Recent progress in gasoline surrogate fuels

Abstract

Petroleum-derived gasoline is currently the most widely used fuel for transportation propulsion. The design and operation of gasoline fuels is governed by specific physical and chemical kinetic fuel properties. These must be thoroughly understood in order to improve sustainable gasoline fuel technologies in the face of economical, technological, and societal challenges. For this reason, surrogate mixtures are formulated to emulate the thermophysical, thermochemical, and chemical kinetic properties of the real fuel, so that fundamental experiments and predictive simulations can be conducted. Early studies on gasoline combustion typically adopted single component or binary mixtures (n-heptane/isooctane) as surrogates. However, the last decade has seen rapid progress in the formulation and utilization of ternary mixtures (n-heptane/isooctane/toluene), as well as multicomponent mixtures that span the entire carbon number range of gasoline fuels (C 4 ÀC 10). The increased use of oxygenated fuels (ethanol, butanol, MTBE, etc.) as blending components/additives has also motivated studies on their addition to gasoline fuels. This comprehensive review presents the available experimental and chemical kinetic studies which have been performed to better understand the combustion properties of gasoline fuels and their surrogates. Focus is on the development and use of surrogate fuels that emulate real fuel properties governing the design and operation of engines. A detailed analysis is presented for the various classes of compounds used in formulating gasoline surrogate fuels, including n-paraffins, isoparaffins, olefins, naphthenes, and aromatics. Chemical kinetic models for individual molecules and mixtures of molecules to emulate gasoline surrogate fuels are presented. Despite the recent progress in gasoline surrogate fuel combustion research, there are still major gaps remaining; these are critically discussed, as well as their implications on fuel formulation and engine design.

A minimalist functional group (MFG) approach for surrogate fuel formulation

“…One of the important advantages of NMR spectroscopy is that functional groups closely resembling each other give distinct signals, which facilitates identification and quantification. 1 H NMR experiments of the six FACE gasoline fuels namely FACE A, C, F, G, I and J (acquired from Chevron Philips Chemical Co) were performed and the spectra are shown in Fig. 1.…”

“…Transportation fuels, such as gasoline [1] and diesel [2] are complex hydrocarbon mixtures containing hundreds to thousands of individual molecules. Identifying and quantifying all of these molecules is challenging, which complicates modeling of their combustion behavior.…”

“…have also been used as targets in developing surrogates. Surrogate fuel formulation strategies and the necessary fuel property targets have been discussed in detail [1,8,18,21,22,35].…”

Three-stage heat release in n-heptane auto-ignition

“…Aero-engines and stationary power generation turbines control autoignition for safety reasons and/or to extend operability limits [3]. This work aims to provide new insights into the ignition characteristics of n-heptane, a widely used surrogate molecule for studying combustion of practical hydrocarbon fuels [4,5].…”

On the universality of ignition delay times of distillate fuels at high temperatures: A statistical approach

“…This value is independent of fuel composition and only depends on pressure, temperature and equivalence ratio [21] for multicomponent mixtures. Based on wide-ranging experimental IDTs of gasoline and naphtha fuels, AlAbbad et al [25] and Sarathy et al [26] recently reported that a number of fuels with different compositions and octane numbers exhibited very similar IDTs at high temperatures. Davidson et al [27] performed an experimental investigation of the hightemperature ignition delay times of various distillate fuels including gasoline, diesel and jet fuel near stoichiometric conditions, and showed that the IDTs of these distillate fuels are similar within the experimental scatter.…”