Effect of an inhibitor on high-speed turbulent flames and the transition to detonation

Shock Waves ◽  
1996 ◽  
Vol 5 (5) ◽  
pp. 305-309
Author(s):  
M.H. Johnston ◽  
F. Zhang ◽  
D.L. Frost ◽  
J.H.S. Lee
Keyword(s):  
High Speed ◽  
Turbulent Flames ◽  
Transition To Detonation

Effect of an inhibitor on high-speed turbulent flames and the transition to detonation

Shock Waves ◽  
1996 ◽  
Vol 5 (5) ◽  
pp. 305-309 ◽  
Author(s):  
M. H. Johnston ◽  
F. Zhang ◽  
D. L. Frost ◽  
J. H. S. Lee
Keyword(s):  
High Speed ◽  
Turbulent Flames ◽  
Transition To Detonation

The Structure and Propagation Mechanism of Turbulent Flames in High Speed Flow

1955 ◽  
Vol 25 (8) ◽  
pp. 377-384 ◽  
Author(s):  
MARTIN SUMMERFIELD ◽  
SYDNEY H. REITER ◽  
VICTOR KEBELY ◽  
RICHARD W. MASCOLO
Keyword(s):  
High Speed ◽  
Turbulent Flames ◽  
Propagation Mechanism ◽  
High Speed Flow ◽  
Speed Flow

The Effect of Lewis Number on Instantaneous Flamelet Speed and Position Statistics in Counter-Flow Flames With Increasing Turbulence

2017 ◽  
Author(s):  
Sean D. Salusbury ◽  
Ehsan Abbasi-Atibeh ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Flame Front ◽  
Turbulence Intensity ◽  
High Speed ◽  
Rayleigh Scattering ◽  
Turbulent Flame ◽  
Lewis Number ◽  
Turbulent Flames ◽  
Flame Speed ◽  
Laminar Flames ◽  
Counter Flow

Differential diffusion effects in premixed combustion are studied in a counter-flow flame experiment for fuel-lean flames of three fuels with different Lewis numbers: methane, propane, and hydrogen. Previous studies of stretched laminar flames show that a maximum reference flame speed is observed for mixtures with Le ≳ 1 at lower flame-stretch values than at extinction, while the reference flame speed for Le ≪ 1 increases until extinction occurs when the flame is constrained by the stagnation point. In this work, counter-flow flame experiments are performed for these same mixtures, building upon the laminar results by using variable high-blockage turbulence-generating plates to generate turbulence intensities from the near-laminar u′/SLo=1 to the maximum u′/SLo achievable for each mixture, on the order of u′/SLo=10. Local, instantaneous reference flamelet speeds within the turbulent flame are extracted from high-speed PIV measurements. Instantaneous flame front positions are measured by Rayleigh scattering. The probability-density functions (PDFs) of instantaneous reference flamelet speeds for the Le ≳ 1 mixtures illustrate that the flamelet speeds are increasing with increasing turbulence intensity. However, at the highest turbulence intensities measured in these experiments, the probability seems to drop off at a velocity that matches experimentally-measured maximum reference flame speeds in previous work. In contrast, in the Le ≪ 1 turbulent flames, the most-probable instantaneous reference flamelet speed increases with increasing turbulence intensity and can, significantly, exceed the maximum reference flame speed measured in counter-flow laminar flames at extinction, with the PDF remaining near symmetric for the highest turbulence intensities. These results are reinforced by instantaneous flame position measurements. Flame-front location PDFs show the most probable flame location is linked both to the bulk flow velocity and to the instantaneous velocity PDFs. Furthermore, hydrogen flame-location PDFs are recognizably skewed upstream as u′/SLo increases, indicating a tendency for the Le ≪ 1 flame brush to propagate farther into the unburned reactants against a steepening average velocity gradient.

scholarly journals High-speed, three-dimensional tomographic laser-induced incandescence imaging of soot volume fraction in turbulent flames

2016 ◽  
Vol 24 (26) ◽  
pp. 29547 ◽  
Author(s):  
Terrence R. Meyer ◽  
Benjamin R. Halls ◽  
Naibo Jiang ◽  
Mikhail N. Slipchenko ◽  
Sukesh Roy ◽  
...  
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Laser Induced Incandescence

scholarly journals Large vapour cloud explosions, with particular reference to that at Buncefield

2012 ◽  
Vol 370 (1960) ◽  
pp. 544-566 ◽  
Author(s):  
D. Bradley ◽  
G. A. Chamberlain ◽  
D. D. Drysdale
Keyword(s):  
Land Use Planning ◽  
High Speed ◽  
Phase 1 ◽  
Turbulent Flames ◽  
Major Incident ◽  
Advisory Group ◽  
Storage Site ◽  
Two Phase ◽  
Underlying Mechanisms ◽  
The Uk

This paper first briefly surveys the energy releases in some major accidents. It then examines the analyses of the explosion at the Buncefield fuel storage site in the UK, one of the most intense accidental explosions in recent times. This followed the release of approximately 300 tonnes of winter-grade gasoline, when a 15 m high storage tank was overfilled for about 40 min before ignition of the resulting flammable mixture. The ensuing explosion was of a severity that had not been identified previously in a major hazard assessment of this type of facility. It was therefore imperative to investigate the event thoroughly and develop an understanding of the underlying mechanisms to inform future prevention, mitigation and land-use planning issues. The investigation of the incident was overseen by the Buncefield Major Incident Investigation Board. A separate Explosion Mechanism Advisory Group examined the evidence and reported on the severity of the explosion. It concluded that additional work was necessary and recommended that a two-stage project be initiated, phase 1 of which has been completed. The analyses of the damage and the derivation of explosion over-pressures are described. Possible explosion mechanisms and the evidence for them at Buncefield are discussed, in the light of other major incidents. Mechanisms that are reviewed include high-speed turbulent combustion, quasi-detonations, fully developed detonations, the generation of fireballs, flame instabilites, radiative heat transfer and aspects of two-phase burning. Of particular importance is the acceleration of turbulent flames along the line of trees and hedgerows. A number of conclusions are drawn and suggestions made for further research.

Propagation of Turbulent Natural Gas/Air Flames in Tubing With 90° Bends

2003 ◽  
Vol 125 (4) ◽  
pp. 304-310
Author(s):  
Michael D. Morgan ◽  
S. A. (Raj) Mehta ◽  
T. J. Al-Himyary ◽  
R. G. (Gord) Moore
Keyword(s):  
Natural Gas ◽  
High Speed ◽  
Small Diameter ◽  
Industrial Applications ◽  
Turbulent Flames ◽  
Process Equipment ◽  
Pressure Data ◽  
Flammable Gas ◽  
Internal Volume ◽  
Temperature Responses

Anytime flammable gas mixtures are handled, there is a risk of combustion. This is particularly true in many industrial applications where space is limited and equipment is located near sources of ignition. Unfortunately, there is a lack of understanding of combustion phenomena within process equipment such as mufflers, rotating blowout preventers, liquid traps, and dry gas seal assemblies. These vessels have small internal volumes, complex internal geometries, and are connected using small diameter piping. This paper discusses the results of a parametric study which was carried out to establish the nature of combustion within such vessels and tubing. The test vessel had an internal volume of 7 in3 (115 ml) and the tubing had a nominal diameter of 0.5 in (1.27 mm). Flowing, turbulent, pre-mixed natural gas/air mixtures were used. The study did not attempt to increase turbulence using devices such as mesh screens or attempt to stabilize the flame. The results from a representative sample of 76 tests, from the 5,000+ tests that have been completed, are discussed herein. Typical pressure and temperature responses are presented and analyzed. It is demonstrated that flames can be remotely detected using only high speed pressure data. Turbulent flames were formed whose velocity was found to be linearly dependant on Reynolds number.

Fuel Variation Effects in Propagation and Stabilization of Turbulent Counter-Flow Premixed Flames

2018 ◽  
Author(s):  
Ehsan Abbasi-Atibeh ◽  
Sandeep Jella ◽  
Jeffrey M. Bergthorson
Keyword(s):  
High Speed ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Mass Diffusion ◽  
Flame Stabilization ◽  
Turbulent Flames ◽  
Flame Speed ◽  
Flame Surface ◽  
Differential Diffusion ◽  
Turbulent Flame Speed

Sensitivity to stretch and differential diffusion of chemical species are known to influence premixed flame propagation, even in the turbulent environment where mass diffusion can be greatly enhanced. In this context, it is convenient to characterize flames by their Lewis number (Le), a ratio of thermal-to-mass diffusion. The work reported in this paper describes a study of flame stabilization characteristics when the Le is varied. The test data is comprised of Le ≪ 1 (Hydrogen), Le ≈ 1 (Methane), and Le > 1 (Propane) flames stabilized at various turbulence levels. The experiments were carried out in a Hot exhaust Opposed-flow Turbulent Flame Rig (HOTFR), which consists of two axially-opposed, symmetric turbulent round jets. The stagnation plane between the two jets allows the aerodynamic stabilization of a flame, and clearly identifies fuel influences on turbulent flames. Furthermore, high-speed Particle Image Velocimetry (PIV), using oil droplet seeding, allowed simultaneous recordings of velocity (mean and rms) and flame surface position. These experiments, along with data processing tools developed through this study, illustrated that in the mixtures with Le ≪ 1, turbulent flame speed increases considerably compared to the laminar flame speed due to differential diffusion effects, where higher burning rates compensate for the steepening average velocity gradient, and keeps these flames almost stationary as bulk flow velocity increases. These experiments are suitable for validating the ability of turbulent combustion models to predict lifted, aerodynamically-stabilized flames. In the final part of this paper, we model the three fuels at two turbulence intensities using the FGM model in a RANS context. Computations reveal that the qualitative flame stabilization trends reproduce the effects of turbulence intensity, however, more accurate predictions are required to capture the influences of fuel variations and differential diffusion.

Influence of Air and Fuel Mass Flow Fluctuations in a Premix Swirl Burner on Flame Dynamics

2006 ◽  
Author(s):  
M. P. Auer ◽  
C. Hirsch ◽  
T. Sattelmayer
Keyword(s):  
Heat Release ◽  
Mass Flow ◽  
High Speed ◽  
Structural Changes ◽  
Flame Structure ◽  
Flame Length ◽  
Turbulent Flames ◽  
Swirl Burner ◽  
Fuel Mass ◽  
Flame Dynamics

This paper discusses the structural changes observed in oscillating premixed turbulent swirling flames and demonstrates the influence of modulated mass flows on the flame dynamics in a preheated atmospheric test rig with a natural gas fired swirl burner. The experimentally investigated self excited and forced combustion oscillations of swirl stabilized premixed flames show varying time delays between the acoustically driven mass flow oscillations and the integral heat release rate of the flame. High speed films of the OH*-chemiluminescence reveal how the flame structure changes with the oscillation frequency and the phase angle between the fuel mass flow oscillation and the total mass flow at the burner exit. These parameters are found determine the spatial and temporal heat release distribution and thus the net heat release fluctuation. Therefore, the spatial and temporal heat release distribution along the flame length has an influence on the thermoacoustic coupling, even in the case of acoustically compact flames. The observed phenomena are discussed further using an 1-d analytical model. It underscores that for swirl stabilized premixed turbulent flames the dynamics of the flow field perturbation play a major role in creating the effective heat release fluctuation.

Fiber-Coupled High-Speed OH-PLIF Imaging in Turbulent Flames

2012 ◽  
Author(s):  
Paul Hsu ◽  
Waruna Kulatilaka ◽  
Naibo Jiang ◽  
Stanislav Kostka ◽  
Sukesh Roy ◽  
...  
Keyword(s):  
High Speed ◽  
Turbulent Flames
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