An Experimental Study on Properties of Local Burning Velocity for Hydrogen Added Hydrocarbon Premixed Turbulent Flames

2011 ◽  
Author(s):  
Masaya Nakahara ◽  
Koichi Murakami ◽  
Jun Hashimoto ◽  
Atsushi Ishihara
Keyword(s):  
Burning Velocity ◽  
Quantitative Relationship ◽  
Lewis Number ◽  
Turbulent Flames ◽  
Laminar Flames ◽  
Mean Values ◽  
Laser Tomography ◽  
Turbulence Condition ◽  
Turbulent Burning Velocity ◽  
Local Burning

This study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u′/SL0 = 1.4), in order to clarify basically the influence of the addition of hydrogen to methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δH are prepared. A two-dimensional sequential laser tomography technique is used to obtain the relationship between the flame shape and the flame displacement. The local flame displacement velocity SF is quantitatively obtained as the key parameters of the turbulent combustion. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effects of positive stretch and curvature on burning velocity. It was found that the trends of the mean values of measured SF with respect to δH, the total equivalence ratio Φ and fuel types corresponded well its turbulent burning velocity. The trend of the obtained Ma could explain the local burning velocity of turbulent flames only qualitatively. Based on the Ma, the local burning velocity at the part of turbulent flames with positive stretch and curvature, SLt, is estimated quantitatively. As a result, a quantitative relationship between the estimated SLt and the SF at positive stretch and curvature of turbulent flames could be observed for mixtures with increasing the Lewis number.

Flame stretch rate as a determinant of turbulent burning velocity

1992 ◽  
Vol 338 (1650) ◽  
pp. 359-387 ◽  
Keyword(s):  
Burning Velocity ◽  
Turbulent Flame ◽  
Lewis Number ◽  
Turbulent Flames ◽  
Stretch Rate ◽  
Dimensionless Groups ◽  
Flame Stretch ◽  
Experimental Values ◽  
Turbulent Burning Velocity

A rational basis for correlating turbulent burning velocities is shown to involve the product of the Karlovitz stretch factor and the Lewis number. A generalized expression is derived to show how flame stretch is related to the velocity field. A new dimensionless correlation of experimental values of turbulent burning velocities is presented. Dimensionless groups also are used in correlations of laminar and turbulent flame extinction stretch rates. A distribution function of stretch rates in turbulent flames, based on an earlier one of Yeung et al ., is proposed and the experimental data are well predicted by a theory based on flamelet extinction by flame stretch with this distribution. Uncertainties arise concerning the role of negative stretch rate. Laminar flamelet modelling of complex combustion appears to have a broader validity than might be expected and some explanation for this is offered.

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 Effect of Stretch on Local Burning Velocity of Premixed Turbulent Flames

2007 ◽  
Vol 2 (2) ◽  
pp. 268-280 ◽  
Author(s):  
Masaya NAKAHARA ◽  
Hiroyuki KIDO ◽  
Takamori SHIRASUNA ◽  
Koichi HIRATA
Keyword(s):  
Burning Velocity ◽  
Turbulent Flames ◽  
Premixed Turbulent Flames ◽  
Local Burning

412 Influence of Markstein Number on Local Burning Velocity of Premixed Turbulent Flames

2005 ◽  
Vol 2005.58 (0) ◽  
pp. 145-146
Author(s):  
Masaya NAKAHARA ◽  
Hiroyuki KIDO ◽  
Kenshiro NAKASHIMA ◽  
Hideaki TAKAMOTO ◽  
Koichi HIRATA
Keyword(s):  
Burning Velocity ◽  
Turbulent Flames ◽  
Premixed Turbulent Flames ◽  
Markstein Number ◽  
Local Burning

Lewis number effects on turbulent burning velocity

1985 ◽  
Vol 20 (1) ◽  
pp. 505-512 ◽  
Author(s):  
R.G. Abdel-Gayed ◽  
D. Bradley ◽  
M.N. Hamid ◽  
M. Lawes
Keyword(s):  
Burning Velocity ◽  
Lewis Number ◽  
Turbulent Burning Velocity

An experimental study of burner-stabilized turbulent flames in premixed reactants

1962 ◽  
Vol 268 (1333) ◽  
pp. 222-239 ◽  
Keyword(s):  
Burning Velocity ◽  
Short Circuit ◽  
Turbulent Flames ◽  
Laminar Flames ◽  
Small Scale ◽  
Light Sources ◽  
Gas Streams ◽  
Slow Flows ◽  
Mean Structure ◽  
Scale Turbulence

Current concepts of flame propagation in premixed, turbulent gas streams are examined. This leads to the conclusion that the link between theory and experiment is entirely inadequate and incapable of improvement by existing methods. A series of new methods is implemented in an attempt to short-circuit the chain of hypothesis and experiment which has hampered the identification of dubious steps. Methods of introducing uniform turbulence at relatively slow flows and improvements in light sources allow analysis of the approach flow by photographing particles illuminated by an interrupted Tyndall beam. Three new optical deflexion methods are used to give a measure of the randomness of flame-front orientation, of the time-mean structure of the flame and of the instantaneous shape of the corrugated front. It is found that this corrugated surface propagates at a velocity considerably in excess of the normal laminar burning velocity. Quantitative analysis of the frequency of ‘peaks’ and ‘valleys’ on the surface, together with comparative data from the apex of laminar flames, suggests an explanation in terms of the effects of curvature and, secondarily, of the influence of small-scale turbulence.

The generation of sound by flames

1979 ◽  
Vol 367 (1730) ◽  
pp. 291-309 ◽  
Keyword(s):  
Physical Process ◽  
Burning Velocity ◽  
Turbulent Flames ◽  
Experimental Results ◽  
Laminar Flames ◽  
Gas Mixture ◽  
Laminar Burning Velocity ◽  
Combustible Gas ◽  
Combustible Gas Mixture ◽  
Good Agreement

The conditions under which laminar flames in tubes can generate sound are investigated. It is shown that gaseous oscillations in a tube are amplified by the presence of a flame, and that the amplification arises through the dependence of the laminar burning velocity on the density and temperature of the combustible gas mixture into which the flame propagates. The theory is compared with observations made by Markstein and good agreement is achieved without the use of adjustable parameters. Some of the observed features of the noise of turbulent flames are interpreted on the basis of the same physical process as occur in tube-flames. In this case amplification is possible in the quadrupole or higher w-pole modes because of the well established property that such modes radiate very little energy if the dimensions of the source, in this case the flame, are small compared to the wavelength of the sound. Comparisons are made with the experimental results of Smith & Kilham (1963).

scholarly journals Autoignitions and detonations in engines and ducts

2012 ◽  
Vol 370 (1960) ◽  
pp. 689-714 ◽  
Author(s):  
Derek Bradley
Keyword(s):  
Hot Spots ◽  
Hot Spot ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Laminar Flames ◽  
Transverse Waves ◽  
One Dimensional ◽  
Gasoline Engines ◽  
Turbulent Burning Velocity ◽  
Autoignition Engines

The origins of autoignition at hot spots are analysed and the pressure pulses that arise from them are related to knock in gasoline engines and to developing detonations in ducts. In controlled autoignition engines, autoignition is benign with little knock. There are several modes of autoignition and the existence of an operational peninsula, within which detonations can develop at a hot spot, helps to explain the performance of various engines. Earlier studies by Urtiew and Oppenheim of the development of autoignitions and detonations ahead of a deflagration in ducts are interpreted further, using a simple one-dimensional theory of the generation of shock waves ahead of a turbulent flame. The theory is able to indicate entry into the domain of autoignition in an ‘explosion in the explosion’. Importantly, it shows the influence of the turbulent burning velocity, and particularly its maximum attainable value, upon autoignition. This value is governed by localized flame extinctions for both turbulent and laminar flames. The theory cannot show any details of the transition to a detonation, but regimes of eventually stable or unstable detonations can be identified on the operational peninsula. Both regimes exhibit transverse waves, triple points and a cellular structure. In the case of unstable detonations, transverse waves are essential to the continuing propagation. For hazard assessment, more needs to be known about the survival, or otherwise, of detonations that emerge from a duct into the same mixture at atmospheric pressure.

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