Thrust Augmentation with Mixer/Ejector Systems

byDr. Walter M. Presz, Jr.Western New England CollegeSpringfield, MAGary ReynoldsStage III TechnologiesLaJolla, CADr. Craig HunterNASA Langley Research CenterHampton, VAAbstractOlder conmlercial aircraft often exceed FAA sideline noiseregulations. The major problem is the jet noise associated withthe high exhaust velocities of the low bypass ratio engines onsuch aircraft. Mixer/ejector exhaust systems can provide asimple means of reducing the jet noise on these aircraft bymixing cool ambient air with the high velocity engine gasesbefore they are exhausted to ambient. This paper presents newinformation on thrust performance predictions, and thrustaugmentation capabilities of mixer/ejectors. Results arepresented from the recent development program of thepatented Alternating Lobe Mixer Ejector Concept (ALMEC)suppressor system for the Gulfstream GII, GlIB and Gillaircraft. Mixer/ejector perfbrmance procedures are presentedwhich include classical control volume analyses, compoundcompressible flow theory, lobed nozzle loss correlations andstate of the art computational fluid dynamic predictions. Themixer/ejector thrust predictions are compared to subscale windtunnel test model data and actual aircraft flight testmeasurements. The results demonstrate that a properlydesigned mixer/ejector noise suppressor can increase effectiveengine bypass ratio and generate large thrust gains at takeoffconditions with little or no thrust loss at cruise conditions. Thecruise performance obtained for such noise suppressor systemsis shown to be a strong function of installation effects on theaircraft.M = Mach NumberT = TemperatureTh = ThrustV = Velocityd_= Thrust Augmentation, --p = DensitySubscripta, A = Airplaneamb = Ambient Conditionse = System Exit Stationp = Primary Streams = Secondary Streamt = Stagnation Conditions1 - Primary Nozzle Exit2 = Ejector Shroud ExitIntroductionNomenclature