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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 397 records · Page 22

All sources NASA NTRS DOE OSTI

NASA NTRS1995

Effects of Gravity on Bubble Formation at a Plate Orifice

A model of the dynamic regime of gas injection through a submerged plate orifice into an ideally wetting liquid is developed in the circumstance when successively detached bubbles may be regarded as independent objects. Two major factors favor bubble detachment: the buoyancy force and a force due to the momentum inflow into the bubble with injected gas. In normal and moderately reduced gravity, the first factor dominates. At relatively low flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole period of its evolution till detachment. If the flow rate exceeds a critical value, another stage of bubble evolution occurs in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical gaseous stem that lengthens as the bubble rises above the plate. The bubble continues to grow until the gas supply through the stem is completely cut off, after which back flow of gas into the stem from the bubble becomes possible. In microgravity, the second factor prevails, and the latter stage is always present irrespective of the flow rate. However, the gas envelope rises and the stem lengthens very slowly. This difference in the underlying physical mechanisms provides for key properties of bubble growth and detachment being drastically different in appreciable and sufficiently reduced gravity. The frequency of bubble formation slightly decreases with and the detachment volume is almost proportional to the gas flow rate in the first case, in accordance with familiar relations. In the second case, the first variable is proportional to the flow rate whereas the second one is independent of it. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.

Webbon, Bruce W.↗

DOE OSTI2022

Understanding syringeability and injectability of high molecular weight PEO solution through time-dependent force-distance profiles

Opioid medications play a vital role in treating moderate to severe pain. Unfortunately, many drug misusers and abusers attempt to alter the formulations or properties of these drugs by manipulation, (e.g., crushing, chewing, smoking, snorting, injecting). The intravenous (IV) route is most dangerous to abusers, as the drugs directly enter the circulatory system and produce intense euphoria. To obtain a full understanding of the impact of syringe factors (e.g., needle gauge size, needle length, syringe barrel size), on the ease of injection, we undertook a comprehensive assessment of syringeability and injectability of manipulated abuse-deterrent formulations (ADFs). A texture analyzer-based testing method was developed for the measurement of the resistance force of pulling, holding, and pushing phases of injections. Results showed that the finer needle gauge sizes required higher injection force to withdraw drug solutions. In addition, the syringed liquid volume was highly dependent on needle gauge size, holding time, and sample viscosity. In most cases, a lower needle gauge number and a longer holding time increased the syringed volume. Needle length was highly correlated to injection force (R 2 = 0.99). Using longer needles to inject drug solution requires greater force. Furthermore, large barrel size was correlated to pushing force (R 2 = 0.99); thus, increasing the difficulty of pushing the plunger of a large syringe with one hand. Lastly, relationships between injection force, sample viscosity, and testing conditions were elucidated using a mathematical model, which could be used in the future to assess and predict injection force of solution samples.

60 APPLIED LIFE SCIENCES↗

NASA NTRS1995

Low gravity transfer line chilldown

Antar, B. N.↗

NASA NTRS1989

Low gravity transfer line chilldown

A code has been developed that solves for the transfer line chilldown time and flow and heat transfer characteristics in one-g environment. The code solves the transient, one dimensional, space averaged mass, momentum, and energy conservation equations for liquid-vapor two-phase flow in tubes. The physical configuration solved is that appropriate for bottom coolant injection in a vertically supported heated tube. Four distinct regions are considered consecutively: fully liquid, inverted annular, dispersed, and fully vapor flow. The conservation equations for both the liquid and the vapor are solved in each region separately. Also, in each region the mass and energy transport between each phase as well as the energy and momentum transport between the tube wall and the fluid are accounted for. A finite wall thickness is also considered. The model described above was solved numerically through a mixed finite difference scheme with forward time marching. The inverted annular regime was resolved using a semi-implicit finite differencing while the dispersed regime was solved explicitly. Also, a staggered mesh was used in which the velocity was resolved at mesh boundaries while all other field variables were resolved at the mesh centroids. Different mesh sizes were used depending on the region of solution. A coarse mesh was used in the dispersed flow region while a much finer mesh was used in both the inverted annular flow region and the tube walls.

B. N. Antar↗

NASA NTRS2015

Capillary Channel Flow (CCF) EU2-02 on the International Space Station (ISS): An Experimental Investigation of Passive Bubble Separations in an Open Capillary Channel

It would be signicantly easier to design fluid systems for spacecraft if the fluid phases behaved similarly to those on earth. In this research an open 15:8 degree wedge-sectioned channel is employed to separate bubbles from a two-phase flow in a microgravity environment. The bubbles appear to rise in the channel and coalesce with the free surface in much the same way as would bubbles in a terrestrial environment, only the combined effects of surface tension, wetting, and conduit geometry replace the role of buoyancy. The host liquid is drawn along the channel by a pump and noncondensible gas bubbles are injected into it near the channel vertex at the channel inlet. Control parameters include bubble volume, bubble frequency, liquid volumetric flow rate, and channel length. The asymmetrically confined bubbles are driven in the cross-flow direction by capillary forces until they at least become inscribed within the section or until they come in contact with the free surface, whereupon they usually coalesce and leave the flow. The merging of bubbles enhances, but does not guarantee, the latter. The experiments are performed aboard the International Space Station as a subset of the Capillary Channel Flow experiments. The flight hardware is commanded remotely and continuously from ground stations during the tests and an extensive array of experiments is conducted identifying numerous bubble flow regimes and regime transitions depending on the ratio and magnitude of the gas and liquid volumetric flow rates. The breadth of the publicly available experiments is conveyed herein primarily by narrative and by regime maps, where transitions are approximated by simple expressions immediately useful for the purposes of design and deeper analysis.

fluid dynamics↗

NASA NTRS1996

High Leverage Space Transportation System Technologies for Human Exploration Missions to the Moon and Beyond

The feasibility of returning humans to the Moon by 2004, the 35th anniversary of the Apollo 11 landing, is examined assuming the use of existing launch vehicles (the Space Shuttle and Titan 4B), a near term, advanced technology space transportation system, and extraterrestrial propellant--specifically 'lunar-derived' liquid oxygen or LUNOX. The lunar transportation system (LTS) elements consist of an expendable, nuclear thermal rocket (NTR)-powered translunar injection (TLI) stage and a combination lunar lander/Earth return vehicle (LERV) using cryogenic liquid oxygen and hydrogen (LOX/LH2) chemical propulsion. The 'wet' LERV, carrying a crew of 2, is configured to fit within the Shuttle orbiter cargo bay and requires only modest assembly in low Earth orbit. After Earth orbit rendezvous and docking of the LERV with the Titan 4B-launched NTR TLI stage, the initial mass in low Earth orbit (IMLEO) is approx. 40 t. To maximize mission performance at minimum mass, the LERV carries no return LOX but uses approx. 7 t of LUNOX to 'reoxidize' itself for a 'direct return' flight to Earth followed by an 'Apollo-style' capsule recovery. Without LUNOX, mission capability is constrained and the total LTS mass approaches the combined Shuttle-Titan 4B IMLEO limit of approx. 45 t even with enhanced NTR and chemical engine performance. Key technologies are discussed, lunar mission scenarios described, and LTS vehicle designs and characteristics are presented. Mission versatility provided by using a small 'all LH2' NTR engine or a 'LOX-augmented' derivative, either individually or in clusters, for outer planet robotic orbiter, small Mars cargo, lunar 'commuter', and human Mars exploration class missions is also briefly discussed.

Borowski, Stanley K.↗

NASA NTRS1991

Autogenous pressurization of cryogenic vessels using submerged vapor injection

Experimental results are reported for submerged injection pressurization and expulsion tests of a 4.89 cu m liquid hydrogen tank. The pressurant injector was positioned near the bottom of the test vessel to simulate liquid engulfment of the pressurant gas inlet; a condition that may occur in low-gravity conditions. Results indicate a substantial reduction in pressurization efficiency, with pressurant gas requirements approximately five times greater than ideal amounts. Consequently, submerged vapor injection should be avoided as a low-gravity autogenous pressurization method whenever possible. The work presented herein validates that pressurent requirements are accurately predicted by a homogeneous thermodynamic model when the submerged injection technique is employed.

Stochl, Robert J.↗

NASA NTRS1991

Autogenous pressurization of cryogenic vessels using submerged vapor injection

Experimental results are reported for submerged injection pressurization and expulsion tests of a 4.89 cu m liquid hydrogen tank. The pressurant injector was positioned near the bottom of the test vessel to simulate liquid engulfment of the pressurant gas inlet, a condition that may occur in low-gravity conditions. Results indicate a substantial reduction in pressurization efficiency with pressurant gas requirements approximately five times greater than ideal amounts. Consequently, submerged vapor injection should be avoided as a low-gravity autogenous pressurization method whenever possible. The work presented herein validates that pressurant requirements are accurately predicted by a homogeneous thermodynamic model when the submerged injection technique is employed.

Stochl, Robert J.↗

NASA NTRS1970

Preparation of fine-particles at cryogenic temperatures

Flash freezing process yields gelling agent for use at cryogenic temperatures. Vaporized material, diluted with an inert gas, is injected below the surface of an agitated cryogenic liquid. This method disperses particles of chlorine trifluoride in liquid oxygen difluoride.

Globus, H.↗

NASA NTRS1981

Laser velocimetry technique applied to the Langley 0.3 meter transonic cryogenic tunnel

A low power laser velocimeter operating in the forward scatter mode was used to measure free stream mean velocities in the Langley 0.3 Meter Transonic Cryogenic Tunnel. Velocity ranging from 51 to 235 m/s was measured. Measurements were obtained for a variety of nominal tunnel conditions: Mach numbers from 0.20 to 0.77, total temperatures from 100 to 250 K, and pressures from 101 to 152 kPa. Particles were not injected to augment the existing Mie scattering materials. Liquid nitrogen droplets were the existing liqht scattering material. Tunnel vibrations and thermal effects had no detrimental effects on the optical system.

Gartrell, L. R.↗

NASA NTRS1981

Steady generation of aerosols with an improved constant output atomizer

It is common practice to generate laboratory aerosols of soluble materials with pneumatic atomizers. In a typical device, a solution of the substance to be aerosolized is injected into a jet of air and the liquid is broken up into very small droplets. After forced evaporation, a dry aerosol of the solute is produced. A number of commercially available devices were tested, and despite differences in design, all the atomizers tested suffered from short- and/or long-term fluctuations of their output particle number concentrations. The mechanisms responsible for atomizer instabilities are discussed and methods for alleviating these problems are considered.

Dea, J. Y.↗

NASA NTRS1984

Pre-existing seed particles and the onset of condensation in cryogenic wind tunnels

The condensation research at NASA Langley Research Center has used a variety of experimental approaches to gather information on seed particles that can act as sites for condensation growth. Total pressure measurements have suggested that condensation growth is caused by impurities in the flow and not by unevaporated liquid nitrogen (LN2) droplets resulting from the LN2 injected to cool the 0.3-Meter Transonic Cryogenic Tunnel. A separate test with an optical droplet sizing probe, which was designed to detect droplets in the 2- to 300-micron range, confirmed the conclusions from the total pressure measurements and also discovered what appears to be solidified oil droplets having diameters of about 3 microns. These oil droplets appear to be the dominant source of seed particles above 2 microns. However, computer simulations of static pressure test data suggest that the measured condensation effects are the result of more numerous, smaller seeds with number densities on the order of 10 to the 12th per kilogram of the gas and diameters on the order of 0.5 microns.

Hall, R. M.↗

NASA NTRS1992

Cheap System Supplies Liquid At Steady High Pressure

High-pressure pumps and pulsation-damping devices not needed. Compressed gas provides pressure in liquid-supply system. Proposed to use system to inject alcohol in fuel-additive tests. Principal advantage of system is elimination of costs of high-pressure pumps and of accompanying costs of pulsation-damping devices.

Morse, C. Robert↗

NASA NTRS1934

Photomicrographic Studies of Fuel Sprays

A large number of photomicrographs of fuel sprays were taken for the purpose of studying the spray structure and the process of spray formation. They were taken at magnifying powers of 2.5, 3.25, and 10, using a spark discharge of very short duration for illumination. Several types and sizes of nozzles were investigated, different liquids were used, and a wide range of injection pressures was employed. The sprays were photographed as they were injected into a glass-walled chamber in which the air density was varied from 14 atmospheres to 0.0013 atmosphere.

Lee, Dana W↗

NASA NTRS2002

Bubble Formation and Detachment in Reduced Gravity Under the Influence of Electric Fields

The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Both uniform and nonuniform electric field configurations were considered. Bubble formation and detachment were recorded and visualized in reduced gravity (corresponding to gravity levels on Mars, on the Moon as well as microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

Herman, Cila↗

NASA NTRS2003

A Nonlinear Model for Fuel Atomization in Spray Combustion

Most gas turbine combustion codes rely on ad-hoc statistical assumptions regarding the outcome of fuel atomization processes. The modeling effort proposed in this project is aimed at developing a realistic model to produce accurate predictions of fuel atomization parameters. The model involves application of the nonlinear stability theory to analyze the instability and subsequent disintegration of the liquid fuel sheet that is produced by fuel injection nozzles in gas turbine combustors. The fuel sheet is atomized into a multiplicity of small drops of large surface area to volume ratio to enhance the evaporation rate and combustion performance. The proposed model will effect predictions of fuel sheet atomization parameters such as drop size, velocity, and orientation as well as sheet penetration depth, breakup time and thickness. These parameters are essential for combustion simulation codes to perform a controlled and optimized design of gas turbine fuel injectors. Optimizing fuel injection processes is crucial to improving combustion efficiency and hence reducing fuel consumption and pollutants emissions.

Liu, Nan-Suey↗

NASA NTRS2003

A Matlab-Based Graphical User Interface for Simulation and Control Design of a Hydrogen Mixer

A Graphical User Interface (GUI) that facilitates prediction and control design tasks for a propellant mixer is described. The Hydrogen mixer is used in rocket test stand operations at the NASA John C. Stennis Space Center. The mixer injects gaseous hydrogen (GH2) into a stream of liquid hydrogen (LH2) to obtain a combined flow with desired thermodynamic properties. The flows of GH2 and LH2 into the mixer are regulated by two control valves, and a third control valve is installed at the exit of the mixer to regulate the combined flow. The three valves may be simultaneously operated in order to achieve any desired combination of total flow, exit temperature and mixer pressure within the range of operation. The mixer, thus, constitutes a three-input, three-output system. A mathematical model of the mixer has been obtained and validated with experimental data. The GUI presented here uses the model to predict mixer response under diverse conditions.

Richter, Hanz↗

NASA NTRS2004

Preform Characterization in VARTM Process Model Development

Vacuum-Assisted Resin Transfer Molding (VARTM) is a Liquid Composite Molding (LCM) process where both resin injection and fiber compaction are achieved under pressures of 101.3 kPa or less. Originally developed over a decade ago for marine composite fabrication, VARTM is now considered a viable process for the fabrication of aerospace composites (1,2). In order to optimize and further improve the process, a finite element analysis (FEA) process model is being developed to include the coupled phenomenon of resin flow, preform compaction and resin cure. The model input parameters are obtained from resin and fiber-preform characterization tests. In this study, the compaction behavior and the Darcy permeability of a commercially available carbon fabric are characterized. The resulting empirical model equations are input to the 3- Dimensional Infiltration, version 5 (3DINFILv.5) process model to simulate infiltration of a composite panel.

Grimsley, Brian W.↗