An atmospheric test program was conducted to define a low NOx annular combustor concept suitable for a supersonic, high-altitude aircraft application. The lean premixed combustor, known as the Vortex Air Blast (VAB) concept, was tested as a 22.0 cm diameter model in the early development phases to arrive at basic design and performance criteria. Final demonstration testing was carried out on a full scale combustor of 0.66 m diameter. Variable geometry dilution ports were incorporated to allow operation of the combustor across the range of conditions between idle (Tin = 422 K, Tout = 917 K) and cruise (Tin = 833 K, Tout = 1778 K). Test results showed that the design could meet the program NOx goal of 1.0 g NO2/kg fuel at a reduced atmospheric cruise condition.

Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.