Dual-layered Multi-Objective Genetic Algorithms (D-MOGA): A Robust Solution for Modern Engine Development and Calibrations

Heavy-duty (HD) diesel engines are the primary propulsion systems used within the freight transportation sector and are subjected to stringent emissions regulations. The primary objective of this study is to develop a robust calibration technique for HD engine optimization in order to meet current and future regulated emissions standards during certification cycles and off-cycle vocation activities. Recently, California - Air Resources Board (C-ARB) has also shown interests in controlling off-cycle emissions from vehicles operating in California by funding projects such as the Ultra-Low NOx study by Sharp et. al [1]. Moreover, there is a major push for the complex real-world driving emissions testing protocol as the confirmatory and certification testing procedure in Europe and Asia through the United Nations - Economic Commission for Europe (UN-ECE) and International Organization for Standardization (ISO). This calls for more advanced and innovative approaches to optimize engine operation to meet the regulated certification levels.;A robust engine calibration technique was developed using dual-layered multi-objective genetic algorithms (D-MOGA) to determine necessary engine control parameter settings. The study focused on reducing fuel consumption and lowering oxides of nitrogen (NOx) emissions, while simultaneously increasing exhaust temperatures for thermal management of exhaust after-treatment system. The study also focused on using D-MOGA to develop a calibration routine that simultaneously calibrates engine control parameters for transient certification cycles and vocational drayage operation. Several objective functions and alternate selection techniques for D-MOGA were analyzed to improve the optimality of the D-MOGA results.;The Low-NOx calibration for the Federal Test Procedure (FTP) which was obtained using the simple desirability approach was validated in the engine dynamometer test cell over the FTP and near-dock test cycles. In addition, the 2010 emissions compliant calibration was baselined for performance and emissions over the FTP and custom developed low-load Near-Dock engine dynamometer test cycles. Performance and emissions of the baseline calibrations showed a 63% increase in engine-out brake-specific NOx emissions and a proportionate 77% decrease in engine-out soot emissions over the Near-Dock cycle as compared to the FTP cycle. Engine dynamometer validation results of the Low-NOx FTP cycle calibration developed using D-MOGA, showed a 17% increase brake-specific NOx emissions over the FTP cycle, compared to the baseline calibrations. However, a 50% decrease in engine-out soot emissions and substantial increase in exhaust temperature were observed with no penalties on fuel consumption.;The tools developed in this study can play a role in meeting current and future regulations as well as bridging the gap between emissions during certification and real-world engine operations and eventually could play a vital role in meeting the National Ambient Air Quality Standards (NAAQS) in areas such as the port of Los Angeles, California in the South Coast Air Basin

Characterizing the Variability in Particulate Mass Emissions from Current Model Year Diesel and Natural Gas Engines

The objective of this study is to discern and characterize the factors contributing to the variability in Particulate Matter (PM) mass emissions from current model year diesel and natural gas engines observed during in-use chassis dynamometer testing and compare it with an alternate method of mass measurement involving instantaneous particle size distribution and number count. The study involves the analysis of engine and chassis dynamometer data collected from different engine technologies and chassis dynamometer test cycles in order compare the variability in gravimetric PM mass as well as the PM mass estimated by number-concentration.;PM and oxides of nitrogen (NOx) have been the two most stringently regulated emissions constituents from heavy-duty diesel engines. Current US-EPA 2010 PM regulations, set at 0.01 g/bhp-hr, have forced manufacturers to implement the use of diesel particulate filters (DPF) in order to comply with the regulations. The use of DPF\u27s has resulted in PM mass decreasing by orders of magnitude since 2004, hence laboratory measurement techniques and instrumentation to accurately quantify the true mass of PM emitted from such engines have been posed with a challenge. Also, the widely gained acceptance of heavy-duty natural gas engines, characterized by their low soot combustion, has inevitably resulted in significant measurement variability due to the high volatile organic content in the exhaust.;Particulate matter mass comparisons are performed between PM sampled using the regulated CFR 1065 Methodology and PM number count measurements performed with similar exhaust dilution conditions as employed for gravimetric PM sampling. Particle size distribution and number concentration measurements were performed using the Engine Exhaust Particle SizerRTM (EEPS) spectrometer for transient engine operation and Scanning Mobility Particle SizerRTM (SMPS) spectrometer for steady-state modal tests performed on an engine dynamometer. Additionally, PM mass comparisons are extended to an in-use study in order to compare Not-To-Exceed (NTE) PM emission limits.;Results from this study showed that an effective-density based conversion technique correlated well with gravimetric filter mass for pre-2010 engine technologies without aftertreatment systems, in particular DPFs for diesel fueled vehicles. Gravimetric PM measurements from a natural gas engine resulted in a standard deviation of 3.1 mg/bhp-hr in comparison to mass calculated through particle size distributions, which resulted in a standard deviation of 0.36 mg/bhp-hr. The use of particle size based measurements for in-use PM monitoring resulted in better resolution of PM mass during short, valid NTE windows