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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

# Ignition and Flame Speed Kinetics of Two Natural Gas Blends With High Levels of Heavier Hydrocarbons

[+] Author and Article Information
Gilles Bourque

Darren Healy, Henry Curran

Department of Chemistry, National University of Ireland, Galway, Ireland

Christopher Zinner, Danielle Kalitan

Department of Mechanical, Materials, and Aerospace Engineering, University of Central Florida, Orlando, FL 32816

Jaap de Vries, Christopher Aul, Eric Petersen

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843

J. Eng. Gas Turbines Power 132(2), 021504 (Oct 30, 2009) (11 pages) doi:10.1115/1.3124665 History: Received April 04, 2008; Revised May 22, 2008; Published October 30, 2009

## Abstract

High-pressure experiments and chemical kinetics modeling were performed to generate a database and a chemical kinetic model that can characterize the combustion chemistry of methane-based fuel blends containing significant levels of heavy hydrocarbons (up to 37.5% by volume). Ignition delay times were measured in two different shock tubes and in a rapid compression machine at pressures up to 34 atm and temperatures from 740 K to 1660 K. Laminar flame speeds were also measured at pressures up to 4 atm using a high-pressure vessel with optical access. Two different fuel blends containing ethane, propane, n-butane, and n-pentane added to methane were studied at equivalence ratios varying from lean (0.3) to rich (2.0). This paper represents the most comprehensive set of experimental ignition and laminar flame speed data available in the open literature for $CH4/C2H6/C3H8/C4H10/C5H12$ fuel blends with significant levels of $C2+$ hydrocarbons. Using these data, a detailed chemical kinetics model based on current and recent work by the authors was compiled and refined. The predictions of the model are very good over the entire range of ignition delay times, considering the fact that the data set is so thorough. Nonetheless, some improvements to the model can still be made with respect to ignition times at the lowest temperatures and for the laminar flame speeds at pressures above 1 atm and at rich conditions.

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## Figures

Figure 10

Effect of mixture composition using shock-tube ignition delay time data. Points are experimental results; lines through data points are best fit lines, for clarity in deducing the trends; lines representing pure methane are model calculations. Solid lines correspond to ϕ=1.0, and dashed lines correspond to ϕ=0.3. (a) Pressure≈1 atm. (b) Pressure≈30 atm.

Figure 13

Measured laminar burning velocities and comparison to model predictions for Pi=1 atm, Ti=298 K. (a) Methane and NG2 in air. (b) Methane and NG3 in air.

Figure 1

Effect of pressure for NG2 mixture, ϕ=0.5 in air. Points are experimental results, and lines are model simulations. Dashed lines correspond to data at 8 atm and 20 atm.

Figure 2

Effect of pressure for NG2 mixture, ϕ=1.0 in air. Points are experimental results, and lines are model simulations. Dashed lines correspond to P=7 and 20 atm.

Figure 3

Shock-tube ignition data and comparison to model for NG2, ϕ=0.3

Figure 4

Shock-tube ignition data and comparison to model for NG2, ϕ=2.0

Figure 5

Fuel-lean ignition delay time data from the shock-tube experiments and comparison to model for NG3, ϕ=0.3; dashed line: 7.6 atm

Figure 6

Lean ignition delay time data from the shock-tube experiments and comparison to model for NG3, ϕ=0.5

Figure 7

Stoichiometric ignition delay time data from the shock-tube experiments and comparison to model for NG3, ϕ=1.0

Figure 8

Fuel-rich ignition delay time data from the shock-tube experiments and comparison to model for NG3, ϕ=2.0

Figure 9

Effect of equivalence ratio for the NG2 mixture using both shock-tube and RCM data. Points are experimental results, and lines are model simulations. Dashed lines correspond to ϕ=1.0.(a) Pressure≈10 atm. (b) Pressure≈20 atm.

Figure 11

Schlieren photographs of NG2/air with and without background subtraction, ϕ=1.0; frame width is 12 cm. (a) Pressure=1 atm. (b) Pressure=4 atm.

Figure 12

Pressure histories of CH4/air mixtures for equivalence ratios of 0.8, 0.9, and 1.0; Pi=1 atm, Ti=298 K. All images used in the data reduction are taken before significant pressure rise.

Figure 14

Pressure dependence of the laminar burning velocity for NG2 experiments and comparison to model for CH4, NG2, and NG3. ϕ=1.0, Ti=298 K.

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