Effects of EGR rate and excess air ratio on the combustion characteristics of compressed natural gas engine

Author

Yu Xiao-cao ; Liu Zhong-chang ; Wang Zhong-shu ; Dou Hui-li

Author_Institution

State Key Lab. of Automobile Simulation & Control, Jilin Univ., Changchun, China

fYear

2011

fDate

16-18 Dec. 2011

Firstpage

1177

Lastpage

1180

Abstract

The influence of EGR (exhaust gas recirculation) rate and excess air ratio (λ) on the combustion and emissions of a twofold dilution compressed natural gas (CNG) engine CA6SE3-21E4N were investigated experimentally to solve the limited decreasing-ability on NO_x emissions with air dilution. The results show that as EGR rate and λ increase, the peak of cylinder pressure and heat release rate decrease and delay, the heat release centroids and the start of combustion move backward, the main combustion duration becomes longer and then the flame propagation velocity slows down. The cyclic variations intensify versus the EGR rate and λ increase. With smaller λ than that of air dilution under equivalent NO_x emission levels, the twofold dilution makes the engine operating more stably. Considering the trade-off between NO_x emissions and fuel economy, values as optimal control point can be obtained under 1750r/min, 75% load conditions, namely, λ is 1.35, EGR rate is 7%.

Keywords

air pollution; combustion; exhaust systems; flames; fuel economy; internal combustion engines; CNG engine CA6SE3-21E4N; EGR rate; NO_x emission; air dilution; combustion characteristic; compressed natural gas engine; cyclic variation intensify; cylinder pressure; excess air ratio; exhaust gas recirculation rate; flame propagation velocity; fuel economy; heat release centroid; heat release rate; optimal control point; twofold dilution; Combustion; Engines; Fuel economy; Heating; Natural gas; Valves; CNG engine; EGR rate; NOx emissions Introduction; combustion; excess air ratio; twofold dilution;

fLanguage

English

Publisher

ieee

Conference_Titel

Transportation, Mechanical, and Electrical Engineering (TMEE), 2011 International Conference on

Conference_Location

Changchun

Print_ISBN

978-1-4577-1700-0

Type

conf

DOI

10.1109/TMEE.2011.6199415

Filename

6199415