Laminar Flame Speed Measurements and Modeling of Alkane Blends at Elevated Pressures With Various Diluents

Abstract

Laminar flame speeds at elevated pressure for methane-based fuel blends are important for refining the chemical kinetics that are relevant at engine conditions. The present paper builds on earlier measurements and modeling by the authors by extending the validity of a chemical kinetics mechanism to laminar flame speed measurements obtained in mixtures containing significant levels of helium. Such mixtures increase the stability of the experimental flames at elevated pressures and extend the range of laminar flame speeds. Two experimental techniques were utilized, namely a Bunsen burner method and an expanding spherical flame method. Pressures up to 10 atm were studied, and the mixtures ranged from pure methane to binary blends of CH4/C2H6 and CH4/C3H8. In the Bunsen flames, the data include elevated initial temperatures up to 650 K. There is generally good agreement between model and experiment, although some discrepancies still exist with respect to equivalence ratio for certain cases. A significant result of the present study is that the effect of mixture composition on flame speed is well captured by the mechanism over the extreme ranges of initial pressure and temperature covered herein. Similarly, the mechanism does an excellent job at modeling the effect of initial temperature for methane-based mixtures up to at least 650 K.

Ignition delay times, laminar flame speeds, and mechanism validation for natural gas/hydrogen blends at elevated pressures

“…The effect of hydrogen addition to methane and natural gas has been shown to vary with the amount of higher-order hydrocarbons in the natural gas, the equivalence ratio (φ), and the pressure [31,32]. However, putting together a test list covering a wide range of pressures, % hydrogen, stoichiometry, and fuel blend could prove a huge task due to the large number of possible combinations.…”

Validation of turbulent flame speed models for methane–air-mixtures at high pressure gas engine conditions

“…Basing on a comparison to measured values of [6][7][8][9][10][11], an uncertainty of 15% is expected for the laminar flame speed from the reaction kinetic simulations at the investigated pressure range. These deviations of the laminar flame speed combined with those caused by the cyclic fluctuations of the measured in-cylinder pressure lead to the depicted error bars of Figs.…”

“…2 and 4. The calculated flame speeds lie among the measurement results from spherical flames in constant volume or constant pressure chambers [6,[8][9][10][11] and from counterflow flames [7]. The maximal deviation at high pressure is approximately 15%.…”

“…Symbols: Experimental values from[7,[9][10][11] at 0.1 MPa (grey symbols), 0.5 MPa (black symbols) and 1.0 MPa (grey symbols).…”

The engine reformer: Syngas production in an engine for compact gas‐to‐liquids synthesis

“…At equivalence ratios > 1.5, this value drops below 10 cm/s. [24] In order to improve combustion and overall engine performance at f M > 1.8, higher flame speeds are possible at elevated temperatures by preheating intake mixtures. For example, at methane-air equivalence ratios of 1.4, the flame speed of a mixture with initial temperature of 34 8C was computed to be 22 cm/s, while that with a temperature of 342 8C had a flame speed of 88 cm/s.…”