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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Reusable Hot-Wire Cable Cutter

During the early development stage of balloon deployment systems for missions, nichrome wire cable cutters were often used in place of pyro-actuated cutters. Typically, a nichrome wire is wrapped around a bundle of polymer cables with a low melting point and connected to a relay-actuated electric circuit. The heat from the nichrome reduces the strength of the cable bundle, which quickly breaks under a mechanical load and can thus be used as a release mechanism for a deployment system. However, the use of hand-made heated nichrome wire for cutters is not very reliable. Often, the wrapped nichrome wire does not cut through the cable because it either pulls away from its power source or does not stay in contact with the cable being cut. Because nichrome is not readily soldered to copper wire, unreliable mechanical crimps are often made to connect the nichrome to an electric circuit. A self-contained device that is reusable and reliable was developed to sever cables for device release or deployment. The nichrome wire in this new device is housed within an enclosure to prevent it from being damaged by handling. The electric power leads are internally connected within the unit to the nichrome wire using a screw terminal connection. A bayonet plug, a quick and secure method of connecting the cutter to the power source, is used to connect the cutter to the power leads similar to those used in pyro-cutter devices. A small ceramic tube [0.25-in. wide 0.5-in. long (.6.4-mm wide 13-mm long)] houses a spiraled nichrome wire that is heated when a cable release action is required. The wire is formed into a spiral coil by wrapping it around a mandrel. It is then laid inside the ceramic tube so that it fits closely to the inner surface of the tube. The ceramic tube provides some thermal and electrical insulation so that most of the heat generated by the wire is directed toward the cable bundle in the center of the spiral. The ceramic tube is cemented into an aluminum block, which holds it in position. The leads of the nichrome wire are attached to screw terminals that connect them to power leads. A bayonet plug mounted at the bottom of the rectangular block connects the power leads to a relay circuit. A thin aluminum shell encloses the entire structure, leaving access points to attach to the bayonet plug and to feed a cable into the cylinder. The access holes for the deployment cable are a smaller diameter than the nichrome coil to prevent the cable from coming in direct contact with the nichrome when loaded. It uses the same general method of severing a cable with a heated wire as was used previously, but implements it in such a way that it is more reliable and less prone to failure. It creates a mechanism to create repeatability that was nonexistent in the previous method.

Pauken, Michael T.↗
NASA NTRSDate not supplied

Analysis of Hot-Wire Probe Ice Water Content Measurements in High Ice Water Content Conditions

During the 2022 High Ice Water Content (HIWC) Flight Campaign, ice water content (IWC) measurements were made at various locations on the NASA DC-8 Airborne Science Laboratory using the Isokinetic Probe Version 2 (IKP2), Ice Crystal Detectors (ICD), and Robust Probe. Correlations of a wing mounted ICD to IKP2 were made to determine the collision/retention efficiency of the ICD total water content (TWC) element in glaciated conditions. Similarly, correlations of a nose mounted ICD near the pitot probes were made to the IKP2 and to the wing-mounted ICD to estimate the ice concentration factor near the DC-8 pitot probes. Results from the 2022 flight campaign were compared to results from the HIWC RADAR II flight campaign in 2018. There was an apparent reduction in the ICD TWC collision/retention efficiency during the 2022 flight campaign. Although reasons for this discrepancy were explored, more analyses are needed to fully understand the causes. However, it was concluded that an estimated ice concentration factor at the nose of 2.5 was consistent between the two flight campaigns. Additionally, a correlation model was developed to relate measurements from a Nose ICD to freestream IWC as measured by the IKP2 to support IWC measurements from the 2022 Convective Processes Experiment - Cabo Verde (CPEX-CV) flight campaign.

Icing↗
NASA NTRSDate not supplied

Analysis of Hot-Wire Probe Ice Water Content Measurements in High Ice Water Content Conditions

During the 2022 High Ice Water Content (HIWC) Flight Campaign, ice water content (IWC) measurements were made at various locations on the NASA DC-8 Airborne Science Laboratory using the Isokinetic Probe Version 2 (IKP2), Ice Crystal Detectors (ICD), and Robust Probe. Correlations of a wing mounted ICD to IKP2 were made to determine the collision/retention efficiency of the ICD total water content (TWC) element in glaciated conditions. Similarly, correlations of a nose mounted ICD near the pitot probes were made to the IKP2 and to the wing-mounted ICD to estimate the ice concentration factor near the DC-8 pitot probes. Results from the 2022 flight campaign were compared to results from the HIWC RADAR II flight campaign in 2018. There was an apparent reduction in the ICD TWC collision/retention efficiency during the 2022 flight campaign. Although reasons for this discrepancy were explored, more analyses are needed to fully understand the causes. However, it was concluded that an estimated ice concentration factor at the nose of 2.5 was consistent between the two flight campaigns. Additionally, a correlation model was developed to relate measurements from a Nose ICD to freestream IWC as measured by the IKP2 to support IWC measurements from the 2022 Convective Processes Experiment - Cabo Verde (CPEX-CV) flight campaign.

Icing↗
NASA NTRS1983

Single-wire swirl flow turbulence measurements

A six-orientation, single wire hot wire technique is used to investigate nonswirling and swirling nonreacting flow in an axisymmetric test section with expansion ratio (test section/inlet nozzle diameter) = 2, which may be equipped with a strong contraction nozzle of area ratio 4 at a contraction nozzle downstream distance/test section diameter value = 2. The flowfield contains corner and central recirculation zones typical of gas turbine and ramjet combustion chambers. Swirl may be imparted to the incoming flow by means of a variable angle vane swirler. The effect of swirl on time mean velocities and complete Reynolds stress tensor is investigated, and extensive results are given for swirl vane angles of zero (swirler removed), 38, 45, 60 and 70 deg. The data are being used to aid in the evolution of turbulence models for these complex flow situations. A directional sensitivity analysis is included, which determines the relative accuracy of the measurement technique to approach velocity orientation.

Lilley, D. G.↗
NASA NTRS1987

A critical analysis of transverse vorticity measurements in a large plane shear layer

An evaluation is made of the roles played in four-wire hot wire probe arrays by the influence of (1) the transverse velocity component on pitch angle measurement; (2) the instantaneous spatial gradient of the pitch angle on transverse vorticity computation; (3) the uncertainties in the magnitude of instantaneous pitch angle spatial gradient in the transverse vorticity computation; and (4) the spatial dimension of the microcirculation domain and the evaluation of transverse vorticity. Attention is given to the probe configuration and its computation algorithm.

Foss, J. F.↗
NASA NTRS1987

Flow quality measurements in compressible subsonic flows

The purpose is to re-examine the heat transfer from a hot-wire probe in the compressible subsonic flow regime; describe the three-wire hot-wire probe calibration and data reduction techniques used to measure the velocity, density, and total temperature fluctuation; and present flow quality results obtained in the Langley 0.3 meter Transonic Cryogenic Wind Tunnel and in flight with the NASA JetStar from the same three-wire hot-wire probe.

Stainback, P. Calvin↗
NASA NTRS1975

Analysis of wake vortex flight test data behind a T-33 aircraft

Measurements of the vortex system behind a T-33 aircraft were obtained by a Learjet equipped with a boom carrying a three-wire, hot-wire anemometry probe and other instrumentation. Analysis of the measurements using a computerized geometric method indicated the vortices had a core radius of approximately 0.11 meter with a maximum velocity of 25 meters per second. The hot-wire anemometer was found to be a practical and sensitive instrument for determining in-flight vortex velocities. No longitudinal instabilities, buoyant effects or vortex breakdowns were evident in the data which included vortex wake cross sections from 0.24 to 5.22 kilometers behind the T-33.

Kuhn, G. D.↗