Design and Experimental Evaluation of Propfan Inlets

A cooperative research program has provided the first high-speed wind-tunnel data on propfan inlets. In the initial phase of the program, two single-scoop or chin inlet configurations--one without a boundary layer diverter and the other with a diverter--were designed and tested with a 2-foot-diameter SR-3 propfan. The models were extensively instrumented and wind-tunnel tested at Mach numbers up to 0.80.

Results from the tests showed, as expected, considerably better inlet pressure recoveries for the configuration with the boundary layer diverter. The overall recovery level for both inlets was significantly higher, however, than previous analyses had indicated. Although instrumentation difficulties compromised the measurements, inlet-induced blade cyclic stresses appeared higher than anticipated. Both inlet models showed good agreement with predicted cowl surface pressure distributions, thus validating the design methods.