轻型柴油机EGR与喷油正时的协同性能研究

Study on Synergic Performance of EGR and Injection Timing of a Light Duty Diesel Engine

以一台高压共轨轻型柴油机为样机,研究废气再循环(exhaust gas recirculation,EGR)和喷油正时协同作用对发动机燃烧特性、燃油消耗率、氮氧化物(NOx)和HC排放的影响。研究结果表明:随着EGR率增大,缸内最大压力有所下降,瞬时放热率峰值有所减小。随着喷油提前角增加,缸内最大压力增大,瞬时放热率峰值先增大后减小。EGR率与缸内最大压力降幅、瞬时放热率峰值降幅均具有较好的线性关系。随着EGR率的增大和喷油提前角的减小,NOx排放降低,燃油耗增加,而且存在一个最佳的EGR率和喷油提前角的组合区域使HC排放达到最低。为了实现降低NOx排放的同时有效控制燃油消耗率和避免HC排放升高,低负荷时选择高EGR率并结合大喷油提前角的控制策略;中等负荷时选择适中EGR率结合适中喷油提前角的控制策略。

The effect of exhaust gas recirculation （EGR） and injection timing on the combustion char- acteristics, fuel consumption, as well as NOx and HC emissions of a high-pressure common rail light duty diesel engine was studied. The results show that the maximum cylinder pressure drops and the peak value of instantaneous heat-release rate decreases with the increase of EGR rate. With the increase of injection ad- vance angle, the maximum cylinder pressure increases, and the peak value of instantaneous heat-release rate increases first and then decreases. Both declines of the maximum cylinder pressure and the peak value of in- stantaneous heat-release rate have good linear relationships with the EGR rate. With the increase of EGR rate and decrease of injection advance angle, the NOx emission decreases and the fuel consumption increases, while there is an optimal combination of EGR rate and injection advance angle which can lead to the lowest HC emission. In order to reach lower NOx emission, while effectively control fuel consumption and HC emis- sion, a high EGR rate together with a large injection advance angle is suitable at low engine load, and moder- ate EGR rate combined with moderate injection advance angle is ideal at medium engine load.