Experimental Investigation of Combustion and Emission Characteristics of Various Multi-Stage Injection Control Strategies Under the Highest NOx Formation Condition at Single-Injection Timings in a Single-Cylinder Diesel Engine

摘要

The purpose of this study was to experimentally analyze the effect of the distribution and quantity of fuel injection on the combustion and emission characteristics by applying various multi-stage injection strategies in single-fuel-injection timing, where the highest NOx (Nitrogen oxides) emission was formed. In the single-fuel-injection timing experiment, NOx emission was found to be the most emitted in BTDC (Before Top Dead Center) 20 CA (Crank angle). The various multi-stage injection strategies were categorized into double-, triple-, and quadruple-fuel-injection strategies considering the fuel quantity distribution conditions. It was revealed that as the main injection timing moved towards TDC (Top Dead Center), the IMEP (Indicated Mean Effective Pressure) representing the combustion performance was higher in the various multi-stage injection strategy experiments. IMEP showed the highest value D1 strategy in various multi-fuel-injection strategies, and showed 24.3% improvement compared to the single-fuel-injection strategy (BTDC 20 CA). The lower O_2 concentration level in the exhaust gas, the lower CO (Carbon monoxide) emission, and the CO_2 (Carbon dioxide) emission showed results opposite those of the O_2 concentration level. The NOx emission decreased as a result of the application of the multi-stage injection strategies at the injection timing where the highest NOx was formed. In particular, a remarkable NOx emission reduction of 70.2% was observed in the Q4 strategy. In this research, the injection strategy that showed the greatest influence on NOx emission suppression was identified as the split injection strategy (D4, T4, and Q4), which divides the fuel amount evenly.