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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Status of current development activity related to STOL propulsion noise reduction

The noise goal of 95 PNdb for STOL aircraft imposes severe technology demands on propulsion systems. Effects of this goal on the design of the propulsion system are reviewed. Results from recent development programs associated with STOL noise reduction, such as high bypass fan tests, 25 PNdb acoustic suppression tests, sonic inlets, and powered lift system noise tests, are presented. Integrated propulsion system designs for the blown flap and augmentor wing powered lift systems capable of meeting the noise goal are shown and the performance, installation, and economic penalties assessed.

Rulis, R. J.↗
NASA NTRS1973

Status of current development activity related to STOL propulsion noise reduction.

The noise goal of 95 PNdB for STOL aircraft imposes severe technology demands on propulsion systems. Effects of this goal on the design of the propulsion system are reviewed. Results from recent development programs associated with STOL noise reduction, such as high bypass fan tests, 25 PNdB acoustic suppression tests, sonic inlets, and powered lift system noise tests, are presented. Integrated propulsion system designs for the blown flap and augmentor wing powered lift systems capable of meeting the noise goal are shown, and the performance, installation, and economic penalties are assessed.

Rulis, R. J.↗
NASA NTRS2008

Models of Lift and Drag Coefficients of Stalled and Unstalled Airfoils in Wind Turbines and Wind Tunnels

Equations are developed with which to calculate lift and drag coefficients along the spans of torsionally-stiff rotating airfoils of the type used in wind turbine rotors and wind tunnel fans, at angles of attack in both the unstalled and stalled aerodynamic regimes. Explicit adjustments are made for the effects of aspect ratio (length to chord width) and airfoil thickness ratio. Calculated lift and drag parameters are compared to measured parameters for 55 airfoil data sets including 585 test points. Mean deviation was found to be -0.4 percent and standard deviation was 4.8 percent. When the proposed equations were applied to the calculation of power from a stall-controlled wind turbine tested in a NASA wind tunnel, mean deviation from 54 data points was -1.3 percent and standard deviation was 4.0 percent. Pressure-rise calculations for a large wind tunnel fan deviated by 2.7 percent (mean) and 4.4 percent (standard). The assumption that a single set of lift and drag coefficient equations can represent the stalled aerodynamic behavior of a wide variety of airfoils was found to be satisfactory.

Spera, David A.↗
NASA NTRS2001

On the Use of Surface Porosity to Reduce Unsteady Lift

An innovative application of existing technology is proposed for attenuating the effects of transient phenomena, such as rotor-stator and rotor-strut interactions, linked to noise and fatigue failure in turbomachinery environments. A computational study was designed to assess the potential of passive porosity technology as a mechanism for alleviating interaction effects by reducing the unsteady lift developed on a stator airfoil subject to wake impingement. The study involved a typical high bypass fan Stator airfoil (solid baseline and several porous configurations), immersed in a free field and exposed to the effects of a transversely moving wake. It was found that, for the airfoil under consideration, the magnitude of the unsteady lift could be reduced more than 18% without incurring significant performance losses.

Tinetti, Ana F.↗
NASA NTRS1986

A parametric approach to hover balance analysis of two STOVL fighter concepts

Successful development of an aircraft with vertical landing capability must address the critical problem of balancing the aircraft for hover. In this paper a parametric method for balancing short takeoff and vertical landing (STOVL) aircraft in hover is described and applied to the analysis of two conceptual STOVL fighters. One uses a remote augmented lift system and the other a thrust-vectoring hybrid tandem-fan engine.

Samuels, Jeffrey J.↗
NASA NTRS1978

Three-dimensional effects on pure tone fan noise due to inflow distortion

A theoretical analysis of pure tone fan noise generated by inflow distortion-rotor interaction is carried out with the aid of the three-dimensional unsteady lifting surface theory developed by Namba (1977, 1974). Particular attention is given to a study of the accuracy of available two-dimensional theory for the prediction of pure tone fan noise due to the interaction of inflow distortion with a subsonic annular blade row. The theoretical model considered consists of a single three-dimensional annular cascade rotating at constant angular velocity in an annular rigid-wall duct of infinite axial extent. Attention is given to the fluctuating pressure induced by a rotor blade row, the fluctuating velocity induced by it, an inflow distortion with only an axial velocity component, the determination of acoustic dipole distribution, the pure tone acoustic power, and two-dimensional theory and quasi-three-dimensional theory.

Kobayashi, H.↗
NASA NTRSDate not supplied

Scoping of an Air Supply Configuration for AFC on a Commercial Transport Airplane High Lift System

A scoping study is being conducted on the air supply fora microjet-based active flow control (AFC) system on a twin-turbofan commercial transport airplane. Microjets provide circulation control using small surface-normal pneumatic jets located near the trailing edge of a lifting surface such as a wing or flap. When located on the pressure side of the lifting surface they increase the lift, and when located on the suction side they decrease lift. In this study, microjets are considered for installation in the flaps of the high-lift version of the Common ResearchModel (CRM-HL). Two different architectures to supply the air for the microjets are considered: (1) bleed air from the airplane’s auxiliary power unit (APU) plus ram air, and (2) engine fan bleed air plus ram air. A model based on the 1D compressible flow equations is applied to analyze the air supply system architectures and predict the microjet flow rate with the resulting airplane performance changes based on Reynolds-averaged Navier-Stokes modeling of microjets on the CRM-HL. The results of this scoping study are encouraging in that pressurized air from the APU or the engine fan can be used to entrain ram air and thereby increase the AFC mass flow rate to achieve effective lift control and airplane performance enhancement during takeoff and landing.

AATT↗
NASA NTRS1980

QCSEE UTW engine powered-lift acoustic performance

Powered-lift acoustic test of the Quiet Clean Short Haul Experimental Engine (QCSEE) under the wing (UTW) engine are reported. Propulsion systems for two powered-lift concepts were designed, fabricated, and tested. In addition to low noise features, the designs included composite structures, gear-driven fans, digital control, and a variable pitch fan (UTW). The UTW engine was tested in a static ground test facility with wing and flap segments to simulate installation on a short haul transport aircraft of the future. Powered-lift acoustic performance of the UTW engine is compared with that of the previously tested and reported QCSEE over-the-wing (OTW) engine. Both engines were slightly above the noise goal but were significantly below current FAA and modern wide-body jet transport levels. The UTW system in the powered-lift mode was penalized by reflected engine noise from the wing and flap system, while the OTW system was benefitted by a wing noise shielding effect.

Loeffler, I. J.↗
NASA NTRS1974

Quiet engine from NASA

Engine designs resulting from the NASA sponsored quiet engine program are described in terms of their possible use on the DC-8. These engines have high bypass ratios for low jet noise and low-speed, low-noise fans. Experiments were carried out on various fan designs with different tip speeds. The advantage of low tip speeds and high lift coefficients has been demonstrated. The engines are equipped with flight-standard nacelles with acoustic suppression. It is estimated that these improvements will reduce DC-8 noise by about 26EPNdB-29EPNdB.

Sanders, N. D.↗
NASA NTRS1975

Motion-base simulator study of control of an externally blown flap STOL transport aircraft after failure of an outboard engine during landing approach

A moving-base simulator investigation of the problems of recovery and landing of a STOL aircraft after failure of an outboard engine during final approach was made. The approaches were made at 75 knots along a 6 deg glide slope. The engine was failed at low altitude and the option to go around was not allowed. The aircraft was simulated with each of three control systems, and it had four high-bypass-ratio fan-jet engines exhausting against large triple-slotted wing flaps to produce additional lift. A virtual-image out-the-window television display of a simulated STOL airport was operating during part of the investigation. Also, a simple heads-up flight director display superimposed on the airport landing scene was used by the pilots to make some of the recoveries following an engine failure. The results of the study indicated that the variation in visual cues and/or motion cues had little effect on the outcome of a recovery, but they did have some effect on the pilot's response and control patterns.

Middleton, D. B.↗
NASA NTRS1961

A Wind-Tunnel Investigation of a 4-Foot-Diameter Ducted Fan Mounted on the Tip of a Semispan Wing

Power, wing angle of attack, and the angle of the duct relative to the wing were varied to achieve a specified lift and thrust for a forward velocity range from 0 to 140 knots. In this manner a so-called transition program of steady-state conditions was defined over the velocity range. It was found-that large pitch-up moments resulted when the ducted fan was operated at an angle of attack to the air stream. A deflected vane installed in the high-energy air at the duct exit was helpful in reducing these pitch-up moments. Large downwash angles were induced by the ducted fan at a selected horizontal-tail location. The possibility of using guide vanes in the duct inlet to vary thrust for the purpose of roll control at low forward speeds was examined.The maximum incremental thrust available at zero forward velocity was found to be 11% of the total thrust required at that speed.

Yaggy, Paul F.↗
NASA NTRS1982

Status and capabilities of the National Full Scale Facility 40- by 80-foot wind tunnel modification

The background, requirements, and aerodynamic design of the modified NASA Ames 40 x 80 ft wind tunnel are reviewed, along with the systems integration and systems test results. Advancing vehicle sizes and airspeeds required a larger wind tunnel test section and a capability for 100 and 300 knots airspeed simulation. Acoustic mufflers at the inlet and exit of the nonreturn circuit provide noise suppression. The enlarged test section is intended to accomodate the complex flowfields of wings with high lift coefficients, and the drive system is designed with minimum residual swirl. Features of the fan blades are examined, along with characteristics of the test channels, control vanes and louvers, the exit, circuit losses, temperature rises during operation of the nonreturn circuit, and the facility acoustics. Specific construction problems and solutions for the conversion process are outlined, and it is noted that operational status is expected at the end of 1982.

Mort, K. W.↗
NASA NTRS1964

Dynamic Tests of V/STOL Transport Models

This paper presents a summary of results obtained in dynamic tests of free-flight models of various configurations suitable for V/STOL transport aircraft at the NASA Langley Research Center. The configurations covered will be the tilt-wing propeller-driven type as represented by the XC-142A tri-service transport, the fan-in-wing type as represented by the XV-5A research airplane, and the jet-lift type as represented by the Dornier 00-31 transport. The test techniques themselves are not described in this paper since they have been described in detail previously in references 1 and 2.

Dynamic stability↗
NASA NTRS1981

Three-dimensional periodic disturbances acting upon airfoils in cascade

A theory for three dimensional periodic gusts interacting with loaded airfoils was developed. The unsteady disturbances are linearized with respect to the mean potential flow of the airfoils. The vorticity transport equation is integrated analytically in a Lagrangian form. The vorticity vector shows strong variations in its magnitude and wavelength as it interacts with the flow field of a lifting airfoil. The streamwise component of vorticity increases significantly with flow acceleration and flow turning. The rectangular fan approximation is used and a single Helmholtz equation is derived that characterizes the unsteady three dimensional flow field.

Atassi, H.↗
NASA NTRS2006

Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons: Installed Nozzles - 2

Propulsion airframe aeroacoustic (PAA) interactions arise due to the manner in which an engine is installed on the airframe and lead to an asymmetry in the flow/acoustic environment, for example, for under-the-wing installations due to the pylon, the wing and the high-lift devices. In this work we study how we can affect these PAA interactions to reduce the overall jet-related installed noise by tailoring the chevron shapes on fan and core nozzles in a unique fashion to take advantage of this asymmetry. In part 1 of this trio of papers we introduced the concept of azimuthally varying chevrons (AVC) and showed how some types of AVCs can be more beneficial than the conventional chevrons when tested on "isolated" scaled nozzles inclusive of the pylon effect. In this paper, we continue to study the effect of installing these AVC nozzles under a typical scaled modern wing with high-lift devices placed in a free jet. The noise benefits of these installed nozzles, as well as their installation effects are systematically studied for several fan/core AVC combinations at typical take-off conditions with high bypass ratio. We show, for example, that the top-enhanced mixing T-fan AVC nozzle (with enhanced mixing near the pylon and less mixing away from it) when combined with conventional chevrons on the core nozzle is quieter than conventional chevrons on both nozzles, and hardly produces any high-frequency lift, just as in the isolated case; however, its installed nozzle benefit is less than its isolated nozzle benefit. This suppression of take-off noise benefit under installed conditions, compared to its isolated nozzle benefit, is seen for all other chevron nozzles. We show how these relative noise benefits are related to the relative installation effects of AVCs and baseline nozzles.

Mengle, Vinod G.↗
NASA NTRS1982

Rotorcraft convertible engines for the 1980s

Two rotorcraft studies were executed. The goal was to identify attractive techniques for implementing convertible powerplants for the ABC, Folded Tilt Rotor, and X-wing type high speed, high-L/D rotorcraft; to determine the DOC and fuel savings benefits achieved thereby; and to define research required to bring these powerplants into existence by the 1990's. These studies are reviewed herein and the different methods of approach are pointed out as well as the key findings. Fan shaft engines using variable inlet guide vanes or torque converters, and turboprop powerplants appear attractive. Savings in DOC and fuel consumption of over 15 percent are predicted in some cases as a result of convertible engine use rather than using separate engines for the thrust and the shaft functions. Areas of required research are fan performance (including noise), integrated engine/rotorcraft control, torque converters, turbine design, airflow for rotorcraft torque control, bleed for lift flow, and transmissions and clutches.

Eisenberg, J. D.↗
NASA NTRS1983

Design analysis of a self-acting spiral-groove ring seal for counter-rotating shafts

A self-acting spiral groove inter-shaft ring seal of nominal 16.33 cm (6.43 in.) diameter for sealing fan bleed air between counter rotating shafts in advanced turbofan engines was analyzed. The analysis focused on the lift force characteristics of the spiral grooves. A NASA Lewis developed computer program for predicting the performance of gas lubricated face seals was used to optimize the spiral groove geometry to produce maximum lift force. Load capacity curves (lift force as function of film thickness) were generated for four advanced turbofan engine operating conditions at relative seal speeds ranging from 17,850 to 29,800 rpm, sealed air pressures from 6 to 42 N/sq cm (9 to 60 psi) absolute and temperatures from 95 to 327 C (203 to 620 F). The relative seal sliding speed range was 152 to 255 m/sec (500 to 836 ft/sec). The analysis showed that the spiral grooves are capable of producing sufficient lift force such that the ring seal will operate in a noncontacting mode over the operating range of typical advanced turbofan engines.

Dirusso, E.↗
NASA NTRS1983

Design analysis of a self-acting spiral-groove ring seal for counter-rotating shafts

A self-acting spiral groove inter-shaft ring seal of nominal 16.33 cm (6.43 in.) diameter for sealing fan bleed air between counter rotating shafts in advanced turbofan engines was analyzed. The analysis focused on the lift force characteristics of the spiral grooves. A NASA Lewis developed computer program for predicting the performance of gas lubricated face seals was used to optimize the spiral groove geometry to produce maximum lift force. Load capacity curves (lift force as function of film thickness) were generated for four advanced turbofan engine operating conditions at relative seal speeds ranging from 17,850 to 29,800 rpm, sealed air pressures from 6 to 42 N/sq cm (9 to 60 Psi) absolute and temperatures from 95 to 327 C (203 to 620 F). The relative seal sliding speed range was 152 to 255 m/sec (500 to 836 ft/sec). The analysis showed that the spiral grooves are capable of producing sufficient lift force such that the ring seal will operate in a noncontacting mode over the operating range of typical advanced turbofan engines. Previously announced in STAR as N83-23306

Di Russo, EL↗