Thermochemical states of a turbulent, lean premixed dimethyl ether/air flame were assessed for the first time using simultaneous measurements of gas temperature T , CO(2 )and CO mole fractions with locations as close as 120 mu m above the quenching wall. This is realized by combined dual-pump coherent anti Stokes Raman spectroscopy (DP-CARS) and two-photon laser-induced fluorescence (LIF) of CO. In addition to thermochemical states, the flow and flame dynamics were measured separately using a combined two component particle image velocimetry (PIV) and planar LIF of the OH radical at high (4 kHz) and low (50 Hz) repetition rates. The data from the independent measurements was linked by the instantaneous flame front topologies, determined by the qualitative OH-LIF in both experiments. The grid-generated turbulence intensity was found to be relatively low in the bulk flow ( - 4 . 5% , streamwise velocity component) with the turbulent flame classified within the regime of wrinkled flamelets (w /sL between 0.3 and 0.75, for streamwise velocity component). The flame-wall interaction could be assigned to either a side-wall quenching (SWQ)-like ( - 50% ) or a head-on quenching (HOQ)-like scenario ( - 50% ), with a transition between these scenarios taking place within a few milliseconds. The thermochemical states depend significantly on whether a SWQ-like or a HOQ-like scenario is present. Here, the thermochemistry of the SWQ-scenario is studied in detail, and three zones, A, B, C, could be distinguished in the state space on the basis of the (CO2, T ) correlations. Zone A is characterized by strong wall heat losses and mixing influences, while zone B features less pronounced wall heat losses and mixing processes. In zone C the impacts of turbulence almost completely disappear and conditions comparable to a laminar near-wall flow are observed. The distinguishability of the three zones in the (CO,T) or (CO,CO2) correlations is less clear, which underlines the importance of the additional CO2 measurement in the DP-CARS methodology.(C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
