Effect of hydraulic flow rate, injection timing, and exhaust gas recirculation on particulate and gaseous emissions in a light-duty diesel engine

Nozzle hydraulic flow rate is a critical parameter that affects the combustion process and plays a vital role in the production of emissions from a diesel engine. In this study, injection characteristics, such as normalized injection rate and spray tip penetration, were analyzed for different hydraulic flow rate injectors with the help of spray experiments. To further investigate the effects of hydraulic flow rate on engine-out particulate and gaseous emissions, engine experiments were performed for different values of hydraulic flow rate in multiple injectors. Various operating conditions and loading configurations were examined, and the effects of varying start of injection and exhaust gas recirculation rates for different hydraulic flow rates were analyzed. A separate Pegasor Particle Sensor (PPS-M) sensor was used to measure and collect data on the particle number, and an analysis was conducted to investigate the relation of particle number with hydraulic flow rate, injection timing, and exhaust gas recirculation rate. Results of the spray experiment exhibited a decreasing injection duration and increasing spray tip penetration with increasing hydraulic flow rate. Effect of hydraulic flow rate on combustion and emission characteristics were analyzed from engine experiment results. Least ignition delay was achieved using a smaller hole diameter, retarded injection timing, and lowest EGR%. Higher hydraulic flow rate with retarded injection timing and higher EGR% helped in reduction of NOx emissions and brake-specific fuel consumption, but particulate emissions were increased. Best particulate matter-NOx trade-off was achieved with lowest hydraulic flow rate.