SOME STUDIES ON ENGINE COMBUSTION, EMISSION, AND SPRAY CHARACTERISTICS OF A CRDI DIESEL ENGINE WITH VARIABLE NOZZLE GEOMETRY USING ANSYS

Abstract

The present study aims to investigate the effect on combustion, emission, and spray characteristics with the variation of the nozzle hole diameters (NHD) in a diesel engine. For this a CFD 3D model is developed for a four stroke diesel engine fueled with neat diesel and three different NHD, i.e., 0.20 mm, 0.26 mm, and, 0.30 mm. The CFD 3D models were effectively able to predict the turbulence and turbulent-flame propagation interaction, chemistry involved in combustion processes, and the dissociation and reassociation of chemical species. For the model validation, the combustion characteristics of the CRDI-VCR engine are used. The validation results showed good compatibility having the relative error within the range. The analysis showed that increasing the nozzle hole diameter resulted in the decrease of the in-cylinder pressure by about 8.31% and 31.93%, respectively, for 0.26 mm and 0.30 mm diameter compared to 0.20 mm. The AHRR also showed a similar trend with a decrease of about 11.82% and 42.18%, respectively, for 0.26 mm and 0.30 mm diameter as compared to 0.20 mm. Subsequently, the increase in nozzle diameter showed an increase in HC and CO emissions but a decrease in NOx emissions. The CO emissions increase by about 0.65% and 5.08% and HC emissions increase by about 29.90% and 60.13% respectively for 0.26 mm and 0.30 mm diameter compared to 0.20 mm. viii While the NOx emission reduces by about 41.18% and 70.58% respectively for 0.26 mm and 0.30 mm diameter as compared to 0.20 mm. The effect of different nozzle diameters on spray characteristics is analyzed and verified from previous studies. The increase in nozzle diameter showed an increase in liquid penetration length, breakup length, and SMD. Also, the present study shows the possibilities of the CFD models for the simulation of engines employing different fuels and operative conditions.