Search Results

Modeling tailpipe NOx emissions has always been difficult due to the complexity of the numerous factors involved in the catalytic conversion of the pollutant. Most emissions modeling has been based on steady state driving. A parameterized algebraic model for second-by-second tailpipe emissions of NOx for a composite Tier 1 car is presented employing data from the Federal Test Procedure Revision Project (FTPRP). Calculating fuel rate from measured engine out values, the catalytic converter is physically modeled based on the fuel rate history and a few fitted parameters. Under certain conditions, the changes in fuel rate are related to trends in the air to fuel ratio. The model accurately predicts the time dependence of hot stabilized tailpipe NOx emissions in the FTP bag 3 and US06 driving cycles. Modeling of low power driving, as in bag 2, is not as successful.

Simulation models for second-by-second fuel rate, and engine-out and tailpipe emissions of CO, HC, and NOx from a “composite” car in hot engine and catalyst conditions are presented and tested using Federal Test Procedure Revision Project (FTPRP) data from 15 1991-1994 cars. The models are constructed as a combination of simple science and curve fitting to the FTPRP data. The models are preliminary, the simplest models being presented to illustrate how much can be predicted with very few parameters. Fuel rate and engine out emissions of all three pollutants are accurately predicted. The tailpipe emissions models are only moderately successful, largely because we are only moderately successful in predicting catalyst pass fractions during low power driving. Nevertheless, the composite car shows regular emissions behavior, and these are modeled effectively.