| AEROSPACE ENGINEERING |
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Numerical simulation of fuel flow and heat transfer in a serpentine tube considering the fuel variable properties |
| LI Yu, WANG Xiangqin, MIN Jingchun |
| School of Aerospace Engineering, Tsinghua University, Beijing 100084, China |
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Abstract [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, 600, 750, and 900 K, and serpentine tube straight section lengths of 65.000, 32.500, and 0 mm for both constant and variable fuel properties. The inlet fuel temperature is 350 K, whereas the pressure is 5 MPa. [Results] The calculation results revealed that the fuel temperature increased along the serpentine tube for both constant and variable fuel properties but increased more rapidly for variable properties than for constant properties. The fuel velocity remained constant for the constant property but varied nonlinearly for variable properties. The convective heat transfer coefficient remained almost constant for the constant property but exhibited a remarkable increase along the tube for variable properties. Moreover, the curved tube section exhibited a markedly larger convective heat transfer coefficient than the straight tube section. The variable property experienced a noticeably smaller pressure drop than the constant property, similar to the pressure drop in the curved tube section compared to the straight tube section; nevertheless, the pressure drop per unit tube length was considerably larger for the curved tube section than for the straight tube section. The tube wall temperature had a remarkable impact on fuel flow and heat transfer characteristics for the variable properties, whereas the straight tube segment length had a relatively weak influence on such characteristics. [Conclusions] The findings of this study support the fact that neglecting the variable fuel properties leads to an underestimation of the convective heat transfer coefficient and an overestimation of the pressure loss in the serpentine tubes used in air-fuel heat exchangers.
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| Keywords
serpentine tube
jet fuel
variable property
flow and heat transfer
numerical simulation
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Issue Date: 28 December 2023
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[1] BRUENING G B, CHANG W S. Cooled cooling air systems for turbine thermal management [C]//ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. Indianapolis, USA:ASME, 1999:V003T01A002.
[2] 苏雷. 航空发动机涡轮冷却空气预冷系统研究[D]. 沈阳:沈阳航空航天大学, 2018. SU L. Precooling turbine cooling air for aviation engines [D]. Shenyang:Shenyang Aerospace University, 2018. (in Chinese)
[3] TIBBS G. Test results of the Northrop Grumman corporation turbine engine bleed air/fuel heat exchanger after 165 hours of operation with JP-8+100 fuel [C]//AIAA and SAE, 1998 World Aviation Conference. Anaheim, USA:AIAA, 1998:5559.
[4] LU T J, STONE H A, ASHBY M F. Heat transfer in open-cell metal foams [J]. Acta Materialia, 1998, 46(10):3619-3635.
[5] 特尼格尔, 闻洁, 付衍琛, 等. 细管蛇形管换热器流动与换热特性实验研究[C]//中国航天第三专业信息网第39届技术交流会暨第3届空天动力联合会议论文集:S05发动机热管理技术. 洛阳, 中国:中国航天第三专业信息网, 2018:2-13. TENIGEER, WEN J, FU Y C, et al. Experimental study of flow and heat transfer characteristics for a thin tube serpentine heat exchanger [C]//Proceedings of the 39th Technical Exchange Conference and the 3rd Joint Conference on Aerospace Power of China Third Professional Information Network:S05 Engine Thermal Management Technology. Luoyang, China:China Third Professional Information, 2018:2-13. (in Chinese)
[6] LIU Y L, XU G Q, FU Y C, et al. Airside pressure drop characteristics of three analogous serpentine tube heat exchangers considering heat transfer for aero-engine cooling [J]. Chinese Journal of Aeronautics, 2022, 35(12):32-46.
[7] FU Y C, WEN J, TAO Z, et al. Experimental research on convective heat transfer of supercritical hydrocarbon fuel flowing through U-turn tubes [J]. Applied Thermal Engineering, 2017, 116:43-55.
[8] ZHANG C B, XU G Q, GAO L, et al. Experimental investigation on heat transfer of a specific fuel (RP-3) flows through downward tubes at supercritical pressure [J]. The Journal of Supercritical Fluids, 2012, 72:90-99.
[9] 任峰志. 冲压发动机中燃料/空气换热器设计方法研究[D]. 哈尔滨:哈尔滨工业大学, 2015. REN F Z. Research on designing method of fuel-air heat exchanger for use in ramjet [D]. Harbin:Harbin Institute of Technology, 2015. (in Chinese)
[10] 邓宏武, 李利昂, 杨家旺, 等. 航空发动机超轻高效换热器的发展与应用展望[J]. 航空动力学报, 2022, 37(10):2272-2285. DENG H W, LI L A, YANG J W, et al. Development and application prospect of light and high efficiency heat exchanger in aviation and aerospace [J]. Journal of Aerospace Power, 2022, 37(10):2272-2285. (in Chinese)
[11] 赵镇南, 时雨荃, 张毅, 等. 相变乳状液在蛇形管中的流动和传热特性[J]. 工程热物理学报, 2002, 23(6):730-732. ZHAO Z N, SHI Y Q, ZHANG Y, et al. Flow and heat transfer characteristics of phase-change emulsion in a coiled double-tube heat exchanger [J]. Journal of Engineering Thermophysics, 2002, 23(6):730-732. (in Chinese)
[12] 常勇强, 杨震, 赵振兴, 等. 蛇形管平行通道中高压气体的对流换热特性研究[J]. 西安交通大学学报, 2011, 45(3):53-57. CHANG Y Q, YANG Z, ZHAO Z X. Convection heat transfer characteristics of high-pressure gas in parallel channel heat exchanger with membrane serpentine tubes [J]. Journal of Xi'an Jiaotong University, 2011, 45(3):53-57. (in Chinese)
[13] 王晓艳. 水平蛇形管内传热特性实验研究[D]. 淄博:山东理工大学, 2011. WANG X Y. Experimental research on heat transfer characteristics in horizontal serpentine tube [D]. Zibo:Shandong University of Technology, 2011. (in Chinese)
[14] 姚旺. 水平蛇形管内流动阻力特性实验研究[D]. 淄博:山东理工大学, 2011. YAO W. Experimental research on flow resistance characteristic in horizontal serpentine tube [D]. Zibo:Shandong University of Technology, 2011. (in Chinese)
[15] 陈杨华, 肖炜, 郭文帅, 等. 蛇形管蓄能箱蓄热过程的数值模拟[J]. 南昌大学学报(工科版), 2013, 35(2):163-167. CHEN Y H, XIAO W, GUO W S, et al. Numerical simulation about thermal energy storage process of serpentine tube energy storage [J]. Journal of Nanchang University (Engineering & Technology), 2013, 35(2):163-167. (in Chinese)
[16] CUI X Y, GUO J F, HUAI X L, et al. Numerical investigations on serpentine channel for supercritical CO2 recuperator [J]. Energy, 2019, 172:517-530.
[17] 张明. 超临界压力蛇形管内航空煤油RP-3氧化结焦特性研究[D]. 哈尔滨:哈尔滨工业大学, 2021. ZHANG M. Investigation on the characteristic of thermal oxidation deposition of RP-3 kerosene in serpentine tubes under supercritical pressure [D]. Harbin:Harbin Institute of Technology, 2021. (in Chinese)
[18] 徐国强, 陶智, 丁水汀, 等. 一种适用于燃气涡轮发动机的空-油换热器:200910238384.X [P]. 2010-05-12. XU G Q, TAO Z, DING S T, et al. A kind of air-fuel heat exchanger for gas turbine engine:200910238384.X [P]. 2010-05-12. (in Chinese)
[19] 杨世铭, 陶文铨. 传热学[M]. 4版. 北京:高等教育出版社, 2006. YANG S M, TAO W Q. Heat transfer [M]. 4th ed. Beijing:Higher Education Press, 2006. (in Chinese)
[20] GU L D, MIN J C, WU X M, et al. Airside heat transfer and pressure loss characteristics of bare and finned tube heat exchangers used for aero engine cooling considering variable air properties [J]. International Journal of Heat and Mass Transfer, 2017, 108:1839-1849. |
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2024,
Vol. 64
