Heavy-duty (HD) diesel engines are the primary propulsion systems in use within the transportation sector and are subjected to stringent oxides of nitrogen (NOx) and particulate matter (PM) emission regulations. The objective of this study is to develop a robust calibration technique to optimize HD diesel engine for performance and emissions to meet current and future emissions standards during certification and real-world operations. In recent years, California - Air Resources Board (C-ARB) has initiated many studies to assess the technology road maps to achieve Ultra-Low NOx emissions for HD diesel applications [1]. Subsequently, there is also a major push for the complex real-world driving emissions as the confirmatory and certification testing procedure in Europe and Asia through the UN-ECE and ISO standards. Such in-use monitoring approaches demand a more advanced and innovative approach to optimize engine controls & calibration to meet the regulated certification levels with minimal fuel penalty.
A robust engine calibration technique was developed using dual-layered multi-objective genetic algorithms (D-MOGA) to locate important engine control parameter settings. Primarily, the study is focused on optimizing fuel consumption while lowering NOx emissions through an optimized thermal management strategy. The study also focuses on using D-MOGA to develop a calibration routine that will perform simultaneous transient cycle calibration for the certification cycle and the vocational drayage operation.
The low-NOx FTP calibration obtained during this study was validated in the engine dynamometer test cell, over the FTP and custom low-load drayage test cycles. Additionally, the 2010 emissions compliant calibration was baselined for performance and emissions over the FTP and modified Near-Dock engine dynamometer test cycles. Baseline calibrations showed a 63% increase in engine-out brake-specific NOx emissions and a proportionate 77% decrease in engine-out soot emissions during off-cycle engine activity, as compared to the FTP cycle. Validation results of the D-MOGA optimized calibration showed a 17% increase in brake-specific NOx emissions over the FTP cycle, compared to baseline calibrations. However, a 50% decrease in engine-out soot emissions and a 200°C increase in peak turbine out exhaust temperatures were observed with no penalties on fuel economy or brake-specific fuel consumption. This resulted in a more aggressive thermal management strategy that incurred little to no penalties in the process. Additionally, engine-out brake-specific soot emissions were also decreased by 50%, resulting in reduced fuel penalties incurred during particulate filter management.
The outcome of this study could play a role in lowering the differences in emissions between certification and real-world engine operations without sacrificing engine performance and fuel consumption.
