Effect of the stagnation plate on PAHs, soot and OH distributions in partially premixed laminar flames fueled with a blend of n-heptane and toluene

The stagnant plate influence on spatial distributions of polycyclic aromatic hydrocarbons (PAHs), soot and hydroxyl radical (OH) in the surrogate fuel (80% n-heptane and 20% toluene in volume) partially premixed flame on a McKenna burner were originally investigated in terms of different plate heights above the burner (H-p) and plate temperatures (T-p). Both PAHs and OH distributions were qualitatively measured by laser-induced fluorescence (LIF) and soot volume fraction field was quantitatively measured by two-color laser-induced incandescence (2C-LII). It is found that the LIF intensity of 2&3-ring aromatics (A2&A3) and 4-ring aromatics (A4) and soot volume fraction firstly increase and then reduce when the Hp is set from 35 to 10 mm. The variation tendency transition happens between H-p = 20 and 25 mm. In contrary, OH-LIF intensity gradually decreases as the Hp decreases. On the other hand, the T-p has an opposite effect on the A2&A3-LIF, A4-LIF and soot volume fraction variation tendency at two H-p. At H-p = 15 mm, A2&A3LIF, A4-LIF and soot volume fraction increase as the T-p increases. However, A2&A3-LIF, A4-LIF and soot volume fraction decrease with the rise of the T-p at H-p = 35 mm. Interestingly, OH-LIF intensity always increases as the T-p rises at any H-p. Therefore, it can be concluded that the PAHs-LIF intensity and soot volume fraction depend on the H-p and T-p, and the maximums of them would be reached at the specific H-p and T-p. While both the H-p and T-p have a monotonic effect on the OH-LIF intensity. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The study found that the spatial distributions of PAHs, soot, and OH are influenced by plate height and temperature in a surrogate fuel flame. PAHs and soot are more affected by plate height and temperature, while OH is more affected by monotonic changes in plate height and temperature.