Gotowe bibliografie tematyczne / Flame blowoff

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Gotowa bibliografia na temat „Flame blowoff”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Flame blowoff"

Zhang, Qingguo, David R. Noble i Tim Lieuwen. "Characterization of Fuel Composition Effects in H2∕CO∕CH4 Mixtures Upon Lean Blowout". Journal of Engineering for Gas Turbines and Power 129, nr 3 (26.12.2006): 688–94. http://dx.doi.org/10.1115/1.2718566.

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This paper describes measurements of the dependence of lean blowout limits upon fuel composition for H2∕CO∕CH4 mixtures. Blowout limits were obtained at fixed approach flow velocity, reactant temperature, and combustor pressure at several conditions. Consistent with prior studies, these results indicate that the percentage of H2 in the fuel dominates the mixture blowout characteristics. That is, flames can be stabilized at lower equivalence ratios, adiabatic flame temperatures, and laminar flame speeds with increasing H2 percentage. In addition, the blowoff phenomenology qualitatively changes with hydrogen levels in the fuel, being very different for mixtures with H2 levels above and below about 50%. It is shown that standard well stirred reactor based correlations, based upon a Damköhler number with a diffusivity ratio correction, can capture the effects of fuel composition variability on blowoff limits.

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SAMESHIMA, Taiki, Mitsuharu TAKAO, Toshiaki YANO i Shuichi TORII. "FLAME BLOWOFF LIMITS EXTENTION BY FLAME HOLDER WITH AIR-SUCTION". Proceedings of Conference of Kyushu Branch 2002.55 (2002): 191–92. http://dx.doi.org/10.1299/jsmekyushu.2002.55.191.

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Patel, Vipul, i Rupesh Shah. "Analysis of LPG diffusion flame in tube type burner". Journal of Mechanical Engineering and Sciences 13, nr 3 (26.09.2019): 5278–93. http://dx.doi.org/10.15282/jmes.13.3.2019.05.0431.

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The present research aims to analyse diffusion flame in a tube type burner with Liquefied petroleum gas (LPG) as a fuel. An experimental investigation is performed to study flame appearance, flame stability, Soot free length fraction (SFLF) and CO emission of LPG diffusion flame. Effects of varying air and fuel velocities are analysed to understand the physical process involved in combustion. SFLF is measured to estimate the reduction of soot. Stability limits of the diffusion flame are characterized by the blowoff velocity. Emission characteristic in terms of CO level is measured at different equivalence ratios. Experimental results show that the air and fuel velocity strongly influences the appearance of LPG diffusion flame. At a constant fuel velocity, blue zone increases and the luminous zone decreases with the increase in air velocity. It is observed that the SFLF increases with increasing air velocity at a constant fuel velocity. It is observed that the blowoff velocity of the diffusion flame increases as fuel velocity increases. Comparison of emission for flame with and without swirl indicates that swirl results in low emission of CO and higher flame stability. Swirler with 45° vanes achieved the lowest CO emission of 30 ppm at Φ = 1.3.

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Huang, Lung-Weei, i Chiun-Hsun Chen. "FLAME STABILIZATION AND BLOWOFF OVER A SINGLE DROPLET". Numerical Heat Transfer, Part A: Applications 27, nr 1 (styczeń 1995): 53–71. http://dx.doi.org/10.1080/10407789508913688.

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CHEN, CHIUN-HSUN, i FANG-BOR WENG. "Flame Stabilization and Blowoff Over a Porous Cylinder". Combustion Science and Technology 73, nr 1-3 (wrzesień 1990): 427–46. http://dx.doi.org/10.1080/00102209008951661.

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TORIKAI, Hiroyuki, Akiko MATSUO, Toshihisa UEDA i Masahiko MIZOMOTO. "Blowoff Characteristics and Flame Structure of Edge Flame in the Stagnation Flow." Transactions of the Japan Society of Mechanical Engineers Series B 68, nr 666 (2002): 610–18. http://dx.doi.org/10.1299/kikaib.68.610.

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Nair, Suraj, i Tim Lieuwen. "Near-Blowoff Dynamics of a Bluff-Body Stabilized Flame". Journal of Propulsion and Power 23, nr 2 (marzec 2007): 421–27. http://dx.doi.org/10.2514/1.24650.

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Santhosh, R., i Saptarshi Basu. "Transitions and blowoff of unconfined non-premixed swirling flame". Combustion and Flame 164 (luty 2016): 35–52. http://dx.doi.org/10.1016/j.combustflame.2015.10.034.

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Hindasageri, Vijaykumar, Rajendra Vedula i Siddini Prabhu. "Blowoff Stability of Methane-Air Premixed Flame on Tube Burners". International Journal of Emerging Multidisciplinary Fluid Sciences 3, nr 4 (wrzesień 2011): 209–26. http://dx.doi.org/10.1260/1756-8315.3.4.209.

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He, Zhonghao, Hongbo Wang, Fan Li, Yifu Tian, Minggang Wan i Jiajian Zhu. "Effect of Fuel-Injection Distance and Cavity Rear-Wall Height on the Flameholding Characteristics in a Mach 2.52 Supersonic Flow". Aerospace 9, nr 10 (29.09.2022): 566. http://dx.doi.org/10.3390/aerospace9100566.

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The ethylene-fueled flameholding characteristics of a cavity-based scramjet combustor are experimentally and numerically investigated. The test facility used the air heater, which heats air from room temperature to total temperature 1477 K. A nozzle is installed behind the heater outlet to increase the air speed to Mach 2.52. Two cavity geometries with different rear-wall heights of 8 mm and 10 mm and two injection distances upstream of the cavities of 10 mm and 40 mm are compared to show the effect of these parameters. The CH* spontaneous emission images obtained by dual-camera synchronous shooting and the wall-pressure distribution obtained by a pressure-scan system are used to capture the flame dynamics. The global equivalence ratio range for different combination schemes is controlled from 0.14 to 0.27 in this paper. The results show that the conventional cavity (the rear-wall height is 10 mm) and the shorter injection distance can effectively decrease the lean blowoff limit of the combustor, while the rear-wall-expansion cavity (the rear-wall height is 8 mm) and the longer injection distance can effectively increase the rich blowoff limit. Compared with the injection distance, the rear-wall height of the cavity has little effect on the oscillation distribution of the shear layer-stabilized flame. However, the fuel-injection distance and cavity rear-wall height both have great influence on the spatial distribution of the flame.

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Rozprawy doktorskie na temat "Flame blowoff"

Shroll, Andrew Philip. "Dynamic stability, blowoff, and flame characteristics of oxy-fuel combustion". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67803.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 83-86).
Oxy-fuel combustion is a promising technology to implement carbon capture and sequestration for energy conversion to electricity in power plants that burn fossil fuels. In oxy-fuel combustion, air separation is used to burn fuel in oxygen to easily obtain a pure stream of carbon dioxide from the products of combustion. A diluent, typically carbon dioxide, is recycled from the exhaust to mitigate temperature. This substitution of carbon dioxide with the nitrogen in air alters the thermodynamics, transport properties, and relative importance of chemical pathways of the reacting mixture, impacting the flame temperature and stability of the combustion process. In this thesis, methane oxy-combustion flames are studied for relevance to natural gas. First, a numerical 1-D strained flame shows significantly reduced consumption speeds for oxy-combustion compared to air combustion at the same adiabatic flame temperature. Competition for the H radical from the presence of carbon dioxide causes high CO emissions. Elevated strain rates also cause incomplete combustion in oxy-combustion, demonstrated by the effect of Lewis number with a value greater than one for flame temperatures under 1900 K. Most of this work focuses on experimental results from premixed flames in a 50 kW axi-symmetric swirl-stabilized combustor. Combustion instabilities, upon which much effort is expended to avoid in gas turbines with low pollutant emissions, are described as a baseline for the given combustor geometry using overall sound pressure level maps and chemiluminescence images of 1/4, 3/4, and 5/4 wave mode limit cycles. These oxy-combustion results are compared to conventional air combustion, and the collapse of mode transitions with temperature for a given Reynolds number is found. Hysteresis effects in mode transition are important and similar for air and oxy-combustion. Blowoff trends are also analyzed. While oxy-combustion flames blow off at a higher temperature for a given Reynolds number due to weaker flames, there is an unexpected negative slope in blowoff velocity vs temperature for both air and oxy-combustion. The blowoff data are shown to collapse due to blowoff velocity being inversely proportional to the molar heat capacities of the burned gas mixtures at a given power. Finally, particle image velocimetry results are discussed to relate flow structures to corresponding flame structures.
by Andrew Philip Shroll.
S.M.

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Foley, Christopher William. "Attachment point characteristics and modeling of shear layer stabilized flames in an annular, swirling flowfield". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54357.

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The focus of this work was to develop a deeper understanding of the mechanisms of flame stabilization and extinction for shear layer stabilized, premixed flames. Planar experimental studies were performed in the attachment point region of an inner shear layer stabilized flame in an annular, swirl combustor. Through high resolution, simultaneous PIV & CH-PLIF measurements, the instantaneous flow field and flame position was captured enabling the characterization of 2D flame stretch and velocity conditions in the attachment point region. In addition, measurements performed at various equivalence ratios and premixer velocities provided insight into the physics governing blowoff. Most notably, these studies showed that as lean blowoff conditions are approached by decreasing equivalence ratio, the mean stretch rates near the attachment point decrease but remain positive throughout the measurement domain. In fact, compared to numerically calculated extinction stretch rates, the flame becomes less critically stretched as equivalence ratio is decreased. Also, investigation of the flame structure at the leading edge of the flame showed strong evidence that the flame is edge flame stabilized. This was supported by inspection of the CH-PLIF images, which showed the CH-layer oriented tangent to the flow field and terminating abruptly at the leading edge. Lastly, the flame anchoring location was observed to be highly robust as the mean flame edge flow conditions and mean location of leading edge of the flame were insensitive to changes in equivalence ratio, remaining nearly constant for values ranging from 0.9 to 1.1. However, at the leanest equivalence ratio of 0.8, the flame leading edge was located farther downstream and subject to much higher flow velocities. These results thus suggest that blowoff is the result of a kinematic balance and not directly from stretch induced flame extinction.

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Binti, Munajat Nur Farizan. "Combustion of gasified biomass: : Experimental investigation on laminar flame speed, lean blowoff limit and emission levels". Doctoral thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-120570.

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Biomass is among the primary alternative energy sources that supplements the fossil fuels to meet today’s energy demand. Gasification is an efficient and environmental friendly technology for converting the energy content in the biomass into a combustible gas mixture, which can be used in various applications. The composition of this gas mixture varies greatly depending on the gasification agent, gasifier design and its operation parameters and can be classified as low and medium LHV gasified biomass. The wide range of possible gas composition between each of these classes and even within each class itself can be a challenge in the combustion for heat and/or power production. The difficulty is primarily associated with the range in the combustion properties that may affect the stability and the emission levels. Therefore, this thesis is intended to provide data of combustion properties for improving the operation or design of atmospheric combustion devices operated with such gas mixtures. The first part of this thesis presents a series of experimental work on combustion of low LHV gasified biomass (a simulated gas mixture of CO/H2/CH4/CO2/N2) with variation in the content of H2O and tar compound (simulated by C6H6). The laminar flame speed, lean blowoff limit and emission levels of low LHV gasified biomass based on the premixed combustion concept are reported in paper I and III. The results show that the presence of H2O and C6H6 in gasified biomass can give positive effects on these combustion parameters (laminar flame speed, lean blowoff limit and emission levels), but also that there are limits for these effects. Addition of a low percentage of H2O in the gasified biomass resulted in almost constant laminar flame speed and combustion temperature of the gas mixture, while its NOx emission and blowoff temperature were decreased. The opposite condition was found when H2O content was further increased. The blowoff limit was shifted to richer fuel equivalence ratio as H2O increased. A temperature limit was observed where CO emission could be maintained at low concentration. With C6H6 addition, the laminar flame speed first decreased, achieved a minimum value, and then increased with further addition of C6H6. The combustion temperature and NOx emission were increased, CO emission was reduced, and blowoff occurs at slightly higher equivalence ratio and temperature when C6H6 content is increased. The comparison with natural gas (simulated by CH4) is also made as can be found in paper I and II. Lower laminar flame speed, combustion temperature, slightly higher CO emission, lower NOx emission and leaner blowoff limit were obtained for low LHV gas mixture in comparison to natural gas. In the second part of the thesis, the focus is put on the combustion of a wide range of gasified biomass types, ranging from low to medium LHV gas mixture (paper IV). The correlation between laminar flame speed or lean blowoff limit and the composition of various gas mixtures was investigated (paper IV). It was found that H2 and content of diluents have higher influence on the laminar flame speed of the gas mixture compared to its CO and hydrocarbon contents. For lean blowoff limit, the diluents have the greatest impact followed by H2 and CO. The mathematical correlations derived from the study can be used to for models of these two combustion parameters for a wide range of gasified biomass fuel compositions.

QC 20130411

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Huelskamp, Bethany C. "The Development of a Correlation to Predict the Lean Blowout of Bluff Body Stabilized Flames with a Focus on Relevant Timescales and Fuel Characteristics". University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1367192147.

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Bompelly, Ravi K. "Lean blowout and its robust sensing in swirl combustors". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47529.

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Lean combustion is increasingly employed in both ground-based gas turbines and aircraft engines for minimizing NOx emissions. Operating under lean conditions increases the risk of Lean Blowout (LBO). Thus LBO proximity sensors, combined with appropriate blowout prevention systems, have the potential to improve the performance of engines. In previous studies, atmospheric pressure, swirl flames near LBO have been observed to exhibit partial extinction and re-ignition events called LBO precursors. Detecting these precursor events in optical and acoustic signals with simple non-intrusive sensors provided a measure of LBO proximity. This thesis examines robust LBO margin sensing approaches, by exploring LBO precursors in the presence of combustion dynamics and for combustor operating conditions that are more representative of practical combustors, i.e., elevated pressure and preheat temperature operation. To this end, two combustors were used: a gas-fueled, atmospheric pressure combustor that exhibits pronounced combustion dynamics under a wide range of lean conditions, and a low NOx emission liquid-fueled lean direct injection (LDI) combustor, operating at elevated pressure and preheat temperature. In the gas-fueled combustor, flame extinction and re-ignition LBO precursor events were observed in the presence of strong combustion dynamics, and were similar to those observed in dynamically stable conditions. However, the signature of the events in the raw optical signals have different characteristics under various operating conditions. Low-pass filtering and a single threshold-based event detection algorithm provided robust precursor sensing, regardless of the type or level of dynamic instability. The same algorithm provides robust event detection in the LDI combustor, which also exhibits low level dynamic oscillations. Compared to the gas-fueled combustor, the LDI events have weaker signatures, much shorter durations, but considerably higher occurrence rates. The disparity in precursor durations is due to a flame mode switch that occurs during precursors in the gas-fueled combustor, which is absent in the LDI combustor. Acoustic sensing was also investigated in both the combustors. Low-pass filtering is required to reveal a precursor signature under dynamically unstable conditions in the gas-fueled combustor. On the other hand in the LDI combustor, neither the raw signals nor the low-pass filtered signals reveal precursor events. The failure of acoustic sensing is attributed in part to the lower heat release variations, and the similarity in time scales for the precursors and dynamic oscillations in the LDI combustor. In addition, the impact of acoustic reflections from combustor boundaries and transducer placement was addressed by modeling reflections in a one-dimensional combustor geometry with an impedance jump caused by the flame. Implementing LBO margin sensors in gas turbine engines can potentially improve time response during deceleration transients by allowing lower operating margins. Occurrence of precursor events under transient operating conditions was examined with a statistical approach. For example, the rate at which the fuel-air ratio can be safely reduced might be limited by the requirement that at least one precursor occurs before blowout. The statistics governing the probability of a precursor event occurring during some time interval was shown to be reasonably modeled by Poisson statistics. A method has been developed to select a lower operating margin when LBO proximity sensors are employed, such that the lowered margin case provides a similar reliability in preventing LBO as the standard approach utilizing a more restrictive operating margin. Illustrative improvements in transient response and reliabilities in preventing LBO are presented for a model turbofan engine. In addition, an event-based, active LBO control approach for deceleration transients is also demonstrated in the engine simulation.

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Nair, Suraj. "Acoustic Characterization of Flame Blowout Phenomenon". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10413.

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Combustor blowout is a very serious concern in modern land-based and aircraft engine combustors. The ability to sense blowout precursors can provide significant payoffs in engine reliability and life. The objective of this work is to characterize the blowout phenomenon and develop a sensing methodology which can detect and assess the proximity of a combustor to blowout by monitoring its acoustic signature, thus providing early warning before the actual blowout of the combustor. The first part of the work examines the blowout phenomenon in a piloted jet burner. As blowout was approached, the flame detached from one side of the burner and showed increased flame tip fluctuations, resulting in an increase in low frequency acoustics. Work was then focused on swirling combustion systems. Close to blowout, localized extinction/re-ignition events were observed, which manifested as bursts in the acoustic signal. These events increased in number and duration as the combustor approached blowout, resulting an increase in low frequency acoustics. A variety of spectral, wavelet and thresholding based approaches were developed to detect precursors to blowout. The third part of the study focused on a bluff body burner. It characterized the underlying flame dynamics near blowout in greater detail and related it to the observed acoustic emissions. Vorticity was found to play a significant role in the flame dynamics. The flame passed through two distinct stages prior to blowout. The first was associated with momentary strain levels that exceed the flames extinction strain rate, leading to flame holes. The second was due to large scale alteration of the fluid dynamics in the bluff body wake, leading to violent flapping of the flame front and even larger straining of the flame. This led to low frequency acoustic oscillations, of the order of von Karman vortex shedding. This manifested as an abrupt increase in combustion noise spectra at 40-100 Hz very close to blowout. Finally, work was also done to improve the robustness of lean blowout detection by developing integration techniques that combined data from acoustic and optical sensors.

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Zhang, Qingguo. "Lean blowoff characteristics of swirling H2/CO/CH4 Flames". Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22641.

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This thesis describes an experimental investigation of lean blowoff for H2/CO/CH4 mixtures in a swirling combustor. This investigation consisted of three thrusts. The first thrust focused on correlations of the lean blowoff limits of H2/CO/CH4 mixtures under different test conditions. It was found that a classical Damköhler number approach with a diffusion correction could correlate blowoff sensitivities to fuel composition over a range of conditions. The second part of this thesis describes the qualitative flame dynamics near blowoff by systematically characterizing the blowoff phenomenology as a function of hydrogen level in the fuel. These near blowoff dynamics are very complex, and are influenced by both fluid mechanics and chemical kinetics; in particular, the role of thermal expansion across the flame and extinction strain rate were suggested to be critical in describing these influences. The third part of this thesis quantitatively analyzed strain characteristics in the vicinity of the attachment point of stable and near blowoff flames. Surprisingly, it was found that in this shear layer stabilized flame, flow deceleration is the key contributor to flame strain, with flow shear playing a relatively negligible role. Near the premixer exit, due to strong flow deceleration, the flame is negatively strained i.e., compressed. Moving downstream, the strain rate increases towards zero and then becomes positive, where flames are stretched. As the flame moves toward blowoff, holes begin to form in the flame sheet, with a progressively higher probability of occurrence as one moves downstream. It is suggested that new holes form with a more uniform probability, but that this behavior reflects the convection of flame holes downstream by the flow. It has been shown in prior studies, and affirmed in this work, that flames approach blowoff by first passing through a transient phase manifested by local extinction events and the appearance of holes on the flame. A key conclusion of this work is that the onset of this boundary occurs at a nearly constant extinction strain rate. As such, it is suggested that Damköhler number scalings do not describe blowoff itself, but rather the occurrence of this first stage of blowoff. Given the correspondence between this first stage and the actual blowoff event, this explains the success of classical Damköhler number scalings in describing blowoff, such as shown in the first thrust of this thesis. The physics process associated with the actual blowoff event is still unclear and remains a key task for future work.

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Husain, Sajjad A. "Analysis of blowoff scaling of bluff body stabilized flames". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22565.

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Moore, Nancy Jennings. "Effects of Leading-Edge Flame Behavior on Flame Stabilization and Blowout". NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-10012009-135737/.

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The goal of this work was to identify the mechanisms that effect stabilization of hydrocarbon jet flames. Methane, nitrogen, and co-flowing air were regulated and directed through a burner that created fully-developed fuel flow with concurrent air. The behavior of the reaction zone at the leading-edge was analyzed from digital images obtained from a camera optimally positioned to capture the movements of the entire flame front. Low Reynolds number flows allowed for the investigation of hysteretic behavior. The hysteresis regime refers to the situation where the jet flame has dual positions favorable to flame stabilization: attached and lifted. Results indicate that flame height in hysteresis is significantly impacted by high velocities of co-flow and that past a critical value a local minimum will be created. Fully turbulent lifted flames were also studied to determine the fluctuations in the height of lifted methane flames in the presence of air co-flow. The partially-premixed flame front of the lifted flame fluctuates in the axial direction, with the fluctuations becoming greater in flames stabilized further downstream. These fluctuations are also observed in flames where blowout is imminent. The height and rate of these fluctuations are studied with respect to average height, flow velocities, and Reynolds number. Additionally, the mechanisms that cause jet-flame blowout, particularly in the presence of air co-flow, are not completely understood. Two types of experiments are described, and the data report that a predictor of blowout is the prior disappearance of the axially-oriented flame branch which is consistently witnessed despite a turbulent flameâs inherent variable behavior. The conclusions are supported by experiments with nitrogen-diluted flames. A blowout parameter is also calculated for methane flames in co-flow and diluted methane flames that can be used to predict at what flow velocities blowout will occur. This work analyzes flames near the burner, in the far field, and approaching blowout. The comprehensive study allows for the realization that the mechanisms of flame stabilization differ throughout the combustible field.

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Prakash, Shashvat. "Lean Blowout Mitigation in Swirl Stabilized Premixed Flames". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16159.

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Lean, premixed combustion offers a practical approach for reducing nitrogen oxide (NOx) emissions, but increases the risk of lean blowout (LBO) in gas turbines. Active control techniques are therefore sought which can stabilize a lean flame and prevent LBO. The present work has resulted in the development of flame detection, dynamic modeling, blowout margin estimation, and actuation and control techniques. The flame s acoustic emissions were bandpass filtered at select frequencies to detect localized extinction events, which were found to increase in number near LBO. The lean flame was also found to intermittently burst into a transient tornado configuration in which the flame s inner recirculation zone would collapse. The localized extinctions were dynamically linked to the tornado bursts using a linear, first order model. The model was subsequently applied to predict tornado bursts based on optically detected localized extinction events. It was found that both localized extinctions and tornado bursts are by themselves Poisson processes; the exponential distribution of their spacing times could be used to determine blowout probability. Blowout mitigation was achieved by redistributing the fuel flow between the annular swirlers and central preinjection pilot, both of which were premixed. Rule-based and lead-lag control architectures were developed and validated.

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Książki na temat "Flame blowoff"

Tangirala, V. LDV/Rayleigh scattering measurements to study the blowoff of swirling flames. New York: AIAA, 1986.

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A sea in flames: The Deepwater Horizon Oil blowout. New York: Crown Publishers, 2011.

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Części książek na temat "Flame blowoff"

Sun, Mingbo, Hongbo Wang, Zun Cai i Jiajian Zhu. "Flame Behaviors Near Blowoff in Supersonic Flows". W Unsteady Supersonic Combustion, 307–45. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3595-6_6.

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Maleta, T., R. N. Parthasarathy i S. R. Gollahalli. "Blowoff Characteristics of Laminar Partially Premixed Flames of Palm Methyl Ester/Jet A Blends". W Sustainable Development for Energy, Power, and Propulsion, 161–76. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5667-8_7.

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Sen, Swarnendu, Rajendra R. Chaudhari i Achintya Mukhopadhyay. "Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor". W Novel Combustion Concepts for Sustainable Energy Development, 199–232. New Delhi: Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-2211-8_9.

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Kumar, Rajesh, Krishna C. Kalvakala i Suresh K. Aggarwal. "Effect of Oxygenation on the Liftoff, Stabilization, and Blowout Characteristics of Laminar Co-flow Jet Flames". W Green Energy and Technology, 273–89. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-2648-7_12.

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Wierzba, I., K. Kar i G. A. Karim. "The Blowout of a Jet Diffusion Flame: The Effects of the Velocity and Composition of the Surrounding Co-Flowing Stream". W Combustion Technologies for a Clean Environment, 323–33. London: CRC Press, 2022. http://dx.doi.org/10.1201/9780367810597-25.

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De Giorgi, Maria Grazia, Sara Bonuso, Ghazanfar Mehdi, Mohamed Shamma, Stefan Raphael Harth, Nikolaos Zarzalis i Dimosthenis Trimis. "Enhancement of Blowout Limits in Lifted Swirled Flames in Methane-Air Combustor by the Use of Sinusoidally Driven Plasma Discharges". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 66–82. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-90727-3_5.

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"Flame Stabilization, Flashback, Flameholding, and Blowoff". W Unsteady Combustor Physics, 379–405. Wyd. 2. Cambridge University Press, 2021. http://dx.doi.org/10.1017/9781108889001.011.

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Streszczenia konferencji na temat "Flame blowoff"

Zhang, Qingguo, David R. Noble, Santosh J. Shanbhogue i Tim Lieuwen. "Impacts of Hydrogen Addition on Near-Lean Blowout Dynamics in a Swirling Combustor". W ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27308.

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This paper addresses the impact of H2 addition on lean blowout in premixed swirling flames. Previous work shows that the manner in which the flame blows off varies with percentage of H2 [1,2]. The objective of this paper is to follow up on these observations and systematically characterize the blowoff phenomenology as a function of the H2 levels in the fuel. This is accomplished through high speed visualizations of the flame emission and velocity field measurements. Near blowoff, a variety of highly dynamic flow features are observed, which vary substantially with the H2 levels in the fuel. These features involve complex interactions between the vortex breakdown bubble, outer recirculation zone of the rapid expansion, and flame extinction/reignition phenomenon. Key questions for future studies are the relative roles of fluid mechanics and chemical kinetics in causing the phenomenological variations in near blowoff dynamics, and which features are geometry specific and which are generic to near blowoff flame dynamics.

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Husain, Sajjad A., Ganesh Nair, Santosh Shanbhogue i Tim C. Lieuwen. "Review and Analysis of Bluff Body Flame Stabilization Data". W ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50375.

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This paper compiles and analyzes bluff body stabilized flame blowoff data from the literature. Many of these studies contain semi-empirical blowoff correlations that are, in essence, Damko¨hler number correlations of their data. This paper re-analyzes these data, utilizing various Damko¨hler number correlations based upon detailed kinetic modeling for determining chemical time scales. While the results from this compilation are similar to that deduced from many earlier studies, it demonstrates that a rather comprehensive data set taken over a large range of conditions can be correlated from “first-principles” based calculations that do not rely on empirical fits or adjustable constants (e.g., global activation energy or pressure exponents). The paper then discusses the implications of these results on understanding of blowoff. Near blowoff flames experience local extinction of the flame sheet, manifested as “holes” that form and convect downstream. However, local extinction is distinct from blowoff — in fact, under certain conditions the flame can apparently persist indefinitely with certain levels of local extinction. We hypothesize that simple Damko¨hler number correlations contain the essential physics describing this first stage of blowoff; i.e., they are correlations for the conditions where local extinction on the flame begins, but do not fundamentally describe the ultimate blowoff condition itself. However, such correlations are reasonably successful in correlating blowoff limits because the ultimate blowoff event appears to be correlated to some extent to the onset of this first stage.

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Foley, Christopher W., Jerry Seitzman i Tim Lieuwen. "Analysis and Scalings of Blowoff Limits of 2D and Axisymmetric Bluff Body Stabilized Flames". W ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-70048.

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This paper considers shear layer flame stabilization with a particular focus on velocity scaling of blowoff limits. Analysis of the expression for hydrodynamic flame stretch, κ, in a shear layer shows that it consists of two contributions, associated with normal and shearing flow strain. These two contributors lead to flame stretch scalings of SL/δ and U/L, respectively, where δ and L denote shear layer thickness and characteristic geometric length scale. These two flame stretch terms have different velocity and length scalings (roughly U1/2 and U1, respectively) and so different blowoff trends can be expected depending upon which term dominates. These scalings are used to interpret a variety of bluff body blowoff data in the literature by analyzing the velocity and length scale dependence of extinction stretch rates calculated at the measured blowoff conditions. We also show that the measured velocity sensitivities to chemical time at blowoff range from U−0.3 to U−1.6. A key point of this study is that blowoff boundaries do not necessarily follow a U−1 scaling suggested by classical Damköhler number scalings and that more work is needed to understand the controlling extinction processes of near-blowoff flames.

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Idahosa, Uyi, Abhishek Saha, Chengying Xu i Saptarshi Basu. "Characterization of Combustion Dynamics in Swirl Stabilized Flames". W ASME 2009 Power Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/power2009-81168.

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This paper investigates flame frequency response relative to changes in swirl intensity and equivalence ratio in a non-premixed swirl stabilized burner. The degree of swirl in the burner is characterized by the swirl number (S) provided by circumferentially distributed air supply ports directed tangentially to the main axial air flow. Equivalence ratio variations are induced using varying constant, linear ramp and exponentially decaying fuel (propane) flow rates towards blowoff. The variations in the air speed at the exit of the burner (U) are measured with an anemometer located at the base of the flame. The emission of CH* radicals (I) is used as a marker of flame heat release and is measured using a photomultiplier (PMT). The frequency response of the PMT heat release and burner velocity signals are analyzed in the frequency domain using the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. Amplification in the power of heat release fluctuation is observed in low swirl flames close to blowoff. This effect is found to be reversed in higher swirl number flames even close to blowoff. In dynamic approaches to blowoff (using ramp and decaying fuel flow rates), the dominant heat release fluctuation frequencies are observed to be similar to perturbation frequencies in lean flames hovering at constant fuel flow rates close to blowoff.

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Zhang, Qingguo, Santosh J. Shanbhogue i Tim Lieuwen. "Dynamics of Premixed H2/CH4 Flames Under Near-Blowoff Conditions". W ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59981.

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Swirling flows are widely used in industrial burners and gas turbine combustors for flame stabilization. Several prior studies have shown that these flames exhibit complex dynamics under near-blowoff conditions, associated with local flamelet extinction and alteration in the vortex breakdown flow structure. These extinction events are apparently due to the local strain rate irregularly oscillating above and below the extinction strain rate values near the attachment point. In this work, global, temporally resolved and detailed spatial measurements were obtained of hydrogen/methane flames. Supporting calculations of extinction strain rates were also performed using detailed kinetics. It is shown that flames become unsteady (or local extinctions happen) at a nearly constant extinction strain rate for different hydrogen/methane mixtures. Based upon analysis of these results, it is suggested that classic Damkohler number correlations of blowoff are, in fact, correlations for the onset of local-extinction events, not blowoff itself. Corresponding Mie scattering imaging of near-blowoff flames also was used to characterize the spatio-temporal dynamics of holes along the flame that are associated with local extinction.

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Torii, Shuichi, Sze Man Simon Chan i Toshiaki Yano. "Flame Blowoff Limit Phenomenon of Turbulent Jet Diffusion Flames With Annular Counterflow". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39059.

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The present study deals with the transport phenomena of turbulent jet diffusion flames with air-suction flow and the possibility of extending the flame blow-off limits through the shear stress augmentation using the annular counterflow technique. The experimental apparatus employed here comprises a fuel nozzle placed at the center of a concentric annulus with an outer cylinder adopted to encompass the nozzle. Fuel jet is allowed to eject upwards and turbulent jet diffusion flames are formed by igniting the jet and by increasing the volume flow rates of fuel. It is found that (1) the augmentation of turbulent shear effect exerted on the shear layer formed between the jet flames and the opposed flow of air causes an extension of flame blowoff limits, (2) by using the annular counterflow technique, the flame lift-off height is suppressed than the normal diffusion flame, and (3) its height is correlated using the effective air-suction momentum flux proposed here.

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Kwong, W. Y., i A. M. Steinberg. "Blowoff and Reattachment Dynamics of a Linear Multi-Nozzle Combustor". W ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75647.

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This paper describes the coupled flow and flame dynamics during blowoff and reattachment events in a combustor consisting of a linear array of five interacting nozzles using 10 kHz repetition-rate OH planar laser induced fluorescence and stereoscopic particle image velocimetry. Steady operating conditions were studied at which the three central flames randomly blew-off and subsequently reattached to the bluff-bodies. Transition of the flame from one nozzle was rapidly followed by transition of the other nozzles, indicating cross-nozzle coupling. Blow-off transitions were preferentially initiated in one of the off-center nozzles, with the transition of subsequent nozzles occurring in a random order. Similarly, the center nozzle tended to be the last nozzle to reattach. The blowoff process of any individual nozzle was similar to that for a single bluff-body stabilized flame, though with cross-flame interactions providing additional means of re-stabilizing a partially extinguished flame. Subsequent to blowoff of the first nozzle, the other nozzles underwent similar blowoff processes. Flame reattachment was initiated by entrainment of a burning pocket into a recirculation zone, followed by transport to the bluff-body; the other nozzles subsequently underwent similar reattachment processes. Several forms of cross-nozzle interaction that can promote or prevent transition are identified. Furthermore, the velocity measurements indicated that blowoff or reattachment of the first nozzle during a multi-nozzle transition causes significant changes to the flow fields of the other nozzles. It is proposed that a single nozzle transition redistributes the flow to the other nozzles in a manner that promotes their transition.

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Zare, Saeid, Hao Wei Lo, Shrabanti Roy i Omid Askari. "Flame Stability in Inverse Coaxial Injector Using Repetitive Nanosecond Pulsed Plasma". W ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10991.

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Abstract There has been recently a growing interest in the use of methane as a strong candidate for both interplanetary and descent/ascent propulsion solutions. The higher boiling point and higher density of methane compared with hydrogen, makes its storage tank lighter, cheaper and smaller to launch. Methane is abundant in the outer solar system and can be harvested on Mars, Titan, Jupiter, and many other planets and therefore, it can be used in reusable rocket engines. However, there are still some technological challenges in methane engines development path. Among those challenges, ignition reliability and flame stability are of great importance. These challenges can be addressed by integrating low-temperature plasma (LTP) through repetitive nanosecond pulsed (RNP) discharge to the injector design. This research work focuses on Air/CH4 jet flames in a single-element coaxial shear injector coupled with RNP plasma discharge to study the influence of LTP on ignition characteristics and flame stability using advanced diagnostic techniques. The experiments have been performed for different fuel composition, jet velocities, discharge voltages and frequencies at atmospheric conditions. The transient flame behavior including flame oscillation is studied using direct photography by CMOS high-speed camera. The effect of plasma discharge location on flame stability is also investigated. To demonstrate the effectiveness of RNP discharge on liftoff and blowout/blowoff velocities, the jet velocity at the critical conditions is measured in terms of discharge frequencies and the enhancement of flame stability is then evaluated. The collected experimental data have shown that the RNP discharge can significantly extend the flame stability by reducing the liftoff height and increasing the velocity at which blowout/blowoff occurs.

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Foley, C. W., I. Chterev, J. Seitzman i T. Lieuwen. "High Resolution PIV and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame". W ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43387.

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Understanding the mechanisms and physics of flame stabilization and blowoff of premixed flames is critical towards the design of high velocity combustion devices. In the high bulk flow velocity situation typical of practical combustors, the flame anchors in shear layers where the local flow velocities are much lower. Within the shear layer, fluid strain deformation rates are very high and the flame can be subjected to significant stretch levels. The main goal of this work was to characterize the flow and stretch conditions that a premixed flame experiences in a practical combustor geometry and to compare these values to calculated extinction values. High resolution, simultaneous PIV and CH-PLIF measurements are used to capture the flame edge and near-field stabilization region. When approaching lean limit extinction conditions, we note characteristic changes in the stretch and flow conditions experienced by the flame. Most notably, the flame becomes less critically stretched when fuel/air ratio is decreased. However, at these lean conditions, the flame is subject to higher mean flow velocities at the edge, suggesting less favorable flow conditions are present at the attachment point of the flame as blowoff is approached. These measurements suggest that blowoff of the flame from the shear layer is not directly stretch extinction induced, but rather the result of an imbalance between the speed of the flame edge and local tangential flow velocity.

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Zhang, Qingguo, David R. Noble, Andrew Meyers, Kunning Xu i Tim Lieuwen. "Characterization of Fuel Composition Effects in H2/CO/CH4 Mixtures Upon Lean Blowout". W ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68907.

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This paper describes measurements of the dependence of lean blowout limits upon fuel composition for H2/CO/CH4 mixtures. Blowout limits were obtained at fixed approach flow velocity, reactant temperature, and combustor pressure at several conditions up to 4.4 atm and 470 K inlet reactants temperature. Consistent with prior studies, these results indicate that the percentage of H2 in the fuel dominates the mixture blowoff characteristics. That is, flames can be stabilized at lower equivalence ratios, adiabatic flame temperatures, and laminar flame speeds with increasing H2 percentage. Various methods of correlating these data were evaluated, using combinations of Lewis number (Lemix), adiabatic flame temperature (Tad), flame speed (SL), and chemical time (τchem). These correlations clearly indicate the significance of the mixture diffusivity, heat content, and flame propagation speed upon blowout characteristics across a wide fuel spectrum. Two basic models of flame stabilization discussed in the literature were evaluated — a well-stirred reactor based approach that considers the ratio of chemical and flow times, and a propagative mechanism that considers the ratio of flame and flow speed. Both mechanisms were able to correlate some, but not all segments of the data set.

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Raporty organizacyjne na temat "Flame blowoff"

Lieuwen, Tim, i Jared Kee. PR-592-16208-R01 Effect of Variability in Fuel on Operation and Reliability of Gas Turbine. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzec 2017. http://dx.doi.org/10.55274/r0011023.

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Pipeline natural gas, while dominantly composed of methane, also contains various amounts of diluents, hydrogen, and hydrocarbons. The objective of this report is to describe how variations in fuel composition influence gas turbine emissions, operability, and operational range (turndown). A key point of this report is that these fuel composition sensitivities are not described by a single parameter, such as Wobbe index, but by different parameters depending upon the specific issue. For example, the autoignition time is an important parameter influencing autoignition risk, while flame speed has important influences on combustion instability and blowoff risk. This report explains these sensitivities, as well as approaches for identifying and mitigating operational risk. This report has a related webinar.

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Lyons, Kevin M. Stabilization and Blowout of Gaseous- and Spray-Jet Flames. Fort Belvoir, VA: Defense Technical Information Center, sierpień 2004. http://dx.doi.org/10.21236/ada426409.

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Huelskamp, Bethany C., Barry V. Kiel, Amy C. Lynch, Stanislav Kostka, Ponnuthurai Gokulakrishnan i Michael S. Klassen. Improved Correlation for Blowout of Bluff-body Stabilized Flames (Preprint). Fort Belvoir, VA: Defense Technical Information Center, kwiecień 2012. http://dx.doi.org/10.21236/ada560506.

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Lyons, Kevin M. Flame Propagation and Blowout in Hydrocarbon Jets: Experiments to Understand the Stability and Structure. Fort Belvoir, VA: Defense Technical Information Center, lipiec 2012. http://dx.doi.org/10.21236/ada577412.

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