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Numerical Analyses of Hydrothermal Methanol Diffusion Flame in Supercritical Water: Hot and Warm Flames.

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Bibliographic Details
Title: Numerical Analyses of Hydrothermal Methanol Diffusion Flame in Supercritical Water: Hot and Warm Flames.
Authors: Saha, Sudipta1 (AUTHOR), Farouk, Tanvir1 (AUTHOR) tfarouk@sc.edu
Source: Combustion Science & Technology. 2026, Vol. 198 Issue 6, p1585-1607. 23p.
Subject Terms: *Flame, *Supercritical water, *Combustion, *Numerical analysis, *Flame temperature, *Oxidation, *Chemical kinetics
Abstract: In this study, the oxidation of methanol in a supercritical water medium has been numerically investigated. A two-dimensional axisymmetric computational model has been developed to conduct simulation over a range of fuel loading conditions using single and multi-step chemical kinetic scheme. The multi-step chemistry has been found to perform better than the single-step chemistry in predicting the flame temperature as well as its location and structure. It is found that the hydrothermal flame exhibits different flame structures depending on the fuel loading. For a higher fuel loading (XF = 0.12), a classical non-premixed hot flame was observed with a peak temperature of ~ 2000K. Whereas, for the leanest case (XF = 0.071), a peak temperature of ~ 1200K was observed with extremely low hydroxyl (OH) concentration (ranging to a few ppm levels). For high fuel loading, the flame forms on the jet periphery, while as the fuel loading decreases, the flame is observed to be lifted in the radial direction. At lower fuel loading, radial mixing is more prominent, and the multidimensional effect appears to be significant. Under this condition, the model predicts a peak concentration of ~ 300 ppm and ~ 1600 ppm of HO2 and H2O2, respectively, while the CO and CO2 concentrations become comparable and are distributed over a larger volume in a homogeneous fashion. This is counter to the hot flame where the CO profiles are located closer to the fuel-rich region and is dictated by the fuel-oxidizer diffusion. The CO-CO2 and the HO2-H2O2 profiles at the lowest fuel loading suggest the formation of a warm flame at supercritical conditions. Perturbation analysis was conducted to identify the impact of third-body collision efficiency of key species on the overall predictions. The predictions show that the flame formation and peak axial temperature are highly sensitive to the third body collision efficiency parameters – undergoing complete extinction or establishing a stable flame structure. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:In this study, the oxidation of methanol in a supercritical water medium has been numerically investigated. A two-dimensional axisymmetric computational model has been developed to conduct simulation over a range of fuel loading conditions using single and multi-step chemical kinetic scheme. The multi-step chemistry has been found to perform better than the single-step chemistry in predicting the flame temperature as well as its location and structure. It is found that the hydrothermal flame exhibits different flame structures depending on the fuel loading. For a higher fuel loading (XF = 0.12), a classical non-premixed hot flame was observed with a peak temperature of ~ 2000K. Whereas, for the leanest case (XF = 0.071), a peak temperature of ~ 1200K was observed with extremely low hydroxyl (OH) concentration (ranging to a few ppm levels). For high fuel loading, the flame forms on the jet periphery, while as the fuel loading decreases, the flame is observed to be lifted in the radial direction. At lower fuel loading, radial mixing is more prominent, and the multidimensional effect appears to be significant. Under this condition, the model predicts a peak concentration of ~ 300 ppm and ~ 1600 ppm of HO2 and H2O2, respectively, while the CO and CO2 concentrations become comparable and are distributed over a larger volume in a homogeneous fashion. This is counter to the hot flame where the CO profiles are located closer to the fuel-rich region and is dictated by the fuel-oxidizer diffusion. The CO-CO2 and the HO2-H2O2 profiles at the lowest fuel loading suggest the formation of a warm flame at supercritical conditions. Perturbation analysis was conducted to identify the impact of third-body collision efficiency of key species on the overall predictions. The predictions show that the flame formation and peak axial temperature are highly sensitive to the third body collision efficiency parameters – undergoing complete extinction or establishing a stable flame structure. [ABSTRACT FROM AUTHOR]
ISSN:00102202
DOI:10.1080/00102202.2025.2488831