scholarly journals The dilution effect on the extinction of wall diffusion flame

2014 ◽  
Vol 35 (4) ◽  
pp. 43-54
Author(s):  
Nadjib Ghiti
Keyword(s):  
Dilution Rate ◽  
Diffusion Flame ◽  
Flame Temperature ◽  
Dilution Effect ◽  
Lateral Wall ◽  
Flame Extinction ◽  
Jet Flame ◽  
Extinction Process ◽  
Nitrogen Dilution ◽  
Flame Response

Abstract The dynamic process of the interaction between a turbulent jet diffusion methane flame and a lateral wall was experimentally studied. The evolution of the flame temperature field with the Nitrogen dilution of the methane jet flame was examined. The interaction between the diffusion flame and the lateral wall was investigated for different distance between the wall and the central axes of the jet flame. The dilution is found to play the central role in the flame extinction process. The flame response as the lateral wall approaches from infinity and the increasing of the dilution rate make the flame extinction more rapid than the flame without dilution, when the nitrogen dilution rate increase the flame temperature decrease.

scholarly journals Dilution Effect on the Extinction of Impinging Diffusion Flame with a Lateral Wall

2013 ◽  
Vol 1 (2) ◽  
pp. 30-33 ◽  
Author(s):  
Nadjib Ghiti ◽  
Abed Alhalim Bentebbiche ◽  
Ramzi Boulkroune
Keyword(s):  
Diffusion Flame ◽  
Dilution Effect ◽  
Lateral Wall

scholarly journals Transport and chemical kinetics of H2/N2 jet flame: A flamelet modelling approach with NOx prediction

1970 ◽  
Vol 2 (1) ◽  
pp. 33-40 ◽  
Author(s):  
MA Alim ◽  
W Malalasekera
Keyword(s):  
Chemical Kinetics ◽  
Diffusion Flame ◽  
Mixture Fraction ◽  
Beta Function ◽  
Flame Temperature ◽  
Chemical Species ◽  
Lewis Number ◽  
Jet Flame ◽  
Marine Engineering ◽  
Kinetics Of

 In this work simulation of a turbulent H2/N2 jet diffusion flame with flamelet modelling has been presented. The favre-averaged mixture fraction has been employed to model the combustion. Favre-averaged scalar quantities have been calculated from flamelet libraries by making use of a presumed Probability Density Function (PDF) method. The predicted flame temperature profiles and chemical species concentrations are compared with TNF experimental data obtained from Sandia/California. Predictions considering the unity Lewis number flamelet are found to be in good agreement with temperature and chemical species measurements. Predicted NO results also compared and shown with other species. This study shows that the combustion simulation using unity Lewis number flamelets are effective for predicting the flow, temperature and chemical kinetics of H2/N2 diffusion flame. To account for fluctuations of mixture fraction, its distribution is presumed to have the shape of a beta-function. Keywords: Non-premixed flame, Turbulent Combustion, Flamelet modelling   doi: 10.3329/jname.v2i1.2028 Journal of Naval Architecture and Marine Engineering 2(1)(2005)33-40

Ultra-Low Emission Hydrogen/Syngas Combustion With a 1.3 MW Injector Using a Micro-Mixing Lean-Premix System

2011 ◽  
Author(s):  
Brian Hollon ◽  
Erlendur Steinthorsson ◽  
Adel Mansour ◽  
Vincent McDonell ◽  
Howard Lee
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Flame Temperature ◽  
Fuel Mixture ◽  
Full Scale ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Nitrogen Dilution ◽  
Fuel Mixtures

This paper discusses the development and testing of a full-scale micro-mixing lean-premix injector for hydrogen and syngas fuels that demonstrated ultra-low emissions and stable operation without flashback for high-hydrogen fuels at representative full-scale operating conditions. The injector was fabricated using Macrolamination technology, which is a process by which injectors are manufactured from bonded layers. The injector utilizes sixteen micro-mixing cups for effective and rapid mixing of fuel and air in a compact package. The full scale injector is rated at 1.3 MWth when operating on natural gas at 12.4 bar (180 psi) combustor pressure. The injector operated without flash back on fuel mixtures ranging from 100% natural gas to 100% hydrogen and emissions were shown to be insensitive to operating pressure. Ultra-low NOx emissions of 3 ppm were achieved at a flame temperature of 1750 K (2690 °F) using a fuel mixture containing 50% hydrogen and 50% natural gas by volume with 40% nitrogen dilution added to the fuel stream. NOx emissions of 1.5 ppm were demonstrated at a flame temperature over 1680 K (2564 °F) using the same fuel mixture with only 10% nitrogen dilution, and NOx emissions of 3.5 ppm were demonstrated at a flame temperature of 1730 K (2650 °F) with only 10% carbon dioxide dilution. Finally, using 100% hydrogen with 30% carbon dioxide dilution, 3.6 ppm NOx emissions were demonstrated at a flame temperature over 1600 K (2420 °F). Superior operability was achieved with the injector operating at temperatures below 1470 K (2186 °F) on a fuel mixture containing 87% hydrogen and 13% natural gas. The tests validated the micro-mixing fuel injector technology and the injectors show great promise for use in future gas turbine engines operating on hydrogen, syngas or other fuel mixtures of various compositions.

COMPUTATIONAL STUDY ON COMBUSTION AND EMISSION CHARACTERISTIC OF PILOTED FLAMES BY VARYING COMPOSITION CO2 OF SIMULATED BIOGAS

2017 ◽  
Vol 79 (7-3) ◽  
Author(s):  
Khor Chin Keat ◽  
M. F. Mohd Yasin ◽  
M. A. Wahid ◽  
A. Saat ◽  
A. S. Md Yudin
Keyword(s):  
Computational Study ◽  
Flame Temperature ◽  
Dilution Effect ◽  
Co2 Concentration ◽  
Nox Emission ◽  
Combustion Model ◽  
Emission Characteristic ◽  
Measured Temperature ◽  
Flamelet Model ◽  
Detailed Chemistry

This study investigates the performance of flamelet model technique in predicting the behavior of piloted flame.A non-premixed methane flame of a piloted burner is simulated in OpenFOAM. A detailed chemistry of methane oxidation is integrated with the flamelet combustion model using probability density function (pdf) approach. The turbulence modelling adopts Reynolds Average Navier Stokes (RANS) framework with standard k-ε model. A comparison with experimental data demonstrates good agreement between the predicted and the measured temperature profiles in axial and radial directions. Recently, one of major concern with combustion system is the emission of pollution specially NOx emission. Reduction of the pollutions can be achieved by varying the composition of CO2 in biogas. In addition, the effect of the composition of biogas on NOx emission of piloted burner is still not understood. Therefore, understanding the behavior composition of CO2 in biogas is important that could affect the emission of pollution. In the present study, the use of biogas with composition of 10 to 30 percent of CO2 is simulated to study the effects of biogas composition on NOx emission. The comparison between biogas and pure methane are done based on the distribution of NOx, CO2, CH4, and temperature at different height above the burner. At varying composition of CO2 in biogas, the NOx emission for biogas with 30 percent CO2 is greatly reduced compared to that of 10 percent CO2. This is due to the reduction of the post flame temperature that is produced by the dilution effect at high CO2 concentration.  

Laminar Microjet Diffusion Flame Response to Transverse Acoustic Excitation

2020 ◽  
Vol 192 (7) ◽  
pp. 1292-1319 ◽  
Author(s):  
Hyung Sub Sim ◽  
Andres Vargas ◽  
Dongchan Daniel Ahn ◽  
Ann R. Karagozian
Keyword(s):  
Diffusion Flame ◽  
Acoustic Excitation ◽  
Transverse Acoustic ◽  
Flame Response

Response Dynamics of Recirculation Structures in Coaxial Nonpremixed Swirl-Stabilized Flames Subjected to Acoustic Forcing

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Uyi Idahosa ◽  
R. Santhosh ◽  
Ankur Miglani ◽  
Saptarshi Basu
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Fluid Dynamic ◽  
High Energy ◽  
Reacting Flow ◽  
Flow State ◽  
Response Dynamics ◽  
Jet Flame ◽  
Flame Response ◽  
Acoustic Forcing

This paper reports the time-mean and phase-locked response of nonreacting as well as reacting flow field in a coaxial swirling jet/flame (nonpremixed). Two distinct swirl intensities plus two different central pipe flow rates at each swirl setting are investigated. The maximum response is observed at the 105 Hz mode in the range of excitation frequencies (0–315 Hz). The flow/flame exhibited minimal response beyond 300 Hz. It is seen that the aspect ratio change of inner recirculation zone (IRZ) under nonreacting conditions (at responsive modes) manifests as a corresponding increase in the time-mean flame aspect ratio. This is corroborated by ∼25% decrease in the IRZ transverse width in both flame and cold flow states. In addition, 105 Hz excited states are found to shed high energy regions (eddies) asymmetrically when compared to dormant 315 Hz pulsing frequency. The kinetic energy (KE) of the flow field is subsequently reduced due to acoustic excitation and a corresponding increase (∼O (1)) in fluctuation intensity is witnessed. The lower swirl intensity case is found to be more responsive than the high swirl case as in the former flow state the resistance offered by IRZ to incoming acoustic perturbations is lower due to inherently low inertia. Next, the phase-locked analysis of flow and flame structure is employed to further investigate the phase dependence of flow/flame response. It is found that the asymmetric shifting of IRZ mainly results at 270 deg acoustic forcing. The 90 deg phase angle forcing is observed to convect the IRZ farther downstream in both swirl cases as compared to other phase angles. The present work aims primarily at providing a fluid dynamic view point to the observed nonpremixed flame response without considering the confinement effects.

Extended Le Chatelier's formula and nitrogen dilution effect on the flammability limits

2006 ◽  
Vol 41 (5) ◽  
pp. 406-417 ◽  
Author(s):  
Shigeo Kondo ◽  
Kenji Takizawa ◽  
Akifumi Takahashi ◽  
Kazuaki Tokuhashi
Keyword(s):  
Dilution Effect ◽  
Flammability Limits ◽  
Nitrogen Dilution

Mathematical Imaging of Piloted Diffusion Methane-Air Flames Under Anisotropic Scalar Dissipation Rates

2005 ◽  
Author(s):  
Mohsen M. Abou-Ellail ◽  
Karam R. Beshay ◽  
David R. Halka
Keyword(s):  
Diffusion Flame ◽  
Dissipation Rate ◽  
Mixture Fraction ◽  
Flame Temperature ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Scalar Dissipation ◽  
Elementary Reactions ◽  
Chemical Kinetic Mechanism ◽  
Limiting Value

The present work is a numerical simulation of the, piloted, non-premixed, methane–air flame structure in a new mathematical imaging domain. This imaging space has the mixture fraction of diffusion flame Z1 and mixture fraction of pilot flame Z2 as independent coordinates to replace the usual physical space coordinates. The predications are based on the solution of two–dimensional set of transformed second order partial differential conservation equations describing the mass fractions of O2, CH4, CO2, CO, H2O, H2 and sensible enthalpy of the combustion products which are rigorously derived and solved numerically. A three–step chemical kinetic mechanism is adopted. This was deduced in a systematic way from a detailed chemical kinetic mechanism by Peters (1985). The rates for the three reaction steps are related to the rates of the elementary reactions of the full reaction mechanism. The interaction of the pilot flame with the non-premixed flame and the resulting modifications to the structure and chemical kinetics of the flame are studied numerically for different values of the scalar dissipation rate tensor. The dissipation rate tensor represents the flame stretching along Z1, the main mixture fraction, and in the perpendicular direction, along Z2, the pilot mixture fraction. The computed flame temperature contours are plotted in the Z1-Z2 plane for fixed values of the dissipation rate along Z1 and Z2.These temperature contours show that the flame will become unstable when the dissipate rates along Z1 and Z2 increase, simultaneously, to the limiting value for complete flame extinction of 45 s−1. However, the diffusion flame will extinguish for dissipate rates less than 20 1/s, if unpiloted. It is also noticed that the flame will remain stable if the dissipation rate along Z2 is increased to the limiting value, while the dissipation rate, along Z2, remains constant at a value less than 30 s−1.

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