarta16426Indonesia Universitas Mataram West Nusa Tenggara83116Indonesia School of Accounting Jiujiang UniversityJiujiang330300China National Research Ogarev Mordovia State University Saransk430005Russia Russian Technological University Moscow119454Russian Nosov Magnitogorsk State Technical University Magnitogorsk455000Russian Departamento de Energía Universidad de la CostaBarranquilla080002Colombia Kazan Federal University Kazan628400Russia College of Technical Engineering The Islamic UniversityNajaf54001Iraq

The most important components of electrical vehicles are the battery and the related cooling *** subsystems play a major role in determining the overall electric vehicle *** this study,a novel cooling system with fluid in the battery cell is proposed,by which the energy storage system can be optimized through control of the temperature of the batteries.A sensitivity analysis is conducted considering the maximum temperature,the heat rate,the coolant temperature,and the geometry of the *** numerical simulations show that the parameters for the trapezoidal compartment have an impact on the thermal performance of *** optimal geometry is proposed *** is concluded that for high values of Reynolds number for which the flow becomes turbulent,a decrease in the battery temperature can be obtained thereby avoiding thermal stresses.

关键词： thermal flow batteries geometry cavity cooling system

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