Experimental study of effects of oxygen concentration on combustion and emissions of diesel engine

Effects of oxygen concentration on combustion and emissions of diesel engine are investigated by experiment. The intake oxygen concentration is controlled by adjusting CO₂. The results show that very low levels of both soot and NO _x emissions can be achieved by modulating the injection pressure, timing, and boost pressure at the low levels of oxygen concentration. However, both CO and HC emissions and fuel consumption distinctly increase at the low levels of oxygen concentration. The results also indicate that NO _x emissions strongly depend on oxygen concentration, while soot emissions strongly depend on injection pressure. Decreasing oxygen concentration is the most effective method to control NO _x emissions. High injection pressure is necessary to reduce smoke emissions. High injection pressure can also decrease the CO and HC emissions and improve engine efficiency. With the increase of intake pressure, both NO _x and smoke emissions decrease. However, it is necessary to use the appropriate intake pressure in order to get the low HC and CO emissions with high efficiency. Supported by the National Natural Science Foundation of China (Grant Nos. 50636040, 50676066)