Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Design Improvement Survey for NOx Emissions Reduction of a Heavy-Duty Gas Turbine Partially Premixed Fuel Nozzle Operating With Natural Gas: Numerical Assessment

[+] Author and Article Information
Alessandro Innocenti

Department of Industrial Engineering,
University of Florence,
Via S. Marta 3,
Florence 50139, Italy
e-mail: alessandro.innocenti@htc.de.unifi.it

Antonio Andreini, Bruno Facchini

Department of Industrial Engineering,
University of Florence,
Via S. Marta 3,
Florence 50139, Italy

Matteo Cerutti, Gianni Ceccherini, Giovanni Riccio

GE Oil & Gas Nuovo Pignone s.r.l.,
Via F. Matteucci 2,
Florence 50127, Italy

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 15, 2015; final manuscript received July 22, 2015; published online August 12, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(1), 011501 (Aug 12, 2015) (9 pages) Paper No: GTP-15-1324; doi: 10.1115/1.4031144 History: Received July 15, 2015

A numerical investigation of a low NOx partially premixed fuel nozzle for heavy-duty gas turbine applications is presented in this paper. Availability of results from a recent test campaign on the same fuel nozzle architecture allowed the exhaustive comparison study presented in this work. At first, an assessment of the turbulent combustion model was carried out, with a critical investigation of the expected turbulent combustion regimes in the system and taking into account the partially premixed nature of the flame due to the presence of diffusion type pilot flames. In particular, the fluent partially premixed combustion model and a flamelet approach are used to simulate the flame. The laminar flamelet database is generated using the flamelet generated manifold (FGM) chemistry reduction technique. Species and temperature are parameterized by mixture fraction and progress variable. Comparisons with calculations with partially premixed model and the steady diffusion flamelet (SDF) database are made for the baseline configuration in order to discuss possible gains associated with the introduced dimension in the FGM database (reaction progress), which makes it possible to account for nonequilibrium effects. Numerical characterization of the baseline nozzle has been carried out in terms of NOx. Computed values for both the baseline and some alternative premixer designs have been then compared with experimental measurements on the reactive test rig at different operating conditions and different split ratios between main and pilot fuel. Numerical results allowed pointing out the fundamental NOx formation processes, both in terms of spatial distribution within the flame and in terms of different formation mechanisms. The obtained knowledge would allow further improvement of fuel nozzle design.

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Fig. 1

DACRS premixer scheme

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Fig. 2

Axial velocity and TKE contours

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Fig. 3

CH4 mass fraction profiles along the premixer

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Fig. 4

Alternative premixer designs: SW1 (a), SW3 (b), and SW4 (c)

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Fig. 5

Scheme of the workflow

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Fig. 6

Computed and scaled profiles: data matching

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Fig. 7

Reactive test rig: computational domain and mesh

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Fig. 8

Progress variable (a) and nondimensional temperature (b) contours: comparison between SDF model and the FGM one

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Fig. 9

Progress variable source terms: FR (top) and TFC (bottom)

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Fig. 10

No emissions for the tested combustion models

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Fig. 11

Global correlation between numerical results and experimental data

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Fig. 12

No emissions against flame temperature, for the simulated configurations

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Fig. 13

Scaled mixture fraction and temperature in the combustor with SW0 and SW4 designs

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Fig. 14

Contributions of the no formation mechanisms to the global reaction rate

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Fig. 15

No emissions against pilot split

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Fig. 16

No emissions against combustor pressure drop

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Fig. 17

NOx emissions against combustion residence time in the combustion chamber

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Fig. 18

Contours of RMS of temperature for two different pressure drops




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