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1
Sugawa, Osami. "Flame Behavior." Japanese journal of science and technology for identification 4, no. 2 (2000): 43–52. http://dx.doi.org/10.3408/jasti.4.43.
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Al-Mosawi, Ali I., Mustafa Ahmed Rijab, Ali J. Salaman, Naser A. Alwash, and Naglaa S. Aziz. "Flammability Behavior of Composite Mixed with Retardant Agents." Applied Mechanics and Materials 186 (June 2012): 129–31. http://dx.doi.org/10.4028/www.scientific.net/amm.186.129.
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The flammability characteristics and synergistic effect of zinc borate with antimony trioxide in araldite resin composite have been studied by thermal erosion test . Zinc borate was added first to araldite resin reinforced by hybrid carbon-Kevlar fibers as a surface layer(5mm) thickness .Then, the result composite material was exposed to a direct flame generated from Oxyacetylene torch (3000°C) with different flame exposure intervals (10,20mm), and study the range of resistance of retardant material layer to the flames and protected the substrate .After that , antimony trioxide was added to zinc borate with various amount(10%,20%,30%) to forming a hybrid flame retardant for enhance the action of this material to react flame . Hybrid retardant exposure to same flame temperature and exposure distances. Method of measuring the surface temperature opposite to the flame was used to determined the heat transferred to composite material . the best results was obtained with large exposed distance and large percentage from protective layer which is zinc borate with (30%) antimony trioxide .
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Jiang, Xiaozhen, Jingxuan Li, and Lijun Yang. "Nonlinear response of laminar premixed flames to dual-input harmonic disturbances." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 4 (February 1, 2023): 3408–19. http://dx.doi.org/10.3397/in_2022_0484.
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In gas turbines, aero-engines and rocket engines, flames are always disturbed by perturbations of dual or multiple harmonic frequencies, resulting in corresponding combustion instability. This paper analyses the nonlinear response of laminar premixed flames to dual-input harmonic disturbances to further understand those associated combustion instability. Nonlinear results of flame dynamics were derived from analytical and numerical solutions of the G-equation. The spatial front-tracking of premixed flames was obtained, where types of nonlinear behaviors were classified and related mechanisms of that were elucidated. A dual-input flame description function (DIFDF) was proposed to separately determine global nonlinearities of flame responses of fundamental and higher harmonics frequencies under dual-input disturbances. The fundamental frequency response consists of linear and nonlinear components, and the higher harmonic frequency one is purely nonlinear. The DIFDF properties of conical and "V" flames were compared, with particular emphasis on their differences in nonlinear behavior. The spatial and global effects of the second input frequency on the flame kinematics perturbed by the first frequency were also clarified. Furthermore, the roles of perturbation amplitude and flame height in spatial flame dynamics and DIFDF were quantified.
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Baker, John, Mark E. Calvert, and David W. Murphy. "Structure and Dynamics of Laminar Jet Micro-Slot Diffusion Flames." Journal of Heat Transfer 124, no. 4 (July 16, 2002): 783–90. http://dx.doi.org/10.1115/1.1482083.
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Results of an experimental investigation into the behavior of laminar jet diffusion flames, produced using micro-slot burner ports, are presented. Under certain conditions, the cross-sectional shape of micro-slot flames is qualitatively similar to the cross-sectional shape of circular burner port flames produced in an environment where molecular diffusion is the primary transport mechanism. An order of magnitude analysis reveals that, over the range of experimental conditions examined, the behavior of the experimentally observed micro-slot flames is not necessarily diffusion-controlled. A comparison of the experimental data with an accepted theoretical model shows that current theoretical models do not accurately predict the experimentally observed flame heights. A theoretical expression for purely diffusion-controlled micro-slot flame height is developed and compared with experimental micro-slot flame data. The region where this theoretical expression is valid is identified through an examination of the diffusion to buoyancy parameter. A qualitative discussion of micro-slot flame structure is also presented.
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Gupta, A. K., M. J. Lewis, and M. Daurer. "Swirl Effects on Combustion Characteristics of Premixed Flames." Journal of Engineering for Gas Turbines and Power 123, no. 3 (November 15, 2000): 619–26. http://dx.doi.org/10.1115/1.1339987.
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The effect of radial distribution of swirl has been examined on the thermal behavior of two different premixed flames using a double concentric premixed swirl burner. The double concentric swirl burner allowed systematic variation in the radial distribution of swirl (both co- and counter-) between the inner and outer annulus of the burner. The burner had two annular jets and a central nozzle. Information on the thermal field in two flames formed by co- or counter-swirl in the outer annulus and co-swirl in the inner annulus has been examined. Specifically mean and fluctuating temperatures, integral and micro thermal time scales, and probability density distribution of temperatures have been determined at various spatial positions in the flames. The micro-thermocouple output was compensated to provide high-frequency (about 1 kHz) response of the thermocouple. Direct flame photographs were taken to provide information about the global features of flames and flame stability. The global and thermal characteristic data presented here provided a complete insight on the thermal behavior of co- and counter-swirl flames. The results show that the direction of swirl (co- or counter-) used to stabilize a flame from annular jets provides a great influence on flame symmetry. The simultaneous combination of co- and counter-swirl in the burner showed a very nonsymmetrical behavior of the flame. The global and thermal data presented here confirmed these findings. The results suggest significant effect of co- and counter-swirl distribution in flames on the NOx emission levels.
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Gupta, A. K., S. Bolz, and T. Hasegawa. "Effect of Air Preheat Temperature and Oxygen Concentration on Flame Structure and Emission." Journal of Energy Resources Technology 121, no. 3 (September 1, 1999): 209–16. http://dx.doi.org/10.1115/1.2795984.
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The structure of turbulent diffusion flames with highly preheated combustion air (air preheat temperature in excess of 1150°C) has been obtained using a specially designed regenerative combustion furnace. Propane gas was used as the fuel. Data have been obtained on the global flame features, spectral emission characteristics, spatial distribution of OH, CH, and C2 species, and pollutant emission from the flames. The results have been obtained for various degrees of air preheat temperatures and O2 concentration in the air. The color of the flame was found to change from yellow to blue to bluish-green to green over the range of conditions examined. In some cases a hybrid color flame was also observed. The recorded images of the flame photographs were analyzed using color-analyzing software. The results show that thermal and chemical flame behavior strongly depends on the air preheat temperature and oxygen content in the air. The flame color was observed to be bluish-green or green at very high air preheat temperatures and low-oxygen concentration. However, at high-oxygen concentration, the flame color was yellow. The flame volume was found to increase with increase in air-preheat temperature and decrease in oxygen concentration. The flame length showed a similar behavior. The concentrations of OH, CH, and C2 increased with an increase in air preheat temperatures. These species exhibited a two-stage combustion behavior at low-oxygen concentration and single-stage combustion behavior at high-oxygen concentration in the air. Stable flames were obtained for remarkably low equivalence ratios, which would not be possible with normal combustion air. Pollutant emission, including CO2 and NOx, was much lower with highly preheated combustion air at low O2 concentration than with normal air. The results also suggest uniform flow and flame thermal characteristics with conditioned, highly preheated air. Highly preheated air combustion provides much higher heat flux than normal air, which suggests direct energy savings and a reduction of CO2 to the environment. Colorless oxidation of fuel has been observed under certain conditions.
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Martin, Jan, Michael Börner, Justin Hardi, Dmitry Suslov, and Michael Oschwald. "Experimental Investigation of Flame Anchoring Behavior in a LOX/LNG Rocket Combustor." Aerospace 10, no. 6 (June 6, 2023): 542. http://dx.doi.org/10.3390/aerospace10060542.
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Hot fire tests of a multi-injector research combustor were performed with liquid-oxygen and liquefied-natural-gas (LOX/LNG) propellants at chamber pressures from 30 up to 67 bar, hence at conditions similar to an upper stage rocket engine. Within these tests shear coaxial injectors were tested with and without a recessed LOX post. In both configurations, operating conditions with flames anchored at the LOX post tip and thus, if available, pre-combustion in the recess volume as well as lifted flames were observed. Flame anchoring was indirectly detected via acoustic measurements, using mean speed of sound to indicate the presence of flame in the head end of the combustion chamber. While the injector without recess showed only stable combustion irrespective of the flame anchoring behavior, the recessed injector featured short-lived bursts of oscillatory combustion and sustained combustion instabilities. Analysis of the test data showed that stable flame anchoring could not be ensured at momentum flux ratios below 20 for a non-recessed and below 45 for a recessed injector.
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Bohn, D., G. Deutsch, and U. Kru¨ger. "Numerical Predication of the Dynamic Behavior of Turbulent Diffusion Flames." Journal of Engineering for Gas Turbines and Power 120, no. 4 (October 1, 1998): 713–20. http://dx.doi.org/10.1115/1.2818458.
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Environmental compatibility requires low-emission burners for gas turbine power plants as well as for jet engines. In the Past, significant progress has been made developing low NOx and CO burners. Unfortunately, these burners often have a more pronounced tendency than conventional burner designs to produce combustion driven oscillations. The oscillations may be excited to such an extent that pronounced pulsation may possibly occur; this is associated with a risk of engine failure. The stability of a burner system can be investigated by means of a stability analysis under the assumption of acoustical behavior. The problem with all these algorithms is the transfer function of the flame. A new method is presented here to predict the dynamic flame behavior by means of a full Navier-Stokes simulation of the complex combustion process. The first step is to get a steady-state solution of a flame configuration. After that a transient simulation follows with a sudden change in the mass flow rate at the flame inlet. The time-dependent answer of the flame to this disturbance is then transformed into the frequency space by a Laplace Transformation. This leads, in turn, to the frequency response representing the dynamic behavior of the flame. In principle, this method can be adapted for both diffusion as well as premixed flame systems. However, due to the fact that diffusion flames are more controlled by the mixing process than by the chemical kinetic, the method has first been used for the prediction of the dynamic behavior of turbulent diffusion flames. The combustion has been modelled by a mixed-is-burnt model. The influence of the turbulence has been taken into account by a modified k-ε model and the turbulence influences the combustion rate by presumed probability density functions (pdf). The steady state as well as the transient results have been compared with experimental data for two different diffusion flame configurations. Although the burner configuration is relatively complex, the steady-state results collaborate very well with the experiments for velocity, temperature, and species distribution. The most important result is that the heat release that drives the oscillations can be modeled sufficiently accurately. The effect of using different pdf models has been discussed and the best model has been used for the transient calculations of the dynamic flame behavior. The results for the frequency response of the flame are very encouraging. The principal behavior of the flame—higher order time element with a delay time—can be predicted with sufficient precision. In addition, the qualitative results collaborate fairly well with the experiments.
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Yakush, Sergey, Oleg Semenov, and Maxim Alexeev. "Premixed Propane–Air Flame Propagation in a Narrow Channel with Obstacles." Energies 16, no. 3 (February 3, 2023): 1516. http://dx.doi.org/10.3390/en16031516.
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Flame interaction with obstacles can affect significantly its behavior due to flame front wrinkling, changes in the flame front surface area, and momentum and heat losses. Experimental and theoretical studies in this area are primarily connected with flame acceleration and deflagration to detonation transition. This work is devoted to studying laminar flames propagating in narrow gaps between closely spaced parallel plates (Hele–Shaw cell) in the presence of internal obstacles separating the rectangular channel in two parts (closed and open to the atmosphere) connected by a small hole. The focus of the research is on the penetration of flames through the hole to the adjacent channel part. Experiments are performed for fuel-rich propane–air mixtures; combustion is initiated by spark ignition near the far end of the closed volume. Additionally, numerical simulations are carried out to demonstrate the details of flame behavior prior to and after penetration into the adjacent space. The results obtained may be applicable to various microcombustors; they are also relevant to fire and explosion safety where flame propagation through leakages may promote fast fire spread.
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Lipatnikov, Andrei, Shinnosuke Nishiki, and Tatsuya Hasegawa. "Closure Relations for Fluxes of Flame Surface Density and Scalar Dissipation Rate in Turbulent Premixed Flames." Fluids 4, no. 1 (March 7, 2019): 43. http://dx.doi.org/10.3390/fluids4010043.
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In this study, closure relations for total and turbulent convection fluxes of flame surface density and scalar dissipation rate were developed (i) by placing the focus of consideration on the flow velocity conditioned to the instantaneous flame within the mean flame brush and (ii) by considering the limiting behavior of this velocity at the leading and trailing edges of the flame brush. The model was tested against direct numerical simulation (DNS) data obtained from three statistically stationary, one-dimensional, planar, premixed turbulent flames associated with the flamelet regime of turbulent burning. While turbulent fluxes of flame surface density and scalar dissipation rate, obtained in the DNSs, showed the countergradient behavior, the model predicted the total fluxes reasonably well without using any tuning parameter. The model predictions were also compared with results computed using an alternative closure relation for the flame-conditioned velocity.
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Fletcher, Thomas H., Denver Haycock, Seth Tollefsen, and David O. Lignell. "Merging of Horizontally and Vertically Separated Small-Scale Buoyant Flames." Fire 4, no. 3 (August 25, 2021): 51. http://dx.doi.org/10.3390/fire4030051.
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The purpose of this study was to investigate the merging behavior of small-scale buoyant flames that might be representative of flames from a leaf in a shrub. Zirconia felt pads soaked in n-heptane were suspended on thin rods and spaced both horizontally and vertically. Time-dependent video images from flames from two-pad and three-pad configurations were analyzed to determine merging probability, combined flame characteristics (height, area, and width), and changes in burn time. Correlations of these combined flame characteristics were developed based on horizontal and vertical spacing between the pads. Merging probability correlated with an exponential function that was quadratic in horizontal and/or vertical spacing. Flame heights corrected for vertical inter-pad spacing showed a maximum increase of 50% over single flame heights, and were correlated with an exponential decay function. Flame areas increased by a maximum of 34%, but on average were relatively constant. Corrected flame widths for the merged flames increased by as much as 55% in some configurations, but decreased by up to 73% in other configurations. Burn times for upper pads decreased when there was no horizontal spacing. The limited flame growth observed in these non-overlapping configurations in the horizontal dimension imply that overlapping configurations seem to be necessary for significant flame growth.
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Anggono, Willyanto, Fandi Dwiputra Suprianto, Tubagus P. Wijaya, and Michael S. C. Tanoto. "Behavior of Flame Propagation in Biogas Spark Ignited Premix Combustion with Carbon Dioxide Inhibitor." Advanced Materials Research 1044-1045 (October 2014): 251–54. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.251.
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Biogas is a mixture of gases which commonly consists of methane (up to 50%) and other inhibitor gases which are dominated by carbon dioxide (up to 50%). Biogas is produced naturally by the decomposition of organic materials such as vegetation or animal manure in the absence of oxygen and it also contributes less greenhouse gases which may lead to global warming or climate change. The presence of carbon dioxide (CO2) in biogas is presumed to have some effects on biogas flame propagation characteristics. This study focuses on the effect of carbon dioxide (CO2) as the biggest inhibitor composition in biogas on flame propagation speed as the important flame propagation characteristic in spark ignited premix combustion. Propagating flames are employed to measure the flame propagation speed as a function of the mixture composition. This parameter was measured using a transparent tube fuel chamber with dimensions of 60 mm inner diameter and 300 mm height based on DIN 51649 standards and recorded by high speed digital photographic technique. The characteristic of biogas-oxygen flames were studied at stoichiometric, room temperature and atmospheric condition from 0% to 50% CO2 biogas inhibitor composition increased by 10% for each experiment. The results showed that the carbon dioxide decreases flame propagation speed of biogas. These indicated that carbon dioxide reduced reaction rate of biogas premixed combustion.
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Albayrak, Alp, and Wolfgang Polifke. "An analytical model based on the G-equation for the response of technically premixed flames to perturbations of equivalence ratio." International Journal of Spray and Combustion Dynamics 10, no. 2 (November 22, 2017): 103–10. http://dx.doi.org/10.1177/1756827717740776.
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A model for the response of technically premixed flames to equivalence ratio perturbations is proposed. The formulation, which is an extension of an analytical flame tracking model based on the linearized G-equation, considers the flame impulse response to a local, impulsive, infinitesimal perturbation that is transported by convection from the flame base towards the flame surface. It is shown that the contributions of laminar flame speed and heat of reaction to the impulse response exhibit a local behavior, i.e. the flame responds at the moment when and at the location where the equivalence ratio perturbation reaches the flame surface. The time lag of this process is related to a convective time scale, which corresponds to the convective transport of fuel from the base of the flame to the flame surface. On the contrary, the flame surface area contribution exhibits a non-local behavior: albeit fluctuations of the flame shape are generated locally due to a distortion of the kinematic balance between flame speed and the flow velocity, the resulting wrinkles in flame shape are then transported by convection towards the flame tip with the restorative time scale. The impact of radial non-uniformity in equivalence ratio perturbations on the flame impulse response is demonstrated by comparing the impulse responses for uniform and parabolic radial profiles. Considerable deviation in the phase of the flame transfer function, which is important for thermo-acoustic stability, is observed.
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Fan, Baochun, Zhanfeng Ying, Zhihua Chen, and Jingfang Ye. "Observations of flame behavior during flame-obstacle interaction." Process Safety Progress 27, no. 1 (2008): 66–71. http://dx.doi.org/10.1002/prs.10223.
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Nuñez Celis, Howard, Mauricio Rincón Ortiz, and Andrés González Hern´ández. "Corrosion Behavior of Flame Sprayed Cr2O3 Coatings on Carbon Steel in Chloride Solutions." Revista Ingenierías Universidad de Medellín 21, no. 40 (March 31, 2022): 143–62. http://dx.doi.org/10.22395/rium.v21n40a9.
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Cr2O3 coatings were deposited on carbon steel through the flame spraying technique using two types of flames (neutral and oxidizing). The protective and morphological characteristics of the coatings were determined. The coatings had layer thickness values of 114 and 214µm for oxidizing and neutral samples, respectively. Porosity percentages of 4.5 % and 2.5 % were determined, where the neutral sample presented the greatest porosity due to the insufficient fusion of the oxide particles during the process, resulting in the formation of a heterogeneous and less compact layer. Microcracks and pores were found on the surface and cross-section of the coatings, due to the thermal expansion generated during the solidification process. The coating protective capacity was evaluated by electrochemical techniques over 672 hours in a 3.5 %wt NaCl saline solution. The results evidenced that the coatings manufactured with the oxidizing flame presented more corrosion resistance compared to those prepared with the neutral flame. The corrosion products were more evident in the neutral flame coatings, because of the diffusion mechanisms from the substrate to the surface coating through the interconnected pores. Finally, the wettability of the sodium chloride solution in the Cr2O3 coatings was measured by the contact angle technique, finding that the oxidizing flame coatings exhibited a higher angle contact value (64.8°) in contrast to the neutral flame coatings (35°).
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Ayoobi, Mohsen, and Ingmar Schoegl. "Numerical analysis of flame instabilities in narrow channels: Laminar premixed methane/air combustion." International Journal of Spray and Combustion Dynamics 9, no. 3 (June 5, 2017): 155–71. http://dx.doi.org/10.1177/1756827717706009.
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Premixed flames propagating within small channels show complex combustion phenomena that differ from flame propagation at conventional scales. Available experimental and numerical studies have documented stationary, non-stationary, or asymmetric modes that depend on properties of the incoming reactant flow as well as channel geometry and wall temperatures. This work seeks to illuminate mechanisms leading to symmetry breaking and limit cycle behavior that are fundamental to these combustion modes. Specifically, four cases of lean premixed methane/air combustion—two equivalence ratios (0.53 and 0.7) and two channel widths (2 mm and 5 mm)—are investigated in a 2D configuration with constant channel length and bulk inlet velocity, where numerical simulations are performed using detailed chemistry. External wall heating is simulated by imposing a linear temperature gradient as a boundary condition on both walls. In the 2 mm channel, both equivalence ratios produce flames that stabilize with symmetric flame fronts after propagating upstream. In the 5 mm channel, flame fronts start symmetrically, although symmetry is broken almost immediately after ignition. Further, 5 mm channels produce non-stationary combustion modes with dramatically different limit cycles: in the leaner case ( φ = 0.53), the asymmetric flame front flops periodically, whereas in the richer case ( φ = 0.7), flames with repetitive extinctions and ignitions (FREI) are observed. To further understand the flame dynamics, reaction fronts and flame fronts are captured and differentiated. Results show that the loss of flame front symmetry originates in a region close to the flame cusp, where flow and chemical characteristics exhibit large gradients and curvatures. Limit cycle behavior is illuminated by investigating flame edges that are formed along the wall, and accompany local or global ignition and extinction processes. In the flopping mode ( φ = 0.53), local ignition and extinction in regions adjacent to the wall result in oblique fronts that advance and recede along the wall and redirect the flow ahead of the flame. In the FREI mode, asymmetric flames propagate much farther upstream, where they experience global extinction due to heat losses, and re-ignite far downstream with opposite flame front orientation. In both cases, an interaction of flow and chemical effects drives the asymmetric limit cycles. The lack of instabilities and asymmetries for the 2mm cases is attributed to insufficient wall separation, which is of the same order of magnitude as the flame thickness.
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Parsinejad, Farzan, Matyas Matlo, and Mohamad Metghalchi. "A Mathematical Model for Schlieren and Shadowgraph Images of Transient Expanding Spherical Thin Flames." Journal of Engineering for Gas Turbines and Power 126, no. 2 (April 1, 2004): 241–47. http://dx.doi.org/10.1115/1.1688368.
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Optical behavior of spherical flames is investigated using both Schlieren and shadowgraph methods. A mathematical model has been developed to predict the intensity of refracted light beams interacting with a transient expanding thin flame. Experimental facilities have been built to visualize transient expanding spherical flames. The facilities include a cylindrical chamber with two end glasses for optical observation. Shadowgraph and Schlieren pictures of flame propagation have been taken using a high-speed charged coupled device camera. Experimental results are in very good agreement with those predicted by the theoretical model. Schlieren and shadowgraph techniques have also been used to view smooth, cracked and cellular flames; these techniques will be useful in future in studies to determine the stability of propagating flame.
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Moore, N. J., J. L. McCraw, and K. M. Lyons. "Observations on Jet-Flame Blowout." International Journal of Reacting Systems 2008 (2008): 1–7. http://dx.doi.org/10.1155/2008/461059.
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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.
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Wang, Yalong, Chaoying Li, Haidong Liu, Jin Lin, Shouxiang Lu, and Kim Meow Liew. "On The Flame Behavior during Cable Insulation Material Ignited by Fault Arc: A Flame Extracting and Noise Reduction Algorithm." Fire 6, no. 2 (January 24, 2023): 45. http://dx.doi.org/10.3390/fire6020045.
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The electric fault arc, particularly the series arc, leads to plenty of electrical fire. The limitations of t previous studies include: (1) most existing research focused on gaseous atmospheres rather than solids materials, which is contrary to the actual demand; and (2) the studied external heat sources were restricted to cone heaters and flames, while the electric arc was seldom studied. To overcome these limitations, we developed an experimental platform to investigate the flame behavior when cable insulation material was ignited by the fault arc. We proposed a flame-extracting and noise-reduction algorithm to process the enormous number of photos shot by the high-speed camera. The main obtained findings were: (1) the appropriate size of the structuring element plays an essential role in filtering the flame region in the photos, too small a size resulted in the wrong recognition of incandescent particles, while too large a size made a jagged distortion; (2) the mean flame area increased as the system load grew; (3) The flame size became more prominent, and the flame appeared more frequently in specific locations when the system load increased. The in-depth understanding of flame behavior provided by this work will help to optimize the design of electric systems and disaster prevention reduction.
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Chien, Yu-Chien, and Derek Dunn-Rankin. "Combustion Characteristics of Methane Hydrate Flames." Energies 12, no. 10 (May 21, 2019): 1939. http://dx.doi.org/10.3390/en12101939.
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This research studies the structure of flames that use laboratory-produced methane hydrates as fuel, specifically for the purpose of identifying their key combustion characteristics. Combustion of a methane hydrate involves multiple phase changes, as large quantities of solid clathrate transform into fuel gas, water vapor, and liquid water during burning. With its unique and stable fuel energy storage capability, studies in combustion are focused on the potential usage of hydrates as an alternative fuel source or on their fire safety. Considering methane hydrate as a conventional combustion energy resource and studying hydrate combustion using canonical experimental configurations or methodology are challenges. This paper presents methane hydrate flame geometries from the time they can be ignited through their extinguishment. Ignition and burning behavior depend on the hydrate initial temperature and whether the clathrates are chunks or monolithic shapes. These behaviors are the subject of this research. Physical properties that affect methane hydrate in burning can include packing density, clathrate fraction, and surface area. Each of these modifies the time or the temperature needed to ignite the hydrate flames as well as their subsequent burning rate, thus every effort is made to keep consistent samples. Visualization methods used in combustion help identify flame characteristics, including pure flame images that give reaction zone size and shape and hydrate flame spectra to identify important species. The results help describe links between hydrate fuel characteristics and their resulting flames.
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Wang, Yawei, Weipeng Fan, Gao Ye, Wan-Ki Chow, Hung-Kit Lai, Cheuk-Lun Chow, and Chi-Honn Cheng. "Wind action on whirling flame characteristics." Thermal Science, no. 00 (2022): 132. http://dx.doi.org/10.2298/tsci220509132w.
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The behavior of whirling flame above a pool fire under cross wind was studied using a small wind tunnel. Whirling flames with different heat release rates were generated by an experimental rig. Effect of different wind speeds on the whirling flame was studied by an oil pool of two different diameters. Lateral images of the whirling flame collected were analyzed. Results show that under cross flow, the whirling flame was deflected along the direction of incoming flow. With the increase in wind speed, the deflection angle increased gradually. The angle also increased with the increase in pool diameter. When the cross flow increased to a certain value, the flame stopped swirling, and changed to an irregular shape. The maximum cross wind speed of the flame that did not stop flame rotation decreased with diameter. Crosswind with lower speed would raise the temperature of the whirling flame. When the wind speed was higher than a critical value, the temperature was reduced because burning rate decreased.
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Wirawan, I. K. G., I. N. G. Wardana, Rudy Soenoko, and Slamet Wahyudi. "Premixed Combustion of Coconut Oil on Perforated Burner." International Journal of Renewable Energy Development 2, no. 3 (October 30, 2013): 133–39. http://dx.doi.org/10.14710/ijred.2.3.133-139.
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Coconut oil premixed combustion behavior has been studied experimentally on perforated burner with equivalence ratio (φ) varied from very lean until very rich. The results showed that burning of glycerol needs large number of air so that the laminar burning velocity (SL) is the highest at very lean mixture and the flame is in the form of individual Bunsen flame on each of the perforated plate hole. As φ is increased the SL decreases and the secondary Bunsen flame with open tip occurs from φ =0.54 at the downstream of perforated flame. The perforated flame disappears at φ = 0.66 while the secondary Bunsen flame still exist with SL increases following that of hexadecane flame trend and then extinct when the equivalence ratio reaches one or more. Surrounding ambient air intervention makes SL decreases, shifts lower flammability limit into richer mixture, and performs triple and cellular flames. The glycerol diffusion flame radiation burned fatty acids that perform cellular islands on perforated hole. Without glycerol, laminar flame velocity becomes higher and more stable as perforated flame at higher φ. At rich mixture the Bunsen flame becomes unstable and performs petal cellular around the cone flame front. Keywords: cellular flame; glycerol; perforated flame;secondary Bunsen flame with open tip; triple flame
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Yilmaz, N., A. B. Donaldson, W. Gill, and R. E. Lucero. "Imaging of flame behavior in flickering methane/air diffusion flames." Journal of Visualization 12, no. 1 (March 2009): 47–55. http://dx.doi.org/10.1007/bf03181942.
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Gupta, A. K. "Thermal Characteristics of Gaseous Fuel Flames Using High Temperature Air." Journal of Engineering for Gas Turbines and Power 126, no. 1 (January 1, 2004): 9–19. http://dx.doi.org/10.1115/1.1610009.
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Recent advances on high temperature air combustion (HiTAC) have demonstrated significant energy savings, higher and uniform thermal field, lower pollution, and smaller size of the equipment for a range of furnace applications. The HiTAC technology has evolved from the conception of excess enthalpy combustion (EEC) to high and ultra-high preheated air combustion. In the HiTAC method, combined heat regeneration and low oxygen methods are utilized to enlarge and control the flame thermal behavior. This technology has shown promise for much wider applications in various process and power industries, energy conversion, and waste to clean fuel conversion. For each application the flow, thermal, and chemical behavior of HiTAC flames must be carefully tailored to satisfy the specific needs. Qualitative and quantitative results are presented on several gas-air diffusion flames using high-temperature combustion air. A specially designed regenerative combustion test furnace facility, built by Nippon Furnace Kogyo, Japan, was used to preheat the combustion air to elevated temperatures. The flames with highly preheated combustion air were significantly more stable and homogeneous (both temporally and spatially) as compared to the flames with room-temperature combustion air. The global flame features showed the flame color to change from yellow to blue to bluish-green to green over the range of conditions examined. In some cases hybrid and purple color flame was also observed. Under certain conditions flameless or colorless oxidation of the fuel has also been demonstrated. Information on global flame features, flame spectral emission characteristics, spatial distribution of OH, CH, and C2 species and emission of pollutants has been obtained. Low levels of NOx along with negligible levels of CO and HC have been obtained using high-temperature combustion air. The thermal and chemical behavior of high-temperature air combustion flames depends on fuel property, preheat temperature, and oxygen concentration of air. Waste heat from a furnace in high-temperature air combustion technology is retrieved and introduced back into the furnace using regenerator. These features help save energy, which subsequently also reduce the emission of CO2 (greenhouse gas) to the environment. Flames with high temperature air provide significantly higher and uniform heat flux than normal air, which reduces the equipment size or increases the process material throughput for same size of the equipment. The high-temperature air combustion technology can provide significant energy savings (up to about 60%), downsizing of the equipment (about 30%), and pollution reduction (about 25%). Fuel energy savings directly translates to a reduction of CO2 and other greenhouse gases to the environment.
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Sasongko, Mega Nur. "The Effect of Water Droplet Size on the Extinguished Concentric Jet Premixed and Diffusion Flame." Applied Mechanics and Materials 493 (January 2014): 173–78. http://dx.doi.org/10.4028/www.scientific.net/amm.493.173.
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The present research experimentally investigated the effect of different water droplet size on the burning behavior and extinction condition of concentric jet premixed and diffusion flame. Water droplet stream in line with flowing air from lower duct. The burning behavior of concentric jet flame was observed and the extinction of flame was gained by decreasing the flow rate of fuel until the flame exthinguised. The results showed that the burning behavior of concentric jet diffusion and premixed flame had the same tendency. Different water droplet size influenced the burning behavior of flame. Decreasing the water droplet size, luminosity of the flame became thin as well as reducing the flame height. However, the inhibition effect of water droplet was stronger for diffusion flame compared to premixed flame. For smaller water droplet size, water droplet was four times more effective for suppressing the diffusion flame than premixed flame
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Chen, Xian Feng, Y. Zhang, M. Chen, Shao Feng Ren, and Xiao L. Song. "Experiment on Thin Structure Behavior of Explosion Flame Flow Field." Applied Mechanics and Materials 44-47 (December 2010): 2793–97. http://dx.doi.org/10.4028/www.scientific.net/amm.44-47.2793.
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To prevent and control fire and explosion disasters, the premixed methane-air explosion was performed under restricted condition. In the experiment, the high speed schlieren photography system was used to record the flame characteristics and propagation mechanism. At the same time the ion current probe was used to reveal the inner flame structure characteristics. Based on the images of High Speed Schlieren Photography, the flame acceleration and flame structure were discussed in detail. In addition, the flow field characteristic of explosion flame was disclosed clearly. The microscopic evolving process of laminar-turbulent transition was accomplished in the period of flame structure change. As an alternative observation and detect technique, the high speed schlieren photograph system was used to capture flame front microstructure dynamic process precisely. Based on burning chemical and explosive dynamics, the optical measure method can record flame dynamic behavior visually, which further helps to disclose flame microstructure characteristic and the inner dynamic mechanism.
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Yuliati, Lilis. "Flame stability and behavior inside meso-scale combustor with different flame holder." MATEC Web of Conferences 159 (2018): 02011. http://dx.doi.org/10.1051/matecconf/201815902011.
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Flame stability and behavior inside meso-scale combustor with different flame holder was investigated experimentally. Three types of flame holder i.e. wire mesh, flat plate with circular holes and flat plate with narrow slits, were used to improve the flame stability inside the meso-scale combustor. Combustor with flat plate - narrow slits flame holder has the best flame stability, i.e. stable flame established inside the combustor at the highest reactant velocity compared to the other combustor with the different flame holder. Furthermore, combustor with wire mesh and flat plate with narrow slits have a relatively uniform flame colour at the combustor cross section, compared to flame visualization inside meso-scale combustor with flame holder of flat plate with circular holes. This phenomena is related to non-uniform reactant distribution on the combustor cross section.
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Renner, Juliana Sally, Rhoda Afriyie Mensah, Lin Jiang, Qiang Xu, Oisik Das, and Filippo Berto. "Fire Behavior of Wood-Based Composite Materials." Polymers 13, no. 24 (December 13, 2021): 4352. http://dx.doi.org/10.3390/polym13244352.
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Wood-based composites such as wood plastic composites (WPC) are emerging as a sustainable and excellent performance materials consisting of wood reinforced with polymer matrix with a variety of applications in construction industries. In this context, wood-based composite materials used in construction industries have witnessed a vigorous growth, leading to a great production activity. However, the main setbacks are their high flammability during fires. To address this issue, flame retardants are utilized to improve the performance of fire properties as well as the flame retardancy of WPC material. In this review, flame retardants employed during manufacturing process with their mechanical properties designed to achieve an enhanced flame retardancy were examined. The addition of flame retardants and manufacturing techniques applied were found to be an optimum condition to improve fire resistance and mechanical properties. The review focuses on the manufacturing techniques, applications, mechanical properties and flammability studies of wood fiber/flour polymer/plastics composites materials. Various flame retardant of WPCs and summary of future prospects were also highlighted.
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Liu, Qiong, Bing Du, Qiang Yan, Long Shi, Ming Li, and Zhi Li. "Study on Coupled Combustion Behavior of Two Parallel Line Fires." Fire 5, no. 1 (January 22, 2022): 14. http://dx.doi.org/10.3390/fire5010014.
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In this study, the interaction of two parallel line fires with a length-width ratio of greater than 50 was investigated and compared to a single line fire. Considering different length–width ratios and spacings between the fire sources, experiments were carried out to analyze the fire characteristics, such as the burning rate, the flame-merging state, the flame height, the flame tilt angle, and the flame length of the line fires. Its regularity was revealed by combining two mechanisms, namely, heat feedback enhancement and air entrainment restriction. The results revealed that the burning rate under different length–width ratios shows a uniform law, which increases first and then decreases with a greater spacing between the fire sources. There is a special relationship between the flame-merging probability Pm and the dimensionless characteristic parameters (S/ZC)/(L/d)0.27. Based on this relationship, a critical criterion of flame merging can be obtained as (S/ZC)/(L/d)0.27 = 2.38. In addition, the height and the length of the flame were studied to better describe the flame shape when the flame is tilted. Since the flame is bent, the flame length has an abrupt change at a specific position, and the inclination angle also has the same phenomenon. Finally, it was found that the influence of the length–width ratio on the line fires is relatively limited, which is further weakened under a greater length–width ratio.
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Krikunova, Anastasia. "Numerical simulation of combustion instabilities under the alternating gravity conditions." MATEC Web of Conferences 209 (2018): 00005. http://dx.doi.org/10.1051/matecconf/201820900005.
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The work is devoted to the analysis of the methane-air conical flame behaviour under conditions of an alternating gravitational field. Numerical simulation based on the software package FlowVision, has shown the possibility of modeling the flame front instabilities during the transition from the normal gravitational conditions to zero gravity. The appearance of the flame front oscillations is demonstrated under the such conditions. Further studies will provide a complete picture of the behavior of the flame in an alternating gravitational field.
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KITAJIMA, Akio, Toshihisa UEDA, Akiko MATSUO, and Masahiko MIZOMOTO. "Turbulent Effects on the Flame behavior of Turbulent Counterflow Nonpremixed Flames." Transactions of the Japan Society of Mechanical Engineers Series B 65, no. 635 (1999): 2526–33. http://dx.doi.org/10.1299/kikaib.65.2526.
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Li, Linjie, Wuchao Zhang, Zihe Gao, and Liangwen Wei. "Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel." Indoor and Built Environment 32, no. 1 (January 2023): 286–95. http://dx.doi.org/10.1177/1420326x221147427.
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The investigation of the fire characteristics and propagation behaviour in the urban utility tunnel is of great practical importance, especially for the conditions with double fire sources. In this work, a 1/8th scaled urban utility tunnel model was built to conduct the experiments to characterize the flame merging and ceiling impingement behaviour of transversely located double fire sources. Two rectangular fire sources with the same dimension were used, and their heat release rate (HRR) and fire source spacings were varied to consider the typical scenarios. Results show that for the smaller HRR, the tunnel ceiling and sidewalls have little influence on the flame merging of double fire sources. With the increase of HRR, the flame gradually impinges on the tunnel ceiling and forms a stable ceiling jet flame extension, and the ceiling and sidewalls of the tunnel can promote the merging of the flames of the double fire sources. Besides, with the increase of the fire source spacings, the flame merging probability P m can be divided into three stages, that is, (i) complete merging stage, (ii) intermittent merging stage and (iii) complete separation stage. On this basis, the predicting relation of P m was obtained by using the piecewise function.
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De, Somnath, Arijit Bhattacharya, Sirshendu Mondal, Achintya Mukhopadhyay, and Swarnendu Sen. "Investigation of flame behavior and dynamics prior to lean blowout in a combustor with varying mixedness of reactants for the early detection of lean blowout." International Journal of Spray and Combustion Dynamics 11 (November 18, 2018): 175682771881251. http://dx.doi.org/10.1177/1756827718812519.
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Lean blowout is one of the major challenges faced when the gas turbine combustors are operated with lean fuel–air mixture to meet the emission norm. We experimentally study the flame behavior and the dynamics of heat release rate fluctuations during a transition to lean blowout. The study comprising flame visualization and estimating several measures to predict lean blowout for both premixed and partially premixed flames (using fuel ports F1 to F5) in a swirl stabilized dump combustor. To that end, we acquire unsteady heat release rate in terms of CH* chemiluminescence obtained through a photomultiplier tube with a narrow band-pass filter. For evaluating different statistical measures, we use National Instrument Labview software while acquiring the heat release rate oscillations. For premixed and partially premixed flames, such measures and the flame behavior show a different and, in some cases, even opposite trends as lean blowout is approached. However, in both premixed and partially premixed flames, the mean and root mean square values of the heat release rate fluctuation decrease as we decrease the equivalence ratio. Further, we show that the value of mean frequency calculated using Hilbert transform of the heat release rate fluctuations is a good indicator of lean blowout. Apart from the early prediction of lean blowout, different statistics of heat release rate oscillations, such as kurtosis and skewness, are shown to identify only the occurrence of lean blowout for premixed (F1 and F2) and flames with lower level of premixing (F3). They are not useful for the flames with high levels of unmixedness like F4 and F5. On the other side, probability density function is seen useful for both premixed and partially premixed flames. In short, we present the relative importance of different measures stated earlier for the identification and early prediction of lean blowout for both premixed and partially premixed flames.
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Ravichandran, Rahul Ravi, Sambit Supriya Dash, and Vinayak Malhotra. "EXPERIMENTAL INVESTIGATION ON THE ROLE OF THERMO-ACOUSTICS ON SOOT FORMATION." International Journal of Research -GRANTHAALAYAH 6, no. 6 (June 30, 2018): 461–71. http://dx.doi.org/10.29121/granthaalayah.v6.i6.2018.1391.
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Combustion is a complex phenomenon that involves the interaction of multiple phenomena, the cumulative effect of which give rise to the common flame that comprises wide range of practical, functional to propulsion applications. An interesting aspect that needs attention is the effect of the various surrounding environment phenomenon on its behavior and properties of premixed flames. It is noteworthy that soot formation is the main cause of pollution and a major cause of inefficiency of current propulsion systems. These phenomena root variety of energy interactions leading to energy transformations which in turn affect the flame behavior. Present work focuses on experimental investigations and implications of the externally induced acoustics on partially premixed flames. The subject is extensively studied as thermo-acoustics, and the current work emphases on studying its role on soot formation on premixed flames. Experimentation was carried out on a scaled setup comprising of a butane cylinder fitted with a nozzle, that houses 3 arrays consisting of 4 holes each placed equidistant to each other for entraining air. The resulting flame is impinged with acoustics from two independent and similar sources placed equidistant from the center of the nozzle. The entire process is systematically video graphed using a 60-fps regular CCD and analyzed for variation in flame heights and flickering frequencies. The observations involve fixed fuel mass flow rate with varying configuration of entrainment holes and acoustic frequency under normal ambient atmospheric conditions. The work establishes significant outcomes on the effect of acoustics on soot formation. The results are likely to encourage better understanding with applicability to commercial and domestic utilizations for energy generation for enhanced effectiveness and reduced hazards.
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Saylam, Ahmad. "Behavior of Premixed Sooting Flame in a High-Pressure Burner." Reactions 4, no. 1 (February 2, 2023): 155–70. http://dx.doi.org/10.3390/reactions4010009.
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The second-order factor effect of burner optical ports and edge inter-matrices (EIM) and the first-order factor of pressure on the soot formation process and behavior of premixed sooting flames in a high-pressure burner are numerically investigated here. Three-dimensional computational fluid dynamics (CFD) simulations of a premixed flame C2H4/air at p = 1.01 and 10 bar using a one-step chemistry approach are first performed to justify the satisfied predictability of the prospective axisymmetric two-dimensional (2D) and one-dimensional (1D) simulations. The justified 2D simulation approach shows the generation of an axial vorticity around the EIM and axial multi-vorticities due to the high expansion rate of burnt gases at the high pressure of 10 bar. This leads to the development of axial multi-sooting zones, which are manifested experimentally by visible luminous soot streaks, and to the boosting of soot formation conditions of a relatively low-temperature field, <1800 K, and a high mixing rate of gases in combustion around and above the EIM location. Nevertheless, a tolerable effect on the centerline soot volume fraction (fV) profile, fV < 3%, is manifested only at high heights above the burner of the atmospheric sooting flame C2H4/air ϕ = 2.1, and early at the high pressure of 10 bar of this flame, fV < 10%. Enhancing the combustion process reactivity by decreasing the rich equivalence ratio of the fuel/air mixture and/or rising the pressure results in the prior formation of soot precursors, which shifts the sooting zone upstream.
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Blunsdon, C. A., Z. Beeri, W. M. G. Malalasekera, and J. C. Dent. "Comprehensive Modeling of Turbulent Flames With the Coherent Flame-Sheet Model—Part I: Buoyant Diffusion Flames." Journal of Energy Resources Technology 118, no. 1 (March 1, 1996): 65–71. http://dx.doi.org/10.1115/1.2792695.
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A modified version of the computational fluid dynamics code KIVA-II was used to model the transient behavior of buoyant turbulent diffusion flames burning in still air. Besides extensions to the range of permitted boundary conditions and the addition of buoyancy terms to the turbulence model, KIVA-II was augmented by a version of the coherent flame-sheet model, Tesner’s soot generation model, Magnussen’s soot oxidation model, and an implementation of the discrete transfer radiation model that included both banded and continuum radiation. The model captured many of the features of buoyant turbulent flames. Its predictions supported experimental observations regarding the presence and frequency of large-scale pulsations, and regarding axial distributions of temperature, velocity, and chemical species concentrations. The radial structure of the flame was less well represented. The axial radiative heat flux distribution from the flame highlighted deficiencies in the soot generation model, suggesting that a model of soot particle growth was required.
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Yanagi, Tetsui, and Noboru Kagawa. "Study on Burning Velocity of Premixed Turbulent Flames with Wrinkled Laminar Flame Structure. Behavior of Vibrating Flames and Flame Propagation Model." Transactions of the Japan Society of Mechanical Engineers Series B 61, no. 586 (1995): 2283–89. http://dx.doi.org/10.1299/kikaib.61.2283.
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Rohde, K., NA Watson, and U. Jondelius. "Ultrastructure of the Protonephridia of Syndisyrinx-Punicea (Hickman, 1956) (Rhabdocoela, Umagillidae) and Pterastericola-Pellucida Jondelius, 1989 (Rhabdocoela, Pterastericolidae)." Australian Journal of Zoology 40, no. 4 (1992): 385. http://dx.doi.org/10.1071/zo9920385.
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Many flame bulbs of Syndisyrinx punicea (Rhabdocoela: Umagillidae) are formed by one perikaryon containing many mitochondria and a reticulum of membranes mainly in its periphery. Large liquid-filled lacunae were seen in the perikaryon and adjacent to it. Flame bulbs are without junctions, without external and internal leptotriches; the weir consists of some indistinct longitudinal ribs of variable size arranged in a single row, and bundles of microtubules extend along the flame bulb. Cilia are tightly packed, with microtubules oriented identically. Many flame bulbs open into one capillary with a long convoluted, partly septate junction extending to the surface cell membrane, with many microtubules running parallel with the capillary, and lateral flames. In Pterastericola pellucida (Rhabdocoela: Pterastericolidae), flame bulbs and capillaries have a similar structure, but the reticulum is more extensive, and the ribs of the weir are more distinct. The structure of the flame bulbs supports the view (based on similar morphology and hosts) that the Umagillidae and the Pterastericolidae are closely related to each other, and are typical 'turbellarian' Rhabdocoela. Many flame bulbs connected to a single perikaryon, flame bulbs with a single row of longitudinal ribs and bundles of microtubules but lacking internal leptotriches and a septate junction are synapomorphic for the Rhabdocoela (excluding the Neodermata).
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Yun, Jin Han, Dae Geun Park, Sang In Keel, and Jeong Park. "Behavior of Low Strain Rate Flame Disks in Counterflow Diffusion Flame." International Journal of Spray and Combustion Dynamics 1, no. 4 (December 2009): 473–95. http://dx.doi.org/10.1260/175682709789685813.
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Sebbar, N., T. Zirwes, P. Habisreuther, J. W. Bozzelli, H. Bockhorn, and D. Trimis. "S2 + Air Combustion: Reaction Kinetics, Flame Structure, and Laminar Flame Behavior." Energy & Fuels 32, no. 10 (June 15, 2018): 10184–93. http://dx.doi.org/10.1021/acs.energyfuels.8b01019.
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IDEGUCHI, Koji, YUIiei OMAE, Takamitsu YOSHIMOTO, and Toshimi TAKAGI. "223 Flame Behavior and Stability on Radial Horizontal Jet diffusion Flame." Proceedings of Conference of Kansai Branch 2011.86 (2011): _2–29_. http://dx.doi.org/10.1299/jsmekansai.2011.86._2-29_.
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IDEGUCHI, Koji, Ryoji TAKASHIMA, Takamitsu YOSHIMOTO, and Toshimi TAKAGI. "1010 Flame Behavior and Stability on Radial Horizontal Jet diffusion Flame." Proceedings of Conference of Kansai Branch 2012.87 (2012): _10–10_. http://dx.doi.org/10.1299/jsmekansai.2012.87._10-10_.
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Youming Yang, Xichang Shi, and Ruirong Zhao. "Flame Retardancy Behavior of Zinc Borate." Journal of Fire Sciences 17, no. 5 (September 1999): 355–61. http://dx.doi.org/10.1177/073490419901700502.
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Nelson Jr., Ralph M., and Carl W. Adkins. "Flame characteristics of wind-driven surface fires." Canadian Journal of Forest Research 16, no. 6 (December 1, 1986): 1293–300. http://dx.doi.org/10.1139/x86-229.
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Twenty-two fires in a laboratory wind tunnel and 8 field fires were studied with video techniques to determine relationships between their flame characteristics and fire behavior. The laboratory fires were in pine needle fuel beds with and without an overlying stratum of live vegetation. These fuels simulated 2-year roughs in southeastern fuel types. The field bums were in 1- and 2-year roughs in similar fuels. Byram's fire intensity ranged from 98 to 590 kW/m in the laboratory, and from 355 to 2755 kW/m in the field. Flame lengths were proportional to the square root of fire intensity when fuel consumption exceeded 0.5 kg/m2, in agreement with predictions from buoyant flame theory. However, for burns in the needle layer (consumption approximately 0.5 kg/m2), flame lengths were constant at about 0.5 m, regardless of intensity. Similar values were observed on two of the field fires. It is speculated that flame length is limited by a boundary layer pattern for the overall flow, even though the flames themselves did not exhibit boundary layer characteristics. Also, laboratory correlations of flame tilt angle and fire intensity with other fire and weather variables depart from buoyant flame theory. Further study under field conditions is needed before relationships involving flame tilt angle, fire intensity, and wind speed should be used in practical applications.
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Ugarte, Orlando J., and V’yacheslav Akkerman. "Computational Study of Premixed Flame Propagation in Micro-Channels with Nonslip Walls: Effect of Wall Temperature." Fluids 6, no. 1 (January 11, 2021): 36. http://dx.doi.org/10.3390/fluids6010036.
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This investigation evaluates the propagation of premixed flames in narrow channels with isothermal walls. The study is based on the numerical solution of the set of fully-compressible, reacting flow equations that includes viscosity, diffusion, thermal conduction and Arrhenius chemical kinetics. Specifically, channels and pipes with one extreme open and one extreme closed are considered such that a flame is sparked at the closed extreme and propagates towards the open one. The isothermal channel walls are kept at multiple constant temperatures in the range from Tw=300 K to 1200 K. The impact of these isothermal walls on the flame dynamics is studied for multiple radii of the channel (R) and for various thermal expansion ratios (Θ), which approximate the thermal behavior of different fuel mixtures in the system. The flame dynamics in isothermal channels is also compared to that with adiabatic walls, which were previously found to produce exponential flame acceleration at the initial stage of the burning process. The results show that the heat losses at the walls prevent strong acceleration and lead to much slower flame propagation in isothermal channels as compared to adiabatic ones. Four distinctive regimes of premixed burning in isothermal channels have been identified in the Θ−Tw−R space: (i) flame extinction; (ii) linear flame acceleration; (iii) steady or near-steady flame propagation; and (iv) flame oscillations. The physical processes in each of these regimes are discussed, and the corresponding regime diagrams are presented.
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MOHD AZAHARI, Bin Razali, Masataro SUZUKI, and Wataru MASUDA. "1010 Effects of Synthetic Material on Flame Spread Behavior over Combined Fabrics." Proceedings of Conference of Hokuriku-Shinetsu Branch 2010.47 (2010): 365–66. http://dx.doi.org/10.1299/jsmehs.2010.47.365.
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Papanikolaou, N., and I. Wierzba. "The Effects of Burner Geometry and Fuel Composition on the Stability of a Jet Diffusion Flame." Journal of Energy Resources Technology 119, no. 4 (December 1, 1997): 265–70. http://dx.doi.org/10.1115/1.2795000.
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The effect of the burner configuration and fuel composition on the stability limits of jet diffusion flames issuing into a co-flowing air stream is presented. Circular and elliptic nozzles of various lip thicknesses and aspect ratios were employed with methane as the primary fuel and hydrogen, carbon dioxide, and nitrogen as additives. It was found that the effects of nozzle geometry, fuel composition, and co-flowing stream velocity on the blowout limits were highly dependent on the type of flame stabilization mechanism, i.e., whether lifted or rim-attached, just prior to blowout. The blowout behavior of lifted flames did not appear to be significantly affected by a change in the nozzle shape as long as the discharge area remained constant, but it was greatly affected by the fuel composition. In contrast, attached flame stability was influenced by both the fuel composition and the nozzle geometry which had the potential to extend the maximum co-flowing stream velocity without causing the flame to blow out. The parameters affecting the limiting stream velocity were studied.
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OKU, Yohei, Kazuhiro YAMAMOTO, Naoki HAYASHI, and Hiroshi YAMASHITA. "311 A Study on Flame Behavior and Flow Field of Lifted Flames." Proceedings of Conference of Tokai Branch 2013.62 (2013): 171–72. http://dx.doi.org/10.1299/jsmetokai.2013.62.171.
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Merchan-Breuer, Duncan A., Ethan Murphy, Benjamin Berka, Luis Carlos Mendoza Nova, Yingtao Liu, and Wilson Merchan-Merchan. "Synthesis of Carbonaceous Hydrophobic Layers through a Flame Deposition Process." Applied Sciences 12, no. 5 (February 25, 2022): 2427. http://dx.doi.org/10.3390/app12052427.
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In this study we report the effect of fuel type (biodiesel vs. methane), flame structure and flame height (inner-cone vs. outer-cone), and the percent of oxygen content in the oxidizer stream for the formation of hydrophobic carbon layers using co-flow diffusion flames. It was found that a flame formed using a gaseous fuel (methane) over a vaporized liquid fuel, Canola Methyl Ester (CME), has significant structural differences that enable vastly different deposition behavior of soot layers on the surface of solid substrates. Due to its larger pyrolysis zone (taller inner-cone), the CH4/air flame has a smaller region that supports uniform soot deposition of hydrophobic carbon layers (C-layers) compared to the CME/air flame. When a solid substrate is placed within the pyrolysis zone (inner-cone) of a flame the resulting layer is non-uniform, hydrophilic, and consists of undeveloped soot. However, when outside the pyrolysis zone, the deposited soot tends to be uniform and mature, ultimately creating a hydrophobic C-layer consisting of the typical microscale interconnected weblike structures formed of spherical soot nanoparticles. The effect of oxygen content (35% and 50% O2) in the oxidizer stream for the formation of hydrophobic C-layers was also studied in this work. It was found that oxygen enrichment within the CME flame alters the structure of the flame, hence affecting the morphology of the formed C-layer. Under oxygen enrichment the central region of the deposited C-layer is composed of a weblike structure similar to those seen in the air flames; however, this central region is bordered by a region of densely compacted soot that shows signs of significant thermal stress. At 35% O2 the thermal stress is expressed as multiple microscale cracks while at 50% O2 this border region shows much larger cracks and macroscale layer peeling. The formed C-layers under the different flame conditions were tested for hydrophobicity by measuring the contact angle of a water droplet. The morphology of the C-layers was analyzed using scanning electron microscopy.
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Maynard, Trevor, Marko Princevac, and David R. Weise. "A Study of the Flow Field Surrounding Interacting Line Fires." Journal of Combustion 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/6927482.
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The interaction of converging fires often leads to significant changes in fire behavior, including increased flame length, angle, and intensity. In this paper, the fluid mechanics of two adjacent line fires are studied both theoretically and experimentally. A simple potential flow model is used to explain the tilting of interacting flames towards each other, which results from a momentum imbalance triggered by fire geometry. The model was validated by measuring the velocity field surrounding stationary alcohol pool fires. The flow field was seeded with high-contrast colored smoke, and the motion of smoke structures was analyzed using a cross-correlation optical flow technique. The measured velocities and flame angles are found to compare reasonably with the predicted values, and an analogy between merging fires and wind-blown flames is proposed.