An improved methodology for determining threshold sooting indices from smoke point lamps

The ASTM D1322 smoke point test has been used for many years as a quick, convenient and easy way to characterize the sooting propensity of aviation fuels. Attempts to apply the same procedure to hydrocarbons in general have been less successful, since for highly sooting fuels the low smoke point makes it very difficult to obtain values with adequate reproducibility. This work describes an adapted version of the test which is usually much more reproducible than the ASTM method, particularly in the case of highly sooting fuels; typically halving the experimental error. The only additional equipment required is an analytical balance of 0.1 mg precision and a PC, together with some modifications to the ASTM D1322 burner which can be carried out in most engineering workshops. The alternative test is based on the fuel uptake rate and image analysis, rather than the height of the flame. An inflexion point is observed when plotting the flame height against fuel uptake rate and is suggested as a reference point to calculate the threshold sooting index (TSI). Results show an improvement in the reproducibility of the observations and a decrease in the error associated with the TSI calculation.