Search NASA⌕ Search

SEARCH · Search NASA

Results for “Rotor Performance”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

An unsteady helicopter rotor-fuselage aerodynamic interaction analysis

A computational method has been developed to treat the unsteady aerodynamic interaction between a helicopter rotor, wake, and fuselage. Two existing codes, a lifting line-prescribed wake rotor analysis and a source panel fuselage analysis, were modified and coupled to allow prediction of unsteady fuselage pressures and airloads. A prescribed displacement technique was developed to position the rotor wake about the fuselage. Also coupled into the method were optional blade dynamics or rigid blade performance analyses to set the rotor operating conditions. Sensitivity studies were performed to determine the influence of the wake and fuselage geometry on the computational results. Solutions were computed for an ellipsoidal fuselage and a four bladed rotor at several advance ratios, using both the classical helix and the generalized distorted wake model. Results are presented that describe the induced velocities, pressures, and airloads on the fuselage and the induced velocities and bound circulation at the rotor. The ability to treat arbitrary geometries was demonstrated using a simulated helicopter fuselage. Initial computations were made to simulate the geometry of an experimental rotor-fuselage interaction study performed at the Georgia Institute of Technology.

Lorber, Peter F.↗
NASA NTRS1952

Effect of Rotor- and Stator-Blade Modifications on Surge Performance of an 11-Stage Axial-Flow Compressor. I - Original Production Compressor of XJ40-WE-6 Engine

An investigation to increase the compressor surge-limit pressure ratio of the XJ40-WE-6 turbojet engine at high equivalent speeds was conducted at the NACA Lewis altitude wind tunnel. This report evaluates the compressor modifications which were restricted to (1) twisting rotor blades (in place) to change blade section angles and (2) inserting new stator diaphragms with different blade angles. Such configuration changes could be incorporated quickly and easily in existing engines at overhaul depots. It was found that slight improvements in the compressor surge limit were possible by compressor blade adjustment. However, some of the modifications also reduced the engine air flow and hence penalized the thrust. The use of a mixer assembly at the compressor outlet improved the surge limit with no appreciable thrust penalty.

Finger, Harold B.↗
NASA NTRS2004

Performance and Flowfield Measurements on a 10-inch Ducted Rotor VTOL UAV

A ducted fan VTOL UAV with a 10-inch diameter rotor was tested in the US Army 7-by 10-Foot Wind Tunnel. The test conditions covered a range of angle of attack from 0 to 110 degrees to the freestream. The tunnel velocity was varied from 0 (simulating a hover condition) to 128 ft/sec in propeller mode. A six-component internal balance measured the aerodynamic loads for a range of model configurations. including the isolated rotor, the isolated duct, and the full configuration of the duct and rotor. For some conditions, hotwire velocity surveys were conducted along the inner and outer surface of the duct and across the downstream wake. In addition, fluorescent oil flow visualization allowed the flow separation patterns inside and outside of the duct to be mapped for a few test conditions. Two different duct shapes were tested to determine the performance effects of leading edge radius. For each duct, a range of rotor tip gap from 1%R to 4.5%R was tested to determine the performance penalty in hover and axial flight. Measured results are presented in terms of hover performance, hover performance in a crosswind, and high angle of attack performance in propeller mode. In each case, the effects of both tip gap and duct leading edge radius are illustrated using measurements. Some of the hover performance issues were also studied using a simple analytical method, and the results agreed with the measurements.

Martin, Preston↗
NASA NTRS1978

Acoustic evaluation of a novel swept-rotor fan

Inlet noise and aerodynamic performance are presented for a high tip speed fan designed with rotor blade leading edge sweep that gives a subsonic component of inlet Mach number normal to the edge at all radii. The intent of the design was to minimize the generation of rotor leading edge shock waves thereby minimizing multiple pure tone noise. Sound power level and spectral comparisons are made with several high-speed fans of conventional design. Results show multiple pure tone noise at levels below those of some of the other fans and this noise was initiated at a higher tip speed. Aerodynamic performance of the fan did not meet design goals for this first build which applied conventional design procedures to the swept fan geometry.

Lucas, J. G.↗
NASA NTRS1978

Acoustic evaluation of a novel swept-rotor fan

Inlet noise and aerodynamic performance are presented for a high tip speed fan designed with rotor blade leading edge sweep that gives a subsonic component of inlet Mach number normal to the edge at all radii. The intent of the design was to minimize the generation of rotor leading edge shock waves thereby minimizing multiple pure tone noise. Sound power level and spectral comparisons are made with several high-speed fans of conventional design. Results showed multiple pure tone noise at levels below those of some of the other fans and this noise was initiated at a higher tip speed. Aerodynamic performance of the fan did not meet design goals for this first build which applied conventional design procedures to the swept fan geometry.

Lucas, J. G.↗
DOE OSTI2025

Underwater thermomagnetic generator for remote marine thermal energy harvesting and sensing

Thermomagnetic generators offer a promising approach for sustainable power generation in remote marine environments. Here, this study presents the design, thermal modeling, and experimental validation of a passively driven underwater thermomagnetic generator developed for powering ocean observation and monitoring sensors. The generator was evaluated under varying working fluids, thermal boundary conditions, and extended operation to assess real-world applicability. Two fluids, deionized water and silicone-based Thermal C5, were tested under simulated shallow- and deep-ocean conditions. Deionized water outperformed Thermal C5, especially in colder environments (~5°C), achieving a peak output of 2.7 mW due to larger temperature gradients and enhanced convective-evaporative heat transfer. Long-duration tests revealed a transient evaporation-condensation cycle that temporarily reduced rotor immersion and performance before stabilizing. The generator powered commercial marine sensors for over 6 h without external batteries, demonstrating the viability of compact, passively cooled thermomagnetic systems for autonomous, off-grid marine sensing.

13 HYDRO ENERGY↗
DOE OSTI2024

Aerodynamic and production comparison of wind farms with downwind versus conventional upwind turbines

Ever-increasing turbine scales and their associated logistical challenges have reignited questions about the performance of downwind rotor configurations. A particular potential benefit of downwind rotor configurations is the farm-scale power increase that may be conferred by tilt-driven downward wake entrainment and associated wake recovery. In this work, a comprehensive aerodynamic analysis is carried out to understand the mechanisms for wake entrainment and recovery across a spectrum of velocity and inflow alignment conditions on a small, structured farm in order to understand the impact of downwind rotors on farm production. The results show that the benefits demonstrated previously in the literature for downwind-rotor farms in aligned flows are fragile, and, outside of strong farm/flow alignment conditions, power production benefits for small farms with downwind rotor configurations are significantly if not completely mitigated by misalignment effects. The work indicates that farm-scale benefits for downwind rotors must be realized either from large-scale entrainment benefits, with more exotic farm arrangements that can take advantage of the aerodynamic effects, or from beneficial fatigue impacts from entrainment of less turbulent outer boundary layer flows.

17 WIND ENERGY↗
DOE OSTI2022

New collective structures in Au 179 and their implications for the triaxial deformation of the Pt 178 core

The extremely neutron-deficient isotope 179 Au has been studied by a combination of in-beam γ-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/2 – , T 1/2 = 328 ns isomer. A new rotational band, associated with the unfavored signature band of the 1⁢ℎ 9/2 ⊕2f⁢ 7/2 proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and T 1/2 = 2.16⁢(8) ⁢µs was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the 1⁢i 13/2 proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new 1⁢ℎ 9/2 ⊕2f 7/2 rotational band is interpreted as due to triaxial deformation of the underlying configuration with β 2 ≈ 0.26 and γ ≈ 27°. In conclusion, observed non-yrast states of the positive-parity 1i 13/2 intruder configuration are interpreted as due to triaxial deformation with β 2 ≈ 0.26 and γ ≈ 20°.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1980

Stabilization of aerodynamically excited turbomachinery with hydrodynamic journal bearings and supports

A method of analyzing the first mode stability and unbalance response of multimass flexible rotors is presented whereby the multimass system is modeled as an equivalent single mass modal model including the effects of rotor flexibility, general linearized hydrodynamic journal bearings, squeeze film bearing supports and rotor aerodynamic cross coupling. Expressions for optimum bearing and support damping are presented for both stability and unbalance response. The method is intended to be used as a preliminary design tool to quickly ascertain the effects of bearing and support changes on rotor-bearing system performance.

Barrett, L. E.↗
NASA NTRS1980

Core compressor exit stage study. Volume 3: Data and performance report for screening test configurations

Rear stage blading designs that have lower losses in their endwall boundary layer regions were developed. Test data and performance results for rotor B, stator B, and stator C - blading designs that offer promise of reducing endwall losses relative to the baseline are given. A low speed research compressor was the principal investigative tool. The tests were conducted using four identical stages of blading so that the test data would be obtained in a true multistage environment.

Wisler, D. C.↗
NASA NTRS1985

Stress analysis of 27% scale model of AH-64 main rotor hub

Stress analysis of an AH-64 27% scale model rotor hub was performed. Component loads and stresses were calculated based upon blade root loads and motions. The static and fatigue analysis indicates positive margins of safety in all components checked. Using the format developed here, the hub can be stress checked for future application.

Hodges, R. V.↗
NASA NTRS1988

Comprehensive rotorcraft analysis methods

The development and application of comprehensive rotorcraft analysis methods in the field of rotorcraft technology are described. These large scale analyses and the resulting computer programs are intended to treat the complex aeromechanical phenomena that describe the behavior of rotorcraft. They may be used to predict rotor aerodynamics, acoustic, performance, stability and control, handling qualities, loads and vibrations, structures, dynamics, and aeroelastic stability characteristics for a variety of applications including research, preliminary and detail design, and evaluation and treatment of field problems. The principal comprehensive methods developed or under development in recent years and generally available to the rotorcraft community because of US Army Aviation Research and Technology Activity (ARTA) sponsorship of all or part of the software systems are the Rotorcraft Flight Simulation (C81), Dynamic System Coupler (DYSCO), Coupled Rotor/Airframe Vibration Analysis Program (SIMVIB), Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD), General Rotorcraft Aeromechanical Stability Program (GRASP), and Second Generation Comprehensive Helicopter Analysis System (2GCHAS).

Stephens, Wendell B.↗
NASA NTRS1990

Experimental performance and acoustic investigation of modern, counterrotating blade concepts

The aerodynamic, acoustic, and aeromechanical performance of counterrotating blade concepts were evaluated both theoretically and experimentally. Analytical methods development and design are addressed. Utilizing the analytical methods which evolved during the conduct of this work, aerodynamic and aeroacoustic predictions were developed, which were compared to NASA and GE wind tunnel test results. The detailed mechanical design and fabrication of five different composite shell/titanium spar counterrotating blade set configurations are presented. Design philosophy, analyses methods, and material geometry are addressed, as well as the influence of aerodynamics, aeromechanics, and aeroacoustics on the design procedures. Blade fabrication and quality control procedures are detailed; bench testing procedures and results of blade integrity verification are presented; and instrumentation associated with the bench testing also is identified. Additional hardware to support specialized testing is described, as are operating blade instrumentation and the associated stress limits. The five counterrotating blade concepts were scaled to a tip diameter of 2 feet, so they could be incorporated into MPS (model propulsion simulators). Aerodynamic and aeroacoustic performance testing was conducted in the NASA Lewis 8 x 6 supersonic and 9 x 15 V/STOL (vertical or short takeoff and landing) wind tunnels and in the GE freejet anechoic test chamber (Cell 41) to generate an experimental data base for these counterrotating blade designs. Test facility and MPS vehicle matrices are provided, and test procedures are presented. Effects on performance of rotor-to-rotor spacing, angle-of-attack, pylon proximity, blade number, reduced-diameter aft blades, and mismatched rotor speeds are addressed. Counterrotating blade and specialized aeromechanical hub stability test results are also furnished.

Hoff, G. E.↗
NASA NTRS1992

Research and applications in structural dynamics and aeroelasticity

Results of some recently completed research programs in aeroelasticity and structural dynamics at the NASA Langley Research Center are presented. It is shown that multifunctional active controls can be used to control flutter and loads on future advanced fighter configurations. A description and early results of an experimental program are presented in order to provide a well documented data base for validating unsteady aerodynamic codes. It is shown that the degradation in aeroelastic behavior due to thermal effects on a hypersonic vehicle can be offset by the use of active controls. The feasibility of using adaptive materials to control flutter is demonstrated experimentally. A description of the latest unstructured grid methods for use in advanced computational unsteady aerodynamic codes is presented. A program to improve the ability of FEMs to predict rotorcraft vibrational characteristics is described. The use of aeroelastic tailoring to improve the performance of tilt rotor vehicles is examined.

Abel, Irving↗
NASA NTRS1993

A critical assessment of UH-60 main rotor blade airfoil data

Many current comprehensive rotorcraft analyses employ lifting-line methods that require main rotor blade airfoil data, typically obtained from wind tunnel tests. In order to effectively evaluate these lifting-line methods, it is of the utmost importance to ensure that the airfoil section data are free of inaccuracies. A critical assessment of the SC1095 and SC1094R8 airfoil data used on the UH-60 main rotor blade was performed for that reason. Nine sources of wind tunnel data were examined, all of which contain SC1095 data and four of which also contain SC1094R8 data. Findings indicate that the most accurate data were generated in 1982 at the 11-Foot Wind Tunnel Facility at NASA Ames Research Center and in 1985 at the 6-inch-by-22-inch transonic wind tunnel facility at Ohio State University. It has not been determined if data from these two sources are sufficiently accurate for their use in comprehensive rotorcraft analytical models of the UH-60. It is recommended that new airfoil tables be created for both airfoils using the existing data. Additional wind tunnel experimentation is also recommended to provide high quality data for correlation with these new airfoil tables.

Totah, Joseph↗
NASA NTRS1993

A critical assessment of UH-60 main rotor blade airfoil data

Many current comprehensive rotorcraft analyses employ lifting-line methods that require main rotor blade airfoil data, typically obtained from wind tunnel tests. In order to effectively evaluate these lifting-line methods, it is of the utmost importance to ensure that the airfoil section data are free of inaccuracies. A critical assessment of the SC1095 and SC1094R8 airfoil data used on the UH-60 main rotor blade was performed for that reason. Nine sources of wind tunnel data were examined, all of which contain SC1095 data and four of which also contain SC1094R8 data. Findings indicate that the most accurate data were generated in 1982 at the 11-Foot Wind Tunnel Facility at NASA Ames Research Center and in 1985 at the 6-inch by 22-inch transonic wind tunnel facility at Ohio State University. It has not been determined if data from these two sources are sufficiently accurate for their use in comprehensive rotorcraft analytical models of the UH-60. It is recommended that new airfoil tables be created for both airfoils using the existing data. Additional wind tunnel experimentation is also recommended to provide high quality data for correlation with these new airfoil tables.

Totah, Joseph↗
NASA NTRS1997

JTAGG II Brush Seal Test Results

The Tri-services JTAGG 2 engine uses two identical brush seals, in tandem, located aft of the high pressure compressor. The engine operating conditions, at intermediate rated power (IRP), for this seal are estimated to be 50,000 rpm (899 ft/sec) speed, 175 psid air to air pressure differential and 1200 F air temperature. The testing was comprised of static air leakage, performance, seal offset, rotor run out tests and a 50 hr endurance test in the NASA Lewis seal rig. Based on the test results, it is concluded that the brush seal design should be able to meet the air leakage flow factor goal of less than 0.004 for the engine IRP operating conditions. For the 4.12 in. i.d. labyrinth seal, 0.005 in. typical radial clearance, at the JTAGG 2 operating conditions, the leakage flow factor is 0.007. The long term seal life can not be predicted accurately due to the limited endurance testing of 50 hr. However, based on the excellent condition of the test seal and rotor after 50 hr of testing, it is anticipated that the seals should easily meet the JTAGG 2 engine test requirement.

Arora, Gul K.↗