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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

Adherend surfaces and fractography were studied using electron spectroscopy for chemical analysis and scanning electron microscopy/energy dispersive analysis of X-rays. In addition, Auger Electron Spectroscopy with depth profiling capability was used. It is shown that contamination of adhesion systems plays an important role not only in determining initial bond strengths but also in the durability of adhesive bonds. It is concluded that the analytical techniques used to characterize and monitor such contamination.

Chen, W.↗
NASA NTRS1979

Fundamentals of Gas Turbine combustion

Combustion problems and research recommendations are discussed in the areas of atomization and vaporization, combustion chemistry, combustion dynamics, and combustion modelling. The recommendations considered of highest priority in these areas are presented.

Gerstein, M.↗
NASA NTRS1978

Solar collectors. I - Fundamentals and collectors of the past and present

The paper is a state-of-the-art review aiming to familiarize those who are new in the solar energy field with past accomplishment in solar energy utilization. Consideration is given to the design features and performance definition of solar collectors. The characteristics of planar collectors, line focusing collectors, and point focusing collectors (including the central receiver concept) are briefly discussed.

Selcuk, M. K.↗
NASA NTRS1979

Fundamental mechanisms that influence the estimate of heat transfer to gas turbine blades

Heat tranfer problems in aircraft gas turbines required for improved prediction of turbine blade or vane gas-side heat transfer are examined. Estimates of the heat transfer from the gas to vanes or rotating blades are uncertain due to the complexity of the heat transfer processes, since the gas flow is three dimensional with complex secondary viscous flow patterns that interact with the endwalls and blade surfaces. In addition, upstream disturbances, stagnation flow, curvature effects, and flow acceleration complicate the thermal transport mechanisms in the boundary layers. The thermal state and flow characteristics of the hot gases that enter the turbine blade row, analytical methods for calculating the gas-side heat transfer to turbine blades, and flow phenomena such as stagnation, curvature effects, acceleration, secondary flows, and transition that influences local heat transfer rates are discussed.

Graham, R. W.↗
NASA NTRS1977

The Uncertainty Threshold Principle: Some Fundamental Limitations of Optimal Decision Making Under Dynamic Uncertainity

This note shows that the optimal control of dynamic systems with uncertain parameters has certain limitations. In particular, by means of a simple scalar linear-quadratic optimal control example, it is shown that the infinite horizon solution does not exist if the parameter uncertainty exceeds a certain quantifiable threshold; we call this the uncertainty threshold principle. The philosophical and design implications of this result are discussed.

Athans, M.↗
NASA NTRS1979

Fundamentals of heat measurement

Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

Gerashchenko, O. A.↗
NASA NTRS1979

A fundamental study of liquid spray evaporation at a heated surface

The influence of feedwater temperature and the influence of pulsing nozzle flow on the heat transfer characteristics in the spray evaporative cooling process were investigated. A commercial water circulation heater was installed in the feedwater line between the supply reservoir and the nozzle. A pass through the heater provided water at temperatures up to 50 C at the nozzle; higher temperatures were obtained by multiple heater passes. A thermocouple installed in the water line just upstream of the nozzle provided a measure of the feedwater temperature. Initial tests were run with belljar exhaust orifice number two which provided a pressure in a range about 7mm Hg abs. The feedwater temperature was heated to a temperature of 45 C. Results indicate that for a given system operating pressure, there is an upper limit on the feedwater temperature above which the spray will flash to vapor before hitting the surface to be cooled.

Wierum, F. A.↗
NASA NTRS1979

Applications of Modern Hydrodynamics to Aeronautics. Part 1: Fundamental Concepts and the Most Important Theorems. Part 2: Applications

A discussion of the principles of hydrodynamics of nonviscous fluids in the case of motion of solid bodies in a fluid is presented. Formulae are derived to demonstrate the transition from the fluid surface to a corresponding 'control surface'. The external forces are compounded of the fluid pressures on the control surface and the forces which are exercised on the fluid by any solid bodies which may be inside of the control surfaces. Illustrations of these formulae as applied to the acquisition of transformations from a known simple flow to new types of flow for other boundaries are given. Theoretical and experimental investigations of models of airship bodies are presented.

Prandtl, L.↗
NASA NTRS1980

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

The acid-base properties of titanium 6-4 plates (low surface area) were investigated after three different pretreatments, namely Turco, phosphate-fluoride and Pasa-Jell. A series of indicators was used and color changes were detected using diffuse reflectance visible spectroscopy. Electron spectroscopy for chemical analysis was used to examine the indicator on the Ti 6-4 surface. Specular reflectance infra-red spectroscopy was used to study the adsorption of stearic acid from cyclohexane solutions on the Ti 6-4 surface.

Siriwardane, R.↗
NASA NTRS1980

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

Several techniques were used to study pretreated Ti 6-4 surfaces including scanning electron microscopy (SEM), electron spectroscopy of chemical analysis (ESCA), and, reflectance visible spectroscopy. Each pretreatment type gave a characteristic surface morphology as seen by SEM. Elemental analysis of the Ti 6-4 surfaces was done using ESCA. Trace residual contaminants from particular chemical pretreatments were identified readily. Results indicate that reflectance visible spectroscopy using indicator dyes placed on Ti 6-4 surfaces appears to be a feasible approach to establish surface acidity. Differences in surface acidity were observed using bromthymol blue on Ti 6-4 surfaces pretreated by two different methods.

Beck, B.↗
NASA NTRS1980

Fundamentals studies in geodynamics

Research in geodynamics, seismology, and planetary quakes is presented. Terradynamics and plate tectonics are described using dynamic models. The early evolution of the Earth's mantle is also discussed.

Anderson, D. L.↗
NASA NTRS1980

Fundamental studies in geodynamics

Progress in modeling instantaneous plate kinematics is reviewed, with emphasis on recently developed models of present day plate motions derived by the systematic inversion of globally distributed data sets. Rivera plate motions, the Caribbean South American boundary, Indian plate deformation, Pacific-North America, seismicity and subduction processes, and the study of slow earthquakes and free oscillations are discussed.

Anderson, D. L.↗
NASA NTRS1980

Life from a plantary perspective: Fundamental issues in global ecology

Twenty-three scientists from diverse disciplines met for one week at the University of California, Santa Barbara to discuss life from a planetary perspective. The scientists represented the major disciplines concerned with the Earth's biota, oceans, atmosphere and sediments, including geochemistry, atmospheric chemistry, chemical oceanography, limnology, forestry, terrestrial ecology, microbiology, biophysics, geography and remote sensing as well as mathematics. These twenty-three scientists met to discuss whether there was, at this time, a set of scientific issues concerning life and the entire Earth as a single unit, to set down the major tractable issues, and to suggest a set of activities that would promote the study of the issues identified. Their conclusions are summarized.

Botkin, D. B.↗
NASA NTRS1981

Fundamental aspects in the quantitative ultrasonic determination of fracture toughness: General equations

The problem of establishing a theoretical groundwork for experimentally-found correlations between ultrasonic and fracture toughness factors in polycrystalline metals is discussed. It is noted that the link between these material properties and ultrasonic factors are the microstructural parameters that interact with stress wave propagation during deformation and fracture. The dynamic response of material inhomogeneities and the strains and displacements they undergo under incident stress waves are considered. Dynamic strains and displacements inside and outside scatterers are treated. The underlying approach, the formulation and governing equations for the eigenstrains, and the determination of the energy due to the presence of inhomogeneities are presented. The stress wave interaction problem is presented in terms of the dynamic eigenstrain concept.

Fu, L. S.↗