ENGINEERING DESIGN MODELS FOR RAMJET EFFICIENCY AND LEAN BLOWOFF

Combustion efficiency and lean blowoff semiempirical preliminary desig n models, validated originally for laboratory axisymmetric flameholder s and conventional gas turbine combustors, are extended to dump combus tor ramjet geometries. The general efficiency model includes effects o f fluid mechanics, spray evaporation, and finite chemical kinetics, an d its application to ramjets requires inclusion of choked flow due to the downstream nozzle. For the work reported on here, test data employ ing liquid fuel injection far upstream of the flameholder are utilized , so that the configuration is modeled as prevaporized and premixed. T he model successfully correlates these data, which include variations in combustor geometry, nozzle area ratio, and overall equivalence rati o. The resulting correlation allows the prediction of combustion effic iency for the special case examined to date. Work with the lean blowof f model is limited to comparison of the original model with results pr esented in the literature.