Backward-Inclined Diffusion Jet Flames in Crossflow at Low Jet-to-Crossflow Momentum Flux Ratios

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Dickson Bwana Mosiria ◽  
Rong Fung Huang ◽  
Ching Min Hsu
Keyword(s):  
Inclination Angle ◽  
Momentum Flux ◽  
Diffusion Flames ◽  
Thermal Power ◽  
Flux Ratio ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Jet Flames ◽  
Air Mixing ◽  
Flame Flashback

In the design of gas turbine combustors, efforts are engineered toward reducing the combustion pollutant emission levels. The pollutant emissions can be reduced by premixing the fuel and the air prior to ignition. However, the main challenges encountered with premixing are flame flashback and blowout, thus, the preference of diffusion flames. In this study, flame behavior, flow patterns, and thermochemical fields of backward-inclined diffusion jet flames in crossflow at low jet-to-crossflow momentum flux ratio of smaller than 0.04 were studied in a wind tunnel. The backward-inclination angle was varied within 0–50 deg. The flames presented three characteristic modes: crossflow dominated flame (low backward inclination angle) denoted by a large down-washed recirculation flame, transitional flame (mediate backward inclination angle) identified by a recirculation flame and a tail flame, and jet dominated flame (high backward inclination angle) characterized by a blue flame base, a yellow tail flame, and the absence of a recirculation flame. Short flames are detected in the regime of the crossflow dominated flames—an indication of improved fuel–air mixing. The findings suggest that for low exhaust emissions which are vigorously pursued in the aviation and thermal power plant industries, especially during low-load operations, the jet dominated flames are the preferable flames as they generate low unburned hydrocarbon, carbon monoxide, and nitric oxide emissions compared to the other flames.

Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames

1999 ◽  
Author(s):  
Ala R. Qubbaj ◽  
S. R. Gollahalli
Keyword(s):  
Diffusion Flames ◽  
Concentration Field ◽  
Laser Induced Fluorescence ◽  
Pollutant Emissions ◽  
Average Decrease ◽  
Burner Exit ◽  
Fluorescence Measurements ◽  
Air Mixing ◽  
Flame Region ◽  
Lif Spectroscopy

Abstract “Venturi-cascading” technique is a means to control pollutant emissions of diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33% in NO emission index along with a 24% decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, Laser Induced Fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH and CN) in the baseline and venturi-cascaded flames. The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18%, 24% and 12% in the concentrations of OH, CH and CN radical, respectively, from their baseline values. However, in the mid-flame region, a 40% average increase in OH, from its baseline value, was observed. In this region, CH or CN radicals were not detected. The OH radical, in the downstream locations, was mostly affected by soot rather than by temperature. In addition, prompt-NO mechanism appeared to play a significant role besides the conventional thermal-NO mechanism.

Effects of Pulsation Intensities on Flame Characteristics of a Small Backward-Inclined Jet Flame in Crossflow

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Ching Min Hsu ◽  
Farha Khan ◽  
Dickson Bwana Mosiria
Keyword(s):  
Low Temperatures ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Reynolds Numbers ◽  
Mode I ◽  
Gas Analyzer ◽  
Jet Flames ◽  
Jet Flame ◽  
Fine Wire ◽  
Characteristic Modes

Abstract The effects of pulsation intensities on the flame characteristics of a 10 deg-backward-inclined jet flame in the crossflow were investigated in a wind tunnel. The jet and the crossflow Reynolds numbers were 1527 and 2165, respectively. The jet-to-crossflow momentum flux ratio was 0.10. A loudspeaker was used to acoustically excite the jet flame. The excitation Strouhal number was 0.73, while the jet pulsation intensities varied from 0 to 1.26. The flame behaviors were studied through photography techniques. The flame temperatures were measured using a fine-wire R-type thermocouple. The combustion-induced emissions were probed by a commercial multi-gas analyzer. The jet flames were categorized into five characteristic modes with increasing pulsation intensities. Mode I was characterized by a yellowish down-washed recirculation flame, a blue neck flame, and a yellow tail flame. Modes II and III featured a split yellow tail flame, a yellowish recirculation flame, and a blue neck flame. Mode IV was characterized by a blue down-washed recirculation flame and neck flame, as well as a split yellow tail flame. Mode V was identified by a single yellow tail flame and the absence of the down-washed recirculation flame. When the jet flames were excited beyond mode I, the combustion-induced pollutants of carbon monoxide and nitric oxide were significantly reduced. However, the excited jet flame in mode V displayed low temperatures in the near-tube region.

Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames

2000 ◽  
Vol 123 (2) ◽  
pp. 158-166
Author(s):  
Ala R. Qubbaj ◽  
S. R. Gollahalli
Keyword(s):  
Diffusion Flames ◽  
Concentration Field ◽  
Laser Induced Fluorescence ◽  
Pollutant Emissions ◽  
Average Decrease ◽  
Burner Exit ◽  
Fluorescence Measurements ◽  
Air Mixing ◽  
Lif Spectroscopy ◽  
Cn Radicals

Venturi-cascading is a technique to control pollutant emissions from diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33 percent in NO emission index along with a 24-percent decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, laser-induced fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH, and CN) in the baseline and venturi-cascaded flames. The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18, 24 and 12 percent in the concentrations of OH, CH, and CN radicals, respectively, from their baseline values. However, in the midflame region, a 40-percent average increase in OH from its baseline value was observed. In this region, CH or CN radicals were not detected. The OH radical concentration in the downstream locations was mostly affected by soot rather than by temperature.

Prediction of gaseous emissions from industrial stacks using an artificial intelligence method

2006 ◽  
Vol 60 (6) ◽  
Author(s):  
C. Anghel ◽  
A. Ozunu
Keyword(s):  
Artificial Intelligence ◽  
Predictive Power ◽  
Thermal Power ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Gaseous Emissions ◽  
Classification Problems ◽  
Power Station ◽  
The Core ◽  
Minimax Probability Machine Regression

AbstractA novel technique based on artificial intelligence methods able to predict pollutant emission concentrations from industrial stacks is presented. This procedure combines regression and classification problems into a unified technique, named minimax decision procedure. The core of this procedure is based on the minimax probability machine regression model. Using experimental databases, the trend of pollutant emissions and the level of pollution for one industrial thermal power station stack were presented. Based on this unified technique, numerical experiments provided the estimates of concentrations of CO, NOx, NO, and SO2 confirming the predictive power of this procedure.

Effect of Fuel Dilution on the Structure and Pollutant Emission of Syngas Diffusion Flames

2007 ◽  
Author(s):  
Xin Hui ◽  
Zhedian Zhang ◽  
Kejin Mu ◽  
Yue Wang ◽  
Yunhan Xiao
Keyword(s):  
Diffusion Flames ◽  
Flame Temperature ◽  
Nox Emission ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
No Emission ◽  
Exhaust Temperature ◽  
Fuel Dilution ◽  
Fuel Stream ◽  
Co Emission

Combustion with diluted syngas is important for integrated gasification combined cycle (IGCC) system that attains high efficiency and low pollutant emissions. In syngas diffusion flames, peak flame temperature is higher than that in nature gas flames, so NOx emission is more significant. To achieve low NOx emission, fuel dilution is an effective way. In the present study, Flame structure and emission characteristics were experimentally and numerically studied in various fuel diluted syngas diffusion flames, and H2O, N2 and CO2 were employed as diluents respectively. The purpose of this paper is to better understand the behavior and mechanism of fuel diluted combustion and to provide fundamental data base for the development of syngas combustion techniques. Experiments were conducted by using jet diffusion flames in a model combustor. Flame size, exhaust temperature and emission concentration were measured. It was found that by introducing diluents into fuel stream, the stoichiometric surface was brought inward, namely the flame envelope shrunk due to a relatively low fuel concentration. The exhaust temperature was decreased. The results also indicated that with diluted fuel stream, there was an increase of CO emission and an apparent decrease of NO emission. For the same exhaust temperature, H2O had the most significant influence on NO emission among the three diluents, while CO2 affected CO emission most by inhibiting its oxidation thermally and chemically. Numerical simulations were performed in counterflow diffusion flames by applying Chemkin software. To reveal the mechanisms of various diluents in flames, the detailed chemistry of H2-CO-N2 system was employed. It was found that the concentration of OH radical is important for both NO and CO emissions. The OH concentration is affected not only by the type of diluents but also by the flame temperature, therefore it is determined by the coupling and competition of diluents’ chemical and thermal effects.

Evaluation of Two Measurement Techniques to Quantify Fuel–Air Mixing of a Gas Turbine Premixer at Atmospheric Conditions

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Wessam Estefanos ◽  
Mahmoud Hamza ◽  
Umesh Bhayaraju ◽  
San-Mou Jeng
Keyword(s):  
Reynolds Number ◽  
Momentum Flux ◽  
High Speed ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Fuel Mass ◽  
Air Mixing

In the present study, two measurement techniques are adopted to evaluate the fuel–air mixing under atmospheric conditions using an industrial fuel–air premixer. These techniques are CO2 mixing and planar laser induced fluorescence (PLIF) in water. In these techniques, CO2 and fluorescent dye are injected as fuel simulants. CO2 measurements are used to validate PLIF in water. In the CO2 technique, CO2 concentrations are converted to fuel mass fractions, whereas in the PLIF technique, a modified post processing method is used to convert the LIF signal into fuel mass fraction. The experiments are conducted at the same Reynolds number and momentum flux ratio for two injection strategies. To study the effect of the flow aerodynamics on the mixing results, high-speed particle image velocimetry (PIV) measurements are conducted in water at the same Reynolds number. A comparison of fuel concentrations measured with the CO2 and PLIF techniques shows good quantitative agreement at all momentum flux ratios. However, deviations between the two techniques are observed at locations of high fuel concentration gradients. The unsteady mixing is evaluated using the PLIF technique with high temporal resolution. Analysis of PIV and PLIF data shows that unsteady mixing is lower at regions of high fluctuations in velocity. Moreover, it is found that there is high unsteady mixing at locations of high concentration gradient.

Environmental Economic Power Dispatch Using Bat Algorithm with Generalized Fly and Evolutionary Boundary Constraint Handling Scheme

2020 ◽  
Vol 11 (2) ◽  
pp. 171-191
Author(s):  
Latifa Dekhici ◽  
Khaled Guerraiche ◽  
Khaled Belkadi
Keyword(s):  
Environmental Economic ◽  
Thermal Power ◽  
Bat Algorithm ◽  
Pollutant Emissions ◽  
Constraint Handling ◽  
Pollutant Emission ◽  
Economic Power ◽  
Power Dispatch ◽  
Boundary Constraint ◽  
Economic Power Dispatch

This article intends to resolve the evolving environmental economic power dispatching problem (EED) using an enhanced version of the bat algorithm (BA) which is the Bat Algorithm with Generalized Fly (BAG). A good solution based on the Evolutionary Boundary Constraint Handling Scheme rather than the well-known absorbing technique and a good choice of the bi-objective function are provided to maintain the advantages of such algorithms on this problem. In the first stage, an individual economic power dispatch problem is considered by minimizing the fuel cost and taking into account the maximum pollutant emission. In the second stage and after weighting soft constraints satisfaction maximization and hard constraints abuse penalties, the proposed approach of the bi-objective environmental and economic load dispatch was built on a pareto function. The approach was tested on a thermal power plant with 10 generators and an IEEE30 power system of 6 generators. The results on the two datasets compared to those of other methods show that the proposed technique yields better cost and pollutant emissions.

Flow and Thermal Structure of Burner-Wake Stabilized Elliptic Jet Flames in a Cross-Flow

2005 ◽  
Author(s):  
S. R. Gollahalli
Keyword(s):  
Momentum Flux ◽  
Thermal Structure ◽  
Flame Structure ◽  
Cross Flow ◽  
Flux Ratio ◽  
Major Axis ◽  
Minor Axis ◽  
Jet Flames ◽  
Zone Structure ◽  
Momentum Flux Ratio

This study was conducted to delineate the coupling effects of the elliptic geometry of the burner and a crossflow on the combustion of gas jets. This paper presents the flow and thermal structure of burner-wake stabilized turbulent propane jet flames from circular (diameter = 0.45 cm) and elliptic (major axis/minor axis = 3) burners of equivalent exit area in a crossflow of air. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access. Flame structure data including temperature profiles and concentration profiles of CO2, O2, CO, and NO were obtained in the single flame configuration (at jet to crossflow momentum flux ratio = 0.0067), where a planar recirculation zone exists completely stabilized in the wake of the burner tube. This study is complementary to our previous study with a two-zone structure flame at jet/crossflow momentum flux ratio of 0.11. Results show that in this flame configuration, the peak NO concentration in the circular burner is higher than that in the elliptic burner flames. Carbon monoxide concentration was approximately same in the flame with circular burner and the elliptic burner with its major axis aligned with cross-flow; the CO concentration in the elliptic flame with the minor axis of the burner aligned with cross-flow was slightly smaller.

Evaluation of Two Measurement Techniques to Quantify Fuel-Air Mixing of a Gas Turbine Pre-Mixer at Atmospheric Conditions

2015 ◽  
Author(s):  
Wessam Estefanos ◽  
Umesh Bhayaraju ◽  
Mahmoud Hamza ◽  
San-Mou Jeng
Keyword(s):  
Reynolds Number ◽  
Momentum Flux ◽  
High Speed ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Fuel Mass ◽  
Air Mixing

In the present study, two measurement techniques are adopted to evaluate the fuel-air mixing under atmospheric conditions using an industrial fuel-air pre-mixer. These techniques are CO2 mixing and Planar Laser Induced Fluorescence (PLIF) in water. In these techniques, CO2 and fluorescent dye are injected as fuel simulants. CO2 measurements are used to validate PLIF in water. In the CO2 technique, CO2 concentrations are converted to fuel mass fractions whereas, in the PLIF technique, a modified post processing method is used to convert the LIF signal into fuel mass fraction. The experiments are conducted at the same Reynolds number and momentum flux ratio for two injection strategies. To study the effect of the flow aerodynamics on the mixing results, high speed PIV measurements are conducted in water at the same Reynolds number. A comparison of fuel concentrations measured with the CO2 and PLIF techniques shows good quantitative agreement at all momentum flux ratios. However, deviations between the two techniques are observed at high fuel concentration gradients. The unsteady mixing is evaluated using PLIF technique with high temporal resolution. Analysis of PIV and PLIF data shows that unsteady mixing is lower at regions of high fluctuations in velocity. Moreover, it is found that there is high unsteady mixing at locations where there is high concentration gradient.

Effects of Location and Direction of Diluent Injection on Radiation and Pollutant Emissions of a Burning Spray

1989 ◽  
Vol 111 (1) ◽  
pp. 16-21 ◽  
Author(s):  
R. Puri ◽  
S. R. Gollahalli
Keyword(s):  
Diffusion Flames ◽  
Flame Length ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Emission Characteristics ◽  
Temperature Profiles ◽  
Spray Flame ◽  
Nitric Oxide Emission ◽  
Radial Injection ◽  
Thermochemical Processes

Introduction of diluents into diffusion flames is an effective method of changing their combustion and pollutant emission characteristics. Since the dominant thermochemical processes vary from region to region of a burning spray, diluent injection at different locations of a flame can affect its overall characteristics differently. This study examines the effects of location and orientation of N2 injection into an air-atomized kerosene spray flame. Flame length, radiant emission, temperature profiles, flame opacity, and concentration profiles of NO, CO, and soot are measured. The overall emission indexes of NO, CO, and soot are calculated. Results show that the diluent injection in the axial downstream direction is superior to the radial injection from the point of reducing heat loss to the combustor walls. The location of injection affects flame characteristics substantially. Injection of diluent into midflame region produces largest reductions in radiation, flame length, and emissions of soot and CO. Nitric oxide emission does not depend significantly on the location of injection.

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