Reduced Chemical Kinetic Mechanisms for Oxy/Methane Supercritical CO2 Combustor Simulations

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Ladislav Vesely ◽  
Scott Martin ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu
Keyword(s):  
Gas Phase ◽  
High Pressures ◽  
Fluid Dynamic ◽  
Chemical Kinetic ◽  
Flux Analysis ◽  
Analysis Method ◽  
Stirred Reactor ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Kinetic Mechanisms

Reduced mechanisms are needed for use with computational fluid dynamic codes (CFD) utilized in the design of combustors. Typically, reduced mechanisms are created from a detailed mechanism, which contain numerous species and reactions that are computationally difficult to handle using most CFD codes. Recently, it has been shown that the detailed aramco 2.0 mechanism well predicted the available experimental data at high pressures and in highly CO2 diluted methane mixtures. Here, a 23-species gas-phase mechanism is derived from the detailed aramco 2.0 mechanism by path-flux-analysis method (PFA) by using CHEM-RC. It is identified that the reaction CH4 + HO2 ⇔ CH3 + H2O2 is very crucial in predicting the ignition delay times (IDTs) under current conditions. Further, it is inferred that species C2H3 and CH3OH are very important in predicting IDTs of lean sCO2 methane mixtures. Also, the 23-species mechanism presented in this work is able to perform on par with the detailed aramco 2.0 mechanism in terms of simulating IDTs, perfectly stirred-reactor (PSR) estimates under various CO2 dilutions and equivalence ratios, and prediction of turbulence chemistry interactions. It is observed that the choice of equation of state has no significant impact on the IDTs of supercritical CH4/O2/CO2 mixtures but it influences supercritical H2/O2/CO2 mixtures considered in this work.

A Reduced Kinetic Mechanism for Oxy/Methane sCO2 Combustor Simulations

2018 ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Ladislav Vesely ◽  
Scott Martin ◽  
Jose O. Bobren-Diaz ◽  
Subith Vasu
Keyword(s):  
Ignition Delay ◽  
Ignition Delay Time ◽  
High Pressures ◽  
Fluid Dynamic ◽  
Kinetic Mechanism ◽  
Flux Analysis ◽  
Analysis Method ◽  
Stirred Reactor ◽  
Ignition Delay Times ◽  
Delay Times

Reduced mechanisms are needed for use with computational fluid dynamic codes (CFD) utilized in the design of combustors. Typically, the reduced mechanisms are created from the detailed mechanisms which contain numerous species and reactions that are computationally difficult to handle using most CFD codes. Recently, it has been shown that the detailed Aramco 2.0 mechanism well predicted the available experimental data at high pressures and in high-CO2 diluted methane mixtures. Further, a 23-species gas-phase mechanism is derived from the detailed Aramco 2.0 mechanism by path-flux-analysis method (PFA) by using CHEM-RC. It is identified that the reaction CH4+HO2⇔ CH3+H2O2 is very crucial in predicting the ignition delay times under current conditions. Further, it is inferred that species C2H3 and CH3OH are very important in predicting the ignition delay time of lean sCO2 methane mixtures. Also, the 23-species mechanism presented in this work is performing on par with the detailed Aramco 2.0 mechanism in-terms of simulating ignition delay times, perfectly-stirred-reactor estimates under various CO2 dilutions and equivalence ratios, and prediction of turbulence chemistry interactions. It is observed that the choice of equation-of-state has no significant impact on the ignition delay times of supercritical CH4/O2/CO2 mixtures but it influences supercritical H2/O2/CO2 mixtures considered in this work.

CO Time-Histories During Oxy-Methane Combustion in a CO2 Environment

2019 ◽  
Author(s):  
Owen M. Pryor ◽  
Erik Ninnemann ◽  
Subith Vasu
Keyword(s):  
Carbon Monoxide ◽  
Ignition Delay ◽  
Methane Combustion ◽  
Chemical Kinetic ◽  
Tunable Diode Laser ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Kinetic Mechanisms ◽  
Time Histories ◽  
The Impact

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.

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

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.

A path flux analysis method for the reduction of detailed chemical kinetic mechanisms

2010 ◽  
Vol 157 (7) ◽  
pp. 1298-1307 ◽  
Author(s):  
Wenting Sun ◽  
Zheng Chen ◽  
Xiaolong Gou ◽  
Yiguang Ju
Keyword(s):  
Chemical Kinetic ◽  
Flux Analysis ◽  
Analysis Method ◽  
Kinetic Mechanisms ◽  
Detailed Chemical

Ignition Delay Times of Oxy-Syngas and Oxy-Methane in Supercritical CO2 Mixtures for Direct-Fired Cycles

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Erik Ninnemann ◽  
Sneha Neupane ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ignition Delay ◽  
Supercritical Co2 ◽  
High Pressures ◽  
High Efficiency ◽  
Predictive Accuracy ◽  
Chemical Kinetic ◽  
Reflected Shock ◽  
Ignition Delay Times ◽  
Delay Times

Abstract The direct-fired supercritical CO2 (sCO2) cycles promise high efficiency and reduced emissions while enabling complete carbon capture. However, there is a severe lack of fundamental combustion kinetics knowledge required for the development and operation of these cycles, which operate at high pressures and with high CO2 dilution. Experiments at these conditions are very challenging and costly. In this study, a shock tube was used to investigate the auto-ignition tendencies of several 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 were recorded. Reflected shock pressures neared 100 atm, above the critical pressure of carbon dioxide into the supercritical regime. In total, five mixtures were investigated with a pressure range of 70–100 atm and a temperature range of 1050–1350 K. Measured ignition delay times of all mixtures were compared with two leading chemical kinetic mechanisms for their predictive accuracy. The mixtures included four oxy-syngas and one oxy-methane compositions. The literature mechanisms tended to show good agreement with the data for the methane mixture, while these models were not able to accurately capture all behavior for syngas mixtures tested in this study. For this reason, there is a need to further investigate the discrepancies. To the best of our knowledge, we report the first ignition data for the selected mixtures at these conditions. Current work also highlights the need for further work at high pressures to fully understand the chemical kinetic behavior of these mixtures to enable the sCO2 power cycle development.

Development of Detailed Chemical Kinetic Mechanisms for Ignition/Oxidation of JP-8/Jet-A/JP-7 Fuels

2003 ◽  
Author(s):  
M. A. Mawid ◽  
T. W. Park ◽  
B. Sekar ◽  
C. A. Arana
Keyword(s):  
Chemical Kinetic ◽  
Current Status ◽  
Fuel Blend ◽  
Temperature Oxidation ◽  
Temperature Range ◽  
Delay Times ◽  
Kinetic Mechanisms ◽  
Surrogate Fuel ◽  
Autoignition Delay ◽  
Detailed Chemical

Progress on development and validation of detailed chemical kinetic mechanisms for the U.S. Air Force JP-8 and JP-7 fuels [1] is reported in this article. Two JP-8 surrogate fuel blends were considered. The first JP-8 surrogate blend contained 12 pure hydrocarbon components, which were 15% n-C10H22, 20% n-C12H26, 15% n-C14H30, 10% n-C16H34, 5% i-C8H18, 5% C7H14, 5% C8H16, 5% C8H10, 5% C10H14, 5% C9H12, 5% C10H12 and 5% C11H10 by weight. The second JP-8 surrogate blend contained 4 components, which were 45% n-C12H26, 20% n-C10H22, 25% C10H14, and 10% C7H14 by weight. A five-component surrogate blend for JP-7 was also considered. The JP-7 surrogate blend components were 30% n-C10H22, 30% n-C12H26, 30% C10H20, 5% i-C8H18, and 5% C7H8 by weight. The current status of the JP-8 and JP-7 mechanisms is that they consist of 221 species and 1483 reactions and 205 species and 1438 reactions respectively. Both JP-8 and JP-7 mechanisms were evaluated using a lean fuel-air mixture, over a temperature range of 900–1050 K and for atmospheric pressure conditions by predicting autoignition delay times and comparing them to the available experimental data for Jet-A fuel. The comparisons demonstrated the ability of the 12-component JP-8 surrogate fuel blend to predict the autoignition delay times over a wider range of temperatures than the 4-component JP-8 surrogate fuel blend. The 5-component JP-7 surrogate blend predicted autoignition delay times lower than those of JP-8 blends and Jet-A fuel. The JP-8 and JP-7 mechanisms predictions, however, showed less agreement with the measurements towards the lower end of the temperature range (i.e., less than 900 K). Therefore, low temperature oxidation reactions and the sensitivities of the autoignition delays to reaction rate constants are still needed.

Experimental Study on Ethane Ignition Delay Times and Evaluation of Chemical Kinetic Models

2015 ◽  
Vol 29 (7) ◽  
pp. 4557-4566 ◽  
Author(s):  
Erjiang Hu ◽  
Yizhen Chen ◽  
Zihang Zhang ◽  
Xiaotian Li ◽  
Yu Cheng ◽  
...  
Keyword(s):  
Experimental Study ◽  
Kinetic Models ◽  
Ignition Delay ◽  
Chemical Kinetic ◽  
Ignition Delay Times ◽  
Delay Times
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