Effects of CO2 Dilution on Flame Stabilization and NOx Emission in a Small Swirl Burner and Furnace

Abstract The 14 MW pilot–scale pulverized coal experiment system was built, pre-combustion characteristic and flame shape of adjustable axial swirl burner was investigation, and influence of swirl number also was discussed. The temperature and species concentration distribution in pre-combustion chamber showed that a high temperature oxygen-free and high CO concentration zone appeared around central pulverized coal, which enhanced burnout and inhibiting or reduction NOx. The pre-combustion characteristic belonged to high temperature preheating combustion technology. The captured flame image showed that flame shape beyond pre-combustion chamber outlet belonged to turbulent diffusion flame. Then flame shape scales were obtained. For different swirl numbers, ignition, wall temperature, mean maximum temperature, oxygen-free boundary and CO concentration was discussed, the results indicated that S=1.67 had advantaged for burnout and reduction NOx emission on the basis of stable ignition and avoiding high temperature corrosion. Mean flame length and diameter and divergence angle also were analyzed, the results showed that S=1.67 case had moderate flame length and best diameter and divergence. It was favorable for flame stability and high temperature region in furnace part, and increasing burnout and deceasing NOx emission. Therefor the optimal selection was S=1.67 case under experimental condition.

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

Fuel ◽

10.1016/j.fuel.2016.09.002 ◽

2017 ◽

Vol 201 ◽

pp. 124-135 ◽

Cited By ~ 25

Author(s):

Lukas G. Becker ◽

Hidemasa Kosaka ◽

Benjamin Böhm ◽

Samim Doost ◽

Robert Knappstein ◽

...

Keyword(s):

Experimental Investigation ◽

Flame Stabilization ◽

Swirl Burner

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

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2017-64794 ◽

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.

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

10.1115/gt2021-59744 ◽

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.

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

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-90215 ◽

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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