Partially Premixed Combustion (PPC) for low loadconditions in marine engines using computationaland experimental techniques

Diesel Engine has been the most powerful and relevant source of power in the automobile industryfor decades due to their excellent performance, efficiency and power. On the contrary, there arenumerous environmental issues of the diesel engines hampering the environment. It has been agreat challenge for the researchers and scientists to minimize these issues. In the recent years, severalstrategies have been introduced to eradicate the emissions of the diesel engines. Among them,Partially Premixed Combustion (PPC) is one of the most emerging and reliable strategies. PPC is acompression ignited combustion process in which ignition delay is controlled. PPC is intended toendow with better combustion with low soot and NOx emission.The engine used in the present study is a single-cylinder research engine, installed in Aalto UniversityInternal Combustion Engine Laboratory with the bore diameter of 200 mm. The thesis presentsthe validation of the measurement data with the simulated cases followed by the study of the sprayimpingement and fuel vapor mixing in PPC mode for different injection timing. A detailed study ofthe correlation of early injection with the fuel vapor distribution and wall impingement has beenmade.The simulations are carried out with the commercial CFD software STAR CD. Different injectionparameters have been considered and taken into an account to lower the wall impingement and toproduce better air-fuel mixing with the purpose of good combustion and reduction of the emissions.The result of the penetration length of the spray and the fuel vapor distribution for different earlyinjection cases have been illustrated in the study. Comparisons of different thermodynamic propertiesand spray analysis for different injection timing have been very clearly illustrated to get insightof effect of early injection. The parameters like injection timing, injection period, injection pressure,inclusion angle of the spray have an influence the combustion process in PPC mode. Extensivestudy has been made for each of these parameters to better understand their effects in the combustionprocess. Different split injection profiles have been implemented for the study of better fuelvapor distribution in the combustion chamber.The final part of the thesis includes the study of the combustion and implementation of EGR tocontrol the temperature so as to get more prolonged ignition delay to accompany the PPC strategyfor standard piston top and deep bowl piston top. With the injection optimization and implementationof EGR, NOx has been reduced by around 44%, CO by 60% and Soot by 66% in the standardpiston top. The piston optimization resulted in more promising result with 58% reduction in NOx,55% reduction in CO and 67% reduction in Soot. In both cases the percentage of fuel burnt wasincreased by around 8%