Enhanced Flame Stability Research Articles

Experimental evaluation and mechanism analysis of combustion performance enhancement in composite wall-assisted methane/air mixtures

Experimental evaluation and mechanism analysis of combustion performance enhancement in composite wall-assisted methane/air mixtures

Experimental and numerical modeling of co-combustion of biomass gasification gas and natural gas in a non-premixed burner

Experimental and numerical modeling of co-combustion of biomass gasification gas and natural gas in a non-premixed burner

Innovative eco-friendly design solutions for energy demands using swirl- induced burner by jets

Innovative eco-friendly design solutions for energy demands using swirl- induced burner by jets

Flame structure and stability for gradient magnetic field enhanced non-premixed combustion of highly diluted methane with nitrogen

Flame structure and stability for gradient magnetic field enhanced non-premixed combustion of highly diluted methane with nitrogen

Three-dimensional diagnosis of lean premixed turbulent swirl flames using tomographic background oriented Schlieren

The necessity of minimizing NOx emissions drives the pursuit of ultra-lean premixed combustion in aeroengines and gas turbines, characterized by susceptibility to combustion instabilities. To tackle this issue, swirling flow design is widely incorporated into lean premixed combustor design, enhancing flame stability, and shortening flame length. This study utilizes the tomographic background-oriented Schlieren (TBOS) to reconstruct the spatial distribution of the refractive index gradient of lean premixed turbulent swirl flames with an aeroengine combustor configuration. A parametric study of the TBOS reconstruction quality is conducted, and the results reveal that view sparseness primarily degrades the reconstruction quality compared to the specific iterative algorithm used. The classic visual hull approach is explored to address this challenge, highlighting the significance of visual hull size. Furthermore, to improve the reconstruction quality, a posterior support constraint method is proposed, involving the removal of voxels of nearly constant refractive index within the central volume surrounded by flames. Results demonstrate that implementing this posterior support constraint further improves the reconstruction quality of lean premixed turbulent swirl flames. Finally, the robustness of this posterior support constraint method is validated by introducing high-level noise to the light deflection data, showcasing the potential of combining the dedicated designed visual hull and proposed posterior support constraint in addressing the view sparseness challenge for TBOS measurements.

Combustion and emission performance evaluation in ammonia/hydrogen-powered system with baffle and secondary injection applied

Combustion and emission performance evaluation in ammonia/hydrogen-powered system with baffle and secondary injection applied

Characterizing turbulent non-premixed flame structure and pollutant formation of cracked ammonia jet flames using simultaneous NH and NO PLIF

Characterizing turbulent non-premixed flame structure and pollutant formation of cracked ammonia jet flames using simultaneous NH and NO PLIF

Effects of syngas and methanol fuel substitution on ammonia counterflow diffusion flames

Effects of syngas and methanol fuel substitution on ammonia counterflow diffusion flames

Investigation of the influence of the bluff-body temperature on a lean premixed DME/air flame approaching blowoff

Investigation of the influence of the bluff-body temperature on a lean premixed DME/air flame approaching blowoff

Experimental study on the characteristics of a novel aerodynamic wake width flameholder

Experimental study on the characteristics of a novel aerodynamic wake width flameholder

Experimental and kinetic analyses on the flame dynamics and stabilization of ammonia/hydrogen-air mixtures in a micro-planar combustor

Experimental and kinetic analyses on the flame dynamics and stabilization of ammonia/hydrogen-air mixtures in a micro-planar combustor

Experimental and simulation study on the combustion characteristics of ammonia/n-dodecane mixtures

Experimental and simulation study on the combustion characteristics of ammonia/n-dodecane mixtures

Experimental and numerical analysis of ammonia/hydrogen combustion under artificial exhaust gas recirculation

Experimental and numerical analysis of ammonia/hydrogen combustion under artificial exhaust gas recirculation

Large-Eddy Simulation of swirled flame stabilisation using NRP discharges at atmospheric pressure

Large-Eddy Simulation of swirled flame stabilisation using NRP discharges at atmospheric pressure

OH-PLIF study on the mechanism regulating flame-wall interaction with catalytically active CeO2-ZrO2 coatings

OH-PLIF study on the mechanism regulating flame-wall interaction with catalytically active CeO2-ZrO2 coatings

Experimental and numerical study on the laminar flame characteristics for PODE3 and PODE3/iso-octane blends under elevated and sub-ambient initial pressures

• The laminar burning speeds for PODE 3 under different initial pressures are tested. • The laminar burning speeds for PODE 3 / iso -octane blends are investigated. • The accuracy of mechanism for PODE 3 and PRF/PODE n is validated. • The Markstein length and laminar flame instability are analyzed in detail. Polyoxymethylene dimethyl ether (PODE n ) is a promising alternative fuel for diesel due to its high oxygen contents (>40%) and high cetane number, thereby improving the thermal efficiency and reducing the pollutant emissions caused by the internal combustion engine. This study investigated the laminar burning speeds and Markstein length for PODE 3 and PODE 3 / iso -octane blends at wide equivalence ratios (0.7–1.6) and initial temperature of 408 K under elevated and sub-ambient initial pressures (0.5–4 bar) in a cylindrical constant-volume combustion vessel with high-speed Schlieren photography method combined with the nonlinear extrapolation model. The numerical simulation was also carried out to validate the accuracy of the mechanisms of PODE 3 and primary reference fuel (PRF)/PODE n blends and analyze the reaction sensitivities and the mole fraction profiles of key species. In addition, flame instability was discussed experimentally and theoretically. The results show that the laminar burning speed for PODE 3 decreases with the initial pressure, and the laminar burning speed for PODE 3 / iso -octane basically accords with the linear relationship to the PODE 3 volume fractions. The findings indicate that the kinetic effect has a dominant impact on the laminar burning speed for PODE 3 when compared with the thermal effect. The results also reveal that the Markstein length is negative only at an equivalence ratio between 1.5 and 1.6 under P = 2 bar, indicating that PODE 3 has more enhanced flame stability. Furthermore, the flame instability decreases with the increase of PODE 3 volume fractions, increases with the increase of initial pressure, and increases with the increase of the equivalence ratio. The differences between experimental results and theoretical results including the Markstein length, the critical radius and the critical Peclet number might be explained by the stretch rate results.

Stratified Flames in Dual Annular Counter-Rotating Swirl Burner for Wider Operability Gas Turbines

Abstract This study investigates numerically the effects of equivalence ratio (Φ) on flow/flame interactions and emissions of stratified oxy-methane (CH4/O2/CO2) flames in a dual annular counter-rotating swirl (DACRS) burner for wider operability and environmental-friendly gas turbines. The flow mixture entering the combustor is split into two coaxial streams of different equivalence ratios. The central stream is characterized by higher Φ to continuously ignite the flame for enhanced flame stability, whereas the annular stream is a highly lean mixture to sustain the environmental performance of the combustor. The partially premixed combustion model is adopted in the ansys-fluent 2021-r1 software to model the reaction kinetics of the generated stratified flames in the two-dimensional axisymmetric domain. Nine cases of the same inlet velocity ratio (primary stream to secondary stream) of 3.0 are examined at a fixed oxygen fraction (OF: volumetric percentage of oxygen in the O2/CO2 mixture) of both streams of 30%. Flame stratification is achieved by varying the equivalence ratios of the primary (Φp = 0.9, 0.8, and 0.7) and secondary (Φs = 0.7, 0.55, and 0.4) streams. The results indicate effective flame/flow interactions, complete combustion, and reduced emissions for the DACRS stratified flames.

Dynamic and kinetic studies on the oxy-coal combustion using multi-parameter high-speed diagnostics

• Homogeneous ignition and reaction control Zhundong coal combustion upstream. • The heterogeneous reaction occurs upstream but dominates burning processes downstream. • The release and combustion of volatiles strongly affect flame stability. • Optical kinetic data are obtained based on an Arrhenius expression. Non-intrusive measurement of dynamic and kinetic parameters during oxy-coal combustion has been carried out in an enclosed downward laminar flow reactor. High-speed OH-PLIF, CH* chemiluminescence, and pyrometer were used to determine the luminescence species, particle velocity, and particle temperature. A two-step model was established to predict the release of coal combustible based on the Arrhenius expression. The experimental data from traditional coal char analysis methods verified the optical kinetic model. Experiments showed that homogeneous ignition first occurred and dominated the upstream volatile combustion. The heterogeneous reaction was activated upstream due to volatile oxidization and became dominant downstream. The coal combustion formed an overlapping region between volatile and char oxidations. This region played a critical role in enhancing flame stability. The duration of the overlapping region was smaller in oxy-fuel combustion than in air-alike combustion due to the higher reaction rate and lower heat and mass diffusion. A temperature-dependent kinetic model was found to obey a two-step first-order Arrhenius expression with two pre-exponential factors ( 10 3.59 ± 0.22 and 10 5.81 ± 0.31 s −1 ) and two activation energies (173.1 and 278.0 kJ/mol) in air-alike combustion, and two pre-exponential factors ( 10 5.02 ± 0.47 and 10 6.37 ± 0.24 s −1 ) and two activation energies (217.0 and 291.1 kJ/mol) in oxy-fuel combustion. The kinetic predictions agree well with the experimental results of the combustible release in the corresponding tests.

A comparative study of gaseous fuel flame characteristics for different bluff body geometries

Flame stabilization by a bluff-body is commonly used in many combustion applications to improve mixture characteristics, enhance flame stability and assist in combustion control. The main objectives of the present experimental work are concerned with studying the flame stabilization and combustion characteristics of Liquefied Petroleum Gas (LPG) with different bluff body shapes and sizes. An experimental test rig that consists of a gaseous fuel line, compressed air line, mixing chamber and burner is designed and constructed. Different bluff body shapes such as disc, cone, V-gutter, horizontal and vertical cylinders are used. The effects of different Blockage Ratios (B.R.) of 0.25, 0.35, 0.45, and 0.55 are studied at a constant equivalence ratio (Փ) of 1.85 for different bluff body shapes. The blowoff limits, temperature distributions, flame shapes, exhaust species concentrations and visible flame length are experimentally measured and discussed. The results indicated that increasing the blockage ratio leads to increasing the maximum flame temperature, increasing the flame diameter, and decreasing the flame length for all bluff body shapes. The centerline axial NO concentration has its peak values coincide with the maximum centerline axial temperatures. The flame using bluff body cone is more stable than using other bluff body shapes i.e., it has wide flammability limits or a wide range of operating conditions.

Experimental determining flame characteristic of premixed methane/air mixtures in a microchannel supported with Pt/Al2O3/Ni catalyst

To enhance premixed methane/air combustion that occurs under micro-scale conditions, this work considers applying Pt/Al2O3-based catalyst in a rectangular-shaped combustor with the nickel foam surface. The effects of the inlet velocity, equivalence ratio and catalyst loading concentrations are experimentally evaluated and analyzed. The results show that with the implementation of such catalysts, flame structure becomes more stable, and the flammable range of the mixture is also widened. Meanwhile, the thermal coupling between the gas phase flame and the solid wall is more intense. In addition, with the increase in the catalyst loading mass fraction, the transition point from u-shaped flame to inclined flame was found near the entrance of the combustion chamber, which can remain a stable state over a wide operating time in the micro-channel. The catalytic combustion in enhancing flame stability becomes more effective with the increase of Pt loading mass fraction. In general, the findings gained from this study shed light on the mechanism of designing a stable combustion system by implementing a suitable catalyst.