Dolai, A and Ravikrishna, RV (2023) Assessment of MILD combustion in co/counter-swirl configuration using syngas as a fuel. In: International Journal of Hydrogen Energy, 49 .
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Abstract
Moderate or intense low oxygen dilution (MILD) combustion is investigated in a co/counter-swirl using OH�-chemiluminescence, species measurements, OH planar laser-induced fluorescence (OH-PLIF), two-dimensional particle image velocimetry (2D-PIV), and microphone measurements. Experiments are performed in a two-stage combustor, where the first stage of combustor is catalytic stage and the second stage is the swirl stage (co/counter-swirl configuration). A fuel-rich syngas (20 H2, 20 CO, 12 CO2, 2 CH4, and 46 N2) reacts with air in the catalytic stage. Then, the mixture of unconsumed syngas and products of catalytic combustion is supplied to the swirl stage where the mixture is burnt with oxidizer with varied oxygen concentration. The flame in the swirl stage is established by two concentric swirling streams where the inner stream is the hot gases from the catalytic stage, and the outer stream is the oxidizer. Co/counter-swirl flames are generated by changing the swirl direction of the inner stream. After achieving a stable flame, the macrostructure, flame steadiness, CO and NOx emissions, reaction zone distribution, and sound pressure level (SPL) are investigated at several oxygen concentrations (O2 = 13.13 �21 ) with an aim to assess the MILD combustion mode in co/counter-swirl configuration. As the oxygen percentage decreases, the flame luminosity decreases for both co/counter-configuration. However, the reduction in luminosity is profound for co-swirl configuration. Clear distinctions between co and counter-swirl configurations are observed regarding flame height and stand-off height. Two-dimensional particle image velocimetry (2D-PIV) is utilized to understand these trends. The steadiness of the flame is investigated using standard deviations (SD) of OH�-chemiluminescence images and global luminosity (I(t)). The flame steadiness is found to be improved as the oxygen concentration decreases. The OH-PLIF indicates the distributed nature of combustion. The NOx emission is found to be extremely low in all studied cases; however, the CO emission shows an increasing trend when O2 reduces. Finally, the sound pressure level and the dynamics stability are investigated using microphone measurements. The SPL decreases by �3 dB and �7 dB for the counter-swirl and co-swirl configuration, respectively. Furthermore, the frequency domain analysis suggests that the fundamental axial mode of the combustor is excited at high oxygen concentration. However, the unsteady combustion and chamber acoustics become decoupled at lower O2 concentrations. Thus, the present paper, for the first time, confirms that MILD combustion can be achieved in co/counter-swirl configuration, provided the oxygen concentration is low (�13 ). The present study also establishes that the co-swirl configuration is more suitable than the counter-swirl for achieving the MILD combustion mode. © 2023 Hydrogen Energy Publications LLC
| Item Type: | Journal Article |
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| Publication: | International Journal of Hydrogen Energy |
| Publisher: | Elsevier Ltd |
| Additional Information: | The copyright for this article belongs to Author |
| Keywords: | Catalysis; Combustion; Combustors; Flow visualization; Fluorescence; Gas emissions; Laser optics; Laser produced plasmas; Luminance; Nitrogen oxides; Oxygen; Synthesis gas; Velocimeters; Velocity measurement, Co/counter-swirl; Image velocimetry; Low oxygen; Moderate or intense low oxygen dilution; Non-premixed; Non-premixed mode; Oxygen dilution; Particle image velocimetry; Particle images; Planar laser-induced fluorescence, Chemiluminescence |
| Department/Centre: | Division of Mechanical Sciences > Mechanical Engineering |
| Date Deposited: | 04 Mar 2024 09:41 |
| Last Modified: | 04 Mar 2024 09:41 |
| URI: | https://eprints.iisc.ac.in/id/eprint/84393 |
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