Supersonic Combustion Experiments with a Cavity-Based Fuel Injector

TLDR

Recent experiments in a direct‑connect supersonic combustor have been reported. The study used two interchangeable nozzles (Mach 1.8 and 2.2) to generate inlet flow conditions equivalent to Mach 4–6 at 47.9 kPa. The injector/combustor concept achieved successful ignition and sustained combustion of gaseous ethylene at equivalence ratios 0.25–0.75 using only a spark plug, producing delta‑force 667–1779 N, pressure ratios 3.1–4.0, an 80 % combustion efficiency, and a skin‑friction coefficient of 0.0028.

Abstract

Recent results from combustion experimentsin a direct-connectsupersoniccombustorarepresented. Successful ignition and sustained combustion of gaseous ethylene have been achieved using an injector/e ameholder concept with low-angle, e ush-wall fuel injection upstream of a wall cavity. Two interchangeable facility nozzles (Mach 1.8 and 2.2) were used to obtain combustor inlet e ow properties that simulate e ight conditions between Mach 4 and 6 at a dynamic pressure of 47.9 kPa. Mainstream combustion was achieved at equivalence ratios between 0.25 and 0.75 using only a spark plug and no other external ignition aids. Delta-force levels between 667 and 1779 N were measured, with corresponding combustor pressure ratios between 3.1 and 4.0. Video records of the e ame zone show an intensely active combustion zone with rapid e ame spreading. One-dimensional performance analysis of the test data indicates a combustion efe ciency around 80% with an average combustor skin friction coefe cient of 0.0028.