Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Rotation operations”

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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Parametric Time-Dependent Navier-Stokes Computations for a YAV-8B Harrier in Ground Effect

The Harrier Jump Jet has the distinction of being the only powered-lift aircraft in the free world to achieve operational status and to have flown in combat. This V/STOL aircraft can take-off and land vertically or utilize very short runways by directing its four exhaust nozzles towards the ground. Transition to forward flight is achieved by rotating these nozzles into a horizontal position. Powered-lift vehicles have certain advantages over conventional strike fighters. Their V/STOL capabilities allow for safer carrier operations, smaller carrier size, and quick reaction time for troop support. Moreover, they are not dependent on vulnerable land-based runways. The AV-8A Harrier first entered service in the British Royal Air Force (RAF) during 1969, and the U.S. Marine Corps (USMC) in 1971. The AV-8B was a redesign to achieve improved payload capacity, range, and accuracy. This modified design first entered service with the USMC and RAF in 1985. The success and unique capabilities of the Harrier has prompted the design of a powered-lift version of the Joint Strike Fighter (JSF). The flowfield for the Harrier near the ground during low-speed or hover flight operations is very complex and time-dependent. A sketch of this flowfield is shown. Warm air from the fan is exhausted from the front nozzles, while a hot air/fuel mixture from the engine is exhausted from the rear nozzles. These jets strike the ground and move out radially forming a ground jet-flow. The ambient freestream, due to low-speed forward flight or - headwind during hover, opposes the jet-flow. This interaction causes the flow to separate and form a ground vortex. The multiple jets also interact with each other near the ground and form an upwash or jet fountain, which strikes the underside of the fuselage. If the aircraft is sufficiently close to the ground, the inlet can ingest ground debris and hot gases from the fountain and ground vortex. This Hot Gas Ingestion (HGI) can cause a sudden loss of thrust (powered lift), and the vehicle may crash. The high-speed jet flow along the ground can also entrain the ambient flow, resulting in a low pressure region underneath the vehicle. The accompanied loss of lift is referred to as the suckdown effect. The ground vortex may also be highly unsteady, dramatically changing its size and position with time at low frequencies, e.g., 1 Hz.

Chaderjian, Neal M.↗
NASA NTRS1995

Experimental investigation of inlet-combustor isolators for a dual-mode scramjet at a Mach number of 4

This report details experimentally derived operational characteristics of numerous two-dimensional planar inlet-combustor isolator configurations at a Mach number of 4. Variations in geometry included (1) inlet cowl length; (2) inlet cowl rotation angle; (3) isolator length; and (4) utilization of a rearward-facing isolator step. To obtain inlet-isolator maximum pressure-rise data relevant to ramjet-engine combustion operation, configurations were mechanically back pressured. Results demonstrated that the combined inlet-isolator maximum back-pressure capability increases as a function of isolator length and contraction ratio, and that the initiation of unstart is nearly independent of inlet cowl length, inlet cowl contraction ratio, and mass capture. Additionally, data are presented quantifying the initiation of inlet unstarts and the corresponding unstart pressure levels.

Emami, Saied↗
NASA NTRS1989

An improvement of convection fidelity in Euler calculations

A new solution procedure is presented to solve the Euler equations for steady, compressible, rotational, inviscid flows. The approach is aimed at achieving real inviscid solutions in Euler calculations by eliminating numerical diffusion. The variables in the Euler equations are divided into elliptic and convective quantities, using the Clebsch velocity decomposition. The convective quantities are then transported without numerical contamination using an efficient convection operator, while the elliptic quantities are integrated with a relaxation procedure. This approach provides a generalization of the full potential formulation to rotation Euler physics by allowing variations of convective quantities. Results are demonstrated for several transonic flows in two dimensions.

Lee, K. D.↗
NASA NTRS2000

Numerical Simulation of Non-Rotating and Rotating Coolant Channel Flow Fields

Future generations of ultra high bypass-ratio jet engines will require far higher pressure ratios and operating temperatures than those of current engines. For the foreseeable future, engine materials will not be able to withstand the high temperatures without some form of cooling. In particular the turbine blades, which are under high thermal as well as mechanical loads, must be cooled. Cooling of turbine blades is achieved by bleeding air from the compressor stage of the engine through complicated internal passages in the turbine blades (internal cooling, including jet-impingement cooling) and by bleeding small amounts of air into the boundary layer of the external flow through small discrete holes on the surface of the blade (film cooling and transpiration cooling). The cooling must be done using a minimum amount of air or any increases in efficiency gained through higher operating temperature will be lost due to added load on the compressor stage. Turbine cooling schemes have traditionally been based on extensive empirical data bases, quasi-one-dimensional computational fluid dynamics (CFD) analysis, and trial and error. With improved capabilities of CFD, these traditional methods can be augmented by full three-dimensional simulations of the coolant flow to predict in detail the heat transfer and metal temperatures. Several aspects of turbine coolant flows make such application of CFD difficult, thus a highly effective CFD methodology must be used. First, high resolution of the flow field is required to attain the needed accuracy for heat transfer predictions, making highly efficient flow solvers essential for such computations. Second, the geometries of the flow passages are complicated but must be modeled accurately in order to capture all important details of the flow. This makes grid generation and grid quality important issues. Finally, since coolant flows are turbulent and separated the effects of turbulence must be modeled with a low Reynolds number turbulence model to accurately predict details of heat transfer.

Rigby, David L.↗
NASA NTRS1974

NASA plans for space-processing experiments on sounding rockets

Planning for sounding rocket space processing experiments in the second half of 1975 is reported. Currently operational sounding rocket systems are capable of carrying payloads containing more than 50 kg of experimental apparatus on trajectories including between 5 and 10 min of coasting flight above 100 km altitude. When equipped with stabilization systems to nullify angular velocities in their rotational degrees of freedom, these vehicles can provide an environment in which accelerations are less than 1 mm/sec per 2. The cost of flight operations to implement a rocket experiment program will be of the order of 2000 dollars per kg of discretionary payload, and within the next two years newly operational systems are expected to reduce the cost to about 700 dollars per kg.

Bredt, J. H.↗
NASA NTRS2004

Applicability of a Crack-Detection System for Use in Rotor Disk Spin Test Experiments Being Evaluated

Engine makers and aviation safety government institutions continue to have a strong interest in monitoring the health of rotating components in aircraft engines to improve safety and to lower maintenance costs. To prevent catastrophic failure (burst) of the engine, they use nondestructive evaluation (NDE) and major overhauls for periodic inspections to discover any cracks that might have formed. The lowest cost fluorescent penetrant inspection NDE technique can fail to disclose cracks that are tightly closed during rest or that are below the surface. The NDE eddy current system is more effective at detecting both crack types, but it requires careful setup and operation and only a small portion of the disk can be practically inspected. So that sensor systems can sustain normal function in a severe environment, health-monitoring systems require the sensor system to transmit a signal if a crack detected in the component is above a predetermined length (but below the length that would lead to failure) and lastly to act neutrally upon the overall performance of the engine system and not interfere with engine maintenance operations. Therefore, more reliable diagnostic tools and high-level techniques for detecting damage and monitoring the health of rotating components are very essential in maintaining engine safety and reliability and in assessing life.

Abdul-Aziz, Ali↗
NASA NTRS1975

Interior noise levels of two propeller-driven light aircraft

The relationships between aircraft operating conditions and interior noise and the degree to which ground testing can be used in lieu of flight testing for performing interior noise research were studied. The results show that the noise inside light aircraft is strongly influenced by the rotational speed of the engine and propeller. Both the overall noise and low frequency spectra levels were observed to decrease with increasing high speed rpm operations during flight. This phenomenon and its significance is not presently understood. Comparison of spectra obtained in flight with spectra obtained on the ground suggests that identification of frequency components and relative amplitude of propeller and engine noise sources may be evaluated on stationary aircraft.

Catherines, J. J.↗
NASA NTRS1994

Controlling telerobots with video data and compensating for time-delayed video using Omniview

Remote viewing is critical for teleoperations, but the inherent limitations of standard video reduce the operator's effectiveness. These limitations have been compensated for in many ways, from using the operator's adaptability, to augmenting his capability with feedback from a variety of sensors and simulations. Omniview can overcome some of these limitations and improve the operator's efficiency without adding additional sensors or computational burden. It can minimize the potential collisions with facility equipment, provide peripheral vision, and display multiple images simultaneously from a single input device. The Omniview technology provides electronic pan, tilt, magnify, and rotational orientation within a hemispherical field-of-view without any moving parts. Image sizes, viewing directions, scale, offset, etc., may be adjusted to fit operator needs. This paper discusses the derivation of the image transformation, the design of the electronics, and two applications to telepresence that are under development. These are Video Emulated Tweening (VET), and Manipulator Guidance and Positioning (ManGAP). The VET effort uses Omniview to compensate for time-delayed video in teleoperation of remote vehicles. In ManGAP two Omniview systems are used to provide two sets of orientation vectors to points in the field-of-view (FOV). These vectors then provide absolute position information to both control the position of the telerobot, and to avoid collisions with the work sight equipment.

Kuban, Dan↗
NASA NTRS2004

Nickel-Hydrogen and Lithium Ion Space Batteries

The tasks of the Electrochemistry Branch of NASA Glenn Research Center are to improve and develop high energy density and rechargeable, life-long batteries. It is with these batteries that people across the globe are able to power their cell phones, laptop computers, and cameras. Here, at NASA Glenn Research Center, the engineers and scientists of the Electrochemistry branch are leading the way in the development of more powerful, long life batteries that can be used to power space shuttles and satellites. As of now, the cutting edge research and development is being done on nickel-hydrogen batteries and lithium ion batteries. Presently, nickel-hydrogen batteries are common types of batteries that are used to power satellites, space stations, and space shuttles, while lithium batteries are mainly used to power smaller appliances such as portable computers and phones. However, the Electrochemistry Branch at NASA Glenn Research Center is focusing more on the development of lithium ion batteries for deep space use. Because of the limitless possibilities, lithium ion batteries can revolutionize the space industry for the better. When compared to nickel-hydrogen batteries, lithium ion batteries possess more advantages than its counterpart. Lithium ion batteries are much smaller than nickel-hydrogen batteries and also put out more power. They are more energy efficient and operate with much more power at a reduced weight than its counterpart. Lithium ion cells are also cheaper to make, possess flexibility that allow for different design modifications. With those statistics in hand, the Electrochemistry Branch of NASA Glenn has decided to shut down its Nickel-Hydrogen testing for lithium ion battery development. Also, the blackout in the summer of 2003 eliminated vital test data, which played a part in shutting down the program. from the nickel-hydrogen batteries and compare it to past data. My other responsibilities include superheating the electrolyte that is used in the nickel-hydrogen cell in a calorimeter to test its performance under various conditions. 1 used a program called Arbin to study my data. The Arbin allows me to look at different parameters such as pressure and time and how they affect the changing temperature of the electrolyte that is being tested. In addition, I had the responsibility of taking apart and modifying battery coolers that would be used. My mentors told me that the batteries kept shutting down, so it was my responsibility to remove excess fan grilles, rotate the fans, and then switch the aluminum standoffs with nylon ones so that the coolers could operate without problems. My last task is to collect all the battery test data and organize them into charts using Microsoft Excel, before the Branch is able to conduct its research on lithium ion batteries. Therefore, during my tenure, it is my responsibility to take down final test data

Reid, Robert O., II↗
NASA NTRS2005

Multistage Magnetic Separator of Cells and Proteins

The multistage electromagnetic separator for purifying cells and magnetic particles (MAGSEP) is a laboratory apparatus for separating and/or purifying particles (especially biological cells) on the basis of their magnetic susceptibility and magnetophoretic mobility. Whereas a typical prior apparatus based on similar principles offers only a single stage of separation, the MAGSEP, as its full name indicates, offers multiple stages of separation; this makes it possible to refine a sample population of particles to a higher level of purity or to categorize multiple portions of the sample on the basis of magnetic susceptibility and/or magnetophoretic mobility. The MAGSEP includes a processing unit and an electronic unit coupled to a personal computer. The processing unit includes upper and lower plates, a plate-rotation system, an electromagnet, an electromagnet-translation system, and a capture-magnet assembly. The plates are bolted together through a roller bearing that allows the plates to rotate with respect to each other. An interface between the plates acts as a seal for separating fluids. A lower cuvette can be aligned with as many as 15 upper cuvette stations for fraction collection during processing. A two-phase stepping motor drives the rotation system, causing the upper plate to rotate for the collection of each fraction of the sample material. The electromagnet generates a magnetic field across the lower cuvette, while the translation system translates the electromagnet upward along the lower cuvette. The current supplied to the electromagnet, and thus the magnetic flux density at the pole face of the electromagnet, can be set at a programmed value between 0 and 1,400 gauss (0.14 T). The rate of translation can be programmed between 5 and 2,000 m/s so as to align all sample particles in the same position in the cuvette. The capture magnet can be a permanent magnet. It is mounted on an arm connected to a stepping motor. The stepping motor rotates the arm to position the capture magnet above the upper cuvette into which a fraction of the sample is collected. The electronic unit includes a power switch, power-supply circuitry that accepts 110-Vac input power, an RS-232 interface, and status lights. The personal computer runs the MAGSEP software and controls the operation of the MAGSEP through the RS-232 interface. The status of the power, the translating electromagnet, the capture magnet, and the rotation of the upper plate are indicated in a graphical user interface on the computer screen.

Barton, Ken↗
NASA NTRS1983

Scaled centrifugal compressor, collector and running gear program

The Scaled Centrifugal Compressor, Collector and Running gear Program was conducted in support of an overall NASA strategy to improve small-compressor performance, durability, and reliability while reducing initial and life-cycle costs. Accordingly, Garrett designed and provided a test rig, gearbox coupling, and facility collector for a new NASA facility, and provided a scaled model of an existing, high-performance impeller for evaluation scaling effects on aerodynamic performance and for obtaining other performance data. Test-rig shafting was designed to operate smoothly throughout a speed range up to 60,000 rpm. Pressurized components were designed to operate at pressures up to 300 psia and at temperatures to 1000 F. Nonrotating components were designed to provide a margin-of-safety of 0.05 or greater; rotating components, for a margin-of-safety based on allowable yield and ultimate strengths. Design activities were supported by complete design analysis, and the finished hardware was subjected to check-runs to confirm proper operation. The test rig will support a wide range of compressor tests and evaluations.

Kenehan, J. G.↗
NASA NTRS2014

Computational Aerodynamic Simulations of a 1484 ft/sec Tip Speed Quiet High-Speed Fan System Model for Acoustic Methods Assessment and Development

Computational Aerodynamic simulations of a 1484 ft/sec tip speed quiet high-speed fan system were performed at five different operating points on the fan operating line, in order to provide detailed internal flow field information for use with fan acoustic prediction methods presently being developed, assessed and validated. The fan system is a sub-scale, low-noise research fan/nacelle model that has undergone experimental testing in the 9- by 15-foot Low Speed Wind Tunnel at the NASA Glenn Research Center. Details of the fan geometry, the computational fluid dynamics methods, the computational grids, and various computational parameters relevant to the numerical simulations are discussed. Flow field results for three of the five operating points simulated are presented in order to provide a representative look at the computed solutions. Each of the five fan aerodynamic simulations involved the entire fan system, which includes a core duct and a bypass duct that merge upstream of the fan system nozzle. As a result, only fan rotational speed and the system bypass ratio, set by means of a translating nozzle plug, were adjusted in order to set the fan operating point, leading to operating points that lie on a fan operating line and making mass flow rate a fully dependent parameter. The resulting mass flow rates are in good agreement with measurement values. Computed blade row flow fields at all fan operating points are, in general, aerodynamically healthy. Rotor blade and fan exit guide vane flow characteristics are good, including incidence and deviation angles, chordwise static pressure distributions, blade surface boundary layers, secondary flow structures, and blade wakes. Examination of the computed flow fields reveals no excessive or critical boundary layer separations or related secondary-flow problems, with the exception of the hub boundary layer at the core duct entrance. At that location a significant flow separation is present. The region of local flow recirculation extends through a mixing plane, however, which for the particular mixing-plane model used is now known to exaggerate the recirculation. In any case, the flow separation has relatively little impact on the computed rotor and FEGV flow fields.

Tweedt, Daniel L.↗
NASA NTRS2005

Advanced Three-Dimensional Display System

A desktop-scale, computer-controlled display system, initially developed for NASA and now known as the VolumeViewer(TradeMark), generates three-dimensional (3D) images of 3D objects in a display volume. This system differs fundamentally from stereoscopic and holographic display systems: The images generated by this system are truly 3D in that they can be viewed from almost any angle, without the aid of special eyeglasses. It is possible to walk around the system while gazing at its display volume to see a displayed object from a changing perspective, and multiple observers standing at different positions around the display can view the object simultaneously from their individual perspectives, as though the displayed object were a real 3D object. At the time of writing this article, only partial information on the design and principle of operation of the system was available. It is known that the system includes a high-speed, silicon-backplane, ferroelectric-liquid-crystal spatial light modulator (SLM), multiple high-power lasers for projecting images in multiple colors, a rotating helix that serves as a moving screen for displaying voxels [volume cells or volume elements, in analogy to pixels (picture cells or picture elements) in two-dimensional (2D) images], and a host computer. The rotating helix and its motor drive are the only moving parts. Under control by the host computer, a stream of 2D image patterns is generated on the SLM and projected through optics onto the surface of the rotating helix. The system utilizes a parallel pixel/voxel-addressing scheme: All the pixels of the 2D pattern on the SLM are addressed simultaneously by laser beams. This parallel addressing scheme overcomes the difficulty of achieving both high resolution and a high frame rate in a raster scanning or serial addressing scheme. It has been reported that the structure of the system is simple and easy to build, that the optical design and alignment are not difficult, and that the system can be built by use of commercial off-the-shelf products. A prototype of the system displays an image of 1,024 by 768 by 170 (=133,693,440) voxels. In future designs, the resolution could be increased. The maximum number of voxels that can be generated depends upon the spatial resolution of SLM and the speed of rotation of the helix. For example, one could use an available SLM that has 1,024 by 1,024 pixels. Incidentally, this SLM is capable of operation at a switching speed of 300,000 frames per second. Implementation of full-color displays in future versions of the system would be straightforward: One could use three SLMs for red, green, and blue, respectively, and the colors of the voxels could be automatically controlled. An optically simpler alternative would be to use a single red/green/ blue light projector and synchronize the projection of each color with the generation of patterns for that color on a single SLM.

Geng, Jason↗
NASA NTRS1999

Improving Scientific Capabilities in Space in the 21st Century: The NASA New Millennium Program

NASA's New Millennium Program (NMP) has been chartered to identify and validate in space emerging, revolutionary technologies that will enable less costly, more capable future science missions. The program utilizes a unique blend of science guidance and industry partnering to ferret out technology solutions to enable science capabilities in space which are presently technically infeasible, or unaffordable. Those technologies which present an unacceptably high risk to future science missions (whether small PI-led or operational) are bundled into technology validation missions. These missions seek to validate the technologies in a manner consistent with their future uses, thus reducing the associated risk to the first user, and obtaining meaningful science data as well. The Space Readiness Coherent Lidar Experiment (SPARCLE) was approved as the second NMP Earth Observing mission (EO2) in October 1997, and assigned to Marshall Space Flight Center for implementation. Leading up to mission confirmation, NMP sponsored a community workshop in March 1996 to draft Level-1 requirements for a doppler wind lidar mission, as well as other space-based lidar missions (such as DIAL). Subsequently, a study group was formed and met twice to make recommendations on how to perform a comparison of coherent and direct detection wind lidars in space. These recommendations have guided the science validation plan for the SPARCLE mission, and will ensure that future users will be able to confidently assess the risk profile of future doppler wind missions utilizing EO2 technologies. The primary risks to be retired are: (1) Maintenance of optical alignments through launch and operations on orbit, and (2) Successful velocity estimation compensation for the Doppler shift due to the platform motion, and due to the earth's rotation. This includes the need to account for all sources of error associated with pointing control and knowledge. The validation objectives are: (1) Demonstrate measurement of tropospheric winds from space using a scanning coherent Doppler lidar technique that scales to meet future research (e.g. ESSP) and operational (e.g. NPOESS) mission requirements. Specifically, produce and validate LOS wind data with single shot accuracy of 1-2 m/s in regions of high signal-to-noise ratio (SNR), and low atmospheric wind turbulence and wind shear, (2) Collect the atmospheric and instrument performance data in various scanning modes necessary to validate and improve instrument performance models that will enable the definition of future missions with greater confidence. Such data include aerosol backscatter data over much of the globe, and high SNR data such as that from surface returns, and (3) Produce a set of raw instrument data with which advanced signal processing techniques can be developed. This objective will permit future missions to better understand how to extract wind information from low backscatter regions of the atmosphere.

Raymond, Carol A.↗
NASA NTRS1994

Use of magnetic compression to support turbine engine rotors

Ever since the advent of gas turbine engines, their rotating disks have been designed with sufficient size and weight to withstand the centrifugal forces generated when the engine is operating. Unfortunately, this requirement has always been a life and performance limiting feature of gas turbine engines and, as manufacturers strive to meet operator demands for more performance without increasing weight, the need for innovative technology has become more important. This has prompted engineers to consider a fundamental and radical breakaway from the traditional design of turbine and compressor disks which have been in use since the first jet engine was flown 50 years ago. Magnetic compression aims to counteract, by direct opposition rather than restraint, the centrifugal forces generated within the engine. A magnetic coupling is created between a rotating disk and a stationary superconducting coil to create a massive inwardly-directed magnetic force. With the centrifugal forces opposed by an equal and opposite magnetic force, the large heavy disks could be dispensed with and replaced with a torque tube to hold the blades. The proof of this concept has been demonstrated and the thermal management of such a system studied in detail; this aspect, especially in the hot end of a gas turbine engine, remains a stiff but not impossible challenge. The potential payoffs in both military and commercial aviation and in the power generation industry are sufficient to warrant further serious studies for its application and optimization.

Pomfret, Chris J.↗
NASA NTRS1990

Monitoring techniques for the X-29A aircraft's high-speed rotating power takeoff shaft

The experimental X-29A forward swept-wing aircraft has many unique and critical systems that require constant monitoring during ground or flight operation. One such system is the power takeoff shaft, which is the mechanical link between the engine and the aircraft-mounted accessory drive. The X-29A power takeoff shaft opertes in a range between 0 and 16,810 rpm, is longer than most jet engine power takeoff shafts, and is made of graphite epoxy material. Since the X-29A aircraft operates on a single engine, failure of the shaft during flight could lead to loss of the aircraft. The monitoring techniques and test methods used during power takeoff shaft ground and flight operations are discussed. Test data are presented in two case studies where monitoring and testing of the shaft dynamics proved instrumental in discovering and isolating X-29A power takeoff shaft problems. The first study concerns the installation of an unbalanced shaft. The effect of the unbalance on the shaft vibration data and the procedure used to correct the problem are discussed. The second study deals with the shaft exceeding the established vibration limits during flight. This case study found that the vibration of connected rotating machinery unbalances contributed to the excessive vibration level of the shaft. The procedures used to identify the contributions of other rotating machinery unbalances to the power takeoff shaft unbalance are discussed.

Voracek, David F.↗
NASA NTRS1992

A high-efficiency acoustic chamber and the anomalous sample rotation

A high efficiency acoustic chamber for the levitation and manipulation of liquid or molten samples in a microgravity environment has been developed. The chamber uses two acoustic drivers that are mounted at opposite corners of the chamber; by driving these at the same frequency, with 18-deg phase shifts, an increase in force of a factor of 3-4 is obtainable relative to the force of a single-driver system that is operated at the same power level. This enhancement is due to the increased coupling between the sound driver and the chamber. An anomalous rotation is noted to be associated with the chamber; this is found to be eliminated by a physically as-yet inexplicable empirical solution.

Wang, Taylor G.↗