Studies of Lean Blowout in a Step Swirl Combustor

Durbin, M. D.; Ballal, D. R.

doi:10.1115/94-gt-216

Cited by 5 publications

(4 citation statements)

References 5 publications

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“…As mentioned above, Plee and Mellor [24] and Leonard and Mellor [25] found that slowly vaporizing droplets can have beneficial influence on lean blowout limits of spray flames. More stable combustion due to less uniform mixing was also observed by Durbin and Ballal [57], albeit using gaseous propane fuel in a swirl-stabilized combustor. The improved stability was explained by locally richer mixture regions.…”

Section: Discussionsupporting

confidence: 59%

Influence of Single-Component Fuels on Gas-Turbine Model Combustor Lean Blowout

Grohmann

Rauch

Kathrotia

et al. 2018

Journal of Propulsion and Power

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The influence of selected single-component hydrocarbons on lean blowout behavior of swirl-stabilized spray flames was investigated. Additional information on the spray characteristics was collected by Phase Doppler Interferometry (PDI) and Mie scattering measurements. The measurements were accomplished in a gas turbine model combustor under atmospheric pressure and at two different air preheat temperatures.The combustor featured a dual-swirl geometry and a prefilming airblast atomizer. The combustion chamber provided good optical access and yielded well-defined boundary conditions. Three single-component hydrocarbons were chosen: one short and one long linear alkane (n-hexane and n-dodecane) and one branched alkane (iso-octane).Kerosene Jet A-1 was used as a reference. Results show noticeable differences in the lean blowout limits of the various fuels, at comparable flow conditions. By using the results of the measurements, of additional modelling and of an assessment of the fuel properties it was concluded that fuel differences in lean blowout in this combustor can be due to differences in the physical properties as well as in the chemical properties. \phi = global equivalence ratio (-) P th = thermal power (W) \rho = density ( \mathrm{ \mathrm{ /\mathrm{ 3 ) Re = Reynolds number (-) \sigma = surface tension ( \mathrm{ /\mathrm{ ) S = geometrical swirl number (-) t e = total evaporation time (s) T = temperature (K) u, v, w = velocities in reference coordinate system ( \mathrm{ /\mathrm{ ) x, y, z = reference coordinate system (m) I. IntroductionProduction pathways for alternative aviation fuels offer the possibility to modify the chemical composition of the final product in order to improve physical and chemical properties for optimized combustion performance. Depending on feedstock (e.g. coal, natural gas or biomass) and process parameters, alternative fuels can contain hydrocarbons of significantly different types and chain lengths [1,2]. However, the influence of the chemical composition of the fuel on combustion performance is not fully understood [3].Four main processes govern the combustion of liquid fuels in gas turbine combustors: atomization, vaporization, turbulent mixing and chemical reaction. These processes happen simultane-

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Section: Discussionsupporting

confidence: 59%

Influence of Single-Component Fuels on Gas-Turbine Model Combustor Lean Blowout

Grohmann

Rauch

Kathrotia

et al. 2018

Journal of Propulsion and Power

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“…The stabilization mechanisms used to hold flames in high velocity flows are based on varying several parameters such as flow rate, flow geometry, swirl, heat release rates, fuel/air composition, and temperature. [7][8][9][10][11][12][13][14][15][16] Most of these efforts have focused on understanding the stabilization mechanisms and improving them; little attention has been given to understanding the dynamics of loss of stabilization.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Extinction Events Near Blowout in Swirl Dump Combustors

Muruganandam¹,

Seitzman²

2005

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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This work examines the evolution of the lean blowout (LBO) process in a swirl-dumpstabilized combustor with center body. Previous studies identified extinction-reignition events as precursors to LBO. These events are investigated in greater detail using simultaneous fiber optic-based chemiluminescence sensors and high speed imaging in an atmospheric pressure, premixed methane-air combustor. It is found that the flame, which is stabilized above the center body, at first partially detaches due to turbulent fluctuations. This detached region moves around the center body due to the swirl and the feedback mechanism of the inner recirculation zone. As the LBO limit is approached, the weaker flame detaches more often and over a larger extent of the center body. When the flame is detached beyond a certain extent, enough cold packets of unburned gases move around the inner recirculation zone to reduce the feedback needed for stabilization and the flame detaches completely from the center body. This is the source of the extinction events previously noted in the sensor data. The flow field responds to the decreased heat release with a larger recirculation zone and stronger swirl. The flame shape and flame stabilization change to a tornado mode. In this mode, the flame is stabilized much farther downstream of the combustor inlet, but an occasional packet of burning gases is convected back to the inlet. If this flame packet is sufficiently strong, the original flow field and flame shape are restored. This return of the original stable flame mode is the onset of the reignition events found in the sensor data. Several occurrences of these events in time gradually weaken the combustion process and eventually the convected flame packets are not strong enough to restabilize the combustor, i.e., the combustor blows out. This understanding of the process of flame stabilization loss provides the necessary insight for improved design and analysis of LBO sensors systems.

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“…Flame stability has been studied close to blowout by a number of researchers. [15][16][17][18][19][20][21][22][23] The focus was mainly on understanding the mechanisms that influence the loss of stability. This is usually attributed to high heat loss and strain rates.…”

Section: Introductionmentioning

confidence: 99%

Chemiluminescence Based Sensors for Turbine Engines

Muruganandam¹,

Kim²,

Olsen³

et al. 2003

39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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This work focuses on the use of naturally occurring optical emissions, specifically chemiluminescence, for sensing applications in active control and health monitoring of combustors. First, monitoring local equivalence ratio (φ), at the reaction zone, has been demonstrated using the ratio of CH to OH chemiluminescence. This ratio (CH*/OH*) increases monotonically with equivalence ratio, and the dependence on equivalence ratio has been shown to be a universal function for combustor configurations ranging from unconfined jet flames to swirl and dump stabilized combustors. There is essentially no difference between the CH*/OH* ratio for methane and natural (city) gas, but the ratio has a lower sensitivity to φ for n-heptane compared to methane or natural gas. The ratio was found to increase almost linearly with pressure for natural gas/methane combustion above 3 atm. Second, chemiluminescence emission from the combustor was used to detect precursor events to blowout, using a robust thresholding method. This method was shown to be successful in jet flames and swirl/dump stabilized combustors using premixed methane/air and nonpremixed Jet-A/air. This method gives the kind of information on proximity to blowout that can be used by an active control system to prevent lean blowout in low NO x turbine engine combustors.

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Studies of Lean Blowout in a Step Swirl Combustor

Cited by 5 publications

References 5 publications

Influence of Single-Component Fuels on Gas-Turbine Model Combustor Lean Blowout

Influence of Single-Component Fuels on Gas-Turbine Model Combustor Lean Blowout

Characterization of Extinction Events Near Blowout in Swirl Dump Combustors

Chemiluminescence Based Sensors for Turbine Engines

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