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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Boundary-Layer-Ingesting Inlet Flow Control

This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCP(sub avg)) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow.

Owens, Lewis R.↗
NASA NTRS1950

Effects of Inlet Icing on Performance of Axial-flow Turbojet Engine in Natural Icing Conditions

A flight investigation in natural icing conditions was conducted to determine the effect of inlet ice formations on the performance of axial-flow turbojet engines. The results are presented for icing conditions ranging from a liquid-water content of 0.1 to 0.9 gram per cubic meter and water-droplet size from 10 to 27 microns at ambient-air temperature from 13 to 26 degrees F. The data show time histories of jet thrust, air flow, tail-pipe temperature, compressor efficiency, and icing parameters for each icing encounter. The effect of inlet-guide-vane icing was isolated and shown to account for approximately one-half the total reduction in performance caused by inlet icing.

COMPRESSORS - AXIAL FLOW↗
NASA NTRSDate not supplied

Assessment of Using Ideal Gas for Predicting Boattail Flow at Cryogenic Temperatures

The applicability of using ideal gas assumptions to simulate high Reynolds number experimental data that was obtained at cryogenic temperatures is examined. Flow over an axisymmetric nozzle boattail model was calculated using reference temperatures of 117 K and 300 K and at Reynolds numbers from 50 to 200 million per meter. From the testing perspective, pressure, compression factor, and isentropic coefficients calculated using one-dimensional real gas equations are used to examine the departure of cryogenic flow from ideal gas flow across the range of temperatures and potential impacts on measured aerodynamic data. Solutions developed using ideal gas assumptions in a three-dimensional Navier-Stokes code are compared with experimental data obtained at cryogenic temperatures at two unit Reynolds numbers at freestream Mach numbers of 0.6 and 0.9. Results for several one- and two-equation turbulence models are shown. Predicted pressure coefficient distributions along the nozzle boattail differed from experimental data between 8% to less than 0.5% depending on the turbulence model and Mach number. The greatest discrepancy occurred in the level of static pressure recovery in the recompression region where the flow was separated. Solutions using warm and cryogenic freestream temperatures predicted similar boattail pressure distributions at the same unit Reynolds number.

Nozzle↗
NASA NTRSDate not supplied

Assessment of Using Ideal Gas for Predicting Boattail Flow at Cryogenic Temperatures

The applicability of using ideal gas assumptions to simulate high Reynolds number experimental data that was obtained at cryogenic temperatures is examined. Flow over an axisymmetric nozzle boattail model was calculated using reference temperatures of 117 K and 300 K and at Reynolds numbers from 50 to 200 million per meter. From the testing perspective, pressure, compression factor, and isentropic coefficients calculated using one-dimensional real gas equations are used to examine the departure of cryogenic flow from ideal gas flow across the range of temperatures and potential impacts on measured aerodynamic data. Solutions developed using ideal gas assumptions in a three-dimensional Navier-Stokes code are compared with experimental data obtained at cryogenic temperatures at two unit Reynolds numbers at freestream Mach numbers of 0.6 and 0.9. Results for several one- and two-equation turbulence models are shown. Predicted pressure coefficient distributions along the nozzle boattail differed from experimental data between 8% to less than 0.5% depending on the turbulence model and Mach number. The greatest discrepancy occurred in the level of static pressure recovery in the recompression region where the flow was separated. Solutions using warm and cryogenic freestream temperatures predicted similar boattail pressure distributions at the same unit Reynolds number.

Nozzle↗
NASA NTRS2013

Pneumatic Proboscis Heat-Flow Probe

Heat flow is a fundamental property of a planet, and provides significant constraints on the abundance of radiogenic isotopes, the thermal evolution and differentiation history, and the mechanical properties of the lithosphere. Heat-flow measurements are also essential in achieving at least four of the goals set out by the National Research Council for future lunar exploration. The heat-flow probe therefore directly addresses the goal of the Lunar Geophysical Network, which is to understand the interior structure and composition of the Moon. A key challenge for heat flow measurement is to install thermal sensors to the depths approximately equal to 3 m that are not influenced by the diurnal, annual, and longer-term fluctuations of the surface thermal environment. In addition, once deployed, the heat flow probe should cause little disturbance to the thermal regime of the surrounding regolith. A heat-flow probe system was developed that has two novel features: (1) it utilizes a pneumatic (gas) approach, excavates a hole by lofting the lunar soil out of the hole, and (2) deploys the heat flow probe, which utilizes a coiled up tape as a thermal probe to reach greater than 3-meter depth. The system is a game-changer for small lunar landers as it exhibits extremely low mass, volume, and simple deployment. The pneumatic system takes advantage of the helium gas used for pressurizing liquid propellant of the lander. Normally, helium is vented once the lander is on the surface, but it can be utilized for powering pneumatic systems. Should sufficient helium not be available, a simple gas delivery system may be taken specifically for the heat flow probe. Either way, the pneumatic heat flow probe system would be much lighter than other systems that entirely rely on the electrical power of the lander.

Zacny, Kris↗
NASA NTRS1975

Microwave emission spectrum of the moon - Mean global heat flow and average depth of the regolith

Earth-based observations of the lunar microwave brightness temperature spectrum at wavelengths between 5 and 500 centimeters, when reexamined in the light of physical property data derived from the Apollo program, tentatively support the high heat flows measured in situ and indicate that a regolith thickness between 10 and 30 meters may characterize a large portion of the lunar near side.

Keihm, S. J.↗
NASA NTRS1976

Aerodynamic performance of a 1.20-pressure ratio fan stage designed for low noise

The aerodynamic design and the overall blade element performance of a 51 centimeter diameter fan stage is presented. The stage was designed to minimize the noise generated by rotor stator interactions. The design pressure ratio was 1.20 at a flow of 30.6 kilograms per second and a rotor blade tip speed of 228.6 meters per second. At design speed the rotor peak efficiency was 0.935. The peak efficiency of the stage, however, was 0.824. The radial distribution of rotor performance parameters at peak efficiency and design speed indicated excellent agreement with design values.

Lewis, G. W., Jr.↗
NASA NTRS1983

Measuring Power Flow in Electric Vehicles

Instrument accommodates fast rise and fall times of waveforms characteristic of modern, efficient power controllers. Power meter multiplies analog signals proportional to voltage and current, and converts resulting signal to frequency. Two mechanical counters provided: one for charging, one for discharging.

Griffin, Daniel C., Jr↗
NASA NTRS1997

Modeling of Water Injection into a Vacuum

A loosely coupled two-phase vacuum water plume model has been developed. This model consists of a source flow model to describe the expansion of water vapor, and the Lagrangian equations of motion for particle trajectories. Gas/Particle interaction is modeled through the drag force induced by the relative velocities. Particles are assumed traveling along streamlines. The equations of motion are integrated to obtain particle velocity along the streamline. This model has been used to predict the mass flux in a 5 meter radius hemispherical domain resulting from the burst of a water jet of 1.5 mm in diameter, mass flow rate of 24.2 g/s, and stagnation pressure of 21.0 psia, which is the nominal Orbiter water dump condition. The result is compared with an empirical water plume model deduced from a video image of the STS-29 water dump. To further improve the model, work has begun to numerically simulate the bubble formation and bursting present in a liquid stream injected into a vacuum. The technique of smoothed particle hydrodynamics was used to formulate this simulation. A status and results of the on-going effort are presented and compared to results from the literature.

Alred, John W.↗
NASA NTRSDate not supplied

Key Observations and Discoveries from the Vector Electric Field Investigation on the C/NOFS Satellite

Launched in 2008 and operating for 7.5 years, the Air Force Communication /Navigation Outage Forecasting System (C/NOFS) satellite included the Vector Electric Field Investigation (VEFI) designed and built at NASA’s Goddard Space Flight Center. VEFI successfully met its objectives: 1) investigate the role of ambient electric fields in initiating nighttime density depletions and turbulence; 2) determine the quasi-DC electric fields associated with abrupt density depletions, and 3) quantify the spectrum of the irregularities associated with density depletions, providing many key observations and discoveries including: -- Global (low latitude) vector DC electric fields at 16 s/sec revealing variations with local time, longitude, and season between extremely low and moderate solar activity-- Reversed zonal E x B drifts below the F-region ledge at sunset and simultaneous observations of large scale Kelvin-Helmholtz instabilities as seeds of spread-F -- Large expanses of quasi-coherent kilometer-scale vector wave observations (electric field and density) below 450 km and their discovery as a source of scintillations using the C/NOFS GPS -- Reversed zonal DC electric fields and simultaneous observations of afternoon counter electrojet-- Enhanced zonal DC electric fields at sunrise and full vector plasma flow continuity at the terminator-- Vector electric field and density irregularities extending to meter-scales within equatorial plasma depletions -- Intense electric field structure within the equatorial ionosphere at night in the absence of density depletions -- First observations of the westward equatorial electrojet in post-midnight ionosphere and possible association with downward meridional drifts-- Spaceborne Dst observations and implications for ring current asymmetries-- Vector electric and magnetic field Poynting flux within depletions and TIDs-- Measurements of ionospheric reflectance and Alfvenic waves associated with TIDs-- Observations of Alfven resonators -- ULF magnetic field structure within the nightime equatorial ionosphere-- Discovery of Schumman resonances in space and implications of ELF radiowave propagation-- Vector observations of 50-60 Hz powerline radiation without harmonics-- Ion cyclotron resonance absorption lines associated with ELF hiss and the identification of ambient ions-- Parallel electric fields associated with lower hybrid waves driven by thunderstorm lightning-related sferics-- Discovery of Z-mode radiation in the equatorial ionosphere including its associated with density depletions-- Optical lightning detector waveforms and electric field sferics observed up to altitudes of 800 km

Robert F Pfaff↗
NASA NTRS2017

An Experimental Flow-Through Assessment of Acidic Fe/Mg Smectite Formation on Early Mars

Orbital observations have detected the phyllosilicate smectite in layered material hundreds of meters thick, intracrater depositional fans, and plains sediments on Mars; however, the detection of carbonate deposits is limited. Instead of neutral/alkaline conditions during the Noachian, early Mars may have experienced mildly acidic conditions derived from volcanic acid-sulfate solutions that allowed Fe/Mg smectite formation but prevented widespread carbonate formation. The detection of acid sulfates (e.g., jarosite) associated with smectite in Mawrth Vallis supports this hypothesis. Previous work demonstrated smectite (saponite) formation in closed hydrologic systems (batch reactor) from basaltic glass at pH 4 and 200°C (Peretyazhko et al., 2016 GCA). This work presents results from alteration of basaltic glass from alkaline to acidic conditions in open hydrologic systems (flow-through reactor). Preliminary experiments exposed basaltic glass to deionized water at 190°C at 0.25 ml/min where solution pH equilibrated to 9.5. These initial high pH experiments were conducted to evaluate the flow-through reactor system before working with lower pHs. Smectite at this pH was not produced and instead X-ray diffraction results consistent with serpentine was detected. Experiments are in progress exposing basaltic glass from pH 8 down to pH 3 to determine what range of pHs could allow for smectite formation in this experimental opensystem. The production of smectite under an experimental open-system at low pHs if successful, would support a significant paradigm shift regarding the geochemical evolution of early Mars: Early Mars geochemical solutions were mildly acidic, not neutral/alkaline. This could have profound implications regarding early martain microbiology where acid conditions instead of neutral/alkaline conditions will require further research in terrestrial analogs to address the potential for biosignature preservation on Mars.

Sutter, Brad↗
DOE OSTI2022

Machine Learning Based Network Parameter Estimation Using AMI Data

The expansion of distribution power system and the growing penetration of distributed energy resources present new challenges for situational awareness. Calibrating the extended system model with sensor measurements and maintaining the usability is critical for utilities. This paper presents a distribution network parameter estimation (DNPE) approach using machine learning (ML) and metering data that improve the quality of extended distribution power system modeling. The reliability model can improve the ability of endpoint data to be translated into network-level situational awareness in real time and help distribution system operators (DSOs) solve branch flow and voltage problems. In addition, a data analytic and automate processing scheme is proposed to improve the sensor data quality and prevent misleading information. The effectiveness of the proposed method is verified with actual advanced metering infrastructure (AMI) data on a real utility feeder model, while considering the higher penetration of photovoltaic power generation. The test of DNPE and study results are demonstrated in this paper.

Parameter estimation, machine learning, power dist↗
DOE OSTI2023

Learning Distribution Grid Topologies: A Tutorial

Unveiling feeder topologies from data is of paramount importance to advance situational awareness and proper utilization of smart resources in power distribution grids. This tutorial summarizes, contrasts, and establishes useful links between recent works on topology identification and detection schemes that have been proposed for power distribution grids. The primary focus is to highlight methods that overcome the limited availability of measurement devices in distribution grids, while enhancing topology estimates using conservation laws of power-flow physics and structural properties of feeders. Grid data from phasor measurement units or smart meters can be collected either passively in the traditional way, or actively, upon actuating grid resources and measuring the feeder's voltage response. Analytical claims on feeder identifiability and detectability are reviewed under disparate meter placement scenarios. Such topology learning claims can be attained exactly or approximately so via algorithmic solutions with various levels of computational complexity, ranging from least-squares fits to convex optimization problems, and from polynomial-time searches over graphs to mixed-integer programs. Although the emphasis is on radial single-phase feeders, extensions to meshed and/or multiphase circuits are sometimes possible and discussed. Here this tutorial aspires to provide researchers and engineers with knowledge of the current state-of-the-art in tractable distribution grid learning and insights into future directions of work.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1981

Performance tests of a gas blending system based on mass-flow controllers

The system provides many of the gas mixtures required for calibrating analytical instruments used in engine exhaust gas analysis and is capable of blending from one to four additive gases with either of two carrier gases in concentrations from 20 ppm to 50%. Two mixtures can be flowing simultaneously. Performance tests were made to determine the stability accuracy of the system while it was in limited use for a period of 2 years. The accuracy of the blender was measured by comparing binary mixtures from the blender with National Bureau of Standards standard reference materials. Analytical instruments were used to make these comparisons. The expected accuracy of 2% was obtained in some of the tests, by the majority showed a systematic biAs of -5%. Although these tests revealed subtle instabilities in the flow controllers that contributed to the random scatter of data, the accuracy of wet test meters and bubble flowmeters used for calibration is marginal for this purpose. A simple procedure is recommended that should enable the full potential of the system to be realized.

Evans, A., Jr.↗
NASA NTRS1987

Along-strike magma mixing beneath mid-ocean ridges - Effects on isotopic ratios

The effects of mixing processes on the isotopic variability of midocean ridge basalts are studied. The processes considered are porous flow dispersion and convective mixing in magma chambers. Porous flow dispersion is capable of mixing magmas over distances of only a few tens of meters. Convective mixing, on the other hand, is found to produce continuous magma chambers, where mixing is limited by convective processes, and for discontinuous chambers, where mixing is limited by chamber size. Preliminary comparison of the calculations with observations along the midocean ridges shows that the calculations are consistent with the existence of a correlation between bathymetry and isotopic ratio at long, but not at short, wavelengths. They are also capable of explaining a decrease in isotopic variability with increasing spreading rate.

Kenyon, P. M.↗
NASA NTRS1990

Subsurface energy storage and transport for solar-powered geysers on Triton

The location of active geyser-like eruptions and related features close to the current subsolar latitude on Triton suggests a solar energy source for these phenomena. Solid-state greenhouse calculations have shown that sunlight can generate substantially elevated subsurface temperatures. A variety of models for the storage of solar energy in a subgreenhouse layer and for the supply of gas and energy to a geyser are examined. 'Leaky greenhouse' models with only vertical gas transport are inconsistent with the observed upper limit on geyser radius of about 1.5 km. However, lateral transport of energy by gas flow in a porous N2 layer with a block size on the order of a meter can supply the required amount of gas to a source region about 1 km in radius. The decline of gas output to steady state may occur over a period comparable with the inferred active geyser lifetime of 5 earth years. The required subsurface permeability may be maintained by thermal fracturing of the residual N2 polar cap. A lower limit on geyser source radius of about 50 to 100 m predicted by a theory of negatively buoyant jets is not readily attained.

Kirk, Randolph L.↗