基于气助雾化喷射的柴油喷雾特性数值模拟  

Numerical simulation of diesel spray characteristics based on air-assisted atomization injection

作　　者：季昊成 吴昊 杨海青[2] 刘海峰[3] 刘锐 JI Haocheng;WU Hao;YANG Haiqing;LIU Haifeng;LIU Rui(School of Mechanical and Power Engineering,Nanjing Tech University,Nanjing 211816,China;College of Energy and Power Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China;State Key Laboratory of Engines,Tianjin University,Tianjin 300072,China)

机构地区：[1]南京工业大学机械与动力工程学院,南京211816 [2]南京航空航天大学能源与动力学院,南京210016 [3]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《航空动力学报》2022年第6期1284-1294,共11页Journal of Aerospace Power

基　　金：内燃机燃烧学国家重点实验室开放基金(K2020⁃05);国家自然科学基金(51865031);江苏省高等学校自然科学研究项目(20KJB470014)。

摘　　要：为对气助雾化喷射柴油的过程进行数值分析,借助计算流体力学仿真工具Fluent,在不改变喷嘴结构的情况下,建立考虑油气预混腔中柴油喷射过程的三维流体计算模型,研究定容弹内气助雾化喷嘴的柴油/空气两相流喷射过程,并且重点考察喷气压力、环境背压以及燃油温度对气助雾化喷射柴油喷雾特性的影响规律。结果表明:喷气压力对喷雾贯穿距离影响较大,喷气压力由0.65 MPa增大至0.75 MPa后贯穿距离增加12.2%,但柴油索太尔平均直径(SMD)只减小了5.2%,说明在保证燃油SMD处于较好水平时,喷气压力和环境背压绝对压力比值(气相压比)为7.5有利于减少气量消耗;环境背压对喷雾贯穿距离与燃油SMD影响显著,气相压比为1.875时,喷嘴出口处流场基本不会产生超声速气流,气动力降低显著影响了燃油液滴破碎过程,使喷射时间在4 ms时的SMD达到40.7μm;燃油温度对喷雾贯穿距离影响不大,但对燃油SMD影响较大,燃油温度升高后燃油SMD显著减小,323 K对应的SMD比293 K时减小了12.3%,喷射时间在4 ms时的SMD达到14.9μm,燃油蒸发质量分数达到36.93%。To numerically analyse the process of air-assisted atomization for diesel spray,the computational fluid dynamics simulation tool Fluent was applied. Three-dimensional fluid calculation model considering diesel injection process in fuel/air premixing chamber was established without changing the injector structure. The air-assisted injection process of diesel/air two-phase flow was investigated in constant volume chamber. The effects of air injection pressure,ambient backpressure and fuel temperature on diesel spray characteristics were investigated. The results showed that the air injection pressure had a great influence on the spray penetration distance. As the air injection pressure increased from 0. 65 MPa to 0. 75 MPa, the penetration distance increased by 12. 2%,while the Sauter mean diameter(SMD)of diesel only decreased by 5. 2%.When maintaining the SMD of fuel spray at an optimal level,the pressure ratio of 7. 5 was beneficial to reduce the air consumption. Ambient backpressure had significant influence on penetration distance and SMD of fuel spray,as the pressure ratio was 1. 875,the flow field at injector outlet almost did not produce supersonic flow, and the decrease of aerodynamic force significantly affected the breaking process of fuel droplets, making the SMD increase to 40. 7 μm at the injection time of 4 ms. Fuel temperature had little effect on spray penetration distance,while it had a great effect on SMD. The SMD of fuel decreased significantly with the increase of temperature,and the SMD corresponding to 323 K decreased by 12. 3% compared with that of 293 K. At the injection time of 4 ms,the overall SMD of fuel was 14. 9 μm and the evaporated mass fraction of fuel reached 36. 93%.

关 键 词：气助雾化喷嘴 柴油 喷雾特性 索太尔平均直径 贯穿距离 

分 类 号：V233.2[航空宇航科学与技术—航空宇航推进理论与工程] TK401[动力工程及工程热物理—动力机械及工程]