This paper presents a summary of principal results obtained from crossflow tests of a model 15-in.-diam lift fan installed in a wing in the NASA Lewis Research Center, 9 by 15 ft V/STOL Propulsion Wind Tunnel. Tests were run with and without exit louvers over a range of tunnel air speeds, fan speeds, and wing angle of attack. Fan thrust in crossflow was influenced by two principal factors: the effects of inflow distortion on blade-row performance, and changes in fan stage operating point brought about by changes in back pressure ratio. In this particular fan, flow separation on the inlet bellmouth did not appear to be a serious problem for crossflow operation.

Performance Characteristics of a Model VTOL Lift Fan in Crossflow

Cross flow wind tunnel performance tests of 15 in. wing installed lift fan with coaxial drive turbine for VTOL transport aircraft

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Wind tunnel tests of a wing-installed model VTOL lift fan with coaxial drive turbine

Comment on 'Advanced technology thrust vectoring exhaust systems'

QL = CS(h ± X6 (2) The plenum pneumatic capacitances are based on isentropic compressibility. The pressure rates associated with the inner circular skirt plenums and the inskirt plenum, which lies between the inner circular skirts and the outer peripheral skirt, vary with vehicle motion in pitch and heave where dP/dt = (kP/V)[2Q + A(dZ/dt ± xd8/dt)] (3) The equations of vehicle motion in pitch and heave represent a rigid craft operating over a nondeforming surface with zero forward speed and are simplified by limiting the motion to small perturbations. A body-fixed coordinate system is used with the origin fixed at the vehicle center of gravity. A further simplification is realized due to symmetry about the x-z and y-z planes of the vehicle. The equation of motion in heave for the multiple-skirt ACV is 2 = 9 ~

Gross thrust coefficient - Turbofan engines

Slide-valve-controlled vectoring nozzle

flowfield and that temperatures could be hazardous to the airplane. The test program was therefore extended to investigate changes in JBD design which might improve the environment. The three configurations described previously, selected as requiring minimum modifications to existing deflectors, were tested. The results of these tests are shown in Fig. 18, with results from the standard deflector included for comparison. From Fig. 18 it can be seen that these tests successfully demonstrated a JBD design that will prevent any hot gas from reaching the airplane. It can also be seen that modifications which were beneficial in some locations were detrimental in other locations, and that the momentum balance is not adequate to determine the effects of modifications. The fence was expected to turn the forward flow outboard, and (to an extent) it was successful. However, the temperature at the top of the vertical tail shows that the fence also augmented the upward flow. Similarly, reducing the JBD angle to 45° was expected to lower all temperatures on the airplane, but it increased the temperature at the engine inlet. These test results were valuable in the F-111B program and are generally applicable for situations that duplicate the F-111B nozzle spacing, height above the deck, and nozzle inclination. In any other case, the uncertainties in analysis as demonstrated in this test are such that data from exact models should be obtained.

J. A. C. Kentfield

Papers

Nozzles for jet-lift V/STOL aircraft.