Modelling practical combustion systems and predicting NOx emissions with an integrated CFD based approach

2002 ◽  
Vol 26 (9) ◽  
pp. 1171-1183 ◽  
Author(s):  
M. Falcitelli ◽  
S. Pasini ◽  
L. Tognotti
Keyword(s):  
Nox Emissions ◽  
Combustion Systems

Large-Eddy Simulation of a Reacting Jet in Cross Flow With NOx Prediction

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Johannes Weinzierl ◽  
Michael Kolb ◽  
Denise Ahrens ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Large Eddy Simulation ◽  
Cross Flow ◽  
Nox Emissions ◽  
Staged Combustion ◽  
Nox Formation ◽  
Full Load ◽  
Eddy Simulation ◽  
Jet In Cross Flow ◽  
Large Eddy ◽  
Combustion Systems

The reduction of full and part load emissions and the increase of the turndown ratio are important goals for gas turbine combustor development. Combustion techniques, which generate lower NOx emissions than unstaged premixed combustion in the full load range, and which have the potential of reducing minimum load while complying with emission legislation, are of high technical interest. Therefore, axial-staged combustion systems have been designed, either with or without expansion in a turbine stage between both stages. In its simpler form without intermediate expansion stage, a flow of hot combustion products is generated in the first stage of the premixed combustor, which interacts with the jets of premixed gas injected into the second stage. The level of NOx formation during combustion of the premixed jets in the hot cross flow determines the advantage of axially staged combustion regarding full load NOx emission reduction. Employing large-eddy simulation in openfoam, a tool has been developed, which allows to investigate staged combustion systems including not only temperature distribution but also NOx emissions under engine conditions. To be able to compute NOx formation correctly, the combustion process has to be captured with sufficient level of accuracy. This is achieved by the partially stirred reactor model. It is combined with a newly developed NOx model, which is a combination of a tabulation technique for the NOx source term based on mixture fraction and progress variable and a partial equilibrium approach. The NOx model is successfully validated with generic burner stabilized flame data and with measurements from a large-scale reacting jet in cross flow experiment. The new NOx model is finally used to compute a reacting jet in cross flow under engine conditions to investigate the NOx formation of staged combustion in detail. The comparison between the atmospheric and the pressurized configuration gives valuable insight in the NOx formation process. It can be shown that the NOx formation within a reacting jet in cross flow configuration is reduced and not only diluted.

Chemical Kinetic Modeling of Ignition and Emissions From Natural Gas and LNG Fueled Gas Turbines

2012 ◽  
Author(s):  
P. Gokulakrishnan ◽  
C. C. Fuller ◽  
R. G. Joklik ◽  
M. S. Klassen
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Chemical Kinetic ◽  
Higher Order ◽  
Premixed Combustion ◽  
Nox Emissions ◽  
Lean Premixed Combustion ◽  
Lean Premixed ◽  
Combustion Systems

Single digit NOx emission targets as part of gas turbine design criteria require highly accurate modeling of the various NOx formation pathways. The concept of lean, premixed combustion is adopted in various gas turbine combustor designs, which achieves lower NOx levels by primarily lowering the flame temperature. At these conditions, the post-flame thermal-NOx pathway contribution to the total NOx can be relatively small compared to that from the prompt-NOx and the N2O-route, which are enhanced by the super-equilibrium radical pathway at the flame front. In addition, new sources of natural gas fuel (e.g., imported LNG) with widely varying chemical compositions including higher order hydrocarbon components, impact flame stability, lean blow-out limits and emissions in existing lean premixed combustion systems. Also, the presence of higher order hydrocarbons can increase the risk of flashback induced by autoignition in the premixing section of the combustor. In this work a detailed chemical kinetic model was developed for natural gas fuels that consist of CH4, C2H6, C3H8, nC4H10, iC4H10, and small amounts of nC5H12, iC5H12 and nC6H14 in order to predict ignition behavior at typical gas turbine premixing conditions and to predict CO and NOx emissions at lean premixed combustion conditions. The model was validated for different NOx-pathways using low and high pressure laminar premixed flame data. The model was also extended to include a vitiated kinetic scheme to account for the influence of exhaust gas recirculation on fuel oxidation. The model was employed in a chemical reactor network to simulate a laboratory scale lean premixed combustion system to predict CO and NOx. The current kinetic mechanism demonstrates good predictive capability for NOx emissions at lower temperatures typical of practical lean premixed combustion systems.

Large Eddy Simulation of a Reacting Jet in Cross Flow With NOx Prediction

2016 ◽  
Author(s):  
Johannes Weinzierl ◽  
Michael Kolb ◽  
Denise Ahrens ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Large Eddy Simulation ◽  
Cross Flow ◽  
Nox Emissions ◽  
Staged Combustion ◽  
Nox Formation ◽  
Full Load ◽  
Eddy Simulation ◽  
Jet In Cross Flow ◽  
Large Eddy ◽  
Combustion Systems

The reduction of full and part load emissions and the increase of the turndown ratio are important goals for gas turbine combustor development. Combustion techniques, which generate lower NOx emissions than unstaged premixed combustion in the full load range, and which have the potential of reducing minimum load while complying with emission legislation, are of high technical interest. Therefore axial staged combustion systems have been designed, either with or without expansion in a turbine stage between both stages. In its simpler form without intermediate expansion stage a flow of hot combustion products is generated in the first stage of the premixed combustor, which interacts with the jets of premixed gas injected into the second stage. The level of NOx formation during combustion of the premixed jets in the hot cross flow determines the advantage of axially staged combustion regarding full load NOx emission reduction. Employing Large Eddy Simulation in OpenFOAM, a tool has been developed, which allows to investigate staged combustion systems including not only temperature distribution but also NOx emissions under engine conditions. To be able to compute NOx formation correctly the combustion process has to be captured with sufficient level of accuracy. This is achieved by the partially stirred reactor model. It is combined with a newly developed NOx model, which is a combination of a tabulation technique for the NOx source term based on mixture fraction and progress variable and a partial equilibrium approach. The NOx model is successfully validated with generic burner stabilized flame data and with measurements from a large scale reacting jet in cross flow experiment. The new NOx model is finally used to compute a reacting jet in cross flow under engine conditions to investigate the NOx formation of staged combustion in detail. The comparison between the atmospheric and the pressurized configuration gives valuable insight in the NOx formation process. It can be shown that the NOx formation within a reacting jet in cross flow configuration is reduced and not only diluted.

scholarly journals Uncertainty in Gas Turbine NOx Emission Measurements

1998 ◽  
Author(s):  
Wilfred S. Y. Hung ◽  
Alan Campbell
Keyword(s):  
Measurement Uncertainty ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Water Injection ◽  
Nox Emission ◽  
Regulatory Agencies ◽  
Nox Emissions ◽  
Current State ◽  
Combustion Systems ◽  
Good Agreement

The advent of dry, low-emissions combustion systems for gas turbine applications and the trend towards requiring emissions monitoring and lower NOx limits by regulatory agencies, have created renewed interests in the uncertainty of NOx emissions measurements. This paper addresses the uncertainty of measuring NOx emissions from gas turbines in the field, including gas turbines equipped with conventional combustion systems, with or without water injection, with dry, low-emissions combustion systems and with exhaust clean-up systems. The sources of errors, using current state-of-the-art instruments, in field emissions testing or continuous emission monitoring of gas turbines to meet specific emission (ppmvd @ 15% O2) as well as mass emission rate (kg/hr) limits are identified. The uncertainty of measuring NOx emissions from gas turbines is estimated and compared with Geld data. The effect of NOx emission levels on measurement uncertainty is also addressed. The minimus NOx measurement uncertainty is determined and is in good agreement with what is currently allowed by regulatory agencies.

High-Intensity Burners with Low Nox Emissions

1992 ◽  
Vol 206 (1) ◽  
pp. 3-17 ◽  
Author(s):  
G E Andrews ◽  
H S Alkabie ◽  
M M Abdul Aziz ◽  
U S Abdul Hussain ◽  
N A Al Dabbagh ◽  
...  
Keyword(s):  
Shear Layer ◽  
Gas Turbine ◽  
High Intensity ◽  
Gas Turbines ◽  
Nox Emissions ◽  
Cent Oxygen ◽  
Air Mixing ◽  
Industrial Gas Turbines ◽  
Combustion Systems ◽  
Flow Blockage

Experimental combustion and NOx emissions results are summarized for a range of jet shear layer combustion systems that have rapid fuel and air mixing, short intense flames, a high turn-down ratio and low NOx characteristics. Two burner sizes of 76 and 140 mm are investigated for propane and natural gas. Three jet shear layer burners are compared with axial and radial swirlers. The combustion techniques were developed for application to low NOx combustion systems for industrial gas turbines, where NOx emissions as low as 10 ppm at 15 per cent oxygen have been demonstrated. It is shown that at one bar pressure, gas turbine combustors and high-intensity burners operate at similar air flow, blockage and pressure loss conditions.

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