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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 127 records · Page 7

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NASA NTRS1973

Correlation and prediction of gaseous diffusion coefficients.

A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.

Marrero, T. R.↗

NASA NTRS1974

Experimental studies of hypersonic boundary-layer transition and effects of wind tunnel disturbances

Boundary layer transition data on cones and free stream disturbance levels were measured in a hypersonic wind tunnel and Mach 8 variable density hypersonic tunnel. Transition data were obtained by using different conical models and techniques for detecting the location of transition. The disturbance levels were measured by using hot wire anemometry and pressure transducers. The transition Reynolds numbers obtained from the tests correlated well when the fluctuating pressures measured at the surface of conical models were used as a correlating parameter.

Stainback, P. C.↗

NASA NTRS1975

Exhaust pollutant emissions from swirl-can combustor module arrays at parametric test conditions

Improved designs of swirl-can combustor modules were tested using seven-module arrays in a combustor. The combustor was operated over a pressure range of 69 to 207 N/sq cm, a fuel-air ratio range of 0.015 to 0.046, at a constant inlet air temperature of 733 K, and at reference velocities of 23.9 and 30.6 m/sec. The three designs tested performed with high combustion efficiency at all conditions tested and exhibited oxides of nitrogen emissions substantially lower than that of conventional gas turbine combustors. A correlating parameter used to extrapolate oxides of nitrogen emissions to full power or takeoff conditions for large commercial turbofan engines predicts oxides of nitrogen emissions somewhat higher than those specified in the 1979 government emissions standards.

Mularz, E. J.↗

NASA NTRS1975

Gaseous exhaust emissions from a JT8D-109 turbofan engine at simulated cruise flight conditions

Gaseous emissions from a JT8D-109 turbofan engine were measured in an altitude facility at four simulated cruise flight conditions: Mach 0.8 at altitudes of 9.1, 10, 7, and 12.2 km and Mach 0.9 at 10.7 km. Engine inlet air temperature was held constant at 283 K for all tests. Emissions measurements were made at nominally 6 cm intervals across the horizontal diameter of the engine exhaust nozzle with a single-point traversing gas sample probe. Measured emissions of decreased with increasing altitude from an emission index of 10.4 to one of 8.3, while carbon monoxide increased with increasing altitude from an emission index of 1.6 to one of 4.4. Unburned hydrocarbon emissions were essentially negligible for all flight conditions. Since the engine inlet air temperatures were not correctly simulated, the NOx emission indices were corrected to true altitude conditions by using correlating parameters for changes in combustor inlet temperature, pressure, and temperature rise. The correction was small at the lowest altitude. At the 10.7 and 12.2 km, Mach 0.8 test conditions the correction decreased the measured values by 1 emission index.

Diehl, L. A.↗

NASA NTRS1975

Hydrogen interactions with metals

Review of the literature on the nature and extent of hydrogen interactions with metals and the role of hydrogen in metal failure. The classification of hydrogen-containing systems is discussed, including such categories as covalent hydrides, volatile hydrides, polymeric hydrides, and transition metal hydride complexes. The use of electronegativity as a correlating parameter in determining hydride type is evaluated. A detailed study is made of the thermodynamics of metal-hydrogen systems, touching upon such aspects as hydrogen solubility, the positions occupied by hydrogen atoms within the solvent metal lattice, the derivation of thermodynamic functions of solid solutions from solubility data, and the construction of statistical models for hydrogen-metal solutions. A number of theories of hydrogen-metal bonding are reviewed, including the rigid-band model, the screened-proton model, and an approach employing the augmented plane wave method to solve the one-electron energy band problem. Finally, the mechanism of hydrogen embrittlement is investigated on the basis of literature data concerning stress effects and the kinetics of hydrogen transport to critical sites.

Mclellan, R. B.↗

NASA NTRS1975

Space shuttle orbiter reaction control system jet interaction study

The space shuttle orbiter has forward mounted and rear mounted Reaction Control Systems (RCS) which are used for orbital maneuvering and also provide control during entry and abort maneuvers in the atmosphere. The effects of interaction between the RCS jets and the flow over the vehicle in the atmosphere are studied. Test data obtained in the NASA Langley Research Center 31 inch continuous flow hypersonic tunnel at a nominal Mach number of 10.3 is analyzed. The data were obtained with a 0.01 scale force model with aft mounted RCS nozzles mounted on the sting off of the force model balance. The plume simulations were accomplished primarily using air in a cold gas simulation through scaled nozzles, however, various cold gas mixtures of Helium and Argon were also tested. The effect of number of nozzles was tested as were limited tests of combined controls. The data show that RCS nozzle exit momentum ratio is the primary correlating parameter for effects where the plume impinges on an adjacent surface and mass flow ratio is the parameter where the plume interaction is primarily with the external stream. An analytic model of aft mounted RCS units was developed in which the total reaction control moments are the sum of thrust, impingement, interaction, and cross-coupling terms.

Rausch, J. R.↗

NASA NTRS1977

Attenuation of upstream-generated low frequency noise by gas turbines

The acoustic transfer functions of low frequency (below 3500 Hz) noise through aircraft turbines were investigated. Model test results were compared with theoretical predictions in order to assess the validity of the theory. Component tests were conducted on both high pressure and low pressure model turbines. The influence of inlet temperature and turbine speed attenuation was evaluated, while the effects of turbine pressure ratio, blade-row choking, and additional downstream stages were determined. Preliminary identification of pertinent aeroacoustic correlating parameters was made.

Doyle, V. L.↗

NASA NTRS1977

Space shuttle orbiter rear mounted reaction control system jet interaction study

The effect of interaction between the reaction control system (RCS) jets and the flow over the space shuttle orbiter in the atmosphere was investigated in the NASA Langley 31-inch continuous flow hypersonic tunnel at a nominal Mach number of 10.3 and in the AEDC continuous flow hypersonic tunnel B at a nominal Mach number of 6, using 0.01 and .0125 scale force models with aft RCS nozzles mounted both on the model and on the sting of the force model balance. The data show that RCS nozzle exit momentum ratio is the primary correlating parameter for effects where the plume impinges on an adjacent surface and mass flow ratio is the parameter when the plume interaction is primarily with the external stream. An analytic model of aft mounted RCS units was developed in which the total reaction control moments are the sum of thrust, impingement, interaction, and cross-coupling terms.

Rausch, J. R.↗

NASA NTRS1978

Pretest information for a test to validate plume simulation procedures (FA-17)

The results of an effort to plan a final verification wind tunnel test to validate the recommended correlation parameters and application techniques were presented. The test planning effort was complete except for test site finalization and the associated coordination. Two suitable test sites were identified. Desired test conditions were shown. Subsequent sections of this report present the selected model and test site, instrumentation of this model, planned test operations, and some concluding remarks.

Hair, L. M.↗

NASA NTRS1978

Space shuttle orbiter reaction control system interactions with the vehicle flow field

Test data on the effect of the interaction between the space shuttle orbiter rear-mounted reaction control system jets and the flow over the vehicle in the atmosphere are analyzed with particular attention to yaw angle effects. Masted tank-plus-orbiter jet interactions resulting from combinations of forward and rear-mounted reaction control jets being fired prior to external tank staging are also documented. The primary correlating parameter used for the mated data is a single-jet momentum ratioed to free-stream momentum. An analytic model for computing reaction control system interactions for all control combinations used for mated vehicle coast is included.

Rausch, J. R.↗

NASA NTRS1979

Modal propagation angles in ducts with soft walls and their connection with suppressor performance

The angles of propagation of the wave fronts associated with duct modes are derived for a cylindrical duct with soft walls (acoustic suppressors) and a uniform steady flow. The angle of propagation with respect to the radial coordinate (angle of incidence on the wall) is shown to be a better correlating parameter for the optimum wall impedance of spinning modes than the previously used mode cutoff ratio. Both the angle of incidence upon the duct wall and the propagation angle with respect to the duct axis are required to describe the attenuation of a propagating mode. Using the modal propagation angles, a geometric acoustics approach to suppressor acoustic performance was developed. Results from this approximate method were compared to exact modal propagation calculations to check the accuracy of the approximate method. The results are favorable except in the immediate vicinity of the modal optimum impedance where the approximate method yields about one-half of the exact maximum attenuation.

Rice, E. J.↗

NASA NTRS1978

Experimental clean combustor program, phase 3: Noise measurement addendum

The acoustic characteristics of the double annular combustor in a CF6-50 high bypass turbofan engine were investigated. Internal fluctuating pressure measurements were made in the combustor region and in the core exhaust. The transmission loss across the turbine and nozzle was determined from the measurements and compared to previous component results and present theory. The primary noise source location in the combustor was investigated. Spectral comparisons of test rig results were made with the engine results. The measured overall power level was compared with component and engine correlating parameters.

Doyle, V. L.↗

NASA NTRS1979

Modal propagation angles in ducts with soft walls and their connection with suppressor performance

Rice, E. J.↗

NASA NTRS1979

The reaction of the atmosphere to solar disturbances

The effect of solar flares on the thermosphere and the troposphere is investigated. It is found that during periods of geoeffect solar disturbances, there is a connection between phenomena in the upper and lower atmospheres and that variations in atmospheric parameters correlate with changes in the geomagnetic index.

Mikhnevich, V. V.↗

NASA NTRS1980

Core noise investigation of the CF6-50 turbofan engine

The contribution of the standard production annular combustor to the far-field noise signature of the CF6-50 engine was investigated. Internal source locations were studied. Transfer functions were determined for selected pairs of combustor sensors and from two internal sensors to the air field. The coherent output power was determined in the far-field measurements, and comparisons of measured overall power level were made with component and engine correlating parameters.

Doyle, V. L.↗

NASA NTRS1980

A theoretical analysis of simulated transonic boundary layers in cryogenic-nitrogen wind tunnels

A theoretical analysis was made to determine the real gas effects on simulation of transonic boundary layers in wind tunnels with cryogenic nitrogen as the test gas. The analysis included laminar and turbulent flat plate boundary layers and turbulent boundary layers on a two dimensional airfoil. The results indicate that boundary layers in such wind tunnels should not be substantially different from ideal gas boundary layers at standard conditions. At a pressure of 9.0 atm, two separate effects produce deviations of real gas values from ideal gas values which are in the opposite direction from deviations at 1.0 atm and are of the same insignificant order of magnitude. Results also show that nonadiabatic boundary layers should be adequately simulated if the enthalpy ratio is the correlating parameter rather than the temperature ratio.

Adcock, J. B.↗

NASA NTRS1981

A Nonlinear Propulsion System Simulation Technique for Piloted Simulators

In the past, propulsion system simulations used in flight simulators have been extremely simple. This resulted in a loss of simulation realism since significant engine and aircraft interactions were neglected and important internal engine parameters were not computed. More detailed propulsion system simulators are needed to permit evaluations of modern aircraft propulsion systems in a simulated flight environment. A real time digital simulation technique has been developed which provides the capabilities needed to evaluate propulsion system performance and aircraft system interaction on manned flight simulators. A parameter correlation technique is used with real and pseudo dynamics in a stable integration convergence loop. The technique has been applied to a multivariable propulsion system for use in a piloted NASA flight simulator program. Cycle time is 2.0 ms on a Univac 1110 computer and 5.7 ms on the simulator computer, a Xerox Sigma 8. The model is stable and accurate with time steps up to 50 ms. The program evaluated the simulation technique and the propulsion system digital control. The simulation technique and model used in that program are described and results from the simulation are presented.

Mihaloew, J. R.↗

NASA NTRS1979

Bellows flow-induced vibrations

Results of theoretical and experimental investigations of bellows typical of those found in space shuttle external tanks are presented. Correlation parameters are identified which generalize the alternating stress calculations cited in an earlier study. Alternating stress amplitudes and mean stress levels form the basis of a fatigue analysis incorporating seven ordinate charts for 347 stainless steel, alloy 21 6-9, and Inco 718. A crack propagation model is included with a program for computing bellows fatigue life. Two phase flow and material hardness properties are discussed.

Johnson, J. E.↗