| 马帅营，刘方杰，王鑫，杜慧勇，徐斌.冷、热EGR对柴油机性能、燃烧及排放特性的影响[J].内燃机工程,2017,38(4):33-40. |
| Effects of Cold and Hot EGR on Diesel Engine Performance, Combustion and Emissions |
| DOI： |
| Key Words:diesel engine cold EGR hot EGR combustion emissions |
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| Abstract:To effectively improve the emissions of a diesel engine without reducing its performance in power and fuel economy, the effects of cold and hot EGR on engine performance, combustion and emissions characteristics were experimentally studied. The experiment was conducted on a four-cylinder diesel engine at three different loads of 6,12 and 24 mg of fuel injected a cycle. The three loads hereinafter are temporarily referred to as low, medium and high loads. The experimental results show that the introduction of EGR can reduce the fresh air inflow, extend the ignition delay and slow down the heat release rate, thus reducing the cylinder pressure rise rate. The hot EGR, on the one hand, decreases HC emission effectively and increases the thermal efficiency at the low load due to its heating intake air; on the other hand, it obviously reduces the thermal efficiency at the high load with high EGR rate because of lower excess air coefficient. The effect of the hot EGR on reducing the maximum pressure rise rate is smaller than that of the cold EGR. With the increase of EGR rate, NOx emission decreases significantly at the three different loads, and soot emission keeps small at the low and medium loads, but increases quickly at the high load with high EGR rate, requiring a trade-off between NOx and soot. The cold EGR, however, can effectively ease this requirement due to its slow increase in soot emission. The thermal efficiency and emissions at the three loads being considered, the hot EGR is appropriate at the low load to improve thermal efficiency, and the cold EGR is more suitable at the high load to maintain high thermal efficiency and reduce the excessive pressure rise rate. |
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