Development of Comprehensive Modal Emissions Model: Operating Under Hot-Stabilized Conditions

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Abstract
A comprehensive modal emission model for light-duty cars and trucks is being developed. More than 300 real-world vehicles are being recruited for in-house dynamometer testing under as-is conditions to provide the foundation for the model. The model is designed to predict second-by-second tailpipe emissions under a variety of driving conditions. The vehicles can be modeled as individual vehicles with properly functioning, deteriorated, or malfunctioning emission control conditions, or as composite vehicles representing different vehicle technology categories. The model is based on a simple parameterized physical approach and consists of six modules that predict engine power, engine speed, air/fuel ratio, fuel use, engine-out emissions, and catalyst pass fraction. When developing the model, four important vehicle operating conditions are considered: cold and warm starts; normal, stoichiometric operation; high-power enrichment; and lean-burn operation. The model concept and the expected input/output requirements of the model are discussed. The general structure of the model also is presented, focusing on emissions for vehicles operating under hot-stabilized conditions. Preliminary results of the model are given, and comparisons are made between the modeled and measurement results for 17 sample vehicles. Preliminary results show good agreement.

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