二冲程液压自由活塞发动机换气过程影响因素的仿真研究
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摘要
利用CONVERGE软件建立了二冲程液压自由活塞发动机换气过程的三维计算流体动力学(computational fluid dynamics,CFD)仿真模型,并且基于液压自由活塞发动机的独特结构,研究了气口比时面值、扫气箱压缩比、活塞顶倾角和活塞杆直径对换气过程的影响。结果表明:在未发生废气倒流时,扫气效率主要与扫气比时面值有关,增大扫气比时面值有利于提高扫气效率;捕获率主要与排气比时面值有关,减小排气比时面值有利于增大捕获率;提高扫气箱压缩比有利于提高扫气效率,扫气箱压缩比从1.2增加到2.1,扫气效率提升9.8%;适当增大活塞顶倾角有利于扫气效率和捕获率的提高;减小活塞杆直径有利于提升扫气效率,但同时会导致捕获率下降。
A three-dimensional computational fluid dynamics(CFD)simulation model of two-stroke hydraulic free-piston engine(HFPE)was built by the CONVERGE.The effects of specific time-area value,compression ratio of scavenge case,piston top angle,and piston rod diameter on scavenging process were studied based on the unique structure of the HFPE.The results show that the scavenging efficiency is mainly affected by the specific scavenging time-area value when there is no backflow of exhaust gas,and the improvement of the later is beneficial to the former.The capture ratio is mainly affected by the specific timearea value of exhaust,and the reduction in the later can increase the former.Increasing the scavenge case compression ratio from 1.2 to 2.1 can promote the scavenging efficiency by 9.8%.The appropriate increase of the piston top angle is beneficial to the improvement of the scavenging efficiency and capture ratio.Decreasing the diameter of the piston rod diameter can increase the scavenging efficiency,but it will reduce the capture ratio.
A three-dimensional computational fluid dynamics(CFD)simulation model of two-stroke hydraulic free-piston engine(HFPE)was built by the CONVERGE.The effects of specific time-area value,compression ratio of scavenge case,piston top angle,and piston rod diameter on scavenging process were studied based on the unique structure of the HFPE.The results show that the scavenging efficiency is mainly affected by the specific scavenging time-area value when there is no backflow of exhaust gas,and the improvement of the later is beneficial to the former.The capture ratio is mainly affected by the specific timearea value of exhaust,and the reduction in the later can increase the former.Increasing the scavenge case compression ratio from 1.2 to 2.1 can promote the scavenging efficiency by 9.8%.The appropriate increase of the piston top angle is beneficial to the improvement of the scavenging efficiency and capture ratio.Decreasing the diameter of the piston rod diameter can increase the scavenging efficiency,but it will reduce the capture ratio.
引文
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[2]HANIPAH M R,MIKALSEN R,ROSKILLY A P.Recent commercial free-piston engine developments for automotive applications[J].Applied Thermal Engineering,2015,75:493-503.
[3]ZHU Y S,WANG Y,ZHEN X D,et al.The control of an opposed hydraulic free piston engine[J].Applied Energy,2014,126:213-220.
[4]GENG H M,WANG Y,ZHEN X,et al.Study on adaptive behavior and mechanism of compression ratio(or piston motion profile)for combustion parameters in hydraulic free piston engine[J].Applied Energy,2018,211:921-928.
[5]LARJOLA J,HONKATUKIA J,SALLINEN P,et al.Fluid dynamic modeling of a free piston engine with labyrinth seals[J].Journal of Thermal Science,2010,19(2):141-147.
[6]栾延龙,李理光,王哲,等.自由活塞发动机关键设计参数及其性能的仿真优化研究[J].内燃机工程,2010,31(2):15-21.LUAN Y L,LI L G,WANG Z,et al.Key design parameters and performance optimization of a free-piston engine based on simulation[J].Chinese Internal Combustion Engine Engineering,2010,31(2):15-21.
[7]MIKALSEN R,ROSKILLY A P.Performance simulation of a spark ignited free-piston engine generator[J].Applied Thermal Engineering,2008,28(14/15):1726-1733.
[8]傅煜,王哲,臧鹏飞,等.直线发动机换气系统关键参数优化研究[J].内燃机工程,2017,38(5):120-126.FU Y,WANG Z,ZANG P F,et al.Key parameters optimization of the scavenging system on linear engine[J].Chinese Internal Combustion Engine Engineering,2017,38(5):120-126.
[9]张栓录,赵长禄,赵振峰,等.液压自由活塞发动机直流扫气设计及优化研究[J].内燃机工程,2016,37(6):110-115.ZHANG S L,ZHAO C L,ZHAO Z F,et al.Scavenging design and optimization for hydraulic free piston diesel engine[J].Chinese Internal Combustion Engine Engineering,2016,37(6):110-115.
[10]姜一通.自由活塞内燃发电系统换气过程研究[D].北京:北京理工大学,2015.
[11]YUAN C,REN H,XU J.Comparison of the gas exchange of a loop scavenged free-piston engine alternator and the conventional engine[J].Applied Thermal Engineering,2017,127:638-649.
[12]刘福水,姜一通,张长岭,等.自由活塞内燃发电机低速不稳定性影响因素分析[J].农业工程学报,2014,30(18):109-115.LIU F S,JIANG Y T,ZHANG C L,et al.Analysis on influence factors of low-speed instability in free-piston enginegenerator[J].Transactions of the Chinese Society of Agricultural Engineering,2014,30(18):109-115.
[13]GOLDBOROUGH S S,BLARIGAN P V.Optimizing the scavenging system for a two-stroke cycle,free piston engine for high efficiency and low emissions:a computational approach[C/OL].SAE Paper,2003,2003-01-0001.(2013-03-03).https://doi.org/10.4271/2003-01-0001.
[14]李冀辉,汪洋,徐帅卿,等.活塞运动规律对点燃式HFPE燃烧过程影响的仿真研究[J].内燃机工程,2017,38(6):23-28.LI J H,WANG Y,XU S Q,et al.Simulative research of impact of piston motion law on spark-ignition hydraulic free piston engine combustion process[J].Chinese Internal Combustion Engine Engineering,2017,38(6):23-28.
[15]LIU Y D,JIA M,XIE M Z,et al.Enhancement on a skeletal kinetic model for primary reference fuel oxidation by using a semidecoupling methodology[J].Energy&Fuels,2012,26(12):7069-7083.
[16]史宗庄.二冲程汽油机气口的设计计算[J].小型内燃机与车辆技术,1978(4):1-29.