Acetone PLIF visualization of the fuel distribution at plasma-enhanced supersonic combustion

• 100 Hz Acetone PLIF is applied to characterize unburned fuel distributions in a plasma stabilized planewall supersonic combustor. • A plasma filament coupled to a transverse fuel jet in a supersonic flow is shown to enhance jet penetration, cross flow expansion, and initiate fuel jet breakup. • A significant unburned fuel distribution in a plasma generated separation region is identified. • The minimum plasma pulse duration for flowfield transition from initial conditions to a combustion pattern was determined. This study examines the mixing and flameholding characteristics of a plasma stabilized planewall supersonic combustor. Fuel injection, ignition, and flameholding are provided by Plasma Injection Modules (PIMs) installed in a M = 2, 76.2 × 76.2 mm duct. Two configurations were explored: the first involves a plasma filament collocated within a single transverse fuel jet, while the second involves combustion stabilization using a series of three PIMs. Unburned fuel distributions were assessed with acetone planar laser induced fluorescence (PLIF), where acetone vapor was seeded into the gaseous fuel. PLIF measurements were performed for both streamwise and spanwise laser sheet orientations. Supporting datasets were collected including schlieren imaging, chemiluminescent imaging, and pressure distributions. PIM actuation is found to increase jet penetration, crossflow expansion, and initiate fuel jet breakup. The average jet cross sectional area is shown to increase by >20% with the addition of plasma. PLIF imaging at PIM stabilized combustion revealed a significant unburned fuel concentration in a local separation region near the PIMs, and identified the minimum plasma pulse duration for flowfield transition from initial conditions to the combustion pattern.