scholarly journals Chemical Kinetic Mechanism Study on Premixed Combustion of Ammonia/Hydrogen Fuels for Gas Turbine Use

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Hua Xiao ◽  
Agustin Valera-Medina
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Ignition Delay ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Sensitivity Analyses ◽  
Mechanism Study ◽  
Combustion Chemistry ◽  
Chemical Mechanisms ◽  
Ignition Delay Times

To explore the potential of ammonia-based fuel as an alternative fuel for future power generation, studies involving robust mathematical, chemical, thermofluidic analyses are required to progress toward industrial implementation. Thus, the aim of this study is to identify reaction mechanisms that accurately represent ammonia kinetics over a large range of conditions, particularly at industrial conditions. To comprehensively evaluate the performance of the chemical mechanisms, 12 mechanisms are tested in terms of flame speed, NOx emissions and ignition delay against the experimental data. Freely propagating flame calculations indicate that Mathieu mechanism yields the best agreement within experimental data range of different ammonia concentrations, equivalence ratios, and pressures. Ignition delay times calculations show that Mathieu mechanism and Tian mechanism yield the best agreement with data from shock tube experiments at pressures up to 30 atm. Sensitivity analyses were performed in order to identify reactions and ranges of conditions that require optimization in future mechanism development. The present study suggests that the Mathieu mechanism and Tian mechanism are the best suited for the further study on ammonia/hydrogen combustion chemistry under practical industrial conditions. The results obtained in this study also allow gas turbine designers and modelers to choose the most suitable mechanism for combustion studies.

Theoretical Investigation of Autoignition of Combustible Gas Mixtures in Rapid Compression Machines

2002 ◽  
Author(s):  
Shaoping Shi ◽  
Daniel Lee ◽  
Sandra McSurdy ◽  
Michael McMillian ◽  
Steven Richardson ◽  
...  
Keyword(s):  
Experimental Data ◽  
Theoretical Investigation ◽  
Ignition Delay ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Independent Manner ◽  
Elementary Reactions ◽  
Chemical Kinetic Mechanism ◽  
Rapid Compression

In any theoretical investigation of ignition processes in natural gas reciprocating engines, physical and chemical mechanisms must be adequately modeled and validated in an independent manner. The Rapid Compression Machine (RCM) has been used in the past as a tool to validate both autoignition models as well as turbulent mixing effects. In this study, two experimental cases were examined. In the first experimental case, the experimental measurements of Lee and Hochgreb (1998a) were chosen to validate the simulation results. In their experiments, hydrogen/oxygen/argon mixtures were used as reactants. In the simulations, a reduced chemical kinetic mechanism consisting of 10 species and 19 elementary reactions coupled to a CFD software, Fluent 6, was used to simulate the autoignition. The ignition delay from the simulation agreed very well with that from the experimental data of Lee and Hochgreb, (1998b). In the second case, experimental data derived from an RCM with two opposed, pneumatically driven pistons (Brett et al., 2001) were used to study the autoignition of methane/oxygen/argon mixtures. The reduced chemical kinetic mechanism DRM22, derived from the GRI-Mech reaction scheme coupled to Fluent 6, was applied in the simulations. The DRM22 scheme included 22 species and 104 reactions. When methane/oxygen/argon mixture were simulated for the RCM, the ignition delay deviated about 15% from the experimental results. The simulation approaches as well as the validation results are discussed in detail in this paper. The paper also discusses an evaluation of reduced reaction models available in the literature for subsequent Fluent modeling.

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.

Investigating Trends in Simulated Ignition Timing Across a Wide Range of Conditions Including Fuel Reactivity

2012 ◽  
Author(s):  
Michael V. Johnson ◽  
S. Scott Goldsborough ◽  
Timothy A. Smith ◽  
Steven S. McConnell
Keyword(s):  
Ignition Delay ◽  
Equivalence Ratio ◽  
Computational Cost ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Ignition Timing ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Initial Work ◽  
Ci Engines

Continued interest in kinetically-modulated combustion regimes, such as HCCI and PCCI, poses a significant challenge in controlling the ignition timing due to the lack of direct control of combustion phasing hardware available in traditional SI and CI engines. Chemical kinetic mechanisms, validated based on fundamental data from experiments like rapid compression machines and shock tubes, offer reasonably accurate predictions of ignition timing; however utilizing these requires high computational cost making them impractical for use in engine control schemes. Empirically-derived correlations offer faster control, but are generally not valid beyond the narrow range of conditions over which they were derived. This study discusses initial work in the development of an ignition correlation based on a detailed chemical kinetic mechanism for three component gasoline surrogate, composed of n-heptane, iso-octane and toluene, or toluene reference fuel (TRF). Simulations are conducted over a wide range of conditions including temperature, pressure, equivalence ratio and dilution for a range of tri-component blends in order to produce ignition delay time and investigate trends in ignition as pressure, equivalence ratio, temperature and fuel reactivity are varied. A modified, Arrhenius-based power law formulation will be used in a future study to fit the computed ignition delay times.

A Study on Fundamental Combustion Properties of Oxymethylene Ether-2

2021 ◽  
Author(s):  
John N. Ngugi ◽  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
Markus Köhler ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reaction Mechanisms ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Sensitivity Analyses ◽  
Chain Reactions ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times

Abstract Oxymethylene ethers (OMEn, n = 1–5) are a promising class of synthetic fuels that have the potential to be used as additives or substitutes to diesel in compression ignition engines. A comprehensive understanding of their combustion properties is required for their safe and efficient utilization. In this study, the results of a combined experimental and modeling work on oxidation of OME2 are reported: (i) Ignition delay time measurements of stoichiometric OME2 / synthetic air mixtures diluted 1:5 with nitrogen using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) laminar flame speeds of OME2 / air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. The experimental data sets obtained have been used for validation of a detailed reaction mechanisms of OME2. The results of ignition delay times showed that OME2 exhibits a two-stage ignition in the lower temperature region. There is a good match of the measured data compared to the predicted ones using three reaction mechanisms from the literature. The mechanism from Cai et al. (2020) best predicted the temperature and pressure dependence of ignition delay times. For laminar flame speeds, the experimental data were well matched by the mechanism from Ren et al. (2019) at p = 1, 3, and 6 bar and for all equivalence ratios considered. From sensitivity analyses calculations, it was observed that chain reactions involving small radicals, i.e., H, O, OH, HO2, and CH3 control the oxidation of OME2. The comparison of the results of this work and our previous work (Ngugi et al. (2021)) on OME1 show that these two fuels have similar oxidation pathways. The results obtained in this work will contribute to a better understanding of the combustion of oxymethylene ethers, and thus, to the design and optimization of burners and engines as well.

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.

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.

A Study On Fundamental Combustion Properties of Oxymethylene Ether-2

2021 ◽  
Author(s):  
John Mburu Ngugi ◽  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
Markus Köhler ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Sensitivity Analyses ◽  
Chain Reactions ◽  
Design And Optimization ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times

Abstract Oxymethylene ethers (OMEn, n=1-5) are a promising class of synthetic fuels that have the potential to be used as diesel additives or substitutes. A comprehensive understanding of their combustion properties is required for their safe and efficient utilization. In this study, a combined experimental and modeling work on oxidation of OME2 is reported: (i) Ignition delay time measurements of stoichiometric OME2 / synthetic air mixtures diluted 1:5 with nitrogen using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) laminar flame speeds of OME2 / air mixtures using the cone angle method at pressures of 1, 3 and 6 bar. The experimental data obtained have been used for validation of three detailed reaction mechanisms of OME2. The results of ignition delay times showed that OME2 exhibits a two-stage ignition in the lower temperature region. The mechanism from Cai et al. (2020) best predicted the temperature and pressure dependence of ignition delay times. For laminar flame speeds, the experimental data were well matched by the mechanism from Ren et al. (2019) for all the conditions of pressures and equivalence ratios considered. From sensitivity analyses, it was observed that chain reactions involving small radicals, i.e., H, O, OH, HO2, and CH3 control the oxidation of OME2. The results obtained in this work will contribute to a better understanding of the combustion of oxymethylene ethers, and thus, to the design and optimization of burners and engines as well.

Theoretical Prediction of Laminar Burning Speed and Ignition Delay of Gas to Liquid Fuel

2016 ◽  
Author(s):  
Guangying Yu ◽  
Omid Askari ◽  
Fatemeh Hadi ◽  
Ziyu Wang ◽  
Hameed Metghalchi ◽  
...  
Keyword(s):  
Chemical Kinetics ◽  
Ignition Delay ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Delay Times ◽  
Chemical Kinetic Mechanism ◽  
Gas To Liquid ◽  
Laminar Burning Speed

Gas to Liquid (GTL), an alternative synthetic jet fuel derived from natural gas has gained significant attention recently due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay time, laminar burning speed, and emission characteristics have been experimentally studied. However, the development of chemical kinetics mechanism to predict those parameters for GTL fuel is still in its early stage. In this work, a detailed kinetics model (DKM) has been developed based on the chemical kinetics reported for GTL surrogate fuels. The DKM is applied to the chemical kinetic mechanism of 597 species and 3853 reactions. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL and its three surrogates over a wide range of initial temperature, pressure and equivalence ratio. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the CANTERA freely propagating 1D flame code is used in conjunction with the chemical kinetic mechanism to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions.

A Micro Gas Turbine Fuelled by Methane-Hydrogen Blends

2012 ◽  
Vol 232 ◽  
pp. 792-796 ◽  
Author(s):  
Fabrizio Reale ◽  
Raffaela Calabria ◽  
Fabio Chiariello ◽  
Rocco Pagliara ◽  
Patrizio Massoli
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Hydrogen Oxidation ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Combustion Efficiency ◽  
Point Of View ◽  
Combustion Model ◽  
Numerical Computations ◽  
Micro Gas Turbine

The combustion efficiency and the gaseous emission of a 100 kWe MGT, designed for working with natural gas but fuelled with blends containing up to 10% of hydrogen is investigated. A critical comparison between experimental data and results of the CFD analysis of the combustor is discussed. The k-epsilon RANS turbulence model and the Finite Rate – Eddy Dissipation combustion model were used in the numerical computations. The chemical kinetic mechanisms embedded were the 2-step Westbrook and Dryer for methane oxidation, 1-step Westbrook and Dryer for hydrogen oxidation and the Zeldovich mechanism for NO formation. The experimental data and numerical computations are in agreement within the experimental accuracy for NO emissions. Regarding CO, there is a significant deviation between experimental and computational data due to the scarce predictive capability of the simple two steps kinetic mechanism was adopted. From a practical point of view, the possibility of using fuels with a similar Wobbe index was confirmed. In particular the addiction of 10 % of hydrogen to pure methane doesn’t affect the behavior of the micro gas turbine either in terms of NO or CO emissions.

Alternative Fuels Based on Biomass: An Experimental and Modeling Study of Ethanol Co-Firing to Natural Gas

2014 ◽  
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 co-firing. 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 (micro gas turbines) or centralized gas turbine units, neat, or co-fired with gaseous fuels like natural gas and biogas — is discussed, besides its role within the transport sector. 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 CFD (computational fluid dynamics) codes. Therefore, a detailed experimental and modeling study of ethanol co-firing to natural gas 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 natural gas, ethanol, and ethanol co-fired to natural gas.

Sign in / Sign up

Export Citation Format

Share Document