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

# Influence of Pressure and Steam Dilution on $NOx$ and CO Emissions in a Premixed Natural Gas Flame

[+] Author and Article Information
Sebastian Göke, Thoralf Reichel, Katharina Göckeler

Chair of Fluid Dynamics,
Hermann-Föttinger-Institute,
Technische Universität,
Berlin 10623, Germany

Sebastian Schimek

Chair of Fluid Dynamics,
Hermann-Föttinger-Institute,
Technische Universität,
Berlin 10623, Germany
e-mail: sebastian.goeke@tu-berlin.de

Steffen Terhaar

Chair of Fluid Dynamics,
Hermann-Föttinger-Institute,
Technische Universität,
Berlin 10623, Germany

Oliver Krüger

Chair of Fluid Dynamics,
Hermann-Föttinger-Institute,
Technische Universität
Berlin 10623, Germany

Julia Fleck, Peter Griebel

German Aerospace Center (DLR),
Institute of Combustion Technology,
Stuttgart 70569, Germany

Christian Oliver Paschereit

Chair of Fluid Dynamics,
Hermann-Föttinger-Institute,
Technische Universität,
Berlin 10623, Germany
e-mail: oliver.paschereit@tu-berlin.de

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 January 26, 2014; final manuscript received February 9, 2014; published online April 18, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(9), 091508 (Apr 18, 2014) (8 pages) Paper No: GTP-14-1050; doi: 10.1115/1.4026942 History: Received January 26, 2014; Revised February 09, 2014

## Abstract

In the current study, the influence of pressure and steam on the emission formation in a premixed natural gas flame is investigated at pressures between 1.5 bar and 9 bar. A premixed, swirl-stabilized combustor is developed that provides a stable flame up to very high steam contents. Combustion tests are conducted at different pressure levels for equivalence ratios from lean blowout to near-stoichiometric conditions and steam-to-air mass ratios from 0% to 25%. A reactor network is developed to model the combustion process. The simulation results match the measured $NOx$ and CO concentrations very well for all operating conditions. The reactor network is used for a detailed investigation of the influence of steam and pressure on the $NOx$ formation pathways. In the experiments, adding 20% steam reduces $NOx$ and CO emissions to below 10 ppm at all tested pressures up to near-stoichiometric conditions. Pressure scaling laws are derived: CO changes with a pressure exponent of approximately −0.5 that is not noticeably affected by the steam. For the $NOx$ emissions, the exponent increases with equivalence ratio from 0.1 to 0.65 at dry conditions. At a steam-to-air mass ratio of 20%, the $NOx$ pressure exponent is reduced to −0.1 to +0.25. The numerical analysis reveals that steam has a strong effect on the combustion chemistry. The reduction in $NOx$ emissions is mainly caused by lower concentrations of atomic oxygen at steam-diluted conditions, constraining the thermal pathway.

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## Figures

Fig. 2

Setup for the gas-fired tests

Fig. 1

Sketch of the injector. The circular combustion chamber for the water tunnel experiments is shown.

Fig. 4

Line-of-sight integrated OH* chemiluminescence images of the flame (window size is 140 mm × 140 mm)

Fig. 3

Schematic of the reactor network

Fig. 5

Blowout limit

Fig. 6

Measured CO concentrations. For each curve, the equivalence ratio is decreased from φ = 0.95 in steps of Δφ = 0.05 until blowout occurs.

Fig. 8

Measured NOx concentrations for different pressures at Ω = 0 and Ω = 0.2

Fig. 9

Measured and simulated emissions for Ω = 0 and Ω = 0.2 at various pressures: (a) CO emissions, and (b) NOx emissions

Fig. 7

Measured NOx concentration for 1.5 bar

Fig. 10

Contribution of the NOx formation pathways: (a) p = 1.5 bars, ω = 0; (b) p = 9 bars, ω = 0; (c) p =  6.5 bars, ω = 0.2; and (d) p = 9 bars, ω  = 0.2

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