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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Performance optimization of helicopter rotor blades

As part of a center-wide activity at NASA Langley Research Center to develop multidisciplinary design procedures by accounting for discipline interactions, a performance design optimization procedure is developed. The procedure optimizes the aerodynamic performance of rotor blades by selecting the point of taper initiation, root chord, taper ratio, and maximum twist which minimize hover horsepower while not degrading forward flight performance. The procedure uses HOVT (a strip theory momentum analysis) to compute the horse power required for hover and the comprehensive helicopter analysis program CAMRAD to compute the horsepower required for forward flight and maneuver. The optimization algorithm consists of the general purpose optimization program CONMIN and approximate analyses. Sensitivity analyses consisting of derivatives of the objective function and constraints are carried out by forward finite differences. The procedure is applied to a test problem which is an analytical model of a wind tunnel model of a utility rotor blade.

Walsh, Joanne L.↗
NASA NTRS1987

Helicopter blade dynamic loads measured during performance testing of two scaled rotors

A test to determine the performance differences between the 27-percent-scale models of two rotors for the U.S. Army AH-64 helicopter was conducted in the Langley 14- by 22-Foot Subsonic Tunnel. One rotor, referred to as the baseline rotor, simulated the geometry and dynamic characteristics of the production baseline rotor, and the other rotor, referred to as the advanced rotor, was designed to have improved hover performance. During the performance test, the dynamic pitch-link forces and blade bending and torsion moments were also measured. Dynamic data from the forward flight investigation are reduced and presented. The advanced blade set was designed to have dynamic characteristics similar to those of the baseline rotor so that test conditions would not be limited by potential rotor instability and blade resonances, and so that the measured performance increments could be considered to be due purely to aerodynamic causes. Data show consistent trends with advance ratio for both blade sets with generally higher oscillatory loads occurring for the advanced blade set when compared with the baseline blade set.

Berry, John D.↗
NASA NTRS1992

Aerodynamic performance optimization of a rotor blade using a neural network as the analysis

This paper describes the use of neural networks as a replacement for rotor analyses in a conventional aerodynamic performance optimization procedure. The optimization procedure minimizes an objective function, a linear combination of horsepower required for hover, forward flight, and maneuver. The design variables are pretwist, taper initiation, taper ratio, and blade root chord. Constraints consist of limits on horsepower required (for hover, forward flight, and maneuver), stall, trim, and minimum tip chord. Neural network analyses agree with conventional analyses.

Lamarsh, William J., II↗
NASA NTRS1986

Hover performance tests of baseline metal and Advanced Technology Blade (ATB) rotor systems for the XV-15 tilt rotor aircraft

Rotor hover performance data were obtained for two full-scale rotor systems designed for the XV-15 Tilt Rotor Research Aircraft. One rotor employed the rectangular planform metal blades (rotor solidity = 0.089) which were used on the initial flight configuration of the XV-15. The second rotor configuration examined the nonlinear taper, composite-construction, Advanced Technology Blade (ATB), (rotor solidity = 0.10) designed to replace the metal blades on the XV-15. Variations of the baseline ATB tip and cuff shapes were also tested. A new six-component rotor force and moment balance designed to obtain highly accurate data over a broad range of thrust and torque conditions is described. The test data are presented in nondimensional coefficient form for the performance results, and in dimensional form for the steady and alternating loads. Some wake and acoustic data are also shown.

Bartie, K.↗
NASA NTRS1983

Effects of aerodynamic interaction between main and tail rotors on helicopter hover performance and noise

A model test was conducted to determine the effects of aerodynamic interaction between main rotor, tail rotor, and vertical fin on helicopter performance and noise in hover out of ground effect. The experimental data were obtained from hover tests performed with a .151 scale Model 222 main rotor, tail rotor and vertical fin. Of primary interest was the effect of location of the tail rotor with respect to the main rotor. Penalties on main rotor power due to interaction with the tail rotor ranged up to 3% depending upon tail rotor location and orientation. Penalties on tail rotor power due to fin blockage alone ranged up to 10% for pusher tail rotors and up to 50% for tractor tail rotors. The main rotor wake had only a second order effect on these tail rotor/fin interactions. Design charts are presented showing the penalties on main rotor power as a function of the relative location of the tail rotor.

Menger, R. P.↗
NASA NTRS2018

Generation of Performance Model for the Aeolian Wind Tunnel (AWT) Rotor at Reduced Pressure

The NASA Jet Propulsion Laboratory (JPL) designed the Mars Helicopter (MH) in collaboration with AeroVironment Inc., NASA Ames Research Center, and NASA Langley Research Center to explore the possibility of a vertical takeoff and landing (VTOL) Unmanned Aerial Vehicle (UAV) for flight on Mars. A 40-inch-diameter Aeolian Wind Tunnel (AWT) rotor, roughly approximating the proposed MH design by JPL, was tested in forward flight at Mars atmospheric pressure at the NASA Ames Planetary Aeolian Laboratory (PAL) in support of MH research efforts. This report describes the generation of the rotor model used to correlate with that experimental effort as reported by Ament and Koning. The 40-inch-diameter rotor was 3D-scanned and transformed into an airfoil deck. The scanned rotor airfoil sections are analyzed using C81 Generator (C81Gen) to generate the sectional aerodynamic coefficients for comprehensive analyses. A mid-fidelity computational fluid dynamics (CFD) simulation using Rotorcraft CFD (RotCFD) is pursued to efficiently estimate rotor hover and forward flight performance. Simulations at two pressures, 7 mbar (approximate Martian atmospheric pressure) and 1018 mbar (1 atmosphere), are performed to gain an understanding of the performance differences and Reynolds number effects observed. Experimental 1-atmosphere thrust for single- and dual-rotor isolated hover cases correlate well with the modeled rotor. Performance results at reduced pressure (7 mbar) show a drastic decrease in lift for equivalent RPMs tested at 1 atmosphere. Although this is primarily due to pressure reduction, Reynolds number effects also contribute to this decrease, as airfoil lift and drag coefficients are affected when compared with 1-atmosphere results. Further, simulated rotor power coefficient shows drastic increases at reduced pressures, attributed to laminar boundary layer separation, as described in Koning et al. for the MH rotor analysis. PAL experimental Martian Surface Wind Tunnel (MARSWIT) results are presented in the paper by Ament and Koning. The very low Reynolds number range is currently not well understood and presents various challenges for both experimentation and simulation.

Koning, Witold J. F.↗
NASA NTRS1974

Effect of damper on overall and blade-element performance of a compressor rotor having a tip speed of 1151 feet per second and an aspect ratio of 3.6

The overall and blade-element performance of two configurations of a moderately high aspect ratio transonic compressor rotor are presented. The subject rotor has conventional blade dampers. The performance is compared with a rotor utilizing dual wire friction dampers. At design speed the subject achieved a pressure ratio of 1.52 and efficiency of 0.89 at a near design weight flow of 72.1 pounds per second. The rotor with wire dampers gave consistently higher pressure ratios at each speed, but efficiencies for the two rotors were about the same. Stall margin for the subject rotor was 20.4 percent, but for the wire damped rotor only 4.0 percent.

Lewis, G. W.↗
NASA NTRS1972

Optimum performance of static propellers and rotors.

A criterion for the optimum performance of static propellers and hovering helicopter rotors is developed. Numerical results are presented for the optimum radial distributions of circulation and inflow at the propeller disk and relating the optimum power coefficient and the figure of merit to the thrust coefficient. It is shown that the present theory, which fully accounts for the effect of slipstream rotation, predicts optimum distributions of circulation and inflow that differ significantly from those based on approximate methods.

Wu, J. C.↗
NASA NTRS1987

Results of the integration of a transonic full-potential analysis program with a free-wake lifting-line program for hovering rotors

The hovering performance predictions of the TFAR1 and OPLIN codes and the experimental data are discussed. The TFAR1 program solves the full-potential equation in a rotor-fixed coordinate system by use of the line relaxation method. The OPLIN program calculates the positions of wake vortices and rotor performance using the influence-coefficient-and-lifing-line method. The two programs are combined by adding the induced velocities from the OPLIN code to the near flow-field of the rotor from the TFAR1 code. Results show that the TFAR1 program converges better with the downwash-coupling method than the twist correction method to include the wake downwash.

Chung, Song-Young↗
NASA NTRS1977

ENGINEL: A single rotor turbojet engine cycle match performance program

ENGINEL is a computer program which was developed to generate the design and off-design performance of a single rotor turbojet engine with or without afterburning using a cycle match procedure. It is capable of producing engine performance over a wide range of altitudes and Mach numbers. The flexibility, of operating with a variable geometry turbine, for improved off-design fuel consumption or with a fixed geometry turbine as in conventional turbojets, has been incorporated. In addition, the option of generation engine performance with JP4, liquid hydrogen or methane as fuel is provided.

Lovell, W. A.↗
NASA NTRS1972

Comparison of the effect of two damper sizes on the performance of a low-solidity axial-flow transonic compressor rotor

The experimental performance of a 20-inch-diameter axial-flow transonic compressor rotor with small dampers is presented. The compressor rotor was tested earlier with large dampers which were twice in size, and comparisons of overall performance and radial distributions of selected flow and performance parameters are made. The rotor with small dampers experienced lower losses in the damper region which resulted in locally higher values of temperature rise efficiency and total pressure ratio. However, there was no appreciable effect on overall efficiency and pressure ratio. A greater stall margin was measured for the rotor with small dampers at design speed, but at 70 and 90 percent of design speed the rotor with large dampers had somewhat greater flow range.

Lewis, G. W., Jr.↗
NASA NTRSDate not supplied

Data Processing and Analysis of Performance Measurements From Ingenuity Rotors in the Jet Propulsion Laboratory 25-Ft Space Simulator

The success of Ingenuity completing over 71 flights on Mars has resulted in the possible use of two further optimized Ingenuity-sized helicopters to retrieve samples for the planned Mars Sample Return campaign. Data to validate performance for several rotor speeds, densities, configurations, and collectives will aid in the design process and help in understanding Ingenuity’s current performance limitations. Tests were performed at the Jet Propulsion Laboratory (JPL) in the 25-foot Space Simulator, which include the Engineering Design Model 1 (EDM-1) with and without a cruciform box, and the Transonic Rotor Test (TRT) which is a single rotor setup featuring the same blade geometry as EDM-1 but designed to spin at much higher RPMs. The experimental setup, test matrix, data processing, data quality, and the performance results for EDM1 and TRT campaigns are presented.

Processing↗
DOE OSTI2023

Aerodynamic Rotor Design for a 25 MW Offshore Downwind Turbine

Continuously increasing offshore wind turbine scales require rotor designs that maximize power and performance. Downwind rotors offer advantages in lower mass due to reduced potential for tower strike, and is especially true at large scales, e.g., for a 25 MW turbine. In this study, three 25 MW downwind rotors, each with different prescribed lift coefficient distributions were designed (chord, geometry, and twist) and compared to maximize power production at unprecedented scales and Reynolds numbers, including a new approach to optimize rotor tilt and coning based on aeroelastic effects. To achieve this objective the design process was focused on achieving high power coefficients, while maximizing swept area and minimizing blade mass. Maximizing swept area was achieved by prescribing pre-cone and shaft tilt angles to ensure the aeroelastic orientation when the blades point upwards was nearly vertical at nearly rated conditions. Maximizing the power coefficient was achieved by prescribing axial induction factor and lift coefficient distributions which were then used as inputs for an inverse rotor design tool. The resulting rotors were then simulated to compare performance and subsequently optimized for minimum rotor mass. To achieve these goals, a high Reynolds number design space was developed using computational predictions as well as new empirical correlations for flatback airfoil drag and maximum lift. Within this design space, three rotors of small, medium and large chords were considered for clean airfoil conditions (effects of premature transition were also considered but did not significantly modify the design space). The results indicated that the medium chord design provided the best performance, producing the highest power in Region 2 from simulations while resulting in the lowest rotor mass, both of which support minimum LCOE. The methodology developed herein can be used for the design of other extreme-scale (upwind and downwind) turbines.

downwind rotors↗
NASA NTRS2001

Wind Tunnel Evaluation of a Model Helicopter Main-Rotor Blade With Slotted Airfoils at the Tip

Data for rotors using unconventional airfoils are of interest to permit an evaluation of this technology's capability to meet the U.S. Army's need for increased helicopter mission effectiveness and improved safety and survivability. Thus, an experimental investigation was conducted in the Langley Transonic Dynamics Tunnel (TDT) to evaluate the effect of using slotted airfoils in the rotor blade tip region (85 to 100 percent radius) on rotor aerodynamic performance and loads. Four rotor configurations were tested in forward flight at advance ratios from 0.15 to 0.45 and in hover in-ground effect. The hover tip Mach number was 0.627, which is representative of a design point of 4000-ft geometric altitude and a temperature of 95 F. The baseline rotor configuration had a conventional single-element airfoil in the tip region. A second rotor configuration had a forward-slotted airfoil with a -6 deg slat, a third configuration had a forward-slotted airfoil with a -10 slat, and a fourth configuration had an aft-slotted airfoil with a 3 deg flap (trailing edge down). The results of this investigation indicate that the -6 deg slat configuration offers some performance and loads benefits over the other three configurations.

Noonan, Kevin W.↗
NASA NTRS1986

Helicopter rotor and engine sizing for preliminary performance estimation

Methods are presented for estimating some of the more fundamental design variables of single-rotor helicopters (tip speed, blade area, disk loading, and installed power) based on design requirements (speed, weight, fuselage drag, and design hover ceiling). The well-known constraints of advancing-blade compressibility and retreating-blade stall are incorporated into the estimation process, based on an empirical interpretation of rotor performance data from large-scale wind-tunnel tests. Engine performance data are presented and correlated with a simple model usable for preliminary design. When approximate results are required quickly, these methods may be more convenient to use and provide more insight than large digital computer programs.

Talbot, P. D.↗
NASA NTRS1989

Laser anemometer measurements in a transonic axial-flow fan rotor

Laser anemometer surveys were made of the 3-D flow field in NASA rotor 67, a low aspect ratio transonic axial-flow fan rotor. The test rotor has a tip relative Mach number of 1.38. The flowfield was surveyed at design speed at near peak efficiency and near stall operating conditions. Data is presented in the form of relative Mach number and relative flow angle distributions on surfaces of revolution at nine spanwise locations evenly spaced from hub to tip. At each spanwise location, data was acquired upstream, within, and downstream of the rotor. Aerodynamic performance measurements and detailed rotor blade and annulus geometry are also presented so that the experimental results can be used as a test case for 3-D turbomachinery flow analysis codes.

Strazisar, Anthony J.↗
NASA NTRS1993

Jet engine performance enhancement through use of a wave-rotor topping cycle

A simple model is used to calculate the thermal efficiency and specific power of simple jet engines and jet engines with a wave-rotor topping cycle. The performance of the wave rotor is based on measurements from a previous experiment. Applied to the case of an aircraft flying at Mach 0.8, the calculations show that an engine with a wave rotor topping cycle may have gains in thermal efficiency of approximately 1 to 2 percent and gains in specific power of approximately 10 to 16 percent over a simple jet engine with the same overall compression ratio. Even greater gains are possible if the wave rotor's performance can be improved.

Wilson, Jack↗