Abstract
This study is focused on the characterization of wall heat fluxes and its influence upon CO formation/oxidation within atmospheric flames in a side-wall quenching geometry. The influence of different wall temperatures ranging between 330 K and 670 K is compared for stoichiometric methane and dimethyl ether (DME) flames. Coherent anti-Stokes Raman spectroscopy (CARS) and two-photon laser induced fluorescence (LIF) of the CO molecule are used to determine pointwise gas phase temperatures and CO concentrations. Simultaneously, wall temperatures are measured using one-dimensional phosphor thermometry and flame front positions are identified by planar OH-LIF imaging. Wall heat fluxes are estimated from measured gas and wall temperatures. For increasing wall temperatures, quenching distances decrease significantly and the maximum wall heat fluxes rise in the quenching region. Additionally, thermochemical states are analysed using CO/T scatter plots. Compared to one-dimensional unbounded laminar flame calculations, the CO/T dependencies are altered significantly by the presence of a wall. Very close to the wall, for methane/air flames and to a lesser extent for DME/air flames at y = 100 µm, the CO formation branch is shifted towards lower temperatures. In contrast, in the entire near-wall region the CO oxidation branch is shifted to lower temperatures for both fuels. One-dimensional premixed flame calculations accounting for enthalpy losses indicate that the heat loss to the wall is the most likely cause rather than different chemical reaction pathways. Studying the impact of turbulence, both the CO formation and oxidation branch are shifted to lower temperatures in state space. Additionally, an increasing number of intermediate CO mole fractions is observed filling the state space in between both branches. The analysis of turbulent integral time scale derived from PIV data indicates that this phenomenon is dominated by heat transfer, which is enhanced by turbulence.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.