A NOVEL TEST METHOD FOR FUEL THERMAL STABILITY

IN THE PRACTICAL APPLICATIONS OF HYDROCARBON FUELS IN ADVANCED AIRCRAFT, THE MOST IMPORTANT CONSIDERATION IS TO KNOW UNDER WHAT CIRCUMSTANCES THE FUEL WILL DEGRADE TO THE EXTENT THAT A DEPOSIT IS FORMED. THE DEVELOPMENT OF THIS UNDERSTANDING OF FUEL BEHAVIOR HAS BEEN HAMPERED BY THE LACK OF TECHNIQUES FOR ON-LINE MEASUREMENT OF DEPOSIT FORMATION. THE PHASE I PROPOSAL IS TO DEVELOP AN EXPERIMENTAL SYSTEM FOR MONITORING THE DEPOSIT RATE AND COMPOSITION OF SURFACE DEPOSITS FORMED FROM DEGRADATION OF JET FUEL. THE MONITORING SYSTEM WOULD BE BASED ON A COMBINATION OF FT-IR TRANSMISSION SPECTROSCOPY AND A QUARTZ CRYSTAL MASS (QCM) DETECTOR. THE FT-IR DIAGNOSTICS WOULD INVOLVE THE USE OF A FIBER-OPTIC (F-O) ELEMENT OPERATED IN AN ATTENUATED TOTAL REFLECTANCE (ATR) MODE. THE USE OF FIBER-OPTICS HAS PROVIDED THE POSSIBILITY OF TRANSMITTING THE IR LIGHT THROUGH A PROCESS STREAM UNDER DIFFICULT OPERATING CONDITIONS (HIGH TEMPERATURE, HIGH PRESSURE). ATR SPECTROSCOPY PROVIDES THE POSSIBILITY OF ANALYSES OF HIGHLY ABSORBING MATERIALS BY PROVIDING A REPRODUCIBLE, SHORT PATH LENGTH. THE QCM DETECTOR CAN MEASURE MICROGRAM QUANTITIES OF DEPOSITS AND THUS CAN PROVIDE REAL TIME DATA ON FUEL DEPOSITION. THE PHASE I RESULT WOULD BE THE DEMONSTRATION OF THESE DIAGNOSTIC METHODS FOR MEASURING THE ONSET OF FUEL DEGRADATION AND FOR TESTING ADDITIVES. THE PHASE II PROGRAM WOULD INVOLVE PARALLEL TESTING OF FUEL/ADDITIVE COMBINATIONS IN A LARGER SCALE SYSTEM WHICH MORE CLOSELY SIMULATES THE CONDITIONS IN AN AIRCRAFT FUEL SYSTEM ALONG WITH COMPREHENSIVE FLUID DYNAMIC MODELING TO ESTABLISH THE USEFULNESS OF THE TEST DEVICE FOR OBTAINING FUNDAMENTAL DATA ON FUEL DEGRADATION. THE DEVICE WOULD BE FURTHER IMPROVED AND TESTED IN PHASE II AND A COMMERCIAL PROTOTYPE WOULD BE DEVELOPED, SUITABLE FOR RESEARCH OR QUALITY ASSURANCE APPLICATIONS.