Reactivity and Ignition Delay Measurements of Petroleum-based Fuels, Surrogate Fuels and Biofuels

Abstract

Energy demand is rapidly increasing due to the increase in population and rising living standards. Petroleum-based fuels account for the main source of energy consumed in the world. However, they are also considered to be the main source of the unwanted emissions to the atmosphere. In this context, chemical kinetic studies of combustion processes are essential for a better understanding of the underlying reactions and to achieve increased combustion efficiency and reduced pollutant emissions. In this study, ignition delay times, a global indicator of fuel reactivity, were measured for promising fuels for use in advanced combustion engines. Also, rate coefficients were measured for promising oxygenated hydrocarbons that can be used as additives to conventional fuels. Ignition delay time measurements of four primary reference fuel (PRF) blends, mixtures considered to be some of the simplest gasoline surrogates, were measured behind reflected shock waves to provide a large experimental dataset to validate PRF chemical kinetic models. The kinetic modeling predictions from four chemical kinetic models were compared with the experimental data. Ignition delay correlations were also developed to reduce the simulation cost of complicated models. Recently, naphtha, a low-octane distillate fuel, has been proposed as a low-cost refinery fuel. Likewise, a mid-octane blend which consists of low-octane (light and heavy naphtha) and high-octane (reformate) distillate fuels has been proposed to power gasoline compression ignition (GCI) engines. In this work, experimental and modeling studies were conducted on low and mid-octane distillate fuels (naphtha and GCI blend) and surrogate candidates to assess their autoignition characteristics for use in advanced internal combustion engines. Oxygenated molecules are considered to be promising additives to conventional fuels. Thermal decomposition of three esters (ethyl levulinate, ethyl propionate and diethyl carbonate ) and a five-member cyclic ketone (cyclopentanone) was investigated in this work. Laser absorption technique was employed to follow the reaction progress by measuring ethylene (C2H4) near 10.532 µm using a CO2 gas laser for the decomposition process of the three esters. The reaction progress of the decomposition of cyclopentanone was followed by monitoring CO formation using a quantum cascade laser at a wavelength near 4.556 µm.