Effects of leading edge entrainment on the double flame structure in lifted ethanol spray flames

2004 ◽  
Vol 29 (1) ◽  
pp. 23-31 ◽  
Author(s):  
S.K. Marley ◽  
E.J. Welle ◽  
K.M. Lyons ◽  
W.L. Roberts
Keyword(s):  
Flame Structure ◽  
Leading Edge ◽  
Spray Flames

Combustion Structures in Lifted Ethanol Spray Flames

2004 ◽  
Vol 126 (2) ◽  
pp. 254-257 ◽  
Author(s):  
Stephen K. Marley ◽  
Eric J. Welle ◽  
Kevin M. Lyons
Keyword(s):  
Reaction Zone ◽  
Flame Structure ◽  
Leading Edge ◽  
Laser Induced Fluorescence ◽  
Premixed Combustion ◽  
Diffusion Mode ◽  
Spray Flames ◽  
Partially Premixed Combustion ◽  
Planar Laser ◽  
Single Reaction

The development of a double flame structure in lifted ethanol spray flames is visualized using OH planar laser-induced fluorescence (PLIF). While the OH images indicate a single reaction zone exists without co-flow, the addition of low-speed co-flow facilitates the formation of a double flame structure that consists of two diverging flame fronts originating at the leading edge of the reaction zone. The outer reaction zone burns steadily in a diffusion mode, and the strained inner flame structure is characterized by both diffusion and partially premixed combustion exhibiting local extinction and re-ignition events.

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.

Theoretical and numerical analysis of a spreading opposed-flow diffusion flame

2009 ◽  
Vol 465 (2110) ◽  
pp. 3209-3238 ◽  
Author(s):  
Yang Long ◽  
Indrek S. Wichman
Keyword(s):  
Heat Flux ◽  
Solid Fuel ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Leading Edge ◽  
Species Distributions ◽  
Variable Density ◽  
Simulation Code ◽  
Total Enthalpy ◽  
Numerical Predictions

This article describes the macroscopic and microscopic features of flames spreading over solid-fuel surfaces by examining and comparing three models. The first model examines ignition and flame spread over a solid-fuel surface using a two-dimensional numerical simulation code. This model employs variable density, variable thermophysical properties and one-step global finite-rate chemistry. The second model, a macroscopic ‘field’ model, is solved in terms of the mixture fraction ( Z ) and total enthalpy ( H ) functions. Comparisons are made with numerical predictions for primitive quantities: temperature, species distributions and velocity fields; and derived quantities: heat flux, mass flux, mixture fraction, enthalpy function and flame stretch rate. The third model yields a ‘localized’ flame structure description near the flame attachment point. Theoretical formulas are produced for the quenching distance, the leading edge heat flux, and the flame structure, as characterized by reactivity, temperature field and species distributions. The analytical predictions are compared with numerical simulations to derive flame microstructure scaling parameters.

Spray Flame Study Using a Model Gas Turbine Swirl Burner

2013 ◽  
Vol 316-317 ◽  
pp. 17-22 ◽  
Author(s):  
Cheng Tung Chong ◽  
Simone Hochgreb
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Flame Structure ◽  
Fuel Droplets ◽  
Spray Flame ◽  
Spray Flames ◽  
Reaction Zones ◽  
Fixed Power ◽  
Particle Imaging ◽  
Gas Turbine Burner

A model gas turbine burner was employed to investigate spray flames established under globally lean, continuous, swirling conditions. Two types of fuel were used to generate liquid spray flames: palm biodiesel and Jet-A1. The main swirling air flow was preheated to 350 °C prior to mixing with airblast-atomized fuel droplets at atmospheric pressure. The global flame structure of flame and flow field were investigated at the fixed power output of 6 kW. Flame chemiluminescence imaging technique was employed to investigate the flame reaction zones, while particle imaging velocimetry (PIV) was utilized to measure the flow field within the combustor. The flow fields of both flames are almost identical despite some differences in the flame reaction zones.

Leading-Edge Reaction Zones in Lifted-Jet Gas and Spray Flames

2004 ◽  
Vol 72 (1) ◽  
pp. 29-47 ◽  
Author(s):  
S.K. Marley ◽  
K.M. Lyons ◽  
K.A. Watson
Keyword(s):  
Leading Edge ◽  
Spray Flames ◽  
Reaction Zones

Effect of Swirl and Fuel Pulsation on Flow Dynamics, Flame Structure and Droplet Motion in Swirl-Stabilized Spray Flames

2004 ◽  
Author(s):  
Martin B. Linck ◽  
Michael D. Armani ◽  
Ashwani K. Gupta
Keyword(s):  
Passive Control ◽  
Swirling Flow ◽  
Droplet Diameter ◽  
Combustion Instability ◽  
Flame Structure ◽  
High Shear ◽  
Droplet Dynamics ◽  
Spray Flames ◽  
Airflow Distribution

This paper describes an experimental investigation of the role of swirl distribution in a co-annular swirl-stabilized spray combustor for passive control of flame structure using kerosene fuel. Three distinctly different flames have been examined. A low shear, a high shear, and a counter-rotating swirling flow flame have been examined. The droplet dynamics and flowfield associated with the low and high shear co-rotating swirl configurations under isothermal and combustion conditions have been examined using a phase Doppler interferometric techniques. The high-shear swirl configuration was found to decrease droplet diameter in the shear region, indicating secondary atomization of larger size droplets due to strong shear effects in the flow. Droplet mean and turbulence characteristics were obtained. In order to simulate oscillations in the flow pulsations were introduced into the fuel flow in order to excite instabilities in the burner. The role of swirl distribution was determined on the attenuation of this imposed instability. Swirl distribution was found to be effective in reducing the instability. Instabilities at the forcing and harmonic frequencies are found to be up to 5 dB more powerful in the counter-rotating flow, demonstrating the role of swirl on flame structure and the associated combustion instability in swirl-stabilized spray combustors. The airflow distribution in the burner was also found to play an important role on the alleviation of combustion instability.

scholarly journals Effects of Pressure on Flame Structure and Droplet Behaviour of Coaxial Jet Spray Flames(Thermal Engineering)

2009 ◽  
Vol 75 (750) ◽  
pp. 354-362
Author(s):  
Mariko NAKAMURA ◽  
Yoshinori NAKAO ◽  
Daichi NISHIOKA ◽  
Seung-Min HWANG ◽  
Jun HAYASHI ◽  
...  
Keyword(s):  
Flame Structure ◽  
Thermal Engineering ◽  
Spray Flames

Comparison of the Combustion Characteristics of Liquid Single-Component Fuels in a Gas Turbine Model Combustor

2016 ◽  
Author(s):  
Jasper Grohmann ◽  
William O’Loughlin ◽  
Wolfgang Meier ◽  
Manfred Aigner
Keyword(s):  
Gas Turbine ◽  
Alternative Fuels ◽  
Numerical Models ◽  
Flame Structure ◽  
Mie Scattering ◽  
Single Component ◽  
Liquid Fuels ◽  
Reacting Flow ◽  
Spray Flames ◽  
Turbine Model

Alternative production pathways for liquid fuels provide the opportunity to adjust the chemical composition of the product in order to improve combustion performance. In this study, flame characteristics of selected single-component fuels were investigated to provide a basis for a better understanding of the influence of specific fuel components on the combustion behaviour. The measurements were performed in a redesigned gas turbine model combustor for swirl-stabilised spray flames under atmospheric pressure. The combustor features a dual-swirl geometry and a prefilming airblast atomiser. The combustion chamber provides good optical access and yields well-defined boundary conditions. As part of different projects in the field of alternative fuels, two liquid single-component fuels (n-hexane, n-dodecane) and kerosene Jet A-1 were investigated. Flow fields of the nonreacting and reacting flow were measured using stereo particle image velocimetry. The flame structure and spray distribution were derived from CH* chemiluminescence and Mie scattering respectively. Lean blowout limits were measured. Results show noticeable differences in combustion behaviour of the chosen fuels at comparable flow conditions. Furthermore, the results provide a detailed data base for the validation of numerical models.

Numerical and Theoretical Analysis of Laminar Counterflowing Spray Flames for Use in Turbulent Combustion Modeling

2014 ◽  
Author(s):  
Hernan Olguin ◽  
Philip Hindenberg ◽  
Eva Gutheil
Keyword(s):  
Numerical Simulations ◽  
Dissipation Rate ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Main Reaction ◽  
Computational Time ◽  
Scalar Dissipation ◽  
Scalar Dissipation Rate ◽  
Spray Flames

The paper presents a combined theoretical and numerical study of laminar counterflow mono-disperse spray flames. The numerical model includes a similarity transformation of the two-dimensional governing gas phase equations into a one-dimensional formulation. The reduced computational time enables the use of detailed chemical reaction mechanisms to study the spray flame structure. In particular, the effect of spray evaporation on combustion is investigated by means of numerical simulations. For this purpose, the transport equation of the scalar dissipation rate of the mixture fraction is derived, where the spray evaporation source term is included. Numerical simulations of laminar liquid and gaseous ethanol and combustion products mono disperse spray flames under fuel-rich conditions are presented and discussed. The parametric dependence of the flame structures on strain rate is studied with emphasis on the spray evaporation. Droplet reversal and oscillation are found to dominate the flame structure, and they determine the location of the main reaction zone as well as the profile of the scalar dissipation rate. The study aims to develop a novel spray flamelet model for use in the numerical simulations of turbulent spray combustion with particular emphasis on flameless conditions.

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