蛇形管内燃油变物性流动换热特性数值模拟  

Numerical simulation of fuel flow and heat transfer in a serpentine tube considering the fuel variable properties

作　　者：李玉 王相钦 闵敬春[1] LI Yu;WANG Xiangqin;MIN Jingchun(School of Aerospace Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学航天航空学院,北京100084

出　　处：《清华大学学报（自然科学版）》2024年第2期337-345,共9页Journal of Tsinghua University(Science and Technology)

基　　金：国家重大专项基础研究项目(2017-Ⅲ-0005-0030)。

摘　　要：蛇形管空油换热器可用于航空发动机的冷却,该文通过数值模拟研究了蛇形管内航空煤油的流动换热特性,分析了燃油入口流速、管壁温及蛇形管直管段长度对流动换热的影响,对比了直管段与弯管段、常物性与变物性下流动换热特性的差异。综合考虑换热器的紧凑度及燃油流过换热器时可能发生结焦,蛇形管内径取值2.0 mm,另外燃油流过蛇形管时被加热,温度可以升高数百摄氏度,燃油物性将会产生剧烈变化,因此本研究特别关注蛇形细管内燃油的变物性流动换热特性。研究结果表明:弯管段的对流换热系数明显高于直管段,但同时弯管段压降也显著增大;变物性的对流换热系数明显高于常物性,而变物性的压损明显低于常物性;变物性时管壁温对流动换热特性的影响较为显著,而直管段长度对流动换热特性的影响相对较弱。[Objective] Air-fuel heat exchangers consisting of serpentine tubes are used to cool aero-engines,whose turbine blades and other hot parts are generally cooled by the air taken from the compressor outlet,which may have temperatures as high as 900 K.A practical approach uses engine fuel,usually at a temperature close to the normal atmospheric temperature,to precool the air taken from the compressor outlet to improve its cooling capacity.This process can be realized in air-fuel heat exchangers.This work aims to analyze the fuel flow and heat transfer in a serpentine tube and explore the influence of fuel inlet velocity,tube wall temperature,and straight section length of the serpentine tube on the flow and heat transfer characteristics,with an emphasis on the differences in such characteristics between the straight and curved tube segments of the serpentine tube and between the constant and variable fuel properties.[Methods] Considering heat exchanger compactness and the possible coking that may take place during the flow of fuel through the heat exchanger,the inside diameter of the serpentine tube is set to be 2.0 mm.To arrange the heat exchanger in the annular space between the combustion chamber wall and the main shaft of the aero-engine,the straight section length of the serpentine tube is set to be 65.000 mm.The serpentine tube is composed of 14 straight and 13 curved tube segments,constituting approximately 7 cycles,provided that 1 cycle is defined to include 2 straight and 2 curved tube segments.When the fuel flows through the serpentine tube,its temperature may increase by several hundred degrees Kelvin.This aspect promptes the consideration of fuel variable properties in the simulation model.The uniqueness of this work lies in the fact that it deals with variable property fuel flow and heat transfer in a thin serpentine tube.The low Reynolds number k-ω flow model is employed in the simulations,and calculations are implemented for fuel entering velocities of 1,2,3,4,and 5 m/s,tube wall temperatures of 450,

关 键 词：蛇形管 航空煤油 变物性 流动换热 数值模拟 

分 类 号：TK172[动力工程及工程热物理—热能工程]