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Results for “annular slits”

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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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

High-throughput nuclear resonance time domain interferometry using annular slits

Nuclear resonance time domain interferometry (NR-TDI) is used to study the slow dynamics of liquids (that do not require Mössbauer isotopes) at atomic and molecular length scales. Here the TDI method of using a stationary two-line magnetized 57 Fe foil as a source and a stationary single-line stainless steel foil analyzer is employed. The new technique of adding an annular slit in front of a single silicon avalanche photodiode detector enables a wide range of momentum transfers (1 to 100 nm -1 by varying the distance between the annular slits and sample) with a high count rate of up to 160 Hz with a Δ q resolution of ±1.7 nm -1 at q = 14 nm -1 . The sensitivity of this method in determining relaxation times is quantified and discussed. The Kohlrausch–Williams–Watts (KWW) model was used to extract relaxation times for glycerol. These relaxation times give insight into the dynamics of the electron density fluctuations of glycerol as a function of temperature and momentum transfers.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRSDate not supplied

Computational Assessment of Inlet Backflow Effects on Rotating Detonation Engine Performance and Operability

The performance impact of flow reversal at the inlet of an airbreathing rotating detonation engine (RDE) is investigated using 2 and 3-dimensional computational fluid dynamic (CFD) simulations. Flow reversal, or backflow, occurs in RDE inlets in the high-pressure region directly behind the rotating detonation front. This is also where most of the engine thrust or pressure gain is produced. The amount of backflow relative to throughflow depends on the inlet design. For the present work, a simple annular ‘slit’ design is used. The simulations are idealized in several ways, including that fuel and air are premixed, but prevented from reacting when within the inlet region. The results indicate that even with idealizations, the impact of inlet backflow on pressure gain can be substantial. The simulations also reveal an intriguing instability that develops in certain configurations. The mass flow rate into the RDE begins to oscillate at a regular frequency that is substantially less than the detonation rotational frequency. This is accompanied by oscillations in the detonation height. The oscillation amplitude grows over time until the detonation ultimately fails. Both the performance and instability results emphasize the need for carefully designed RDE inlets that provide low loss when flow is in the forward direction, but high resistance when the flow is reversed. Development of such high-diodicity inlets is critical to achieving pressure gain in airbreathing RDE’s.

Detonation↗
NASA NTRSDate not supplied

Computational Assessment of Inlet Backflow Effects on Rotating Detonation Engine Performance and Operability

The performance impact of flow reversal at the inlet of an airbreathing rotating detonation engine (RDE) is investigated using 2 and 3-dimensional computational fluid dynamic (CFD) simulations. Flow reversal, or backflow, occurs in RDE inlets in the high-pressure region directly behind the rotating detonation front. This is also where most of the engine thrust or pressure gain is produced. The amount of backflow relative to throughflow depends on the inlet design. For the present work, a simple annular ‘slit’ design is used. The simulations are idealized in several ways, including that fuel and air are premixed, but prevented from reacting when within the inlet region. The results indicate that even with idealizations, the impact of inlet backflow on pressure gain can be substantial. The simulations also reveal an intriguing instability that develops in certain configurations. The mass flow rate into the RDE begins to oscillate at a regular frequency that is substantially less than the detonation rotational frequency. This is accompanied by oscillations in the detonation height. The oscillation amplitude grows over time until the detonation ultimately fails. Both the performance and instability results emphasize the need for carefully designed RDE inlets that provide low loss when flow is in the forward direction, but high resistance when the flow is reversed. Development of such high-diodicity inlets is critical to achieving pressure gain in airbreathing RDE’s.

detonation↗
NASA NTRS1937

Measurements of Fuel Distribution Within Sprays for Fuel-Injection Engines

Two methods were used to measure fuel distribution within sprays from several types of fuel-injection nozzles. A small tube inserted through the wall of an air tight chamber into which the sprays were injected could be moved about inside the chamber. When the pressure was raised to obtain air densities of 6 and 14 atmospheres, some air was forced through the tube and the fuel that was carried with it was separated by absorbent cotton and weighed. Cross sections of sprays from plain, pintle, multiple-orifice, impinging-jets, centrifugal, lip, slit, and annular-orifice nozzles were investigated, at distances of 1, 3, 5, and 7 inches from the nozzles.

Lee, Dana W↗
NASA NTRS1987

Imaging performance of annular apertures. VI - Limitations by optical surface deviations

The performance of optical systems is limited by imperfect optical surfaces that degrade the images below the level set by wave theoretical limits. The central irradiance functions are derived for slit and circular apertures with five distributions of wavefront errors and for a range of maximal wavefront deviations. For practical frequency of occurrence distributions of wavefront deviations, the point spread and the image energy integral functions are determined. Practical performances of optical systems are derived and performance limits discussed.

Tschunko, Hubert F. A.↗
NASA NTRS1989

Turbomachinery shaft insert

An insert is presented for a hollow rotatable shaft on the end of which an impeller is mounted, the insert having a first cylindrical portion receivable within the end of the shaft. The insert includes a radially extending portion adjacent the end of the shaft having an annular wall including radially inner and outer surfaces for engaging tightly similar surfaces in a recess formed in the impeller to provide inner and outer pilot surfaces. The insert also includes a tubular extension which is received within a bore in the impeller, the tubular extension having spaced longitudinally extending slits for permitting the extension together with radially extending hook-like tongues thereon to be received within radial slots in the bore of the impeller to lock the impeller to the insert.

Vonpragenau, George L.↗
NASA NTRS1976

Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra

Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

Patch, R. W.↗