Donald K. Minus

THERMAL STABILIZING TENDENCIES OF HYDROGEN DONOR COMPOUNDS IN JP-8+100 FUEL

The present study describes an ongoing assessment of hydrogen donor (H-donor) compounds and compounds with similar chemical characteristics (decahydroquinoline and cyclodecane) as thermal stabilizers in JP-8+100 fuel. Decalin (a mixture of stereo-isomers (cis- and tmns-) of bicyclo[4.4.0] decane) and 1,2,3,4-tetrahydroquinolme (THQ) were evaluated at various concentrations in JF-8+100 fuel and stressed to temperatures up to 600°C for six hours in a flowing reactor system. Additionally, cisdecalin and tram+decalin, are assessed individually to determine if their thermal stability activities in a static reactor’ are correlatable to a flowing system, and to compare with the performsnce of decslin. The thermal oxidative and pyrolytic deposition for all fuel/additives mixtures, the conversion percentages and composition of the stressed fuel’s gaseous and liquid products are reported.

Assessment of radical stabilizing additives for JP-8 fuel

Fuel additives to reduce thermal decomposition of JP-8 fuel in the pyrolytic regime were evaluated. Chemical compounds with abstractable hydrogen structures were added to JP-8 at 2.5 % wt concentrations, and tested at 5.2 MPa (750 psi) in a flowing reactor with fuel exit temperatures up to 600 C (1112 F). The most notable results of the present effort are the dramatic reduction in pyrolytic deposition and fuel conversion rate observed for 1,2,3,4 tetrahydroquinoline (THQ). Unfortunately, results also show that THQ, as well as most additives considered, increased the thermal oxidative deposition to some degree. In addition to pyrolytic deposition, the gaseous and liquid composition of the stressed fuel, the conversion rates and thermal oxidative deposition for all additives are reported.

Studies of decalin as a suppressor of pyrolytic deposits in JP-8+100

Decalin isomers, cisand tram-, and a 46% cis-154% trans-decalin mixture (commercial decalin) are studied as suppressors of pyrolytic deposits in JP-8+100 at elevated temperatures. The additives are evaluated at various concentrations in a single. tube reactor system, with exit fuel temperatures to 540°C for a period of 20 hours. Test results demonstrate that at 54O’C only moderate improvements can be obtained with decalin. At these temperatures the decalin isomers are still thermally stable, and hydrogen donation reactions do not appear to occur, or proceed very slowly. Commercial decalin was the only additive to have a moderate effect by reducing pyrolytic deposits by 25 30% when added at 1.0% w/w concentration. Negligible effects with the additives at the 0.05% w/w level were observed.

Hydrogen Donors: Thermal Stabilizers for JP-8+100 at High Temperatures

The effectiveness of hydrogen donor compounds as additives to reduce pyrolytic deposition in JP-8+100 at high temperatures was assessed. Decalin and 1,2,3,4 tetrahydroquinoline (THQ) were added to JP-8+100 at 0.5% (decalin only), 1.0 and 2.5% w/w concentrations and tested in a flow reactor at a fuel exit temperature of 600°C at 5.2 MPa. Measurements of carbon deposits along the tube and gas chromatography/mass spectrometry (GC/MS) analysis of the stressed and unstressed liquid fuel were used to assess effectiveness of the additive, and the degree of fuel decomposition. Additionally, liquid-to-gas conversion was determined, and the composition of the gas was determined via GC. Experimental results show significant reductions in pyrolytic deposition in JP-8+100 with the additives relative to the baseline fuel. Tests with decalin showed negligible effects on thermal oxidative deposits, while THQ produced significant increases in thermal oxidative deposits. The effects of the additives on fuel thermal decomposition and conversion rates are also discussed.Copyright

A Statistical Approach to Estimating the Compatibility of Alternative Fuels with Materials used in Seals and Sealants

‡§ In this study a method of statistically comparing the volume swell behavior of selected materials in representative JP-8s and alternative fuels is described. This approach is based on obtaining volume swell data is a set of reference JP-8s and the alternative fuel. The overlap in the 90% prediction intervals is then used as a measure of the comparability, and by extension the degree of compatibility, between ‘typical’ JP-8 and the alternative fuel. In the specific case examined here the alternative fuel is a 50% v/v blend of JP-8 and a Fischer-Tropsch fuel. The results of the statistical analysis showed that in a arbitrarily blended JP-8 fuel there is greater than 50% chance that this fuel would exhibit volume swell behavior that is within the range of ‘typical’ low-aromatic JP-8s. From this it was concluded that the chances of an acute failure of O-ring seals and sealants with a 50% JP-8/FT fuel blend was low and there was no compelling evidence in the data that there was a significant likelihood of an acute sealing failure resulting from the use of this blend.