Acoustic properties of a supersonic fan
Short rotor blade span supersonic fan for pressure wave forward propagation elimination, obtaining acoustic and aerodynamic characteristics
Coats, J. W.↗
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Some experimental results on lift fan noise reduction
Tip turbine driven lift fan noise reduction tests, considering design parameters effects
Benzakein, M. J.↗
Factors affecting handling qualities of a lift- fan aircraft during steep terminal area approaches
Handling qualities of V/STOL research vehicles during steep terminal area approaches, discussing powered lift fan VTOL aircraft limitations and instrument landing approach
Gerdes, R. M.↗
Low-speed jet noise from a 1.83-meter /6-ft/ fan for turbofan engines
Fan induced low speed jet noise from turbofan engines, discussing results of far field sound measurements for simulated nacelle configurations with and without acoustic liners
Feiler, C. E.↗
Wind tunnel tests of a wing-installed model VTOL lift fan with coaxial drive turbine
Wing installed VTOL coaxial drive lift fan model in wind tunnel test, investigating performance in crosswind environment
Diedrich, J. H.↗
Reduction of fan noise: A concept
Acoustic materials strategically located within or near noise sources are effective for noise abatement on wing mounted lift fans, nozzles, engines and other noise sources. Panels are straightforward and easily adaptable to situations outside of aircraft technology.
Simonson, M. R.↗
LF336 lift fan modification and acoustic test program
Investigating lift fan noise reduction by configuration modifications in LF336/A
Kazin, S. B.↗
Two-Stage Fan I: Aerodynamic and Mechanical Design
A two-stage, highly-loaded fan was designed to deliver an overall pressure ratio of 2.8 with an adiabatic efficiency of 83.9 percent. At the first rotor inlet, design flow per unit annulus area is 42 lbm/sec/sq ft (205 kg/sec/sq m), hub/tip ratio is 0.4 with a tip diameter of 31 inches (0.787 m), and design tip speed is 1450 ft/sec (441.96 m/sec). Other features include use of multiple-circular-arc airfoils, resettable stators, and split casings over the rotor tip sections for casing treatment tests.
Messenger, H. E.↗
High-loading, 1800 ft/sec tip speed transonic compressor fan stage. 1: Aerodynamic and mechanical design
A single stage fan with a tip speed of 1800 ft/sec (548.6m/sec) and hub/tip ratio of 0.5 was designed to produce a pressure ratio of 2.285:1 with an adiabatic efficiency of 84.0%. The design flow per inlet annulus area is 38.7 lbm/sq ft-sec (188.9KG/sqm-sec). Rotor blades have modified multiple-circular-arc and precompression airfoil sections. The stator vanes have multiple-circular-arc airfoil sections.
Morris, A. L.↗
STOL noise sources and fan noise treatment
STOL noise goals, noise sources, and their affects on engine and propulsion systems design are considered. It is shown that major noise sources constitute the blown-flap system with its turbofan engine and the augmentor wing propulsion system. Most of the problem areas associated with STOL propulsion systems are defined and the development of a multistage fan engine with proper rotor-stator spacings and low noise core exhaust jet is illustrated. A variable-area acoustic inlet provides near sonic flow conditions during takeoff and landing.
Rulis, R. J.↗
High loading, 1800 ft/sec tip speed, transonic compressor fan stage. 2: Final report
Tests were conducted on a 0.5 hub/tip ratio, single-stage fan-compressor designed to produce a pressure ratio of 2.285 an efficiency of 84 percent with a rotor tip speed of 1800 feet per second. A peak efficiency of 82 percent was achieved by the stage at a stall margin of 6.5 percent. Tests showed that stall-limit line was slightly sensitive to tip-radial distortion, but stall-line improvements were noted when the stage was subjected to circumferential and hub-radial flow distortions. Rotor blade passage and trailing edge shock positions were inferred from static pressure contours over the rotor tips.
Morris, A. L.↗
Analysis of integral lift-fan engine dynamics
An integral lift-fan engine being considered for VTOL applications was simulated using the hybrid computer. A contractor-proposed fuel control and a simple model of the roll dynamics of a hovering VTOL airplane were used in the simulation. Both steady-state and transient data were generated. The desired engine time constant of 0.20 second was achieved for thrust increments less than 10 precent of the design thrust. For roll angle demands less than 10 deg, roll angle overshoot was acceptable with more than 84 percent of the demand achieved in 1 second.
Szuch, J. R.↗
Labyrinth seal testing for lift fan engines
An abradable buffered labyrinth seal for the control of turbine gas path leakage in a tip-turbine driven lift fan was designed, tested, and analyzed. The seal configuration was not designed to operate in any specific location but was sized to be evaluated in an existing test rig. The final sealing diameter selected was 28 inches. Results of testing indicate that the flow equations predicted seal air flows consistent with measured values. Excellent sealing characteristics of the abradable coating on the stator land were demonstrated when a substantial seal penetration of .030 inch into the land surface was encountered without appreciable wear on the labyrinth knife edges.
Dobek, L. J.↗
Preliminary design study of quiet integral fan lift engines for VTOL transport applications in the 1980s
Preliminary designs of three integral lift fan engines suitable for commercial certification in the 80's were completed. Emphasis was placed on low cost, simplicity, low noise, low emissions, minimum weight, and design features meeting all commercial standards for fire safety and containment.
Rabone, G. R.↗
Performance of a 1.20 pressure ratio STOL fan stage at three rotor blade setting angles
A model of a short takeoff and landing (STOL) fan stage was testedin a single-stage compressor research facility. Surveys of the airflow conditions ahead of the rotor, between the rotor and stator, and behind the stator were made over the stable operating range of the stage. At the design speed of 213.3 meters per second and a weight flow of 31.2 kilograms per second, the stage pressure ratio of 1.15 was less than the design value of 1.2. The stage was tested with the rotor blades reset for more flow. Design pressure ratio was achieved and surpassed with the minus 5 deg and minus 7 deg resets, respectively. The stage efficiency was 0.88 for the minus 5 deg reset and 0.85 for the minus 7 deg reset.
Lewis, G. W., Jr.↗
Fan noise mechanisms and control. II.
The fluctuating velocity input into the fan is measured by two approaches. One approach makes use of stationary hot wires mounted in front of the rotor. The other approach employs rotating hot wires moving with the rotor. It is shown that the noise has three principal source components including discrete frequencies, which are governed by inflow distortion, low frequency broad band noise governed by inflow turbulence, and high frequency broad band noise governed by the blade tips.
Lowson, M. V.↗
The effect of wind tunnel wall interference on the performance of a fan-in-wing VTOL model
A fan-in-wing model with a 1.07-meter span was tested in seven different test sections with cross-sectional areas ranging from 2.2 sq meters to 265 sq meters. The data from the different test sections are compared both with and without correction for wall interference. The results demonstrate that extreme care must be used in interpreting uncorrected VTOL data since the wall interference may be so large as to invalidate even trends in the data. The wall interference is particularly large at the tail, a result which is in agreement with recently published comparisons of flight and large scale wind tunnel data for a propeller-driven deflected-slipstream configuration. The data verify the wall-interference theory even under conditions of extreme interference. A method yields reasonable estimates for the onset of Rae's minimum-speed limit. The rules for choosing model sizes to produce negligible wall effects are considerably in error and permit the use of excessively large models.
Heyson, H. H.↗
Highly loaded multi-stage fan drive turbine - performance of initial seven configurations
Experimental results of a three-stage highly loaded fan drive turbine test program are presented. A plain blade turbine, a tandem blade turbine, and a tangentially leaned stator turbine were designed for the same velocity diagram and flowpath. Seven combinations of bladerows were tested to evaluate stage performances and effects of the tandem blading and leaned stator. The plain blade turbine design point total-to-total efficiency was 0.886. The turbine with the stage three leaned stator had the same efficiency with an improved exit swirl profile and increased hub reaction. Two-stage group tests showed that the two-stage turbine with tandem stage two stator had an efficiency of 0.880 compared to 0.868 for the plain blade two-stage turbine.
Wolfmeyer, G. W.↗