Mixture Fraction Imaging of Distributed Regime Turbulent Jet Flame using Rayleigh Scattering

2020 ◽  
Author(s):  
Abinash Sahoo ◽  
Venkateswaran Narayanaswamy ◽  
Aravind Ramachandran ◽  
Kevin Lyons
Keyword(s):  
Rayleigh Scattering ◽  
Mixture Fraction ◽  
Turbulent Jet ◽  
Jet Flame

scholarly journals Consistent Conditional Moment Closure Modelling of a Lifted Turbulent Jet Flame Using the Presumedβ-PDF Approach

2014 ◽  
Vol 2014 ◽  
pp. 1-25 ◽  
Author(s):  
Ahmad El Sayed ◽  
Roydon A. Fraser
Keyword(s):  
Mixture Fraction ◽  
Turbulent Jet ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Conditional Moment ◽  
Jet Flame ◽  
Gradient Diffusion ◽  
Conditional Moment Closure ◽  
History Of ◽  
Closure Modelling

A liftedH2/N2turbulent jet flame issuing into a vitiated coflow is investigated using the conditional moment closure. The conditional velocity (CV) and the conditional scalar dissipation rate (CSDR) submodels are chosen such that they are fully consistent with the moments of the presumedβprobability density function (PDF). The CV is modelled using the PDF-gradient diffusion model. Two CSDR submodels based on the double integration of the homogeneous and inhomogeneous mixture fraction PDF transport equations are implemented. The effect of CSDR modelling is investigated over a range of coflow temperatures (Tc) and the stabilisation mechanism is determined from the analysis of the transport budgets and the history of radical build-up ahead of the stabilisation height. For allTc, the balance between chemistry, axial convection, and micromixing, and the absence of axial diffusion upstream of the stabilisation height indicate that the flame is stabilized by autoignition. This conclusion is confirmed from the rapid build-up ofHO2ahead ofH,O, andOH. The inhomogeneous CSDR modelling yields higher dissipation levels at the most reactive mixture fraction, which results in longer ignition delays and larger liftoff heights. The effect of the spurious sources arising from homogeneous modelling is found to be small but nonnegligible, mostly notably within the flame zone.

Hydrodynamic instability and shear layer effect on the sound emission of a turbulent jet flame

2015 ◽  
Author(s):  
Stephan Schlimpert ◽  
Seong Ryong Koh ◽  
Antje Feldhusen ◽  
Benedikt Roidl ◽  
Matthias H. Meinke ◽  
...  
Keyword(s):  
Shear Layer ◽  
Hydrodynamic Instability ◽  
Turbulent Jet ◽  
Sound Emission ◽  
Jet Flame ◽  
Layer Effect

scholarly journals Effect of Temperature Conditions on Flame Evolutions of Turbulent Jet Ignition

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2226
Author(s):  
Jiaying Pan ◽  
Yu He ◽  
Tao Li ◽  
Haiqiao Wei ◽  
Lei Wang ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Early Stage ◽  
Turbulent Jet ◽  
Combustion Stability ◽  
Effect Of Temperature ◽  
Main Chamber ◽  
Detailed Chemical Kinetics ◽  
Jet Flame ◽  
Spherical Flame ◽  
Temperature Conditions

Turbulent jet ignition technology can significantly improve lean combustion stability and suppress engine knocking. However, the narrow jet channel between the pre-chamber and the main chamber leads to some difficulties in heat exchange, which significantly affects combustion performance and mechanical component lifetime. To clarify the effect of temperature conditions on combustion evolutions of turbulent jet ignition, direct numerical simulations with detailed chemical kinetics were employed under engine-relevant conditions. The flame propagation in the pre-chamber and the early-stage turbulent jet ignition in the main chamber were investigated. The results show that depending on temperature conditions, two types of flame configuration can be identified in the main chamber, i.e., the normal turbulent jet flame propagation and the spherical flame propagation, and the latter is closely associated with pressure wave disturbance. Under low-temperature conditions, the cold jet stoichiometric mixtures and the vortexes induced by the jet flow determine the early-stage flame development in the main chamber. Under intermediate temperature conditions, pre-flame heat release and leading pressure waves are induced in the jet channel, which can be regarded as a transition of different combustion modes. Whereas under high-temperature conditions, irregular auto-ignition events start to occur, and spherical flame fronts are induced in the main chamber, behaving faster flame propagation.

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.

Steady-State Simulation of a Methane-Air Partially Premixed Turbulent Flame

2001 ◽  
Author(s):  
Graham Goldin ◽  
Dipankar Choudhury
Keyword(s):  
Steady State ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Equilibrium Mixture ◽  
Flamelet Model ◽  
Jet Flame ◽  
Partially Premixed ◽  
Partially Premixed Flame ◽  
Steady State Simulation ◽  
Laminar Flamelet

Abstract Two steady-state simulations of a benchmark (Sandia Flame D) methane-air, turbulent, partially premixed flame are compared. The first uses an equilibrium mixture fraction model for the thermo-chemistry, while the second uses a steady, strained laminar-flamelet model. These non-premixed combustion models are coupled with a premixed reaction progress model to simulate a partially premixed jet flame. The laminar-flamelet approach predicts CO and H2 more accurately than the equilibrium model by accounting for the unbumt premixed stream within individual flamelets, and improved radical (such as OH) predictions by incorporating non-equilibrium chemistry effects due aerodynamic strain (fluid shear).

Evaluation of a Turbulent Jet Flame Flashback Correlation Applied to Annular Flow Configurations With and Without Swirl

2021 ◽  
Author(s):  
Vincent McDonell ◽  
Elliot Sullivan-Lewis ◽  
Alireza Kalantari ◽  
Priyank Saxena
Keyword(s):  
Annular Flow ◽  
Turbulent Jet ◽  
Jet Flame ◽  
Flow Configurations ◽  
Flame Flashback

Simulation of Methanol-Air Two-Phase Flames Using Various Turbulent Combustion Models

2009 ◽  
Author(s):  
F. Wang ◽  
Y. Huang ◽  
Y. Z. Wu
Keyword(s):  
Experimental Data ◽  
Turbulent Combustion ◽  
Turbulent Jet ◽  
Combustion Model ◽  
Air Flow Rate ◽  
Two Phase ◽  
Jet Flame ◽  
Combustion Simulation ◽  
Turbulent Combustion Model ◽  
Turbulent Models

Though fossil fuel is running out, liquid fuels nowadays still provide the most energy used by industrial furnaces, automotive and aero engines. How to predict a two-phase turbulent combustion flame is still a big problem to designers. Generally, the liquid fuel is sprayed and mixed with oxygen, and the flame characteristics depends on the fuel atomization, the fuel droplet spatial distribution, and its interaction with the turbulent oxidizer flow field: turbulent heat, mass and momentum transfer, complicated chemical kinetics, and turbulent-chemistry interaction. Turbulent combustion model is a key point for the two phase combustion simulation. For its short time consuming, Reynolds Averaged Navier Stokes (RANS) method nowadays still is the major tool for gas turbine chamber (GTC) designers, but there is not a universal method in RANS GTC spray combustion simulation at present especially for the two-phase turbulent combustion. The Eddy-Break-Up turbulent combustion model (EBU), Eddy Dissipation Concept turbulent combustion model (EDC), steady Laminar Flame-let turbulent combustion Model (LFM) and the Composition PDF transport turbulent combustion model (CPDF) are all widely used models. In this paper, these four turbulent models are used to simulate a methane-air turbulent jet flame measured by Sandia Lab first, then three methanol-air two-phase turbulent flames, in order to know the ability of these turbulent models. In the gas turbulent jet flame simulation, the result of LFM model and CPDF model are in better agreement with the experimental data than those of the EBU and the EDC models’ results. The reason is that the EBU model and EDC model are overestimated the effect of turbulent. In the three different cases of the two phase combustion simulation, CPDF is the best. The prediction ability of the other three models is different in different cases. The EDC predictions are closer to the experimental data when the air flow rate value is lower, whereas the LFM predictions are better when the air flow rate value is higher.

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