柴油机不同类型喷嘴内部空化流动特性的研究  

Study on Cavitating Flow in Different Types of Diesel Nozzle Orifice

作　　者：张军[1] 杜青[1,2] 杨延相[1] 孙剑[1] 

机构地区：[1]天津大学内燃机研究所,天津300072 [2]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《内燃机学报》2010年第2期133-140,共8页Transactions of Csice

基　　金：国家自然科学基金资助项目(50876072);天津市应用基础研究计划资助项目(07JCYBJC03900)

摘　　要：柴油喷嘴内部空化效应是燃油液体射流雾化的重要原因之一。针对目前发动机上广泛采用的SAC型和VCO型两种柴油机多孔喷嘴,运用基于欧拉多流体法的多相流模型,通过全自动网格生成技术,对二者进行了多维数值模拟。将空化模型应用于数值模拟中,全面分析了喷射压力、喷孔背压、喷孔入口圆角半径和喷孔倾斜角等参数对喷孔内部空化流动及出口流量的影响。结果表明,增大喷射压力容易促使空化的发生,压力较大时,SAC型喷嘴出口流量变化不如VCO型的大;出口压力对空化起到抑制作用,减小出口压力有利于空化的形成,有助于喷孔出口燃油的雾化;喷孔入口圆角半径和倾斜角的增大,使得孔内流动变得更加顺畅,燃油蒸气体积变小,出口流量增加。所以孔内空化效应对缸内喷雾过程尤其是燃油液体射流的初始破碎的影响不容忽视。Cavitation in diesel nozzle orifice is a key factor to the atomization of fuel liquid jet.Nowadays,SAC-type nozzle and VCO-type nozzle are widely used in internal combustion engines.Based on automatically generated unstructured grid,a multidimensional simulation is performed on both orifices using multiphase flow model of Eulerian multi-fluid approach and cavitation model.Injection pressure,back pressure of nozzle,inlet rounded radius of nozzle orifice and inclination angle of nozzle hole,are included in analyzing the cavitating flow in nozzle and mass flow of nozzle exit.The results show that increasing injection pressure can easily lead cavitation.At high injection pressure,the change in mass flow of SAC-type nozzle is less than that of VCO-type nozzle.The outlet pressure of nozzle restrains cavitation and decreasing outlet pressure is helpful to generating fuel bubbles,which is favorable to atomization.Large inlet rounded radius and inclination angle of nozzle orifice make smooth flow of nozzle,generate less vapor bubbles and increase exit mass flow.Study shows that cavitaiton in nozzle orifice can not be neglected in in-cylinder fuel atomization process,especially in primary break-up of liquid jet.

关 键 词：柴油喷嘴 空化 欧拉多流体法 数值模拟 

分 类 号：TK421[动力工程及工程热物理—动力机械及工程]