传热对微型摆式发动机性能的影响机制分析
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摘要
建立了微型摆式发动机(Micro internal combustion swing engine,MICSE)的计算模型,揭示了传热及其尺度效应对微型摆式发动机性能的影响机制。结果表明:壳体仅在一个较薄的热缓存层内与工质气体进行周期性热交换。在进气过程中,热缓存层对气体的传热会提高气体温度,从而降低进气质量和压缩比;在做功过程中,气体对热缓存层的传热减少做功,这两方面都会降低系统热效率。尺寸越小,进气气体在热缓存层传热下的温升越大,相对进气质量和压缩比越低;做功过程中的气体向热缓存层的传热量占燃气总化学能的比值越高。因此尺寸越小,传热效应增强,热效率越低。
A computational model of a micro internal combustion swing engine(MICSE)is established.The mechanism of the heat transfer and its scale effect on the system performance are analyzed.The results show that the heat exchange between the gas and the solid wall occurs in a thin thermal buffer layer close to the contact area.In the intake process,the hot thermal buffer layer heats the intake gas,thereby reducing the intake air mass,resulting in a compression ratio drop.While in the power process,the heat transfer from the gas to the thermal buffer layer reduces the work output.Hence the thermal efficiency declines.The smaller the engine scale is,the gas temperature in the intake stroke increases for the influence of the thermal buffer layer,the less the dimensionless inlet air mass and the compression ratio will be.While in the power process,the ratio of the thermal transferred from the gas to thermal buffer layer to the fuel chemical energy increases with the reduction of engine scale.Therefore,the heat transfer enhances and the thermal efficiency drops with the reduction of the engine scale.
A computational model of a micro internal combustion swing engine(MICSE)is established.The mechanism of the heat transfer and its scale effect on the system performance are analyzed.The results show that the heat exchange between the gas and the solid wall occurs in a thin thermal buffer layer close to the contact area.In the intake process,the hot thermal buffer layer heats the intake gas,thereby reducing the intake air mass,resulting in a compression ratio drop.While in the power process,the heat transfer from the gas to the thermal buffer layer reduces the work output.Hence the thermal efficiency declines.The smaller the engine scale is,the gas temperature in the intake stroke increases for the influence of the thermal buffer layer,the less the dimensionless inlet air mass and the compression ratio will be.While in the power process,the ratio of the thermal transferred from the gas to thermal buffer layer to the fuel chemical energy increases with the reduction of engine scale.Therefore,the heat transfer enhances and the thermal efficiency drops with the reduction of the engine scale.
引文
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[13]周雄.基于三臂自由摆动式活塞发动机的微型能源动力系统理论与实验研究[D].北京:中国科学院工程热物理研究所,2017.ZHOU Xiong.Theoretical and experimental studies on a micro power generation system based on a threearm free-piston swing engine[D].Beijing:Institute of Engineering,Thermophysics Chinese Academy of Sciences,2017.
[14]周雄,孔文俊.燃烧特征参数对MICSE性能及热力过程的影响[J].工程热物理学报,2015,36(5):1125-1129.ZHOU Xiong,KONG Wenjun.Effects of combustion characteristics on the performances and thermodynamic process of MICSE[J].Journal of Engineering Thermophysics,2015,36(5):1125-1129.
[15]杨世铭,陶文铨.传热学[M].4版.北京:高等教育出版社,2006.
[2]EPSTEIN A H.Millimeter-scale,micro-electro-mechanical systems gas turbine engines[J].Journal of Engineering for Gas Turbines&Power,2004,126(2):205-226.
[3]SPRAGUE S B,PARK S W,WALTHER D C,et al.Development and characterisation of small-scale rotary engines[J].International Journal of Alternative Propulsion,2007,19(1):275-293.
[4]AICHLMAYR H T,KITTELSON D B,ZACHARIAH M R.Miniature free-piston homogeneous charge compression ignition engine-compressor concept—part I:Performance estimation and design considerations unique to small dimensions[J].Chemical Engineering Science,2002,57(19):4173-4186.
[5]DAHM W,MIJIT K,MAYOR R.Micro internal combustion swing engine(MICSE)for portable power generation systems[C]∥40th AIAA Aerospace Sciences Meeting.[S.l.]:AIAA,2002.
[6]GU Y.Gasdynamic modeling and parametric study of mesoscale internal combustion swing engine/generator systems[D].Ann Arbor:University of Michigan,2006.
[7]ZHOU X,ZHANG Z,KONG W,et al.Investigations of leakage mechanisms and its influences on a micro swing engine considering rarefaction effects[J].Applied Thermal Engineering,2016,106:674-680.
[8]FU K.Design and experimental results of small-scale rotary engines[C]∥Proceedings of the 2001 ASME International Mechanical Engineering-Congress and Exposition.[S.l.]:ASME,2001.
[9]MENON S K.The scaling of performance and losses in miniature internal combustion engines[D].Ann Arbor:University of Michigan,2010.
[10]MENON S,CADOU C P.Scaling of miniature piston engine performance,Part 2:Energy losses[J].Journal of Propulsion&Power,2013,29(4):788-799.
[11]FRANCO A,MARTORANO L.Evaluations on the heat transfer in the small two stroke engines[R].SAE Paper 980762,1998.
[12]徐健华,夏晨,黄国平,等.微型旋转摆式发动机性能影响因素分析[J].中国科学:技术科学,2017(6):596-604.XU Jianhua,XIA Chen,HUANG Guoping,et al.Analysis on the performance of micro swing rotor engine[J].Scientia Sinica:Technologica,2017(6):596-604.
[13]周雄.基于三臂自由摆动式活塞发动机的微型能源动力系统理论与实验研究[D].北京:中国科学院工程热物理研究所,2017.ZHOU Xiong.Theoretical and experimental studies on a micro power generation system based on a threearm free-piston swing engine[D].Beijing:Institute of Engineering,Thermophysics Chinese Academy of Sciences,2017.
[14]周雄,孔文俊.燃烧特征参数对MICSE性能及热力过程的影响[J].工程热物理学报,2015,36(5):1125-1129.ZHOU Xiong,KONG Wenjun.Effects of combustion characteristics on the performances and thermodynamic process of MICSE[J].Journal of Engineering Thermophysics,2015,36(5):1125-1129.
[15]杨世铭,陶文铨.传热学[M].4版.北京:高等教育出版社,2006.