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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Results of acoustic tests of a Prop-Fan model

Results of acoustic tests in a low speed open jet anechoic wind tunnel are presented for a counter rotation Prop-Fan model. The model tested had 5 front and 5 rear rotor blades with swept planform. Noise spectra are presented showing the influence of operating and configuration variables such as: (1) power absorption, (2) tip speed, (3) rotor-rotor spacing, (4) power split between the front and rear blade rows, (5) variation of the RPM ratio between front and rear blade rows, (6) tractor versus pusher (pylon effects), and (7) angle of attack. In addition to model scale results, calculated levels derived from test are presented showing the influence of the above variables on Effective Perceived Noise Level of a 13.1 ft diameter Prop-Fan at a flyover distance of 1500 ft. It was found that the strongest effects are caused by tip speed and power absorption. A significant finding was that there is an optimum operating tip speed for minimum noise for a given power absorption. Effects of other parametric variations are generally small but measurable. In order to minimize noise to meet airplane certification limits, operation at moderate tip speeds and power absorption is shown to be desirable. Accuracy of predicted Effective Perceived Noise Level is shown to be good with the best accuracy in the 590 to 670 ft/sec tip speed range.

Metzger, F.B.↗
NASA NTRS1983

Incidence loss for fan turbine rotor blade in two-dimensional cascade

The effect of incidence angle on the aerodynamic performance of a fan turbine rotor blade was investigated experimentally in a two dimensional cascade. The test covered a range of incidence angles from -15 deg to 10 deg and exit ideal critical velocity ratios from 0.75 to 0.95. The principal measurements were blade-surface static pressures and cross-channel survey of exit total pressure, static pressure, and flow angle. Flow adjacent to surfaces was examined using a visualization technique. The results of the investigation include blade-surface velocity distribution and overall kinetic energy loss coefficients for the incidence angles and exit velocity ratios tested. The measured losses are compared with those from a reference core turbine rotor blade and also with two common analytical methods of predicting incidence loss.

Kline, J. F.↗
NASA NTRS1979

Experimental evaluation of the effect of inlet distortion on compressor blade vibrations

Compressor rotor strain gage data from an engine test conducted with an inlet screen distortion were reduced and analyzed. These data are compared to data obtained from the same engine without inlet pressure distortion to determine the net effect of the distortion on the vibratory response of the compressor blades. The results obtained are presented.

Lubomski, J. F.↗
NASA NTRS1979

Experimental evaluation of the effect of inlet distortion on compressor blade vibrations

Compressor rotor strain gage data from an engine test conducted with an inlet screen distortion were reduced and analyzed. The data were compared to results obtained from the same engine without inlet pressure distortion to determine the net effect of the distortion on the vibratory response of the compressor blades. The effect of the distortion was found to be most prominent in the first three compressor stages, with the rotor speed establishing the period of the complex wave and, consequently, the frequencies of all the higher engine order excitations. At certain speeds it was observed that the complex pressure wave had the frequency content to excite a number of modes simultaneously, although the overall magnitudes were small and well within allowable stress limits.

Lubomski, J. F.↗
DOE OSTI2014

Predicting Power for a Scaled‐up Non‐Newtonian Biomass Slurry

Abstract High‐solids biomass slurries exhibit non‐Newtonian behavior with a yield stress and require high power input for mixing. The goals were to determine the effect of scale and geometry on power number P 0 , and estimate the power for mixing a pretreated biomass slurry in a 3.8 million L hydrolysis reactor of conventional design. A lab‐scale computational fluid dynamics model was validated against experimental data and then scaled up. A pitched‐blade turbine and A310 hydrofoil were tested for various geometric arrangements. Flow was transitional; laminar and turbulence models resulted in equivalent P 0 which increased with scale. The ratio of impeller diameter to tank diameter affected P 0 for both impellers, but impeller clearance to tank diameter affected P 0 only for the A310. At least 2 MW is required to operate at this scale.

Russ, David C.↗
DOE OSTI2023

TEAMER: Experimental performance characterization of a shrouded axial-flow turbine

Sitkana has developed a shrouded hydrokinetic turbine with a modular, low-cost design that can be scaled to meet the needs of remote communities. With technical support from the University of Washington, Sitkana sought to experimentally characterize the mechanical power and structural loads of various 1:3.3 scale rotor geometries. In all, 11 different rotor geometries were characterized with variations in height-to-diameter ratio, blade number, and blade type (foiled versus flat). All tests were conducted in Reynolds-independent flow conditions in the Alice C. Tyler Flume at the University of Washington. Results allow Sitkana to (1) refine the optimal rotor geometry, (2) validate numerical models, and (3) predict power output for a full-scale system. This project is part of the TEAMER RFTS 8 (request for technical support) program.

16 TIDAL AND WAVE POWER↗
DOE OSTI2020

Within and Among Fish Species Differences in Simulated Turbine Blade Strike Mortality: Limits on the Use of Surrogacy for Untested Species

Use of surrogacy remains a useful method for prioritizing research on representatives of at-risk groups of fishes, yet quantifiable evidence in support of its use is generally not available. Blade strike impact represents one of the most traumatic stressors experienced by fish during non-volitional movements through hydropower turbines. Here, we use data generated from laboratory trials on blade strike impact experiments to directly test use of surrogacy for salmonid and clupeid fishes. Results of logistic regression indicated that a -taxonomic (genus) variable was not a significant predictor of mortality among large rainbow trout and brook trout. Similar results were found for young-of-the-year shad species, but genus-level taxonomy was a significant predictor of mortality while species was not. Multivariate analysis of morphometric data showed that shad clustered together based on similarities in fish shape which was also closely associated with genus. Logistic regression including size as a major covariate suggested total fish length was not a significant predictor of mortality, yet dose–response data suggest differential susceptibility to lower strike velocities. We suggest that use of surrogacy among species is justifiable but should be avoided within a species since the effects of size remain unclear.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Site Selection for Field Testing of a Marine Hydrokinetic Turbine Platform to Serve as a Floating Unmanned Mobile Recharging Station for Aerial Drones

Abstract Expanding applications of unmanned aerial vehicles (UAVs) in coastal areas suggests a need for stations along or close to the coast where the UAV batteries can be easily recharged. A small-scale low flow marine current turbine in support of a floating autonomous recharge station for small UAVs has been designed and assembled at Florida Atlantic University and is being prepared for field testing. Surveys of identified test sites in the Intracoastal Waterways and at open ocean locations are being conducted to determine their suitability in meeting resource, system design and permitting requirements. A sensor platform has been developed for measuring local currents at the identified sites in support of resource characterization. Two out of the eight sites surveyed in the Intracoastal Waterways are found to meet the field-testing requirements for current resource, water depth, and sea bottom conditions. Planned field testing will include parametric characterization studies of the performance of the current turbine for a range of turbine blade configurations, current speeds, turbine wheel submergence levels, and test site location (channeled flow vs open ocean flow).

McKinney, Adriana Lynell↗
NASA NTRS1977

Aerodynamic characteristics of a 1/6-scale powered model of the rotor systems research aircraft

A wind-tunnel investigation was conducted to determine the effects of the main-rotor wake on the aerodynamic characteristics of the rotor systems research aircraft (RSRA). For the investigation, a 1/6-scale model with a four-blade articulated main rotor was used. Tests were conducted with and without the main rotor. Both the helicopter and the compound helicopter were tested. The latter configuration included the auxiliary thrust engines and the variable-incidence wing. Data were obtained over ranges of angle of attack, angle of sideslip, and main-rotor collective pitch angle at several main-rotor advance ratios. Results are presented for the total loads on the airframe as well as the loads on the rotor, the wing, and the tail. The results indicated that without the effect of the rotor wake, the RSRA had static longitudinal and directional stability and positive effective dihedral. With the effect of the main rotor and its wake, the RSRA exhibited longitudinal instability but retained static directional stability and positive effective dihedral.

Mineck, R. E.↗
NASA NTRS1979

Advanced turbo-prop airplane interior noise reduction-source definition

Acoustic pressure amplitudes and phases were measured in model scale on the surface of a rigid semicylinder mounted in an acoustically treated wind tunnel near a prop-fan (an advanced turboprop with many swept blades) model. Operating conditions during the test simulated those of a prop-fan at 0.8 Mach number cruise. Acoustic pressure amplitude and phase contours were defined on the semicylinder surface. Measurements obtained without the semi-cylinder in place were used to establish the magnitude of pressure doubling for an aircraft fuselage located near a prop-fan. Pressure doubling effects were found to be 6dB at 90 deg incidence decreasing to no effect at grazing incidence. Comparisons of measurements with predictions made using a recently developed prop-fan noise prediction theory which includes linear and non-linear source terms showed good agreement in phase and in peak noise amplitude. Predictions of noise amplitude and phase contours, including pressure doubling effects derived from test, are included for a full scale prop-fan installation.

Magliozzi, B.↗
NASA NTRS1980

Practical design considerations for a flightworthy higher harmonic control system

The paper discusses the design of a higher harmonic blade pitch control system for flight testing on an OH-6A helicopter. Alternative designs for both the mechanical and electronic subsystems are also presented. Among the recommendations set forth are: (1) use electronic analog methods instead of FFT software, delegating spectral analysis and self testing to an Electronic Control Unit; (2) use a digital rather than analog computer for increased flexibility in solution processing; and (3) locate HHC actuators in the nonrotating system and separate these actuators from the primary control system. It is concluded that a target weight for a prototype control system would be less than 1% of design gross weight and the production weight of the future HHC system may be 0.5 of the weight of the aircraft.

Wood, E. R.↗
NASA NTRS1980

Zero-length, slotted-lip inlet for subsonic military aircraft

Zero-length, slotted-lip inlet performance and associated fan blade stresses were determined during model tests using a 20-inch diameter fan simulator in the NASA-LeRC 9- by 15-foot low-speed wind tunnel. The model configuration variables consisted of inlet contraction ratio, slot width, circumferential extent of slot fillers, and length of a constant area section between the inlet throat and fan face. Inlet configurations having contraction ratios of 1.2 and 1.3 satisfied all critical low-speed inlet operating requirements for a fixed horizontal nacelle and tilt-nacelle-type subsonic V/STOL aircraft, respectively. Relative to a conventional axisymmetric tilt-nacelle inlet, the zero-length, slotted-lip inlet has a 27-percent smaller inlet lip contraction ratio, an 83-percent shorter total length, and a 5-percent smaller maximum cowl diameter.

Glasgow, E. R.↗
NASA NTRS1981

Zero-length inlets for subsonic V/STOL aircraft

Zero-length inlet performance and associated fan blade stresses were determined during model tests in the NASA-LeRC 9-by 15-foot low-speed wind tunnel. The inlet models, which were installed on a 20-inch diameter fan unit, had different inlet lip contraction ratios as well as unslotted, slotted, and double slotted inlet lips. The inlet angle-of-attack boundaries for onset of flow separation were identified and compared to the operating requirements of several generically different subsonic V/STOL aircraft. The zero-length inlets, especially those with slotted lips, were able to satisfy these requirements without compromising the maximum cowl forebody radius. As an aid to the inlet design process, a unique relationship was established between the maximum surface Mach number associated with the separation boundary and the maximum-to-throat surface velocity ratio.

Glasgow, E. R.↗
NASA NTRS1982

Interim review of the Energy Efficient Engine /E3/ Program

The NASA-sponsored Energy Efficient Engine (E3) Program, which is now in its fourth year, is assessed from the viewpoint of one of its research contractors. Attention is given to the development status of the shroudless fan, segmented combustor and exhaust mixer components which are encompassed by the program. The shroudless fan blades are two-thirds hollow for lightness, and are fabricated by means of plies and cores subjected to hot isostatic pressing diffusion bonding. The combustor's segmented liner is cast from turbine blade materials. Exhaust mixer flow visualization tests are described. Consideration is given to the effects of integrating the technology described with the low and high pressure advanced turbines whose development is also part of the E3 program.

Gardner, W. B.↗
NASA NTRS1982

JT90 Ceramic Outer Air Seal System Refinement Program, Phase 2

The sprayed ceramic gas turbine outer air seal system was tested in two JT9D engines to substantiate the abradability and durability of the seals. Of particular significance was that one of the tests, a 150 hour 1000 cycle endurance program at nominal JT9D operating conditions, was completed with minimal effect on the seals and received Federal Aviation Administration cognizance with respect to potential field service use by the airlines. The other engine test completed 1825 endurance cycles at severe operating conditions and no burn through or other serious defects in the structural integrity of a seal segment was observed. These test results combined with other Pratt and Whitney Aircraft engine tests substantiate the potential of the ceramic outer air seal system to attain the durability goal of 50000 hour engine operating capability. Both engine tests subjected the seals to intentional blade rubs and demonstrated good abradability with volume wear ratios greater than 100, far exceeding the design goal of 10. The improved volume wear ratio will allow the turbine tip clearance to be reduced, thereby resulting in an estimated thrust specific fuel consumption improvement of 0.3 percent.

Shiembob, L. T.↗
NASA NTRS1982

Surface protection overview

A first-cut integrated environmental attack life prediction methodology for hot section components is addressed. The HOST program is concerned with oxidation and hot corrosion attack of metallic coatings as well as their degradation by interdiffusion with the substrate. The effects of the environment and coatings on creep/fatigue behavior are being addressed through a joint effort with the Fatigue sub-project. An initial effort will attempt to scope the problem of thermal barrier coating life prediction. Verification of models will be carried out through benchmark rig tests including a 4 atm. replaceable blade turbine and a 50 atm. pressurized burner rig.

Levine, S. R.↗