Performance Characteristics of Controllable Flat-Plate Flameholders

This paper is to study experimentally the characteristics of controllable flat-plate flameholders used in an afterburner. The idea of using the variable-angle flat-plates as the flameholder stems from the advantages of good controllability and light weight. Tests under 20% blockage ratio with various angles of attack (AOA), i.e., 30°, 45°, 60° and 90° of the flat-plates were carried out. Results under isothermal conditions showed that vortex shedding was not observed at AOA of 30°, while it did occur when the AOA was more than 30°. An asymmetric flow field at down stream of the flat-plate was also observed under isothermal conditions. Moreover, it was found that the Strouhal numbers are separated into two groups. The higher value, i.e, St=0‥25, corresponds to the 30° flow condition and the lower value, i.e., St=0.22, corresponds to other flow conditions. Results also show that the flat plate with 30° AOA has better pressure recovery. Under reacting flow conditions, the fuel distributions of different angles of attack are essentially symmetric. Schlieren photograph technique shows no vortex shedding even for flat-plates of high AOA under reacting conditions. The measured oxygen concentration in the downstream shows a symmetric profile even though the local flame structure is skewed behind the flat-plate. The combustion efficiencies of the flat-plate flameholders with controllable inclined angles are higher than that of the conventional V-gutter.