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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

A Comparison of Wind Speed Data from Mechanical and Ultrasonic Anemometers

This study compared the performance of mechanical and ultrasonic anemometers at the Eastern Range (ER; Kennedy Space Center and Cape Canaveral Air Force Station on Florida's Atlantic coast) and the Western Range (WR; Vandenberg Air Force Base on California's Pacific coast). Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at the ER and WR for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The current ER and WR weather tower wind instruments are being changed from the current propeller-and-vane (ER) and cup-and-vane (WR) sensors to ultrasonic sensors through the Range Standardization and Automation (RSA) program. The differences between mechanical and ultrasonic techniques have been found to cause differences in the statistics of peak wind speed in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between RSA and current sensors to determine if there are significant differences. Approximately 3 weeks of Legacy and RSA wind data from each range were used in the study, archived during May and June 2005. The ER data spanned the full diurnal cycle, while the WR data was confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on 5 different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The 10 towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The RSA sensors were collocated at the same vertical levels as the present sensors and typically within 15 ft horizontally of each another. Data from a total of 53 RSA ultrasonic sensors, collocated with present sensors were compared. The 1-minute average wind speed/direction and the 1-second peak wind speed/direction were compared.

Short, D.↗
NASA NTRS1995

Internal Acoustics Measurements of a Full Scale Advanced Ducted Propulsor Demonstrator

Acoustics measurements of a Pratt & Whitney full-scale ADP (Advanced Ducted Propulsor), an ultrahigh by-pass ratio engine, were conducted in the NASA Ames 40- by 80-Foot Wind Tunnel. This paper presents data from measurements taken from sensors on a fan exit guide vane in the ADP. Data from two sensors, one at mid-span and the other at the tip of the fan exit guide vane, are presented. At the blade passage frequency (BPF), the levels observed at the various engine and wind speeds were higher at the mid-span sensor than the tip sensor. The coherence between these internal sensors and external microphones were calculated and plotted as a function of angle (angles ranged from 5 degrees to 160 degrees) relative to the ADP longitudinal axis. At the highest engine and wind speeds, the coherence between the tip sensor and the external microphones was observed to decrease at higher multiples of the BPF. These results suggest that the rotor-stator interaction tones are stronger in the mid-span region than at the tip.

Santa Maria, O. L.↗
NASA NTRS1982

Aerodynamic characteristics of a large-scale, twin tilt-nacelle V/STOL model

A subsonic tilt-nacelle V/STOL aircraft configuration is described which is powered by two turbofan engines, mounted on a single carry-through structure that is designed to maintain the thrust axis close to the center of gravity at nacelle incidences of 5-95 deg. Control during V/STOL operation, often from small ship platforms, is achieved by means of a vane assembly that is immersed in each turbofan's exhaust. Wind tunnel test data have been obtained with an 11.2-m wing span model for the vertical-to-horizontal flight transition capability of the concept. It is found that the aircraft can operate over a broad transition corridor, with sufficient maneuver capability about the trim points. The control vane exhibited linear response characteristics over a large deflection range, with little influence from power, angle of attack or ground proximity in hover. The model induced a positive ground effect in hover that increased as wheel height was approached and strake angle increased.

Falarski, M. D.↗
NASA NTRS1983

Aerodynamic performance of a fan stage utilizing Variable Inlet Guide Vanes (VIGVs) for thrust modulation

An experimental research program was conducted in the Lewis Research Center's 9x15-foot (2.74x4.57 m) low speed wind tunnel to evaluate the aerodynamic performance of an inlet and fan system with variable inlet guide vanes (VIGVs) for use on a subsonic V/STOL aircraft. At high VIGV blade angles (lower weight flow and thrust levels), the fan stage was stalled over a major portion of its radius. In spite of the stall, fan blade stresses only exceeded the limits at the most extreme flow conditions. It was found that inlet flow separation does not necessarily lead to poor inlet performance or adverse fan operating conditions. Generally speaking, separated inlet flow did not adversely affect the fan blade stress levels. There were some cases, however, at high VIGV angles and high inlet angles-of-attack where excessive blade stress levels were encountered. An evaluation term made up of the product of the distortion parameter, K alpha, the weight flow and the fan pressure ratio minus one, was found to correlate quite well with the observed blade stress results.

Woollett, R. R.↗
NASA NTRS1991

Multiaxis thrust vectoring using axisymmetric nozzles and postexit vanes on an F/A-18 configuration vehicle

A ground-based investigation was conducted on an operational system of multiaxis thrust vectoring using postexit vanes around an axisymmetric nozzle. This thrust vectoring system will be tested on the NASA F/A-18 High Alpha Research Vehicle (HARV) aircraft. The system provides thrust vectoring capability in both pitch and yaw. Ground based data were gathered from two separate tests at NASA Langley Research Center. The first was a static test in the 16-foot Transonic Tunnel Cold-Jet Facility with a 14.25 percent scale model of the axisymmetric nozzle and the postexit vanes. The second test was conducted in the 30 by 60 foot wind tunnel with a 16 percent F/A-18 complete configuration model. Data from the two sets are being used to develop models of jet plume deflection and thrust loss as a function of vane deflection. In addition, an aerodynamic interaction model based on plume deflection angles will be developed. Results from the scale model nozzle test showed that increased vane deflection caused exhaust plume turning. Aerodynamic interaction effects consisted primarily of favorable interaction of moments and unfavorable interaction of forces caused by the vectored jet plume.

Bowers, Albion H.↗
NASA NTRS2000

The Alternative Low Noise Fan

A 106 bladed fan with a design takeoff tip speed of 1100 ft/sec was hypothesized as reducing perceived noise because of the shift of the blade passing harmonics to frequencies beyond the perceived noise rating range. A 22 in. model of this Alternative Low Noise Fan, ALNF, was tested in the NASA Glenn 9x 15 Wind Tunnel. 'Me fan was tested with a 7 vane long chord stator assembly and a 70 vane conventional stator assembly in both hard and acoustically treated configurations. In addition a partially treated 7 vane configuration was tested wherein the acoustic material between the 7 long chord stators was made inactive. The noise data from the 106 bladed fan with 7 long chord stators in a hard configuration was shown to be around 4 EPNdB quieter than a low tip speed Allison fan at takeoff and around 5 EPNdB quieter at approach. Although the tone noise behaved as hypothesized, the majority of this noise reduction was from reduced broadband noise related to the large number of rotor blades. This 106 bladed ALNF is a research fan designed to push the technology limits and as such is probably not a practical device with present materials technology. However, a low tip speed fan with around 50 blades would be a practical device and calculations indicate that it could be 2 to 3 EPNdB quieter at takeoff and 3 to 4 EPNdB quieter at approach than the Allison fan. 7 vane data compared with 70 vane data indicated that the tone noise was controlled by rotor wake-stator interaction but that the broadband noise is probably controlled by the interaction of the rotor with incoming flows. A possible multiple pure tone noise reduction technique for a fan/acoustic treatment system was identified. The data from the fully treated configuration showed significant noise reductions over a large frequency range thereby providing a real tribute to this bulk absorber treatment design. The tone noise data with the partially treated 7 vane configuration indicated that acoustic material in the source noise generation region may be more effective than similar material outside of the generation region.

Dittmar, James H.↗
NASA NTRS2010

Boundary-layer-ingesting inlet flow control system

A system for reducing distortion at the aerodynamic interface plane of a boundary-layer-ingesting inlet using a combination of active and passive flow control devices is disclosed. Active flow control jets and vortex generating vanes are used in combination to reduce distortion across a range of inlet operating conditions. Together, the vortex generating vanes can reduce most of the inlet distortion and the active flow control jets can be used at a significantly reduced control jet mass flow rate to make sure the inlet distortion stays low as the inlet mass flow rate varies. Overall inlet distortion, measured and described as average SAE circumferential distortion descriptor, was maintained at a value of 0.02 or less. Advantageous arrangements and orientations of the active flow control jets and the vortex generating vanes were developed using computational fluid dynamics simulations and wind tunnel experimentations.

Owens, Lewis R.↗
NASA NTRS2011

Fundamental Ice Crystal Accretion Physics Studies

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice-crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 grams per cubic meter, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 millimeters in 3 minutes. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Currie, Tom↗
NASA NTRS2012

Fundamental Ice Crystal Accretion Physics Studies

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 g/m3, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 mm in 3 min. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component such as a stator blade to degrade significantly, and could damage downstream components if shed.

Struk, Peter M.↗
NASA NTRS2016

Numerical Simulation of a Complete Low-Speed Wind Tunnel Circuit

A numerical simulation of the complete circuit of the NASA Langley 14 x 22-ft low-speed wind tunnel is described. Inside the circuit, all turning vanes are modeled as well as the five flow control vanes downstream of the 1st corner. The fan drive system is modeled using an actuator disk for the fan blades coupled with the fan nacelle. All the surfaces are modeled as viscous walls except the turning vanes, which were modeled as inviscid surfaces. NASA Langley's TetrUSS unstructured grid software was used for grid generation and flow simulation. Two turbulence models were employed in the present study, namely, the one-equation Spalart-Allmaras model and the shear stress transport (SST) model of Menter. The paper shows the flow characteristics in the circuit and compares the results with experimental data where available.

Nayani, Sudheer N.↗
NASA NTRS1983

Aerodynamic performance of a fan stage utilizing variable inlet guide vanes (VIGV's) for thrust modulation

An experimental research program was conducted in the Lewis Research Center's 9 x 15-foot (2.74 x 4.57 m) low speed wind tunnel to evaluate the aerodynamic performance of an inlet and fan system with variable inlet guide vanes (VIGVs) for use on a subsonic V/STOL aircraft. At high VIGV blade angles (lower weight flow and thrust levels), the fan stage was stalled over a major portion of its radius. In spite of the stall, fan blade stresses only exceeded the limits at the most extreme flow conditions. It was found that inlet flow separation does not necessarily lead to poor inlet performance or adverse fan operating conditions. Generally speaking, separated inlet flow did not adversely affect the fan blade stress levels. There were some cases, however, at high VIGV angles and high inlet angles-of-attack where excessive blade stress levels were encountered. An evaluation term made up of the product of the distortion parameter, K alpha, the weight flow and the fan pressure ratio minus one, was found to correlate quite well with the observed blade stress results. Previously announced in STAR as N83-27957

Woollett, R. R.↗
NASA NTRS2009

Testing and Performance Verification of a High Bypass Ratio Turbofan Rotor in an Internal Flow Component Test Facility

A 1/5 scale model rotor representative of a current technology, high bypass ratio, turbofan engine was installed and tested in the W8 single-stage, high-speed, compressor test facility at NASA Glenn Research Center (GRC). The same fan rotor was tested previously in the GRC 9x15 Low Speed Wind Tunnel as a fan module consisting of the rotor and outlet guide vanes mounted in a flight-like nacelle. The W8 test verified that the aerodynamic performance and detailed flow field of the rotor as installed in W8 were representative of the wind tunnel fan module installation. Modifications to W8 were necessary to ensure that this internal flow facility would have a flow field at the test package that is representative of flow conditions in the wind tunnel installation. Inlet flow conditioning was designed and installed in W8 to lower the fan face turbulence intensity to less than 1.0 percent in order to better match the wind tunnel operating environment. Also, inlet bleed was added to thin the casing boundary layer to be more representative of a flight nacelle boundary layer. On the 100 percent speed operating line the fan pressure rise and mass flow rate agreed with the wind tunnel data to within 1 percent. Detailed hot film surveys of the inlet flow, inlet boundary layer and fan exit flow were compared to results from the wind tunnel. The effect of inlet casing boundary layer thickness on fan performance was quantified. Challenges and lessons learned from testing this high flow, low static pressure rise fan in an internal flow facility are discussed.

VanZante, Dale E.↗
NASA NTRS1985

Static internal performance of a single-engine onaxisymmetric-nozzle vaned-thrust-reverser design with thrust modulation capabilities

An investigation has been conducted at wind-off conditions in the stati-test facility of the Langley 16-Foot Transonic Tunnel. The tests were conducted on a single-engine reverser configuration with partial and full reverse-thrust modulation capabilities. The reverser design had four ports with equal areas. These ports were angled outboard 30 deg from the vertical impart of a splay angle to the reverse exhaust flow. This splaying of reverser flow was intended to prevent impingement of exhaust flow on empennage surfaces and to help avoid inlet reingestion of exhaust gas when the reverser is integrated into an actual airplane configuration. External vane boxes were located directly over each of the four ports to provide variation of reverser efflux angle from 140 deg to 26 deg (measured forward from the horizontal reference axis). The reverser model was tested with both a butterfly-type inner door and an internal slider door to provide area control for each individual port. In addition, main nozzle throat area and vector angle were varied to examine various methods of modulating thrust levels. Other model variables included vane box configuration (four or six vanes per box), orientation of external vane boxes with respect to internal port walls (splay angle shims), and vane box sideplates. Nozzle pressure ratio was varied from 2.0 approximately 7.0.

Leavitt, L. D.↗
NASA NTRS1973

Vertical axis wind rotors: Status and potential

The design and application of a vertical axis wind rotor is reported that operates as a two stage turbine wherein the wind impinging on the concave side is circulated through the center of the rotor to the back of the convex side, thus decreasing what might otherwise be a high negative pressure region. Successful applications of this wind rotor to water pumps, ship propulsion, and building ventilators are reported. Also shown is the feasibility of using the energy in ocean waves to drive the rotor. An analysis of the impact of rotor aspect ratio on rotor acceleration shows that the amount of venting between rotor vanes has a very significant effect on rotor speed for a given wind speed.

Vance, W.↗
NASA NTRS2005

An Empirical Model for Vane-Type Vortex Generators in a Navier-Stokes Code

An empirical model which simulates the effects of vane-type vortex generators in ducts was incorporated into the Wind-US Navier-Stokes computational fluid dynamics code. The model enables the effects of the vortex generators to be simulated without defining the details of the geometry within the grid, and makes it practical for researchers to evaluate multiple combinations of vortex generator arrangements. The model determines the strength of each vortex based on the generator geometry and the local flow conditions. Validation results are presented for flow in a straight pipe with a counter-rotating vortex generator arrangement, and the results are compared with experimental data and computational simulations using a gridded vane generator. Results are also presented for vortex generator arrays in two S-duct diffusers, along with accompanying experimental data. The effects of grid resolution and turbulence model are also examined.

Dudek, Julianne C.↗
NASA NTRS1989

The K-Gill - A twin propeller-vane anemometer for measurements of atmospheric turbulence

A twin propeller-vane anemometer developed at the University of British Columbia was successfully used for unattended measurement of atmospheric turbulence over extended periods of time during moderate to high winds in the presence of sea spray. In this paper, a new design in twin propeller-vane anemometers is introduced. The instrument consists of two Gill anemometers mounted on a vane. The propeller shafts, one pointing up and the other pointing down, make an angle of 45 deg with the horizontal (hence, the name K-Gill). In addition to the desirable characteristics of the earlier design the K-Gill has symmetry, so that updraft and downdraft winds are measured with equal sensitivity. An algorithm for obtaining the vertical and downstream horizontal components of the wind velocity is described. Various sources of error and their magnitudes are discussed.

Atakturk, Serhad S.↗
NASA NTRS1996

Wind tunnel test results of a 1/8-scale fan-in-wing model

A 1/8-scale model of a fan-in-wing concept considered for development by Grumman Aerospace Corporation for the U.S. Army was tested in the Langley 14- by 22-Foot Subsonic Tunnel. Hover testing, which included height above a pressure-instrumented ground plane, angle of pitch, and angle of roll for a range of fan thrust, was conducted in a model preparation area near the tunnel. The air loads and surface pressures on the model were measured for several configurations in the model preparation area and in the tunnel. The major hover configuration change was varying the angles of the vanes attached to the exit of the fans for producing propulsive force. As the model height above the ground was decreased, there was a significant variation of thrust-removed normal force with constant fan speed. The greatest variation was generally for the height-to-fan exit diameter ratio of less than 2.5; the variation was reduced by deflecting fan exit flow outboard with the vanes. In the tunnel angles of pitch and sideslip, height above the tunnel floor, and wind speed were varied for a range of fan thrust and different vane angle configurations. Other configuration features such as flap deflections and tail incidence were evaluated as well. Though the V-tail empennage provided an increase in static longitudinal stability, the total model configuration remained unstable.

Wilson, John C.↗