Effects of Back-Pressure in a Lean Blowout Research Combustor

Sturgess, G. J.; Heneghan, S. P.; Vangsness, M. D.; Ballal, D. R.; Lesmerises, A. L.; Shouse, Dale T.

doi:10.1115/1.2906735

Cited by 18 publications

(4 citation statements)

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“…LBO data were collected by maintaining a constant airflow rate, heating the combustor to a near steady-state temperature at stoichiometric fuel-air ratio, and then gradually decreasing the fuel flow rate until blowout occurred. This is a procedure similar to that adopted by Sturgess et al (1991). The flame length was defined as the distance from the nozzle exit to the flame tip and measured by taking individual color snap-shots of the combustion process, enlarging these photographs, and then carefully plotting the luminous boundary of the flame front.…”

Section: Error Analysismentioning

confidence: 99%

Studies of Lean Blowout in a Step Swirl Combustor

Durbin

Ballal

1994

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

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The design requirements of a modem gas turbine combustor are increasingly dictated by wide stability limits, short flame length, and uniform mixing. To achieve the best trade-off between the above three factors, flame characteristics (length, shape, mixedness), lean blowout (LBO), and optimum combustor configuration should be investigated over a wide range of inner and outer air velocities, inner and outer vane angles, and co- vs. counter-swirl arrangements. Such an investigation was performed in a step swirl combustor (SSC) designed to simulate the fuel-air mixing pattern in a gas turbine combustor dome fitted with an airblast atomizer. It was found that an increase in the outer vane angle and a decrease in inner air velocity decreased the flame length. LBO was improved when outer flow swirl intensity was increased. An optimum hardware and velocity configuration for the SSC was found for inner swirl = 45°, outer swirl = 60°, co-swirl direction, and inner air velocity = outer air velocity = 16 m/s. This optimum SSC configuration yielded: (i) low values of LBO, (ii) short flame length, (iii) uniformly mixed stable flame, and (iv) little or no variation in these characteristics over the range of operation of SSC. Finally, the co- vs. counter-swirl arrangements and the operation of the optimized combustor configuration were discussed.

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Section: Error Analysismentioning

confidence: 99%

Studies of Lean Blowout in a Step Swirl Combustor

Durbin

Ballal

1994

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

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“…Based on detection of LBO precursors using OH* chemiluminescence, Thiruchengode et al extended the LBO limit by modifying the fuel fraction injected into the flame stabilization zone 10 . Gutmark et al extended the LBO limit of a premixed dump combustor by generating small-scale vortices using shear layer forcing 15 , whereas Sturgess et al found that the LBO limit can be extended by exit blockage 16 . Durbin and Ballal observed that the LBO limit was reduced by increasing the outer swirl intensity if the inner swirl is stronger than the outer swirl 17 .…”

mentioning

confidence: 99%

Sensing and Control of Combustion Instabilities in Swirl-Stabilized Combustors Using Diode-Laser Absorption

Li¹,

Zhou²,

Jeffries³

et al. 2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Thermoacoustic instability and lean blowout (LBO) are monitored in propane/air flames in a swirl-stabilized combustor using a novel tunable diode laser (TDL) sensor for gas temperature using wavelength-scanned laser absorption of two neighboring water vapor transitions near 1.4 μm. Although the gas composition and temperature are not uniform along the sensor line-of-sight, temperature oscillations and fluctuations are clearly identified in the FFT power spectra of the time-resolved data. Detailed experiments are conducted to optimize the position of the sensor line-of-sight in the flame for thermoacoustic instability and LBO sensing. The output of the sensor is used to suppress the thermoacoustic oscillations in a phase-delay feedback control system, and acoustic modulation of the intake air flow suppresses the temperature oscillations by more than 7dB. The low-frequency temperature fluctuations measured by the TDL sensor increase sharply as the flame approaches LBO. The intensity of these low-frequency fluctuations is used to detect the proximity to LBO, and can be used as a control variable for active LBO suppression without knowing the LBO fuel/air ratio limit. The TDL sensor results are compared with traditional pressure and emission sensors, and the TDL sensor is found to offer several advantages including better spatial resolution and insensitivity to background acoustic noise and flame emissions.

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“…LBO scaling as a function of combustion parameters (incoming flow velocity, equivalence ratio, pressure, temperature, and fuel type) have been reported for specific combustor configurations [9][10][11][12][13][14], and active or passive control strategies to extend LBO have been explored [8,[15][16][17][18]. Several LBO mechanisms have been proposed and include balance between the rate of entrainment of reactants into the recirculation zone and the rate of buming [19], energy balance between heat supplied by the hot recirculating flow to the fresh gases and that released by reaction [20][21][22][23], balance between contact time between the combustible mixture and hot gases in the shear layer and chemical ignition time [20,[24][25][26], and mecha-nisms related to local extinction by excessive flame stretch with a flamelet based description [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study of Lean Blowout With Hydrogen-Enriched Fuels

Zhu

Acharya

2012

Journal of Engineering for Gas Turbines and Power

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premixed combustion is widely used to achieve a better compromise between nitric oxide (NOx) emissions and combustion efficiency (related to CO levels). However, com-bustor operation near the lean blowout (LBO) limit can render the flame unstable and lead to oscillations, flashback, or extinction, thereby limiting the potential range of lean combustion application. Recent interest in integrated gasification combined cycle plants and syngas combustion requires an improved understanding of the role of hydrogen on the combustion process. Therefore, in the present study, combustion of pure methane and blended methane-hydrogen with hydrogen-levels up to 80 % by volume has been con-ducted in a swirl stabilized premixed combustor. Particle imaging velocimetry (PIV) and OH * chemiluminescence imaging have been used in this study. Results show that there is a single-ringed structure of internal recirculation zone (IRZ) in the non-reacting flow, while in the reacting flows, there is a more complex flow pattern with a two-celled IRZ structure in which the axial velocity near the center-axis is oriented downstream. As the equivalence ratio decreases, the width of IRZ decreases in methane flames while it increases in hydrogen-enriched flames, and the flame shape changes from conical to an elongated columnar shape, especially in hydrogen-enriched flames. There are two differ-ent modes of vortex breakdown observed, spiral mode in methane flames and bubble mode in hydrogen-enriched flames. These differences between the behavior of the methane-only and hydrogen-enriched flames lead to different behavior of the flame as it approaches the lean blowout. The differences in the mechanisms of LBO in pure methane and hydrogen-enriched premixed flames are examined and explained in the present study. [DOI: 10.1115/1.4004742

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Effects of Back-Pressure in a Lean Blowout Research Combustor

Cited by 18 publications

References 0 publications

Studies of Lean Blowout in a Step Swirl Combustor

Studies of Lean Blowout in a Step Swirl Combustor

Sensing and Control of Combustion Instabilities in Swirl-Stabilized Combustors Using Diode-Laser Absorption

An Experimental Study of Lean Blowout With Hydrogen-Enriched Fuels

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