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

We present an experimental study on the nonlinear dynamics of combustion instability in a lean premixed gas-turbine model combustor with a swirl-stabilized turbulent flame. Intermittent combustion oscillations switching irregularly back and forth between burst and pseudo-periodic oscillations exhibit the deterministic nature of chaos. This is clearly demonstrated by considering two nonlinear forecasting methods: an extended version (Gotoda et al., 2015, “Nonlinear Forecasting of the Generalized Kuramoto-Sivashinsky Equation,” Int. J. Bifurcation Chaos, 25, p. 1530015) of the Sugihara and May algorithm (Sugihara and May, 1990, “Nonlinear Forecasting as a Way of Distinguishing Chaos From Measurement Error in Time Series,” Nature, 344, pp. 734–741) as a local predictor, and a generalized radial basis function (GRBF) network as a global predictor (Gotoda et al., 2012, “Characterization of Complexities in Combustion Instability in a Lean Premixed Gas-Turbine Model Combustor,” Chaos, 22, p. 043128; Gotoda et al., 2016 (unpublished)). The former enables us to extract the short-term predictability and long-term unpredictability of chaos, while the latter can produce surrogate data to test for determinism by a free-running approach. The permutation entropy based on a symbolic sequence approach is estimated for the surrogate data to test for determinism and is also used as an online detector to prevent lean blowout.

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Evaluation of CH4/NOx Reduced Mechanisms Used for Modeling Lean Premixed Turbulent Combustion of Natural Gas

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2818457 ◽

1998 ◽

Vol 120 (4) ◽

pp. 703-712 ◽

Cited By ~ 33

Author(s):

H. P. Mallampalli ◽

T. H. Fletcher ◽

J. Y. Chen

Keyword(s):

High Pressure ◽

Natural Gas ◽

Gas Turbine ◽

Turbulent Combustion ◽

Gas Turbines ◽

Flame Structure ◽

Computational Cost ◽

Premixed Turbulent Combustion ◽

Reduced Mechanism ◽

Lean Premixed

This study has identified useful reduced kinetic schemes that can be used in comprehensive multidimensional gas-turbine combustor models. Reduced mechanisms lessen computational cost and possess the capability to accurately predict the overall flame structure, including gas temperatures and key intermediate species such as CH4, CO, and NOx. In this study, four new global mechanisms with five, six, seven, and nine steps based on the full GRI 2.11 mechanism, were developed and evaluated for their potential to model natural gas chemistry (including NOx chemistry) in gas turbine combustors. These new reduced mechanisms were optimized to model the high pressure and fuel-lean conditions found in gas turbines operating in the lean premixed mode. Based on perfectly stirred reactor (PSR) and premixed code calculations, the five-step reduced mechanism was identified as a promising model that can be used in a multidimensional gas-turbine code for modeling lean-premixed, high-pressure turbulent combustion of natural gas. Predictions of temperature, CO, CH4, and NO from the five-to nine-step reduced mechanisms agree within 5 percent of the predictions from the full kinetic model for 1 < pressure (atm) < 30, and 0.6 < φ < 1.0. If computational costs due to additional global steps are not severe, the newly developed nine step global mechanism, which is a little more accurate and provided the least convergence problems, can be used. Future experimental research in gas turbine combustion will provide more accurate data, which will allow the formulation of better full and reduced mechanisms. Also, improvement in computational approaches and capabilities will allow the use of reduced mechanisms with larger global steps, perhaps full mechanisms.

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F234 Effect of oxygen concentration on combustion instability in a lean premixed gas-turbine model combustor

The Proceedings of the Thermal Engineering Conference ◽

10.1299/jsmeted.2015._f234-1_ ◽

2015 ◽

Vol 2015 (0) ◽

pp. _F234-1_-_F234-2_

Author(s):

Satoshi KINOSHITA ◽

Kenta HAYASHI ◽

Hiroshi GOTODA

Keyword(s):

Gas Turbine ◽

Oxygen Concentration ◽

Combustion Instability ◽

Lean Premixed ◽

Effect Of Oxygen ◽

Turbine Model

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Comparison of the Combustion Characteristics of Liquid Single-Component Fuels in a Gas Turbine Model Combustor

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2016-56177 ◽

2016 ◽

Cited By ~ 5

Author(s):

Jasper Grohmann ◽

William O’Loughlin ◽

Wolfgang Meier ◽

Manfred Aigner

Keyword(s):

Gas Turbine ◽

Alternative Fuels ◽

Numerical Models ◽

Flame Structure ◽

Mie Scattering ◽

Single Component ◽

Liquid Fuels ◽

Reacting Flow ◽

Spray Flames ◽

Turbine Model

Alternative production pathways for liquid fuels provide the opportunity to adjust the chemical composition of the product in order to improve combustion performance. In this study, flame characteristics of selected single-component fuels were investigated to provide a basis for a better understanding of the influence of specific fuel components on the combustion behaviour. The measurements were performed in a redesigned gas turbine model combustor for swirl-stabilised spray flames under atmospheric pressure. The combustor features a dual-swirl geometry and a prefilming airblast atomiser. The combustion chamber provides good optical access and yields well-defined boundary conditions. As part of different projects in the field of alternative fuels, two liquid single-component fuels (n-hexane, n-dodecane) and kerosene Jet A-1 were investigated. Flow fields of the nonreacting and reacting flow were measured using stereo particle image velocimetry. The flame structure and spray distribution were derived from CH* chemiluminescence and Mie scattering respectively. Lean blowout limits were measured. Results show noticeable differences in combustion behaviour of the chosen fuels at comparable flow conditions. Furthermore, the results provide a detailed data base for the validation of numerical models.

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Laser-Based Investigations of Thermoacoustic Instabilities in a Lean Premixed Gas Turbine Model Combustor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2718224 ◽

2006 ◽

Vol 129 (3) ◽

pp. 664-671 ◽

Cited By ~ 15

Author(s):

Peter Weigand ◽

Wolfgang Meier ◽

Xuru Duan ◽

Manfred Aigner

Keyword(s):

Gas Turbine ◽

Mixture Fraction ◽

Measurement Techniques ◽

Pressure Fluctuations ◽

Three Dimensional ◽

Joint Probability ◽

Optical Measurements ◽

Laser Raman ◽

Lean Premixed ◽

Turbine Model

Nonintrusive laser-based and optical measurements were performed in a gas turbine model combustor with a lean premixed swirl-stabilized CH4-air flame at atmospheric pressure. The main objective was to gain spatially and temporally resolved experimental data to enable the validation of numerical CFD results of oscillating flames. The investigated flame was operated at 25 kW and ϕ=0.70, and exhibited self-excited oscillations of more than 135 dB at ≈300Hz. The applied measurement techniques were three-dimensional (3D) laser doppler velocimetry (LDV) for velocity measurements, OH* chemiluminescence yielding information about the heat release and pointwise laser Raman scattering for the determination of joint probability density functions (PDFs) of the major species concentrations, temperature, and mixture fraction. Each of these techniques was applied with phase resolution with respect to the periodic fluctuation of the pressure in the combustion chamber that was measured with a microphone probe. The measurements finally revealed that the mixing of fuel and air in this technical premixing system was strongly affected by the pressure fluctuations leading to changes in equivalence ratio during an oscillation cycle that, in turn, induced the pressure fluctuations.

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