Atkinson循环发动机性能改进研究

A Study on the Performance Improvement of Atkinson Cycle Engine

本文中利用理论计算、结构及参数改进和试验标定相结合的方法,将某自然吸气Otto循环汽油机改为Atkinson循环混合动力发动机。首先通过减少活塞顶部凹坑容积将压缩比从10.5提高到13以克服Atkinson循环中由于进气门晚关所带来的有效压缩比的降低;然后利用AVL Excite Timing Drive软件重新设计了满足Atkinson循环要求的进、排气凸轮型线;最后通过发动机台架试验标定了Atkinson循环发动机万有特性下的过量空气系数、配气相位和点火正时等参数。试验结果表明:在保证动力性满足要求的前提下,改型后Atkinson循环发动机的燃油消耗率在整体上比原Otto循环发动机低得多,尤其在中低转速中大负荷时。另外,改型后Atkinson循环发动机的低油耗区域范围比原Otto循环发动机大得多,且低油耗区向低转速和较小负荷区域移动。改型后的Atkinson循环发动机最低燃油消耗率由原来的250g/(kW·h)降低到234.5g/(kW·h),达到了目标要求。

In this paper,an Otto cycle gasoline engine is converted to an Atkinson cycle engine for hybrid electric vehicles with a method combining theoretical calculation,structure and parameters modification and experi-mental calibration. First of al l,compression ratio （CR） is increased from 10. 5 to 13 by reducing the volume of re-cess in piston crown for compensating the effective CR drop caused by the delayed close of induction valve in Atkin-son cycle. Then,both intake and exhaust cam profiles are redesigned using AVL Excite Timing Drive software to meet the requirements of modified Atkinson cycle engine. Finally,parameters such as excess air coefficient,valve timing and ignition timing in the universal characteristics map of Atkinson cycle engine are calibrated by engine bench tests. Test results show that on the premise of meeting power performance requirements,the overall specific fuel consumption of modified Atkinson cycle engine is much lower than that of original Otto cycle engine in particular in medium-low speed and medium-high load regions. In addition,the low-fuel consumption region of modified Atkin-son cycle engine is much larger than that of original Otto cycle engine,with its location moving toward low-speed / low-load area. The minimum brake specific fuel consumption is reduced from 250g/（kW·h） in original Otto cycle engine to 234. 5g/（kW· h） in modified Atkinson cycle engine,meeting the objective requirements.