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

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.

scholarly journals Observations on Jet-Flame Blowout

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
N. J. Moore ◽  
J. L. McCraw ◽  
K. M. Lyons
Keyword(s):  
Reaction Zone ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Leading Edge ◽  
Transient Behavior ◽  
Turbulent Flames ◽  
Ignition Source ◽  
Jet Flame ◽  
Physically Based ◽  
Air Diffusion

The mechanisms that cause jet-flame blowout, particularly in the presence of air coflow, are not completely understood. This work examines the role of fuel velocity and air coflow in the blowout phenomenon by examining the transient behavior of the reaction zoneat blowout. The results of video imaging of a lifted methane-air diffusion flame at near blowout conditions are presented. Two types of experiments are described. In the first investigation, a flame is established and stabilized at a known, predetermined downstream location with a constant coflow velocity, and then the fuel velocity is subsequently increased to cause blowout. In the other, an ignition source is used to maintain flame burning near blowout and the subsequent transient behavior to blowout upon removal of the ignition source is characterized. Data from both types of experiments are collected at various coflow and jet velocities. Images are used to ascertain the changes in the leading edge of the reaction zone prior to flame extinction that help to develop a physically-based model to describe jet-flame blowout. The data report that a consistent predictor of blowout is the prior disappearance of the axially oriented flame branch. This is witnessed despite a turbulent flames' inherent variable behavior. Interpretations are also made in the light of analytical mixture fraction expressions from the literature that support the notion that flame blowout occurs when the leading edge reaches the vicinity of the lean-limit contour, which coincides approximately with the conditions for loss of the axially oriented flame structure.

URANS Simulation of an Appended Hull During Steady Turn With Propeller Represented by an Actuator Disk Model

2011 ◽  
Author(s):  
Charles M. Dai ◽  
Ronald W. Miller
Keyword(s):  
Flow Field ◽  
Cross Flow ◽  
Field Measurements ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Complex Flow ◽  
Ship Maneuvering ◽  
Disk Model ◽  
Actuator Disk ◽  
Propeller Wake

This paper reports on the comparison between computational simulations and experimental measurements of a surface vessel in steady turning conditions. The primary purpose of these efforts is to support the development of physics-based high fidelity maneuvering simulation tools by providing accurate and reliable hydrodynamic data with relevance to maneuvering performances. Reynolds Averaged Unsteady Navier Stokes Solver (URANS): CFDSHIPIOWA was used to perform simulations for validation purposes and for better understanding of the fundamental flow physics of a hull under maneuvering conditions. The Propeller effects were simulated using the actuator disk model included in CFDShip-Iowa. The actuator disk model prescribes a circumferential averaged body force with axial and tangential components. No propeller generated side forces are accounted for in the model. This paper examines the effects of actuator disk model on the overall fidelity of a RANS based ship maneuvering simulations. Both experiments and simulations provide physical insights into the complex flow interactions between the hull and various appendages, the rudders and the propellers. The experimental effort consists of flow field measurements using Stereo Particle-Image Velocimetry (SPIV) in the stern region of the model and force and moment measurements on the whole ship and on ship components such as the bilge keels, the rudders, and the propellers. Comparisons between simulations and experimental measurements were made for velocity distributions at different transverse planes along the ship axis and different forces components for hull, appendages and rudders. The actuator disk model does not predict any propeller generated side forces in the code and they need to be taken into account when comparing hull and appendages generated side forces in the simulations. The simulations were compared with experimental results and they both demonstrate the cross flow effect on the transverse forces and the propeller slip streams generated by the propellers during steady turning conditions. The hull forces (include hull, bilge keels, skeg, shafting and strut) predictions were better for large turning circle case as compared with smaller turning circle. Despite flow field simulations appear to capture gross flow features qualitatively; detailed examinations of flow distributions reveal discrepancies in predictions of propeller wake locations and secondary flow structures. The qualitative comparisons for the rudders forces also reveal large discrepancies and it was shown that the primary cause of discrepancies is due to poor predictions of velocity inflow at the rudder plane.

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.

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.

Investigation of Flow Characteristics in a Combustor With Opposed Jets

2018 ◽  
Author(s):  
Yongbin Ji ◽  
Bing Ge ◽  
Shusheng Zang
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Momentum Flux ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Flux Ratio ◽  
Main Flow ◽  
3D Flow ◽  
Momentum Flux Ratio ◽  
High Efficient

Jet-in-cross flow (JICF) has been investigated broadly because of its wide engineering application, for example in the gas turbine field, film cooling on the turbine vanes and blades, primary and dilution jets in the combustors and so on. In the gas turbine combustors, the main flow is generated by the swirlers to stabilize the flame, which induces complicated 3D flow characteristics. Different from uniform main flow, swirling cross flow has a strong tangential velocity component, which will deflect the jets in the circumferential direction as well as in the streamwise direction. So, the degradation behavior of the jets is more complex than that in the uniform cross flow. This paper presents PIV measurement of the flow field inside of a three-nozzle annular combustor with opposed quenching jets on the liner walls. Dry ice as a newly proposed flow tracer was proposed and tried. The momentum flux ratio and jet holes configuration are studied to evaluate their effects on the primary recirculation zone, downstream flow field. Finally, numerical simulation was also performed to reveal 3D flow characteristics as well as turbulent kinetic energy generation. The results show that momentum flux ratio has a dominant influence on flow characteristics in the combustor. Getting better understanding of jets behavior in the swirling cross flow helps optimization design of quenching or dilution holes geometry and arrangement for the gas turbine combustor, which turns to be very beneficial to the low-emission and high efficient combustor development.

Thermal Performance of Multipass Parallel and Counter-Cross-Flow Heat Exchangers

2006 ◽  
Vol 129 (3) ◽  
pp. 282-290 ◽  
Author(s):  
Luben Cabezas-Gómez ◽  
Hélio Aparecido Navarro ◽  
José Maria Saiz-Jabardo
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Experimental Studies ◽  
Cross Flow ◽  
Numerical Procedure ◽  
Complex Flow ◽  
Flow Heat ◽  
Small Elements ◽  
Effectiveness Data

A thorough study of the thermal performance of multipass parallel cross-flow and counter-cross-flow heat exchangers has been carried out by applying a new numerical procedure. According to this procedure, the heat exchanger is discretized into small elements following the tube-side fluid circuits. Each element is itself a one-pass mixed-unmixed cross-flow heat exchanger. Simulated results have been validated through comparisons to results from analytical solutions for one- to four-pass, parallel cross-flow and counter-cross-flow arrangements. Very accurate results have been obtained over wide ranges of NTU (number of transfer units) and C* (heat capacity rate ratio) values. New effectiveness data for the aforementioned configurations and a higher number of tube passes is presented along with data for a complex flow configuration proposed elsewhere. The proposed procedure constitutes a useful research tool both for theoretical and experimental studies of cross-flow heat exchangers thermal performance.

Experimental Investigation of a Generic Compressor Bleed System

2006 ◽  
Author(s):  
Reinaldo A. Gomes ◽  
Carsten Schwarz ◽  
Michael Pfitzner
Keyword(s):  
Flow Field ◽  
Annular Flow ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Complex Flow ◽  
Pressure Losses ◽  
Aero Engines

Extensive experimental studies on axial compressor bleed-flow systems have been carried out on a three dimensional model of a generic bleed-flow configuration typical for aero engines. The compressor flow is modeled as a clean annular flow. One row of stator vanes is used to impart a constant swirl upstream of the bleed system. The rig is designed modularly in order to allow for inexpensive changes in all of its components and therefore to enlarge the variability of the model. The research is focused onto the generation of an experimental data base, which can be used to derive correlations for the calculation of effective areas and pressure losses. Those data are gained using steady pneumatic measurement technique. In addition, the highly complex flow field in the manifold, which has an important effect onto the bleed-flow, is analyzed using Doppler-Global-Velocimetry (DGV). These measurements were conducted in collaboration with DLR Cologne, who have developed the DGV technique. In this paper the flow field in the manifold is analyzed in detail for two different configurations featuring two and four bleed ducts, respectively. Furthermore the use of a flush design of the slot is compared with a lip design. These data are compared to results from the literature achieved using 2-dimensional configurations.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2005 ◽  
Vol 127 (1) ◽  
pp. 187-196 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven nonpremixed turbulent flames.

scholarly journals Pitched and Yawed Circular Jets in Cross-Flow

2002 ◽  
Author(s):  
Ivana M. Milanovic ◽  
K. B. M. Q. Zaman
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Momentum Flux ◽  
Cross Flow ◽  
Flux Ratio ◽  
Streamwise Velocity ◽  
Streamwise Vorticity ◽  
Downstream Distance ◽  
Circular Jets

Results from an experimental investigation of flow field generated by pitched and yawed jets discharging from a flat plate into a cross-flow are presented. The circular jet was pitched at α = 20° and 45° and yawed between β = 0° and 90° in increments of 15°. The measurements were performed with two X-wires providing all three components of velocity and turbulence intensity. These data were obtained at downstream locations of x = 3, 5, 10 and 20, where the distance x, normalized by the jet diameter, is measured from the center of the orifice. Data for all configurations were acquired at a momentum-flux ratio J = 8. Additionally, for selected angles and locations, surveys were conducted for J = 1.5, 4, and 20. As expected, the jet penetration is found to be higher at larger α. With increasing β the jet spreads more. The rate of reduction of peak streamwise vorticity, ωxmax, with the downstream distance is significantly lessened at higher β but is found to be practically independent of α. Thus, at the farthest measurement station x = 20, ωxmax is about five times larger for β = 75° compared to the levels at β = 0°. Streamwise velocity within the jet-vortex structure is found to depend on the parameter J. At J = 1.5 and 4, ‘wake-like’ velocity profiles are observed. In comparison, a ‘jet-like’ overshoot is present at higher J.

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