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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust

The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.

Von Glahn, U. H.↗
DOE OSTI2023

Method and system to measure gas flow

A system for measuring gas flow generally including a passive acoustic wave generator disposed in a gas flow stream to passively generate an audio signal through vortex shedding, a sound capturing instrument disposed outside the gas stream to produce an electrical signal representative of the acoustic signal, a temperature sensor to obtain temperature measurements indicative of the temperature of the gas flow stream and a control system for determining the gas flow, such as velocity or flow rate, as a function of the acquired acoustic and temperature measurements. The acoustic wave generator includes a corrugated flow channel whose geometric design is so tuned to generate an acoustic emission whose frequency signature varies as a function of the gas flow velocity. The control system may acquires time-domain acoustic data, and process that data to obtain a frequency-domain representation from which gas velocity or gas flow rate can be determined.

Cetiner, Mustafa S.↗
NASA NTRS1975

Advanced supersonic propulsion study, phase 2

A continuation of the NASA/P and WA study to evaluate various types of propulsion systems for advanced commercial supersonic transports has resulted in the identification of two very promising engine concepts. They are the Variable Stream Control Engine which provides independent temperature and velocity control for two coannular exhaust streams, and a derivative of this engine, a Variable Cycle Engine that employs a rear flow-inverter valve to vary the bypass ratio of the cycle. Both concepts are based on advanced engine technology and have the potential for significant improvements in jet noise, exhaust emissions and economic characteristics relative to current technology supersonic engines. Extensive research and technology programs are required in several critical areas that are unique to these supersonic Variable Cycle Engines to realize these potential improvements. Parametric cycle and integration studies of conventional and Variable Cycle Engines are reviewed, features of the two most promising engine concepts are described, and critical technology requirements and required programs are summarized.

Howlett, R. A.↗
NASA NTRS1952

Investigation at Mach Number 1.91 of Spreading Characteristics of Jet Expanding from Choked Nozzles

It is demonstrated that the temperature profiles of jets expanding into a supersonic stream are considerably smaller than the temperature profiles of jets expanding into quiescent air. The effect on the wake of varying afterbody geometry is shown to be small. The gross spreading characteristics of jets expanding from convergent and convergent-divergent nozzles in the base of a body of revolution with various boattail configurations at a Mach number of 1.91 are presented.

EXITS↗
NASA NTRS1972

Flight-test results from two total temperature probes for air-data measurements up to 2014 K (3625 R)

An experimental temperature probe package containing a fluidic oscillator temperature probe and a shielded thermocouple temperature probe was tested during several X-15 flights. The X-15 flights provided greatly varying test conditions, including a wide range of rapidly changing total temperatures and Mach numbers which extended from subsonic to hypersonic speeds. Within restricted ranges of free-stream Mach number, free-stream unit weight flow, and local stagnation pressure, both probes yielded ramp outputs of temperature parallel to ramp inputs of free-stream total temperature. Within these ranges both probes were used to determine total temperature in the Mach 6 temperature environment. Because ambient temperature was known, both probes were used to estimate velocity and Mach number.

Nugent, J.↗
NASA NTRS1988

Gas-jet and tangent-slot film cooling tests of a 12.5 deg cone at Mach number of 6.7

Tests were conducted in the Langley 8-Foot High Temperature Tunnel to determine the aerothermal effects of gaseous nitrogen-coolant ejection on a 3-ft base-diameter, 12.5 degree half-angle cone. Free-stream Mach number, total temperature, and unit Reynolds number per foot were 6.7, 3300 deg R, and 1.4 million, respectively. Two coolant ejection noses were tested, an ogive frustum with a forward-facing 0.8-in radius gas-jet tip, and a 3-in radius hemisphere with a 0.243-in high rearward-facing tangent slot. Data include surface pressures and heating rates, shock shapes, and shock-layer profiles; results are compared with no-cooling data obtained with 1-in and 3-in radius solid noses. Surface pressures were reduced with gas-jet ejection but were affected little by tangent-slot ejection. For both gas-jet and tangent-slot ejection, high coolant flow rates reduced heating even far downstream from the region of ejection; however, low coolant rates caused transition to turbulence and increased heating. Shock-layer profiles of pitot pressure, Mach number, and total temperature were reduced for both gas-jet and tangent-slot ejection. Insight into the gas-jet heat-flux mechanisms was obtained by using shock-layer rake data and established, no-cooling, heat-transfer equations.

Nowak, Robert J.↗
NASA NTRS2007

Effect of Temperature on Jet Velocity Spectra

Statistical jet noise prediction codes that accurately predict spectral directivity for both cold and hot jets are highly sought both in industry and academia. Their formulation, whether based upon manipulations of the Navier-Stokes equations or upon heuristic arguments, require substantial experimental observation of jet turbulence statistics. Unfortunately, the statistics of most interest involve the space-time correlation of flow quantities, especially velocity. Until the last 10 years, all turbulence statistics were made with single-point probes, such as hotwires or laser Doppler anemometry. Particle image velocimetry (PIV) brought many new insights with its ability to measure velocity fields over large regions of jets simultaneously; however, it could not measure velocity at rates higher than a few fields per second, making it unsuitable for obtaining temporal spectra and correlations. The development of time-resolved PIV, herein called TR-PIV, has removed this limitation, enabling measurement of velocity fields at high resolution in both space and time. In this paper, ground-breaking results from the application of TR-PIV to single-flow hot jets are used to explore the impact of heat on turbulent statistics of interest to jet noise models. First, a brief summary of validation studies is reported, undertaken to show that the new technique produces the same trusted results as hotwire at cold, low-speed jets. Second, velocity spectra from cold and hot jets are compared to see the effect of heat on the spectra. It is seen that heated jets possess 10 percent more turbulence intensity compared to the unheated jets with the same velocity. The spectral shapes, when normalized using Strouhal scaling, are insensitive to temperature if the stream-wise location is normalized relative to the potential core length. Similarly, second order velocity correlations, of interest in modeling of jet noise sources, are also insensitive to temperature as well.

Bridges, James E.↗
NASA NTRS1976

An analysis of data related to the minimum temperatures for valid testing in cryogenic wind tunnels using nitrogen as the test gas

The minimum operating temperature which avoids adverse low temperature effects, such as condensation, has been determined at a free stream Mach number of 0.85 for flow over a 0.137 meter airfoil mounted at zero incidence in the Langley 1/3 meter transonic cryogenic tunnel. The onset of low temperature effects is established by comparing the pressure coefficient measured at a given orifice for a particular temperature with those measured at temperatures sufficiently above where low temperature effects might be expected to occur. The pressure distributions over the airfoil are presented in tabular form. In addition, the comparisons of the pressure coefficient as a function of total temperature are presented graphically for chord locations of 0, 25, 50, and 75 percent. Over the 1.2 to 4.5 atmosphere total pressure range investigated, low temperature effects are not detected until total temperatures are 2 K, or more, below free stream saturation temperatures.

Hall, R. M.↗
NASA NTRS2015

Acoustic Database for Turbofan Engine Core-Noise Sources: Volume - I

In this program, a database of dynamic temperature and dynamic pressure measurements were acquired inside the core of a TECH977 turbofan engine to support investigations of indirect combustion noise. Dynamic temperature and pressure measurements were recorded for engine gas dynamics up to temperatures of 3100 degrees Fahrenheit and transient responses as high as 1000 hertz. These measurements were made at the entrance of the high pressure turbine (HPT) and at the entrance and exit of the low pressure turbine (LPT). Measurements were made at two circumferential clocking positions. In the combustor and inter-turbine duct (ITD), measurements were made at two axial locations to enable the exploration of time delays. The dynamic temperature measurements were made using dual thin-wire thermocouple probes. The dynamic pressure measurements were made using semi-infinite probes. Prior to the engine test, a series of bench, oven, and combustor rig tests were conducted to characterize the performance of the dual wire temperature probes and to define and characterize the data acquisition systems. A measurement solution for acquiring dynamic temperature and pressure data on the engine was defined. A suite of hardware modifications were designed to incorporate the dynamic temperature and pressure instrumentation into the TECH977 engine. In particular, a probe actuation system was developed to protect the delicate temperature probes during engine startup and transients in order to maximize sensor life. A set of temperature probes was procured and the TECH977 engine was assembled with the suite of new and modified hardware. The engine was tested at four steady state operating speeds, with repeats. Dynamic pressure and temperature data were acquired at each condition for at least one minute. At the two highest power settings, temperature data could not be obtained at the forward probe locations since the mean temperatures exceeded the capability of the probes. The temperature data were processed using software that accounts for the effects of convective and conductive heat transfer. The software was developed under previous NASA sponsored programs. Compensated temperature spectra and compensated time histories corresponding to the dynamic temperature of the gas stream were generated. Auto-spectral and cross-spectral analyses of the data were performed to investigate spectral features, acoustic circumferential mode content, signal coherence, and time delays. The dynamic temperature data exhibit a wideband and fairly flat spectral content. The temperature spectra do not change substantially with operating speed. The pressure spectra in the combustor and ITD exhibit generally similar shapes and amplitudes, making it difficult to identify any features that suggest the presence of indirect combustion noise. Cross-spectral analysis reveal a strong correlation between pressure and temperature fluctuations in the ITD, but little correlation between temperature fluctuations at the entrance of the HPT and pressure fluctuations downstream of it. Temperature fluctuations at the entrance of the low pressure turbine were an order of magnitude smaller than those at the entrance to the high pressure turbine. Time delay analysis of the temperature fluctuations in the combustor was inconclusive, perhaps due to the substantial mixing that occurs between the upstream and downstream locations. Time delay analysis of the temperature fluctuations in the ITD indicate that they convect at the mean flow speed. Analysis of the data did not reveal any convincing indications of the presence of indirect combustion noise. However, this analysis has been preliminary and additional exploration of the data is recommended including the use of more sophisticated signal processing to explore subtle issues that have been revealed but which are not yet fully understood or explained.

Aeroacoustics↗
NASA NTRS1985

Solar heated oil shale pyrolysis process

An improved system for recovery of a liquid hydrocarbon fuel from oil shale is presented. The oil shale pyrolysis system is composed of a retort reactor for receiving a bed of oil shale particules which are heated to pyrolyis temperature by means of a recycled solar heated gas stream. The gas stream is separated from the recovered shale oil and a portion of the gas stream is rapidly heated to pyrolysis temperature by passing it through an efficient solar heater. Steam, oxygen, air or other oxidizing gases can be injected into the recycle gas before or after the recycle gas is heated to pyrolysis temperature and thus raise the temperature before it enters the retort reactor. The use of solar thermal heat to preheat the recycle gas and optionally the steam before introducing it into the bed of shale, increases the yield of shale oil.

Qader, S. A.↗
NASA NTRS2002

High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated

The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for temperature control and signal conditioning, and packaging designed for high temperatures is necessary for the array to survive the engine environment.

Hunter, Gary W.↗
NASA NTRS1974

Thin-film temperature sensor

Sensor measures rapid temperature changes in fluid streams. Sensor withstands contacts with various corrosive fluids, high fluid-flow rates, and turbulences caused by rapid changes in flow rates. Capacitor is part of resonant bridge circuit which produces ac voltage that is proportional to temperature.

Maserjian, J.↗
NASA NTRS2004

Ground-Based Simulation of Low-Earth Orbit Plasma Conditions: Plasma Generation and Characterization

A 16-cm diameter plasma source operated on argon is described that is capable of producing a plasma environment that closely simulates the low Earth orbit (LEO) conditions experienced by satellites in the altitude range between 300 to 500 km. The plasma source uses a transverse-field magnetic filter, and has been successful in producing low electron temperature plasmas that contain streaming ion populations. Both of these characteristics are important because the plasma in LEO is relatively cold (e.g., Te approx. 0.1 eV) and the ram energy of the ions due to the motion of the satellite relative to the LEO plasma is high (e.g., 7,800 m/s which corresponds to approx. 5 eV for O+ ions). Plasma source operational conditions of flow rate and discharge power are presented that allow the electron temperature to be adjusted over a range from 0.14 to 0.4 eV. The expanding plasma flow field downstream of the source contains both low-energy, charge-exchange ions and streaming ions with energies that are adjustable over a range from 4 eV to 6 eV. At low flow rates and low facility pressures, the streaming ion component of the ion population comprises over 90% of the total plasma density. In the work described herein, a large area retarding potential analyzer was used to measure both electron and ion energy distribution functions in the low density, expanding plasma produced downstream of the plasma source. The benefits of using this type of plasma diagnostic tool in easily perturbed, low-density plasma are identified, and techniques are also discussed that can be used to perform real-time measurements of electron temperature. Finally, recommendations are made that may enable lower electron temperatures to be produced while simultaneously decreasing the plasma source flow rate below 1 to 2 sccm.

Williams, John D.↗
NASA NTRS1990

Properties of large scale plasma flow during the early stage of the plasmaspheric refilling

The objective is to better characterize the macroscopic properties of the interhemisphere plasma flow by solving a more complete set of hydrodynamic equations than that solved previously. Specifically, the ion continuity, momentum and energy equations were solved for the plasma flow along the closed magnetic field lines. During the initial stage of the supersonic outflow in the equatorial region, the ions cool substantially. Using the hydrodynamic model for the large-scale plasma flow, the dynamics of shocks was examined which form in the geomagnetic flux tubes during the early stages of refilling. These shocks are more like those forming in neutral gases than the electrostatic shocks driven by microinstabilities involving ion-ion interaction. Therefore, the shocks seen in the hydrodynamic model are termed as hydrodynamic shocks. Such shocks are generally unsteady and therefore the usual shock jump conditions given by Rankine-Hugoniot relations are not strictly applicable to them. The density, flow velocity and temperature structures associated with the shocks are examined for both asymmetrical and symmetrical flows. In the asymmetrical flow the outflow from one of two conjugate ionospheres is dominant. On the other hand, in the symmetrical case outflows from the two ionospheric sources are identical. Both cases are treated by a two-stream model. In the late type of flow, the early-time refilling shows a relaxation type of oscillation, which is driven by the large-scale interactions between the two identical streams. After this early stage, the resulting temperature structure shows some interesting features. In the equatorial region the streams are isothermal, but in the off-equatorial regions the streams have quite different temperatures, and also densities and flow velocities. The dense and slow stream is found to be warmer than the low-density fast stream. In the late stage of refilling, the temperature is found to steadily increase from the conjugate ionospheres towards the equator; the equatorial temperature is found to be as high as about 8000 K compared to the ionospheric temperature of 3600 K.

Singh, Nagendra↗
NASA NTRS1980

Theoretical study of nonadiabatic boundary-layer stabilization times in a cryogenic wind tunnel for typical stainless steel wing and fuselage models

The time varying effect of nonadiabatic wall conditions on boundary layer properties was studied for a two dimensional wing section and an axisymmetric fuselage. The wing and fuselage sections are representative of the wing root chord and fuselage of a typical transport model for the National Transonic Facility. The analysis was made with a solid wing and three fuselage configurations (one solid and two hollow with varying skin thicknesses) all made from AISI type 310S stainless steel. The displacement thickness and local skin friction were investigated at a station on the model in terms of the time required for these two boundary layer properties to reach an adiabatic wall condition after a 50 K step change in total temperature. The analysis was made for a free stream Mach number of 0.85, a total temperature of 117 K, and stagnation pressures of 2, 6, and 9 atm.

Johnson, C. B.↗
NASA NTRS1972

An observation of the Gulf Stream surface front structure by ship, aircraft, and satellite.

Evaluation of observations of surface temperature and salinity along the western edge of the Gulf Stream made from a ship and of concurrent temperature observations obtained by instrumented aircraft at six altitudes. The major feature along a five-kilometer line normal to the Stream's edge is a temperature gradient of about 0.75 C/kilometer within which are embedded two abrupt temperature increases of about 1.5 C. Temperature variations were compensated by salinity variations, yielding nearly constant density through the frontal zone; a sharp lateral current shear was associated with the thermohaline mixing region between the steps. The attenuation of surface temperature measured by the airborne radiometer was compared with a theoretical model. The analysis supports the view that a two-part correction technique is required: one part for bulk-skin temperature differences, and another for atmospheric attenuation of sea surface emission due to the mass and temperature of interfering gases.

Maul, G. A.↗
DOE OSTI2024

Toward a Universal Model of Hyporheic Exchange and Nutrient Cycling in Streams

In this paper we demonstrate that several ubiquitous hyporheic exchange mechanisms can be represented simply as a one-dimensional diffusion process, where the diffusivity decays exponentially with depth into the streambed. Based on a meta-analysis of 106 previously published laboratory measurements of hyporheic exchange (capturing a range of bed morphologies, hydraulic conditions, streambed properties, and experimental approaches) we find that the reference diffusivity and mixing length-scale are functions of the permeability Reynolds Number and Schmidt Number. These dimensionless numbers, in turn, can be estimated for a particular stream from the median grain size of the streambed and the stream's depth, slope, and temperature. Application of these results to a seminal study of nitrate removal in 72 headwater streams across the United States, reveals: (a) streams draining urban and agricultural landscapes have a diminished capacity for in-stream and in-bed mixing along with smaller subsurface storage zones compared to streams draining reference landscapes; (b) under steady-state conditions nitrate uptake in the streambed is primarily biologically controlled; and (c) median reaction timescales for nitrate removal in the hyporheic zone are 0.5 and 20 hr for uptake by assimilation and denitrification, respectively. While further research is needed, the simplicity and extensibility of the framework described here should facilitate cross-disciplinary discussions and inform reach-scale studies of pollutant fate and transport and their scale-up to watersheds and beyond.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2002

Basal melt beneath whillans ice stream and ice streams A and C

We have used a recently derived map of the velocity of Whillans Ice Stream and Ice Streams A and C to help estimate basal melt. Temperature was modeled with a simple vertical advection-diffusion equation, 'tuned' to match temperature profiles. We find that most of the melt occurs beneath the tributaries where larger basal shear stresses and thicker ice favors greater melt (e.g., 10-20 mm/yr). The occurrence of basal freezing is predicted beneath much of the ice plains of Ice Stream C and Whillans Ice Stream. Modelled melt rates for when Ice Stream C was active suggest there was just enough melt water generated in its tributaries to balance basal freezing on its ice plain. Net basal melt for Whillans Ice Stream is positive due to smaller basal temperature gradients. Modelled temperatures on Whillans Ice Stream, however, were constrained by a single temperature profile at UpB. Basal temperature gradients for Whillans B1 and Ice Stream A may have conditions more similar to those beneath Ice Streams C and D, in which case, there may not be sufficient melt to sustain motion. This would be consistent with the steady deceleration of Whillans stream over the last few decades.

glaciers ice sheets↗