An Investigation on Laminar Flame Speed as Part of Needed Combustion Characteristics of Biomass-Based Syngas Fuels

2007 ◽  
Author(s):  
Marina Braun-Unkhoff ◽  
Thomas Kick ◽  
Peter Frank ◽  
Manfred Aigner
Keyword(s):  
Reaction Mechanisms ◽  
Co2 Sequestration ◽  
Alternative Fuels ◽  
Laminar Flame ◽  
Gas Mixtures ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Hydrogen Burning ◽  
Biogenic Gas ◽  
Wide Range

The present work reports on laminar flame speed measurements with biogenic gas mixtures over a wide range of parameters, such as preheat temperatures, pressure, equivalence ratio, and gas compositions. The biogenic gas mixtures were derived from gasification of ethanol and of corn silage as representatives for alternative fuels containing hydrogen and methane as major components (after CO2-sequestration), light hydrocarbons to some extent, and diluents such as nitrogen and carbon monoxide. In the present work, premixed flames were stabilized in a high pressure burner system at pressures up to 6 bars at preheat temperatures between 323 and 453 K and for equivalence ratios of φ = 0.5–1.6. In addition, a gas mixture of methane and hydrogen burning in air was investigated at atmospheric pressure. Furthermore, different detailed reaction mechanisms were used to predict the measured data. The trends and main features were captured by predictions applying different reaction mechanisms.

Laminar Flame Speed and Ignition Delay Time Data for the Kinetic Modeling of Hydrogen and Syngas Fuel Blends

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Michael C. Krejci ◽  
Olivier Mathieu ◽  
Andrew J. Vissotski ◽  
Sankaranarayanan Ravi ◽  
Travis G. Sikes ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Chemical Kinetics ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Elevated Pressures ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Delay Times

Laminar flame speeds and ignition delay times have been measured for hydrogen and various compositions of H2/CO (syngas) at elevated pressures and elevated temperatures. Two constant-volume cylindrical vessels were used to visualize the spherical growth of the flame through the use of a schlieren optical setup to measure the laminar flame speed of the mixture. Hydrogen experiments were performed at initial pressures up to 10 atm and initial temperatures up to 443 K. A syngas composition of 50/50 by volume was chosen to demonstrate the effect of carbon monoxide on H2-O2 chemical kinetics at standard temperature and pressures up to 10 atm. All atmospheric mixtures were diluted with standard air, while all elevated-pressure experiments were diluted with a He:O2 ratio of 7:1 to minimize instabilities. The laminar flame speed measurements of hydrogen and syngas are compared to available literature data over a wide range of equivalence ratios, where good agreement can be seen with several data sets. Additionally, an improved chemical kinetics model is shown for all conditions within the current study. The model and the data presented herein agree well, which demonstrates the continual, improved accuracy of the chemical kinetics model. A high-pressure shock tube was used to measure ignition delay times for several baseline compositions of syngas at three pressures across a wide range of temperatures. The compositions of syngas (H2/CO) by volume presented in this study included 80/20, 50/50, 40/60, 20/80, and 10/90, all of which are compared to previously published ignition delay times from a hydrogen-oxygen mixture to demonstrate the effect of carbon monoxide addition. Generally, an increase in carbon monoxide increases the ignition delay time, but there does seem to be a pressure dependency. At low temperatures and pressures higher than about 12 atm, the ignition delay times appear to be indistinguishable with an increase in carbon monoxide. However, at high temperatures the relative composition of H2 and CO has a strong influence on ignition delay times. Model agreement is good across the range of the study, particularly at the elevated pressures.

Flame Speed and Vapor Pressure of Biojet Fuel Blends

2013 ◽  
Author(s):  
Jeffrey D. Munzar ◽  
Bradley M. Denman ◽  
Rodrigo Jiménez ◽  
Ahmed Zia ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Vapor Pressure ◽  
Alternative Fuels ◽  
Laminar Flame ◽  
Flame Speed ◽  
Aviation Fuel ◽  
Laminar Flame Speed ◽  
Camelina Oil ◽  
Combustion Properties ◽  
Initial Comparison ◽  
Fuel Mixtures

An understanding of the fundamental combustion properties of alternative fuels is essential for their adoption as replacements for non-renewable sources. In this study, three different biojet fuel mixtures are directly compared to conventional Jet A-1 on the basis of laminar flame speed and vapor pressure. The biofuel is derived from camelina oil and hydrotreated to ensure consistent elemental composition with conventional aviation fuel, yielding a bioderived synthetic paraffinic kerosene (Bio-SPK). Two considered blends are biofuel and Jet A-1 mixtures, while the third is a 90% Bio-SPK mixture with 10% aromatic additives. Premixed flame speed measurements are conducted at an unburned temperature of 400K and atmospheric pressure using a jet-wall stagnation flame apparatus. Since the laminar flame speed cannot be studied experimentally, a strained (or reference) flame speed is used as the basis for the initial comparison. Only by using an appropriate surrogate fuel were the reference flame speed measurements extrapolated to zero flame strain, accomplished using a direct comparison of simulations to experiments. This method has been previously shown to yield results consistent with non-linear extrapolations. Vapor pressure measurements of the biojet blends are also made from 25 to 200°C using an isoteniscope. Finally, the biojet blends are compared to the Jet A-1 benchmark on the basis of laminar flame speed at different equivalence ratios, as well as on the basis of vapor pressure over a wide temperature range, and the suitability of a binary laminar flame speed surrogate for these biojet fuels is discussed.

Reduced Reaction Mechanisms for Methane and Syngas Combustion in Gas Turbines

2005 ◽  
Author(s):  
N. Slavinskaya ◽  
M. Braun-Unkhoff ◽  
P. Frank
Keyword(s):  
Heat Release ◽  
Turbulent Combustion ◽  
Reaction Mechanisms ◽  
Gas Turbines ◽  
Laminar Flame ◽  
Laminar Flame Speed ◽  
Preheat Temperature ◽  
Reduced Mechanism ◽  
Wide Range ◽  
Syngas Combustion

Two reduced reaction mechanisms were established which predict reliably for pressures up to about 20 bar the heat release for different syngas mixtures including initial concentrations of methane. The mechanisms were validated on the base of laminar flame speed data covering a wide range of preheat temperature, pressure and fuel-air mixtures. Additionally, a global reduced mechanism for syngas, which comprises only two steps, was developed and validated, too. This global reduced and validated mechanism can be incorporated into CFD codes for modelling turbulent combustion in stationary gas turbines.

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.

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.

Chemistry-Based Laminar Flame Speed Correlations for a Wide Range of Engine Conditions for Iso-Octane, n-Heptane, Toluene and Gasoline Surrogate Fuels

2017 ◽  
Author(s):  
Alessandro D'Adamo ◽  
Marco Del Pecchia ◽  
Sebastiano Breda ◽  
Fabio Berni ◽  
Stefano Fontanesi ◽  
...  
Keyword(s):  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Surrogate Fuels ◽  
Wide Range

Laminar Flame Speed and Ignition Delay Time Data for the Kinetic Modeling of Hydrogen and Syngas Fuel Blends

2012 ◽  
Author(s):  
M. C. Krejci ◽  
O. Mathieu ◽  
A. J. Vissotski ◽  
S. Ravi ◽  
T. G. Sikes ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Ignition Delay ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Elevated Pressures ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Delay Times

Laminar flame speeds and ignition delay times have been measured for hydrogen and various compositions of H2/CO (syngas) at elevated pressures and elevated temperatures. Two constant-volume cylindrical vessels were used to visualize the spherical growth of the flame through the use of a schlieren optical setup to measure the laminar flame speed of the mixture. Hydrogen experiments were performed at initial pressures up to 10 atm and initial temperatures up to 443 K. A syngas composition of 50/50 by volume was chosen to demonstrate the effect of carbon monoxide on H2−O2 chemical kinetics at standard temperature and pressures up to 10 atm. All atmospheric mixtures were diluted with standard air, while all elevated-pressure experiments were diluted with a He:O2 of 7:1 to minimize instabilities. The laminar flame speed measurements of hydrogen and syngas are compared to available literature data over a wide range of equivalence ratios where good agreement can be seen with several data sets. Additionally, an improved chemical kinetics model is shown for all conditions within the current study. The model and the data presented herein agree well, which demonstrates the continual, improved accuracy of the chemical kinetic model. A high-pressure shock tube was used to measure ignition delay times for several baseline compositions of syngas at three pressures across a wide range of temperatures. The compositions of syngas (H2/CO) by volume presented in this study included 80/20, 50/50, 40/60, 20/80, and 10/90, all of which are compared to previously published ignition delay times from a hydrogen-oxygen mixture to demonstrate the effect of carbon monoxide addition. Generally, an increase in carbon monoxide increases the ignition delay time, but there does seem to be a pressure dependency. At low temperatures and pressures higher than about 12 atm, the ignition delay times appear to be indistinguishable with an increase in carbon monoxide. However, at high temperatures the relative composition of H2 and CO has a strong influence on ignition delay times. Model agreement is good across the range of the study, particularly at the elevated pressures. Also, an increase in carbon monoxide causes the activation energy of the mixture to decrease.

Calculation of Laminar Flame Speed and Autoignition Delay at High Temperature and Pressures

2013 ◽  
Author(s):  
Hui Xu ◽  
Leon A. LaPointe
Keyword(s):  
High Temperature ◽  
Relative Humidity ◽  
Laminar Flame ◽  
Engine Performance ◽  
Simulation Software ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Gaseous Fuels ◽  
Wide Range ◽  
Engine Development

Recent developments in emissions regulations, costs of conventional fuels, and new gas extraction drilling technologies have resulted in an increased emphasis in gaseous fueled spark ignited engine development. However the composition of gaseous fuels can vary greatly. Homogenous Charge Spark Ignited (HCSI) engine performance is heavily dependent upon fuel properties, and robust engine design to utilize gaseous fuels must accommodate these fuel property variances. Accurate prediction of fuel energy release characteristics and knock tendency is critical in the process of HCSI engine development. Combustion characteristics, such as Laminar Flame Speed (LFS) and Autoignition Interval (AI), are used to characterize performance of various gaseous fuels in HCSI engine applications. Combustion duration is related to the LFS. The likelihood of Knock is related to the AI. Overall engine performance is estimated by appropriately incorporating these parameters into cycle simulation software. Experimental data of LFS is often at low temperature and low pressure and thus does not represent the high temperature and pressure conditions typically prevalent in HCSI engine combustion chambers at the time of ignition. Lack of reliable LFS data at high temperature and pressures represents a major opportunity of development for better engine performance simulations [1]. In this paper, the commercially available chemical kinetics solver Chemkin Pro using an appropriate mechanism was employed to compute LFS and AI at typical HCSI engine in-cylinder conditions. It is challenging to compute LFS at such extreme conditions mainly because of autoignition as a competing process. This paper describes development of a robust methodology to compute LFS over a wide range of Temperature (up to 1300 K), Pressure (up to 250 bar), Relative Humidity, and Lambda for Methane. A regression for LFS with Pressure, Temperature, Lambda, and Relative Humidity as independent variables was generated for Methane. Methodology robustness was suggested with similar LFS calculations using other fuels. The form of the regression is similar for all of the fuels investigated.

Generating Laminar Flame Speed Libraries for Autoignition Conditions

2020 ◽  
Author(s):  
Karthik V. Puduppakkam ◽  
Abhijit U. Modak ◽  
Cheng Wang ◽  
Devin Hodgson ◽  
Chitralkumar V. Naik ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Laminar Flame ◽  
Combustion Engine ◽  
Flame Speed ◽  
Cfd Modeling ◽  
Laminar Flame Speed ◽  
Wide Range ◽  
Fuel Effects ◽  
Propagation Properties ◽  
Operating Points

Abstract With advanced gas turbine combustor and internal combustion engine designs, autoignition can happen alongside flame propagation. Laminar flame speeds are required to model flame propagation. Determining laminar flame speeds using simulation assumes flames are freely propagating, an assumption that is not valid when autoignition does occur. From a CFD modeling viewpoint however, it is useful to have extrapolated laminar flame-speed values over a wide range of conditions, to allow CFD to operate smoothly and avoid discontinuities while calculating flame-propagation properties. In this work we focus on developing an approach for generating laminar flame-speed libraries under both nonigniting and autoigniting conditions. Following a test of whether autoignition occurs, laminar flame speeds are either modeled or extrapolated. The details of the approach implemented and its validation are explained. We assess the accuracy of the extrapolation employed by calculating relevant coefficients based on flame speeds from nearby operating points. Recommendations are made for the time scales to be used in determining autoignition occurrence. Fuel effects are also explored in this context.

Reduced Reaction Mechanisms for Methane and Syngas Combustion in Gas Turbines

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
N. Slavinskaya ◽  
M. Braun-Unkhoff ◽  
P. Frank
Keyword(s):  
Heat Release ◽  
Turbulent Combustion ◽  
Reaction Mechanisms ◽  
Gas Turbines ◽  
Laminar Flame ◽  
Laminar Flame Speed ◽  
Preheat Temperature ◽  
Reduced Mechanism ◽  
Wide Range ◽  
Syngas Combustion

Two reduced reaction mechanisms were established that predict reliably for pressures up to about 20bar the heat release for different syngas mixtures including initial concentrations of methane. The mechanisms were validated on the base of laminar flame speed data covering a wide range of preheat temperature, pressure, and fuel-air mixtures. Additionally, a global reduced mechanism for syngas, which comprises only two steps, was developed and validated, too. This global reduced and validated mechanism can be incorporated into CFD codes for modeling turbulent combustion in stationary gas turbines.

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