Enthalpy of Combustion of Fuels as a Function of Distillate Cut:  Application of an Advanced Distillation Curve Method

Abstract

In previous work, several significant improvements in the measurement of distillation curves for complex fluids were introduced. The modifications to the classical measurement provide for (1) temperature and volume measurements of low uncertainty, (2) temperature control based upon fluid behavior with a model predictive temperature controller, and, most important, (3) a composition-explicit data channel in addition to the temperature-volume relationship that usually comprises the measurement. This latter modification was achieved with a new sampling approach that allows precise qualitative as well as quantitative analyses of each fraction, during the measurement of the distillation curve. In this paper, we utilize the composition-explicit information to characterize distillate cuts in terms of available energy content. This is critical information in the study of real fuels. The measure we use for the fluid energy content is the composite enthalpy of combustion for each component selected for identification in each distillate fraction. As a test system, we present the distillation cuts of two prepared mixtures of n-decane + n-tetradecane. Then, as a further illustration of the approach, we present an analysis of distillate fractions of a 91 antiknock index (AI) gasoline and a 91 AI gasoline with 15% methanol (vol/vol) added.

Properties of a 5050 mixture of jet-A + S-8

“…Simply stated, the distillation curve is a plot of the distillation temperature of the fluid plotted against the volume fraction distilled [6]. We have recently introduced an advanced approach to the measurement of the distillation curve that takes the information content to a much higher level [7][8][9][10][11][12][13][14]. The new metrology provides: C c = C(760 -P a )(273 + T c ), Representative distillation curve data for the three mixtures of Jet-A with S-8, along with data for the starting materials, are presented in Table 5.…”

Relating Complex Fluid Composition and Thermophysical Properties with the Advanced Distillation Curve Approach

“…Along with these data, one withdraws a sample for detailed analysis. This procedure provides access to the detailed composition, energy content [23], corrosivity [24][25][26][27], etc., corresponding to each datum in the grid.…”

“…If the enthalpy of combustion is known (or predictable) for the components of a mixture, the composite enthalpy of combustion of a mixture of these components can be derived (neglecting the enthalpy of mixing). We have demonstrated how this can be applied to the distillate fractions corresponding to the data grid of the distillation curve [23]. It is not necessary to identify all the components of the fraction; a substantial subset of the major constituents is adequate, and the uncertainty caused by the use of a subset is negligible [37][38][39].…”

Equations of State on Demand: Application for Surrogate Fuel Development

“…Instead, we have been successful in the use of a surrogate mixture concept [29][30][31][32][33] that incorporates advanced distillation curve (ADC) measurements [34][35][36][37][38][39][40][41][42][43][44][45] along with thermophysical property data measurements such as density, heat capacity, sound speed, viscosity, and thermal conductivity [46][47][48][49]. The general principle is to use a mixture with a relatively small number of components (usually <15) to represent the behavior of the actual complex fuel.…”