This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 02, 2019 by SAE International in United States
Annotation ability available
Early exhaust valve opening (eEVO) increases the exhaust gas temperature by faster termination of the power stroke and is considered as a potential warm up strategy for diesel engines aftertreatment thermal management. In this study, first, it is shown that when eEVO is applied, the engine main variables such as the boost pressure, exhaust gas recirculation (EGR) and injection (timing and quantity) must be re-calibrated to develop the required torque, avoid exceeding the exhaust temperature limits and keep the air fuel ratio sufficiently high. Then, a two-step procedure is presented to optimize the engine operation after the eEVO system is introduced, using a validated diesel engine model. In the first step, the engine variables are optimized at a constant eEVO shift. In the second step, optimal eEVO trajectories are calculated using Dynamic Programming (DP) for a transient test cycle. The optimized results indicate that with early EVO, the boost pressure should be increased to provide enough cylinder air charge and to maintain the engine torque. External EGR can be reduced due to increased internal EGR while maintaining the same engine out NOx. An optimal zone to maximize temperature benefit with least impact to BSFC has been observed. The study also shows some of the penalties related to eEVO including increased flow pulsation at the air flow sensor location. Finally, with optimal eEVO, a 6.5% - 11% reduction is observed in the light-off time of the selective catalytic reduction (SCR) catalyst and 45% reduction in tailpipe NOx compared to the baseline operation without eEVO.
CitationSrinivas, P. and Salehi, R., "Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up," SAE Technical Paper 2019-01-0584, 2019, https://doi.org/10.4271/2019-01-0584.
- Neely, G., Sarlashkar, J., and Mehta, D., “Diesel Cold-Start Emission Control Research for 2015-2025 LEV III Emissions,” SAE Int. J. Engines 6(2):1009-1020, 2013, doi:10.4271/2013-01-1301.
- Gehrke, S., Kovács, D., Eilts, P., Rempel, A. et al., “Investigation of VVA-Based Exhaust Management Strategies by Means of a HD Single Cylinder Research Engine and Rapid Prototyping Systems,” SAE Int. J. Commer. Veh. 6(1):47-61, 2013, doi:10.4271/2013-01-0587.
- Roberts, L., Magee, M., Shaver, G. et al., “Modeling the Impact of Early Exhaust Valve Opening on Exhaust Aftertreatment Thermal Management and Efficiency for Compression Ignition Engines,” International Journal of Engine Research. 16(6)):773-794, 2014.
- Lancefield, T., Methley, I., Räse, U., and Kuhn, T., “The Application of Variable Event Valve Timing to a Modern Diesel Engine,” SAE Technical Paper 2000-01-1229, 2000.
- Mayer, A., Lutz, T., and Lämmle, C., “Engine Intake throttling for Active Regeneration of Diesel Particle Filters,” SAE Technical Paper 2003-01-0381, 2003.
- Ratzberger, R., Kraxner, T., Pramhas, J., Hadl, K. et al., “Evaluation of Valve Train Variability in Diesel Engines,” SAE Int. J. Engines 8(5):2379-2393, 2015, doi:10.4271/2015-24-2532.
- Culbertson, D., Khair, M., Zhang, S., Tan, J. et al., “The Study of Exhaust Heating to Improve SCR Cold Start Performance,” SAE Int. J. Engines 8(3):1187-1195, 2015, doi:10.4271/2015-01-1027.
- Pfahl, U., Schatz, A., and Konieczny, R., “Advanced Exhaust Gas Thermal Management for Lowest Tailpipe Emissions - Combining Low Emission Engine and Electrically Heated Catalyst,” SAE Technical Paper 2012-01-1090, 2012.
- Ramadhas, A.S. and Xu, H., “Intake Air Heating Strategy to Reduce Cold-Start Emissions from Diesel Engines,” Biofuels 9(3):405-414, 2017.
- Girard, J., Montreuil, C., Kim, J., Cavataio, G. et al., “Technical Advantages of Vanadium SCR Systems for Diesel NOx Control in Emerging Markets,” SAE Int. J. Fuels Lubr. 1(1):488-494, 2009, doi:10.4271/2008-01-1029.
- Lambert, C., Hammerle, R., McGill, R., Khair, M. et al., “Technical Advantages of Urea SCR for Light-Duty and Heavy-Duty Diesel Vehicle Applications,” SAE Technical Paper 2004-01-1292, 2004.
- Fu, H., Chen, X., Shilling, I., and Richardson, S., “A One-Dimensional Model for Heat Transfer in Engine Exhaust Systems,” SAE Technical Paper 2005-01-0696, 2005.
- Rakopoulos, C., Dimaratos, A., Giakoumis, E., and Peckham, M., “Experimental Assessment of Turbocharged Diesel Engine Transient Emissions during Acceleration, Load Change and Starting,” SAE Technical Paper 2010-01-1287, 2010.
- Salehi, R. and Stephanopoulou, A.G., “Optimal Exhaust Valve Opening Control for Fast Aftertreatment Warm Up in Diesel Engines,” submitted to ASME 2018 Dynamic Systems and Control Conference, 2018.