Characterization of Liquid Fuel Mixing in a Scramjet Flowfield

This paper describes an experimental program to provide high quality, fuel-air mixing data in a well-characterized scramjet model flowfield for validation of computational tools, such as subgrid LES models. The study employs a noncombusting, supersonic windtunnel and a standard, backward-facing step configuration that allows injection of gaseous or liquid fuel (or fuel surrogates). The facility is modular, with nozzles for providing flows from M=1.5 to 3.5. The facility is instrumented so as to provide a rigorous set of inlet, boundary, and internal flow properties. Results are presented for a Mach 2.5 flow without injection, and with 90 ° injection of a nonevaporating liquid fuel surrogate (acetone) just upstream of the step. The results include vertical profiles of inlet Mach number and static pressure; test section, wall static pressures; downstream profiles of flow static pressures; characterization of the droplet distributions produced by the fuel atomizer; and initial characterization of the fuel mixing as measured by laser-induced fluorescence images. The results are used to characterize the main flow features, such as the expansion over the step, boundary and shear layers and the reattachment shock. The results are repeatable, demonstrating the reliability of the facility. In addition, the liquid injection has little effect on most of the flow features, with results for this case nearly identical to the noninjection case