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

# Autoignition Delay Time Measurements of Methane, Ethane, and Propane Pure Fuels and Methane-Based Fuel Blends

[+] Author and Article Information
M. M. Holton, P. Gokulakrishnan, M. S. Klassen, R. J. Roby

Combustion Science and Engineering, Inc., 8940 Old Annapolis Road, Suite L, Columbia, MD 21045

G. S. Jackson

Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742

J. Eng. Gas Turbines Power 132(9), 091502 (Jun 10, 2010) (9 pages) doi:10.1115/1.4000590 History: Received April 16, 2009; Revised May 28, 2009; Published June 10, 2010; Online June 10, 2010

## Abstract

Autoignition delay experiments in air have been performed in an atmospheric flow reactor using typical natural gas components, namely, methane, ethane, and propane. Autoignition delay measurements were also made for binary fuel mixtures of methane/ethane and methane/propane, and ternary mixtures of methane/ethane/propane. The effect of $CO2$ addition to the methane-based fuel blends on autoignition delay times was also investigated. Equivalence ratios for the experiments ranged between 0.5 and 1.25, and temperatures ranged from 930 K to 1140 K. Consistent with past studies, increasing equivalence ratio and increasing inlet temperatures over these ranges decreased autoignition delay times. Furthermore, addition of 5–10% ethane or propane decreased autoignition delay time of the binary methane-based fuel by 30–50%. Further addition of either ethane or propane showed less significant reduction of autoignition delays. Addition of 5–10% $CO2$ slightly decreased the autoignition delay times of methane fuel mixtures. Arrhenius correlations were used to derive activation energies for the ignition of the pure fuels and their mixtures. Results show a reduction in activation energies at the higher temperatures studied, which suggests a change in ignition chemistry at very high temperatures. Measurements show relatively good agreement with predictions from a detailed kinetics mechanism, specifically developed to model ignition chemistry of C1-C3 alkanes.

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## Figures

Figure 1

Summary of autoignition delay times for pure fuels methane, ethane, and propane reported in the literature including experimental conditions

Figure 2

Summary of autoignition delay times for methane-based fuel blends containing ethane and propane reported in the literature including experimental conditions

Figure 3

Schematic of the experimental setup used for ignition delay time measurements

Figure 4

Sample injection valve and CH∗ chemiluminescence signals and ignition delay time definition

Figure 5

Typical performance of available ethylene chemical kinetics mechanisms (35-39) in predicting experimental ethylene ignition data of Brown and Thomas (20) at temperatures between 1102 K and 1771 K and pressures between 1.4 atm and 3.4 atm

Figure 6

Ethylene autoignition delay time measurements obtained in the present work (▲) compared with data from the literature (20,23,30,33) and predictions made by Varatharajan and Williams (37) on ethylene mechanism

Figure 7

Methane autoignition delay time measurements, Arrhenius correlation, GRI 3.0 predictions (36), and kinetics model predictions of Petersen (1)

Figure 8

Ethane autoignition delay time measurements, Arrhenius correlation, and kinetics model predictions of Petersen (1)

Figure 9

Propane autoignition delay time measurements, Arrhenius correlation, and kinetics model predictions of Petersen (1)

Figure 10

Propane autoignition delay time measurements obtained in the present work (ϕ=0.5◼, ϕ=1.0▲) compared with atmospheric pressure measurements reported in the literature (42-43) and kinetics model predictions made by Petersen (1)

Figure 11

Methane/ethane autoignition delay time measurements, Arrhenius correlation, and Petersen (1) mechanism predictions. The mole fractions of methane and ethane used in the Arrhenius correlation were 0.0801 and 0.0083, respectively.

Figure 12

Methane/propane autoignition delay time measurements, Arrhenius correlation, and mechanism predictions of Petersen (1). The mole fractions of methane and propane used in the Arrhenius correlation were 0.0393 and 0.0044, respectively.

Figure 13

Methane/propane autoignition delay time as a function of propane mole fraction in the fuel, ϕ=1.0

Figure 14

Ternary methane/ethane/propane autoignition delay time measurements and mechanism predictions of Petersen (1). Mixture 1: 50% CH4, 25% C2H6, and 25% C3H8; mixture 2: 85% CH4, 10% C2H6, and 5% C3H8.

Figure 15

Effect of CO2 addition on 75% methane/25% ethane fuel blend autoignition delay time. CO2 composition is reported as mol % in the fuel mixture.

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