Optical visualization of hypergolic burning spray structure using blue light spectrum

In this study, we focused on a novel methodology involving the optical visualization of a hypergolic burning spray. A hypergolic propellant, comprising 95 wt% H2O2 and an amine-based fuel, was injected using pentad impingement for implementing the hypergolic reacting flow. The intense luminosity of hypergolic flame was successfully suppressed using blue light spectrum illumination and bandpass optical filtering. The hypergolic burning spray structures can be classified into reactive stream separation, normal combustion, and oxidizer partial consumption based on the dynamic interaction of impinging jets. The majority of dispersed spray propellant was consumed in developing a hypergolic diffusion flame in the vicinity of a fuel-to-oxidizer dynamic pressure ratio (DR) of 0.83, a design condition of optimum mixing. Either off-design combustion of excessive oxidizer (DR ≪ 0.83) or fuel dynamic pressure (DR ≫ 0.83) caused deformation of the burning spray structure. The results indicated that the burning spray structure is significantly affected by the dynamic pressure ratio of impinging jets. The burning rate of the propellant mixture is expected to vary significantly with respect to the hypergolic burning structure. A simple optical visualization of the reacting flow via the blue light spectrum enhanced the qualitative understanding of hypergolic combustion.