n-Dodecane oxidation at high-pressures: Measurements of ignition delay times and OH concentration time-histories

Abstract Carbon monoxide time-histories and ignition delay times were measured in carbon dioxide diluted methane mixtures behind reflected shockwaves. Experiments were performed around 2 atm for a temperature range between 1650–2000 K. The experiments were performed for a mixture of XCH4 = 0.5%, XO2 = 1.0%, XCO2 = 8.5%, XAr = 90.0%. The mixture was chosen to minimize energy release during the experiment and a minimum of 2 ms was recorded for all experiments. The carbon monoxide time-histories were measured using a tunable diode laser absorption spectroscopy technique and measuring the absorbance at two different wavelengths to isolate the impact of carbon monoxide on the absorbance. Carbon monoxide was measured at a wavelength of 4886.94 nm while the interfering species was measured at 4891.17 nm. Each experiment was performed twice, with the pressure and temperature before combustion being matched to within the experimental uncertainty of the two experiments. The ignition delay times were measured using OH* radical emission to determine the time-scales of the experiments. All experiments were compared to detailed chemical kinetic mechanisms that can be found in the literature. The experimental results show that the detailed mechanisms from the literature were able to accurately predict the general profile of the carbon monoxide time-histories but under-predicted maximum concentration of CO being formed at these conditions.

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Ignition Delay Times of Syngas and Methane in sCO2 Diluted Mixtures for Direct-Fired Cycles

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2019-90178 ◽

2019 ◽

Author(s):

Samuel Barak ◽

Owen Pryor ◽

Erik Ninnemann ◽

Sneha Neupane ◽

Xijia Lu ◽

...

Keyword(s):

Carbon Dioxide ◽

Ignition Delay ◽

High Pressures ◽

Chemical Kinetic ◽

Time Data ◽

Fuel Loading ◽

Supercritical Regime ◽

Reflected Shock ◽

Ignition Delay Times ◽

Delay Times

Abstract In this study, a shock tube is used to investigate combustion tendencies of several fuel mixtures under high carbon dioxide dilution and high fuel loading. Individual mixtures of oxy-syngas and oxy-methane fuels were added to CO2 bath gas environments and ignition delay time data was recorded. Reflected shock pressures maxed around 100 atm, which is above the critical pressure of carbon dioxide in to the supercritical regime. In total, five mixtures were investigated within a temperature range of 1050–1350K. Ignition delay times of all mixtures were compared with predictions of two leading chemical kinetic computer mechanisms for accuracy. The mixtures included four oxy-syngas and one oxy-methane combinations. The experimental data tended to show good agreement with the predictions of literature models for the methane mixture. For all syngas mixtures though the models performed reasonably well at some conditions, predictions were not able to accurately capture the overall behavior. For this reason, there is a need to further investigate the discrepancies in predictions. Additionally, more data must be collected at high pressures to fully understand the chemical kinetic behavior of these mixtures to enable the supercritical CO2 power cycle development.

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Ignition Delay Times of High Pressure Oxy-Methane Combustion With High Levels of CO2 Dilution

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2017-63666 ◽

2017 ◽

Cited By ~ 3

Author(s):

Owen Pryor ◽

Batikan Koroglu ◽

Samuel Barak ◽

Joseph Lopez ◽

Erik Ninnemann ◽

...

Keyword(s):

Shock Tube ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Current Data ◽

Validation Data ◽

Ignition Delay Times ◽

Delay Times ◽

Kinetic Mechanisms ◽

Time Histories

Ignition delay times and methane species time-histories were measured for methane/O2 mixtures in a high CO2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 1 and 31 atm. The experimental mixtures were conducted at an equivalence ratio of 1 with CH4 mole fractions ranging from 3.5%–5% and up to 85% CO2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (GRI 3.0 and ARAMCO Mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into the different parameters showing that the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane under these conditions. Current data provides crucial validation data needed for development of future methane/CO2 kinetic mechanisms.

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