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Author: Richard E. Longhouse
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 96
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Book Description
Improvement in the thrust/power ratio for shrouded propellers and fan-in-wing units, which are widely used for V/STOL aircraft propulsion, can be achieved by using an external aerodynamic diffuser during hover. Large diffuser divergence angles are required which necessitate a technique of controlling the flow separation from the internal diffuser wall. The purpose of this experimental investigation was to obtain a correlation between experimental and analytical prediction of performance improvement in order to generate a design technique for optimization of external diffusion, and investigate the potential of several techniques which offer a method of forcing the flow to diffuse externally. A static test facility for measuring the external flow field and the thrust of the model was constructed. All tests were performed with uniform, axial flow at the diffuser inlet. Two-dimensional tests were conducted employing either turning vanes, coanda effect, or rotating cylinder walls. Axisymmetric tests were performed using boundary layer control by suction or blowing. (Modified author abstract).
Author: Richard E. Longhouse
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 96
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Book Description
Improvement in the thrust/power ratio for shrouded propellers and fan-in-wing units, which are widely used for V/STOL aircraft propulsion, can be achieved by using an external aerodynamic diffuser during hover. Large diffuser divergence angles are required which necessitate a technique of controlling the flow separation from the internal diffuser wall. The purpose of this experimental investigation was to obtain a correlation between experimental and analytical prediction of performance improvement in order to generate a design technique for optimization of external diffusion, and investigate the potential of several techniques which offer a method of forcing the flow to diffuse externally. A static test facility for measuring the external flow field and the thrust of the model was constructed. All tests were performed with uniform, axial flow at the diffuser inlet. Two-dimensional tests were conducted employing either turning vanes, coanda effect, or rotating cylinder walls. Axisymmetric tests were performed using boundary layer control by suction or blowing. (Modified author abstract).
Author: Ying-chieh Albert Lee
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 126
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Book Description
Author: L. A. Povinelli
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 10
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Book Description
Author: Daniel Friedman
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 804
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Book Description
An experimental investigation was conducted in order to determine the performance of a 90 degree cascade diffusing bend with an area ratio of 1.45:1 and a 19-inch square inlet with several inlet-boundary-layer shapes and thicknesses. The maximum mean inlet Mach number was 0.41 and the corresponding airfoil Reynolds number was 950,000. The experimental results seem to indicate that, when the duct configuration requires a bend, a certain amount of diffusion can be obtained without an appreciable rise in the total-pressure losses. If length is important, this configuration requires much less space than the usual diffuser-bend combination.
Author: Robert Joseph Shaw
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 378
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Book Description
Author: James J. White (III)
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 0
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Book Description
A fixed-geometry diffuser system was tested in an arc-heated, hypersonic, open-jet wind tunnel facility at Mach numbers between 14 and 18 and Reynolds numbers (based on nozzle exit diameter) between 8,900 and 25,000. Tests were conducted both with an empty test section and with conical models in the flow. Test variables included test section open-jet length, diffuser second-throat length, and diffuser inlet geometry. Diffuser efficiency improved with increased diffuser second-throat length, with increasing Reynolds number, and with the addition of conical models into the flow. Changes in open-jet length and diffuser inlet geometry had no appreciable effect on diffuser efficiency with an empty test section. A streamlined model support strut produced marked improvement in diffuser efficiency over a blunt support strut.
Author: United States. National Aeronautics and Space Administration. Scientific and Technical Information Office
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 103
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Book Description
Two annular diffusers downstream of a nacelle-mounted fan were tested for aerodynamic performance, measured in terms of two static pressure recovery parameters (one near the diffuser exit plane and one about three diameters downstream in the settling duct) in the presence of several inflow conditions. The two diffusers each had an inlet diameter of 1.84 m, an area ratio of 2.3, and an equivalent cone angle of 11.5 deg, but were distinguished by centerbodies of different lengths. The dependence of diffuser performance on various combinations of swirling, radially distorted, and/or azimuthally distorted inflow was examined. Swirling flow and distortions in the axial velocity profile in the annulus upstream of the diffuser inlet were caused by the intrinsic flow patterns downstream of a fan in a duct and by artificial intensification of the distortions. Azimuthal distortions or defects were generated by the addition of four artificial devices (screens and fences). Pressure recover data indicated beneficial effects of both radial distortion (for a limited range of distortion levels) and inflow swirl. Small amounts of azimuthal distortion created by the artificial devices produced by only small effects on diffuser performance. A large artificial distortion device was required to produce enough azimuthal flow distortion to significantly degrade the static pressure recovery. (Author).
Author: Robert Joseph Shaw
Publisher:
ISBN:
Category : Diffusers
Languages : en
Pages : 330
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Book Description
Author: John S. Dennard
Publisher:
ISBN:
Category :
Languages : en
Pages : 65
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Book Description
