Analysis of NOX Formation in an Axially Staged Combustion System at Elevated Pressure Conditions

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Chockalingam Prathap ◽  
Flavio C. C. Galeazzo ◽  
Plamen Kasabov ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
...  
Keyword(s):  
Penetration Depth ◽  
Mole Fraction ◽  
Momentum Flux ◽  
Cross Flow ◽  
Flux Ratio ◽  
Elevated Pressure ◽  
Operating Conditions ◽  
Nox Formation ◽  
Jet Flame ◽  
Stage Combustion

The objective of this investigation was to study the effect of axially staged injection of methane in the vitiated air cross flow in a two stage combustion chamber on the formation of NOX for different momentum flux ratios. The primary cylindrical combustor equipped with a low swirl air blast nozzle operating with Jet-A liquid fuel generates vitiated air in the temperature range of 1473–1673 K at pressures of 5–8 bars. A methane injector was flush mounted to the inner surface of the secondary combustor at an angle of 30 deg. Oil cooled movable and static gas probes were used to collect the gas samples. The mole fractions of NO, NO2, CO, CO2, and O2 in the collected exhaust gas samples were measured using gas analyzers. For all the investigated operating conditions, the change in the mole fraction of NOX due to the injection of methane (ΔNOX) corrected to 15% O2 and measured in dry mode was less than 15 ppm. The mole fraction of ΔNOX increased with an increase in mass flow rate of methane and it was not affected by a change in the momentum flux ratio. The penetration depth of the methane jet was estimated from the profiles of mole fraction of O2 obtained from the samples collected using the movable gas probe. For the investigated momentum flux ratios, the penetration depth observed was 15 mm at 5 bars and 5 mm at 6.5 and 8 bars. The results obtained from the simulations of the secondary combustor using a RANS turbulence model were also presented. Reaction modeling of the jet flame present in a vitiated air cross flow posed a significant challenge as it was embedded in a high turbulent flow and burns in partial premixed mode. The applicability of two different reaction models has been investigated. The first approach employed a combination of the eddy dissipation and the finite rate chemistry models to determine the reaction rate, while the presumed JPDF model was used in the further investigations. Predictions were in closer agreement to the measurements while employing the presumed JPDF model. This model was also able to predict some key features of the flow such as the change of penetration depth with the pressure.

Analysis of NOX Formation in an Axially Staged Combustion System at Elevated Pressure Conditions

2011 ◽  
Author(s):  
Prathap Chockalingam ◽  
Flavio Cesar Cunha Galeazzo ◽  
Plamen Kasabov ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
...  
Keyword(s):  
Penetration Depth ◽  
Mole Fraction ◽  
Momentum Flux ◽  
Cross Flow ◽  
Flux Ratio ◽  
Elevated Pressure ◽  
Operating Conditions ◽  
Nox Formation ◽  
Jet Flame ◽  
Stage Combustion

The objective of this investigation was to study the effect of axially staged injection of methane in the vitiated air cross flow in a two stage combustion chamber on the formation of NOX for different momentum flux ratios. The primary cylindrical combustor equipped with a low swirl air blast nozzle operating with Jet-A liquid fuel generates vitiated air in the temperature range of 1473–1673 K at pressures of 5–8 bar. A methane injector was flush mounted to the inner surface of the secondary combustor at an angle of 30°. Oil cooled movable and static gas probes were used to collect the gas samples. The mole fractions of NO, NO2, CO, CO2 and O2 in the collected exhaust gas samples were measured using gas analyzers. For all the investigated operating conditions, the change in the mole fraction of NOX due to the injection of methane (ΔNOX) corrected to 15% O2 and measured in dry mode was less than 15 ppm. The mole fraction of ΔNOX increased with an increase in mass flow rate of methane and it was not affected by a change in the momentum flux ratio. The penetration depth of the methane jet was estimated from the profiles of mole fraction of O2 obtained from the samples collected using the movable gas probe. For the investigated momentum flux ratios, the penetration depth observed was 15 mm at 5 bar and 5 mm at 6.5 and 8 bar. The results obtained from the simulations of the secondary combustor using a RANS turbulence model were also presented. Reaction modeling of the jet flame present in a vitiated air cross flow posed a significant challenge as it was embedded in a high turbulent flow and burns in partial premixed mode. The applicability of two different reaction models has been investigated. The first approach employed a combination of the eddy dissipation and the finite rate chemistry models to determine the reaction rate, while the presumed JPDF model was used in the further investigations. Predictions were in closer agreement to the measurements while employing the presumed JPDF model; this model was also able to predict some key features of the flow as the change of penetration depth with the pressure.

Turbulent Gas Jet Flames in Cross-Flow at Low Momentum Flux Ratios

1994 ◽  
Author(s):  
S. R. Gollahalll ◽  
B. Nanjundappa
Keyword(s):  
Momentum Flux ◽  
Flame Structure ◽  
Axisymmetric Flow ◽  
Cross Flow ◽  
Flux Ratio ◽  
Gas Jet ◽  
Jet Flame ◽  
Flow Recirculation ◽  
Two Dimensional Flow ◽  
The Stability

An experimental study of the stability and structure of a propane gas jet flame in cross-flow at a low jet to cross-flow momentum flux ratio (0.024) is presented. The flame structure is characterized by two distinct zones. A two-dimensional flow recirculation zone attached to the burner tube in its wake forms the first zone. An axisymmetric flow follows the first zone downstream. The junction of the two zones is characterized by an intense mixing of jet and cross-flow streams. This paper deals with the structure of the first zone. The temperature and concentration profiles show that the physico-chemical processes and combustion in that zone are diffusion controlled.

Sprays in Cross Flow: Dependence on Weber Number

2007 ◽  
Author(s):  
Eugene Lubarsky ◽  
Jonathan R. Reichel ◽  
Ben T. Zinn ◽  
Rob McAmis
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Fuel Injection ◽  
Flow Direction ◽  
Air Flow ◽  
Cross Flow ◽  
Flux Ratio ◽  
Elevated Pressure ◽  
Momentum Flux Ratio ◽  
Breakup Mechanism

This paper describes an experimental investigation of the spray created by Jet A fuel injection from a plate containing sharp edged orifice 0.018 inches (457 μm) in diameter and L/D ratio of 10 into the crossflow of preheated air (555 K) at elevated pressure in the test section (4 ata) and liquid to air momentum-flux ratio of 40. A 2 component Phase Doppler Particle Analyzer used for measuring the characteristics of the spray. The Weber number of the spray in crossflow was varied between 33 and 2020 and the effect of Weber number on spray properties was investigated. It was seen that shear breakup mechanism dominates at Weber number greater than about 100. Droplets’ diameters were found to be in the range of 15-30 microns for higher values of Weber numbers, while larger droplets (100-200 microns) were observed at Weber number of 33. Larger droplets were observed at the periphery of the spray. The droplet velocities and diameters were measured in a plane 30mm downstream of the orifice along the centerline of the spray at an incoming air flow Mach number of 0.2 and liquid to air momentum-flux ratio of 40. The droplets reach a maximum of 90% of the flow velocity at this location. The velocity of droplets in the directions perpendicular to the air flow direction is higher at the periphery of the spray possibly due to the presence of larger droplets. The RMS values of the droplet velocities are highest slightly off center of the centerline of the spray showing the presence of strong vortices formed due to the liquid jet in crossflow. The data presented here could serve as benchmark data for CFD code validation.

scholarly journals Drop Size Characteristics of Forward Angled Injectors in Subsonic Cross Flows

2013 ◽  
Author(s):  
Venkat S. Iyengar ◽  
Sathiyamoorthy Kumarasamy ◽  
Srinivas Jangam ◽  
Manjunath Pulumathi
Keyword(s):  
Gas Turbine ◽  
Test Section ◽  
Momentum Flux ◽  
Drop Size ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Axial Distance ◽  
Momentum Flux Ratio ◽  
Spray Plume

Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiments were done with a 10 degree forward angled 0.8 mm diameter plain orifice nozzle which was flush mounted on the bottom plate of test section. Laser diffraction using Malvern Spraytec particle analyzer was used to measure drops size and distributions in the near field of the spray. Measurements were performed at a distance of 70 mm from the injector at various locations along the height of the spray plume for a reasonable range of liquid flow rates as in practical devices. The sprays were characterized using the non dimensional parameters such as the Weber number and the momentum flux ratio and drop sizes were measured at three locations along the height of the spray from the bottom wall. The momentum flux ratio was varied from 5 to 25. Results indicate that with increase in momentum flux ratio the SMD reduced at the specific locations and an higher overall SMD was observed as one goes from the bottom to the top of the spray plume. This was accompanied by a narrowing of the drop size distribution.

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.

Effect of Cross-Flow Swirl on the Trajectory of Spray in an Annular Passage

2020 ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari
Keyword(s):  
Momentum Flux ◽  
High Speed ◽  
Air Flow ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Swirl Number ◽  
Flow Swirl ◽  
Air Stream ◽  
The Impact

Abstract This paper presents the experimental analysis of the impact of swirl number of cross-flowing air stream on liquid jet spray trajectory at a fixed air flow velocity of 42 m/s with the corresponding Mach number of 0.12. The experiments were conducted for 4 different swirl numbers (0, 0.2, 0.42 and 0.73) using swirl vanes at air inlet having angles of 0°, 15°, 30° and 45° respectively. Liquid to air momentum flux ratio (q) was varied from 5 to 25. High speed (@ 500 fps) images of the spray were captured and those images were processed using MATLAB to obtain the path of the spray at various momentum flux ratios. The results show interesting trends for the spray trajectory and the jet spread in swirling air flow. High swirling flows not only lead to spray with lower radial penetration due to sharp bending and disintegration of liquid jet, but also result in spray with high jet spread and spray area. Based on the results, correlations for the spray path have been proposed which incorporates the effects of the swirl number of the air flow.

Experimental Investigation of Liquid Jet Breakup in a Cross Flow of a Swirling Air Stream

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari ◽  
Saadat Syed ◽  
Jeffery A. Lovett
Keyword(s):  
Experimental Investigation ◽  
Momentum Flux ◽  
High Speed ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Penetration Behavior

This paper presents the results of an experimental investigation of liquid jet breakup in a cross flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach number 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using matlab to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes—bag breakup, column breakup, shear breakup, and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15 deg swirl show reduced breakup length and penetration related to the nonuniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.

Structure of the Flow Field of a Nonpremixed Gas Jet Flame in Cross-Flow

1997 ◽  
Vol 119 (2) ◽  
pp. 137-144 ◽  
Author(s):  
O. Savas ◽  
R. F. Huang ◽  
S. R. Gollahalli
Keyword(s):  
Flow Field ◽  
Flame Structure ◽  
Experimental Studies ◽  
Power Spectra ◽  
Cross Flow ◽  
Flux Ratio ◽  
Quantitative Information ◽  
Turbulent Flames ◽  
Complex Flow ◽  
Jet Flame

Experimental studies on nonpremixed turbulent flames in cross flow are necessary as the current analytical and numerical tools are unable to provide acceptable quantitative information about their complex flow fields. This study, which complements the results of a previous study by the authors on the flame structure in the stabilization region of a partially lifted turbulent diffussion flame in cross-flow (TDFCF), presents the measured turbulence quantities in the flow field of the same flame. Results include mean velocities in the cross-stream and spanwise directions, the vertical and horizontal components of fluctuating components of velocity, Reynolds stress, power spectra, and autocorrelations useful for developing and validating theoretical models of TDFCF in the moderate momentum flux ratio range

Computational Analysis on Primary Breakup and Deformation of Kerosene Jet in Subsonic Cross Flow Using VOF Method

2017 ◽  
Author(s):  
Muthuselvan Govindaraj ◽  
Muralidhara Halebidu Suryanarayanarao ◽  
Prateekkumar Kotegar ◽  
Sonali Gupta ◽  
Sanjay Shankar ◽  
...  
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Computational Analysis ◽  
Cross Flow ◽  
Flux Ratio ◽  
Experimental Results ◽  
Liquid Jet ◽  
Computational Domain ◽  
Breakup Process ◽  
Primary Breakup

The main objective of this computational analysis is to investigate the effect of increase in Weber number at constant momentum flux ratio on the primary breakup process and deformation of kerosene jet in cross stream air flow. Unsteady computational analysis with VOF approach is carried out to simulate the two phase flow at three different cross flow Weber number conditions (150, 350 and 400) at constant momentum flux ratio of 17. Since the results of VOF technique is highly sensitive to the size and distribution of grid, grid optimization process is carried out, with both structured and unstructured forms of the grid. Since the structured grid with number of elements 17,96,181 displayed better matching with experimental results of upper trajectory of kerosene jet; this grid is used to investigate the effect of turbulence model and Weber number on the windward trajectory of kerosene jet in cross flow air stream. Initially to evaluate the results of computational analysis; simulations are carried out with larger computational domain (with number of elements 17,96,181). Windward trajectory of computational analysis is compared with experimental results of upper trajectory predicted using image processing technique and reasonable overall matching is observed. To investigate the primary breakup process and deformation of liquid jet at three different increasing Weber number conditions, simulations are carried out with smaller computational domain with higher mesh density with number of elements 33,96,146. The computational technique used in the present analysis exactly captures the modes of breakup observed from experimental results at different Weber number operating conditions. To characterize the deformation of liquid jet at different Weber number conditions; near-field trajectory, cross stream dimension and wave length of liquid jet are quantified at different instants of time. With increase in Weber number, decrease in penetration of liquid jet along transverse direction and more bending of liquid jet along flow direction is observed. From the velocity profile along transverse direction of three different conditions, stronger shearing of liquid film is observed in higher Weber number conditions.

A Model for Predicting the Lift-Off Height of Premixed Jets in Vitiated Cross Flow

2015 ◽  
Author(s):  
Michael Kolb ◽  
Denise Ahrens ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Time Scale ◽  
Ignition Delay ◽  
Gas Turbines ◽  
Cross Flow ◽  
Flame Stabilization ◽  
Staged Combustion ◽  
Flow Temperature ◽  
Jet Flame ◽  
Stage Combustion ◽  
Lift Off

Lean premixed single-stage combustion is state of the art for low pollution combustion in heavy-duty gas turbines with gaseous fuels. The application of premixed jets in multi-stage combustion to lower nitric oxide emissions and enhance turndown ratio is a novel promising approach. At the Lehrstuhl für Thermodynamik, Technische Universität München, a large scale atmospheric combustion test rig has been set up for studying staged combustion. The understanding of lift-off behavior is crucial for determining the amount of mixing before ignition and for avoiding flames anchoring at the combustor walls. This experiment studies jet lift-off depending on jet equivalence ratio (0.58–0.82), jet preheat temperature (288–673 K), cross flow temperature (1634–1821 K) and jet momentum ratio (6–210). The differences to existing lift-off studies are the high cross flow temperature and applying a premixed jet. The lift-off height of the jet flame is determined by OH* chemiluminescence images, and subsequently, the data is used to analyze the influence of each parameter and to develop a model that predicts the lift-off height for similar staged combustion systems. A main outcome of this work is that the lift-off height in a high temperature cross flow cannot be described by one dimensionless number like Damköhler- or Karlovitz number. Furthermore, the ignition delay time scale τign also misses part of the lift-off height mechanism. The presented model uses turbulent time scales, the ignition delay and a chemical time scale based on the laminar flame speed. An analysis of the model reveals flame stabilization mechanisms and explains the importance of different time scale.

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