(335ao) Automated Density And Speed Of Sound Measurements Of Aviation Jet Fuels Over A Wide Range Of Temperature And Pressure

Authors: 
Freund, M., University of Hannover
Seelig, H., University of Colorado
Laesecke, A., NIST


Accurate measurements of the p-ρ-T surface of a fluid are necessary for the development of accurate equations of state used to predict the thermophysical properties of the fluid. These types of equations serve as a basis for the design and optimization of systems with wide ranging applications. The United States Department of Defense has a keen interest in developing a generic fuel that could be utilized by the military to power everything from planes to tanks and other ground vehicles. This new fuel would be similar to the current military aviation jet fuel JP-8. The major chemical constituents of JP-8 are nearly identical to those of Jet-A, the most common commercial gas turbine fuel. Both fuels are complex hydrocarbon mixtures whose properties cannot be predicted with sufficient accuracy by models or by simulation. Measurements presented here were carried out as part of an ongoing program to provide the data necessary to formulate equations and populate a database that will facilitate the development of a fuel for the military as described above. For the purpose of this work, three different Jet-A samples and the synthetic fluid S-8, a substitute for JP-8 produced from natural gas by the Fischer-Tropsch process were used to represent possible compositions of a future fuel. Densities measurements covered a temperature range of 233.15 K to 470 K over pressures from atmospheric to 35 MPa. Speeds of sound were obtained at ambient pressure from 278 K to 343 K.

To be more responsive to the demand for high-accuracy data on an increasing number of industrial type fluids, our group at NIST is working to both optimize and broaden its measurement capabilities. As such, we are now able to measure the density of a fluid with an array of automated instruments operating in different ranges. Automation and parallel operation shorten measurement durations significantly. By referencing these measurements to reference data from our traditional state-of-the-art instruments, we achieve the level of accuracy that one expects from NIST. Employing more than one measurement technique is an additional safeguard that prevents systematic errors. Three vibrating-tube instruments and a very high-accuracy two-sinker densimeter constitute a unique measuring capability. The benefits of this will be demonstrated with the results of the jet fuel measurements in the vibrating-tube densimeters. Two of these densimeters measure only at ambient pressure, while the third is capable of measuring to pressures of 68 MPa. Compressed liquid density data from the high-pressure apparatus were extrapolated to atmospheric pressure for comparison with data from the other two instruments. Similarly, results for the fuel additive dimethyl ether from the compressed liquid vibrating-tube and the dual-sinker densimeters are presented for comparison.