高压缩比汽油机分层压燃效果的光学诊断

doi:10.3969/j.issn.1674-8484.2021.03.017

摘要/Abstract

摘要：

对汽油分层压燃燃烧方式进行了光学诊断,研究了缸内直喷(GDI)持续期、喷油时刻及轨压对分层引燃压燃效果影响。在一台光学单缸机上,采用气道喷射预混,缸内直喷辅助火花引燃的方法,分别在0.5、1.2、2.0 ms的3种不同喷油持续期,上止点前曲柄转角CA为40°、50°、60°、80°和100°的5种直喷喷油时刻,以及3.8、10、15 MPa的3种轨压下开展了对比试验。结果表明:高压缩比发动机维持常规气门定时,利用气道喷射预混,缸内直喷辅助火花点火,可以实现分层引燃压燃燃烧。通过合理标定直喷喷油持续期、喷油时刻和轨压,可以提高压燃成功率、提升压燃稳定性并降低碳烟排放。

关键词: 汽油机, 分层压燃, 高压缩比, 光学诊断

Abstract:

An optical diagnostic on charge stratification compression ignition was used to investigate the influences of gasoline direct injection (GDI) duration, timing and rail pressure to charge stratification compression ignition. Based on a single-cylinder optical engine with port injection method to inform pre-mixture and direct injection fuel to induce ignition, some experiments were developed under the conditions at different GDI duration of 0.5, 1.2, and 2 ms, with different timing at crank angles (before top dead center) of 40°, 50°, 60°, 80°, and 100°, and with different rail pressure of 3.8, 10, 15 MPa. The results show that charge stratification compression ignition is realized by adopting high compression ratio, normal valve timing, port injection to inform pre-mixture and direct injection fuel to induce ignition. Success chance of compression combustion is increased, combustion stability is improved, and the emission of soot is reduced by reasonable calibration to GDI duration, timing and rail pressure.

Key words: gasoline engine, charge stratification compression ignition, high compression ratio, optical diagnostics

中图分类号:

TK411

张志永, 高定伟, 赖海鹏, 张彬, 邢化锋. 高压缩比汽油机分层压燃效果的光学诊断[J]. 汽车安全与节能学报, 2021, 12(3): 410-416.

ZHANG Zhiyong, GAO Dingwei, LAI Haipeng, ZHANG Bin, XING Huafeng. Optical diagnostics of charge stratification compression ignition in high compression ratio gasoline engine[J]. Journal of Automotive Safety and Energy, 2021, 12(3): 410-416.

图/表 15

图1 2种不同HCCI燃烧实现方式的技术原理

缸径	79.5 mm
行程	100 mm
压缩比	14
排量	0.5 L
最高转速	3 500 r/min

表1 试验机基本参数

转速	2 000 r/min
平均指示有效压力, IMEP	260 kPa
点火时刻,CA(btdc)	38°
PFI喷油时刻,CA(btdc)	320°
PFI喷射压力	550 kPa
过量空气因数	1.20
冷却水温度	60 ℃
机油温度	60 ℃

表2 试验工况

图2 分层压燃模式下燃烧特征分析

图3 直喷喷油持续期对分层压燃放热率的影响

图4 2 ms喷油持续期连续50个循环的燃烧放热率

图5 1.2 ms喷油持续期连续50个循环的燃烧放热

图6 直喷喷油持续期对压燃成功率的影响

图7 直喷喷油持续期对碳烟生成的影响

图8 直喷喷油时刻对分层压燃放热率的影响

图9 直喷喷油时刻对压燃成功率的影响

图10 直喷喷油时刻对排气温度的影响

图11 直喷喷油时刻对碳烟生成的影响

图12 轨压对分层压燃放热率的影响

图13 轨压对碳烟生成的影响

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