Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Jet Surface”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Numerical study of coronal plasma jet formation

A new scenario for solar flare eruption in the coronal holes is analyzed by using MHD stability concepts for a spheromak configuration. The stability properties of a spheromak partially embedded into a conducting surface are studied using three dimensional MHD simulations. In agreement with the analytical theory, a large degree of line-tying stabilizes the spheromak's tilt instability, while the elongation has a destabilizing effect. High-resolution nonlinear simulations also demonstrate current sheet formation at the upper surface of the spheromak, where the tilted magnetic field of the spheromak reconnects with the background magnetic field. The calculated stability threshold and the observed magnetic reconnection support a model of coronal jet eruptions where a dome-like magnetic structure grows through flux emergence on the solar surface, tilts, reconnects, and erupts. Countering the effect from elongation, line-tying strongly stabilizes a spheromak growing from a flux-emergence process, suggesting that to accelerate the onset of eruptive coronal jets, there must be magnetic reconnection at the bottom of the spheromak to detach the structure from the solar surface.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1983

Supersonic jet screech tone cancellation

A new method of supersonic jet screech tone reduction is presented. The method utilizes a sound reflecting surface positioned upstream of the nozzle exit a distance of one-quarter wavelength of the fundamental screech tone. The reflector establishes a standing wave pattern of acoustic waves with a node at the nozzle exit plane. The pressure minimum at the exit halts the screech tone feedback mechanism. Experimental results indicate that the method eliminates supersonic jet screech as effectively as the currently accepted technique using an intrusive tab, but without distortion of the jet flow. The change in shock cell spacing, which occurs with an intrusive tab, does not occur when screech is cancelled with the new technique. The broadband shock-associated noise is also influenced much less when the jet screech tones are eliminated by the new method.

Nagel, R. T.↗
NASA NTRS2015

Preliminary Surface Thermal Design of the Mars 2020 Rover

The Mars 2020 rover, scheduled for launch in July 2020, is currently being designed at NASA's Jet Propulsion Laboratory. The Mars 2020 rover design is derived from the Mars Science Laboratory (MSL) rover, Curiosity, which has been exploring the surface of Mars in Gale Crater for over 2.5 years. The Mars 2020 rover will carry a new science payload made up of 7 instruments. In addition, the Mars 2020 rover is responsible for collecting a sample cache of Mars regolith and rock core samples that could be returned to Earth in a future mission. Accommodation of the new payload and the Sampling Caching System (SCS) has driven significant thermal design changes from the original MSL rover design. This paper describes the similarities and differences between the heritage MSL rover thermal design and the new Mars 2020 thermal design. Modifications to the MSL rover thermal design that were made to accommodate the new payload and SCS are discussed. Conclusions about thermal design flexibility are derived from the Mars 2020 preliminary thermal design experience.

Novak, Keith S.↗
NASA NTRS1995

Flow visualization studies of VTOL aircraft models during Hover in ground effect

A flow visualization study of several configurations of a jet-powered vertical takeoff and landing (VTOL) aircraft model during hover in ground effect was conducted. A surface oil flow technique was used to observe the flow patterns on the lower surfaces of the model. There were significant configuration effects. Wing height with respect to fuselage, the presence of an engine inlet duct beside the fuselage, and nozzle pressure ratio are seen to have strong effects on the surface flow angles on the lower surface of the wing. This test was part of a program to improve the methods for predicting the hot gas ingestion (HGI) for jet-powered vertical/short takeoff and landing (V/STOL) aircraft. The tests were performed at the Jet Calibration and Hover Test (JCAHT) Facility at Ames Research Center.

Mourtos, Nikos J.↗
DOE OSTI2020

Self-organization in 1 atm DC glows with liquid anodes: current understanding and potential applications

Self-organization refers to the spontaneous generation of spatially or temporally organized patterns in an otherwise disordered system. Self-organization is ubiquitous in plasma physics particularly in the low-pressure regime as observed in astrophysical jets or plasma loaded flux loops that form on the surface of the Sun. In recent times, self-organization in atmospheric pressure plasmas has captured the attention of researchers. Its occurrence has been observed in DBD discharges as well as DC 1 atm glows with liquid electrodes. The mechanism of pattern formation is still not well understood. In this work, we briefly review the current understanding of pattern formation in DC glows with liquid anode, surveying past work, application areas, theories on mechanisms of formation from the context of reaction diffusion systems, current experimental work and computational progress towards predicting pattern formation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1972

Wind tunnel investigation of a large scale 35 deg swept wing jet transport model with an external blowing triple slotted flap

An investigation was conducted to determine the aerodynamic characteristics of a large-scale subsonic jet transport model with an externally jet-augmented flap system that would augment lift and provide direct-lift control. The model had a 35 deg swept wing of aspect ratio 7.82 and two side-by-side engines mounted on a single pylon under each wing close to the fuselage. The lift of the flap system was augmented by jet engine exhaust impingement on the triple-slotted flap surfaces. The rearmost flap provided direct lift control. Results were obtained for several combinations of flap deflections at gross thrust coefficients from 0 to 2.0. Three-component longitudinal data are presented with four engines operating. Limited longitudinal and lateral data are presented for asymmetric and symmetric thrust conditions with three engines operating. For the same overall flap deflection, lift coefficient and maximum lift coefficient were improved 13 and 7 percent compared to coefficients obtained with a double-slotted flap configuration. A maximum lift coefficient of 6.3 was obtained at a gross thrust coefficient of 2.0. At the same flap deflection lateral and directional trim moment requirements with an engine inoperative were reduced 55 and 33 percent, respectively, compared to those with the engines located farther outboard on the wing. Trim moment requirements in pitch were also reduced significantly. However, pitching-moment instability occurred and increased with gross thrust coefficient.

Aoyagi, K.↗
NASA NTRS1973

Silica RSI entry simulation tests

Simulated reentry heating of the all-silica surface insulation material under a variety of conditions including arc jet and radiant lamp facilities for up to 100 simulated flight cycles has demonstrated consistent thermal performance capability. Consistent predictability along with demonstrated coating integrity and dimensional stability to 1645 K validates the earlier selection of the all-silica material for the RSI application.

Banas, R. P.↗
NASA NTRS1974

Evaporation in space manufacturing

'Normal evaporation' equations for predicting the compositional changes with time and temperature have been developed and correlated with actual experimental data. An evaporative congruent temperature is defined and used to explain, predict, or plan space experiments on anomalous constitutional melting (on cooling) or solidification (on heating). Uneven evaporation causes reactive jetting forces capable of initiating new convection currents, nongravitational accelerations, surface vibrations, or other disturbances. Applications of evaporation to space manufacturing are described concerning evaporative purification, surface cooling, specimen selection, particles splitting, freezing data interpretation, material loss and dimensional control, and surface contamination or compositional changes.

Li, C. H.↗
NASA NTRS1981

Extinguishing in-flight engine fuel-leak fires with dry chemicals

The fire extinguishant storage temperature requirements were examined for several commercially available dry chemicals. Particular emphasis was placed on the development of dry powder extinguishant that, when discharged into a jet engine fuel leak fire, would stick to the hot surfaces. Moreover, after putting out the initial fire, these extinguishants would act as antireignition catalysts, even when the fuel continued to leak onto the heated surface.

Altman, R. L.↗
NASA NTRS1988

Non-contaminating method to reduce Marangoni convection in microgravity float zones

A ground-based experiment has validated the effectiveness of a noncontaminating method developed to reduce Marangoni (thermal capillary) convection in float-zone processing of corrosive materials in space microgravity. A drop of silicone oil 1.5 mm high was enclosed in a transparent box, and the small size of the drop was shown to suppress the 1-g thermal-buoyant convection. A vertical jet of air was blown tangentially over a vertical free surface, producing a viscous shear drag which opposes the Marangoni surface shear. A 66 percent reduction in Marangoni velocities was found in the lowest one-third of the drop, corresponding to the resolidification surface in a float-zone melt.

Dressler, R. F.↗
NASA NTRS1988

Three-dimensional viscous flow computations of a circular jet in subsonic and supersonic cross flow

Three-dimensional viscous flow computations are presented for 90 deg. injection angle jets in subsonic and supersonic crossflow. Comparisons with experimental data include jet centerline and vortex trajectories for the subsonic crossflow, and surface pressure measurement for the supersonic crossflow case. The vortices induced in the jet/freestream interaction are computed and illustrated. The vortices persist in subsonic flow and die out quickly in supersonic flow. The structure of the shocks in the unconfined supersonic flow is illustrated.

Harloff, G. J.↗
NASA NTRS1992

Effects of the LDEF environment on the Ag/FEP thermal blankets

This presentation was made by Francois Levadou at the NASA Langley Research Center LDEF materials workshop, November 19-22, 1991. It represents the results to date on the examination of silvered teflon thermal blankets primarily from the Ultra-heavy Cosmic Ray Experiment and also from the blanket from the Park Seed Company experiment. ESA/ESTEC and Boeing conducted a number of independent measurements on the blankets and in particular on the exposed fluorinated ethylene-propylene (FEP) layer of the blankets. Mass loss, thickness, and thickness profile measurements have been used by ESA, Boeing, and NASA LeRC to determine recession and average erosion yield under atomic oxygen exposure. Tensile strength and percent elongation to failure data, surface characterization by ESCA, and SEM images are presented. The Jet Propulsion Laboratory analysis of vacuum radiation effects is also presented. The results obtained by the laboratories mentioned and additional results from the Aerospace Corporation on samples provided by Boeing are quite similar and give confidence in the validity of the data.

Levadou, Francois↗
NASA NTRS1992

Development of soil moisture retrieval algorithm for L-band SAR measurements

A study of algorithm development and testing for soil moisture retrieval for bare fields using L-band synthetic aperture radar (SAR) imagery is reported. First-order surface scattering models predict that the copolarization ratio is sensitive to soil moisture but not to surface roughness. All possible ratios of the co-polarization signals and their linear combinations are evaluated. The best sensitivity to soil moisture is achieved from measurements as predicted by the first-order surface scattering model. The effects of system noise and volume scattering of soil are evaluated. To minimize the effect of the volume scattering, an algorithm which includes both the surface and volume scattering has been developed and tested using Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) data. The results show that the estimation of soil moisture can be improved after removing the system noise and including the volume scattering effect at large incidence angles.

Shi, Jiancheng↗
NASA NTRS1997

Reactive Hydrodynamics in Rotating Spherical and Cylindrical Geometry

In turbulent spray combustion among many complex interactions between local flow structures called turbulent eddies and droplets are those associated with rotation of droplets. In general, for a complete statistical description of turbulent sprays, consideration of at least four degrees of freedom respectively associated with translational, rotational, vibrational (pulsational), and internal motions of the droplet are needed. Clearly the interactions between all degrees of freedom of the droplets and those for the gaseous background field will be exceedingly complex. For example, one type of interaction between the translational and the rotational velocity of droplets results in droplet helicity, H(d) = w(d).v(d), the significance of which in turbulent spray combustion is yet to be recognized. The role of droplet rotation in turbulent spray combustion modeling and its impact on the evaporation of liquid fuel droplets was recently investigated. Also, the impact of rotation on combustion of solid particles such as is encountered in pulverized coal combustion has been emphasized. The problem of viscous flow around a rotating sphere discussed above also occurs in other areas of physical sciences such as astrophysics and geophysics. Consequently, the subject has been addressed in many classical as well as more recent investigations. According to these investigations, the rotation of a rigid sphere in an otherwise quiescent, unconfined environment results in the motion of the fluid towards the poles. The polar flows from the northern and southern hemispheres move along helical trajectories towards the equatorial plane. Eventually, the polar flows collide at the equatorial plane, thus producing a sheet of rotating fluid that is radially ejected outward on this plane. Therefore, a droplet induces a strained flow field as a result of its rotation. Since the spatial extent of equatorial jets could easily exceed many droplet diameters, interactions between neighboring droplets are enhanced as a result of their rotation. Also, the equatorial jet substantially alters the spherical geometry of the diffusion flame surface that surrounds a rotating droplet. The objective of the research is to gain more knowledge about the hydrodynamics within and around rotating spherical and cylindrical body of fluid, and the behavior of diffusion or premixed flame surfaces that could surround such symmetric body of rotating fluid.

Sohrab, Siavash H.↗