Numerical and experimental investigation of a mild combustion burner (original) (raw)
Related papers
2016
An industrial burner operating in the MILD combustion regime with high air preheating and strong internal exhaust gas recirculation is numerically simulated. The burner is characterized by relatively low flame temperatures, low NOx emissions, no visible flame and no sound. The ILDM technique is combined with the presumed probability density function approach to simulate turbulent combustion. A computational fluid dynamics (CFD) model is set up comprising the input of geometrical model, mesh-refining process, setting up physical model, handling of algorithms of solution, and the incorporation of appropriate user subroutine that was linked to the fluent code. Predictions of the mean flow field, turbulence kinetic energy, temperature, mass fraction of CO2, H2O and NOx emissions are presented. The calculated mean velocities and temperatures reproduce experimental data reasonably well, but some small discrepancies were found. The NO emissions calculated are compared both with in-furnace ...
Numerical simulation of an industrial radiant burner
2004
The present paper reports the 3-D CFD modelling of an industrial swirl radiant burner (12.8 – 18 kW) performed by means of a commercial code (FLUENT). The first step was the validation of the code through a detailed comparison with experimental velocity data acquired under isothermal flow regimes for different operating conditions. On this basis the reactive characterization was carried out and the thermal and fluid dynamic flow patterns were compared with the experimental measurements. The k – ε RSM (Reynolds Stress Model) model was used for Navier – Stokes equation closure and the air – methane reaction was modelled with the 2 step reaction approach with Finite Rate – Eddy Dissipation model. For the radiative characterization it was chosen the DO (Discrete Ordinates) model. Moreover, the simulation of a modified burner geometry with internal EGR was performed and confirmed the experimentally observed reduction of pollutant emissions. INTRODUCTION Industrial radiant burners have be...
Numerical Model Analysis of Natural Gas Combustion Burners
International Journal of Engineering and Management Sciences
Traditional power plants still the dominating power source for all the major industries and powerdemanding facilities, the most crucial facility for the whole plant operations is the industrial boiler which generatessteam, heating energy or electrical power. Boilers generate energy by combustion. The improvement of combustion efficiency could greatly influence the energy consumption and will make the boiler more efficient and cleaner (less emissions), that’s why it is important to understand the combustion and thermal flow behaviours inside the boiler. Beside experimental testing, computational work nowadays becoming more and more important due to lower cost and acceptable accuracy with minimum error. With numerical calculations method, the computational model created by a Computational Fluid Dynamics (CFD) software could reduce a lot of trial and error on experimental work. In this paper utilizing the ANSYS FLUENT 19.1 software to make crate the combustion model. The ratio of air t...
This paper presents experimental and computational results of a small-scale combustor operating in the mild combustion regime. On the experimental side, flue-gas composition data and hydroxyl radical chemiluminescence (OH*) imaging are reported as a function of the preheat temperature of the combustion air. For two of these combustor operating conditions, spatial distributions of temperature and of O 2 , CO 2 , unburned hydrocarbons, CO and NO x concentrations are also reported. The combustor yields low CO (< 10 ppm@15% O 2 ) and NO x emissions (< 14 ppm@15% O 2 ) regardless of the inlet air temperature; the OH* images reveal that as the inlet air temperature increases the main reaction zone moves progressively closer to the burner; the chemiluminescence images also show that the OH* gradients increase as the level of air preheating increases; and the detailed measurements made inside the combustor confirmed the expected uniformity of the measured fields over the entire combustion chamber, as expected when operating under mild conditions. On the modelling side, the calculations were carried out using the commercial code Ansys-Fluent. Turbulence was modelled using the realizable k-ε model. The eddy dissipation concept was employed along with a skeletal chemical mechanism comprising 13 transported species and 73 chemical reactions Additional calculations carried out using a global single-step reaction are also reported. The more detailed reaction mechanism is able to accurately predict the temperature and the concentrations of O 2 and CO 2 over most of the combustor, but the temperature field is overestimated in the vicinity of the burner. Discrepancies are found in the prediction of the CO concentrations.
This work reports numerical simulations of a small-scale cylindrical combustor operating in the mild combustion regime. Preheated air is supplied by a central nozzle, while the fuel (methane) is injected through 16 holes placed equidistantly in a circumference concentric with the air nozzle. The calculations were carried out using the commercial code Ansys-Fluent. Turbulence was modelled using the realizable k-ε model. Two different combustion models were employed, namely the eddy dissipation concept and the joint composition pdf transport model. In both cases, a chemical mechanism comprising 13 transported species and 73 chemical reactions was used, as well as a global single-step reaction. A thorough comparison of the predictions obtained using the pdf transport model and the eddy dissipation concept with detailed experimental data is presented. Both models are able to accurately predict the temperature and the O 2 and CO 2 molar fractions over most of the combustor, but the temperature field is overestimated in the vicinity of the burner. Discrepancies are found in the prediction of the CO molar fraction, particularly when the eddy dissipation concept is used.
Numerical Simulation of a Small-Scale Mild Combustor
Journal of Physics: Conference Series, 2012
This work reports numerical simulations of a small-scale cylindrical combustor operating in the mild combustion regime. Preheated air is supplied by a central nozzle, while the fuel (methane) is injected through 16 holes placed equidistantly in a circumference concentric with the air nozzle. The calculations were carried out using the commercial code Ansys-Fluent. Turbulence was modelled using the realizable k-ε model. Two different combustion models were employed, namely the eddy dissipation concept and the joint composition pdf transport model. In both cases, a chemical mechanism comprising 13 transported species and 73 chemical reactions was used, as well as a global single-step reaction. A thorough comparison of the predictions obtained using the pdf transport model and the eddy dissipation concept with detailed experimental data is presented. Both models are able to accurately predict the temperature and the O 2 and CO 2 molar fractions over most of the combustor, but the temperature field is overestimated in the vicinity of the burner. Discrepancies are found in the prediction of the CO molar fraction, particularly when the eddy dissipation concept is used.
Application of Scalar Dissipation Rate Modelling to Industrial Burners in Partially Premixed Regimes
The objective of this paper is to test various available turbulent burning velocity models on an experimental version of Siemens small scale combustor using the commercial CFD code. Failure of burning velocity model with different expressions for turbulent burning velocity is observed with an unphysical flame flashback into the swirler. Eddy Dissipation Model/Finite Rate Chemistry is found to over-predict mean temperature and species concentrations. Solving for reaction progress equation with its variance using scalar dissipation rate modelling produced reasonably good agreement with the available experimental data. Two different turbulence models Shear Stress Transport (SST) and Scale Adaptive Simulation (SAS) SST are tested and results from transient SST simulations are observed to be predicting well. SAS-SST is found to under-predict with temperature and species distribution. Introduction Numerical combustion modelling of practical combustors which involves major complexities nee...
Design and Development of MILD Combustion Burner
Journal of Mechanical Engineering and Sciences, 2013
This paper discussed the design and development of the Moderate and Intense Low oxygen Dilution (MILD) combustion burner using Computational Fluid Dynamics (CFD) simulations. The CFD commercial package was used to simulate preliminary designs for the burner before the final design was sent to workshop for the fabrication. The burner is required to be a non-premixed and open burner. To capture and use the exhaust gas, the burner was enclosed within a large circular shaped wall with an opening at the top. An external EGR pipe was used to transport the exhaust gas which was mixed with the fresh oxidant. To control the EGR and exhaust flow, butterfly valves were installed at the top opening as a damper to close the exhaust gas flow at the certain ratio for EGR and exhaust out to atmosphere. High temperature fused silica glass windows were installed to view and capture images of the flame and analyse the flame propagation. The burner simulation shows that MILD combustion was achieved for...