Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “SHROUD”

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 NTRS1983

Accretion onto magnetized neutron stars - X-ray pulsars with intermediate rotation rates

Assuming that the accreting material originates in a wind or envelope and therefore carried no net angular momentum, the Kevin-Helmholtz instability is applied to the transport of accreting plasma across the magnetopause of a rotating and magnetized neutron star for the case in which this surface is interchange-stable. Magnetopause location is determined, and the blackbody emission temperature is estimated. A possible period-dependence is noted in the X-ray temperature data which is in approximate agreement with the present model calculations. The magnetopause is found to be insufficiently stable to support an optically thick sheath of plasma surrounding the source, so that neither shrouding of the X-ray source nor significant reprocessing of the radiation field is possible in the model presented. It is concluded that while the flow structure at the magnetopause can control accretion column geometry, the emerging pulse profile and spectra are only indirectly altered, through a dynamical influence on emission region geometry.

Burnard, D. J.↗
NASA NTRS1983

Booster and orbiter configurations

In the recent Future Space Transportation System (FSFS) study, a mission model was selected and a baseline vehicle which best met model requirements was shaped. This baseline was then analyzed for flight performance, structural and subsystem weight, and operation. Figures related to a payload of 150,000 lb in a 20-ft-diam by 90-ft-long envelope became the baseline. The existence of both space-based orbital transfer vehicles (OTVs) and a space station was assumed, taking into account a transfer of the payload from the launch vehicle to OTVs at the space station for final delivery to geosynchronous orbit (GEO). A computer-aided engineering system called Aerospace Vehicle Interactive Design (AVID) was employed in connection with baseline vehicle development. It was found that approximately three-fifth of the payload weight would be cryogenic propellants for OTVs. Attention is given to problems regarding the packaging of cryogenic tankage, a payload shroud, and studies of staging for two different booster propulsion units.

Wilhite, A. W.↗
NASA NTRS1983

The aerodynamic design and performance of the General Electric/NASA EEE fan

The aerodynamic design and test results of the fan and quarter-stage component for the GE/NASA Energy Efficient Engine (EEE) are presented. The fan is a high bypass ratio, single-stage design having 32 part-span shrouded rotor blades, coupled with a unique quarter-stage arrangement that provides additional core-stream pressure ratio and particle separation. The fan produces a bypass pressure ratio of 1.65 at the exit of the low aspect ratio vane/frame and a core-stream pressure ratio of 1.67 at the entrance to the core frame struts. The full-scale fan vehicle was instrumented, assembled and tested as a component in November 1981. Performance mapping was conducted over a range of speeds and bypass ratios using individually-controlled bypass and core-stream discharge valves. The fan bypass and core-stream test data showed excellent results, with the fan exceeding all performance goals at the important engine operating conditions.

Sullivan, T. J.↗
NASA NTRS1982

Grid generation by elliptic partial differential equations for a tri-element Augmentor-Wing airfoil

Two efforts to numerically simulate the flow about the Augmentor-Wing airfoil in the cruise configuration using the GRAPE elliptic partial differential equation grid generator algorithm are discussed. The Augmentor-Wing consists of a main airfoil with a slotted trailing edge for blowing and two smaller airfoils shrouding the blowing jet. The airfoil and the algorithm are described, and the application of GRAPE to an unsteady viscous flow simulation and a transonic full-potential approach is considered. The procedure involves dividing a complicated flow region into an arbitrary number of zones and ensuring continuity of grid lines, their slopes, and their point distributions across the zonal boundaries. The method for distributing the body-surface grid points is discussed.

Sorenson, R. L.↗
NASA NTRS1983

Metal honeycomb to porous wireform substrate diffusion bond evaluation

Two nondestructive techniques were used to evaluate diffusion bond quality between a metal fail honeycomb and porous wireform substrate. The two techniques, cryographics and acousto-ultrasonics, are complementary in revealing variations of bond integrity and quality in shroud segments from an experimental aircraft turbine engine. Previously announced in STAR as N82-18612

Vary, A.↗
NASA NTRS1983

Recent work on bipolar nebulae

The results of recent studies of bipolar nebulae (BPN) using nebular-polarization mapping, spectropolarimetry, near-IR spectroscopy, far-IR photometry, and radio-maser and continuum observations are surveyed. The characteristics of several BPN of different evolutionary types are discussed and illustrated with spectra, model drawings, and maps. As shown in a Hertzsprung-Russell diagram of 19 BPN, this morphological class includes pre-main-sequence stars, red giants in transition to ordinary planetary nebulae, pre-white-dwarfs, a dust-shrouded carbon star, and a visual binary with a type-O primary. VLA 6-cm observations of the latter object, MWC 349, reveal a morphology similar to the optical structure of the Red Rectangle illuminated by HD 44179: it is suggested that equatorial dusty tori may occur commonly at different phases of stellar evolution, and hence that BPN may be relatively abundant, although short-lived, phenomena.

Cohen, M.↗
NASA NTRS1985

Ellipsoidal Balloon Antenna

Direct-broadcast ellipsoidal antenna 40 percent smaller than spherical reflector. Balloon antenna has feedpoint on surface of ellipsoid outside balloon, simplifying balloon deployment and feed support. Dielectric shrouds used locally to adjust shape of balloon and maintain feed distance at its optimum value.

Cramer, P. W.↗
NASA NTRS1984

Ceramic composite liner material for gas turbine combustors

Advanced commercial and military gas turbine engines may operate at combustor outlet temperatures in excess of 1920 K (3000 F). At these temperatures combustors liners experience extreme convective and radiative heat fluxes. The ability of a plasma sprayed ceramic coating to reduce liner metal temperature has been recognized. However, the brittleness of the ceramic layer and the difference in thermal expansion with the metal substrate has caused cracking, spalling and some separation of the ceramic coating. Research directed at turbine tip seals (or shrouds) has shown the advantage of applying the ceramic to a compliant metal pad. This paper discusses recent studies of applying ceramics to combustor liners in which yttria stabilized zirconia plasma sprayed on compliant metal substrates which were exposed to near stoichiometric combustion, presents performance and durability results, and describes a conceptual design for an advanced, small gas turbine combustor. Test specimens were convectively cooled or convective-transpiration cooled and were evaluated in a 10 cm square flame tube combustor at inlet air temperatures of 533 K (500 F) and at a pressure of 0.5 MPa (75 psia). The ceramics were exposed to flame temperatures in excess of 2000 K (3320 F). Results appear very promising with all 30 specimens surviving a screening test and one of two specimens surviving a cyclic durability test.

Ercegovic, D. B.↗
NASA NTRS1982

NASTRAN flutter analysis of advanced turbopropellers

An existing capability developed to conduct modal flutter analysis of tuned bladed-shrouded discs in NASTRAN was modified and applied to investigate the subsonic unstalled flutter characteristics of advanced turbopropellers. The modifications pertain to the inclusion of oscillatory modal aerodynamic loads of blades with large (backward and forward) variable sweep. The two dimensional subsonic cascade unsteady aerodynamic theory was applied in a strip theory manner with appropriate modifications for the sweep effects. Each strip is associated with a chord selected normal to any spanwise reference curve such as the blade leading edge. The stability of three operating conditions of a 10-bladed propeller is analyzed. Each of these operating conditions is iterated once to determine the flutter boundary. A 5-bladed propeller is also analyzed at one operating condition to investigate stability. Analytical results obtained are in very good agreement with those from wind tunnel tests.

Elchuri, V.↗
NASA NTRS1982

NASTRAN documentation for flutter analysis of advanced turbopropellers

An existing capability developed to conduct modal flutter analysis of tuned bladed-shrouded discs was modified to facilitate investigation of the subsonic unstalled flutter characteristics of advanced turbopropellers. The modifications pertain to the inclusion of oscillatory modal aerodynamic loads of blades with large (backward and forward) varying sweep.

Elchuri, V.↗
NASA NTRS1983

Spaceborne SAR and sea ice

A number of remote sensing systems deployed in satellites to view the Earth which are successful in gathering data on the behavior of the world's snow and ice covers are described. Considering sea ice which covers over 10% of the world ocean, systems that have proven capable to collect useful data include those operating in the visible, near-infrared, infrared, and microwave frequency ranges. The microwave systems have the essential advantage in observing the ice under all weather and lighting conditions. Without this capability data are lost during the long polar night and during times of storm passage, periods when ice activity can be intense. The margins of the ice pack, a region of particular interest, is shrouded in cloud between 80 and 90% of the time.

Weeks, W. F.↗
NASA NTRS1984

Investigation of flow phenomena in a transonic fan rotor using laser anemometry

Several flow phenomena including flowfield periodicity, rotor shock oscillation, and rotor shock system geometry were investigated in a transonic low aspect ratio fan rotor using laser anemometry. Flow periodicity is found to increase with increasing rotor pressure rise, and to correlate with blade geometry variations. Analysis of time-accurate laser anemometer data indicates that the rotor shock oscillates about its mean location with an amplitude of 3 to 4 percent of rotor chord. The shock surface is nearly two-dimensional or levels of rotor pressure rise at and above the peak efficiency level but becomes more complex for lower levels of pressure rise. Spanwise shock lean generates radial flows due to streamline deflection in the hub-to-shroud streamsurface.

Strazisar, A. J.↗
NASA NTRS1984

Rotordynamic Characteristics of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

Rotational stability of turbopump components in the space shuttle main engine was studied via analysis of component and structural dynamic models. Subsynchronous vibration caused unacceptable migration of the rotor/housing unit with unequal load sharing of the synchronous bearings that resulted in the failure of the High Pressure Oxygen Turbopump. Linear analysis shows that a shrouded inducer eliminates the second critical speed and the stability problem, a stiffened rotor improves the rotordynamic characteristics of the turbopump, and installing damper boost/impeller seals reduces bearing loads. Nonlinear analysis shows that by increasing the "dead band' clearances, a marked reduction in peak bearing loads occurs.

Childs, D. W.↗
NASA NTRS1984

Variable stator radial turbine

A radial turbine stage with a variable area nozzle was investigated. A high work capacity turbine design with a known high performance base was modified to accept a fixed vane stagger angle moveable sidewall nozzle. The nozzle area was varied by moving the forward and rearward sidewalls. Diffusing and accelerating rotor inlet ramps were evaluated in combinations with hub and shroud rotor exit rings. Performance of contoured sidewalls and the location of the sidewall split line with respect to the rotor inlet was compared to the baseline. Performance and rotor exit survey data are presented for 31 different geometries. Detail survey data at the nozzle exit are given in contour plot format for five configurations. A data base is provided for a variable geometry concept that is a viable alternative to the more common pivoted vane variable geometry radial turbine.

Rogo, C.↗
NASA NTRS1983

NASTRAN forced vibration analysis of rotating cyclic structures

Theoretical aspects of a new capability developed and implemented in NASTRAN level 17.7 to analyze forced vibration of a cyclic structure rotating about its axis of symmetry are presented. Fans, propellers, and bladed shrouded discs of turbomachines are some examples of such structures. The capability includes the effects of Coriolis and centripetal accelerations on the rotating structure which can be loaded with: (1) directly applied loads moving with the structure and (2) inertial loas due to the translational acceleration of the axis of rotation (''base' acceleration). Steady-state sinusoidal or general periodic loads are specified to represent: (1) the physical loads on various segments of the complete structure, or (2) the circumferential harmonic components of the loads in (1). The cyclic symmetry feature of the rotating structure is used in deriving and solving the equations of forced motion. Consequently, only one of the cyclic sectors is modelled and analyzed using finite elements, yielding substantial savings in the analysis cost. Results, however, are obtained for the entire structure. A tuned twelve bladed disc example is used to demonstrate the various features of the capability.

Elchuri, V.↗
NASA NTRS1984

Main characteristics of the Large Space Simulation (LSS)

The European Space Agency (ESA) has started the implementation of a Large Space Simulator at its European Space Research and Technology Centre (ESTEC) located at Noordwijk, The Netherlands. After its completion in early 1986 this facility will enable mechanical and thermal tests on large satellites. The chamber will be equipped with a collimated solar beam of 6 Meter diameter. In addition Infrared equipment is available as alternative or complementary source of thermal radiation. Also controlled variation of shroud temperatures can be utilised for thermal testing or temperature cycling of hardware. The "Design and Definition Phase" of the project has been successfully completed by the end of 1983. The paper presents the basic concept and major design aspects of this facility. At the time of the conference, the large chamber is already under construction on site.

Peter W. Brinkmann↗
NASA NTRS1983

Fused silica mirror evaluation for the Shuttle Infrared Telescope Facility (SIRTF)

The SIRTF optics are intended for operation at 20 K (or less); it will be extremely inconvenient, expensive, and time consuming if it becomes necessary to accomplish all of the optical element testing, assembly, and alignment at comparable temperatures. The thermal strain behavior, including potential anisotropies and inhomogeneities, of a mirror substrate between room temperature and 20 K thus becomes a major factor in the selection of the substrate material, structural configuration, and joining methods for lightweight structures. With support from Space Projects, NASA Ames Research Center, an optical figure evaluation of a 0.65-meter, lightweight, fused silica mirror at a low-temperature goal of 20 K is being conducted. The design details of a thermal shroud, provisions for extracting heat from the low-conductivity mirror, and wavefront error sources other than the mirror surface are discussed and preliminary test results presented.

Barnes, W. P., Jr.↗
NASA NTRS1984

The interaction between mistuning and friction in the forced response of bladed disk assemblies

This paper summarizes the results of an investigation to establish the impact of mistuning on the performance and design of blade-to-blade friction dampers of the type used to control the resonant response of turbine blades in gas turbine engines. In addition, it discusses the importance of friction slip force variations on the dynamic response of shrouded fan blades.

Griffin, J. H.↗