Experimental study of intake air temperature effects on NOx and soot emissions in a direct injection diesel engine

Recently, NOx and PM emissions of diesel engine are regarded as a source of air pollution. And there is a global trend to enforce more stringent regulations on these exhaust gas. Therefore, several technologies have been progressively introduced in the last few decades for the reduction of NOx and PM emissions. The goal of this paper is to investigate the effect of intake air temperature on exhaust emissions in a HSDI diesel engine. This paper focuses on simultaneous reduction of NOx and PM emissions in the low intake air temperature. Experimental investigations were carried out on a 2.9L common-rail direct injection diesel engine equipped with HP (high pressure) EGR line. The experiment was conducted for one operating point, engine speed 1400rpm and IMEP 4bar, while intake air temperature was varied. Intake air temperature was controlled by intercooler and EGR cooler which were adjusted by separate cooling loop. As a result of this experiment, the decrease of intake air temperature reduced the NOx and PM emissions simultaneously through the decrease of mean temperature in cylinder and the increase of premixed period, respectively. Moreover, when intake air temperature was reduced, indicated specific fuel consumption (ISFC) was improved, due to increase of density of intake air entrained in the cylinder. On the other hand, HC and CO emissions were increased while temperature of intake air decreased. In addition, at a given intake condition, the effects of injection strategies on emissions were analyzed. Copyright �� 2012 by the Japan Society of Mechanical Engineers