scholarly journals Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

2019 ◽  
Vol 9 (19) ◽  
pp. 3989 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Qian Chen ◽  
...  
Keyword(s):  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Flame Height ◽  
Reacting Flow ◽  
Detailed Chemistry ◽  
Eddy Generation ◽  
Fire Whirl ◽  
Generation Mechanisms ◽  
The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5   m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

scholarly journals Numerical Study of the Comparison of Symmetrical and Asymmetrical Eddy-Generation Scheme on the Fire Whirl Formulation and Evolution

2020 ◽  
Vol 10 (1) ◽  
pp. 318 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Ho Lung Yip ◽  
...  
Keyword(s):  
Numerical Study ◽  
Computational Cost ◽  
Injection Rate ◽  
Flame Height ◽  
Large Radius ◽  
Detailed Chemistry ◽  
Eddy Simulation ◽  
Industrial Sectors ◽  
Eddy Generation ◽  
Fire Whirl

A numerical study of the fire whirl formation under symmetrical and asymmetrical entraining configuration is presented. This work aims to assess the effect of eddy-generation configuration on the evolution of the intriguing phenomenon coupled with both flow dynamics and combustion. The numerical framework implements large-eddy simulation, detailed chemistry to capture the sophisticated turbulence-chemistry interaction under reasonable computational cost. It also adopts liquid-based clean fuel with fixed injection rate and uniformed discretisation scheme to eliminate potential interference introduced by various aspects of uncertainties. The result reveals that the nascent fire whirl formulates significantly rapidly under the symmetrical two-slit configuration, with extended flame height and constrained vortex structure, compared with the asymmetrical baseline. However, its revolution orbit gradually diverges from domain centreline and eventually stabilises with a large radius of rotation, whereas the revolution pattern of that from the baseline case is relatively unchanged from the inception of nascent fire whirl. Through the analysis, the observed difference in evaluation pathway could be explained using the concept of circular motion with constant centripetal force. This methodology showcases its feasibility to reveal and visualise the fundamental insight and facilitate profound understanding of the flaming behaviour to benefit both research and industrial sectors.

scholarly journals Modeling diesel combustion with tabulated kinetics and different flame structure assumptions based on flamelet approach

2019 ◽  
Vol 21 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Tommaso Lucchini ◽  
Daniel Pontoni ◽  
Gianluca D’Errico ◽  
Bart Somers
Keyword(s):  
Soot Formation ◽  
Flame Structure ◽  
Combustion Process ◽  
Computational Cost ◽  
Pollutant Emissions ◽  
Diesel Combustion ◽  
Flamelet Generated Manifold ◽  
Tabulated Chemistry ◽  
Computational Fluid Dynamics Analysis ◽  
The Impact

Computational fluid dynamics analysis represents a useful approach to design and develop new engine concepts and investigate advanced combustion modes. Large chemical mechanisms are required for a correct description of the combustion process, especially for the prediction of pollutant emissions. Tabulated chemistry models allow to reduce significantly the computational cost, maintaining a good accuracy. In the present work, an investigation of tabulated approaches, based on flamelet assumptions, is carried out to simulate turbulent Diesel combustion in the Spray A framework. The Approximated Diffusion Flamelet is tested under different ambient conditions and compared with Flamelet Generated Manifold, and both models are validated with Engine Combustion Network experimental data. Flame structure, combustion process and soot formation were analyzed in this work. Computed results confirm the impact of the turbulent–chemistry interaction on the ignition event. Therefore, a new look-up table concept Five-Dimensional-Flamelet Generated Manifold, that accounts for an additional dimension (strain rate), has been developed and tested, giving promising results.

CFD Simulation of Confined Non-Premixed Flames

2012 ◽  
Author(s):  
Tanaji M. Dabade ◽  
Xianchang Li ◽  
Daniel Chen ◽  
Helen Lou ◽  
Christopher Martin ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flame Structure ◽  
Combustion Process ◽  
Premixed Combustion ◽  
Flame Height ◽  
Combustion Model ◽  
Ansys Fluent ◽  
Innovative Strategies ◽  
Precise Control ◽  
Fuel Jet

Material processing furnaces are the key component of the manufacturing industries. The burners used in these furnaces require precise control over the flame structure such as flame shape, height, and width. This study mainly focused on the simulation of the flame structure with Computational Fluid Dynamics (CFD) approach. ANSYS Fluent 13.0 was used to predict the flame characteristics in an enclosed cylinder. Non-premixed combustion model was applied to this combustion phenomenon. To control the flame structure, a micro jet at the centre of the burner is introduced. The effect on flame parameters with varying flow rates of micro jet, fuel jet and co-flow jet is examined. This study confirms the experimental study by Sinha et al. [1], which concluded that an air micro jet at the center of a non-premixed flame can control the flame height and luminosity. Moreover, this paper visualizes the thermo chemistry and transport phenomenon of non-premixed combustion process. Emissions from the combustion are monitored for different boundary conditions. This study shows that innovative strategies can be developed for the precise control over the different types of flames with the help of numerical modeling.

scholarly journals Fuel molecular structure effect on soot mobility size in premixed C6 hydrocarbon flames

2021 ◽  
Author(s):  
Shruthi Dasappa ◽  
Joaquin Camacho
Keyword(s):  
Size Distribution ◽  
Soot Particle ◽  
Volume Fraction ◽  
Soot Formation ◽  
Flame Structure ◽  
Flame Temperature ◽  
Similar Time ◽  
Mobility Diameter ◽  
Premixed Laminar ◽  
The Impact

Soot formation in premixed laminar flames is examined for a canonical set of flames burning C6 hydrocarbon fuels. Particle mobility size and flame temperature measurements are complemented by flame structure calculations using detailed flame chemistry. Specifically, the evolution of the detailed soot particle size distribution (PSDF) is compared for n-hexane, n-hexene, 2-methylpentane, cyclohexane and benzene at a carbon-to-oxygen ratio of 0.69 and maximum flame temperature of 1800 K. Under this constraint, the overall sooting process is comparable as evidenced by similar time resolved bimodal PSDF. However, the first inception of particles and the persistence of nucleation-sized particles with time are depend upon the structure of the parent fuel. For the given conditions, the fastest onset of soot is observed in cyclohexane and benzene flames and the observed evolution of the PSDF also shows that nucleation-sized particles disappear sooner in cyclohexane and benzene flames. Flame structure computations incorporating detailed chemistry show a clear connection between the early onset of soot particles as fuel specific routes to PAH formation are predicted in the pre-flame region of the cyclohexane and benzene flames. These observations illustrate the impact of alkane, alkene, cycloalkane and aromatic fuel structure on soot formation in premixed flames. Analysis of soot particle morphology by atomic force microscopy indicates that most of size distribution is composed of aggregates. Simple aggregate mobility diameter analysis shows the spherical assumption taken to interpret the mobility diameter does not impact the PSDF number density result but the inferred volume fraction for aggregates deviates by up to an order of magnitude depending on the morphology assumptions adopted.

Effects of Emulsified Fuel on the Performance and Emission Characteristics of Aeroengine Combustors

2019 ◽  
Author(s):  
M. G. De Giorgi ◽  
E. Pescini ◽  
S. Campilongo ◽  
G. Ciccarella ◽  
D. Fontanarosa ◽  
...  
Keyword(s):  
Flame Structure ◽  
Combustion Process ◽  
Optical Filters ◽  
Diagnostic Techniques ◽  
Jet Fuels ◽  
Test Case ◽  
Performance And Emission ◽  
Emulsified Fuel ◽  
Spectral Ranges ◽  
The Impact

Abstract The aim of the present work is the experimental investigation of the effects of the addition of water and urea into jet fuels, on the reduction of nitrogen oxides (NOx) emissions and eventually improvement of the lean flame stability in aeroengine combustors. Experiments have been carried out using a 300-kW liquid-fueled swirling combustor. Various urea and/or water concentrations have been tested at the same fuel/air ratio. In order to study the flame behavior, non-invasive optical diagnostic techniques, as charge-coupled device (CCD) cameras in different spectral ranges (Visible and UV ranges, with different optical filters), have been adopted to analyze the shape and the brightness of the flame structure. Measurements of exhaust emissions (NOx, SO2, CO, CO2 and O2) have also been performed in order to evaluate the impact of emulsification on the entire combustion process. Finally, the thermal efficiency losses with respect to the neat jet test case were also analyzed for each emulsified fuel condition.

Instability Control by Premixed Pilot Flames

2008 ◽  
Author(s):  
Peter Albrecht ◽  
Stefanie Bade ◽  
Arnaud Lacarelle ◽  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
Gas Turbines ◽  
Flame Structure ◽  
Premixed Flames ◽  
Combustion Process ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pilot Injection ◽  
Acoustic Instabilities ◽  
Flame Behavior ◽  
The Impact

Premixed flames of swirl-stabilized combustors (displaced-half-cone) are susceptible to thermo-acoustic instabilities which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can e.g. be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow and other methods. Pilot flames can alleviate this issue by either improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injection on the combustion stability is investigated. One of the pilot injector (pilot flame injector, PFI) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring (PR) placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation evidenced that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than when the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blow out when a percentage of the fuel was premixed with air and injected through the pilot ring. In the mean time, NOx emissions were significantly reduced.

scholarly journals Effect of added struts and intake velocity on flame stabilization in supersonic combustors

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Akram Mohammad ◽  
Keyword(s):  
Mole Fraction ◽  
Computational Study ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Single Step ◽  
Flame Stabilization ◽  
Reacting Flow ◽  
Mach Numbers ◽  
German Aerospace ◽  
The Impact

In the present computational study, the impact of strut positions and the effect of inlet Mach numbers on the combustion efficiency are investigated in a strut-based supersonic combustor. An experimentally investigated model combustor developed at the German Aerospace Center (DLR) is simulated and validated. Then, a model combustor with three struts placed at different positions is investigated. Two-dimensional, compressible, reacting-flow governing equations are solved along with single-step chemistry reaction and k-ω SST turbulence model using a commercial CFD code FLUENT. The oblique shock from the struts has a profound influence on the mixing and combustion process. The H2O mole fraction, H2 mole fraction contours, and combustion efficiency of various configurations are compared for finding better mixing and flame stabilization. The combustion efficiency reduces when the two struts are located in farther downstream or placed at the same downstream location. At higher Mach numbers, the combustion is delayed, and the mixing of fuel with the supersonic mainstream is incomplete.

Effects of Emulsified Fuel on the Performance and Emission Characteristics of Aeroengine Combustors

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
M. G. De Giorgi ◽  
E. Pescini ◽  
S. Campilongo ◽  
G. Ciccarella ◽  
D. Fontanarosa ◽  
...  
Keyword(s):  
Flame Structure ◽  
Combustion Process ◽  
Optical Filters ◽  
Diagnostic Techniques ◽  
Jet Fuels ◽  
Test Case ◽  
Performance And Emission ◽  
Emulsified Fuel ◽  
Spectral Ranges ◽  
The Impact

Abstract The aim of this work is the experimental investigation of the effects of the addition of water and urea into jet fuels, on the reduction of nitrogen oxides (NOx) emissions and eventually improvement of the lean flame stability in aeroengine combustors. Experiments have been carried out using a 300-kW liquid-fueled swirling combustor. Various urea and/or water concentrations have been tested at the same fuel/air ratio. In order to study the flame behavior, noninvasive optical diagnostic techniques, as charge-coupled device (CCD) cameras in different spectral ranges (visible and UV ranges, with different optical filters), have been adopted to analyze the shape and the brightness of the flame structure. Measurements of exhaust emissions (NOx, SO2, carbon monoxide (CO), CO2, and O2) have also been performed in order to evaluate the impact of emulsification on the entire combustion process. Finally, the thermal efficiency losses with respect to the neat jet test case were also analyzed for each emulsified fuel condition.

scholarly journals Pengaruh Variasi Arah Aliran Udara pada Stove terhadap Karak-teristik Pembakaran Wood Pellet

2020 ◽  
Vol 11 (3) ◽  
pp. 521-529
Author(s):  
Lilis Yuliati ◽  
◽  
David Simanungkalit
Keyword(s):  
Combustion Rate ◽  
Flame Temperature ◽  
Combustion Process ◽  
Axial Direction ◽  
Combustion Characteristics ◽  
Flame Height ◽  
Test Fluid ◽  
Wood Pellet ◽  
Injection Point ◽  
Temperature Combustion

This research was conducted to investigate the effect of inlet airflow direction on the combustion characteristics of a wood pellet stove. The direction of the airflow into the wood pellet stove is varied for four methods, namely inlet I, inlet II, inlet III, and inlet IV. At inlets, I, II, and III air is injected into the plenum in the radial direction with the injection points at r = -8, 0, and 8 cm respectively, whereas at inlet IV the direction of airflow into the plenum is in the axial direction with the injection point at r = 0. The combustion characteristics were observed in the wood pellet stove with a continuous fuel feeding system. The combustion characteristics investigated in this research consist of flame visualization, flame temperature, combustion rate, and the efficiency of the wood pellet stove. The results showed that wood pellet stoves with inlet IV had a lower combustion rate and flame height, however, this stove indicates a higher flame temperature and stove efficiency. Air entrance through the inlet IV induces most of the airflow to enter the combustion chamber through the primary channel, compared to that through the secondary and tertiary channels. The primary airflow through the wood pellet encourages a better devolatilization and combustion process. These conditions conduce the flame dimension which is a zone where the combustion reaction occurs is smaller with a higher flame temperature, due to higher volumetric heat release rate. This matter results in better heat transfer from the flame to the test fluid and higher stove efficiency.

Instability Control by Premixed Pilot Flames

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Peter Albrecht ◽  
Stefanie Bade ◽  
Arnaud Lacarelle ◽  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
Gas Turbines ◽  
Flame Structure ◽  
Premixed Flames ◽  
Combustion Process ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Lean Blowout ◽  
Acoustic Instabilities ◽  
Flame Behavior ◽  
The Impact

Premixed flames of swirl-stabilized combustors (displaced half-cone) are susceptible to thermo-acoustic instabilities, which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow, and other mechanisms. Pilot flames can alleviate this issue either by improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injections on the combustion stability is investigated. One of the pilot injector (pilot flame injector) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation showed that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blowout when a percentage of the fuel was premixed with air and injected through the pilot ring. NOx emissions were significantly reduced.

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