Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “radiality”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Cooled variable nozzle radial turbine for rotor craft applications

An advanced, small 2.27 kb/sec (5 lbs/sec), high temperature, variable area radial turbine was studied for a rotor craft application. Variable capacity cycles including single-shaft and free-turbine engine configurations were analyzed to define an optimum engine design configuration. Parametric optimizations were made on cooled and uncooled rotor configurations. A detailed structural and heat transfer analysis was conducted to provide a 4000-hour life HP turbine with material properties of the 1988 time frame. A pivoted vane and a moveable sidewall geometry were analyzed. Cooling and variable geometry penalties were included in the cycle analysis. A variable geometry free-turbine engine configuration with a design 1477K (2200 F) inlet temperature and a compressor pressure ratio of 16:1 was selected. An uncooled HP radial turbine rotor with a moveable sidewall nozzle showed the highest performance potential for a time weighted duty cycle.

Rogo, C.↗
NASA NTRS1981

A study of the long-term variation and radial gradient of cosmic rays out to 23 AU

It is shown by an examination of Pioneer, Voyager and IMP spacecraft cosmic ray long-term modulation data, for the case of E greater than 60 MeV in the period 1972-1980, that (1) long-term modulation effects are propagated outward radially from the sun with a typical speed of 350-500 km/sec; (2) the average integral radial gradient over the period, between 2 and 23 AU, is 2.85 + or - 0.5% AU, and (3) the boundary of the heliocentric modulation region in the ecliptic plane, as derived from simple conventional modulation theory, is greater than 65 AU. It is concluded that the weak dependence of the average gradient upon cosmic ray intensity may be used to estimate the location of the boundary in a standard modulation model.

Webber, W. R.↗
NASA NTRS1982

Radial widths, optical depths, and eccentricities of the Uranian rings

Observations of the stellar occultation by the Uranian rings of 15/16 August 1980 are used to estimate radial widths and normal optical depths for segments of rings 6, 5, 4, alpha, beta, eta, gamma, and delta. Synthetic occultation profiles are generated to match the observed light curves. A review of published data confirms the existence of width-radius relations for rings alpha and beta, and indicates that the optical depths of these two rings vary inversely with their radial widths. Masses are obtained for rings alpha and beta, on the assumption that differential precession is prevented by their self-gravity. A quantitative comparison of seven epsilon-ring occultation profiles obtained over a period of 3.4 yr reveals a consistent structure, which may reflect the presence of unresolved gaps and subrings.

Nicholson, P. D.↗
NASA NTRS1982

Non-radial flow near the cometary surface

It is shown that, as a consequence of the non-uniform temperature distribution of the cometary nucleus, large lateral pressure gradients are set up, which in turn drive strong lateral flows. However, at small heliocentric distances the onset of turbulence within a thin boundary layer destroys these steady lateral flows and the eventual outflow of gas from within the outer boundary of this layer is expected to be more or less radial. On the other hand, at large heliocentric distances, turbulence is unlikely to set in, and the lateral flows that are set up, may persist. Consequently, it is expected that the gas flow out of the cometary nucleus at these large distances to be highly non-radial.

Marconi, M. L.↗
NASA NTRS1982

Radially uniform electron source

A thermionic electron source capable of producing uniform count rates in a number of channel electron multipliers simultaneously was required for conditioning multipliers for an extended space mission. It was found that a straight tungsten filament in the center of a cylindrically symmetric geometry surrounded by an array of multipliers emits a radially asymmetric distribution of electrons that changes with time. A source was developed which successfully produces a time-independent radially uniform distribution of electrons by moving the filament out of the direct line of sight and replacing it with a centrally located electron 'cloud.'

Mccomas, D.↗
NASA NTRS1983

Calculating the Flow Field in a Radial Turbine Scroll

Set of two computer programs calculates flow field in radial turbine scroll. Programs represent improvement in analyzing flow in radial turbine scrolls and provide designer with tools for designing better scrolls. Programs written in FORTRAN IV.

Baskharone, E.↗
NASA NTRS1984

Radial-Cascade Analysis

Conformal mapping transforms radial cascade to axial cascade. Report describes analysis of pressure distributions on radial diffuser geometries within Space Shuttle main and preburner pumps. Analysis uses modified version of Douglas-Neuman (D-N) procedure for two-dimensional axial cascades.

Meng, S. Y.↗
NASA NTRS1984

Radially-Graduated Turbine-Temperature Profile

Proposed scheme to change temperature distribution in gas-turbine flame increases radially instead of remaining spatially uniform offers important advantages. Radially increasing temperature allows higher mean gas temperature, greater power output, higher rotational speed and longer life for blades. Principle suitable for axial-flow gas turbine directly in line with cylindrical combustor. Included in category many rocket, aircraft, stationary, and shipboard turbines.

Wagner, W. R.↗
NASA NTRS1983

Stress intensity and displacement coefficients for radially cracked ring segments subject to three-point bending

The boudary collocation method was used to generate Mode 1 stress intensity and crack mouth displacement coefficients for internally and externally radially cracked ring segments (arc bend specimens) subjected to three point radial loading. Numerical results were obtained for ring segment outer to inner radius ratios (R sub o/ R sub i) ranging from 1.10 to 2.50 and crack length to width ratios (a/W) ranging from 0.1 to 0.8. Stress intensity and crack mouth displacement coefficients were found to depend on the ratios R sub o/R sub i and a/W as well as the included angle between the directions of the reaction forces.

Gross, B.↗
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 NTRS1984

Application of a quasi-3D inviscid flow and boundary layer analysis to the hub-shroud contouring of a radial turbine

Application of a quasi-3D approach to the aerodynamic analysis of several radial turbine configurations is described. The objective was to improve the rotor aerodynamic characteristics by hub-shroud contouring. The approach relies on available 2D inviscid methods coupled with boundary layer analysis to calculate profile, mixing, and endwall losses. Windage, tip clearance, incidence, and secondary flow losses are estimated from correlations. To eliminate separation along the hub and blade suction surfaces of a baseline rotor, the analysis was also applied to three alternate hub-shroud geometries. Emphasis was on elimination an inducer velocity overshoot as well as increasing hub velocities. While separation was never eliminated, the extent of the separated area was progressively reduced. Results are presented in terms of mid-channel and blade surface velocities; kinetic energy loss coefficients; and efficiency. The calculation demonstrates a first step for a systematic approach to radial turbine design that can be used to identify and control aerodynamic characteristics that ultimately determine heat transfer and component life. Experimentation will be required to assess the extent to which flow and boundary layer behavior were predicted correctly.

Civinskas, K. C.↗
NASA NTRS1983

Radial segregation induced by natural convection and melt/solid interface shape in vertical Bridgman growth

The roles of natural convection in the melt and the shape of the melt/solid interface on radial dopant segregation are analyzed for a prototype of vertical Bridgman crystal growth system by finite element methods that solve simultaneously for the velocity field in the melt, the shape of the solidification isotherm, and the temperature distribution in both phases. Results are presented for crystal and melt with thermophysical properties similar to those of gallium-doped germanium in Bridgman configurations with melt below (thermally destabilizing) and above (stabilizing) the crystal. Steady axisymmetric flow are classified according to Rayleigh number as either being nearly the growth velocity, having a weak cellular structure or having large amplitude cellular convention. The flows in the two Bridgman configurations are driven by different temperature gradients and are in opposite directions. Finite element calculations for the transport of a dilute dopant by these flow fields reveal radial segregation levels as large as sixty percent of the mean concentration. Segregation is found most severe at an intermediate value of Rayleigh number above which the dopant distribution along the interface levels as the intensity of the flow increases.

Chang, C. J.↗
NASA NTRS1983

Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. III - Reticon radial velocities

Radial velocities for 72 stars, most of them known or suspected binaries with F - K giant-supergiant primaries, are derived from Reticon spectra in the region 6005-6235 A at a scale of 7 km/s per diode. Cross-correlation of the spectra normally produces results accurate to better than 1.0 km/s. Eight new radial velocity variables are found (HR 2786, R Pup, HR 3291, HR 4451, HD 114520, HR 5667, HR 7014, and Nu1 Sgr). Improved orbits are determined for 15 known spectroscopic binaries, and provisional orbits are obtained for seven new spectroscopic binaries.

Parsons, S. B.↗
NASA NTRS1984

Application of a quasi-3D inviscid flow and boundary layer analysis to the hub-shroud contouring of a radial turbine

Application of a quasi-3D approach to the aerodynamic analysis of several radial turbine configurations is described. The objective was to improve the rotor aerodynamic characteristics by hub-shroud contouring. The approach relies on available 2D inviscid methods coupled with boundary layer analysis to calculate profile, mixing, and endwall losses. Windage, tip clearance, incidence, and secondary flow losses are estimated from correlations. To eliminate separation along the hub and blade suction surfaces of a baseline rotor, the analysis was also applied to three alternate hub-shroud geometries. Emphasis was on elimination of an inducer velocity overshoot as well as increasing hub velocities. While separation was never eliminated, the extent of the separated area was progressively reduced. Results are presented in terms of mid-channel and blade surface velocities; kinetic energy loss coefficients; and efficiency. The calculation demonstrates a first step for a systematic approach to radial turbine design that can be used to identify and control aerodynamic characteristics that ultimately determine heat transfer and component life. Experimentation will be required to assess the extent to which flow and boundary layer behavior were predicted correctly.

Civinskas, K.↗
NASA NTRS1984

Production of plasma with variable, radial electric fields

A device is described suitable for plasma wave experiments requiring relatively large, variable, radial electric fields perpendicular to a static magnetic field. By separately adjusting the potentials of two independent, coaxial discharge plasmas, the authors produced plasmas with a radial electric field E sub r less than approximately 5 V/cm.

Kustom, B.↗
NASA NTRS1986

Off-Design Performance of Radial-Inflow Turbines

Computer code determines rotor exit flow from hub to tip. RTOD (Radial Turbine Off-Design), computes off-design performance of radial turbine by modeling flow with stator viscous and trailing-edge losses, and with vaneless space loss between stator and rotor, and with rotor incidence, viscous, clearance, trailing-edge, and disk friction losses.

Meitner, P. L.↗
NASA NTRS1985

Radial transport of approximately 1 MeV/nucleon ions during the 22 November 1977 solar particle event

Time intensity profiles of solar flare energetic particle events carry information on the particle injection processes at the Sun, as well as the transport of particles in interplanetary space. However, in order to help identify the individual processes of injection versus transport it is necessary to use observations taken at more than one radial location. Results of such a study concerning the 22 November 1977 solar particle event, observed with instruments at 1.0 and 1.55 AU are presented. The observations are for particles of energies near 1 MeV/nucleon, considerably less than the approx. 10 to 20 MeV/nucleon energies typical of previous radial transport studies. Thus, in the present work it is possible to examine the validity of transport models to considerably lower energies than in previous work.

Mason, G. M.↗
NASA NTRS1983

Difference equation technique for determining the evolution of radially symmetric ultrasonic fields

A simplified difference equation technique has been developed to calculate the three-dimensional evolution of radially symmetric, complex ultrasonic fields. The parabolic approximation to the Helmholtz equation is obtained by assuming that localized changes in the magnitude of the field with respect to distance along the axis of propagation are small compared to those with respect to radial displacement. The Helmholtz equation in cylindrical coordinates may then be approximated, after separating variables, using truncated series expansions. The resulting difference equation determines complex field values at discrete locations in a plane using corresponding adjacent locations in the preceding plane. Stability criteria which determine acceptable values for various parameters are discussed. The technique has been applied to the propagation of ultrasonic fields generated by two-dimensional focusing and non-focusing, uniform and Gaussian profile, piezoelectric transducers in both profiled and non-profiled media.

Dockery, G. D.↗