Effects of Intake Components and Stratification on the Particle and Gaseous Emissions of a Diesel Engine

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.

Experimental Study on NOx Reduction of Diesel Engine by EGR Coupled with SCR

“…Cheng et al 26 studied the effect law of EGR on the performance of low-load diesel engine by bench test and found that as the EGR rate increases, the maximum in-cylinder burst pressure and heat release rate decrease and the average in-cylinder temperature decreases; when the EGR rate is low, the smoke increases with the increase of EGR rate, while with the further increase of the EGR rate, the smoke emission decreases and the CO and HC emissions increase rapidly. Zhang et al 27 designed a system in which the EGR gas component enters the cylinder simultaneously with oxygen, and the incoming oxygen with EGR can reduce both NO x and carbon soot emissions from diesel engines.…”