PowerPoint Presentationfaculty.washington.edu/malte/pubs/conferences/GT-2007-27990.pdf–Gas turbine...
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GT 2007-27990 Development and Application of an 8-Step Global Mechanism for
CFD and CRN Simulations of Lean-Premixed Combustors
Igor V. Novosselov and Philip C. Malte
University of Washington
ASME Turbo Expo
Montreal
May 14-17, 2007
Outline
• Purpose of 8-step mechanism:
– CFD and CRN predictions of NOx and CO for natural
gas-fired lean-premixed combustion turbines.
• Development of 8-step mechanism:
– Foundation in high-pressure JSR measurements.
– Chemical reactor modeling with GRI 3.0 used to
develop the “database.”
– Regression analysis used to obtain the 8 global steps.
• Application and verification of 8-step mechanism:
– 15 atm bluff body combustor.
– Gas turbine engine test rig.
– CFD model of generic can-type combustor.
The 8-Steps
Nitric Oxide Reaction Chemistry for Lean-Premixed Combustion
Foundation in High-Pressure Jet-Stirred Reactor Measurements:
Modeling of data of Bengtsson by Rutar and Malte
(phi = 0.55, T = 1828K, 88% PSR/ 12% PFR).
Chemical reactor schemes used in developing the “database” –
pressure 5-20 atm, inlet air temperature corresponding to 85%
efficient compression from 288K, phi 0.45-0.75
“Data” provided
• Temperature
• Major species concentrations: CH4, CO, CO2, O2, H2O,
N2, and OH.
• Species involved in NO formation: CH, N2O, NNH, O,
and H.
• Rates of CH4 and CO oxidation and CO2 dissociation.
• Rates of NO formation by the Zeldovich, nitrous oxide,
prompt, and NNH mechanisms.
Global Rate Expression
Obtaining the Global Rates
Example: Global Rate vs Rate by Elemental Chemistry
Bluff body combustor (Bucher et al.): methane, 680K inlet T, 14.3
atm, 1.1 kg/s air, 0.63 blockage ratio, effusion cooled.
Temperature field by 2-D CFD shown top plot: 1930K peak.
(flow from left to right)
Predicted CO (2.2% peak) and NO (14 ppm peak) also shown.
(phi = 0.59)
Bluff body: comparison of modeling results to measurements
0
100
200
300
400
500
600
700
800
0.55 0.57 0.59 0.61 0.63 0.65 0.67 0.69 0.71
premixer phi
CO
pp
mv
dry
(1
5%
O2
) .
experimental data
CFD area-average
CFD weighted to probe
CFD on centerline
0
10
20
30
40
50
60
70
80
0.55 0.57 0.59 0.61 0.63 0.65 0.67 0.69
premixer phi
NO
x p
pm
v d
ry (
15
% O
2)
.
experimental data
CFD weighted to probe
CFD without thermal NO weighted to probe
L&S high (front-end phi)
L&S low (front-end phi plus wall-cooling air)
Gas Turbine Engine Test Rig Data (Novosselov et al.): Comparison
between data and 31-element CRN predictions using full mechanism and
8-step mechanism.
0.0
0.5
1.0
1.5
2.0
2.5
0 50 100 150 200
Pilot, % of Neutral
NO
x, N
orm
alized
Em
issio
n
CRN: 8-step mechanism
CRN: GRI 3.0 mechanism
Engine test rig data
31-Element CRN for Lean-Premixed GT Combustor (Novosselov)
Application of 8-Step Mechanism in Modeling Generic Lean-
Premixed Gas Turbine Combustor (phi = 0.475, 50% pilot, 16 atm)
Application of 8-Step Mechanism in Modeling Generic Lean-
Premixed Gas Turbine Combustor (rates)
CFD Modeling Assumptions and Boundary Conditions
(bluff body at left, generic GT combustor at right)
END