Experimental techniques for the assessment of fuel thermal stability

Two different methods for characterizing the thermal oxidative tendencies of aviation fuels have been developed. A common feature of both methods is that the fuel being tested is passed through a heated tube which is maintained at a constant temperature throughout the test duration. One is a closed-loop system in which the fuel is recirculated continuously for periods of up to 22 h. The other is a single-pass device whereby the test fuel flows only once through the heated tube. These two methods and their relative merits are discussed in some detail, and the extent to which they simulate an actual aircraft fuel system is assessed alongside that of a more established test technique which maintains a constant heat flux through the tube wall and allows the wall temperature to increase continuously throughout the test duration.