In estimating emissions inventories, it is important to be able to predict the evaporative emissions of the vehicle fleet, and to know the impact of fuel volatility changes. A new relationship has been developed for predicting vehicle evaporative emissions as a function of fuel volatility. A new quantity, vapor generation number Nvp, was defined to indicate the vapor generation potential of a fuel: Nvp = EXP(0.26 RVP) + 0.23 V70, where RVP is the Reid Vapor Pressure of the fuel and V70 is the amount of fuel distilled at 70°C. The first term accounts for the vapor generation from the vehicle fuel tank; the second term accounts for the hot-soak vapor generation from the carburetor and it is equal to zero for fuel-injected cars. The constants in this equation were determined using both mathematical models and experimental data. The average evaporative emissions with a wide variety of fuels were calculated using information from EPA, API, and CRC reports. An excellent correlation (R=0.95) was found between the average evaporative emissions and Nvp.
A New Correlation for Predicting Average Vehicle Evaporative Emissions as a Function of Fuel Volatility
Sae Technical Papers
1988 SAE International Fall Fuels and Lubricants Meeting and Exhibition ; 1988
1988-10-01
Conference paper
English
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