Convertible Fan/Shaft Engine Variable Fan Geometry Investigation
Abstract
Preliminary design studies have shown that advanced VTOL aircraft performance can be enhanced when the aircraft are coupled with a turbofan engine having the ability to provide shaft power to the vertical lift rotor (convertible fan/shaft engine). A program was conducted to determine the feasibility of using variable fan inlet and duct exit guide vanes to effectively reduce fan horsepower and eliminate thrust during periods of vertical lift and hover. An exploratory test program was conducted in an existing 0.5 hub-tip ratio compressor research rig modified to simulate a high-bypass-ratio fan configuration. This fan configuration consisted of variable inlet and exit guide vanes, a fan rotor, and a simulated gas generator flowpath providing a 4.2:1 bypass ratio. The fan rotor was an existing moderate-speed rotor blade with a tip diameter of 43 inches, tip speed of 1150 fps, and design pressure ratio and flow of 1.35 and 285 lb/sec, respectively. Results from the test program established the feasibility of using variable-geometry inlet and duct exit guide vanes to effectively reduce fan horsepower and thrust. Fan horsepower was reduced to 16 percent of the maximum (cruise) power absorbed by the fan, and fan thrust was reduced by 100 percent. The test results indicate that the potential exists for reducing fan horsepower to values of less than 10 percent of the cruise power. Inlet guide vane, rotor blade, and duct exit guide vane stresses were within safe operating limits over the test range of guide vane positions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1970
- Accession Number
- AD0873018
Entities
People
- Burton A. Jones
- David L. Wright
Organizations
- Pratt & Whitney