Numerical modeling of di diesel engine spray characteristics

Abstract

Air-fuel mixture formation plays a major role in regulating the combustion newlineprocess in diesel engines. This is primarily because of the fact that major portion of newlinethe combustion process is occurring in diffusion flames. During this period the rates newlineof chemical reactions are solely depending on the air-fuel mixture formation rate. The newlineair-fuel mixture formation can be used as a measure that indicates the appropriate newlinedistribution of fuel within the combustion chamber. And the exhaust emission levels newlinecan be used as a measure to indicate the quality of combustion. Though there exist newlinemany factors that regulate the air-fuel mixture formation, initial air swirl, number of newlinenozzle holes and the time of fuel injection are the major factors. Optimizing these newlinethree factors definitely yields appropriate air-fuel mixture formation. newlineIn the present work, a numerical study was carried out on a DI diesel engine to newlinestudy the effect of in-cylinder air swirl, number of nozzle holes and the injection time newlineon spray and combustion as well. Ricardo-Vectis, a 3 dimensional computational fluid newlinedynamics code which works on finite volume method has been used for this purpose. newlineThe available experimental results were taken into account while validating newlinethe model as well as the code. The capability of the code was validated by comparing newlinethe predicted values of in-cylinder pressure and emissions with the available newlineexperimental results. It was found that the predicting capabilities of the code are newlinematching with the experimental results, with acceptable deviations. newlineAn attempt was made to understand the spray behaviour with the help of the newlinespray characteristics like, penetration length, spray cone angle and Sauter mean newlinediameter. In order to understand the quality of combustion, heat release rate, newlinetemperature, NOx and soot were considered. In this attempt, three factors viz., initial newlinexiv newlineair swirl, number of nozzle holes and the time of fuel injection were considered to newlinefind their optimum values that improves the quality of combustion. newlineIn the first a