Performance Measurements of Direct Air Injection in a Cavity-Based Flameholder for a Supersonic Combustor (Postprint)

摘要

For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Direct air injection has been shown to be a valuable tool for improving combustion in a directly fueled cavity-based flameholder. The objective of this research was to quantitatively determine the advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream flow downstream of the cavity flameholder. Pitot and static pressure, total temperature, and gas sampling measurements were taken and the corresponding values were processed to yield relevant engineering quantities. Data were taken over a range of fuel and air injection rates. Direct air injection resulted in increased combustion throughout the area of interest behind the cavity. Air injection increased the static temperature and pressure throughout the area of interest. Enthalpy spread into the free stream and total pressure losses also increased through the use of air injection. Direct air injection shows more promise for higher fuel loadings.