Experimental study on effects of exhaust gas recirculation on diesel nitrogen oxides and particulate emissions

Exhaust gas recirculation, boost and injection pressure are key parameters affecting diesel low temperature combustion. This paper investigates the effects of EGR on the nitrogen oxides and particulate emissions. The study shows that with the increase of EGR rate, the proportion of NO shows a decreasing and then increasing while those of NO2 and N2O give an opposite trend. The proportion of N2O is low with maximum value about 1%. The maximum proportion of NO2 and NO corresponds to the same EGR rate. With the increase of boost pressure, the peak proportion of NO2 increases and its corresponding EGR rate also increases. At boost pressure of 0.24 MPa, the proportion of NO2 is 60%. When EGR rate is increased to the point where soot emission increases sharply, particulate conglomeration will occur, and its concentration decreases but diameter increases. Higher injection pressure can decrease the particulate emission, but the mechanism is different at different EGR rates.