Influence of [formula omitted] oxidizer blends on soot formation and radiative heat flux in PMMA-air 2D slab burner for understanding hybrid rocket combustion

Abstract

The focus of this study is to establish a correlation between the flame to fuel incident radiative heat flux (RHF) in 1D steady-state diffusion flames to non-intrusively measured RHF in 2D slab burner experiments for a range of O2/N2 oxidizer blends. Slab burner experiments are conducted for a range of increasing O2 concentrations from 17% to 100% in the oxidizer stream. Non-intrusive two-color pyrometry is used to determine flame temperature, soot volume fraction, and flame to fuel surface RHF. Measurements and modeling confirm soot volume fraction attains a local maximum for an O2 concentration of 45%. Low-strain diffusion flame modeling shows the reason for the local maximum is the relative location of the soot formation/nucleation fronts relative to oxidation which decreases with increasing O2 concentration. Overall good agreement between modeling and measurements of radiative heat flux to the fuel is observed for the fuel and range of O2 concentrations considered. These results demonstrate the viability of using flamelet modeling approaches for describing hybrid rocket motors.