The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Nicolas Petit - One of the best experts on this subject based on the ideXlab platform.
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
Delay Systems, 2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:International audienceIn this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:This paper studies the low-pressure Burned Gas recirculation in spark-ignited engines and shows, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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TDS - Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
IFAC Proceedings Volumes, 2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low-pressure Burned Gas recirculation in spark-ignited engines for automotive powertrain. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Combustion phasing model for control of a Gasoline-ethanol fueled SI engine with variable valve timing
2012 American Control Conference (ACC), 2012Co-Authors: Carrie M. Hall, Jonathan Chauvin, Gregory M. Shaver, Nicolas PetitAbstract:Concern over the availability of fossil fuels and energy usage have produced an interest in both alternative fuels and new engine technologies such as variable valve timing to improve engine efficiency. Fuel-flexible engines permit the increased use of ethanol-Gasoline blends. Ethanol is a renewable fuel which has the added advantage of improving performance in typically knock-limited operating regions due to the higher octane rating of the fuel. Furthermore, many modern engines are also being equipped with variable valve timing (VVT), a technology which allows increased control of the quantity of Burned Gas in-cylinder and can increase engine efficiency by reducing the need for throttling. The Burned Gas fraction as well as the blend ratio of ethanol impact the combustion timing and capturing these effects is essential if the combustion phasing is to be properly controlled. Combustion efficiency is typically tied to an optimal CA50 (crankangle when 50% of fuel is Burned) for an engine. This paper proposes a physically-based model which captures combustion phasing and is designed to provide accurate estimates of CA50 for real-time control efforts allowing the CA50 to be adjusted to its optimal value despite changes in fuel and valve overlap. This control-oriented model was extensively validated at over 500 points across the engine operating range for four blends of Gasoline and ethanol.
Jonathan Chauvin - One of the best experts on this subject based on the ideXlab platform.
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
Delay Systems, 2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:International audienceIn this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:This paper studies the low-pressure Burned Gas recirculation in spark-ignited engines and shows, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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TDS - Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
IFAC Proceedings Volumes, 2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low-pressure Burned Gas recirculation in spark-ignited engines for automotive powertrain. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Combustion phasing model for control of a Gasoline-ethanol fueled SI engine with variable valve timing
2012 American Control Conference (ACC), 2012Co-Authors: Carrie M. Hall, Jonathan Chauvin, Gregory M. Shaver, Nicolas PetitAbstract:Concern over the availability of fossil fuels and energy usage have produced an interest in both alternative fuels and new engine technologies such as variable valve timing to improve engine efficiency. Fuel-flexible engines permit the increased use of ethanol-Gasoline blends. Ethanol is a renewable fuel which has the added advantage of improving performance in typically knock-limited operating regions due to the higher octane rating of the fuel. Furthermore, many modern engines are also being equipped with variable valve timing (VVT), a technology which allows increased control of the quantity of Burned Gas in-cylinder and can increase engine efficiency by reducing the need for throttling. The Burned Gas fraction as well as the blend ratio of ethanol impact the combustion timing and capturing these effects is essential if the combustion phasing is to be properly controlled. Combustion efficiency is typically tied to an optimal CA50 (crankangle when 50% of fuel is Burned) for an engine. This paper proposes a physically-based model which captures combustion phasing and is designed to provide accurate estimates of CA50 for real-time control efforts allowing the CA50 to be adjusted to its optimal value despite changes in fuel and valve overlap. This control-oriented model was extensively validated at over 500 points across the engine operating range for four blends of Gasoline and ethanol.
Thomas Leroy - One of the best experts on this subject based on the ideXlab platform.
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
Delay Systems, 2014Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:International audienceIn this chapter, the authors provide an overview and study of the low- pressure Burned Gas recirculation in spark-ignited engines for automotive power- train. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The mod- eled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines
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Practical delay modeling of externally recirculated Burned Gas fraction for Spark-Ignited engines
2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:This paper studies the low-pressure Burned Gas recirculation in spark-ignited engines and shows, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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TDS - Practical Delay Modeling of Externally Recirculated Burned Gas Fraction for Spark-Ignited Engines
IFAC Proceedings Volumes, 2013Co-Authors: Delphine Bresch-pietri, Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:In this chapter, the authors provide an overview and study of the low-pressure Burned Gas recirculation in spark-ignited engines for automotive powertrain. It is shown, at the light of supportive experimental results, that a linear delay system permits to capture the dominant effects of the system dynamics. The modeled transport delay is defined by implicit equations stemming from first principles and can be calculated online. This model is shown to be sufficiently accurate to replace a sensor that would be difficult and costly to implement on commercial engines.
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Transient Burned Gas Rate Control on VVA equipped Diesel Engines
IFAC Proceedings Volumes, 2010Co-Authors: Thomas Leroy, Jonathan Chauvin, Nicolas PetitAbstract:Abstract This paper addresses the problem of cylinder Burned Gas rate transient control of VVA equipped Diesel engines. This problem is of importance for NOx emissions reduction. The proposed strategy coordinates existing low-level intake manifold Burned Gas rate and VVA controllers. To determine relevant control actions, a model of cylinder filling phenomenon is determined. It expresses, under the form of a discrete event dynamics, the behavior of the cylinder Burned Gas rate at intake valve closure. Interestingly, the model is invertible, thanks to its analytical nature. This property directly suggests an inverse formula that serves as control law. The strategy is efficient as is highlighted by experimental results obtained on a 1.6 L Diesel engine test bench. As a result, NOx emissions are largely diminished during transients.
Elisa Toulson - One of the best experts on this subject based on the ideXlab platform.
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The critical lower radius limit approach for laminar flame speed measurement from spherically expanding stretched flames
Experimental Thermal and Fluid Science, 2021Co-Authors: Berk Can Duva, Lauren Elizabeth Chance, Elisa ToulsonAbstract:Abstract Spherically expanding flames are severely affected by flame stretch in the early stage of combustion and therefore stretch models are of great importance in determining the uncertainty of experimental laminar flame speeds (SL) and Burned Gas Markstein lengths (Lb). In order to prevent the existing large scatter in experimental data of these two fundamental flame parameters, the effect of the lower radius limit for the flame speed calculation on extrapolation results of the stretch models was investigated through spherically expanding flames under constant pressure. Methane, hydrogen, propane, and iso-octane fuels were tested to account for both hydrocarbon and non-hydrocarbon fuels with different evolutions in the Burned Gas Markstein length when equivalence ratio is increased. Results show that there is a critical lower radius limit (RL,critical), where all laminar flame speed and Burned Gas Markstein length values obtained by the extrapolation of the stretch models converge to the same laminar flame speed and Burned Gas Markstein length. The value of the critical lower radius limit strongly depends on the Burned Gas Markstein number (Mab) and this dependency can be shown with |Mab|=0.8424*RL,critical for fuel/oxidizer mixtures with −0.48 mm ≤ Lb ≤ 1.23 mm (or, −0.62 ≤ Mab ≤ 2.60). Finally, laminar flame speeds and Burned Gas Markstein lengths of methane, hydrogen, propane, and iso-octane flames that were corrected according to the critical lower radius limit approach proposed in the present study were compared to previously published experimental results.
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dilution effect of different combustion residuals on laminar burning velocities and Burned Gas markstein lengths of premixed methane air mixtures at elevated temperature
Fuel, 2020Co-Authors: Berk Can Duva, Lauren Elizabeth Chance, Elisa ToulsonAbstract:Abstract Most of the experimental examinations on laminar flame characteristics of a diluted combustible mixture have simulated combustion residuals with one of the main exhaust Gases (N2, H2O, and CO2) or a mixture of two. However, flue Gases have quite different thermodynamic properties and chemical reactivities. Therefore, simulating the post combustion products used for dilution with only one or two of the main exhaust Gases may yield erroneous laminar flame characteristic data. In the present study, the laminar burning velocities and Burned Gas Markstein lengths of diluted methane/air mixtures at 1 bar and 473 K were measured with spherically expanding flames under constant pressure in an optically accessible constant volume combustion chamber. The mixtures were diluted with N2, H2O, and CO2 individually as well as with a mixture of 71.49% N2 + 19.01% H2O + 9.50% CO2 by volume, which represents the main product concentrations from stoichiometric methane/air combustion. Experimental results show that the laminar flame speed values of methane/air mixtures diluted with actual combustion residuals are between those of N2 and H2O dilution, whereas the laminar burning velocities of methane flames diluted with CO2 are considerably slower. The effects of different combustion residuals on the Burned Gas Markstein length were not found to be significant. At the experimentally-investigated initial conditions, CHEMKIN analyses were performed with the GRI-Mech 3.0, San Diego, and USC Mech II mechanisms to inquire about the performances of the kinetic schemes. The GRI-Mech 3.0 results were the closest to the experimental data. This mechanism was also utilized to numerically quantify the dilution, thermal diffusion, and chemical effects of combustion residuals. The dilution effect was the leading effect in decreasing the laminar burning velocity, while the thermal diffusion effect had the smallest contribution. Nevertheless, the thermal diffusion effect changes the thermal and mass diffusivities, and, as a result, the Lewis number, making it a vital parameter for flame stability and stretch. As the thermodynamic properties and chemical reactivities of the combustion residuals vary with temperature, pressure, equivalence and dilution ratios, real combustion residuals cannot be accurately represented with only one or two of the main exhaust Gases, as shown in the current study.
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Dilution effect of different combustion residuals on laminar burning velocities and Burned Gas Markstein lengths of premixed methane/air mixtures at elevated temperature
Fuel, 2020Co-Authors: Berk Can Duva, Lauren Elizabeth Chance, Elisa ToulsonAbstract:Abstract Most of the experimental examinations on laminar flame characteristics of a diluted combustible mixture have simulated combustion residuals with one of the main exhaust Gases (N2, H2O, and CO2) or a mixture of two. However, flue Gases have quite different thermodynamic properties and chemical reactivities. Therefore, simulating the post combustion products used for dilution with only one or two of the main exhaust Gases may yield erroneous laminar flame characteristic data. In the present study, the laminar burning velocities and Burned Gas Markstein lengths of diluted methane/air mixtures at 1 bar and 473 K were measured with spherically expanding flames under constant pressure in an optically accessible constant volume combustion chamber. The mixtures were diluted with N2, H2O, and CO2 individually as well as with a mixture of 71.49% N2 + 19.01% H2O + 9.50% CO2 by volume, which represents the main product concentrations from stoichiometric methane/air combustion. Experimental results show that the laminar flame speed values of methane/air mixtures diluted with actual combustion residuals are between those of N2 and H2O dilution, whereas the laminar burning velocities of methane flames diluted with CO2 are considerably slower. The effects of different combustion residuals on the Burned Gas Markstein length were not found to be significant. At the experimentally-investigated initial conditions, CHEMKIN analyses were performed with the GRI-Mech 3.0, San Diego, and USC Mech II mechanisms to inquire about the performances of the kinetic schemes. The GRI-Mech 3.0 results were the closest to the experimental data. This mechanism was also utilized to numerically quantify the dilution, thermal diffusion, and chemical effects of combustion residuals. The dilution effect was the leading effect in decreasing the laminar burning velocity, while the thermal diffusion effect had the smallest contribution. Nevertheless, the thermal diffusion effect changes the thermal and mass diffusivities, and, as a result, the Lewis number, making it a vital parameter for flame stability and stretch. As the thermodynamic properties and chemical reactivities of the combustion residuals vary with temperature, pressure, equivalence and dilution ratios, real combustion residuals cannot be accurately represented with only one or two of the main exhaust Gases, as shown in the current study.
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Correlations for the laminar burning velocity and Burned Gas Markstein length of methane-air mixtures diluted with flue Gases at high temperatures and pressures
Fuel, 2020Co-Authors: Berk Can Duva, Lauren Elizabeth Chance, Yen Cheng Wang, Elisa ToulsonAbstract:Abstract Laminar burning velocity and Burned Gas Markstein length correlations have been developed from the measurements of spherically expanding methane-air flames under constant pressure at 1–5 bar, 373–473 K, and with 0–15% dilution. A dilution mixture consisting of 71.49% N2 + 19.01% H2O + 9.50% CO2 by mole, representing the actual principal residual concentrations from stoichiometric methane-air combustion, was used. Only equivalence ratios where the laminar burning velocity was greater than 15 cm/s were reported, due to the buoyancy effect limitation. The physical and chemical aspects of changes in the laminar burning velocity and flame front stability due to changes in temperature, pressure, equivalence and dilution ratios were discussed in detail. Experimentally measured laminar burning velocity data and a newly developed correlation in this study were compared with numerical results obtained from several chemical mechanisms as well as experimental data from the literature.
Shigeru Hayashi - One of the best experts on this subject based on the ideXlab platform.
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Emissions Characteristics of Combustion of Lean Secondary Premixed Gas Jets Injected Into Burned Gas From Primary Stage by Lean Premixed Combustion Supported by Reverse Jet Flame Holding
Volume 4A: Combustion Fuels and Emissions, 2016Co-Authors: Takumi Saitoh, Hideshi Yamada, Takafumi Nakasu, Takumi Hiroi, Shigeru HayashiAbstract:The emissions characteristics of a model Gas turbine combustor characterized by the enhancement of the reactions of the secondary mixtures of lean to ultra-lean compositions by the Burned Gas from the primary stage were investigated at atmospheric pressure. A cylindrical quartz tube with the bottom end closed was used as the combustion chamber and the mixture injector was extending co-axially into the combustion chamber to the bottom wall. The stagnation point reverse flow combustion was used for the primary stage where the primary mixture was injected toward the end wall. The secondary mixture was injected radially from the multiple holes in the outer wall of the injector into the Burned Gas from the primary stage. The effects of the positions for injection of the primary and secondary mixtures as well as mixture temperatures on NOx, CO and HC emissions were investigated over a range of the primary and secondary mixture equivalence ratios at atmospheric pressure.
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Emissions in combustion of lean methane-air and biomass-air mixtures supported by primary hot Burned Gas in a multi-stage Gas turbine combustor
Proceedings of the Combustion Institute, 2007Co-Authors: Sadamasa Adachi, Shigeru Hayashi, Hideshi Yamada, Atushi Iwamoto, Shigehiko KanekoAbstract:Abstract Thermal reaction of lean to ultra-lean premixed mixtures supported by the hot Burned Gas from the up-stream stage can be used for obtaining a better trade-off between ultra-low-NO x and high combustion efficiency over a wide range of operations of a Gas turbine. A three-stage model combustor designed based on this concept is being developed for a biomass Gas-fueled regenerative cycle 10 kW micro-Gas turbine. Tubular flame combustion is used for the primary stage and mixtures of lean to ultra-lean compositions are injected into the cross-flowing hot Burned Gas from the up-stream stage in the secondary and tertiary stages. The emissions and combustion characteristics are evaluated with methane and simulated biomass Gas of different CO 2 contents at atmospheric pressure and inlet air temperatures up to 700 K. In the experiments, the fuel flow for the secondary mixture was gradually increased while maintaining the fuel flow to the primary stage in the two-stage combustion mode and the fuel flow for the tertiary mixture was gradually increased while maintaining the fuel flows to the primary and secondary stages in the three-stage combustion mode. The combustor exit NO x concentration corrected to 15% O 2 remained at or slightly lower than the level that was achieved at the start of fuel staging as far as the injected mixture was leaner than the primary mixture and NO x emissions in the 10 ppm level were achieved at Gas temperatures less than 1700 K. In contrast, the NO x concentration increase steeply with equivalence ratio in non-staged combustion mode. The reaction of the injected mixture was completion when the reaction zone temperature was higher than 1500 K regardless of inlet air temperature and equivalence ratio of the primary stage. The results show that, the multi-stage combustion where mixtures of ultra-lean to lean compositions are injected into the hot Burned Gas from the up-stream stage achieved low-NO x emissions and high combustion efficiency over a wide range of overall equivalence ratios or combustor exit Gas temperatures. It is found that the CO 2 in the simulated biomass Gas suppresses the NO formation by slowing down the progress of combustion reaction, especially at high temperature conditions.
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Combustion of lean prevaporized fuel–air mixtures mixed with hot Burned Gas for low-NOx emissions over an extended range of fuel–air ratios
Proceedings of the Combustion Institute, 2005Co-Authors: Naoki Aida, Tomoki Nishijima, Shigeru Hayashi, Hideshi Yamada, Tadashige KawakamiAbstract:Abstract Reaction of lean to ultra-lean mixtures supported by high-temperature Burned Gas can resolve the dilemma between complete combustion versus ultra-low NOx emissions in lean premixed Gas turbine combustors. The combustion characteristics and NOx emissions in “lean–lean” two-stage combustion were investigated for premixed–prevaporized kerosene–air mixtures using a co-axial flow configuration. Secondary prevaporized kerosene–air mixtures of lean to ultra-lean compositions were injected into the stream of hot Burned Gas prepared by the combustion of lean prevaporized kerosene–air mixtures stabilized on an annular perforated flame holder in the primary stage. The progress of mixing and reactions of the secondary mixture jets of prevaporized kerosene–air mixture injected into the co-axial primary hot Burned Gas flow were investigated by spatial Gas sampling and direct photography. The effects of the ratio of secondary to primary air flow rates and equivalence ratios of the primary and secondary mixtures on the emissions from the two-stage combustor were studied. Imparting swirl to the secondary mixture jets resulted in an enhancement of the mixing of the jets with the primary Burned Gas. It was also shown that the use of reaction of lean to ultra-lean secondary mixtures supported by the hot Burned Gas from the primary stage is much advantageous in extending the operating range of ultra-low NOx emissions of the 10 ppm level and complete combustion as compared with other approaches such as fuel staging and variable geometry. The proposed ultra-low NOx combustion concept has a potential of suppressing combustion instabilities that is often experienced with lean premixed combustion.
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combustion of lean prevaporized fuel air mixtures mixed with hot Burned Gas for low nox emissions over an extended range of fuel air ratios
Proceedings of the Combustion Institute, 2005Co-Authors: Naoki Aida, Tomoki Nishijima, Shigeru Hayashi, Hideshi Yamada, Tadashige KawakamiAbstract:Abstract Reaction of lean to ultra-lean mixtures supported by high-temperature Burned Gas can resolve the dilemma between complete combustion versus ultra-low NOx emissions in lean premixed Gas turbine combustors. The combustion characteristics and NOx emissions in “lean–lean” two-stage combustion were investigated for premixed–prevaporized kerosene–air mixtures using a co-axial flow configuration. Secondary prevaporized kerosene–air mixtures of lean to ultra-lean compositions were injected into the stream of hot Burned Gas prepared by the combustion of lean prevaporized kerosene–air mixtures stabilized on an annular perforated flame holder in the primary stage. The progress of mixing and reactions of the secondary mixture jets of prevaporized kerosene–air mixture injected into the co-axial primary hot Burned Gas flow were investigated by spatial Gas sampling and direct photography. The effects of the ratio of secondary to primary air flow rates and equivalence ratios of the primary and secondary mixtures on the emissions from the two-stage combustor were studied. Imparting swirl to the secondary mixture jets resulted in an enhancement of the mixing of the jets with the primary Burned Gas. It was also shown that the use of reaction of lean to ultra-lean secondary mixtures supported by the hot Burned Gas from the primary stage is much advantageous in extending the operating range of ultra-low NOx emissions of the 10 ppm level and complete combustion as compared with other approaches such as fuel staging and variable geometry. The proposed ultra-low NOx combustion concept has a potential of suppressing combustion instabilities that is often experienced with lean premixed combustion.
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Extending low-NOx operating range of a lean premixed–prevaporized Gas turbine combustor by reaction of secondary mixtures injected into primary stage Burned Gas
Proceedings of the Combustion Institute, 2005Co-Authors: Shigeru Hayashi, Hideshi Yamada, Mitsumasa MakidaAbstract:Abstract Reactions of lean to ultra-lean premixed mixtures injected into the hot Burned Gas that was produced in the lean-burn primary stage can be successfully used for extending the ultra-low NOx operating range of a Gas turbine combustor. A tubular lean–lean two-stage model combustor for a simple cycle 200 kW Gas turbine was designed based on this concept. Two secondary mixture injection tubes with a flow deflector at the exit, extending into the primary combustion zone, were used to inject lean premixed–prevaporized kerosene–air mixtures of various fuel concentrations into the volumes of hot Burned Gas produced by the lean-burn primary burners. The emissions and combustion characteristics were evaluated at 600 K inlet air temperature and 0.8 MPa pressure for two sizes of mixture injection tubes. With increasing the secondary fuel flow rate while maintaining the primary mixture equivalence ratio fixed, the NOx concentration remained at the level achieved for no secondary fuel (i.e., single stage combustion) for a while before it gradually increased. A still further increase in the secondary mixture equivalence ratio beyond the primary mixture equivalence ratio finally resulted in a steep increase in NOx emissions due to enhanced thermal NOx formation. It was shown that at proper air splits, high combustion efficiency was achieved while maintaining the NOx emissions in a single digit over a very wide range of overall equivalence ratios. It was found that combustion oscillation hardly occurred in the lean–lean two-stage combustion provided that the primary mixture was lean enough, though severe combustion oscillation occurred at greater overall equivalence ratios (typically >0.8) in the single stage combustion.
