Generation of Comprehensive Surrogate Kinetic Models and Validation Databases for Simulating Large Molecular Weight Hydrocarbon Fuels

Abstract

This multi-university research initiative investigated "surrogate fuel" mixture methodology detailed kinetic models for representing fully prevaporized chemical kinetic/transport global combustion properties of real fuels. Concepts by which surrogate mixtures of a small number of molecular class components would emulate the global combustion properties of each specific real fuel were developed and tested experimentally by comparing surrogate mixture and real fuel behavior in a wide variety of fundamental combustion venues, including: high pressure reflected shock tube ignition delay, rapid compression machine ignition, variable pressure flow reactor reactivity/species time history, high pressure pulsed shock tube speciation, laminar premixed burning rate and strained extinction, laminar counter-flow, strained-extinction configurations, and laminar co-annular diffusive soot extinction configurations. Matching the "real fuel combustion property targets" of hydrogen/carbon molar ratio (H/C), derived cetane number (DCN), threshold sooting index (TSI), and average mean molecular weight (MW ave) of mixtures with those of the real fuel was shown to result in nearly identical global combustion behavior of the real fuel and the surrogate. Methodologies for determining combustion property targets and creating matching surrogate mixtures were demonstrated. Mixtures of surrogate components that had nearly identical combustion property targets were found to have nearly the same distribution of key (CH 2 , CH 3 , benzyl) chemical functional groups. Experimental data for surrogate components were collected from each venue, and vapor phase transport data for components and reaction intermediates were determined created. Data were utilized to test and construct detailed and reduced kinetic models for surrogate components and their mixtures. Models taken from the literature (n-decane and n-dodecane, and iso-octane) were further modified and new models were produced for toluene, n-propyl benzene, and 1,3,5 trimethyl benzene. Model reduction techniques were developed and applied to permit comparisons of predictions with flame data for burning rate and extinction. Approaches that would improve the efficiency of numerical computations were also investigated. Assimilation of physical property considerations within the context of simultaneously emulating chemical properties was also considered.

Chemical kinetic and combustion characteristics of transportation fuels

“…It is interesting to note that the formulated surrogate did not replicate the molecular class composition of the subject real fuel. The investigation on jet fuels noted above [192] offers some further insights on this result. Dryer and co-workers developed an a priori methodology to formulate surrogate mixtures for vapor phase combustion, requiring only limited knowledge of the molecular class composition of the specific real fuel.…”

“…Here remarks, are limited to brief commentary on the state of the field from a personal perspective gained from involvement in surrogate fuel work beginning prior to 2007 [192] and driven by an even longer term fascination with engineering applications [193]. A first pragmatic observation is that combustion-related behavioral aspects of a real fuel and another fuel are best quantitatively compared to each other by actual experiments involving each over a wide range of venues, from fundamental to applied scale.…”

Emulating the Combustion Behavior of Real Jet Aviation Fuels by Surrogate Mixtures of Hydrocarbon Fluid Blends: Implications for Science and Engineering

“…An initial focus of a recent Unites States Air Force Multi University Research Initiative centered at Princeton University 13 was to develop and test (mostly at the laboratory scale) a fundamental methodology for selecting surrogate components, and formulating mixtures of them, that emulate the fully prevaporized combustion behavior of specific real jet fuels. The work concentrated first on emulating fully prevaporized combustion phenomena, with a continuing realization that the approach must eventually encompass physical properties important to the multiphase combustion characteristic of gas turbine applications.…”

Ellipsometric Measurements of the Thermal Stability of Alternative Fuels

“…Sasol IPK is produced using the Fischer-Tropsch process from gasified coal [19]. Other aspects of such gas to liquid fuels including laminar burning speeds and ignition delay times have been studied previously [20].…”