Measurements of the laminar burning velocities and NO concentrations in neat and blended ethanol and n-heptane flames

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Measurements of the laminar burning velocities and NO concentrations in neat and blended ethanol and n-heptane flames. / Lubrano Lavadera, Marco; Brackmann, Christian; Capriolo, Gianluca; Methling, Torsten; Konnov, Alexander A.

I: Fuel, Vol. 288, 119585, 15.03.2021.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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T1 - Measurements of the laminar burning velocities and NO concentrations in neat and blended ethanol and n-heptane flames

AU - Lubrano Lavadera, Marco

AU - Brackmann, Christian

AU - Capriolo, Gianluca

AU - Methling, Torsten

AU - Konnov, Alexander A.

PY - 2021/3/15

Y1 - 2021/3/15

N2 - Adiabatic laminar burning velocities and post-flame NO mole fractions for neat and blended ethanol and n-heptane premixed flames were experimentally determined using a heat flux burner and laser-induced fluorescence. The flames were stabilized at atmospheric pressure and at an initial temperature of 338 K, over equivalence ratios ranging from 0.6 to 1.5. These experiments are essential for the development, validation and optimization of chemical kinetic models, e.g. for the combustion of gasoline-ethanol fuel mixtures. It was observed that the addition of ethanol to n-heptane leads to an increase in laminar burning velocity that is not proportional to the ethanol content and to a decrease of NO formation. Such a NO reduction is due to the slightly lower flame temperatures of ethanol, which decrease the production of thermal-NO at 0.6 < Φ < 1.2, while under fuel-rich conditions this behavior is due to the lower concentrations of CH radicals, which decrease the production of prompt-NO. At Φ > 1.3, the lower NO formation through the prompt mechanism in the ethanol flames is partially offset by a lower rate of NO consumption through the reburning mechanism. New experimental results were compared with predictions of the POLIMI detailed chemical kinetic mechanism. An excellent agreement between measurements and simulated results was observed for the laminar burning velocities over the equivalence ratio range investigated; however, discrepancies were found for the NO mole fractions, especially under rich conditions. Further numerical analyses were performed to identify the main causes of the observed differences. Differences found at close-to stoichiometric conditions were attributed to an uncertainty in the thermal-NO mechanism. In addition, disagreement under rich conditions could be explained by the relative importance of reactions in hydrogen cyanide consumption pathways.

AB - Adiabatic laminar burning velocities and post-flame NO mole fractions for neat and blended ethanol and n-heptane premixed flames were experimentally determined using a heat flux burner and laser-induced fluorescence. The flames were stabilized at atmospheric pressure and at an initial temperature of 338 K, over equivalence ratios ranging from 0.6 to 1.5. These experiments are essential for the development, validation and optimization of chemical kinetic models, e.g. for the combustion of gasoline-ethanol fuel mixtures. It was observed that the addition of ethanol to n-heptane leads to an increase in laminar burning velocity that is not proportional to the ethanol content and to a decrease of NO formation. Such a NO reduction is due to the slightly lower flame temperatures of ethanol, which decrease the production of thermal-NO at 0.6 < Φ < 1.2, while under fuel-rich conditions this behavior is due to the lower concentrations of CH radicals, which decrease the production of prompt-NO. At Φ > 1.3, the lower NO formation through the prompt mechanism in the ethanol flames is partially offset by a lower rate of NO consumption through the reburning mechanism. New experimental results were compared with predictions of the POLIMI detailed chemical kinetic mechanism. An excellent agreement between measurements and simulated results was observed for the laminar burning velocities over the equivalence ratio range investigated; however, discrepancies were found for the NO mole fractions, especially under rich conditions. Further numerical analyses were performed to identify the main causes of the observed differences. Differences found at close-to stoichiometric conditions were attributed to an uncertainty in the thermal-NO mechanism. In addition, disagreement under rich conditions could be explained by the relative importance of reactions in hydrogen cyanide consumption pathways.

KW - Ethanol

KW - Heat flux method

KW - Laminar burning velocity

KW - LIF

KW - n-Heptane

KW - Nitric oxide

U2 - 10.1016/j.fuel.2020.119585

DO - 10.1016/j.fuel.2020.119585

M3 - Article

AN - SCOPUS:85096131749

VL - 288

JO - Fuel

JF - Fuel

SN - 1873-7153

M1 - 119585

ER -