Download or read book Flashback Mechanisms in Lean Premixed Gas Turbine Combustion written by Ali Cemal Benim and published by Academic Press. This book was released on 2014-12-10 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blending fuels with hydrogen offers the potential to reduce NOx and CO2 emissions in gas turbines, but doing so introduces potential new problems such as flashback. Flashback can lead to thermal overload and destruction of hardware in the turbine engine, with potentially expensive consequences. The little research on flashback that is available is fragmented. Flashback Mechanisms in Lean Premixed Gas Turbine Combustion by Ali Cemal Benim will address not only the overall issue of the flashback phenomenon, but also the issue of fragmented and incomplete research.

Download or read book Flashback and Blowoff Characteristics of Gas Turbine Swirl Combustor written by Mohammed Abdulsada and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas turbines are extensively used in combined cycle power systems. These form about 20% of global power generating capacity, normally being fired on natural gas, but this is expected in the future to move towards hydrogen enriched gaseous fuels to reduce CO2 emissions. Gas turbine combined cycles can give electrical power generation efficiencies of up to 60%, with the aim of increasing this to 70% in the next 10 to 15 years, whilst at the same time substantially reducing emissions of contaminants such as NOx. The gas turbine combustor is an essential and critical component here. These are universally stabilized with swirl flows, which give very wide blowoff limits, and with appropriate modification can be adjusted to give very low NOx and other emission. Lean premixed combustion is commonly used at pressures between 15 to 30 bar, these even out hot spots and minimise formation of thermal NOx. Problems arise because improving materials technology/improved cooling techniques allow higher turbine inlet temperatures, hence higher efficiencies, but with the drawback of potentially higher emissions and stability problems. This PhD study has widely investigated and analysed two different kinds of gas turbine swirl burners. The research has included experimental investigation and computational simulation. Mainly, the flashback and blowoff limits have been comprehensively analysed to investigate their effect upon swirl burner operation. The study was extended by using different gas mixtures, including either pure gas or a combination of more than one gas like natural gas, methane, hydrogen and carbon dioxide. The first combustor is a 100 kW tangential swirl combustor made of stainless steel that has been experimentally and theoretically analysed to study and mitigate the effect of flashback phenomena. The use of a central fuel injector, cylindrical confinement and exhaust sleeve are shown to give large benefits in terms of flashback resistance and acts to reduce and sometimes eliminate any coherent structures which may be located along the axis of symmetry. The Critical Boundary Velocity Gradient is used for characterisation of flashback, both via the original Lewis and von Elbe formula and via new analysis using CFD and investigation of boundary layer conditions just in front of the flame front. Conclusions are drawn as to mitigation technologies. It is recognized how isothermal conditions produce strong Precessing Vortex Cores that are fundamental in producing the ii final flow field, whilst the Central Recirculation Zones are dependent on pressure decay ratio inside the combustion chamber. Combustion conditions showed the high similarity between experiments and simulation. Flashback was demonstrated to be a factor highly related to the strength of the Central Recirculation Zone for those cases where a Combustion Induced Vortex Breakdown was allowed to enter the swirl chamber, whilst cases where a bluff body impeded its passage showed a considerable improvement to the resistance of the phenomenon. The use of nozzle constrictions also reduced flashback at high Reynolds number (Re). All these results were intended to contribute to better designs of future combustors. The second piece of work of this PhD research included comprehensive experimental work using a generic swirl burner (with three different blade inserts to give different swirl numbers) and has been used to examine the phenomena of flashback and blowoff in the swirl burner in the context of lean premixed combustion. Cylindrical and conical confinements have been set up and assembled with the original design of the generic swirl combustor. In addition to that, multi-fuel blends used during the experimental work include pure methane, pure hydrogen, hydrogen / methane mixture, carbon dioxide/ methane mixture and coke oven gas. The above investigational analysis has proved the flashback limits decrease when swirl numbers decrease for the fuel blends that contain 30% or less hydrogen. Confinements would improve the flashback limit as well. Blowoff limits improve with a lower swirl number and it is easier to recognise the gradual extinction of the flame under blowoff conditions. The use of exhaust confinement has created a considerable improvement in blowoff. Hydrogen enriched fuels can improve the blowoff limit in terms of increasing heat release, which is higher than heat release with natural gas. However, the confinements complicate the flashback, especially when the fuel contains a high percentage of hydrogen. The flashback propensity of the hydrogen/methane blends becomes quite strong. The most important features in gas turbines is the possibility of using different kinds of fuel. This matter has been discussed extensively in this project. By matching flashback/blowoff limits, it has been found that for fuels containing up to 30% of hydrogen, the designer would be able to switch the same gas turbine combustor to multifuels whilst producing the same power output.

Download or read book Effect of Swirl Cup on Characteristics of Fuel Spray in Gas Turbine Combustors written by Jong-Hoon Park and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Establishing Flashback and Blowout Limits in a Commercial Lean Premixed Combustor Operating on Synthesis Gas written by David Page and published by . This book was released on 2012 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flashback and lean blowout are operability issues that must be addressed for successful operation of stationary gas turbines. The present work focuses on flashback and lean blowout of premixed jet flames in a combustor from a commercially available gas turbine operating on synthesis gas of various compositions. The issues of flashback and lean blowout are exacerbated when operating on fuels with high hydrogen content due to the increased reactivity of hydrogen, thus increasing the propensity for flashback. Operating margins for mixtures of natural gas (NG) and carbon monoxide (CO) in hydrogen (H2) are reported. The results demonstrate less stability near lean blowout for mixtures of H2/NG than for H2/CO. Increasing H2 concentration extends the lean operating limit from [phi] = 0.63 to [phi] = 0.29 for H2/NG and [phi] = 0.42 to [phi] = 0.29 for H2/CO. Modeling of the experimental data using a perfectly stirred reactor indicates that the Damköhler number well characterizes the effects of the addition of H2 to NG on the lean blowout limits. In addition, key factors dominating flashback behavior are identified and included in a predictive methodology. A response surface, developed from a turbulent flame speed database, is used to create a flashback propensity index as a design tool for quantifying flashback based upon experimental data from the combustor. Furthermore, the Damköhler number is explored as an index for predicting flashback and was determined to be effective at capturing the effect of pressure, making it able to link data taken at atmospheric conditions to expected engine results.

Download or read book Lateral jet injection into typical combustor flowfields written by David G. Lilley and published by DIANE Publishing. This book was released on 1986 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Combustion Induced Vortex Breakdown on Flashback Limits of Syngas Fueled Gas Turbine Combustors written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbine combustors of advanced power systems have goals to achieve very low pollutants emissions, fuel variability, and fuel flexibility. Future generation gas turbine combustors should tolerate fuel compositions ranging from natural gas to a broad range of syngas without sacrificing operational advantages and low emission characteristics. Additionally, current designs of advanced turbine combustors use various degrees of swirl and lean premixing for stabilizing flames and controlling high temperature NOx formation zones. However, issues of fuel variability and NOx control through premixing also bring a number of concerns, especially combustor flashback and flame blowout. Flashback is a combustion condition at which the flame propagates upstream against the gas stream into the burner tube. Flashback is a critical issue for premixed combustor designs, because it not only causes serious hardware damages but also increases pollutant emissions. In swirl stabilized lean premixed turbine combustors onset of flashback may occur due to (i) boundary layer flame propagation (critical velocity gradient), (ii) turbulent flame propagation in core flow, (iii) combustion instabilities, and (iv) upstream flame propagation induced by combustion induced vortex breakdown (CIVB). Flashback due to first two foregoing mechanisms is a topic of classical interest and has been studied extensively. Generally, analytical theories and experimental determinations of laminar and turbulent burning velocities model these mechanisms with sufficient precision for design usages. However, the swirling flow complicates the flashback processes in premixed combustions and the first two mechanisms inadequately describe the flashback propensity of most practical combustor designs. The presence of hydrogen in syngas significantly increases the potential for flashback. Due to high laminar burning velocity and low lean flammability limit, hydrogen tends to shift the combustor operating conditions towards flashback regime. Even a small amount of hydrogen in a fuel blend triggers the onset of flashback by altering the kinetics and thermophysical characteristics of the mixture. Additionally, the presence of hydrogen in the fuel mixture modifies the response of the flame to the global effects of stretch and preferential diffusion. Despite its immense importance in fuel flexible combustor design, little is known about the magnitude of fuel effects on CIVB induced flashback mechanism. Hence, this project investigates the effects of syngas compositions on flashback resulting from combustion induced vortex breakdown. The project uses controlled experiments and parametric modeling to understand the velocity field and flame interaction leading to CIVB driven flashback.

Download or read book Combustion Characteristics of Gaseous Flames in a Gas Turbine Combustor written by A. M. Attya and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Film Vaporization Principle for Gas Turbine Combustors written by Gunter W. Maybach and published by . This book was released on 1959 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Swirl Stabilized Combustion and Its Application to Gas Turbine Combustors written by N. Syred and published by . This book was released on 1973 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Non premixed Swirl Stabilized Flames of Gaseous and Liquid Fuels in a Gas Turbine Model Combustor written by Sandipan Chatterjee and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent non-premixed swirl-stabilized flames of gaseous and liquid fuels were investigated experimentally in an optically-accessible gas turbine model combustor. Propane/air and ethylene/air flames were operated at three global fuel-air equivalence ratios. Spray flames of liquid n-heptane fuel were stabilized at six global fuel-air equivalence ratios. The velocity, reaction zone structure and soot measurements were performed using stereoscopic particle image velocimetry, planar laser induced fluorescence of OH radicals and laser induced incandescence, respectively. In all the experimented test flow cases, the time-averaged velocity data show the presence of two large recirculation zones, separated by a zone of high velocity swirled inflow. The inner recirculation zone, which surrounds the combustor axis, shows high turbulence intensities. In gaseous fuel flames, the inner recirculation zone also contained most of the combustion-generated soot concentration of the flow field of gaseous fuel flames. The flow field regions exterior to the inner recirculation zone showed negligible soot values mainly due to the soot oxidation caused by the high intensity turbulence as well as strong OH intensity near the recirculation zone boundary. The time-averaged soot values showed strong sensitivity to changes in the air flow rates. The changes in the air flow rate mostly increased the soot intermittency, while the instantaneous soot concentrations stayed nearly constant. Intensified turbulence as well as shortening of flow time for soot chemistry are speculated to be the reasons for the high sensitivity of soot values to air flow rates. Further, in n-heptane/air flames, the velocity data showed a region of high velocity fuel droplets, positioned in-between two large recirculation zones. The boundary of the inner recirculation zones showed the heat release events, thereby leading to high OH counts. The OH fluorescence profiles showed the major role played by the recirculation zones in fuel droplet evaporation, forming the evaporated fuel-air reactant mixture, and subsequently, igniting the reactant mixture in the presence of hot combustion products and active radicals.

Download or read book Flow Characteristics of an Elliptic Swirl stabilized Gas Turbine Burner written by G. H. G. Anning and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Swirl on Fuel Variability in Gas Turbine Combustors written by Praveen P. Reddy and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Swirling Effect on Flow Pattern Inside a Gas Turbine Combustor written by Yehia A.Eldrainy and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer and Flow Characteristics Inside a Gas Turbine Combustor written by Yap-Sheng Goh and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Combustion in Advanced Gas Turbine Systems written by Ian Edward Smith and published by . This book was released on 1968 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Swirl Stabilised Gas Turbine Combustion written by N. T. Ahmad and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flame Behaviour in an Acoustically Forced Gas Turbine Combustor written by Adam Ruggles and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A swirl stabilised dump combustor capable of imposing flow perturbationscreating combustion instabilities has been designed and commissioned. Thecapability of supplying different fuel mixtures (methane hydrogen blends) hasbeen incorporated. Additional capability is the facility to preheat the combustionair prior to chamber entry and to be able to introduce dilution air into thechamber. The chamber itself is of fused silica quartz to allow non-intrusiveoptical diagnostics. High speed CH* Chemiluminescence has been performed to qualitativecharacterise the unstable heat release rate of pure methane and methanehydrogen blended flames to allow analysis of the mean deconvoluted flamestructure. High speed Stereoscopic Particle Imaging Velocimetry (SPIV) has beenused to acquire the flow field throughout the chamber and focusing upon theAnnulus entry. These diagnostics have been phase locked to the imposedperturbation. A selection of conditions is presented with three different perturbationfrequencies within the low frequency range. These reveal vastly differentreacting and flow field structures. The difference of structures is attributed tobehaviour of the IRZ (Internal Recirculation Zone) and CRZ (CornerRecirculation Zone) in altering the flame shape. All conditions exhibited theaxisymmetric/bubble vortex breakdown mechanism responsible for stabilisation. Both single cell and double cell structures were observed in the mean flow fieldvector maps. The mechanism of oscillating heat release rate is attributed tooscillations of flame surface area. Profiles of integrated heat release rate andflame exhibit the same profile shape and behaviour correlating very well. Theinclusion of hydrogen had no quantifiable impact upon the mean reacting or flowfield structures using the current diagnostics. Investigation into the nature of theturbulence of the shear layers close to the annulus is presented for threeperturbation frequencies. This highlighted periodic structures within theturbulence corresponding to the imposed perturbation frequency. It was foundthat excitation of both shear layers for all turbulent components was not alwaystrue and depended upon the perturbation frequency and flow structure close tothe annulus. Two oppositely rotating vorticity structures were revealed attachedto the outer and inner circumference of the annulus. These structures protrudedinto the chamber and spread radially. Frequency analysis of these two structuresrevealed both were oscillating at the perturbation frequency indicating vorticityshedding. The mean vorticity structures are shown to be influenced also by thebehaviour of the recirculation zones.