CARB Low NOx Stage 3 Program – Modified Engine Calibration and Hardware Evaluations 2020-01-0318
With the conclusion of the California Air Resources Board (CARB) Stage 1 Ultra-Low NOX program, there continues to be a commitment for identifying potential pathways to demonstrate 0.02 g/bhp-hr NOX emissions. The Stage 1 program focused on achieving the Ultra-Low NOX (ULN) levels on the heavy-duty regulatory cycles utilizing a turbo-compound (TC) engine, which required the integration of novel catalyst technologies and a supplemental heat source. While the aftertreatment configuration provided a potential solution to meet the ULN target, a complicated approach was required to overcome challenges from low temperature exhaust. The Stage 2 program was concerned with the development of a new low load test cycle and evaluating the trade-off between GHG and tailpipe NOx on the Stage 2 ULN solution. The Stage 3 program focuses on both the regulatory cycles and the new low load cycle but leverages a different engine architecture that is more representative of the broader heavy-duty industry to meet the Phase 2 GHG targets and to simplify the ULN aftertreatment solution. As part of this effort, multiple engine hardware technologies were evaluated over steady-state and transient operation to assess the trade-offs between improved exhaust properties, emissions and fuel consumption. This paper reports the findings from the engine hardware evaluations and provides support for selecting cylinder deactivation to carry forward in the program.
Gary D. Neely, Christopher Sharp, Sandesh Rao