We use a comprehensive, integrated approach to the study and characterization of liquid and gaseous fuels. Our approach differs depending upon the fluid in question. Pure fluids such as hydrogen pose a different set of challenges than a complex mixture such as diesel fuel or aviation kerosene. Since many fuels are used at high temperatures and pressures, and our measurements often extend to high temperatures and pressures, we next evaluate the thermal decomposition kinetics, usually as a function of temperature and sometimes pressure. This provides guidance as to conditions and residence times that might be tolerated. Following this, we characterize the thermophysical and transport properties of the fuel. This includes the measurement of density (at atmospheric pressure and in the compressed liquid region), the speed of sound, the viscosity, the thermal conductivity and the heat capacity. The vapor liquid equilibrium is approximated by the measurement of the volatility.
Energy is one of the most critical problems facing the United States, with technical, economic and public policy aspects. Decision makers depend on reliable and objective characterization of fuels to evaluate the performance of traditional and alternative liquid and gaseous fuels. Our research group develops state of the art measurement techniques for fuel characterization, and with the resulting data, we develop predictive capability that is needed in all phase of design, from feedstock to engine operation.
Additional Technical Details
We typically begin a study with a detailed chemical analysis of the fuel we intend to study. For a nominally pure fluid, such as hydrogen or perhaps ethanol, the chemical analysis is needed to ensure data quality; measured data are meaningless unless one understands the matrix. For a complex mixture, the analysis provides the starting point by delineating the chemical moieties that are present. Our group has developed extensive analytical techniques, capabilities and databases that are specific to the study of fuels.
Bruno, T.J., Svoronos, P.D.N., CRC Handbook of Basic Tables for Chemical Analysis, Third Edition, CRC Taylor and Francis, 2010.
Thermal Decomposition Kinetics:
We have developed a batch ampoule approach to evaluate the thermal decomposition kinetics that provides (pseudo first order) rate constants, Arrhenius parameters and activation energies for simple and complex fluids. While the immediate application, in house, for these measurements is the support of our other thermophysical property measurements, the measurements are of general usefulness, and are comparable to measurements made by other approaches. We have applied this technique to finished fuels (Jet-A, RP-1, stabilized RP-1), working fluids (pentanes, for parabolic solar reflectors), and fuel components (propylcyclohexane):
Widegren, J.A. Bruno, T.J., 2011. Thermal decomposition kinetics of kerosene-based rocket propellants. 3. RP-2 with varying concentrations of the stabilizing additive 1,2,3,4-tetrahydroquinoline. Energy & Fuels, doi: 10.1021/ef101376k.
We recently developed an advanced method for the measurement of distillation curves to characterize complex fluids. We have applied this to simple hydrocarbons, gasolines, diesel fuels (including renewable fuels), aviation fuels, rocket propellants and even crude oils. The method featuring (1) a composition explicit data channel for each distillate fraction (for both qualitative and quantitative analysis), (2) temperature measurements that are true thermodynamic state points that can be modeled with an equation of state, (3) temperature, volume and pressure measurements of low uncertainty suitable for equation of state development, (4) consistency with a century of historical data, (5) an assessment of the energy content of each distillate fraction, (6) trace chemical analysis of each distillate fraction, and (7) a corrosivity assessment of each distillate fraction. Our method has been adopted by other laboratories in the United States, Canada and Australia, and some of the equipment that is used in the technique is commercialized and sold by Sigma Aldrich. (http://www.sigmaaldrich.com/catalog/
Bruno, T.J., Ott, L.S., Lovestead, T.M., Huber, M.L., 2010. The composition explicit distillation curve technique: relating chemical analysis and physical properties of complex fluids. J. Chromatogr., A1217: 2703-2715.
Bruno, T.J., Ott, L.S., Lovestead, T.M., Huber, M.L., 2010. Relating complex fluid composition and thermophysical properties with the advanced distillation curve approach. Chemical Eng. Tech., 33: 363-376.
The rational development of predictive equations of state, even for complex fluids such as finished fuels, depends upon reliable experimental of low uncertainty. Our group has developed extensive capability to measure fluid density, speed of sound, heat capacity, viscosity and thermal conductivity. All these properties are important in their own right, but achieve synergy when combined with fluid theory, since this allows the development of predictive models, implemented as computer programs, that are then incorporated into all facets of process design and simulation.
contact: Dr. Tom Bruno
Air Force Office of Scientific Research
Air Force Research Laboratory - Wright Patterson AFB
Air Force Research Laboratory - Edwards AFB