Дисертації з теми "Flame blowoff"
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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.
Повний текст джерелаCataloged 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.
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.
Повний текст джерелаBinti, 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.
Повний текст джерелаQC 20130411
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.
Повний текст джерелаBompelly, Ravi K. "Lean blowout and its robust sensing in swirl combustors." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47529.
Повний текст джерелаNair, Suraj. "Acoustic Characterization of Flame Blowout Phenomenon." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10413.
Повний текст джерелаZhang, Qingguo. "Lean blowoff characteristics of swirling H2/CO/CH4 Flames." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22641.
Повний текст джерелаHusain, 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.
Повний текст джерелаMoore, 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/.
Повний текст джерелаPrakash, Shashvat. "Lean Blowout Mitigation in Swirl Stabilized Premixed Flames." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16159.
Повний текст джерелаSingh, Bhupinder. "Flame blowout and pollutant emissions in vitiated combustion of conventional and bio-derived fuels." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024935.
Повний текст джерелаBranco, Natashe Nicoli. "Estudo analítico do mecanismo de blowout de chamas de difusão turbulenta." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3150/tde-04112014-102047/.
Повний текст джерелаThe study of flame stability is very important to the design of burners used in industrial ovens and furnaces, combustion chambers of gas turbines and flares; and fuel substitution in burners. There is a range of conditions (for example gas velocity at the nozzle exit and jet fuel concentration in the gas mixture) at which stable combustion can be maintained, being limited by two phenomena called liftoff and blowout. Lift-off is the detachment of the flame from the fuel nozzle, and blowout its detachment and extinction. Operating conditions close to stability limits should be avoided for security reasons. Many theories have been published to describe the blowout and lifted characteristics of turbulent jet diffusion flames. This document presents some theories, as well as the assumptions and physical processes considered responsible for these phenomena (liftoff and blowout). Correlations for predicting the blowout velocity and experimental results available in the literature are also shown. A new correlation is proposed, which is based on large-scale motions observed in turbulent jets and the dimensionless Damköhler number (ratio of the characteristic chemical reaction time and the time associated with the mixing of reentrained hot products into fresh reactants). Comparisons between the predictions of the proposed correlation with experimental results and predictions of other correlations available in the literature were performed for different fuels and nozzle diameters. The proposed correlation showed good agreement with the experimental results. The analyses developed in this work allow us to conclude that the blowout velocity of the turbulent diffusion flame depends on the fuel properties, characteristics of the nozzle, the environmental conditions and the Damköhler number.
WENG, FANG-BO, and 翁芳柏. "Diffusion flame stabilization and blowoff over a porous cylinder." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/08369041593311673486.
Повний текст джерелаJang, Yung-Li, and 張永利. "AN EXPERIMENTAL INVESTIGATION OF THE BLOWOUT PROCESS OF A JET FLAME." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/15840871021730279290.
Повний текст джерела國立成功大學
航空太空工程學系
88
An experimental study is performed in order to investigate the roles of triple flames and flamefront instabilities in the blowout transient process. Two dimensional laser LIPF(laser induced predissociative fluorescence) OH and PIV (particle image velocimetry) diagnostic techniques are used for measurements of instantaneous flame structure and velocity data. Initial conditions are controlled by external acoustic excitation and beginning the blowout transien process. The blowout transient process can be divided into four regions: the pulsating, onset of receding, receding and extinction regions, according to the dynamic characteristics of the flame. In the pulsating region, the flame base is basically pulsating at two specific heights with jittering. Flamefront instability may play a role in leading the onset of blowout process. Both LIPF OH image and PIV results show the possible existence of the triple (or edge) flame structures in the flame base for cases in the pulsating and onset regions. High strain rate, higher than the extinction strain rate, in the flame base in the onset region should be considered as a prominent factor for the blowout process. Moreover, according to the instability in the pulsating and onset regions, we predicts the value of Lewis number would decrease from more than one to less than one. As to the experiment apparatus, PIV system in the experiment can supply two dimensional instantaneous velocity data, and it has the advantages of the low cost, so it deserves to be popularized.
XUE, ZHI-HUI, and 薛智輝. "A study of blowout mechanisms of jet diffusion flames." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/70343263363422100360.
Повний текст джерелаWu, Chih-Yung, and 吳志勇. "Characterization of the Behavior and Instablility of Transient Blowout Process of Jet Flames." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/40783323004212299109.
Повний текст джерела國立成功大學
航空太空工程學系碩博士班
91
Characteristics of the blowout limits, instability phenomenon, and transient blowout process of jet flames were investigated experimentally. Based upon qualitative observations and phenomenological arguments, an extended model of the transient turbulent blowout process of jet flames was proposed to explain the characteristic behavior of the blowout phenomenon. Quantitative experimental data were used to further examine and verify the proposed model of the transient blowout process of jet flames. In this work, an extended database of the global blowout limits, blowout velocities of various inert-diluted methane, propane, and hydrogen jet flames were constructed and studied experimentally. Helium, argon, nitrogen, and carbon dioxide were used as the diluents to generate different initial properties. Extension of the widely-applied premixed and large-scale blowout models by Kalghatgi and Broadwell, respectively, was carefully examined using inert-diluted methane, propane, and hydrogen jet flames. Results showed that among the models the obtained blowout-velocity estimation based on the premixed model of Kalghatgi is more reliable in the extended dilution region, while that based on the large-scale model of Broadwell needs to take Reynolds number effect into account so that a better prediction of blowout velocity can be made. The trajectory of the flame base propagation in the transient blowout process was evaluated using digital image processing and the specific blowout behaviors was also categorized and analyzed statistically. In addition, the fuel/air mixing and flow characteristics in the upstream region of the flame base during the blowout process were also explored using Rayleigh Scattering and LIPF-OH imaging techniques. In addition, PIV was used to obtain velocity distributions near the lifted flame base. A mechanism related to blowout process model was constructed and proposed to explain the instability behavior and evolution of different stages of the transient blowout process. The accurate blowout-limit estimation and comprehension of the instability behavior of the jet flames are of significant importance to practical combustion applications and advanced combustor design.