Effects of exhaust gas recirculation in homogeneous charge compression ignition engines

2000 ◽  
Vol 1 (3) ◽  
pp. 269-279 ◽  
Author(s):  
M Nakano ◽  
Y Mandokoro ◽  
S Kubo ◽  
S Yamazaki
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Auto Ignition ◽  
Significant Difference ◽  
Hcci Engines ◽  
Gas Recirculation ◽  
Homogeneous Charge

Ignition control is an important issue in homogeneous charge compression ignition (HCCI) engines, which have the advantages of low NOx emission and high thermal efficiency. In this study, the effect of the exhaust gas recirculation (EGR) on the ignition control of HCCI engines is discussed using an engine cycle simulation in which a homogeneous mixture is assumed. Auto-ignition of 65 per cent iso-octane + 25 per cent toluene + 10 per cent n-heptane, which is used as a fuel to evaluate the characteristics of a gasoline-like fuel, is represented by a detailed reaction model. The dilution by EGR delays the ignition timing when the charged gas temperature is not changed by EGR. The temperature rise of the charged gas promotes auto-ignition. Based on these characteristics, it was suggested that the ignition timing could be controlled by EGR with temperature control, when the amount of fuel supply is constant. This control method can also be applied to control of the air-fuel ratio (A/F) in the cylinder while maintaining the optimum ignition timing. In spite of the difference in the A/F and the EGR ratios, no significant difference was found in the pressure rise rate at combustion and the NOx emission when the ignition timing was the same.

Exhaust gas recirculation stratification to control diesel homogeneous charge compression ignition combustion

2012 ◽  
Vol 13 (5) ◽  
pp. 429-447 ◽  
Author(s):  
Mathieu André ◽  
Bruno Walter ◽  
Gilles Bruneaux ◽  
Fabrice Foucher ◽  
Christine Mounaïm–Rousselle
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Experimental Studies ◽  
Exhaust Gas Recirculation ◽  
Combustion Noise ◽  
Control Technique ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Compression Ignition Combustion ◽  
Gas Recirculation ◽  
Homogeneous Charge

A single-cylinder diesel engine was used to investigate the potential of exhaust gas recirculation dilution stratification as a control technique for homogeneous charge compression ignition combustion with early direct injections. Experimental studies on both all-metal and optically accessible engines were performed to understand the processes involved when exhaust gas recirculation is introduced separately in the intake ports. Laser-induced fluorescence diagnostics were carried out in the optical engine in order to provide fuel and exhaust gas recirculation distributions. The results indicate that depending on the intake configuration, the exhaust gas recirculation stratification can be maintained until late timings corresponding to the combustion event, leading to decreased maxima of heat-release rates, as well as decreased combustion noise levels. This result suggests that exhaust gas recirculation stratification may be used as a control parameter for combustion speed and therefore may contribute to the extension of the homogeneous charge compression ignition operating range. However, although exhaust gas recirculation stratification appears to be an interesting new control technique for homogeneous charge compression ignition combustion, its effect on the combustion was shown to be very sensitive to parameters such as the intake system configuration or the exhaust gas recirculation composition, showing that industrial use of this control technique requires further understanding of the physical phenomena involved.

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