New experimental insights into acetylene oxidation through novel ignition delay times, laminar burning velocities and chemical kinetic modelling

2019 ◽  
Vol 37 (1) ◽  
pp. 583-591 ◽  
Author(s):  
Nitin Lokachari ◽  
Ultan Burke ◽  
Ajoy Ramalingam ◽  
Mattias Turner ◽  
Raik Hesse ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Kinetic Modelling ◽  
Chemical Kinetic ◽  
Ignition Delay Times ◽  
Delay Times

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

scholarly journals Alternative Fuels Based on Biomass: An Experimental and Modeling Study of Ethanol Cofiring to Natural Gas

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Marina Braun-Unkhoff ◽  
Jens Dembowski ◽  
Jürgen Herzler ◽  
Jürgen Karle ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Kinetic Modeling ◽  
Ignition Delay ◽  
Chemical Kinetic ◽  
Parameter Range ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times

In response to the limited resources of fossil fuels as well as to their combustion contributing to global warming through CO2 emissions, it is currently discussed to which extent future energy demands can be satisfied by using biomass and biogenic by-products, e.g., by cofiring. However, new concepts and new unconventional fuels for electric power generation require a re-investigation of at least the gas turbine burner if not the gas turbine itself to ensure a safe operation and a maximum range in tolerating fuel variations and combustion conditions. Within this context, alcohols, in particular, ethanol, are of high interest as alternative fuel. Presently, the use of ethanol for power generation—in decentralized (microgas turbines) or centralized gas turbine units, neat, or cofired with gaseous fuels like natural gas (NG) and biogas—is discussed. Chemical kinetic modeling has become an important tool for interpreting and understanding the combustion phenomena observed, for example, focusing on heat release (burning velocities) and reactivity (ignition delay times). Furthermore, a chemical kinetic reaction model validated by relevant experiments performed within a large parameter range allows a more sophisticated computer assisted design of burners as well as of combustion chambers, when used within computational fluid dynamics (CFD) codes. Therefore, a detailed experimental and modeling study of ethanol cofiring to NG will be presented focusing on two major combustion properties within a relevant parameter range: (i) ignition delay times measured in a shock tube device, at ambient (p = 1 bar) and elevated (p = 4 bar) pressures, for lean (φ = 0.5) and stoichiometric fuel–air mixtures, and (ii) laminar flame speed data at several preheat temperatures, also for ambient and elevated pressure, gathered from literature. Chemical kinetic modeling will be used for an in-depth characterization of ignition delays and flame speeds at technical relevant conditions. An extensive database will be presented identifying the characteristic differences of the combustion properties of NG, ethanol, and ethanol cofired to NG.

Investigation of Chemical Kinetic Model for Hypergolic Propellant of Monomethylhydrazine and Nitrogen Tetroxide

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hu Hong-bo ◽  
Chen Hong-yu ◽  
Yan Yu ◽  
Zhang Feng ◽  
Yin Ji-Hui ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Flame Temperature ◽  
Chemical Kinetic ◽  
Chemical Mechanism ◽  
Chamber Pressure ◽  
Nitrogen Tetroxide ◽  
Combustion Flame ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Calculation Results

Abstract Hypergolic bipropellant of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) is extensively used in spacecraft propulsion applications and rocket engines. But studies on the chemical kinetic mechanism of MMH/NTO are limited. So, in this study by integrating the submechanisms of MMH decomposition, NTO thermal decomposition, MMH/NTO and intermediates, and small hydrocarbons, the comprehensive chemical mechanism of MMH/NTO bipropellant is proposed. The present chemical mechanism consists of 72 species and 406 elementary reactions. In two respects of ignition delay times and combustion flame temperatures, the present model has been validated against the theoretical calculation results and also compared with other kinetic models in the literature. The validations show that the predicted ignition delay times by the present kinetic model are highly consistent with the theoretical data and well describe the pressure-dependent characteristic. For combustion flame temperature, the present model also exhibits better predictions to the theoretical calculation results, which are also the same as the predictions by the MMH-RFNA model. Furthermore, the influences of initial temperature, chamber pressure, and NTO/HHM mass ratio (O/F) on the ignition delay time and combustion flame temperature are investigated. The auto-ignition behavior of MMH/NTO propellant is sensitive to initial temperature and chamber pressure, and the combustion flame temperature is more sensitive to the O/F. This study provides a detail chemical kinetics model for further mechanism simplification and combustion numerical simulation.

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.

An Investigation of Combustion Properties of Butanol and its Potential for Power Generation

2017 ◽  
Author(s):  
Torsten Methling ◽  
Sandra Richter ◽  
Trupti Kathrotia ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Transformation Method ◽  
Chemical Kinetic ◽  
Reaction Model ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times ◽  
Reaction Models

Over the last years, global concerns about energy security and climate change have resulted in many efforts focusing on the potential utilization of non-petroleum-based, i.e. bio-derived, fuels. In this context, n-butanol has recently received high attention because it can be produced sustainably. A comprehensive knowledge about its combustion properties is inevitable to ensure an efficient and smart use of n-butanol if selected as a future energy carrier. In the present work, two major combustion characteristics, here laminar flame speeds applying the cone-angle method and ignition delay times applying the shock tube technique, have been studied, experimentally and by modeling exploiting detailed chemical kinetic reaction models, at ambient and elevated pressures. The in-house reaction model was constructed applying the RMG-method. A linear transformation method recently developed, linTM, was exploited to generate a reduced reaction model needed for an efficient, comprehensive parametric study of the combustion behavior of n-butanol/hydrocarbon mixtures. All experimental data were found to agree with the model predictions of the in-house reaction model, for all temperatures, pressures, and fuel-air ratios. On the other hand, calculations using reaction models from the open literature mostly overpredict the measured ignition delay times by about a factor of two. The results are compared to those of ethanol, with ignition delay times very similar and laminar flame speeds of n-butanol slightly lower, at atmospheric pressure.

Auto Ignition Study of Methane and Bio Alcohol Fuel Blends

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Xuan Zheng ◽  
Shirin Jouzdani ◽  
Benjamin Akih-Kumgeh
Keyword(s):  
Experimental Data ◽  
Kinetic Models ◽  
Ignition Delay ◽  
Chemical Kinetic ◽  
Dual Fuel ◽  
Fuel Blends ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Alcohol Fuel ◽  
Delay Times

Abstract Methane (CH4) and bio alcohols have different ignition properties. These have been extensively studied and the resulting experimental data have been used to validate chemical kinetic models. Methane is the main component of natural gas, which is of interest because of its relative availability and lower emissions compared to other hydrocarbon fuels. Given growing interest in fuel-flexible systems, there can be situations in which the combustion properties of natural gas need to be modified by adding biofuels such as bio alcohols. This can occur in dual-fuel internal combustion engines or gas turbines with dual-fuel capabilities. The combustion behavior of such blends can be understood by studying the auto ignition properties in fundamental combustion experiments. Studies of the ignition of such blends are very limited in the literature. In this work, the auto ignition of methane and bio alcohol fuel blends is investigated using a shock tube facility. The chosen bio alcohols are ethanol (C2H5OH) and n-propanol (NC3H7OH). Experiments are carried out at 3 atm and 10 atm for stoichiometric and lean mixtures of fuel, oxygen, and argon. The ignition delay times of the pure fuels are first established at conditions of constant oxygen concentration and comparable pressures. The ignition delay times of blends with 50% methane are then measured. The pyrolysis kinetics of the blends is further explored by measuring CO formation during pyrolysis of the alcohol and methane–alcohol blends. The resulting experimental data are compared with the predictions of selected chemical kinetic models to establish the ability of these models to predict the disproportionate enhancement of methane ignition by the added alcohol.

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.

Auto Ignition Study of Methane and Bio Alcohol Fuel Blends

2019 ◽  
Author(s):  
Xuan Zheng ◽  
Shirin Jouzdani ◽  
Benjamin Akih-Kumgeh
Keyword(s):  
Experimental Data ◽  
Kinetic Models ◽  
Ignition Delay ◽  
Chemical Kinetic ◽  
Dual Fuel ◽  
Fuel Blends ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Alcohol Fuel ◽  
Delay Times

Abstract Methane (CH4) and bio alcohols have different ignition properties. These have been extensively studied and the resulting experimental data have been used to validate chemical kinetic models. Methane is the main component of natural gas, which is of interest because of its relative availability and lower emissions compared to other hydrocarbon fuels. Given growing interest in fuel-flexible systems, there can be situations in which the combustion properties of natural gas need to be modified by adding biofuels, such as bio alcohols. This can occur in dual fuel internal combustion engines or gas turbines with dual fuel capabilities. The combustion behavior of such blends can be understood by studying the auto ignition properties in fundamental combustion experiments. Studies of the ignition of such blends are very limited in the literature. In this work, the auto ignition of methane and bio alcohol fuel blends is investigated using a shock tube facility. The chosen bio alcohols are ethanol (C2H5OH) and n-propanol (NC3H7OH). Experiments are carried out at 3 atm and 10 atm for stoichiometric and lean mixtures of fuel, oxygen, and argon. The ignition delay times of the pure fuels are first established at conditions of constant oxygen concentration and comparable pressures. The ignition delay times of blends with 50% methane are then measured. The pyrolysis kinetics of the blends is further explored by measuring CO formation during pyrolysis of the alcohol and methane-alcohol blends. The resulting experimental data are compared with the predictions of selected chemical kinetic models to establish the ability of these models to predict the disproportionate enhancement of methane ignition by the added alcohol.

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