OH-PLIF investigation of Y2O3-ZrO2 coating improving flame stability in a narrow channel

The chemical catalytic performance of functional ceramics materials of rare earth is of great technological and scientific significance to actively regulate the flame-wall interaction in high-temperature combustion. The premixed methane-air flames in a slot burner with different wall materials were characterized by OH-PLIF technique to gain an insight into the effects of heterogeneous chemistry at gas–solid interfaces on the flame characteristics. The 304STS wall coated with ZrO2 and Y2O3-ZrO2 respectively through atmospheric plasma spray were investigated at the wall temperatures of 473 K and 773 K in this paper. The flame stability was quantitatively analyzed through the dynamic flame morphology of OH-PLIF images. The absolute maximum OH intensities in the flame cores were extracted to investigate the effects of different gap distances, wall temperatures and surface materials. The characterization of chemical interactions between flame and wall was also carried out based on the spatial distribution of OH radicals near the wall. Lastly, the heterogeneous chemistry between the gas-phase radicals in flame with the electrophilic oxygen species on the surface of Y2O3-ZrO2 coating was discussed to reveal the dominant pathways of the reduction and re-oxidation of surface lattice oxygen. Results show that a marked improvement in combustion stability was observed with using Y2O3-ZrO2 coated walls compared to the uncoated 304STS walls under the same conditions. The maximum OH intensity in flame would increase with the decrease of channel gap at higher temperature due to the unique chemical promoting effect of Y2O3-ZrO2 coating. Overall, this work indicates that coating with rare earth composite metal oxides such as Y2O3-ZrO2 can potentially serve as an effective strategy for the optimization of combustion chambers.