Co-Relating Shed Test Results to Permeation Measurement by Recirculation Procedures

When hydrocarbon emissions are measured for conformance testing of a vehicle's fuel and vapor handling systems, the test used is the Sealed Housing Evaporative Determination (SHED) procedure. Flame Ionization Detection (FID) techniques are used for those measurements. During development of individual fuel/emissions systems components, however, recirculation procedures described in SAE J1737 are utilized to determine emissions (adsorbancy measurements of permeation are used). The platform engineer needs a correlation between values out of both procedures and to be able to estimate the emissions of the fuel/emission system of his platform based on the lab values available for the individual components.

The study was done using alcohol-containing fuels. In addition to permeation measurements for 3 different temperatures, an understanding of speciation of the fuel constituents is necessary. This means it has to be known how much of the permeate is pure hydrocarbons and what amount is alcohol (or other fuel components). The results show that the composition of the permeate is different than the composition of the test fuel that was utilized. That difference (measured by the speciation) is a key factor to making the correlation yields usable predictions.

This paper presents a technique to do this correlation for the diurnal and hot soak portion of the SHED procedure.