EGR率控制精度对车用增压直喷柴油机性能的影响

Effect of EGR Rate Control Precision on the Performance of Diesel Engine with Vehicle Turbocharged Direct Injection

开发了一套真空式EGR控制系统和一套步进电机式EGR控制系统,并分别测试了其与发动机匹配后的EGR率万有特性,在此基础之上研究了EGR率控制精度对发动机经济性和排放的影响。研究表明:步进电机式EGR系统的EGR率万有特性平顺,而真空式EGR系统的EGR率万有特性有突变现象,步进电机式EGR系统控制精度优于真空式EGR系统。不同控制精度EGR系统对发动机大负荷区域内的经济性影响不大,但匹配真空式EGR系统的发动机在小负荷区域的油耗偏高;匹配步进电机式EGR系统的发动机中、低速大负荷区的NOX排放较低,但高速大负荷区域的NOX排放较高。

The author presented a set of electronic vacuum controlled EGR system and a set of step motor controlled EGR system and calibrated their EGR rate,which matched the diesel engines respectively,and moreover investigated the effect of EGR rate control precision on fuel economy and exhaust emission based on aforementioned work by using those two EGR systems.The results show that the EGR rate universal characteristics of the step motor controlled EGR system are smoother than that of the vacuum controlled EGR system,which has break points.Therefore,the control precision of step motor controlled EGR system is better than that of vacuum controlled EGR system.The brake specific fuel consumption（BSFC）of the engine that matched electronic vacuum EGR system is higher when the diesel engine runs in light load regions,but the control method of EGR nearly has no effect on BSFC when the diesel engine runs in heavy load regions.The NOX emission of the engine that matched step motor controlled EGR system is higher when operating in high speed and heavy load regions,but lower when operating in high and middle speed and heavy load regions.