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Noncontained rotor failures in U.K. engines resulting from low cycle fatigue, low cycle fatigue with superimposed high cycle fatigue, and overheating and-or overspeeding were analyzed. The size, shape, weight, velocity, energy, and direction of the fragments released from turbines and compressors were studied and are presented in graph.
Technologies are reviewed for improving the thermal stability of jet fuels, with reference to the overheating of fuel tanks in supersonic aircraft. Consideration is given to the development of a jet fuel with high thermal stability by the Polish petroleum industry.
The monolithic multijunction converter is an attractive approach to achieving solar/electric conversion with greater than 30% efficiency. A major technical challenge in the development of such devices is the requirement for low resistance, optically transparent intercell contacts between adjacent junctions. These contacts should transmit, without significant loss, the spectral fraction of the incident sunlight which is not absorbed and converted in the overlying junction materials. Their contact resistances must be low enough to prevent significant I to the 2d power R loss at the designed current density levels. They should also exhibit adequate thermal conductivity to prevent device overheating when subjected to the designed illumination level. Recent encouraging results for the development of such contacts are presented.
Solar-collector system projects oval-shaped color-band images onto solar cells designed to be most efficient at specific wavelength. Image size can be altered by changing width of reflecting mirror of power of lens. Image intensity is thus kept at optimum level, preventing cells from overheating.
Spherical harmonic analysis was used to analyze the observed climatological (C) fields of temperature at 850 mb, geopotential height at 500 mb, and sea level pressure. The spherical harmonic method was also applied to the corresponding "model climatological" fields (M) generated by a general circulation model, the "GISS climate model." The climate model was initialized with observed data for the first of December 1976 at 00. GMT and allowed to generate five years of meteorological history. Monthly means of the above fields for the five years were computed and subjected to spherical harmonic analysis. It was found from the comparison of the spectral components of both sets, M and C, that the climate model generated reasonable 500 mb geopotential heights. The model temperature field at 850 mb exhibited a generally correct structure. However, the meridional temperature gradient was overestimated and overheating of the continents was observed in summer.
High energy density capacitors made from metallized polyvinylidene fluoride film were built and tested. Terminations of aluminum-babbitt, tin-babbitt, and all-babbitt were evaluated. All-babbit terminations appeared to be better. The 0.1 microfarad and 2 microfarad capacitors were made of 6 micrometer material. Capacitance, dissipation factor, and insulation resistance measurements were made over the ranges -55 C to 125 C and 10 Hz to 100 kHz. Twelve of forty-one 0.1 microfarad capacitors survived a 5000 hour dc plus ac life test. Under the same conditions, the 2 microfarad capacitors exhibited overheating because of excessive power loss. Some failures occurred after low temperature exposures for 48 hours. No failures were caused by vibration or temperature cycling.
Sliding barrel and shutter protect against overheating. Downward movement of shutter initiated by melting of fuse wire that suspends it. Shutter lowered or raised under operator's control by depressuring or pressurizing hydraulic cylinder.
Medium-pressure mercury-vapor lamps provide high ratio of ultraviolet to total power. Chamber for evaluating solar-ultraviolet (UV) radiation damage permits accelerated testing without overheating test specimens.
Electrically controlled actuator produces predetermined force, torque, or displacement without motors, solenoids, or gears. Using memory-metal elements, actuator responds to digital input without electronic digitalto-analog conversion. To prevent overheating and consequent loss of hotformed shape, each element protected by thermostat turns off current when predetermined temperature is exceeded. Memory metals used to generate fast mechanical response to electric signals.
Analyses and predicted performance of a 50-mm diameter, spiral-groove face seal to seal liquid oxygen at 5.17 MPa pressure, and operating at surface speeds of 183 m/s are described. The pressure-balanced spiral-groove concept is introduced that circulates spiral-groove flow independent of leakage flow. Independent flow paths preclude overheating from vaporization and consequent flow blockage. The analysis accounts for fluid turbulence and inertia, thermoelastic distortions, and dynamic response. An operating-range map was developed as a function of speed and pressure. The fluid-film analysis is summarized in the Appendix.
Telescoping shield normally stowed around solar receiver protects heat engine and supporting structure from overheating when concentrator aimed few degrees away from line to Sun. When extended, shield intercepts off center concentrated solar radiation. Heat spread out over thermally conductive shield and reradiated diffusely not to cause structural damage.
Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.
Simple addition to ceramic insulating tiles provides backup properties that minimize transfer of heat through tiles when their surfaces become damaged. Addition of 3 percent by weight of 320- or 600-grit silicon carbide powder to ceramic during production results in impregnated tile material that resists overheating. Silicon carbide increases emittance and decreases transmittance of ceramic.
Jets also cool and clean cutting equipment. Modular pick-and-bucket miner suffers from disadvantage: Creates large quantities of potentially explosive coal dust. Dust clogs drive chain and other parts and must be removed by hand. Picks and bucket lips become overheated by friction and be resharpened or replaced frequently. Addition of oscillating and rotating water jets to pick-and-bucket machine keeps down dust, cools cutting edges, and flushes machine. Rotating jets wash dust away from drive chain. Oscillating jets cool cutting surfaces. Both types of jet wet airborne coal dust; it precipitates.
A temperature measurement system, which allows the simultaneous sampling of up to 80 separate thermocouples, was developed. The minimum resolution for the system corresponds to + or - 0.16 C per least significant bit of the A/D converter. The time constant values lambda, for each of the 64 thermocouples, were determined experimentally at 7 mps. Software routines were used to correct the measured temperatures for the effect of lambda for each thermocouple. The temperature measurement system was utilized to study the thermal field of a heated jet discharging perpendicularly into a low and a high disturbance level cross stream for a given momentum flux ratio and for three overheated values. The peak instantaneous temperatures reveal that strong molecular diffusion was operative. Various measures of the thermal field, for the disturbed case, suggest that the jet column remains relatively compact while being buffeted by the ambient turbulence field and that its penetration, into the cross wind, is inhibited by the presence of the strong disturbance field.
The objective of these tests was to determine whether Insta-Foam can be used successfully to protect items inside the solid rocket booster aft skirt during reentry. On some of the early Space Shuttle flights the aft skirt heat shield curtain failed during reentry. This allowed the hot gases to damage some of the equipment, etc., inside the skirt. For example, some of the propellant lines were overheated and ruptured and some of the NSI (nozzle severance) cables were damaged. It was suggested that the Insta-Foam thermal protection system be sprayed over these lines, etc., to protect them during future flights in case of a curtain failure. The tests presented were devised and run to check out the feasibility of this idea.
Noninvasive monitoring of temperatures on inner surface of combustion liner of cooled combustor increases liner life, thereby increasing combustor reliability and performance. Technique used in furnaces, reactors, jet engines, rocket engines, stationary turbines, combustors, and heat exchangers. Growth of internal overheating streaks monitored using output from array of thermocouples on outside wall of combustor. Computer analysis of output indicates temperature pattern on combustor lining. Use of data enables timely liner maintenance or overhaul.
After surveying electrically driven loads used on productive farms, the investigators chose three pumps for testing at voltages and frequencies far outside the normal operating range. These loads extract and circulate water and move heat via air, and all are critical to farm productivity. The object was to determine the envelope of supply voltage and frequency over which these loads would operate stably for time intervals under 1 hour. This information is among that needed to determine the feasibility of supplying critical loads, in case of a utility outage, from a wind driven alternator whose output voltage and frequency will vary dramatically in most continental wind regimes. Other related work is surveyed. The salient features and limitations of the test configurations used and the data reduction are described. The development of simulation models suitable for a small computer are outlined. The results are primarily displayed on the voltage frequency plane with the general conclusion that the particular pump models considered will operate over the range of 50 to 90 Hz and a voltage band which starts below rated, decreases as frequency decreases, and is limited on the high side by excessive motor heating. For example, centrifugal pump operating voltage ranges as extensive .4 to 1.4 appear possible. Particular problems with starting, stalling due to lack of motor torque, high speed cavitation, and likely overheating are addressed in a listing of required properties for wind driven alternators and their controllers needed for use in the isolated or stand alone configuration considered.