MODAL ANALYSIS OF PARTICULATE EMISSIONS FROM CONNECTICUT TRANSIT BUSES FOR LOCAL EMISSIONS MODELING December 2008

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IX 1.0 INTRODUCTION..............................................................................................................1 1.2 LITERATURE REVIEW....................................................................................................................................... 2 1.2.1 Particle Number Emissions from Transit Buses...................................................................................... 2 1.2.2 Uncertainty and Variability in Particle Number Emissions................................................................... 3 1.2.3 Operating Parameters Important for Modeling Diesel Particle Number Emissions ............................. 7 1.2.4 Emission Models for Heavy-duty Diesel Particulate Mass Emissions .................................................... 8 1.2.5 Modal Emissions Models ........................................................................................................................ 9 2.0 RESEARCH OBJECTIVES...........................................................................................11 3.0 RESEARCH METHODS................................................................................................12 3.1 VEHICLES AND ON-BOARD INSTRUMENTATION............................................................................................. 12 3.1.1 Vehicles ................................................................................................................................................. 12 3.1.2 Particle Number Emissions Instrumentation......................................................................................... 12 3.1.3 Horiba Exhaust Emissions System ........................................................................................................ 14 3.1.4 Global Positioning System (GPS) and Time Synchronization............................................................... 14 3.1.5 Engine Diagnostic Scan Tool................................................................................................................ 15 3.1.6 Data Collection Test Route Nomenclature............................................................................................ 15 3.2 DATABASE DEVELOPMENT ............................................................................................................................ 18 3.2.1 Temporal Alignment of Instrument Data............................................................................................... 18 3.2.2 Emissions Rate Calculation .................................................................................................................. 19 3.2.3 Route Definitions and Road Grade ....................................................................................................... 20 3.2.4 Vehicle Specific Power.......................................................................................................................... 21 3.3 DATABASE QUALITY ASSURANCE ................................................................................................................. 21 3.4 DATA ANALYSIS AND MODELING.................................................................................................................. 22 3.4.1 Evaluating Sources of Variability in Onboard Particle Number Concentrations................................. 22 3.4.2 Evaluation of Spatial Relationships ..................................................................................................... 25 4.0 RESULTS AND DISCUSSION ......................................................................................26 4.1 VARIABILITY IN PARTICLE NUMBER CONCENTRATIONS................................................................................ 27 4.1.1 Summary of Variability Analysis........................................................................................................... 36 4.2 VEHICLE OPERATION BY BUS TECHNOLOGY ................................................................................................ 38 4.3 PARTICLE NUMBER EMISSIONS RATE BY VEHICLE TYPE............................................................................... 41 4.4 BUS OPERATION BY ROUTE ........................................................................................................................... 43 4.4.1 Enfield Route Operation ....................................................................................................................... 43 4.4.2 Avon Route Operation........................................................................................................................... 47 4.4.3 Farmington Route Operation ................................................................................................................ 50 4.5 PARTICLE NUMBER EMISSIONS RATE BY ROUTE ........................................................................................... 55 4.6 RELATING PARTICLE EMISSIONS RATES TO OPERATING MODE..................................................................... 58 4.6.1 Vehicle Specific Power and Number Emissions.................................................................................... 59 4.6.2 Vehicle Speed and Number Emissions .................................................................................................. 61 4.6.3 Vehicle Acceleration and Number Emissions........................................................................................ 62 4.7 MODELING PARTICLE EMISSIONS .................................................................................................................. 63 4.8 SPATIAL ANALYSIS OF LAND-USE/TRANSPORTATION/EMISSIONS RATE RELATIONSHIPS.............................. 70 4.9 VALIDATION OF PARTICLE NUMBER EMISSIONS RATE MODAL MODEL........................................................ 75