scholarly journals On the laminar combustion characteristics of natural gas-syngas-air mixtures

2018 ◽  
Vol 22 (5) ◽  
pp. 2077-2086 ◽  
Author(s):  
Ning Zhang ◽  
Jie Liu ◽  
Junle Wang ◽  
Hongbo Zhao
Keyword(s):  
Thermal Diffusivity ◽  
Laminar Flame ◽  
Hydrodynamic Instability ◽  
Flame Temperature ◽  
Laminar Flame Speed ◽  
Flame Thickness ◽  
Mixture Density ◽  
Flame Instability ◽  
Co Addition ◽  
Flame Instabilities

In this study, the effects of hydrogen and CO addition on the laminar flame speed and flame instabilities of CH4/air mixture are investigated experimentally and numerically. Results show that laminar flame speeds increase almost linearly with the addition of hydrogen, which is mainly caused by the increase of the flame temperature and the thermal diffusivity of the mixture. However, it de-creases with the increase of the pressure, which is mainly due to the increase of the mixture density and the enhancement of the termination reactions. The hydrodynamic instability is increased with the increase of hydrogen ratio and pressure, which is due to the reduction of the flame thickness. With the increase of hydrogen fractions and pressure, the Markstein lengths decrease obviously, which means the flame instability is enhanced. The addition of CO has little effect on the flame speeds and flame instabilities.

A Numerical Study on the Reactivity of Biogas/Reformed-Gas/Air and Methane/Reformed-Gas/Air Mixtures at Gas Turbine Relevant Conditions

2016 ◽  
Author(s):  
Pablo Diaz Gomez Maqueo ◽  
Philippe Versailles ◽  
Gilles Bourque ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Gas Turbine ◽  
Laminar Flame ◽  
Numerical Study ◽  
Flame Temperature ◽  
Flame Speed ◽  
Flame Stability ◽  
Laminar Flame Speed ◽  
Fuel Reforming ◽  
Numerical Work ◽  
Chemical Effects

This study investigates the increase in methane and biogas flame reactivity enabled by the addition of syngas produced through fuel reforming. To isolate thermodynamic and chemical effects on the reactivity of the mixture, the burner simulations are performed with a constant adiabatic flame temperature of 1800 K. Compositions and temperatures are calculated with the chemical equilibrium solver of CANTERA® and the reactivity of the mixture is quantified using the adiabatic, freely-propagating premixed flame, and perfectly-stirred reactors of the CHEMKIN-Pro® software package. The results show that the produced syngas has a content of up to 30 % H2 with a temperature up to 950 K. When added to the fuel, it increases the laminar flame speed while maintaining a burning temperature of 1800 K. Even when cooled to 300 K, the laminar flame speed increases up to 30 % from the baseline of pure biogas. Hence, a system can be developed that controls and improves biogas flame stability under low reactivity conditions by varying the fraction of added syngas to the mixture. This motivates future experimental work on reforming technologies coupled with gas turbine exhausts to validate this numerical work.

scholarly journals Catalytic Influence of Water Vapor on Lean Blowoff and NOx Reduction for Pressurised Swirling Syngas Flames

2017 ◽  
Author(s):  
Daniel Pugh ◽  
Philip Bowen ◽  
Andrew Crayford ◽  
Richard Marsh ◽  
Jon Runyon ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Reaction Rate ◽  
Catalytic Effect ◽  
Laminar Flame ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Stability Limit ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Water Loading

It has become increasingly cost-effective for the steel industry to invest in the capture of heavily carbonaceous BOF (Basic Oxygen Furnace) or converter gas, and use it to support the intensive energy demands of the integrated facility, or for surplus energy conversion in power plants. As industry strives for greater efficiency via ever more complex technologies, increased attention is being paid to investigate the complex behavior of by-product syngases. Recent studies have described and evidenced the enhancement of fundamental combustion parameters such as laminar flame speed due to the catalytic influence of H2O on heavily carbonaceous syngas mixtures. Direct formation of CO2 from CO is slow due to its high activation energy, and the presence of disassociated radical hydrogen facilitates chain branching species (such as OH), changing the dominant path for oxidation. The observed catalytic effect is non-monotonic, with the reduction in flame temperature eventually prevailing, and overall reaction rate quenched. The potential benefits of changes in water loading are explored in terms of delayed lean blowoff, and primary emission reduction in a premixed turbulent swirling flame, scaled for practical relevance at conditions of elevated temperature (423 K) and pressure (0.1–0.3 MPa). Chemical kinetic models are used initially to characterize the influence that H2O has on the burning characteristics of the fuel blend employed, modelling laminar flame speed and extinction strain rate across an experimental range with H2O vapor fraction increased to eventually diminish the catalytic effect. These modelled predictions are used as a foundation to investigate the experimental flame. OH* chemiluminescence and OH planar laser induced fluorescence (PLIF) are employed as optical diagnostic techniques to analyze changes in heat release structure resulting from the experimental variation in water loading. A comparison is made with a CH4/air flame and changes in lean blow off stability limits are quantified, measuring the incremental increase in air flow and again compared against chemical models. The compound benefit of CO and NOx reduction is quantified also, with production first decreasing due to the thermal effect of H2O addition from a reduction in flame temperature, coupled with the potential for further reduction from the change in lean stability limit. Power law correlations have been derived for change in pressure, and equivalent water loading. Hence, the catalytic effect of H2O on reaction pathways and reaction rate predicted and observed for laminar flames, are compared against the challenging environment of turbulent, swirl-stabilized flames at elevated temperature and pressure, characteristic of piratical systems.

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

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.

scholarly journals Catalytic Influence of Water Vapor on Lean Blow-Off and NOx Reduction for Pressurized Swirling Syngas Flames

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Daniel Pugh ◽  
Philip Bowen ◽  
Andrew Crayford ◽  
Richard Marsh ◽  
Jon Runyon ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Reaction Rate ◽  
Catalytic Effect ◽  
Laminar Flame ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Stability Limit ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Water Loading

It has become increasingly cost-effective for the steel industry to invest in the capture of heavily carbonaceous basic oxygen furnace or converter gas, and use it to support the intensive energy demands of the integrated facility, or for surplus energy conversion in power plants. As industry strives for greater efficiency via ever more complex technologies, increased attention is being paid to investigate the complex behavior of by-product syngases. Recent studies have described and evidenced the enhancement of fundamental combustion parameters such as laminar flame speed due to the catalytic influence of H2O on heavily carbonaceous syngas mixtures. Direct formation of CO2 from CO is slow due to its high activation energy, and the presence of disassociated radical hydrogen facilitates chain branching species (such as OH), changing the dominant path for oxidation. The observed catalytic effect is nonmonotonic, with the reduction in flame temperature eventually prevailing, and overall reaction rate quenched. The potential benefits of changes in water loading are explored in terms of delayed lean blow-off (LBO), and primary emission reduction in a premixed turbulent swirling flame, scaled for practical relevance at conditions of elevated temperature (423 K) and pressure (0.1–0.3 MPa). Chemical kinetic models are used initially to characterize the influence that H2O has on the burning characteristics of the fuel blend employed, modeling laminar flame speed and extinction strain rate across an experimental range with H2O vapor fraction increased to eventually diminish the catalytic effect. These modeled predictions are used as a foundation to investigate the experimental flame. OH* chemiluminescence and OH planar laser-induced fluorescence (PLIF) are employed as optical diagnostic techniques to analyze changes in heat release structure resulting from the experimental variation in water loading. A comparison is made with a CH4/air flame and changes in LBO stability limits are quantified, measuring the incremental increase in air flow and again compared against chemical models. The compound benefit of CO and NOx reduction is quantified also, with production first decreasing due to the thermal effect of H2O addition from a reduction in flame temperature, coupled with the potential for further reduction from the change in lean stability limit. Power law correlations have been derived for change in pressure, and equivalent water loading. Hence, the catalytic effect of H2O on reaction pathways and reaction rate predicted and observed for laminar flames are appraised within the challenging environment of turbulent, swirl-stabilized flames at elevated temperature and pressure, characteristic of practical systems.

Study of Fuel Composition Effects on Flashback Using a Confined Jet Flame Burner

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Brendan Shaffer ◽  
Zhixuan Duan ◽  
Vincent McDonell
Keyword(s):  
Natural Gas ◽  
Laminar Flame ◽  
Flame Temperature ◽  
Flame Speed ◽  
Fuel Composition ◽  
Laminar Flame Speed ◽  
Processing Scheme ◽  
High Hydrogen ◽  
Jet Flame ◽  
Wide Range

Flashback is the main operability issue associated with converting lean, premixed combustion systems from operation on natural gas to operation on high hydrogen content fuels. Most syngas fuels contain some amount of hydrogen (15–100%) depending on the fuel processing scheme. With this variability in the composition of syngas, the question of how fuel composition impacts flashback propensity arises. To address this question, a jet burner configuration was used to develop systematic data for a wide range of compositions under turbulent flow conditions. The burner consisted of a quartz burner tube confined by a larger quartz tube. The use of quartz allowed visualization of the flashback processes occurring. Various fuel compositions of hydrogen, carbon monoxide, and natural gas were premixed with air at equivalence ratios corresponding to constant adiabatic flame temperatures (AFT) of 1700 K and 1900 K. Once a flame was stabilized on the burner, the air flow rate would be gradually reduced while holding the AFT constant via the equivalence ratio until flashback occurred. Schlieren and intensified OH* images captured at high speeds during flashback allowed some additional understanding of what is occurring during the highly dynamic process of flashback. Confined and unconfined flashback data were analyzed by comparing data collected in the present study with existing data in the literature. A statistically designed test matrix was used which allows analysis of variance of the results to be carried out, leading to correlation between fuel composition and flame temperature with (1) critical flashback velocity gradient and (2) burner tip temperature. Using the burner tip temperature as the unburned temperature in the laminar flame speed calculations showed increased correlation of the flashback data and laminar flame speed as opposed to when the actual unburned gas temperature was used.

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

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.

Study of Fuel Composition Effects on Flashback Using a Confined Jet Flame Burner

2012 ◽  
Author(s):  
Brendan Shaffer ◽  
Zhixuan Duan ◽  
Vincent McDonell
Keyword(s):  
Natural Gas ◽  
Laminar Flame ◽  
Flame Temperature ◽  
Flame Speed ◽  
Fuel Composition ◽  
Laminar Flame Speed ◽  
Processing Scheme ◽  
High Hydrogen ◽  
Jet Flame ◽  
Wide Range

Flashback is the main operability issue associated with converting lean, premixed combustion systems from operation on natural gas to operation on high hydrogen content fuels. Most syngas fuels contain some amount of hydrogen (15–100%) depending on the fuel processing scheme. With this variability in the composition of syngas, the question of how fuel composition impacts flashback propensity arises. To address this question, a jet burner configuration was used to develop systematic data for a wide range of compositions under turbulent flow conditions. The burner consisted of a quartz burner tube confined by a larger quartz tube. The use of quartz allowed visualization of the flashback processes occurring. Various fuel compositions of hydrogen, carbon monoxide, and natural gas were premixed with air at equivalence ratios corresponding to constant adiabatic flame temperatures (AFT) of 1700 K and 1900 K. Once a flame was stabilized on the burner, the air flow rate would be gradually reduced while holding the AFT constant via the equivalence ratio until flashback occurred. Schlieren and intensified OH* images captured at high speeds during flashback allowed some additional understanding of what is occurring during the highly dynamic process of flashback. Confined and unconfined flashback data were analyzed by comparing data collected in the present study with existing data in the literature. A statistically designed test matrix was used which allows analysis of variance of the results to be carried out, leading to correlation between fuel composition and flame temperature with (1) critical flashback velocity gradient and (2) burner tip temperature. Using the burner tip temperature as the unburned temperature in the laminar flame speed calculations showed increased correlation of the flashback data and laminar flame speed as opposed to when the actual unburned gas temperature was used.

Phenomenological Analysis of Combustion of Gaseous Fuels to Measure the Energy Quality and the Capacity to Produce Work in Spark Ignition Engines.

2020 ◽  
Author(s):  
Juan Pablo GOMEZ MONTOYA ◽  
Andres Amell
Keyword(s):  
Energy Density ◽  
Compression Ratio ◽  
Laminar Flame ◽  
Flame Temperature ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Adiabatic Flame Temperature ◽  
Gaseous Fuels ◽  
Combustion Properties ◽  
Si Engines

Abstract Combustion at the knocking threshold was tested using fuels with different methane numbers (MN) in a modified SI engine, with high compression ratio (CR) and high turbulence intensity to the combustion process; fuels were tested in a CFR engine to measure MN and critical compression ratio (CCR); in both engines test were performed just into the knocking threshold. Is proposed that MN to gaseous fuels will be considered in similar way than octane number (ON) to liquid fuels to indicate the energy quality and the capacity to produce work. According to the tests biogas has better combustion properties than the others fuels; biogas is the fuel with the highest knocking resistance; biogas is the fuel with the best energy quality measured with the energy density and combustion temperature; biogas has the highest capacity to produce work in SI engines, because its high MN, low energy density, low laminar flame speed and low adiabatic flame temperature. Fuel combustion phenomenological characteristics were compared using CCR versus: output power, generating efficiency, energy density, laminar flame speed and adiabatic flame temperature. It is suggested that the strategies to suppress knocking are the key to improve the performance of SI engines; knocking is the engine limit to power generation in SI engines and quantum thermal efficiency is defined at this condition.

scholarly journals Numerical study of the laminar flame propagation in ethane-air mixtures

2014 ◽  
Vol 12 (3) ◽  
pp. 391-402 ◽  
Author(s):  
Venera Giurcan ◽  
Domnina Razus ◽  
Maria Mitu ◽  
Dumitru Oancea
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Laminar Flame ◽  
Numerical Study ◽  
Flame Temperature ◽  
Chemical Species ◽  
Main Reaction ◽  
Flame Thickness ◽  
Wide Range

AbstractThe structure of premixed free one-dimensional laminar ethane-air flames was investigated by means of numerical simulations performed with a detailed mechanism (GRI-Mech version 3.0) by means of COSILAB package. The work provides data on ethane-air mixtures with a wide range of concentrations ([C2H6] = 3.0–9.5 vol.%) at initial temperatures between 300 and 550 K and initial pressures between 1 and 10 bar. The simulations deliver the laminar burning velocities and the profiles of temperature, chemical species concentrations and heat release rate across the flame front. The predicted burning velocities match well the burning velocities measured in various conditions, reported in literature. The influence of initial concentration, pressure and temperature of ethane-air mixtures on maximum flame temperature, heat release rate, flame thickness and peak concentrations of main reaction intermediates is examined and discussed.

Sign in / Sign up

Export Citation Format

Share Document