The Influence of Diluent Gases on Combustion Properties of Natural Gas: A Combined Experimental and Modeling Study

2015 ◽  
Author(s):  
Jörn Ermel ◽  
Sandra Richter ◽  
Thomas Kick ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Laminar Flame ◽  
Ambient Pressure ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Diverse Range ◽  
Combustion Properties ◽  
Modeling Study ◽  
A Share

Currently, new concepts for power generation are discussed, as a response to combat global warming due to CO2 emissions stemming from the combustion of fossil fuels. These concepts include new, low-carbon fuels as well as centralized and decentralized solutions. Thus, a more diverse range of fuel supplies will be used, with (biogenic) low-caloric gases such as syngas and coke oven gas (COG) among them. Typical for theses low-caloric gases is the amount of hydrogen, with a share of 50% and even higher. However, hydrogen mixtures have a higher reactivity than natural gas (NG) mixtures, burned mostly in today’s gas turbine combustors. Therefore, in the present work, a combined experimental and modeling study of nitrogen-enriched hydrogen-air mixtures, some of them with a share of methane, to be representative for COG, will be discussed focusing on laminar flame speed data Su as one of the major combustion properties. Measurements were performed in a burner test rig at ambient pressure and at a preheat temperature T0 of 373 K. Flames were stabilized at fuel-air ratios between about φ = 0.5–2.1, depending on the specific fuel-air mixture. This database was used for the validation of four chemical kinetic reaction models, including an in-house one, and by referring to hydrogen-enriched natural gas mixtures. The measured laminar flame speed data of nitrogen-enriched methane-hydrogen-air mixtures are much smaller than the ones of nitrogen-enriched hydrogen-air mixtures. The grade of agreement between measured and predicted data depends on the type of flames and the type of reaction model as well as of the fuel-air ratio: good agreement was found in the fuel lean and slightly fuel rich regime; a large underprediction of the measured data exists at very fuel-rich ratios (φ > 1.4). From the results of the present work, it is obvious that further investigations should focus on highly nitrogen-enriched methane-air mixtures, in particular for very high fuel-air ratio (φ > 1.4). This knowledge will contribute to a more efficient and a more reliable use of low-caloric gases for power generation.

scholarly journals The Influence of Diluent Gases on Combustion Properties of Natural Gas: A Combined Experimental and Modeling Study

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Sandra Richter ◽  
Jörn Ermel ◽  
Thomas Kick ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Laminar Flame ◽  
Ambient Pressure ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Diverse Range ◽  
Combustion Properties ◽  
Modeling Study ◽  
A Share

Currently, new concepts for power generation are discussed, as a response to combat global warming due to CO2 emissions stemming from the combustion of fossil fuels. These concepts include new, low-carbon fuels as well as centralized and decentralized solutions. Thus, a more diverse range of fuel supplies will be used, with (biogenic) low-caloric gases such as syngas and coke oven gas (COG) among them. Typical for theses low-caloric gases is the amount of hydrogen, with a share of 50% and even higher. However, hydrogen mixtures have a higher reactivity than natural gas (NG) mixtures, burned mostly in today's gas turbine combustors. Therefore, in the present work, a combined experimental and modeling study of nitrogen-enriched hydrogen–air mixtures, some of them with a share of methane, to be representative for COG, will be discussed focusing on laminar flame speed data as one of the major combustion properties. Measurements were performed in a burner test rig at ambient pressure and at a preheat temperature T0 of 373 K. Flames were stabilized at fuel–air ratios between about φ = 0.5–2.0 depending on the specific fuel–air mixture. This database was used for the validation of four chemical kinetic reaction models, including an in-house one, and by referring to hydrogen-enriched NG mixtures. The measured laminar flame speed data of nitrogen-enriched methane–hydrogen–air mixtures are much smaller than the ones of nitrogen-enriched hydrogen–air mixtures. The grade of agreement between measured and predicted data depends on the type of flames and the type of reaction model as well as of the fuel–air ratio: a good agreement was found in the fuel lean and slightly fuel-rich regime; a large underprediction of the measured data exists at very fuel-rich ratios (φ > 1.4). From the results of the present work, it is obvious that further investigations should focus on highly nitrogen-enriched methane–air mixtures, in particular for very high fuel–air ratio (φ > 1.4). This knowledge will contribute to a more efficient and a more reliable use of low-caloric gases for power generation.

An experimental and reduced modeling study of the laminar flame speed of jet fuel surrogate components

Fuel ◽  
2013 ◽  
Vol 113 ◽  
pp. 586-597 ◽  
Author(s):  
J.D. Munzar ◽  
B. Akih-Kumgeh ◽  
B.M. Denman ◽  
A. Zia ◽  
J.M. Bergthorson
Keyword(s):  
Laminar Flame ◽  
Jet Fuel ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Reduced Modeling ◽  
Fuel Surrogate ◽  
Modeling Study

Laminar flame speed correlations for methane, ethane, propane and their mixtures, and natural gas and gasoline for spark-ignition engine simulations

2017 ◽  
Vol 18 (9) ◽  
pp. 951-970 ◽  
Author(s):  
Riccardo Amirante ◽  
Elia Distaso ◽  
Paolo Tamburrano ◽  
Rolf D Reitz
Keyword(s):  
Natural Gas ◽  
Laminar Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Computational Time ◽  
Laminar Flame Speed ◽  
Spark Ignition Engines ◽  
Empirical Correlations

The laminar flame speed plays an important role in spark-ignition engines, as well as in many other combustion applications, such as in designing burners and predicting explosions. For this reason, it has been object of extensive research. Analytical correlations that allow it to be calculated have been developed and are used in engine simulations. They are usually preferred to detailed chemical kinetic models for saving computational time. Therefore, an accurate as possible formulation for such expressions is needed for successful simulations. However, many previous empirical correlations have been based on a limited set of experimental measurements, which have been often carried out over a limited range of operating conditions. Thus, it can result in low accuracy and usability. In this study, measurements of laminar flame speeds obtained by several workers are collected, compared and critically analyzed with the aim to develop more accurate empirical correlations for laminar flame speeds as a function of equivalence ratio and unburned mixture temperature and pressure over a wide range of operating conditions, namely [Formula: see text], [Formula: see text] and [Formula: see text]. The purpose is to provide simple and workable expressions for modeling the laminar flame speed of practical fuels used in spark-ignition engines. Pure compounds, such as methane and propane and binary mixtures of methane/ethane and methane/propane, as well as more complex fuels including natural gas and gasoline, are considered. A comparison with available empirical correlations in the literature is also provided.

Evaluation of Kinetic Mechanisms for Direct Fired Supercritical Oxy-Combustion of Natural Gas

2016 ◽  
Author(s):  
Shane Coogan ◽  
Xiang Gao ◽  
Aaron McClung ◽  
Wenting Sun
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
San Diego ◽  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Validation Data ◽  
Data Set ◽  
Reduced Mechanism ◽  
Kinetic Mechanisms

Existing kinetic mechanisms for natural gas combustion are not validated under supercritical oxy-fuel conditions because of the lack of experimental validation data. Our studies show that different mechanisms have different predictions under supercritical oxy-fuel conditions. Therefore, preliminary designers may experience difficulties when selecting a mechanism for a numerical model. This paper evaluates the performance of existing chemical kinetic mechanisms and produces a reduced mechanism for preliminary designers based on the results of the evaluation. Specifically, the mechanisms considered were GRI-Mech 3.0, USC-II, San Diego 204-10-04, NUIG-I, and NUIG-III. The set of mechanisms was modeled in Cantera and compared against the literature data closest to the application range. The high pressure data set included autoignition delay time in nitrogen and argon diluents up to 85 atm and laminar flame speed in helium diluent up to 60 atm. The high carbon dioxide data set included laminar flame speed with 70% carbon dioxide diluent and the carbon monoxide species profile in an isothermal reactor with up to 95% carbon dioxide diluent. All mechanisms performed adequately against at least one dataset. Among the evaluated mechanisms, USC-II has the best overall performance and is preferred over the other mechanisms for use in the preliminary design of supercritical oxy-combustors. This is a significant distinction; USC-II predicts slower kinetics than GRI-Mech 3.0 and San Diego 2014 at the combustor conditions expected in a recompression cycle. Finally, the global pathway selection method was used to reduce the USC-II model from 111 species, 784 reactions to a 27 species, 150 reactions mechanism. Performance of the reduced mechanism was verified against USC-II over the range relevant for high inlet temperature supercritical oxy-combustion.

Optical and Numerical Investigations of Flame Propagation in a Heavy Duty Spark Ignited Natural Gas Engine

2021 ◽  
Author(s):  
Jinlong Liu ◽  
Christopher Ulishney ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Turbulence Intensity ◽  
Laminar Flame ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Heavy Duty ◽  
Piston Chamber

Abstract Increasing the natural gas (NG) use in heavy-duty engines is beneficial for reducing greenhouse-gas emissions from power generation and transportation. However, converting compression ignition (CI) engines to NG spark ignition operation can increase methane emissions without expensive aftertreatment, thereby defeating the purpose of utilizing a low carbon fuel. The widely accepted explanation for the low combustion efficiency in such retrofitted engines is the lower laminar flame speed of natural gas. In addition, diesel engine’s larger bowl size compared to the traditional gasoline engines increases the flame travel length inside the chamber and extends the combustion duration. However, optical measurements performed in this study suggested that a fast-propagating flame was developed inside the cylinder even at extremely lean operation. This was supported by a three-dimensional numerical simulation, which indicated that the squish region of the bowl-in-piston chamber generated a high turbulence intensity inside the bowl. However, the flame propagation experienced a sudden 2.25x reduction in speed when transiting from the bowl to the squish region. Such a phenomenon was caused by the large decrease in the turbulence intensity inside the squish region during the combustion process. Moreover, the squish volume trapped an important fuel fraction, and it is this fraction that experienced a slow and inefficient burning process during the expansion stroke. This resulted in increased methane emissions and reduced combustion efficiency. Overall, it was the specifics of the combustion process inside a bowl-in-piston chamber not the methane’s slow laminar flame speed that contributed to the low methane combustion efficiency for the retrofitted engine. The results suggest that optimizing the chamber shape is paramount to boost engine efficiency and decrease its emissions.

Laminar Flame Speed Measurements and Modeling of Pure Alkanes and Alkane Blends at Elevated Pressures

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
William Lowry ◽  
Jaap de Vries ◽  
Michael Krejci ◽  
Eric Petersen ◽  
Zeynep Serinyel ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Turbines ◽  
Laminar Flame ◽  
Flame Speed ◽  
Published Data ◽  
Laminar Flame Speed ◽  
Binary Blends ◽  
Elevated Pressures ◽  
True Value

Alkanes such as methane, ethane, and propane make up a large portion of most natural gas fuels. Natural gas is the primary fuel used in industrial gas turbines for power generation. Because of this, a fundamental understanding of the physical characteristics such as the laminar flame speed is necessary. Most importantly, this information is needed at elevated pressures to have the most relevance to the gas turbine industry for engine design. This study includes experiments performed at elevated pressures, up to 10 atm initial pressure, and investigates the fuels in a pure form as well as in binary blends. Flame speed modeling was done using an improved version of the kinetics model that the authors have been developing over the past few years. Modeling was performed for a wide range of conditions, including elevated pressures. Experimental conditions include pure methane, pure ethane, 80/20 mixtures of methane/ethane, and 60/40 mixtures of methane/ethane at initial pressures of 1 atm, 5 atm, and 10 atm. Also included in this study are pure propane and 80/20 methane/propane mixtures at 1 atm and 5 atm. The laminar flame speed and Markstein length measurements were obtained from a high-pressure flame speed facility using a constant-volume vessel. The facility includes optical access, a high-speed camera, a schlieren optical setup, a mixing manifold, and an isolated control room. The experiments were performed at room temperature, and the resulting images were analyzed using linear regression. The experimental and modeling results are presented and compared with previously published data. The data herein agree well with the published data. In addition, a hybrid correlation was created to perform a rigorous uncertainty analysis. This correlation gives the total uncertainty of the experiment with respect to the true value rather than reporting the standard deviation of a repeated experiment. Included in the data set are high-pressure results at conditions where in many cases for the single-component fuels few data existed and for the binary blends no data existed prior to this study. Overall, the agreement between the model and data is excellent.

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

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.

Ignition Delay Time and Laminar Flame Speed Calculations for Natural Gas/Hydrogen Blends at Elevated Pressures

2012 ◽  
Author(s):  
Marissa Brower ◽  
Eric Petersen ◽  
Wayne Metcalfe ◽  
Henry J. Curran ◽  
Marc Füri ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Chemical Kinetics ◽  
Ignition Delay ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Hydrogen Addition

Applications of natural gas and hydrogen co-firing have received increased attention in the gas turbine market, which aims at higher flexibility due to concerns over the availability of fuels. While much work has been done in the development of a fuels database and corresponding chemical kinetics mechanism for natural gas mixtures, there are nonetheless few if any data for mixtures with high levels of hydrogen at conditions of interest to gas turbines. The focus of the present paper is on gas turbine engines with primary and secondary reaction zones as represented in the Alstom and Rolls Royce product portfolio. The present effort includes a parametric study, a gas turbine model study, and turbulent flame speed predictions. Using a highly optimized chemical kinetics mechanism, ignition delay times and laminar burning velocities were calculated for fuels from pure methane to pure hydrogen and with natural gas/hydrogen mixtures. A wide range of engine-relevant conditions were studied: pressures from 1 to 30 atm, flame temperatures from 1600 to 2200 K, primary combustor inlet temperature from 300 to 900 K, and secondary combustor inlet temperatures from 900 to 1400 K. Hydrogen addition was found to increase the reactivity of hydrocarbon fuels at all conditions by increasing the laminar flame speed and decreasing the ignition delay time. Predictions of turbulent flame speeds from the laminar flame speeds show that hydrogen addition affects the reactivity more when turbulence is considered. This combined effort of industrial and university partners brings together the know-how of applied, as well as experimental and theoretical disciplines.

Experimental Study on Laminar Flame Speed of Natural Gas/Carbon Monoxide/Air Mixtures

2015 ◽  
Vol 37 (6) ◽  
pp. 576-582 ◽  
Author(s):  
B. Zhang ◽  
C. Dong ◽  
Q. Zhou ◽  
X. Chen ◽  
P. J. Culligan ◽  
...  
Keyword(s):  
Experimental Study ◽  
Carbon Monoxide ◽  
Natural Gas ◽  
Laminar Flame ◽  
Flame Speed ◽  
Laminar Flame Speed

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.

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