可变气门升程与正时对直喷汽油机缸内流动特性的影响
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摘要
利用CFD三维数值模拟软件模拟了1台缸内直喷汽油机的进气及压缩过程,分析比较了不同最大气门升程及进气正时下缸内流场的变化规律。结果表明:减小最大气门升程可以使进气行程中缸内气体的速度及湍动能显著增加,但在压缩末期的滚流比要略小;在小气门升程下,进气门早开或者晚开都会使得进气过程的湍动能显著增加,在距上止点5mm,10 mm,15 mm的3个横截面上,早开和晚开进气门会使最大平均湍动能分别增加28.29%和43.47%,20.7%和40.81%,23.07%和49.58%,但在压缩后期间,进气门早开或者晚开时对缸内的平均湍动能影响不大;在小气门升程下,进气门的开启时间对压缩末期湍动能的分布有较大的影响,早开或者晚开进气门会使缸内的湍动能趋于一致。
The intake and compression process for a gasoline direct injection engine were simulated with CFD software and the change law of in-cylinder flow field under different maximum valve lifts and timings was analyzed.The results show that the gas velocity and turbulent kinetic energy significantly increase with the decrease of maximum valve lift in the intake stroke,but the tumble ratio is small at the end of the compression stroke.For a small valve lift,the early opening or late closing of intake valve will lead to the significant increase of turbulent kinetic energy in the intake stroke.Correspondingly,the maximum average turbulent kinetic energies at three cross sections of 5mm,10 mm,and 15 mm away from TDC increase by 28.29% and43.47%,20.7% and 40.81%,23.07% and 49.58% respectively.However,the early opening or late closing of intake valve has little effect on the average turbulent kinetic energy at the end of the compression stroke.In addition,the opening time of intake valve has a great influence on the distribution of turbulent kinetic energy at the end of compression,and the advance or delay of intake timing will promote the homogeneity of in-cylinder turbulent kinetic energy.
The intake and compression process for a gasoline direct injection engine were simulated with CFD software and the change law of in-cylinder flow field under different maximum valve lifts and timings was analyzed.The results show that the gas velocity and turbulent kinetic energy significantly increase with the decrease of maximum valve lift in the intake stroke,but the tumble ratio is small at the end of the compression stroke.For a small valve lift,the early opening or late closing of intake valve will lead to the significant increase of turbulent kinetic energy in the intake stroke.Correspondingly,the maximum average turbulent kinetic energies at three cross sections of 5mm,10 mm,and 15 mm away from TDC increase by 28.29% and43.47%,20.7% and 40.81%,23.07% and 49.58% respectively.However,the early opening or late closing of intake valve has little effect on the average turbulent kinetic energy at the end of the compression stroke.In addition,the opening time of intake valve has a great influence on the distribution of turbulent kinetic energy at the end of compression,and the advance or delay of intake timing will promote the homogeneity of in-cylinder turbulent kinetic energy.
引文
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[11]Liu Kaimin,Yang Jing,Jiang Wu.Effect of asynchronous valve timing on combustion characteristic and performance of a high speed SI marine engine with five valves[J].Energy Conversionand Management,2016,123(1):185-199.
[12]Fischer J,Velji A,Spicher U.Investigation of cycle to cycle-to-cycle variations of in-cylinder processes in gasoline direct injection engines operating with variable tumble systems[C].SAE Paper 2004-01-0044.
[13]韩文艳,许思传,周岳康,等.滚流比对缸内直喷汽油机混合气形成及燃烧的影响[J].内燃机学报,2012,30(6):499-505.
[2]David Cleary,Gerald Silvas.Unthrottled Engine Operation with Variable Intake Valve Lift,Duration,and Timing[C].SAE Paper 2007-01-1282.
[3]王天友,刘大明.可变气门升程下汽油机缸内气体流动特性的研究[J].内燃机学报,2008,26(5):420-28.
[4]Tianyou Wang,Daming Liu,Bingqian Tan,et al.An Investigation into In-Cylinder Tumble Flow Characteristics with Variable Valve Lift in a GasolineEngine[J].Flow Turbulence Combust,2015,94:285-304.
[5]谈秉乾,王天友,王刚德,等.可变气门升程对4气门直喷汽油机缸内气流运动特性的影响[J].内燃机学报,2011,29(2):112-118.
[6]赵昌普,钟博,朱云尧,等.可变气门升程对涡轮增压缸内直喷汽油机缸内流动特性的影响[J].天津大学学报(自然科学与工程技术版),2013,46(8):737-742.
[7]赵昌普.变气门升程对涡轮增压缸内直喷汽油机工作过程影响的模拟研究[D].天津:天津大学,2011.
[8]胡顺堂,谢辉,陈韬,等.可变进气门升程对汽油机泵气损失的控制及对燃烧过程的影响[J].燃烧科学与技术,2011,17(1):29-34.
[9]张士强,刘瑞林,刘伍权,等.可变气门相异升程4气门汽油机稳态流动特性[J].内燃机学报,2014,32(1):57-63.
[10]刘凯敏,杨靖,邓帮林,等.非同步气门正时对高速汽油机进气及燃烧过程的影响[J].内燃机工程,2016,37(2):94-100.
[11]Liu Kaimin,Yang Jing,Jiang Wu.Effect of asynchronous valve timing on combustion characteristic and performance of a high speed SI marine engine with five valves[J].Energy Conversionand Management,2016,123(1):185-199.
[12]Fischer J,Velji A,Spicher U.Investigation of cycle to cycle-to-cycle variations of in-cylinder processes in gasoline direct injection engines operating with variable tumble systems[C].SAE Paper 2004-01-0044.
[13]韩文艳,许思传,周岳康,等.滚流比对缸内直喷汽油机混合气形成及燃烧的影响[J].内燃机学报,2012,30(6):499-505.