MIXING ENHANCEMENT IN CHEMICAL-LASERS .1. EXPERIMENTS

Nonreacting and reacting flow visualization experiments were used to demonstrate the ability of a new supersonic nozzle design (called the ramp nozzle) to accelerate mixing in a deuterium floride chemical laser via the reactant surface stretching mechanism. Unlike trip nozzles, which use inert gas injection to cause reactant surface stretching, the ramp nozzle causes a similar effect through its geometry without gas injection. The results from laser-induced fluorescence experiments indicate the ramp nozzle design produces a factor of two increase in the reactant interface length within about a centimeter of the nozzle exit. A side-by-side comparison in reacting flow of the ramp and gas trip nozzles suggest that both designs produce similar levels of mixing enhancement. These data are used to develop a phenomenological model for mixing enhancement in gas trip and ramp nozzles. This model describes a possible mechanism by which trip jets cause reactant surface stretching, indicates how the surface stretching rates can be calculated from the reactant nozzle geometry and flow conditions, and permits performance scaling laws consistent with the trip nozzle data to be derived.