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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Revised FORTRAN program for calculating velocities and streamlines on the hub-shroud midchannel stream surface of an axial-, radial-, or mixed-flow turbomachine or annular duct. 1: User's manual

A FORTRAN 4 computer program was developed that obtains a detailed subsonic or shock-free transonic flow solution on the hub-shroud midchannel stream surface of a turbomachine. The blade row may be fixed or rotating, and the blades may be twisted and leaned. Flow may be axial, mixed, or radial. Upstream and downstream flow variables may vary from hub to shroud, and provision is made to correct for loss of stagnation pressure. The results include velocities, streamlines, and flow angles on the stream surface as well as approximate blade surface velocities. Subsonic solutions are obtained by a finite-difference, stream-function solution. Transonic solutions are obtained by a velocity-gradient method that uses information from a finite-difference, stream-function solution at a reduced mass flow.

Katsanis, T.↗
NASA NTRS1977

Revised FORTRAN program for calculating velocities and streamlines on the hub-shroud midchannel stream surface of an axial-, radial-, or mixed-flow turbomachine or annular duct. 2: Programmer's manual

A FORTRAN IV computer program has been developed that obtains a detailed subsonic or shock free transonic flow solution on the hub-shroud midchannel stream surface of a turbomachine. The blade row may be fixed or rotating, and the blades may be twisted and leaned. Flow may be axial, mixed, or radial. Upstream and downstream flow variables may vary from hub to shroud, and provisions are made to correct for loss of stagnation pressure. The results include velocities, streamlines, and flow angles on the stream surface and approximate blade surface velocities.

Katsanis, T.↗
NASA NTRS1977

Composite hubs for low cost turbine engines

A detailed stress analysis is performed using NASTRAN to demonstrate theoretically the adequacy of composite hubs for low cost turbine engine applications. The results show that composite hubs are adequate for this application from the steady state stress viewpoint.

Chamis, C. C.↗
NASA NTRS1979

Preliminary design study of advanced composite blade and hub and nonmechanical control system for the tilt-rotor aircraft. Volume 1: Engineering studies

Composite structures technology is applied in a preliminary design study of advanced technology blades and hubs for the XV-15 tilt rotor research demonstrator aircraft. Significant improvements in XV-15 hover and cruise performance are available using blades designed for compatibility with the existing aircraft, i.e., blade installation would not require modification of the airframe, hub or upper controls. Provision of a low risk nonmechanical control system was also studied, and a development specification is given.

Alexander, H. R.↗
NASA NTRS1980

Preliminary design study of advanced composite blade and hub and nonmechanical control system for the tilt-rotor aircraft. Volume 2: Project planning data

Project planning data for a rotor and control system procurement and testing program for modifications to the XV-15 tilt-rotor research demonstrator aircraft is presented. The design, fabrication, and installation of advanced composite blades compatible with the existing hub, an advanced composite hub, and a nonmechanical control system are required.

Source record↗
NASA NTRS1984

Space station architecture, module, berthing hub, shell assembly, berthing mechanism and utility connection channel

The geometric form of a space station is presented that includes a description of a plurality of modules and berthing hubs, joined by interconnections which are sideways connectable. The modules and hubs are fastened together in a triangular configuration in three dimensions. The interconnections include a pair of opposed, axially aligned, flanged ports and a clamp latch formed from a plurality of sections hinged along their length and extending circumferentially around the flanged ports. A hermetic seal is formed between the ports. A utilities connection channel extends between the ports. The channel has a shell with utilities connectors movable between an extended position to mating connectors in the modules and a withdrawn position. Assembly sequence and common module shell structure is detailed.

Cohen, M. M.↗
NASA NTRS1984

Extended aeroelastic analysis for helicopter rotors with prescribed hub motion and blade appended penduluum vibration absorbers

The mathematical development for the expanded capabilities of the G400 rotor aeroelastic analysis was examined. The G400PA expanded analysis simulates the dynamics of all conventional rotors, blade pendulum vibration absorbers, and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. The methodology for modeling the unsteady stalled airloads of two dimensional airfoils is discussed. Formulations for calculating the rotor impedance matrix appropriate to the higher harmonic blade excitations are outlined. This impedance matrix, and the associated vibratory hub loads, are the rotor dynamic characteristic elements for use in the simplified coupled rotor/fuselage vibration analysis (SIMVIB). Updates to the development of the original G400 theory, program documentation, user instructions and information are presented.

Bielawa, R. L.↗
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 NTRS1984

Effects of inlet distortion on a static pressure probe mounted on the engine hub in an F-15 airplane

Problems encountered in obtaining good engine face pressure data were studied. A single static measurement located upstream of the engine hub in the stream flow was found to provide a pressure signal suitable for engine control. Two identical probes for measuring fan inlet static (PS2) pressure were designed and mounted on the hub of the left F100-PW-100 turbofan engine installed in the F-15 test aircraft for flight evaluation. The probe is used as a static pressure sensor for a digital engine control system.

Hughes, D. L.↗
NASA NTRS1989

Space station architecture, module, berthing hub, shell assembly, berthing mechanism and utility connection channel

A Space Station includes a plurality of modules, and berthing hubs, joined by interconnections which are sideways connectable. The modules and hubs are fastened together in a trianglar configuration in three dimensions. The interconnections include a pair of opposed, axially aligned, flanged ports, and a clamp latch formed from a plurality of sections hinged along their length and extending circumferentially around the flanged ports. A utilities connection channel extends between ports. The channel has a shell with utilities connectors movable between an extended position to mating connectors in the modules and a withdrawn position. Assembly sequence and common module shell structure is detailed.

Marc M Cohen↗
NASA NTRS1990

Improved Hub Fairings For Helicopters

Wind-tunnel experiments show new generic configuration for fairing for helicopter rotor hub reduces contribution of hub to overall aerodynamic drag. New generic fairing has flat bottom, which eliminates converging/diverging boundary by straightening surfaces facing each other. Reduces interference drag, similarly to reduction of interference drag by flattening of facing surfaces of two side-by-side airfoils.

Stroub, Robert H.↗
NASA NTRS1992

Blade root torsional dampers to reduce hub loads

A new method of reducing helicopter rotor hub loads and marginally improving rotor performance by the introduction of large values of blade root torsional damping is presented. Basic theoretical considerations imply that these benefits in hub loads can come about by changes to the blade elastic torsional deflection. This basic theory was analytically verified by using a fully coupled aeroelastic rotorcraft analysis as applied to a modern, articulated rotor blade, namely that of the Sikorsky S-76. From an implementation standpoint, a rotor-based torsional damping device may be more practical than one that involves a major portion of the blade span. Also, a root-based device may allow for the retrofitting of existing helicopter rotor blade/hub configurations.

Kottapalli, Sesi↗
NASA NTRS1951

Experimental investigation of an 0.8 hub-tip radius-ratio,nontwisted-rotor-blade turbine

An experimental investigation of a 0.8 hub-tip radius ratio, nontwisted-rotor-blade turbine designed for a stagnation-pressure ratio of 2.5 and an equivalent mean blade speed of 643 feet per second was made in a cold-air turbine with (a) nontwisted stator blades, and (b) twisted stator blades designed to maintain zero rotor-inlet incidence angles. Turbine efficiencies of the order of 0.85 at the design point were obtained with a nontwisted-rotor-blade turbine with a hub-tip radius ratio of 0.80. The turbine with the twisted stator blades gave higher efficiencies at the design point (of the order of 1.5 percentage points) than the turbine with the nontwisted stator blades.

TURBINES - AXIAL FLOW↗
NASA NTRS2000

Analysis and Modeling of Ground Operations at Hub Airports

Building simple and accurate models of hub airports can considerably help one understand airport dynamics, and may provide quantitative estimates of operational airport improvements. In this paper, three models are proposed to capture the dynamics of busy hub airport operations. Two simple queuing models are introduced to capture the taxi-out and taxi-in processes. An integer programming model aimed at representing airline decision-making attempts to capture the dynamics of the aircraft turnaround process. These models can be applied for predictive purposes. They may also be used to evaluate control strategies for improving overall airport efficiency.

Atkins, Stephen↗
NASA NTRS2002

Centrifugal Compressor Surge Margin Improved With Diffuser Hub Surface Air Injection

Aerodynamic stability is an important parameter in the design of compressors for aircraft gas turbine engines. Compression system instabilities can cause compressor surge, which may lead to the loss of an aircraft. As a result, engine designers include a margin of safety between the operating line of the engine and the stability limit line of the compressor. The margin of safety is typically referred to as "surge margin." Achieving the highest possible level of surge margin while meeting design point performance objectives is the goal of the compressor designer. However, performance goals often must be compromised in order to achieve adequate levels of surge margin. Techniques to improve surge margin will permit more aggressive compressor designs. Centrifugal compressor surge margin improvement was demonstrated at the NASA Glenn Research Center by injecting air into the vaned diffuser of a 4:1-pressure-ratio centrifugal compressor. Tests were performed using injector nozzles located on the diffuser hub surface of a vane-island diffuser in the vaneless region between the impeller trailing edge and the diffuser-vane leading edge. The nozzle flow path and discharge shape were designed to produce an air stream that remained tangent to the hub surface as it traveled into the diffuser passage. Injector nozzles were located near the leading edge of 23 of the 24 diffuser vanes. One passage did not contain an injector so that instrumentation located in that passage would be preserved. Several orientations of the injected stream relative to the diffuser vane leading edge were tested over a range of injected flow rates. Only steady flow (nonpulsed) air injection was tested. At 100 percent of the design speed, a 15-percent improvement in the baseline surge margin was achieved with a nozzle orientation that produced a jet that was bisected by the diffuser vane leading edge. Other orientations also improved the baseline surge margin. Tests were conducted at speeds below the design speed, and similar results were obtained. In most cases, the greatest improvement in surge margin occurred at fairly low levels of injected flow rate. Externally supplied injection air was used in these experiments. However, the injected flow rates that provided the greatest benefit could be produced using injection air that is recirculating between the diffuser discharge and nozzles located in the diffuser vaneless region. Future experiments will evaluate the effectiveness of recirculating air injection.

Skoch, Gary J.↗
NASA NTRS1988

Space station architecture, module, berthing hub, shell assembly, berthing mechanism and utility connection channel

A space station (20) includes a plurality of modules (24) and berthing hubs (22), joined by interconnections (26) which are sideways connectable. The modules (24) and hubs (22) are fastened together in a triangular configuration in three dimensions. The interconnections (26) include a pair of opposed, axially aligned, flanged ports (50) and a clamp latch (52) formed from a plurality of sections (54, 56 and 58) hinged along their length and extending circumferentially around the flanged ports (50). A hermetic seal (63) is formed between the ports (50). A utilities connection channel (68) extends between the ports (50). The channel (68) has a shell (70) with utilities connectors (74) movable between an extended position to mating connectors in the modules (24) and a withdrawn position. Assembly sequence and common module shell structure is detailed.

Cohen, Marc M.↗
NASA NTRSDate not supplied

Time-Frequency Analysis of Experimental and Analytical Hub Loads of a Rotor Undergoing a Rotor Speed Change

A two-part analytical study was conducted examining a small-scale, two-bladed rotor undergoing a change in rotor speed in a wind tunnel setting. First, a parametric study was conducted to understand how rotor transient response, determined using a time-marching solution, is affected by the choice of rotor wake model, blade elasticity, and inclusion of an elastic support structure model. The second part of the study compared results from an analytical model of the NASA Multirotor Test Bed (MTB) undergoing a rotor speed change to experimental data. Since the analytical and experimental time histories were non-stationary signals, a Stockwell transform was employed to analyze the data in lieu of traditional Fourier transform-based methods. The analysis included extraction of time-varying frequency content of the rotor thrust and hub motion, damping ratios, instantaneous rotor speed, and instantaneous phase difference between thrust and hub motion. Use of a free wake model was found to be necessary to predict higher-harmonic thrust, however, it underpredicted the amplitude of the unsteady loads. Modeling the elasticity of the stiff rotor blades installed on the MTB resulted in minimal impact on the vibratory loads compared to a rigid blade model. The current analytical model of the MTB, including an elastic support structure, properly predicted the measured trends in the frequency content of the thrust.

Rotor dynamics↗
NASA NTRSDate not supplied

Time-Frequency Analysis of Experimental and Analytical Hub Loads of a Rotor Undergoing a Rotor Speed Change

A two-part analytical study was conducted examining a small-scale, two-bladed rotor undergoing a change in rotor speed. First, a parametric study was conducted to understand how rotor transient response, determined using a time-marching solution, is affected by the choice of rotor wake model, blade elasticity, and inclusion of an elastic support structure model. The second part of the study compared results from an analytical model of the NASA Multirotor Test Bed (MTB) undergoing a rotor speed change to wind tunnel data. Since the analytical and experimental time histories were nonstationary signals, a Stockwell transform was employed to analyze the data in lieu of traditional Fourier transform-based methods. The analysis included extraction of time-varying frequency content of the rotor thrust and hub motion, damping ratios, instantaneous rotor speed, and instantaneous phase difference between thrust and hub motion. Use of a free wake model was found to be necessary to predict higher-harmonic thrust, however, it underpredicted the amplitude of the unsteady loads. Modeling the elasticity of the stiff rotor blades installed on the MTB resulted in minimal impact on the computed vibratory loads compared to a rigid blade model. The current analytical model of the MTB, including an elastic support structure, properly predicted the measured trends in the frequency content of the thrust.

Martin K Sekula↗