Abstract
It is of great significance to improve the performance of diesel engines by adjusting the intake components and their distribution. In this work, various proportions of exhaust gas recirculation (EGR) gas and oxygen (O(2)) have been introduced to the intake charge of a diesel engine and the effects of different intake components and stratification conditions on pollutant emissions, especially for particles, have been explored. The results show that the introduction of O(2) into the intake charge is beneficial to alleviate the deterioration of particles and hydrocarbon (HC) emissions caused by high EGR rates. Compared with the pure air intake condition, the introduction of moderate O(2) at high EGR rate conditions can simultaneously reduce nitrogen oxides (NO (x) ) and particles, when the intake oxygen content (IOC) is 0.2 and the EGR rate is 20%, the NO (x) and particles are reduced by 45.66% and 66.49%, respectively. It is worth noting that different intake components have a significant impact on the particle size distribution (PSD) of diesel engines. In addition, the in-cylinder O(2) concentration distribution formed by the stratified intake is advantageous for further improving the combined effect of NO (x) , particles and HC emissions relative to the homogeneous intake. At a condition of 0.2 IOC and 20% EGR rate, the NO (x) , particles, and HC emissions are about 8.8%, 14.3%, and 26% lower than that of intake components nonstratification, respectively.