Reduction of soot emissions on optimization of injection quantity adjustment 2019-28-0002
Fuel injection system is a very sensitive structure deciding the optimum quantity of fuel to be injected for combustion process with acceptable accuracy. Learning of fuel quantity with respect to injection type, duration, number of injections requires proper correction values in order to reduce the variation which would result in dissimilar emissions and performance. Deviation of injection quantities are inevitable due to the variations in production tolerance of the injectors. This study focuses on the maximum reduction in deviation of soot emissions with three different sets of injectors statistically deviating from the ideal pilot fuel quantity.
Three sets of injectors deviating from the mean value were chosen and named as Min sample, mean sample and max sample. Min sample was with lower injection quantity and max sample was with higher injection quantity. Engine was tested on dynamometer as per the standards with all the sets of injectors at part loads and the emission parameters were recorded at each load points. Heat release rate was observed at all load points and the corresponding soot emissions were noted. The overall deviation of soot emissions were initially noted for further scope of adjustments in correction code. Correction code was implemented on the pilot injection in order to reduce the variation and continuous iterations were done in order to minimize the variation without affecting the other parameters.
Initially the soot variation between the injectors was observed to be more than 39% with more variation in heat release rate. Although other emissions were observed to be with lesser deviations, initial correction was applied to the injectors in order to reduce the deviations from the mean sample. Pilot Heat release was also monitored continuously at all load points but although few points had very minimum deviations, overall deviations throughout were calculated. At few iterations there were very minimal deviations of soot but other unfavorable emission deviations which was not preferred and further iterations were done concluding with the least deviation of soot ensuring other emissions within acceptable deviations of less than 10%.
Limitations of this study
The optimization of injector quantity corrections were applied for pilot injection quantity alone ensuring the minimal deviation of soot particles. Main injection corrections not applied in this study could be a limitation.