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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Material and tribological considerations for turbopump bearings

The frictional heat generation in the rolling/sliding contact areas of high pressure oxygen turbopump (HPOTP) bearings is a key factor in bearing life. Several bulk materials, surface treatments and coatings are examined for their attributes of rolling contact fatigue life, wear and friction. Emphasis is given to the frictional response of these materials under conditions of rolling with incipient sliding as predicted from HPOTP bearing analysis. Rolling contact fatigue life is shown to be significantly improved with silicon nitride. Fatigue life can also be improved by coating the chromium carbide-laden stainless steels (440C, BG42) with TiN and thin dense chrome. The traction (friction under rolling/sliding) of these materials is discussed in terms of microslip and the presence of interfacial films.

Wedeven, L. D.↗
NASA NTRS1991

Effects of coolant parameters on steady state temperature distribution in phospheric-acid fuel cell electrode

The influence of thermophysical properties and flow rate on the steady-state temperature distribution in a phosphoric-acid fuel cell electrode plate was experimentally investigated. An experimental setup that simulates the operating conditions prevailing in a phosphoric-acid fuel cell stack was used. The fuel cell cooling system utilized three types of coolants to remove excess heat generated in the cell electrode and to maintain a reasonably uniform temperature distribution in the electrode plate. The coolants used were water, engine oil, and air. These coolants were circulated at Reynolds number ranging from 1165 to 6165 for water; 3070 to 6864 for air; and 15 to 79 for oil. Experimental results are presented.

Alkasab, K. A.↗
NASA NTRS1992

Measurements of the fundamental thermodynamic parameters of Li/BCX and Li/SOCl2 cells

Two experimental techniques - equilibrium or reversible cell discharge and measurement of open circuit potential as a function of temperature - are used to determine the thermodynamic data needed to estimate the heat generation characteristics of Li/BCX and Li/SOCl2 cells. The results obtained showed that the reversible cell potential, the temperature dependence of the reversible cell potential, and the thermoneutral potential of the BCX cell were 3.74 V, -0.857 +/- 0.198 mV/K, and 3.994 +/- 0.0603 V, respectively. The respective values obtained for the Li/SOCl2 cell were 3.67 V, -0.776 +/- 0.255 mV/K, and 3.893 +/- 0.0776 V. The difference between the thermoneutral potential of Li/BCX and Li/SCl2 cells is attributable to the difference in their electroactive components.

Kalu, E. E.↗
NASA NTRS1992

The Tapanui region of New Zealand: Site of a Tunguska around 800 years ago?

Evidence is discussed that the wide-spread fires ca. 800 years ago which denuded the southern provinces of the South Island of New Zealand of the extensive forests present at that time were due to the entry of a large bolide into the atmosphere, the conflagration being ignited by the intense heat generated as this extraterrestrial projectile ablated/detonated in a similar manner to that of the Tunguska object of 1908. These fires led to the extinction of the giant terrestrial bird known as the Moa, and the end of the archaic epoch of Maori history known as the Moa Hunter period. This interpretation is well attested to in Maori myth and legend.

Steel, Duncan↗
NASA NTRS1992

Ceramic matrix composites for rocket engine turbine applications

A program to establish the potential for introducing fiber reinforced ceramic matrix composites (FRCMC) in future rocket engine turbopumps was instituted in 1987. A brief summary of the overall program (both contract and in-house research) is presented. Tests at NASA Lewis include thermal upshocks in a hydrogen/oxygen test rig capable of generating heating rates up to 2500 C/sec. Post thermal upshock exposure evaluation includes the measurement of residual strength and failure analysis. Test results for monolithic ceramics and several FRCMC are presented. Hydrogen compatibility was assessed by isothermal exposure of monolithic ceramics in high temperature gaseous hydrogen plus water vapor.

Herbell, Thomas P.↗
NASA NTRS1992

Component test results from the bearing life improvement program for the Space Shuttle Main Engine oxidizer turbopumps

Interim results from a component test program to improve ball bearing life in the Space Shuttle Main Engine oxygen turbopumps are presented. Two specific bearing applications, using liquid oxygen as the bearing coolant, are addressed. The first, the thrust bearing of the low pressure pump, operates at relatively slow speed with predominantly axial load and little temperature rise in the bulk coolant. Testing has demonstrated a very significant reduction in bearing wear by increasing the bearing internal clearance. Heat generation data was obtained that indicates heavy, intermittent cage-to-ball contact occurs, providing a possible explanation for the observed wear. The second application is the turbine end bearings of the high pressure pump. These bearings operate at high speed and load with the possibility of significant coolant vaporization. Tests on production bearings and bearings having modified internal clearance and curvature yielded scattered but generally poor lives. A dramatic improvement was achieved by coating the standard cage with a thin film of fluorinated ethylene propylene and 15 percent molybdenum disulfide. Very promising results have also been obtained by replacing the standard balls with ones made of silicon nitride, especially in combination with the coated cage.

Keba, John E.↗
NASA NTRS1994

Tank Made Of Connected Cooling Fins

New method of fabricating fin-cooled tank requires half as many arc-welding passes and features more efficient transfer of heat. Fins integral parts of tank structure. Requires only one welding pass per fin, and pass done on unobstructed inside of tank. With inside welding, fins longer and more closely spaced. Method proposed to build tank with 256 fins. Holds water in which radioisotope heat source immersed before use. Water absorbs bremsstrahlung radiation from isotope, and fins dissipate heat generated by absorption.

Schultz, Donald F.↗
NASA NTRS1993

Advanced electric motor technology flux mapping

Design of electric motors which fulfill the needs of Thrust Vector Control (TVC) actuators used in large rocket propelled launch vehicles is covered. To accomplish this end the methodology of design is laid out in some detail. In addition a point design of a motor to fulfill the requirements of a certain actuator specified by MSFC is accomplished and reported upon. In the course of this design great stress has been placed on ridding the actuator of internally generated heat. To conduct the heat out of the motor use is made of the unique properties of the in house MSFC designed driving electronics. This property is that as along as they are operated in a quasi-linear mode the electronics nullify the effects of armature inductance as far as the phase of the armature current versus the rotor position is concerned. Actually the additional inductance due to the extended end turns in this design is of benefit because in the shorted armature failure mode the armature current in the fault (caused by the rotor flux sweeping past the armature) is diminished at a given rotor speed when compared to a more conventional motor with lower inductance. The magnetic circuit is analyzed using electromagnetic finite element methods.

Doane, George B., III↗
NASA NTRS1993

Computer program for analysis of high speed, single row, angular contact, spherical roller bearing, SASHBEAN. Volume 1: User's guide

The computer program SASHBEAN (Sikorsky Aircraft Spherical Roller High Speed Bearing Analysis) analyzes and predicts the operating characteristics of a Single Row, Angular Contact, Spherical Roller Bearing (SRACSRB). The program runs on an IBM or IBM compatible personal computer, and for a given set of input data analyzes the bearing design for it's ring deflections (axial and radial), roller deflections, contact areas and stresses, induced axial thrust, rolling element and cage rotation speeds, lubrication parameters, fatigue lives, and amount of heat generated in the bearing. The dynamic loading of rollers due to centrifugal forces and gyroscopic moments, which becomes quite significant at high speeds, is fully considered in this analysis. For a known application and it's parameters, the program is also capable of performing steady-state and time-transient thermal analyses of the bearing system. The steady-state analysis capability allows the user to estimate the expected steady-state temperature map in and around the bearing under normal operating conditions. On the other hand, the transient analysis feature provides the user a means to simulate the 'lost lubricant' condition and predict a time-temperature history of various critical points in the system. The bearing's 'time-to-failure' estimate may also be made from this (transient) analysis by considering the bearing as failed when a certain temperature limit is reached in the bearing components. The program is fully interactive and allows the user to get started and access most of its features with a minimal of training. For the most part, the program is menu driven, and adequate help messages were provided to guide a new user through various menu options and data input screens. All input data, both for mechanical and thermal analyses, are read through graphical input screens, thereby eliminating any need of a separate text editor/word processor to edit/create data files. Provision is also available to select and view the contents of output files on the monitor screen if no paper printouts are required. A separate volume (Volume-2) of this documentation describes, in detail, the underlying mathematical formulations, assumptions, and solution algorithms of this program.

Aggarwal, Arun K.↗
NASA NTRS1993

Computer program for analysis of high speed, single row, angular contact, spherical roller bearing, SASHBEAN. Volume 2: Mathematical formulation and analysis

Spherical roller bearings have typically been used in applications with speeds limited to about 5000 rpm and loads limited for operation at less than about 0.25 million DN. However, spherical roller bearings are now being designed for high load and high speed applications including aerospace applications. A computer program, SASHBEAN, was developed to provide an analytical tool to design, analyze, and predict the performance of high speed, single row, angular contact (including zero contact angle), spherical roller bearings. The material presented is the mathematical formulation and analytical methods used to develop computer program SASHBEAN. For a given set of operating conditions, the program calculates the bearings ring deflections (axial and radial), roller deflections, contact areas stresses, depth and magnitude of maximum shear stresses, axial thrust, rolling element and cage rotational speeds, lubrication parameters, fatigue lives, and rates of heat generation. Centrifugal forces and gyroscopic moments are fully considered. The program is also capable of performing steady-state and time-transient thermal analyses of the bearing system.

Aggarwal, Arun K.↗
NASA NTRS1993

Imaging radar studies of polar ice

A vugraph format presentation is given. The following topics are discussed: scientific overview, radar data opportunities, sea ice investigations, and ice sheet investigations. The Sea Ice Scientific Objectives are as follows: (1) to estimate globally the surface brine generation, heat flux, and fresh water advection (as ice); (2) to monitor phasing of seasonal melt and freeze events and accurately estimate melt and growth rates; and (3) to develop improved treatment of momentum transfer and ice mechanics in coupled air-sea-ice models.

Carsey, Frank↗
NASA NTRS1993

Lithium D-cell study

The purpose of this contract is to evaluate parametrically the effects of various factors including the electrolyte type, electrolyte concentration, depolarizer type, and cell configuration on lithium cell electrical performance and safety. This effort shall allow for the selection and optimization of cell design for future NASA applications while maintaining close ties with WGL's continuous improvements in manufacturing processes and lithium cell design. Taguchi experimental design techniques are employed in this task, and allow for a maximum amount of information to be obtained while requiring significantly less cells than if a full factorial design were employed. Acceptance testing for this task is modeled after the NASA Document EP5-83-025, Revision C, for cell weights, OCV's and load voltages. The performance attributes that are studied in this effort are fresh capacity and start-up characteristics evaluated at two rates and two temperatures, shelf-life characteristics including start-up and capacity retention, and iterative microcalorimetry measurements. Abuse testing includes forced over discharge at two rates with and without diode protection, temperature tolerance testing, and shorting tests at three rates with the measurement of heat generated during shorting conditions.

Size, P.↗
NASA NTRS1992

High efficiency low cost monolithic module for SARSAT distress beacons

The program objectives were to develop a highly efficient, low cost RF module for SARSAT beacons; achieve significantly lower battery current drain, amount of heat generated, and size of battery required; utilize MMIC technology to improve efficiency, reliability, packaging, and cost; and provide a technology database for GaAs based UHF RF circuit architectures. Presented in viewgraph form are functional block diagrams of the SARSAT distress beacon and beacon RF module as well as performance goals, schematic diagrams, predicted performances, and measured performances for the phase modulator and power amplifier.

Petersen, Wendell C.↗
NASA NTRS1993

Thermal analysis of combinatorial solid geometry models using SINDA

Algorithms have been developed using Monte Carlo techniques to determine the thermal network parameters necessary to perform a finite difference analysis on Combinatorial Solid Geometry (CSG) models. Orbital and laser fluxes as well as internal heat generation are modeled to facilitate satellite modeling. The results of the thermal calculations are used to model the infrared (IR) images of targets and assess target vulnerability. Sample analyses and validation are presented which demonstrate code products.

Gerencser, Diane↗
NASA NTRS1994

Non-volatile, solid state bistable electrical switch

A bistable switching element is made of a material whose electrical resistance reversibly decreases in response to intercalation by positive ions. Flow of positive ions between the bistable switching element and a positive ion source is controlled by means of an electrical potential applied across a thermal switching element. The material of the thermal switching element generates heat in response to electrical current flow therethrough, which in turn causes the material to undergo a thermal phase transition from a high electrical resistance state to a low electrical resistance state as the temperature increases above a predetermined value. Application of the electrical potential in one direction renders the thermal switching element conductive to pass electron current out of the ion source. This causes positive ions to flow from the source into the bistable switching element and intercalate the same to produce a non-volatile, low resistance logic state. Application of the electrical potential in the opposite direction causes reverse current flow which de-intercalates the bistable logic switching element and produces a high resistance logic state.

Williams, Roger M.↗
NASA NTRS1994

Calculation of the thermoneutral potential of NiCd and NiH2 cells

The thermoneutral potential of a nickel cadmium or nickel hydrogen cell is the potential at which the cell charge or discharge process puts out zero heat, and thus is the potential corresponding to the enthalpy change of the charge/discharge reaction, delta H. A relatively straightforward method for obtaining the thermoneutral potential E(sub tn), is based on the measured potential and temperature derivative of the cell reactions, which are related to the free energy change delta G, and entropy change delta S, respectively. Particularly in the nickel hydrogen cell, the pressure of hydrogen can often vary over an order of magnitude or more during the course of a charge or discharge. In a nickel cadmium cell, although significant changes in oxygen pressure can occur during charge or discharge, since oxygen does not enter into the charge/discharge reaction, these pressure changes are related to the heat generated from oxygen evolution and recombination. However, the entropy changes due to changes in hydrogen pressure relative to the 1 atm standard state must be included to apply this method to the nickel hydrogen cell.

Zimmerman, Albert H.↗
NASA NTRS1994

Brush Seal Performance and Durability Issues Based on T-700 Engine Test Results

The integrity and performance of brush seals have been established. Severe bench and engine tests have shown high initial wear or run-in rates, material smearing at the interface, and bristle and rub-runner wear, but the brush seals did not fail. Short-duration (46 hr) experimental T-700 engine testing of the compressor discharge seal established over 1-percent engine performance gain (brush versus labyrinth). Long-term gains were established only as leakage comparisons, with the brush at least 20 percent better at controlling leakage. Long-term materials issues, such as wear and ultimately seal life, remain to be resolved. Future needs are cited for materials and analysis tools that account for heat generation, thermomechanical behavior, and tribological pairing to enable original equipment manufacturers to design high-temperature, high-surface-speed seals with confidence.

Hendricks, R. C.↗
NASA NTRS1994

Computer tools for face seal analyses developed at John Crane

The purposes of the computer tools for face seal analysis are new product optimization, existing seals on new applications, existing seals on off-duty conditions, and trouble-shooting. Discussed in this viewgraph presentation are interface forces, friction/heat generation, heat transfer/temperature distribution, axisymmetric pressure/thermal distortion, leakage, and an example case.

Wu, Shifeng↗