摘要
汽油发动机双回路冷却系统由于其快速暖机以及减磨的优点,已逐渐被业界认可,但国内对其工程设计及应用尚属于起步阶段,缺乏相应完善的设计理论和方法。为了满足轻型汽车污染物排放限值(中国第六阶段)的要求以某1.5 T直列四缸汽油发动机为研究对象,对机体、缸盖双回路冷却系统进行了研究。首先,在按经典公式计算的基础上,通过燃气侧对机体、缸盖散热量的计算,初步确定了机体、缸盖双回路冷却介质的流量分配比例。其次,通过一维流动传热和基于CFD(computational fluid dynamics,计算流体动力学)的三维联合仿真,确定了最终冷却回路的流量分配。在此基础上,通过一维瞬态流动传热模型仿真对比了单回路和双回路冷却系统在暖机阶段的性能。结果表明:双回路冷却系统中机体的温度比单回路高10℃,缸盖的温度比单回路低9.6℃,双回路冷却可以显著加快发动机的暖机过程,使发动机在冷启动期间的磨损减小。最后,进行了流量分配验证试验和暖机对比试验,结果表明:在暖机过程中,与单回路冷却系统相比,双回路冷却系统可以使机体温度上升更快,活塞与缸套摩擦减小;在此阶段,怠速工况下油耗降低20.2%,HC(碳氢化合物)排放量降低7.58%,常用工况点(2000 r·min^-1,200 kPa)下油耗降低8.5%,HC排放量降低10.03%。研究结果可为发动机冷却系统的设计优化提供参考。
The double-loop cooling system of gasoline engine has been gradually recognized for its rapid warm-up and low friction,however its engineering design and application in China are still in infancy and lack of relevant perfect design theories and methods.In order to meet the requirements of limits for emissions from light-duty vehicles(China 6),the double-loop cooling system of body and cylinder head of 1.5T in-line 4-cylinder gasoline engine was studied.Firstly,based on the calculation by the classical formula,combined with the calculation of the heat dissipations of body and cylinder head calculated through the combustion gas side,the flow distribution ratio of cooling medium of double-loop was preliminarily determined.Secondly,the final flow distribution of the cooling loop was determined by one-dimensional flow heat transfer simulation and three-dimensional co-simulation based on CFD(computational fluid dynamics).On this basis,the performances of single-loop cooling system and double-loop cooling system in the warm-up stage were simulated and compared using one-dimensional transient flow heat transfer model.The simulation results showed that the body temperature under double-loop cooling system was 10℃ higher than that under single-loop,yet the cylinder head temperature was 9.6℃ lower,and the double-loop cooling could significantly accelerate the engine warming-up process,reducing friction of engine during cold start stage.Finally,the flow distribution verification test and the warm-up comparison test were carried out.The results showed that during the warm-up process,compared with the single-loop cooling system,the double-loop cooling system could make the temperature of the engine body rise faster,the friction between piston and cylinder liner decreased.Fuel consumption and HC(hydrocarbon)emissions were reduced by 20.2% and 7.58% respectively at idle speed working condition,8.5% and 10.03% at common operating condition(2000 r·min^-1,200 kPa).The research results can provide reference for the design and o
作者
徐玉梁
陈利国
白杨
王振
刘捷
赵金旋
XU Yu-liang;CHEN Li-guo;BAI Yang;WANG Zhen;LIU Jie;ZHAO Jin-xuan(Internal Combustion Engine Research Institute,Tianjin University,Tianjin 300072,China;School of Mechanical Engineering,Tianjin University,Tianjin 300072,China)
出处
《工程设计学报》
CSCD
北大核心
2020年第5期671-680,共10页
Chinese Journal of Engineering Design
基金
国家自然科学基金面上项目(51776024)。
关键词
冷却系统
双回路
热管理
暖机
仿真
cooling system
double-loop
thermal management
warm up
simulation
