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Laminar Burning Velocity Measurements of Toluene + Air Mixtures and Ternary Surrogate Formulation at Elevated Temperatures
Journal
Energy and Fuels
ISSN
08870624
Date Issued
2022-06-16
Author(s)
Padhi, Upasana Priyadarshani
Kumar, Rohit
Dorlikar, Nilay
Kumar, Sudarshan
Abstract
In the present work, the externally heated diverging channel (EHDC) method is employed to measure the laminar burning velocity of toluene + air mixtures at elevated temperatures up to 610 K. The experiments are conducted over a range of equivalence ratios (φ = 0.7-1.5) at atmospheric pressure. The measured values are consistent with the reported values from earlier experiments at lower temperatures. The predictions using the LLNL V2.0, Metcalfe, and Yuan kinetic models are able to capture the fundamental combustion characteristics of toluene + air oxidation. The kinetic models are well within the uncertainty range of the present measurements. However, significant discrepancies are observed with the reduced kinetic model of Narayanaswamy over the entire range of equivalence ratios. The temperature exponent shows a good match between the present measurements and mechanism predictions of LLNL V2.0 and Metcalfe. The sensitivity analysis reveals that the fuel-specific intermediate species (hydroperoxyl, benzyl, cresol, and phenol) inhibit the burning velocity significantly. A three-component gasoline surrogate, TRF-85: 20.27% n-heptane, 50.73% iso-octane, and 29% toluene by volume, is proposed using the energy-fraction mixing rule to reproduce the laminar burning characteristics of commercial gasoline fuels with the same octane number. The laminar burning velocity of TRF-85 is determined for the mixture temperature range of 300-600 K and φ = 0.7-1.4. The TRF-85 (up to 600 K mixture temperature) exhibits a fair agreement with the measurements of the commercial gasoline using the EHDC method and reported values of TRF in the literature. The computed laminar burning velocity values using the LLNL V1.0 kinetic model showed a good match with TRF-85 values.