Structure and Laminar Flame Speed of an Ammonia/Methane/Air Premixed Flame under Varying Pressure and Equivalence Ratio

Abstract New laminar flame speed experiments have been collected for multiple alternative liquid fuels. Understanding the combustion characteristics of these synthetic fuels is an important step in developing new chemical kinetics mechanisms that can be applied to real fuels. Included in this study are two synthetic Jet fuels: Syntroleum S-8 and Shell GTL. The precise composition of these fuels is known to change from sample to sample. Since these are low vapor pressure fuels, there are additional uncertainties in their introduction into gas-phase mixtures, leading to uncertainty in the mixture equivalence ratio. An in-situ laser absorption technique was implemented to verify the procedure for filling the vessel and to minimize and quantify the uncertainty in the experimental equivalence ratio. The diagnostic utilized a 3.39-μm HeNe laser in conjunction with Beer’s Law. The resulting spherically expanding flame experiments were conducted over a range of equivalence ratios from φ = 0.7 to φ = 1.5 at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure constant-volume vessel at Texas A&M University. The experimental results show that both fuels have similar flame speeds with a peak value just under 60 cm/s. However, it is shown that when comparing the results from different data sets for these real fuels, equivalence ratio is not necessarily the best parameter to use. Fuel mole fraction may be a better parameter to use as it is independent of the average fuel molecule or fuel surrogate used to calculate equivalence ratio in these real fuel/air mixtures.

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Laminar flame speed of soy and canola biofuels

CT&F - Ciencia Tecnología y Futuro ◽

10.29047/01225383.223 ◽

2012 ◽

Vol 4 (5) ◽

pp. 75-83 ◽

Cited By ~ 2

Author(s):

Juan-Sebastián Gómez-Meyer ◽

Subramanyam R Gollahalli ◽

Ramkumar N. Parthasarathy ◽

Jabid-Eduardo Quiroga

Keyword(s):

Flame Propagation ◽

Equivalence Ratio ◽

Laminar Flame ◽

Turbulent Flames ◽

Flame Speed ◽

Thermochemical Property ◽

Laminar Flame Speed ◽

Hot Air ◽

Maximum Value ◽

Canola Oils

In this article, the flame speed values determined experimentally for laminar premixed flames of the vapors of two biofuels in air are presented. The laminar flame speed is a fundamental thermochemical property of fuels, and is essential for analyzing the flame propagation in practical devices, even those employing turbulent flames. The fuels obtained from transesterification of soy and canola oils are tested. Also, the diesel flames are studied to serve as a baseline for comparison. The experiments are performed with a tubular burner; pre-vaporized fuel is mixed with hot air and is ignited. The flame speed is determined at fuel-equivalence ratios of 1; 1,1 and 1,2 by recording the geometry of the flame. The experimental results show that the flame speed of biofuels is lower by about 15% than that of diesel. Also, the maximum value of flame speed is obtained at an equivalence ratio of approximately 1,1.

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Laminar Flame Speed Experiments of Alternative Liquid Fuels

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4045346 ◽

2019 ◽

Vol 142 (1) ◽

Author(s):

Charles L. Keesee ◽

Bing Guo ◽

Eric L. Petersen

Keyword(s):

Equivalence Ratio ◽

Laminar Flame ◽

Initial Conditions ◽

Synthetic Jet ◽

Flame Speed ◽

Liquid Fuels ◽

Jet Fuels ◽

Laminar Flame Speed ◽

Synthetic Fuels ◽

Best Parameter

Abstract New laminar flame speed experiments have been collected for two alternative liquid fuels. Understanding the combustion characteristics of these synthetic fuels is an important step in developing new chemical kinetics mechanisms that can be applied to real fuels. Included in this study are two synthetic Jet fuels: Syntroleum S-8 and Shell GTL. The precise composition of these fuels is known to change from sample to sample. Since these are low-vapor pressure fuels, there are additional uncertainties in their introduction into gas-phase mixtures, leading to uncertainty in the mixture equivalence ratio. An in-situ laser absorption technique was implemented to verify the procedure for filling the vessel and to minimize and quantify the uncertainty in the experimental equivalence ratio. The diagnostic utilized a 3.39-μm HeNe laser in conjunction with Beer's law. The resulting spherically expanding, laminar flame experiments were conducted over a range of equivalence ratios from φ = 0.7 to φ = 1.5 at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure (HTHP) constant-volume vessel at Texas A&M University. The experimental results show that both fuels have similar flame speeds with a peak value just under 60 cm/s. However, it is shown that when comparing the results from different datasets for these real fuels, equivalence ratio may not be the best parameter to use. Fuel mole fraction may be a better parameter to use as it is independent of the average fuel molecule or fuel surrogate used to calculate equivalence ratio in these real fuel/air mixtures.

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Experimental Study on Laminar Flame Speeds and Markstein Length of Methane-Air Mixtures at Atmospheric Conditions

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.699.714 ◽

2014 ◽

Vol 699 ◽

pp. 714-719

Author(s):

Alaeldeen Altag Yousif ◽

Shaharin Anwar Sulaiman

Keyword(s):

High Speed ◽

Equivalence Ratio ◽

Laminar Flame ◽

Burning Velocity ◽

Ambient Pressure ◽

Flame Speed ◽

Laminar Flame Speed ◽

Atmospheric Conditions ◽

Laminar Burning Velocity ◽

Markstein Length

Accurate value of laminar flame speed is an important parameter of combustible mixtures. In this respect, experimental data are very useful for modeling improvement and validating chemical kinetic mechanisms. To achieve this, an experimental characterization on spherically expanding flames propagation of methane-air mixtures were carried out. Tests were conducted in constant volume cylindrical combustion chamber to measure stretched, unstretched laminar flame speed, laminar burning velocity, and flame stretch effect as quantified by the associated Markstein lengths. The mixtures of methane-air were ignited at extensive ranges of lean-to-rich equivalence ratios, under ambient pressure and temperature. This is achieved by high speed schlieren cine-photography for flames observation in the vessel. The results showed that the unstretched laminar burning velocity increased and the peak value of the unstretched laminar burning velocity shifted to the richer mixture side with the increase of equivalence ratio. The flame propagation speed showed different trends at different equivalence ratio for tested mixtures. It was found that the Markstein length was increased with the increase of equivalence ratio.

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Multi-Dimensional CFD Simulations of Knocking Combustion in a CFR Engine

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2017-3599 ◽

2017 ◽

Cited By ~ 4

Author(s):

Pinaki Pal ◽

Yunchao Wu ◽

Tianfeng Lu ◽

Sibendu Som ◽

Yee Chee See ◽

...

Keyword(s):

Experimental Data ◽

Flame Front ◽

Octane Number ◽

Equivalence Ratio ◽

Laminar Flame ◽

Equation Model ◽

Flame Speed ◽

Lookup Table ◽

Laminar Flame Speed ◽

Skeletal Mechanism

Knock is a major impediment to achieving higher efficiency in Spark-Ignition (SI) engines. The recent trends of boosting, downsizing and downspeeding have exacerbated this issue by driving engines toward higher power density and higher load duty cycles. Apart from the engine operating conditions, fuel anti-knock quality is a major determinant of the knocking tendency in engines, as quantified by its octane number (ON). The ON of a fuel is based on an octane scale which is defined according to the standard octane rating methods for Research Octane Number (RON) and Motor Octane Number (MON). These tests are performed in a single cylinder Cooperative Fuel Research (CFR) engine. In the present work, a numerical approach was developed based on multidimensional computational fluid dynamics (CFD) to predict knocking combustion in a CFR engine. The G-equation model was employed to track the propagation of the turbulent flame front and a multi-zone model based on temperature and equivalence ratio was used to capture auto-ignition in the endgas ahead of the flame front. Furthermore, a novel methodology was developed wherein a lookup table generated from a chemical kinetic mechanism could be employed to provide laminar flame speed as an input to the G-equation model, instead of using empirical correlations. To account for fuel chemistry effects accurately and lower the computational cost, a compact 121-species primary reference fuel (PRF) skeletal mechanism was developed from a more detailed gasoline surrogate mechanism using the directed relation graph assisted sensitivity analysis (DRGASA) reduction technique. Extensive validation of the skeletal mechanism was performed against experimental data available in the literature for both homogeneous ignition delay and laminar flame speed. The skeletal mechanism was used to generate the lookup tables for laminar flame speed as a function of pressure, temperature and equivalence ratio. The engine CFD model incorporating the skeletal mechanism was employed to perform numerical simulations under RON and MON conditions for different PRFs. Parametric tests were conducted at different compression ratios and the predicted values of critical compression ratio (at knock onset), delineating the boundary between “no knock” and “knock”, were found to be in good agreement with the available experimental data. The virtual CFR engine model was, therefore, demonstrated to be capable of adequately capturing the sensitivity of knock propensity to fuel chemistry.

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The adiabatic flame temperature and laminar flame speed of methane premixed flames at varying pressures

Acta periodica technologica ◽

10.2298/apt1950220s ◽

2019 ◽

pp. 220-227

Author(s):

Ahmad Sakhrieh

Keyword(s):

Equivalence Ratio ◽

Initial Temperature ◽

Laminar Flame ◽

Flame Temperature ◽

Flame Speed ◽

Pressure Increase ◽

Stoichiometric Ratio ◽

Laminar Flame Speed ◽

Adiabatic Flame Temperature ◽

Percent Increase

This paper studies the influence of equivalence ratio, pressure and initial temperature on adiabatic flame temperature and laminar flame speed of methane-air mixture. The results indicate that adiabatic flame temperature is weakly correlated with pressure. The adiabatic flame temperature increases only by about 50?C as a result of 30 bar pressure increase. The flame speed is inversely proportional to pressure. The maximum adiabatic flame temperature and flame speed occur at the stoichiometric ratio, ?=1. The percent increase in the flame speed was about 400% when the initial temperature of the mixture is increased from 25?C to 425?C.

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Laminar Flame Speed Measurements of Kerosene-Based Fuels Accounting for Uncertainties in Mixture Average Molecular Weight

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-15527 ◽

2020 ◽

Author(s):

Charles L. Keesee ◽

Bing Guo ◽

Eric L. Petersen

Keyword(s):

Molecular Weight ◽

Equivalence Ratio ◽

Laminar Flame ◽

Initial Conditions ◽

Average Molecular Weight ◽

Flame Speed ◽

Liquid Fuels ◽

Laminar Flame Speed ◽

Noticeable Effect ◽

Data Points

Abstract New laminar flame speed experiments have been collected for some kerosene-based liquid fuels: Jet-A, RP-1, and Diesel Fuel #2. Accurately understanding the combustion characteristics of these, and all kerosene-based fuels in general, is an important step in developing new chemical kinetics mechanisms that can be applied to these fuels. It is well known that the precise composition of these fuels changes from one production batch to the next, leading to significant uncertainty in the mixture average properties. For example, uncertainty in a fuel blend’s molecular weight can have a noticeable effect on defining an equivalence ratio for a typical fuel-air mixture, on the order of 15%. Because of these uncertainties, fuel mole fraction, Xfuel, is shown to be a more appropriate parameter for comparison between different batches of fuel. Additionally, a strong linear correlation was detected between the burned-gas Markstein length and the equivalence ratio. This correlation is shown to be useful in determining the acceptability and accuracy of individual data points. Spherically expanding flames were measured over a range of fuel mole fractions corresponding to equivalence ratios of φ = 0.7 to φ = 1.5, at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure constant volume vessel at Texas A&M University. These new results are compared with the limited set of laminar flame speed data currently available in the literature for this fuel.

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Experimental and Kinetic Evaluation of Pressurized Lean Premixed Hydrogen-Air Flame Stability With Carbon Dioxide and Steam Dilution

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-16083 ◽

2020 ◽

Author(s):

Jon Runyon ◽

Daniel Pugh ◽

Anthony Giles ◽

Burak Goktepe ◽

Philip Bowen ◽

...

Keyword(s):

Carbon Dioxide ◽

Strain Rate ◽

Equivalence Ratio ◽

Laminar Flame ◽

Flame Temperature ◽

Flame Speed ◽

Flame Stability ◽

Laminar Flame Speed ◽

Adiabatic Flame Temperature ◽

Extinction Strain Rate

Abstract A study has been undertaken to experimentally and numerically evaluate the use of carbon dioxide or steam as premixed fuel additive in hydrogen-air flames to aid in the development of lean premixed (LPM) swirl burner technology for low NOx operation. Chemical kinetics modelling indicates that the use of CO2 or steam in the premixed reactants reduces H2-air laminar flame speed and adiabatic flame temperature within the well-characterized range of preheated LPM methane-air flames, albeit in markedly different proportions; for example, nearly 65 %vol CO2 as a proportion of the fuel is required for a reduction in laminar flame speed to equivalent CH4-air values, while approximately 30 %vol CO2 in the fuel is required for an equivalent reduction in adiabatic flame temperature, significantly impacted by the increased heat capacity of CO2. The 2nd generation high-pressure generic swirl burner, designed for use with LPM CH4-air, was therefore utilized to experimentally investigate the influence of CO2 and steam dilution on pressurized (up to 250 kW/MPa), preheated (up to 573 K), LPM H2-air flame stability using high-speed OH* chemiluminescence. In addition, exhaust gas emissions, such as NOx and CO, have been measured in comparison with equivalent thermal power conditions for CH4-air flames, showing that low NOx operation can be achieved. Furthermore, pure LPM H2-air flames are characterized for the first time in this burner, stabilized at low equivalence ratio (approximately 0.24) and increased Reynolds number at atmospheric pressure compared to the stable CH4-air flame (equivalence ratio of 0.55). The influence of extinction strain rate is suggested to characterize, both experimentally and numerically, the observed lean flame behavior, in particular as extinction strain rate has been shown to be non-monotonic with pressure for highly-reactive and diffuse fuels such as hydrogen.

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Experimental Investigation of Laminar Flame Speeds for Medium Calorific Gas With Various Amounts of Hydrogen and Carbon Monoxide Content at Gas Turbine Temperatures

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-22275 ◽

2010 ◽

Cited By ~ 3

Author(s):

Ivan R. Sigfrid ◽

Ronald Whiddon ◽

Robert Collin ◽

Jens Klingmann

Keyword(s):

Gas Turbine ◽

Equivalence Ratio ◽

Room Temperature ◽

Laminar Flame ◽

Chemical Kinetic ◽

Flame Speed ◽

Laminar Flame Speed ◽

Kinetic Mechanisms ◽

Group A ◽

Group B

It is expected that, in the future, gas turbines will be operated on gaseous fuels currently unutilized. The ability to predict the range of feasible fuels, and the extent to which existing turbines must be modified to accommodate these fuels, rests on the nature of these fuels in the combustion environment. Understanding the combustion behavior is aided by investigation of syngases of similar composition. As part of an ongoing project at the Lund University Departments of Thermal Power Engineering and Combustion Physics, to investigate syngases in gas turbine combustion, the laminar flame speed of five syngases (see table) have been measured. The syngases examined are of two groups. The first gas group (A), contains blends of H2, CO and CH4, with high hydrogen content. The group A gases exhibit a maximum flame speed at an equivalence ratio of approximately 1.4, and a flame speed roughly four times that of methane. The second gas group (B) contains mixtures of CH4 and H2 diluted with CO2. Group B gases exhibit maximum flame speed at an equivalence ratio of 1, and flame speeds about 3/4 that of methane. A long tube Bunsen-type burner was used and the conical flame was visualized by Schlieren imaging. The flame speeds were measured for a range of equivalence ratios using a constrained cone half-angle method. The equivalence ratio for measurements ranged from stable lean combustion to rich combustion for room temperature (25°C) and an elevated temperature representative of a gas turbine at full load (270°C). The experimental procedure was verified by methane laminar flame speed measurement; and, experimental results were compared against numerical simulations based on GRI 3.0, Hoyerman and San Diego chemical kinetic mechanisms using the DARS v2.02 combustion modeler. On examination, all measured laminar flame speeds at room temperature were higher than values predicted by the aforementioned chemical kinetic mechanisms, with the exception of group A gases, which were lower than predicted.

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Laminar Flame Speed Measurements of Kerosene-Based Fuels Accounting for Uncertainties in Mixture Average Molecular Weight

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4049886 ◽

2021 ◽

Vol 143 (4) ◽

Author(s):

Charles L. Keesee ◽

Bing Guo ◽

Eric L. Petersen

Keyword(s):

Molecular Weight ◽

Equivalence Ratio ◽

Laminar Flame ◽

Initial Conditions ◽

Average Molecular Weight ◽

Flame Speed ◽

Liquid Fuels ◽

Laminar Flame Speed ◽

Noticeable Effect ◽

Data Points

Abstract New laminar flame speed experiments have been collected for some kerosene-based liquid fuels: Jet-A, RP-1, and diesel fuel #2. Accurately understanding the combustion characteristics of these, and all kerosene-based fuels in general, is an important step in developing new chemical kinetics mechanisms that can be applied to these fuels. It is well known that the precise composition of these fuels changes from one production batch to the next, leading to significant uncertainty in the mixture average properties. For example, uncertainty in a fuel blend's molecular weight can have a noticeable effect on defining an equivalence ratio for a typical fuel–air mixture, of the order of 15%. Because of these uncertainties, fuel mole fraction, XFUEL, is shown to be a more appropriate parameter for comparison between different batches of fuel. Additionally, a strong linear correlation was detected between the burned-gas Markstein length and the equivalence ratio. This correlation is shown to be useful in determining the acceptability and accuracy of individual data points. Spherically expanding flames were measured over a range of fuel mole fractions corresponding to equivalence ratios of φ = 0.7 to φ = 1.5, at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure (HTHP) constant volume vessel at Texas A&M University. These new results are compared with the limited set of laminar flame speed data currently available in the literature for this fuel.

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