Heat flux measurements in stagnation point methane/air flames with thermographic phosphors |
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Authors: | Mohamed Salem Susanne Staude Ulf Bergmann Burak Atakan |
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Institution: | 1. Thermodynamik, IVG, Faculty of Engineering, and CeNIDE (Center for Nanointegration Duisburg-Essen), Universit?t Duisburg-Essen, Lotharstr. 1, 47057, Duisburg, Germany
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Abstract: | Light-induced phosphorescence from thermographic phosphors was used to study the wall temperatures and heat fluxes from nearly
one-dimensional flat premixed flames. The investigated flames were stoichiometric, lean and rich laminar methane/air flames
with equivalence ratios of φ = 1, φ = 0.75 and φ = 1.25 at ambient pressure. The flames were burning in a stagnation point
arrangement against a water-cooled plate. The central part of this plate was an alumina ceramic plate coated from both sides
with chromium-doped alumina (ruby) and excited with a Nd:YAG laser or a green light-emitting diode (LED) array to measure
the wall temperature from both sides and thus the heat flux rate from the flame. The outlet velocity of the gases was varied
from 0.1 to 1.2 m/s. The burner to plate distance (H) ranged from 0.5 to 2 times the burner exit diameter (d = 30 mm). The measured heat flux rates indicate the change of the flame stabilization mechanism from a burner stabilized
to a stagnation plate stabilized flame. The results were compared to modeling results of a one-dimensional stagnation point
flow, with a detailed reaction mechanism. In order to prove the model, gas phase temperatures were measured by OH-LIF for
a stoichiometric stagnation point flame. It turns out that the flame stabilization mechanism and with it the heat fluxes change
from low to high mass fluxes. This geometry may be well suited for further studies of the elementary flame wall interaction. |
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