MONITORING JET FUEL THERMAL-STABILITY USING A QUARTZ-CRYSTAL MICROBALANCE

Thermal stability studies of aviation fuels are hindered by the inadeq uacy of current instrumentation in providing quantitative, in situ mea surements of the rates of solid deposition on contacted surfaces. This paper reports the development of a test system that utilizes a quartz crystal microbalance to make in situ measurements of minute amounts o f solids that deposit on the quartz crystal when a liquid fuel is ther mally degraded. The quartz crystal microbalance jet fuel test system ( QCM-JFTS) was developed in response to a need for quantitative informa tion at temperature conditions representative of actual aviation fuel systems with which to develop mathematical models for predicting fuel thermal degradation and solids deposition. This bench-top system has a resolution of better than 0.3 mug/cm2 with good reproducibility and a ccuracy. Data on deposition rates in the temperature range of 125-200- degrees-C are obtained on three aviation fuels and simple global Arrhe nius-type models formulated which demonstrate how the system can be us ed in model development. Additionally, the system can be used to obtai n viscosity-density data on the fuels. Data obtained from the QCM-JFTS on a model hydrocarbon compound and on a Jet A fuel compare favorably with literature values. The data demonstrate the potential for this s ystem to be used in various aspects of aviation fuel thermal stability investigations.