Pylon Effects on a Scramjet Cavity Flameholder Flowfield; Doctoral thesis

摘要

Cavity flameholders in supersonic combustion ramjet (scramjet) combustors, while effective, fail to take advantage of the full combustor volume. Adding a pylon to the leading edge of a cavity flameholder generates a flowfield increasing mass exchange between the cavity and main combustor flow, increasing the mixing interface between flameholder products and main combustor flow, and exhibiting minimal Reynolds number effects. To demonstrate this modified flowfield driven by supersonic expansion behind the pylon, pylon- cavity flameholder flowfield data were obtained through a combination of wind tunnel experimentation and steady-state computational fluid dynamics. Flowfield effects of the pylon-cavity were examined at a Mach number of two and Reynolds numbers from approximately 33 million m-1 to 55 million m-1. Addition of the pylon resulted in approximately three times the mass exchange between the cavity and overlying flow. Reynolds number effects were weak. A strong upward flow behind the pylon, from the cavity to the top of the pylon wake, significantly increased exposure and exchange of cavity fluid with the main combustor flow. Assuming a suitably reacting fuel-air mixture, the addition of a pylon offers the scramjet designer an attractive option to take advantage of a greater proportion of combustor volume and improve combustor performance.