Optimized In Cylinder NOx Reduction Strategy for Meeting BSVI Emission Limits

The tough emission limits of BSVI norms with very low levels of NOx and PM emissions presents major techno economic challenges for the automobile industry. Combined efforts of pollutants reduction by combustion modification as well as the exhaust after treatment devices could only facilitate to achieve the desired emission targets. selective catalytic reduction technology is a mandatory system which uses ammonia from the aqueous urea solution to react with NOx forming nontoxic by products. The cost spent on aqueous urea solution in addition to the cost of BSVI diesel encounters high operating cost for the vehicle. NOx reduction by SCR too requires adequate quantity of ammonia from the AdBlue. Hence sensible utilization of DEF is essential for reduced running cost of the SCR system. SCR efficiency is higher for higher exhaust temperature and it requires minimum exhaust temperature above which only it operates. For conditions like cold start and low temperature combustion, SCR may not be effective and combustion optimization is the only way to reduce NOx. This article focuses on the reduction of NOx emission of the 2.2 l engine on adjustment of EGR rate and Main injection timing on different operating points on various equivalence ratios. The operating points for optimization were determined by conducting various drive trials on different type of road conditions along with consideration of NEDC. NOx, BSFC, soot and CO were measured and studied thoroughly from richer to leaner fuel-air mixtures. Calibration strategy involved the safe limits of NOx, soot, CO emissions and fuel consumption. Combustion optimization for NOx reduction was done keeping the in mind the consumption of DEF as well as diesel and the cost factor of both. Finally the best fit of strategy for reduced NOx and fuel consumption was arrived ensuring lower operating fuel and DEF cost.