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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Effects of equivalence ratio and dwell time on exhaust emissions from an experimental premixing prevaporizing burner

A flame-tube study was performed to determine the effects of equivalence ratio and residence time on exhaust emissions with premixed, prevaporized propane fuel. Nitrogen oxides emissions as low as .3 g NO2/kg fuel were measured with greater than 99% combustion efficiency at 800 K inlet temperature and an equivalence ratio of .4. For a constant combustion efficiency, lower nitrogen oxides emissions were obtained by burning very lean with relatively long residence times than by using somewhat higher equivalence ratios with shorter times.

Anderson, D.↗
NASA NTRS1975

Effects of equivalence ratio and dwell time on exhaust emissions from an experimental premixing prevaporizing burner

A flame-tube study was performed to determine the effects of equivalence ratio and residence time on exhaust emissions with premixed, prevaporized propane fuel. Nitrogen oxides emissions as low as 0.3 g NO2/kg fuel were measured with greater than 99 percent combustion efficiency at 800 K inlet temperature and an equivalence ratio of 0.4. For a constant combustion efficiency, lower nitrogen oxides emissions were obtained by burning very lean with relatively long residence times than by using somewhat higher equivalence ratios with shorter times.

Anderson, D.↗
NASA NTRS1976

Equivalent constant-amplitude concept for crack growth under spectrum loading

To simplify crack-growth calculations, an equivalent constant-amplitude concept is developed based on the crack-closure phenomenon and on results of pilot tests that showed that the crack-opening load remained essentially constant while cracks grew under repeating random-load sequences containing several thousand load peaks. An equation of crack growth equivalence resulting from derivations based on the crack closure crack growth law is obtained and used to determine a relationship between an equivalent number of cycles of constant-amplitude loading and the distribution of the random loads, the exponent in the crack growth law, and the ratio of the crack-opening load to the maximum load. The validity of the concept is tested experimentally on six different random-load sequences. Good agreement is found between experimental results and theoretical predictions.

Elber, W.↗
NASA NTRS1977

Equivalence principles and electromagnetism

The implications of the weak equivalence principles are investigated in detail for electromagnetic systems in a general framework. In particular, it is shown that the universality of free-fall trajectories (Galileo weak equivalence principle) does not imply the validity of the Einstein equivalence principle. However, the Galileo principle plus the universality of free-fall rotation states does imply the Einstein principle.

Ni, W.-T.↗
NASA NTRS1978

TNT equivalency of M10 propellant

Peak, side-on blast overpressure and scaled, positive impulse have been measured for M10 single-perforated propellant, web size 0.018 inches, using configurations that simulate the handling of bulk material during processing and shipment. Quantities of 11.34, 22.7, 45.4, and 65.8 kg were tested in orthorhombic shipping containers and fiberboard boxes. High explosive equivalency values for each test series were obtained as a function of scaled distance by comparison to known pressure, arrival time and impulse characteristics for hemispherical TNT surface bursts. The equivalencies were found to depend significantly on scaled distance, with higher values of 150-100 percent (pressure) and 350-125 percent (positive impulse) for the extremes within the range from 1.19 to 3.57 m/cube root of kg. Equivalencies as low as 60-140 percent (pressure) and 30-75 percent (positive impulse) were obtained in the range of 7.14 to 15.8 m/cube root of kg. Within experimental error, both peak pressure and positive impulse scaled as a function of charge weight for all quantities tested in the orthorhombic configuration.

Mcintyre, F. L.↗
NASA NTRS1978

Weight propagation and equivalent horsepower for alternate-engined cars

In order to evaluate properly the consequences of replacing conventional Otto-cycle engines with alternate power systems, comparisons must be carried out at the vehicle level with functionally equivalent cars. This paper presents the development and application of a procedure for establishing equivalent vehicles. A systematic weight propagation methodology, based on detailed weight breakdowns and influence factors, yields the vehicle weight impacts due to changes in engine weight and power. Performance-matching criteria, utilizing a vehicle simulation program, are then employed to establish Otto-engine-equivalent vehicles, whose characteristics can form the basis for alternative engine evaluations.

Klose, G. J.↗
NASA NTRS1979

On the equivalence between semiempirical fracture analyses and R-curves

The relationship between several semiempirical fracture analyses (SEFA) and the R-curve concept of fracture mechanics is examined. The conditions for equivalence between a SEFA and an R-curve are derived. A hypothetical material is employed to study the relationship analytically. Equivalent R-curves are developed for real materials using data from the literature. For each SEFA there is an equivalent R-curve whose magnitude and shape are determined by the SEFA formulation and its empirical parameters. If the R-curve is indeed unique then the various empirical parameters cannot be constant, and vice versa. However, for one SEFA the differences are small enough that they may be within the range of normal data scatter for real materials.

Orange, T. W.↗
NASA NTRS1979

On the limitations of the concept of space frequency equivalence

A narrow-band correlation interferometer using directive (large) antennas is equivalent to a wideband correlation interferometer employing isotropic (small) antennas. This concept of space frequency equivalence, due to Kock and Stone, is reexamined and is shown to hold exactly only for the mean or expected values of the correlation interferometer outputs. If their variances are considered, the equivalence disappears, with the variance fo the wideband system always equal to or greater than that of the narrow-band system.

Macphie, R. H.↗
NASA NTRS1980

Predicting tropical cyclone intensity using satellite-measured equivalent blackbody temperatures of cloud tops

A relationship between maximum winds and satellite-measured equivalent blackbody temperatures near tropical cyclones is investigated with data from both the Atlantic and western North Pacific areas. This investigation revealed not only a significant correlation between satellite-derived equivalent blackbody temperatures and maximum winds but also a strong lag relationship between these temperatures and maximum winds. From this latter relationship a regression technique was developed to forecast 24-h changes of the maximum winds for weak (maximum winds less than or equal to 65 kt) and strong (maximum winds greater than 65 kt) tropical cyclones by utilizing the equivalent blackbody temperatures around the storm alone, together with changes in maximum winds during the preceding 24 h and the current maximum winds. Testing of these equations with independent data showed that the mean errors of forecasts made by the equations are lower than the errors in forecasts made by persistence techniques.

Gentry, R. C.↗
NASA NTRS1980

Low order equivalent models of highly augmented aircraft determined from flight data using maximum likelihood estimation

This paper presents the results of a study of the feasibility of using low order equivalent mathematical models of a highly augmented aircraft, the F-8 digital fly-by-wire (DFBW), for flying qualities research. Increasingly complex models were formulated and evaluated using flight data and maximum likelihood estimation techniques. The aircraft actuator was modeled alone first. Next the equivalent derivatives were used to model the longitudinal unaugmented F-8 DFBW aircraft dynamics. The most complex model incorporated a pure time shift of the pilot input, a first order lag, and the basic longitudinal airframe model. This same model was then implemented for the F-8 DFBW aircraft in a highly augmented mode. Excellent matching of the dynamics resulted for this model, indicating that low order equivalent models which are good representations of the highly augmented F-8 DFBW aircraft can be formulated with these methods.

Shafer, M. F.↗
NASA NTRS1980

An equivalent source model of the satellite-altitude magnetic anomaly field over Australia

The low-amplitude, long-wavelength magnetic anomaly field measured between 400 and 700 km elevation over Australia by the POGO satellites is modeled by means of the equivalent source technique. Magnetic dipole moments are computed for a latitude-longitude array of dipole sources on the earth's surface such that the dipoles collectively give rise to a field which makes a least squares best fit to that observed. The distribution of magnetic moments is converted to a model of apparent magnetization contrast in a layer of constant (40 km) thickness, which contains information equivalent to the lateral variation in the vertical integral of magnetization down to the Curie isotherm and can be transformed to a model of variable thickness magnetization. It is noted that the closest equivalent source spacing giving a stable solution is about 2.5 deg, corresponding to about half the mean data elevation, and that the magnetization distribution correlates well with some of the principle tectonic elements of Australia.

Mayhew, M. A.↗
NASA NTRS1980

Apparent violation of the principle of equivalence and killing horizons

By means of the principle of equivalence the qualitative behavior of the Schwarzschild horizon about a uniformly accelerating particle was deduced. This result is confirmed for an exact solution of a uniformly accelerating object in the limit of small accelerations. For large accelerations the Schwarzschild horizon appears to violate the qualitative behavior established via the principle of equivalence. When similar arguments are extended to an observable such as the red shift between two observers, there is no departure from the results expected from the principle of equivalence. The resolution of the paradox is brought about by a compensating effect due to the Rindler horizon.

Zimmerman, R. L.↗
NASA NTRS1981

Adaptation of the TH Epsilon Mu formalism for the analysis of the equivalence principle in the presence of the weak and electroweak interaction

The TH epsilon mu formalism, used in analyzing equivalence principle experiments of metric and nonmetric gravity theories, is adapted to the description of the electroweak interaction using the Weinberg-Salam unified SU(2) x U(1) model. The use of the TH epsilon mu formalism is thereby extended to the weak interactions, showing how the gravitational field affects W sub mu (+ or -1) and Z sub mu (0) boson propagation and the rates of interactions mediated by them. The possibility of a similar extension to the strong interactions via SU(5) grand unified theories is briefly discussed. Also, using the effects of the potentials on the baryon and lepton wave functions, the effects of gravity on transition mediated in high-A atoms which are electromagnetically forbidden. Three possible experiments to test the equivalence principle in the presence of the weak interactions, which are technologically feasible, are then briefly outline: (1) K-capture by the FE nucleus (counting the emitted X-ray); (2) forbidden absorption transitions in high-A atoms' vapor; and (3) counting the relative Beta-decay rates in a suitable alpha-beta decay chain, assuming the strong interactions obey the equivalence principle.

Fennelly, A. J.↗
NASA NTRS1982

Equivalence of the generalized Lie-Hori method and the method of averaging

In this investigation, a comparison is made of two methods for developing perturbation theories for non-canonical dynamical systems. The methods compared are the generalized Lie-Hori method and the method of averaging. In the comparison presented here, the equivalence of the methods up to the second order in the small parameter is shown. However, the approach used can be extended to demonstrate the equivalence for higher orders. To illustrate the equivalence both Duffing's equation and the van der Pol equation are solved using each method.

Ahmed, A.↗
NASA NTRS1982

Measurement of cardiopulmonary performance during acute exposure to a 2440-m equivalent atmosphere

Each of 20 subjects (ranging in age from 18 to 38 years, 15 being male, five female) was given two Bruce Protocol symptom-limited maximum treadmill stress tests, breathing sea-level compressed air (20.9% O2) for one test and a 2440-m equivalent (15.5% O2) for the other. A significant difference was found to exist between measured VO2 max (p less than 0.0002) and exercise time (p less than 0.0004) for the two conditions. No significant differences were observed in heart rate or the recovery time to a respiratory quotient of less than 1. Hemoglobin saturation, as measured by an ear oximeter, averaged 95% for sea-level and 91% for the 2440-m equivalent gases. These results support a 2440-m equivalent contingency atmosphere in the Space Shuttle prior to donning a low-pressure suit for the purpose reducing nitrogen washout times.

Levitan, B. M.↗
NASA NTRS1982

On the validity of equivalent electron fluence for GaAs solar cells

A simple model for particulate radiation damage in shallow-junction heteroface GaAs solar cells is used to evaluate the equivalent electron fluence concept especially in the sense of additivity of electron and proton exposure. It is found that spatial dependent factors for low-energy proton exposure results in a dose dependent equivalent fluence ratio so that additivity within the equivalent fluence concept is generally not possible.

Wilson, J. W.↗
NASA NTRS1983

The damage equivalence of electrons, protons, alphas and gamma rays in rad-hard MOS devices

This paper reports on a study of damage equivalence in rad-hard MOS devices with 100,000 rads (SiO2) capability. Damage sensitivities for electrons of 1, 2, 3, 5, and 7 MeV, protons of 1, 3, 7, 22, and 40 MeV, 3.4-MeV alphas, and Co-60 gammas were measured and compared. Results indicated that qualitatively the same charge recombination effects occurred in hard oxide devices for doses of 100,000 rads (SiO2) as in soft oxide parts for doses of 1 to 4 krads (SiO2). Consequently, damage equivalency or non-equivalency depended on radiation type and energy. However, recovery effects, both during and after irradiation, controlled relative damage sensitivity and its dependency on total dose, dose rate, supply bias, gate bias, radiation type, and energy. Correction factors can be derived from these data or from similar tests of other hard oxide type, so as to properly evaluate the combined effects of the total space environment.

Stassinopoulos, E. G.↗
NASA NTRS1984

Equivalence of the generalized Lie-Hori method and the method of averaging

In this investigation, a comparison is made of two methods for developing perturbation theories for non-canonical dynamical systems. The methods compared are the generalized Lie-Hori method and the method of averaging. In the comparison presented here, the equivalence of the methods up to the second order in the small parameter is shown. However, the approach used can be extended to demonstrate the equivalence for higher orders. To illustrate the equivalence Duffing's equation, the van der Pol equation and the oscillator with quadratic damping problem are solved using each method.

Ahmed, A. H.↗