scholarly journals Flame interactions in a stratified swirl burner: Flame stabilization, combustion instabilities and beating oscillations

2020 ◽  
Vol 212 ◽  
pp. 500-509 ◽  
Author(s):  
Xiao Han ◽  
Davide Laera ◽  
Dong Yang ◽  
Chi Zhang ◽  
Jianchen Wang ◽  
...  
Keyword(s):  
Flame Stabilization ◽  
Combustion Instabilities ◽  
Swirl Burner ◽  
Burner Flame

scholarly journals Influence of Heat Transfer and Material Temperature on Combustion Instabilities in a Swirl Burner

2016 ◽  
Vol 139 (5) ◽  
Author(s):  
Christian Kraus ◽  
Laurent Selle ◽  
Thierry Poinsot ◽  
Christoph M. Arndt ◽  
Henning Bockhorn
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Passive Control ◽  
Unstable Mode ◽  
Combustion Instabilities ◽  
Ambient Conditions ◽  
Swirl Burner ◽  
Helmholtz Resonators ◽  
Eddy Simulation ◽  
Limited Frequency

The current work focuses on the large eddy simulation (LES) of combustion instability in a laboratory-scale swirl burner. Air and fuel are injected at ambient conditions. Heat conduction from the combustion chamber to the plenums results in a preheating of the air and fuel flows above ambient conditions. The paper compares two computations: In the first computation, the temperature of the injected reactants is 300 K (equivalent to the experiment) and the combustor walls are treated as adiabatic. The frequency of the unstable mode (≈ 635 Hz) deviates significantly from the measured frequency (≈ 750 Hz). In the second computation, the preheating effect observed in the experiment and the heat losses at the combustion chamber walls are taken into account. The frequency (≈ 725 Hz) of the unstable mode agrees well with the experiment. These results illustrate the importance of accounting for heat transfer/losses when applying LES for the prediction of combustion instabilities. Uncertainties caused by unsuitable modeling strategies when using computational fluid dynamics for the prediction of combustion instabilities can lead to an improper design of passive control methods (such as Helmholtz resonators) as these are often only effective in a limited frequency range.

Influence of geometric and regime parameters on flame stabilization of a swirl burner

1999 ◽  
Vol 35 (5) ◽  
pp. 483-488 ◽  
Author(s):  
V. A. Arkhipov ◽  
O. V. Matvienko ◽  
E. A. Rudzei
Keyword(s):  
Flame Stabilization ◽  
Swirl Burner

Determination of Criteria for Flame Stability in an Annular Trapped Vortex Combustor

2015 ◽  
Author(s):  
Pradip Xavier ◽  
Mickael Pires ◽  
Alexis Vandel ◽  
Bruno Renou ◽  
Gilles Cabot ◽  
...  
Keyword(s):  
Driving Forces ◽  
Flux Ratio ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Stability Maps ◽  
The Rich ◽  
Acoustic Instabilities ◽  
Trapped Vortex

Development of lean premixed (LP) combustion is still a challenge as it results in considerable constraints for the combustor design. Indeed, new combustors using LP combustion are more prone to flashback, blow-off, or even thermo-acoustic instabilities. A detailed understanding of mechanisms leading to such extreme conditions is then crucial to reduce pollutant emissions, widen the range of operating conditions, and reduce design time. This paper reports the experimental study of an innovative LP trapped vortex combustor (TVC). The TVC concept uses a recirculating rich flow trapped in a cavity to create a stable flame that continuously ignites a main lean mixture passing above the cavity. This concept gave promising performances but some workers highlighted the existence of combustion instabilities for some operating conditions. Detailed studies have therefore been carried out in order to understand the occurrence of these drastic operating conditions. Results showed that the cavity flow dynamics in conjunction with the location of the interfacial mixing zone (between the cavity and the mainstream) were the driving forces to obtain stable combustion regimes. The goal of this work has been to take advantage of these detailed recommendations to determine stability maps, trends, and dimensionless parameters which could be easily used as early-design rules. For this reason, the study introduced a simple and robust criterion, based on the global pressure fluctuation energy. The latter was used to distinguish stable and unstable modes. An aerodynamic momentum flux ratio and a chemical stratification ratio (taken between the cavity and the mainstream) were defined to scale all measurements. Results indicated that the mainstream velocity was critically important to confine the cavity and to prevent combustion instabilities. Remarkably, this trend was verified and even more pronounced for larger cavity powers. In addition, flame stabilization above the cavity resulted in the existence of specific stratification ratios, in order to obtain a soft gradient of gas composition between the rich and lean regions. Finally, a linear relation between the mainstream and cavity velocities became apparent, thereby making possible to simply predict the combustor stability.

Experimental investigation of flame stabilization inside the quarl of an oxyfuel swirl burner

Fuel ◽  
2017 ◽  
Vol 201 ◽  
pp. 124-135 ◽  
Author(s):  
Lukas G. Becker ◽  
Hidemasa Kosaka ◽  
Benjamin Böhm ◽  
Samim Doost ◽  
Robert Knappstein ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flame Stabilization ◽  
Swirl Burner

Experimental Analysis of Confinement and Swirl Effects on Premixed CH4-H2 Flame Behavior in a Pressurized Generic Swirl Burner

2017 ◽  
Author(s):  
Jon Runyon ◽  
Richard Marsh ◽  
Daniel Pugh ◽  
Philip Bowen ◽  
Anthony Giles ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Kinetic Modelling ◽  
Dynamic Pressure ◽  
Flame Stabilization ◽  
Combustion Noise ◽  
Combustion Stability ◽  
Acoustic Response ◽  
Swirl Burner ◽  
Swirl Number

The introduction of hydrogen into natural gas systems for environmental benefit presents potential operational issues for gas turbine combustion and power generation applications; in particular acceptable blending concentrations are still widely debated. The use of a generic swirl burner under conditions pertinent to a gas turbine combustor is therefore advantageous to (i) provide evidence of potential design modifications to inform future gas turbine operation on hydrogen blends and (ii) validate numerical model predictions. Building on a previous experimental combustion database consisting of methane-hydrogen fuel blends under atmospheric and elevated ambient conditions, a new scaled generic swirl burner has been designed for experimental investigation of flame stability and exhaust gas emissions at combustor inlet temperatures to 573 K, pressures to 0.33 MPa, and thermal powers to 126 kW. The geometry downstream of the modular burner is developed further to enable separate investigation under isothermal and combustion conditions of the influence of combustor outlet geometry and the effect of changing geometric swirl number. The burner confinement is modified to include both a cylindrical exit quartz combustion chamber and a conical convergent exit quartz combustion chamber, designed to provide a more representative geometric and acoustic boundary at the combustor outlet. Two inlet geometric swirl numbers of industrial relevance are chosen; namely 0.5 and 0.8. Combustion stability and heat release locations of lean premixed CH4-air and CH4-H2-air combustion are evaluated by a combination of OH planar laser induced fluorescence, OH* chemiluminescence, and dynamic pressure measurements. Changes in flame stabilization location are characterized by the use of an OH* chemiluminescence intensity centroid. Notable upstream flame movement coupled with changes in acoustic response are evident, particularly near the lean operating limit as hydrogen blending shifts lean blowoff of methane flames to lower equivalence ratios with corresponding reduction in NOx emissions. The influence of increased pressure on the lean operating point stability and emissions appear to be small over the range considered, however a power law correlation has been developed for scaling combustion noise amplitudes with inlet pressure and swirl number. Indicators of flame flashback as well as combustor acoustic response are affected considerably when the convergent combustor outlet geometry is deployed. This has been shown to alter the influence of the central recirculation zone as a flame stabilizing coherent flow structure. Chemical kinetic modelling supports the experimental observations that stable burner operation can be achieved with blended methane-hydrogen up to 15% by volume.

Combustion Instabilities and Control of a Multiswirl Atmospheric Combustor

2006 ◽  
Vol 129 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Tongxun Yi ◽  
Ephraim J. Gutmark
Keyword(s):  
Flame Stabilization ◽  
Inlet Temperature ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Factors Affecting ◽  
Thermoacoustic Instability ◽  
Lean Blowout ◽  
Air Inlet ◽  
Swirl Intensity ◽  
And Control

Thermoacoustic instability and lean blowout (LBO) are investigated experimentally in an atmospheric swirl-stabilized combustor fueled with gaseous propane. Factors affecting combustion instability are identified. Sinusoidal or steady air forcing of either the swirling air shear layer or the fuel line, with less than 1.0% of combustion air, can reduce pressure oscillations amplitude by more than 20dB. Phase-shifted close-loop air forcing of the flame can reduce the pressure oscillations amplitude by 13dB. For a constant air flow rate and air inlet temperature, initially smooth turbulent combustion exhibits relatively intense heat release oscillations with decreasing equivalence ratio, followed by a quiet state before blowout. High outer swirl intensity and a rich burning flame stabilization region can effectively extend the LBO limit.

Combustion of Hydrogen-Methane-Air-Mixtures in a Generic Triple Swirl Burner: Numerical Studies

2021 ◽  
Author(s):  
Neha Vishnoi ◽  
Agustin Valera-Medina ◽  
Aditya Saurabh ◽  
Lipika Kabiraj
Keyword(s):  
Hydrogen Content ◽  
Energy Demand ◽  
Combustion Process ◽  
Flow Fields ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Temperature Fields ◽  
Nox Emissions ◽  
Swirl Burner ◽  
High Hydrogen

Abstract Ever-increasing energy demand, limited non-renewable resources, requirement for increased operational flexibility, and the need for reduction of pollutant emissions are the critical factors that drive the development of next generation fuel flexible gas turbine combustors. The use of hydrogen and hydrogen-rich fuels such as syngas helps in achieving decarbonisation. However, high temperatures and flame speeds associated with hydrogen might increase the NOx emissions. Humidified combustion presents a promising approach for NOx control. Humidification inhibits the formation of NOx and also allows for operating on hydrogen and hydrogen-rich fuels. The challenge in the implementation of this technology is the combustor (burner) design, which must provide a stable combustion process at high hydrogen content and ultra-wet conditions. In the present work, we investigate the flow field and combustion characteristics of a generic triple swirl burner running on humidified and hydrogen enriched methane-air mixtures. The investigated burner consists of three co-axial co-rotating swirling passages: outer radial swirler stage, and two inner concentric axial swirler stages. Reynold’s Averaged Navier-Stokes (RANS) simulation approach has been utilized here for flow description within the burner and inside the combustor. We present the flow fields from isothermal and lean pre-mixed methane-air reactive simulations based on the characterization of velocity profiles, streamwise shear layers, temperature fields and NOx emissions. Subsequently, we investigate the effect of combustion on flow fields, and flame stabilization for hydrogen enriched methane-air mixtures as a function of hydrogen content. We also investigate the effect of humidified combustion on methane-hydrogen blends and present comparison of temperature estimations and NOx emissions.

Characterization of ALM Swirl Burner Surface Roughness and its Effects on Flame Stability Using High-Speed Diagnostics

2019 ◽  
Author(s):  
Jon Runyon ◽  
Anthony Giles ◽  
Richard Marsh ◽  
Daniel Pugh ◽  
Burak Goktepe ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Post Processing ◽  
Swirl Burner ◽  
Stability Limits ◽  
Near Wall

Abstract The use of metallic Additive Layer Manufacturing (ALM) is an active area of development for gas turbine components, particularly concerning novel combustor prototypes for micro gas turbines. However, further study is required to understand the influence of this manufacturing technique and subsequent post-processing on the resulting burner component surface roughness and its effect on flame stability. In this study, two Inconel 625 swirl nozzle inserts with identical bulk geometry (swirl number, Sg = 0.8) were constructed via ALM for use in a generic gas turbine swirl burner. Further post-processing by grit blasting of one swirl nozzle insert results in a quantifiable change to the surface roughness characteristics in the burner exit nozzle when compared with the unprocessed ALM swirl nozzle insert or a third nozzle insert which has been manufactured using traditional machining methods. An evaluation of the influence of variable surface roughness effects from these swirl nozzle inserts is therefore performed under preheated isothermal and combustion conditions for premixed methane-air flames at thermal power of 25 kW. High-speed velocimetry at the swirler exit under isothermal air flow conditions gives evidence of the change in near-wall boundary layer thickness and turbulent fluctuations resulting from the change in nozzle surface roughness. Under atmospheric combustion conditions, this influence is further quantified using a combination of dynamic pressure, high-speed OH* chemiluminescence, and exhaust gas emissions measurements to evaluate the flame stabilization mechanisms at the lean blowoff and rich stability limits. Notable differences in flame stabilization are evident as the surface roughness is varied, and changes in rich stability limit were investigated in relation to changes in the near-wall turbulence intensity. Results show the viability of using ALM swirl nozzles in lean premixed gas turbine combustion. Furthermore, precise control of in-process or post-process surface roughness of wetted surfaces can positively influence burner stability limits and must therefore be carefully considered in the ALM burner design process as well as CFD models.

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