High-speed laser diagnostics for the study of flame dynamics in a lean premixed gas turbine model combustor

Boxx, Isaac; Arndt, Christoph M.; Carter, Campbell D.; Meier, Wolfgang

doi:10.1007/s00348-010-1022-x

Cited by 77 publications

(57 citation statements)

References 37 publications

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“…These studies also show that the flame's heat release changes the density and velocity fields, altering the hydrodynamic stability of the flow, in many cases suppressing the m = 1 instability and hence the precessing vortex core. This concurs with experiments and large-eddy simulations (LES) of swirling premixed lifted flames (Giauque et al 2005;Roux et al 2005;Boxx et al 2012).…”

supporting

confidence: 84%

Self-sustained hydrodynamic oscillations in lifted jet diffusion flames: origin and control

2015

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We use direct numerical simulation (DNS) of the Navier-Stokes equations in the low-Mach-number limit to investigate the hydrodynamic instability of a lifted jet diffusion flame. We obtain steady solutions for flames using a finite rate reaction chemistry, and perform a linear global stability analysis around these steady flames. We calculate the direct and adjoint global modes and use these to identify the regions of the flow that are responsible for causing oscillations in lifted jet diffusion flames, and to identify how passive control strategies might be used to control these oscillations. We also apply a local stability analysis to identify the instability mechanisms that are active. We find that two axisymmetric modes are responsible for the oscillations. The first is a high-frequency mode with wavemaker in the jet shear layer in the premixing zone. The second is a low-frequency mode with wavemaker in the outer part of the shear layer in the flame. We find that both of these modes are most sensitive to feedback involving perturbations to the density and axial momentum. Using the local stability analysis, we find that the high-frequency mode is caused by a resonant mode in the premixing region, and that the low-frequency mode is caused by a region of local absolute instability in the flame, not by the interaction between resonant modes, as proposed in Nichols et al. (Phys. Fluids, vol. 21, 2009, article 015110). Our linear analysis shows that passive control of the low-frequency mode may be feasible because regions up to three diameters away from the fuel jet are moderately sensitive to steady control forces.

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confidence: 84%

Self-sustained hydrodynamic oscillations in lifted jet diffusion flames: origin and control

2015

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“…This frequency could be due to the existence of periodic flow structure but requires further detailed analysis of the flow field, and hence will be investigated in a later study. The trends presented in Figure 3 are similar to what Boxx et al (2012) have reported in investigation of flames with and without strong thermo-acoustic pulsations.…”

Section: Flame Characterizationsupporting

confidence: 88%

Phase Resolved Analysis of Flame Structure in Lean Premixed Swirl Flames of a Fuel Staged Gas Turbine Model Combustor

Gounder

Boxx

Kutne

et al. 2014

Combustion Science and Technology

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A scaled model of a gas turbine (GT) burner with coaxially mounted swirlers has been used to study the effects of fuel staging on the behavior of lean premixed methane air flames. Lean flames are known to be susceptible to instabilities that can lead to unsteady operation, flame extinction, and thermo-acoustic oscillations. High speed (10 kHz) laser and optical diagnostic techniques have been used to investigate the fuel staging effect on the mechanisms involved in such instabilities. Methane air flames at atmospheric pressure have been investigated at a constant thermal power of 58 kW. The global equivalence ratio was kept constant, while the fuel staging was varied. The bulk flow velocity at the exit plane was kept constant at 20 m/s. Simultaneous high speed OH PLIF, OH * CL, and acoustic measurements were performed at kHz repetition rate to characterize the flames and determine the operability limits of the combustor. The characterization measurements reveal significant changes in flame shape for various staging ratios as well as onset of self-excited thermo-acoustics in flames with more than 55% fuel injection in the outer swirler. The phase resolved analysis of the OH * CL revealed pulsation in the heat release due to acoustics in flames with higher percentage of fuel in the outer swirler. Comparison of the pressure oscillation in the combustion chamber with the heat release yielded a clear picture regarding the feedback mechanism that sustains the self-excited thermo-acoustic pulsations. The variation of local equivalence ratio of the mixture seems to be the driving force that initiates the onset of acoustics pulsations.

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“…Similar suppression effect of combustion on PVC instability was observed in some research [42,43]. More studies indicated that the PVC occurrence and amplitude under the combustion conditions strongly depended on the operating conditions, e.g., equivalence ratios and the confinement levels [44,45]. The effects of equivalence ratio and fuel composition were examined in the current study.…”

Section: Identification Of Precessing Vortex Core By Pod Analysismentioning

confidence: 64%

Experimental Study of Hydrogen Addition Effects on a Swirl-Stabilized Methane-Air Flame

Tong

Klingmann

et al. 2017

Energies

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Abstract:The effects of H 2 addition on a premixed methane-air flame was studied experimentally with a swirl-stabilized gas turbine model combustor. Experiments with 0%, 25%, and 50% H 2 molar fraction in the fuel mixture were conducted under atmospheric pressure. The primary objectives are to study the impacts of H 2 addition on flame lean blowout (LBO) limits, flame shapes and anchored locations, flow field characteristics, precessing vortex core (PVC) instability, as well as the CO emission performance. The flame LBO limits were identified by gradually reducing the equivalence ratio until the condition where the flame physically disappeared. The time-averaged CH chemiluminescence was used to reveal the characteristics of flame stabilization, e.g., flame structure and stabilized locations. In addition, the inverse Abel transform was applied to the time-averaged CH results so that the distribution of CH signal on the symmetric plane of the flame was obtained. The particle image velocimetry (PIV) was used to detect the characteristics of the flow field with a frequency of 2 kHz. The snapshot method of POD (proper orthogonal decomposition) and fast Fourier transform (FFT) were adopted to capture the most prominent coherent structures in the turbulent flow field. CO emission was monitored with an exhaust probe that was installed close to the combustor exit. The experimental results indicated that the H 2 addition extended the flame LBO limits and the operation range of low CO emission. The influence of H 2 addition on the flame shape, location, and flow field was observed. With the assistance of POD and FFT, the combustion suppression impacts on PVC was found.

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High-speed laser diagnostics for the study of flame dynamics in a lean premixed gas turbine model combustor

Cited by 77 publications

References 37 publications

Self-sustained hydrodynamic oscillations in lifted jet diffusion flames: origin and control

Self-sustained hydrodynamic oscillations in lifted jet diffusion flames: origin and control

Phase Resolved Analysis of Flame Structure in Lean Premixed Swirl Flames of a Fuel Staged Gas Turbine Model Combustor

Experimental Study of Hydrogen Addition Effects on a Swirl-Stabilized Methane-Air Flame

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