A Premixed Laminar Flame Interacting with a Vortex Resulting in Flame Stretch and Quenching
Title | A Premixed Laminar Flame Interacting with a Vortex Resulting in Flame Stretch and Quenching PDF eBook |
Author | William Lafayette Roberts IV. |
Publisher | |
Pages | 382 |
Release | 1992 |
Genre | |
ISBN |
Stretch-Induced Quenching in Flame-Vortex Interactions
Title | Stretch-Induced Quenching in Flame-Vortex Interactions PDF eBook |
Author | National Aeronautics and Space Adm Nasa |
Publisher | Independently Published |
Pages | 30 |
Release | 2019-01-04 |
Genre | Science |
ISBN | 9781792848421 |
The flame-vortex interaction problem is a natural configuration in which several issues relevant to turbulent combustion can be addressed: effect of strain-rate and curvature, effect of the Lewis number, effect of heat losses, effect of complex chemistry, and flame-generated turbulence. In such an approach, the interaction of an isolated vortex with a laminar premixed flame is viewed as a unit process of a turbulent premixed flame in which the reaction zone keeps a laminar like structure locally; this is precisely the case of the wrinkled flame or flamelet regime in turbulent combustion. The present work complements previous studies and involves the study of the interaction of a vortex pair and a laminar premixed flame in a planar two-dimensional geometry, together with numerical simulations. This geometry is quite unique since most studies have considered axisymmetric vortex rings. Such a geometry offers several advantages over previous studies. Samaniego, J.-M. ...
Experimental Quantification of Transient Stretch Effects from Vortices Interacting with Premixed Flames
Title | Experimental Quantification of Transient Stretch Effects from Vortices Interacting with Premixed Flames PDF eBook |
Author | |
Publisher | |
Pages | |
Release | 2004 |
Genre | |
ISBN |
The understanding of complex premixed combustion reactions is paramount to the development of new concepts and devices used to increase the overall usefulness and capabilities of current technology. The evolution from laminar spherically propagating flames to turbulent chemistry is a logical and necessary process to study the complex interactions which occur within any modern practical combustion device. Methane-air flames were chosen to observe the mild affects of thermo-diffusive stability. Five primary propane equivalence ratios were utilized for investigation: 0.69, 0.87, 1.08, 1.32, and 1.49. The choice of equivalence ratio was strategically made so that the 0.69/1.49 and 0.87/1.32 mixtures have the same undiluted flame propagation rate, dr/dt. Therefore, in the undiluted case, there are two flame speeds represented by these mixtures. Three vortices were selected to be used in this investigation. The vortex rotational velocities were measured to be 77 cm/s, 266 cm/s and 398 cm/s for the “weakâ€, “medium†and “strong†vortices, respectively. Ignition of the flame occurred in two ways: (1) spark-ignition or (2) laser ignition using an Nd:YAG laser at its second harmonic in order to quantify the effect of electrode interference. Accompanying high-speed chemiluminescence imaging measurements, instantaneous pressure measurements were obtained to give a more detailed understanding of the effect of vortex strength on reactant consumption rate over an extended time scale and to explore the use of a simple measurement to describe turbulent mixing. Further local flame-vortex interface analysis was conducted using non-invasive laser diagnostics, such as particle image velocimetry and planer laser induced fluorescence of the OH radical. The dependence of heat release rate on temperature provides an estimation of the strain rate dependence of the reaction rate.
Turbulent Combustion
Title | Turbulent Combustion PDF eBook |
Author | Norbert Peters |
Publisher | Cambridge University Press |
Pages | 322 |
Release | 2000-08-15 |
Genre | Science |
ISBN | 1139428063 |
The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.
Scientific and Technical Aerospace Reports
Title | Scientific and Technical Aerospace Reports PDF eBook |
Author | |
Publisher | |
Pages | 692 |
Release | 1995 |
Genre | Aeronautics |
ISBN |
An Experimental Investigation of the Interaction Between a Kármán Vortex Street and a Premixed Laminar Flame
Title | An Experimental Investigation of the Interaction Between a Kármán Vortex Street and a Premixed Laminar Flame PDF eBook |
Author | Izak Namer |
Publisher | |
Pages | 113 |
Release | 1980 |
Genre | Dissertations, Academic |
ISBN |
The interaction of a premixed C2H4-air flame with a Karman vortex street was studied. Laser Doppler anemometry was used for velocity measurements and Rayleigh scattering was used to measure total gas density. A reference hotwire was used to enable phase-locked ensemble averaging to be performed on the data. The velocity measurements, for vortex shedding cylinder Reynolds numbers 73 and 110, indicated that the vortex street and, hence, the flow field upstream of the flame is deflected by the flame. This is due to the pressure drop across the flame which is necessary to accelerate the flow behind the flame. The vortices were not observed behind the flame. The combination of dilatation and increased dissipation 'consumed' the vortices. Density statistics obtained from Rayleigh scattering measurements were compared with predictions by the Bray-Moss-Libby (B-M-L) model which neglects intermediate states. Density fluctuations were overpredicted by the B-M-L model by a small amount for 73 and 110. The flame was essentially a wrinkled-laminar flame for these conditions. However, for (UD/v) = 500 the flame consisted of a distributed reaction zone and intermediate states accounted for as much as 80% of all states encountered in portions of the flame. The B-M-L model significantly overpredicted density fluctuation statistics for this condition. A qualitative comparison was made with numerical calculations by Karasalo and Namer for the time dependent interaction of a flame with an ideal Karman vortex street and suggestions for improving the model were made.
Measurements of Flame-vortex Interaction Dynamics and Chemistry
Title | Measurements of Flame-vortex Interaction Dynamics and Chemistry PDF eBook |
Author | Charles Jeffrey Mueller |
Publisher | |
Pages | 334 |
Release | 1996 |
Genre | |
ISBN |