Browse Publications Technical Papers 2019-26-0270
2019-01-19

Case Study on Thermal Management Strategies for HDD BS VI Exhaust Aftertreatment Performance Using Semi Physical Modelling Approach 2019-26-0270

Selective Catalyst Reduction (SCR) is a key technology in achieving BS VI NOx emission norms in Heavy Duty Diesel (HDD) commercial vehicle segment. Indian automotive industry is on the path of adapting SCR only or SCR + EGR strategy with Cu-Zeolite as the catalyst material, considering stability required during DPF regeneration. Since SCR conversion efficiencies are temperature dependent, it is very crucial to achieve correct temperatures upstream of SCR. This is also critical in order to minimize Urea deposition. In addition, achieving faster light off temperatures for urea dosage in cold WHTC is the most challenging task. Therefore, right thermal management strategy has become a key aspect for catalyst performance and in a way achieving legislative emission norms. Conventional simulation approach to evaluate various strategies are useful but has limitations of performance and emission predictions during concept stage due to requirement of hardware and measurement facility to build the accurate model. Semi physical model has good prediction accuracy for NOX, CO2 and trends of CO, HC & soot at standard and non-standard conditions. This paper focuses on thermal management strategies of HDD engine aftertreatment using semi-physical model for both engine and aftertreatment. Aftertreatment configuration of DOC, DPF and SCR is selected considering six cylinder HD engine. The SCR reaction kinetics, ammonia adsorption and desorption parameters were calibrated with the data from synthetic test bench. Sensitivity of the aftertreatment system evaluated for operating parameters such as light off temperature, NO2/NO ratio etc. Validated aftertreatment models integrated with semi physical 6-cylinder HDD engine model to evaluate steady state as well as transient operating points and validated with base measurement data. Engine model is modified with different thermal management strategies such as Intake, Exhaust throttle valve, Post injection and evaluated for their merits and limitations considering performance and emission parameters. Legislative operating cycles for HDD such as WHSC, Cold WHTC and Hot WHTC were analysed to select best strategy at different operating zone. Semi physical approach has helped in reducing the calibration complexity and lead-time to conclude the hardware selection for thermal management strategy.

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