Spectral characterisation of non-premixed H₂/CO₂ jet flames
File(s)
Published version
Author(s)
Chen, Chaoxu
Taylor, Alex MKP
Hardalupas, Yannis
Type
Journal Article
Abstract
The impact of CO2 addition on the appearance and spectral characteristics of H2-fuelled flames was examined in two types of non-premixed jet flames, namely constant heat release rate and constant fuel jet exit velocity. The CO2 volumetric fraction in the fuel stream was varied between 0 and 60%. Flame images and spectra for wavelengths 270–850 nm were acquired using a digital colour camera and a spectrograph, respectively. For both flame types, CO2 addition introduced broadband CO2* chemiluminescence with prominent intensities in the blue range, owing to the chemical participation of CO2 in combustion. It also suppressed OH* chemiluminescence and emissions from water molecules because of the thermal and chemical impact of CO2. Consequently, CO2 addition led to a flame colour change from slightly red-dominated for pure H2 flames to strongly blue-dominated, enhancing flame visibility by up to 4 times. The intensity of CO2* chemiluminescence reached a maximum for 40–50% CO2 volumetric fraction for both flame types. Spectral intensities were evaluated for three selected wavelength bands, namely OH (305–315 nm), blue (400–540 nm), and IR (720–850 nm). The intensity ratios of three band combinations, namely blue/OH, blue/IR and OH/IR, demonstrated independence of the flame type and monotonic correlations with the CO2 volumetric fraction, highlighting their potential application for industrial real-time monitoring of H2/CO2 blending ratio in non-premixed H2/CO2 flames. Flame height, evaluated from flame images, increased with CO2 addition for laminar jet flames but decreased with increasing CO2 addition for turbulent jet flames, regardless of flame type.
Date Issued
2026-10-15
Date Acceptance
2026-03-13
Citation
Fuel, 2026, 422
ISSN
0016-2361
Publisher
Elsevier BV
Journal / Book Title
Fuel
Volume
422
Copyright Statement
© 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ).
License URL
Publication Status
Published
Article Number
139148
Date Publish Online
2026-03-19