Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Critical Fluids”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied.

Naumann, R. J.↗
NASA NTRS2011

The Effect of Predicted Vehicle Displacement on Ground Crew Task Performance and Hardware Design

NASA continues to explore new launch vehicle concepts that will carry astronauts to low- Earth orbit to replace the soon-to-be retired Space Transportation System (STS) shuttle. A tall vertically stacked launch vehicle (> or =300 ft) is exposed to the natural environment while positioned on the launch pad. Varying directional winds and vortex shedding cause the vehicle to sway in an oscillating motion. Ground crews working high on the tower and inside the vehicle during launch preparations will be subjected to this motion while conducting critical closeout tasks such as mating fluid and electrical connectors and carrying heavy objects. NASA has not experienced performing these tasks in such environments since the Saturn V, which was serviced from a movable (but rigid) service structure; commercial launchers are likewise attended by a service structure that moves away from the vehicle for launch. There is concern that vehicle displacement may hinder ground crew operations, impact the ground system designs, and ultimately affect launch availability. The vehicle sway assessment objective is to replicate predicted frequencies and displacements of these tall vehicles, examine typical ground crew tasks, and provide insight into potential vehicle design considerations and ground crew performance guidelines. This paper outlines the methodology, configurations, and motion testing performed while conducting the vehicle displacement assessment that will be used as a Technical Memorandum for future vertically stacked vehicle designs.

Atencio, Laura Ashley↗
NASA NTRS2012

Current CFD Practices in Launch Vehicle Applications

The quest for sustained space exploration will require the development of advanced launch vehicles, and efficient and reliable operating systems. Development of launch vehicles via test-fail-fix approach is very expensive and time consuming. For decision making, modeling and simulation (M&S) has played increasingly important roles in many aspects of launch vehicle development. It is therefore essential to develop and maintain most advanced M&S capability. More specifically computational fluid dynamics (CFD) has been providing critical data for developing launch vehicles complementing expensive testing. During the past three decades CFD capability has increased remarkably along with advances in computer hardware and computing technology. However, most of the fundamental CFD capability in launch vehicle applications is derived from the past advances. Specific gaps in the solution procedures are being filled primarily through "piggy backed" efforts.on various projects while solving today's problems. Therefore, some of the advanced capabilities are not readily available for various new tasks, and mission-support problems are often analyzed using ad hoc approaches. The current report is intended to present our view on state-of-the-art (SOA) in CFD and its shortcomings in support of space transport vehicle development. Best practices in solving current issues will be discussed using examples from ascending launch vehicles. Some of the pacing will be discussed in conjunction with these examples.

Kwak, Dochan↗
NASA NTRS2013

Microgravity Fluids for Biology, Workshop

Microgravity Fluids for Biology represents an intersection of biology and fluid physics that present exciting research challenges to the Space Life and Physical Sciences Division. Solving and managing the transport processes and fluid mechanics in physiological and biological systems and processes are essential for future space exploration and colonization of space by humans. Adequate understanding of the underlying fluid physics and transport mechanisms will provide new, necessary insights and technologies for analyzing and designing biological systems critical to NASAs mission. To enable this mission, the fluid physics discipline needs to work to enhance the understanding of the influence of gravity on the scales and types of fluids (i.e., non-Newtonian) important to biology and life sciences. In turn, biomimetic, bio-inspired and synthetic biology applications based on physiology and biology can enrich the fluid mechanics and transport phenomena capabilities of the microgravity fluid physics community.

biology↗
NASA NTRS1986

Onset of surface-tension-driven Benard convection

An experimental investigation of the onset of convection in shallow fluid layers heated uniformly from below and cooled from above by an air layer has been made. If the depth of the silicone layer is smaller than 2 mm the onset of convection takes place in two stages. There is first a weak pattern, which is characterized by its appearance at ever smaller temperature gradients as the depth of the fluid is decreased. When the temperature difference across the fluid is increased a second strong pattern forms near the predicted critical Marangoni number. The cells in this pattern are hexagonal and seem to be what one has always referred to as Benard cells. The temperature gradient at which this pattern appears increases with decreased depth. The heat transfer through the fluid has been measured. The critical temperature gradient for the formation of the hexagonal pattern has been determined from the break of the heat transfer curve.

Koschmieder, E. L.↗
NASA NTRS1989

Experimental investigation of convective stability in a superposed fluid and porous layer when heated from below

Experiments have been carried out in a horizontal superposed fluid and porous layer contained in a test box 24 cm x 12 cm x 4 cm high. The porous layer consisted of 3 mm diameter glass beads, and the fluids used were water, 60 and 90 percent glycerin-water solutions, and 100 percent glycerin. The depth ratio d, which is the ratio of the thickness of the fluid layer to that of the porous layer, varied from 0 to 1.0. Fluids of increasingly higher viscosity were used for cases with larger d in order to keep the temperature difference across the tank within reasonable limits. The size of the convection cells was inferred from temperature measurements made with embedded thermocouples and from temperature distributions at the top of the layer by use of liquid crystal film. The experimental results showed: (1) a precipitous decrease in the critical Rayleigh number as the depth of the fluid layer was increased from zero, and (2) an eightfold decrease in the critical wavelength between d = 0.1 and 0.2. Both of these results were predicted by the linear stability theory reported earlier (Chen and Chen, 1988).

Chen, Falin↗
NASA NTRS2003

Measurement of the Specific Heat Using a Gravity Cancellation Approach

The specific heat at constant volume C(sob V) of a simple fluid diverges near its liquid-vapor critical point. However, gravity-induced density stratification due to the divergence of isothermal susceptibility hinders the direct comparison of the experimental data with the predictions of renormalization group theory. In the past, a microgravity environment has been considered essential to eliminate the density stratification. We propose to perform specific heat measurements of He-3 on the ground using a method to cancel the density stratification. A He-3 fluid layer will be heated from below, using the thermal expansion of the fluid to cancel the hydrostatic compression. A 6% density stratification at a reduced temperature of 10(exp -5) can be cancelled to better than 0.1% with a steady 1.7 micro K temperature difference across a 0.05 cm thick fluid layer. A conventional AC calorimetry technique will be used to determine the heat capacity. The minimized bulk density stratification with a relaxation time 6500 sec at a reduced temperature of 10(exp -5) will stay unchanged during 1 Hz AC heating. The smear of the specific heat divergence due to the temperature difference across the cell is about 0.1% at a reduced temperature of 10(exp -6). The combination of using High Resolution Thermometry with a 0.5 n K temperature resolution in the AC technique and the cancellation of the density stratification will enable C(sub V) to be measured down to a reduced temperature of 10(exp -6) with less than a 1% systematic error.

Zhong, Fang↗
NASA NTRS2025

Simulations of Large-Scale Zero Boiloff, Densification, and Solidification of Hydrogen

An Integrated Refrigeration and Storage (IRAS) experimental system called the Ground Operations and Demonstration Unit for Liquid Hydrogen (GODU-LH2) demonstrated the ability store cryogens in a zero boiloff (ZBO) process, and to densify liquid hydrogen by reducing the temperature and pressure down to the triple point resulting in solidification. The incompressible Navier-Stokes was utilized to simulate ZBO, densification, and solidification of liquid hydrogen (LH2) in the IRAS tank. The simulations were performed using a commercially available Computational Fluid Dynamics (CFD) pressure-based mass and momentum flow model and an enthalpy-porosity energy model. Results demonstrated the simulation’s ability to predict time-dependent flow and temperature fields and solid-liquid phase locations for hydrogen during ZBO, densification, and solidification. The simulations showed good agreement with experimental data, with errors within acceptable ranges for temperature and pressure predictions, provided detailed insights into natural convection and solid-liquid phase change dynamics. These findings are critical for the design of future cryogenic fluid management systems.

Computational Fluid Dynamics↗
NASA NTRS1989

Tank Pressure Control Experiment on the Space Shuttle

The tank pressure control experiment is a demonstration of NASA intent to develop new technology for low-gravity management of the cryogenic fluids that will be required for future space systems. The experiment will use freon as the test fluid to measure the effects of jet-induced fluid mixing on storage tank pressure and will produce data on low-gravity mixing processes critical to the design of on-orbit cryogenic storage and resupply systems. Basic data on fluid motion and thermodynamics in low gravity is limited, but such data is critical to the development of space transfer vehicles and spacecraft resupply facilities. An in-space experiment is needed to obtain reliable data on fluid mixing and pressure control because none of the available microgravity test facilities provide a low enough gravity level for a sufficient duration to duplicate in-space flow patterns and thermal processes. Normal gravity tests do not represent the fluid behavior properly; drop-tower tests are limited in length of time available; aircraft low-gravity tests cannot provide the steady near-zero gravity level and long duration needed to study the subtle processes expected in space.

Source record↗
NASA NTRS1974

Hydrostatics and steady dynamics of spatially varying electromechanical flow structures

The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch-in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point-by-point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.

Jones, T. B.↗
NASA NTRSDate not supplied

Cryogenic Fluid Management for the Artemis Program and Beyond

NASA is endeavoring on an ambitious return to the Moon and eventually on to Mars through the Artemis Program leveraging innovative technologies to establish sustainable exploration architectures collaborating with US commercial and international partners [1]. Future NASA architectures have baselined cryogenic propulsion systems to support lunar missions and ultimately future missions to Mars. NASA has been investing in maturing CFM active and passive storage, transfer, and gauging technologies over the last decade plus primarily focused on ground development with a few small-scale microgravity fluid experiments. Recently, NASA created a Cryogenic Fluid Management (CFM) Technology Roadmap identifying the critical gaps requiring further development to reach a technology readiness level (TRL) of 6 prior to infusion to flight applications. To address the technology gaps the Space Technology Mission Directorate (STMD) strategically plans to invest in a diversified CFM portfolio approach through ground and flight demonstrations, collaborating with international partners, and leveraging Public Private Partnerships (PPPs) opportunities with US industry through the Tipping Point and Announcement of Collaborative Opportunities (ACO) solicitations. Once proven, these system capabilities will enable the high performing cryogenic propellant systems needed for the Artemis Program and beyond.

Cryogenic Fluid Management↗
NASA NTRSDate not supplied

Cryogenic Fluid Management Technologies Enabling for the Artemis Program and Beyond

NASA is endeavoring on an ambitious return to the Moon and eventually on to Mars through the Artemis Program leveraging innovative technologies to establish sustainable exploration architectures collaborating with US commercial and international partners[1]. Future NASA architectures have baselined cryogenic propulsion systems to support lunar missions and ultimately future missions to Mars. NASA has been investing in maturing CFM active and passive storage, transfer, and gauging technologies over the last decade plus primarily focused on ground development with a few small-scale microgravity fluid experiments. Recently, NASA created a Cryogenic Fluid Management (CFM)Technology Roadmap identifying the critical gaps requiring further development to reach a technology readiness level (TRL) of 6 prior to infusion to flight applications. To address the technology gaps the Space Technology Mission Directorate(STMD)strategically plans to invest in a diversified CFM portfolio approach through ground and flight demonstrations ,collaborating with international partners, and leveraging Public Private Partnerships (PPPs) opportunities with US industry through the Tipping Point and Announcement of Collaborative Opportunities (ACO) solicitations. Once proven, these system capabilities will enable the high performing cryogenic propellant systems needed for the Artemis Program and beyond.

Cryogenic Fluid Management↗
NASA NTRS1977

A reexamination of two-fluid solar wind models

The two-fluid solar-wind equations have been solved by a method which is approximately 50 times faster than any previously developed, through the use of asymptotic expansions which are self-consistently iterated upon to find a solution that passes through the critical point. The energy assumptions in two-fluid solar-wind models are reexamined, and the conclusions are as follows: (1) proton thermal conduction may not be neglected, (2) the Coulomb logarithm must be calculated as a function of radius, and (3) the electron and proton temperatures at the base need not be equal, even when the time scale for energy exchange between the species is an order of magnitude smaller than the expansion time at the base. It is possible to reproduce reasonable quiet-time solar-wind parameters at 1 AU, but only if the proton temperature is approximately twice the electron temperature at 1 solar radius. This may indicate that extended proton heating is important in the outer solar corona. Winds with velocities at 1 AU of 450 km/s are generated without nonthermal energy deposition but require high proton temperatures as well as very low densities at the base. Higher-velocity solutions are not possible in a spherically symmetric geometry for reasonable particle fluxes at 1 AU, and it is suggested that these higher-velocity states probably require additional heating, acceleration mechanisms, or nonradial flow.

Nerney, S.↗
NASA NTRS2010

Computational Analyses of Pressurization in Cryogenic Tanks

A comprehensive numerical framework utilizing multi-element unstructured CFD and rigorous real fluid property routines has been developed to carry out analyses of propellant tank and delivery systems at NASA SSC. Traditionally CFD modeling of pressurization and mixing in cryogenic tanks has been difficult primarily because the fluids in the tank co-exist in different sub-critical and supercritical states with largely varying properties that have to be accurately accounted for in order to predict the correct mixing and phase change between the ullage and the propellant. For example, during tank pressurization under some circumstances, rapid mixing of relatively warm pressurant gas with cryogenic propellant can lead to rapid densification of the gas and loss of pressure in the tank. This phenomenon can cause serious problems during testing because of the resulting decrease in propellant flow rate. With proper physical models implemented, CFD can model the coupling between the propellant and pressurant including heat transfer and phase change effects and accurately capture the complex physics in the evolving flowfields. This holds the promise of allowing the specification of operational conditions and procedures that could minimize the undesirable mixing and heat transfer inherent in propellant tank operation. In our modeling framework, we incorporated two different approaches to real fluids modeling: (a) the first approach is based on the HBMS model developed by Hirschfelder, Beuler, McGee and Sutton and (b) the second approach is based on a cubic equation of state developed by Soave, Redlich and Kwong (SRK). Both approaches cover fluid properties and property variation spanning sub-critical gas and liquid states as well as the supercritical states. Both models were rigorously tested and properties for common fluids such as oxygen, nitrogen, hydrogen etc were compared against NIST data in both the sub-critical as well as supercritical regimes.

Ahuja, Vineet↗
NASA NTRS1987

Straight cylindrical seal for high-performance turbomachines

A straight cylindrical seal configuration representing the seal for a high-performance turbopump (e.g., the space shuttle main engine fuel pump) was tested under static (nonrotating) conditions. The test data included critical mass flux and pressure profiles over a wide range of inlet temperatures and pressures for fluid nitrogen and fluid hydrogen with the seal in concentric and fully eccentric positions. The critical mass fluxes (or leakage rates) for the concentric and fully eccentric configurations were nearly the same when based on stagnation conditions upstream of the seal. The fully eccentric configuration pressure profiles of the gas and liquid were different. Further, the pressure differences between the maximum and the minimum clearance positions were highly dependent on the geometric conditions, the temperature, and the absolute pressure at both the inlet and the exit. The pressure differences were greatest in the inlet region. The results, although complex, tend to follow the corresponding-states principles for critical flows. Gaseous injection near the seal exit plane significantly altered the pressure profiles and could be used to control turbomachine instabilities.

Hendricks, Robert C.↗
NASA NTRS1987

Three-step cylindrical seal for high-performance turbomachines

A three-step cylindrical seal configuration representing the seal for a high performance turbopump (e.g., the space shuttle main engine fuel pump) was tested under static (nonrotating) conditions. The test data included critical mass flux and pressure profiles over a wide range of inlet temperatures and pressures for fluid nitrogen and fluid hydrogen with the seal in concentric and fully eccentric positions. The critical mass flux (leakage rate) was 70% that of an equivalent straight cylindrical seal with a correspondingly higher pressure drop based on the same flow areas of 0.3569 sq cm but 85% that of the straight seal based on the third-step flow area of 0.3044 sq cm. The mass flow rates for the three step cylindrical seal in the fully eccentric and concentric positions were essentially the same, and the trends in flow coefficient followed those of a simple axisymmetric inlet configuration. However, for inlet stagnation temperatures less than the thermodynamic critical temperature the pressure profiles exhibited a flat region throughout the third step of the seal, with the pressure magnitude dependent on the inlet stagnation temperature. Such profiles represent an extreme positive direct stiffness. These conditions engendered a crossover in the pressure profile upstream of the postulated choke that resulted in a local negative stiffness. Flat and crossover profiles resulting from choking within the seal are practically unknown to the seal designer. However, they are of critical importance to turbomachine stability and must be integrated into any dynamic analysis of a seal of this configuration. In addition, choking is highly dependent on geometry, inlet-to-backpressure ratio, and inlet temperature and can occur within the seal even though the backpressure is above the critical pressure.

Hendricks, Robert C.↗
NASA NTRS1988

Fluid inclusions in Martian samples: Clues to early crustal development and the hydrosphere

Major questions about Mars that could be illuminated by examining fluid inclusions in Martian samples include: (1) the nature, extent and timing of development (and decline) of the hydrosphere that existed on the planet; and (2) the evolution of the crust. Fluid inclusion analyses of appropriate samples could provide critical data to use in comparison with data derived from analogous terrestrial studies. For this study, sample handling and return restrictions are unlikely to be as restrictive as the needs of other investigators. The main constraint is that the samples not be subjected to excessively high temperatures. An aqueous fluid inclusion trapped at elevated pressure and temperature will commonly consist of liquid water and water vapor at room temperature. Heating (such as is done in the laboratory to fix P-V-T data for the inclusion) results in moderate pressure increases up to the liquid-vapor homogenization temperature followed by a sharp increase in pressure with continued heating because the inclusion is effectively a fixed volume system. This increased pressure can rupture the inclusion; precise limits are dependent on size, shape, and composition as well as the host material.

Brown, Philip E.↗