Analysis of Pressure Effect on Three-Dimensional Flame Surface Density Estimation

In experiments, flame surface density (FSD), defined as flame area per volume, is usually approximated by its two-dimensional (2D) value, as flame length per area. However, this approximation may underestimate the flame wrinkle due to the presence of a fluctuating component outside the measurement plane. Obtaining a three-dimensional (3D) flame surface density (FSD) from experiments is challenging, but it can be estimated from low-dimensional measurements under certain assumptions. Models used to estimate 3D FSD can be significantly affected by ambient pressure, as high pressure can cause a substantial decrease in small flame front scales. In this study, a CH4/air premixed turbulent flame is stabilized on a Bunsen burner and measured using the OH-PLIF technique at pressures up to 1.0 MPa. The flame front is extracted with an in-house auto adaptive threshold binarization code. Different models estimating 3D FSD with the corresponding assumptions are summarized from the definition of FSD. The reliability of the assumptions under different pressures is investigated and analyzed. The models are compared through analyzing the assumptions, and are tested in terms of global fuel consumption. The pressure’s effect on the reliability of the models could provide an essential improvement in the context of modeling turbulent combustion.