Abstract
and increase of launcher reliability and operational efficiency. A common way of slightly improving performance of gas-generatoropen-cycleenginesistheinjectionoftheturbineexhaustgasintothenozzledivergentsection, whichis also used for wall film cooling. The present study focuses on a numerical parametric analysis of the film-cooling efficiency in dual-bell nozzles. The secondary gas injection is made in the first bell, and it is found that the expansion fan originating from the inflection helps the film to better protect the wall. The results of fully-attached-flow simulations are also used to study the influence of film cooling on the expected behavior of nozzle side loads during operation with separated flow in the second bell. Nomenclature A = cross-sectional area a = speed of sound cp = constant-pressure specific heat g = gravity constant l = length M = Mach number _ m = mass flow rate p = pressure R = gas constant Re = Reynolds number r = radius s = slot height T = temperature u = flow velocity V = flight velocity x = abscissa � = change of wall angle at inflection
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