标题：Effect of intake swirl on combustion performance in an unthrottled spark ignition engine
作者：Zhang, Kaiyu; Chang, Yingjie; Xie, Zongfa; Sun, Tingting; Chen, Fei
作者机构：[Zhang, Kaiyu; Chang, Yingjie; Xie, Zongfa; Sun, Tingting; Chen, Fei] Shandong Univ, Sch Mech Engn, 17923 Jingshi Rd, Jinan 250061, Shandong, Peoples 更多
通讯作者：Xie, ZF;Xie, Zongfa
通讯作者地址：[Xie, ZF]Shandong Univ, Sch Mech Engn, 17923 Jingshi Rd, Jinan 250061, Shandong, Peoples R China.
来源：PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING
关键词：Unthrottled SI engine; Fully Hydraulic Variable Valve System (FHVVS);; helical valve; intake swirl; indicated thermal efficiency
摘要：A Fully Hydraulic Variable Valve System is described in this article which can achieve continuous variation in valve lift, duration, and timing. The system was installed in a four-cylinder port fuel injection spark ignition engine and achieved unthrottled load control through early intake valve closing. The in-cylinder pressure measured experimentally showed that pumping losses of the unthrottled spark ignition engine at 2000r/min and 0.189MPa brake mean effective pressure was reduced by 85.4% compared with the throttled spark ignition engine. However, its slow and unstable combustion reduced the indicated thermal efficiency. Compared with the throttled spark ignition engine, the amount of residual exhaust flowing back into the intake port was greatly reduced at the early stage of the intake process. Consequently, it negatively influenced fuel evaporation and fuel-air mixing processes in the intake port of the port fuel injection spark ignition engine and decreased the flow of in-cylinder gases, which resulted in a low combustion rate. A new centrosymmetric helical valve is proposed in this article to improve the fuel-air mixing and combustion rate of the unthrottled spark ignition engine. The experiments demonstrate that the helical valve can generate a strong intake swirl at small intake valve lift. It helps to increase combustion rate and lower cycle-to-cycle variation, which improves indicated thermal efficiency and fuel economy of the unthrottled spark ignition engine at low load.