An empirical model for estimating evaporative hydrocarbon emissions from canister-equipped vehicles

An empirical model for the estimation of evaporative hydrocarbon emissions from canister-equipped vehicles has been developed from experimental data obtained from repeated tests on a single carbon canister. The model is able to predict canister adsorption and desorption behaviour under different loading and purging conditions and it calculates canister weight and breakthrough emissions for various experimental variables including temperature, mixture concentration and mass flow rate. The model enables the simulation of a full evaporative emission Sealed Housing for Evaporative Determination (SHED) test procedure taking into account vehicle-specific estimations of fuel vapour generation and permeation. Results from measurements conducted on a vehicle equipped with the same canister were used to calibrate the model. Model results were in good agreement with measured evaporative emissions from a number of vehicles.