Cummins demonstrates cylinder deactivation technology for meeting low NOx emission standards
22 April 2020
Cummins and Tula Technology, a developer of cylinder deactivation software for passenger cars, announced their collaboration on a technical demonstration of diesel Dynamic Skip Fire (dDSF™). By using dDSF software to control cylinder deactivation, Cummins and Tula said they demonstrated significant reductions in NOx emissions and fuel consumption.
The project started in early 2019 with the goal of optimizing cylinder deactivation strategies for diesel engines, which could result in emission reduction benefits. Advancements through the project are expected to help address future, more stringent NOx regulations, the companies said.
The collaboration work was carried out on a Cummins X15 Efficiency Series 6-cylinder diesel engine. The joint development team modified the engine system to integrate Tula’s Dynamic Skip Fire (DSF®) control algorithms to command combustion or deactivation on a cylinder event basis. On the challenging low-load cycle (LLC) being proposed by the California Air Resources Board, modeling of dDSF technology predicted reductions in tailpipe NOx emissions while simultaneously reducing CO2.
On the HD FTP cycle, dDSF technology modeling predicted NOx reductions of 45%, while simultaneously reducing CO2 by 1.5%. On the LLC cycle, dDSF technology modeling predicted reductions of tailpipe NOx emissions by 66% while reducing CO2 by 4%.
Further NOx reductions may be achievable with the addition of increased conventional thermal management (ICTM), with a reduction of the CO2 benefit. The modeling predicted a combined dDSF+ICTM effect of 55% NOx reduction and a 1% CO2 improvement over the HD FTP. On the LLC cycle, the simulated combined effects resulted in a 70% NOx reduction and a 2% reduction in CO2.
The reduction of tailpipe NOx is achieved primarily by optimized exhaust temperature control, resulting in improved conversion efficiency of the SCR aftertreatment. The technology achieves CO2 reductions through improvements in combustion and reductions in pumping work.
During the recommended strategy for dDSF+ICTM, the engine is operated at less than all cylinders for 55% of the time (HD FTP cycle). Predicted SCR temperatures are improved throughout the cycle, including an increase of 80°C during the critical first 200 s of the FTP cycle.
Cummins and Tula have released their joint paper “Diesel Dynamic Skip Fire (dDSF®): Simultaneous CO2 and NOx Reduction” for the 2020 Vienna Motor Symposium [4704], which presented the performance of dDSF in increasing efficiency and reducing CO2 and NOx. The paper reflected the successful partnership and collaboration between Cummins and Tula in evaluating dDSF for the diesel market.
The companies intend to continue the collaboration with exploring future system optimization and viability to control noise, vibration and harshness (NVH) in commercial vehicle applications by manipulating the firing sequence and cylinder loading.
Source: Cummins