Experimental study of combustion inhibition by trimethyl phosphate in turbulent premixed methane/air flames using OH-PLIF

Abstract

The influence of turbulent fluctuation on combustion inhibition by trimethyl phosphate (TMP) is investigated in turbulent premixed methane/air flames. The instantaneous flame structures are detected by OH Planar Laser-Induced Fluorescence (OH-PLIF) system, and some statistical parameters, including the global consumption speed, mean fuel consumption rate and mean heat release rate, are attempted to quantify the inhibition effectiveness of TMP in the turbulent premixed flames. Results show that the turbulent combustion regime of the methane/air flame may be changed from the thin reaction zone (TRZ) to the distributed reaction zone (DRZ) regime, due to the high loading of inhibitor. The addition of agent can obviously decrease the turbulent consumption speed. Meanwhile, the relative inhibition efficiency of TMP in the turbulent flame is much lower than that in the laminar configuration. From the point view of reaction, one possible reason is that the difference of the turbulent transportation between the active radicals (H and OH) and the phosphorus-containing species (PO2, HOPO, HOPO2, etc.) may lead to decreasing the capacity of radical scavenging. By increasing the jet velocity, the mean fuel consumption rate and mean heat release rate decrease for the neat flames, but increase for the inhibited ones. The main reason is that the velocity increment is smaller than the increment of flame volume for the neat cases, but is larger than that for the doped configurations. Because of no consistent tendency, these two statistic variables may not the preferred parameters for the evaluation of turbulent flame inhibition.