Article pubs.acs.org/EF
Experimental and Detailed Kinetic Modeling Study of Ethyl Pentanoate (Ethyl Valerate) Oxidation in a Jet Stirred Reactor and Laminar Burning Velocities in a Spherical Combustion Chamber Guillaume Dayma,†,‡,* Fabien Halter,§ Fabrice Foucher,§ Casimir Togbé,‡ Christine Mounaim-Rousselle,§ and Philippe Dagaut‡ †
Université d’Orléans, Faculté des Sciences, 1 Rue de Chartres, 45067 Orléans Cedex 2, France Institut des Sciences de l’Ingénierie et des Systèmes (INSIS), Centre National de la Recherche Scientifique (CNRS), 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France § PRISME, Université d’Orléans, Polytech Vinci, 45072 Orléans Cedex 2, France ‡
S Supporting Information *
ABSTRACT: To improve our understanding of the combustion characteristics of ethyl pentanoate, a possible second generation biofuel, new experimental data were acquired for its oxidation kinetics in two complementary experiments. In a JSR (jet stirred reactor), concentration profiles of stable species were measured at 10 atm over a range of conditions (equivalence ratios of 0.6, 1, 2, fuel initial concentration of 1000 ppm, and temperatures between 560 to 1160 K). In a spherical combustion chamber, unstretched laminar burning velocities of ethyl pentanoate−air mixtures were measured at different pressures and temperatures and for equivalence ratios in the range 0.7−1.4. The oxidation of ethyl pentanoate was modeled using a new detailed kinetic reaction scheme (2719 reactions, 522 species). The chemical kinetic mechanism proposed here yielded good agreement with the present data. To interpret the results, reactions flux and sensitivity analyses were carried out.
1. INTRODUCTION Fueling the future is a difficult challenge for industrial societies. To this end, renewable, ex-biomass fuels for ground transportation are attracting increasing interest because they could reduce net greenhouse gas emissions1 and oil-dependency. Ethanol is the far most important, accounting for over 90% of worldwide biofuels’ production.2 However, the extensive use of ethanol may not be as sustainable as expected,3−5 and other renewable oxygenates have been proposed as fuel components. Furthermore, first-generation biofuels that are presently being produced will probably not provide the large quantities needed for the transportation sector as they compete with food for their feedstock. Lignocellulosic material (plant-derived), represents more promising feedstock that is more abundant and potentially more sustainable.6 However, until now, lignocellulose has required complex and expensive processing for conversion to biofuels. Improvements in transformation processes have largely facilitated the manufacture of valeric biofuels. These biofuels have acceptable energy densities: the energy density of ethyl valerate is ∼30 MJ/kg compared to ∼24 MJ/kg for ethanol and ∼29 MJ/kg for 1-butanol. Their volatility and ignition properties, which depend on their alkoxy chain length, make them compatible for gasoline or diesel applications. Preliminary results concerning valeric biofuels7 have been reported. The authors detailed the process of valeric biofuels production and reported a test performed with engine cars. Ten current types of vehicle, new and used, were fueled exclusively with a mixture of normal gasoline mixed with 15% by volume of ethyl valerate (ethyl pentanoate) and were sent out on the road to cover 500 km a day. After a total distance of © 2012 American Chemical Society
250 000 km, no negative impacts were found in the engine, fuel tank, or lines. The aim of the present study is to provide new kinetic data on the oxidation of ethyl pentanoate using two wellcharacterized experimental set-ups. Mole fractions of stable species were measured as a function of temperature for ethyl pentanoate oxidation in a jet stirred reactor (JSR) at 10 atm (1.013 MPa) over different equivalence ratios (0.6, 1, and 2) and temperatures. Also, burning velocities for ethyl pentanoate premixed laminar flames were measured over a range of equivalence ratios (φ = 0.7−1.4) and pressures (1, 3, 5, and 10 bar). The validity of the newly proposed detailed kinetic reaction scheme for the oxidation of ethyl esters was verified against the present experimental results.
2. EXPERIMENTAL SECTION 2.1. Jet Stirred Reactor. The JSR experimental setup has been described earlier.8−10 It consists of a 4 cm diameter fused silica sphere with four 1 mm inner diameter (i.d.) nozzles. Nitrogen (
