Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Pressurization”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

High Pressure Hydrogen Pressure Relief Devices: Accelerated Life Testing and Application Best Practices

Pressure relief devices (PRDs ) are used to protect high pressure systems from burst failure caused by overpressurization. Codes and standards require the use of PRDs for the safe design of many pressurized systems. These systems require high reliability due to the risks associated with a burst failure. Hydrogen service can increase the risk of PRD failure due to material property degradation caused by hydrogen attack. The National Renewable Energy Laboratory (NREL) has conducted an accelerated life test on a conventional spring loaded PRD. Based on previous failures in the field, the nozzles specific to these PRDs are of particular interest. A nozzle in a PRD is a small part that directs the flow of fluid toward the sealing surface to maintain the open state of the valve once the spring force is overcome. The nozzle in this specific PRD is subjected to the full tensile force of the fluid pressure. These nozzles are made from 440C material, which is a type of hardened steel that is commonly chosen for high pressure applications because of its high strength properties. In a hydrogen environment, however, 440C is considered a worst case material since hydrogen attack results in a loss of almost all ductility and thus 440C is prone to fatigue and material failure. Accordingly, 440C is not recommended for hydrogen service. Conducting an accelerated life test on a PRD with 440C material provides information on necessary and sufficient conditions required to produce crack initiation and failure. The accelerated life test also provides information on other PRD failure modes that are somewhat statistically random in nature.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

A Model to Account for the Effects of Load Ratio and Hydrogen Pressure on the Fatigue Crack Growth Behavior of Pressure Vessel Steels

A phenomenological model for estimating the effects of load ratio R and hydrogen pressure P H2 on the hydrogen-assisted fatigue crack growth rate (HA–FCGR) behavior in the transient and steady-state regimes of pressure vessel steels is described. The “transient regime” is identified with crack growth within a severely embrittled zone of intense plasticity at the crack tip. The “steady-state” behavior is associated with the crack growing into a region of comparatively lower hydrogen concentration located further away from the crack tip. The model treats the effects of R and P H2 as being functionally separable. In the transient regime, the effects of the hydrogen pressure on the HA–FCGR behavior were negligible but were significant in the steady-state regime. The hydrogen concentration in the steady-state region is modeled as being dependent on the kinetics of lattice diffusion, which is sensitive to pressure. Experimental HA–FCGR data from the literature were used to validate the model. The new model was shown to be valid over a wide range of conditions that ranged between –1 ≤ R ≤ 0.8 and 0.02 ≤ P H2 ≤ 103 MPa for pressure vessel steels.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Spectral Analysis of Integrated Pressures on Patches with Unsteady Pressure-Sensitive Paint Measurements

This paper describes the spectral analysis of integrated pressures on patches of the scale model of the Space Launch System Block 1 cargo vehicle with the Unsteady Pressure-Sensitive Paint measurements, which were collected in the ascent transient aerodynamics test with the Unitary Plan Wind Tunnel 11-by-11-foot Transonic Wind Tunnel in September 2019 at NASA Ames Research Center. The patches are defined with x station values, indicating the position along length of the vehicle, and azimuth angles of the scale model. For each patch, the polygons are determined from the surface cells of the grid of the model, clipped with the edges of the patch, and each of the polygons is divided into triangles. The integrated pressure of the patch is determined as the ratio of the sum of the forces on the triangles over the sum of the areas of the triangles. For each run of the test, the cross power spectral density and magnitude squared coherence are computed from the time series of the integrated pressures on the patches. The results of pressure integration and spectral analysis are presented, and the data consistency of the test is demonstrated. The work described in this paper is a part of NASA’s development of a new state-of-the-art uPSP capability in production wind tunnels. Funding for this research was provided by the NASA Aeroscience Evaluation and Test Capabilities Project.

Pressure-Sensitive Paint↗
NASA NTRSDate not supplied

Methodology for Validation of Unsteady Pressure-Sensitive Paint Measurements using Pressure Transducers

Unsteady Pressure-Sensitive Paint (uPSP) technology provides simultaneously high-frequency and high-spatial resolution surface pressure fluctuation measurements. It has demonstrated value in wind tunnel test facilities to evaluate aerospace vehicle unsteady aerodynamics. The calibration of measurements from digital pixel counts into corresponding physical units relies on both lab-based and in-situ calibration steps, and its validation is both challenging and critical to adoption of the technology. We present a rigorous methodology for direct comparison of uPSP-derived surface pressure measurements to reference pressure transducer data based on a model of the camera-based measurement error, a model of the flow field pressure signal, and their propagation through the uPSP data reduction algorithm. The methodology is demonstrated on data collected in a small-scale, subsonic wind tunnel test as well as data collected from a Space Launch System unsteady aerodynamics characterization test at the NASA Ames Research Center Unitary Plan Wind Tunnel Complex.

Pressure-Sensitive Paint↗
NASA NTRSDate not supplied

Degradation Characterization of Unsteady Pressure-Sensitive Paint Under Various Pressures

The lifetime and intensity techniques are two distinct methods used to measure the surface pressure of wind tunnel models with pressure-sensitive paint (PSP). When exposed to 405 nm light for extended periods, both the luminescence and the lifetime ratio were observed to decrease, affecting perceived pressure values. To help further the implementation of the uPSP, this paper describes the efforts to characterize the degradation of both the intensity of the paint and its lifetime ratio, as well as the change in intensity calibration. It was found that the paint degrades at different rates depending on the partial pressure of oxygen during excitation. It was also found that the calibration curves exhibit greater changes when under higher oxygen concentrations, both indicating photodegradation due to photodecomposition and photo-oxidation processes. These effects are observed on models in a subsonic 14” × 14” wind tunnel. The work provides insight into the dynamic degradation behavior of PSP and uPSP, paving the way to reduce the error in pressure measurements obtained through these techniques.

Pressure-Sensitive Paint↗
DOE OSTI2022

High-pressure structural systematics of dysprosium metal compressed in a neon pressure medium to 182 GPa

Here we present an experimental and theoretical study of dysprosium metal compressed in the soft pressure transmitting medium Ne up to 182 and 300 GPa, respectively. Angle-dispersive x-ray powder diffraction data from each of the high-pressure polymorphs shows anisotropic compression behavior indicating changes to the electron density distribution throughout its polymorphic landscape. We compare the monoclinic (mC4) and orthorhombic (oF16) structures for the collapsed structure for Dy above 82 GPa and verify that the oF16 structure offers a better fit to our data than the previously reported mC4 structure. Further, we have found that the oF16 structure undergoes similar anisotropic compression of its lattice parameters, with a turning point above 160 GPa; suggesting a potential phase transition at pressures much higher than achieved in this study. Density functional theory calculations show the likely candidate for this new high-pressure phase is the isosymmetric oF8 structure, which is predicted to be lower in energy than the oF16 structure above 275 GPa.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Structural and Electronic Transitions in Liquid FeO Under High Pressure

Abstract FeO represents an important end‐member for planetary interiors mineralogy. However, its properties in the liquid state under high pressure are poorly constrained. Here, in situ high‐pressure and high‐temperature X‐ray diffraction experiments, ab initio simulations, and thermodynamic calculations are combined to study the local structure and density evolution of liquid FeO under extreme conditions. Our results highlight a strong shortening of the Fe‐Fe distance, particularly pronounced between ambient pressure and ∼40 GPa, possibly related with the insulator to metal transition occurring in solid FeO over a similar pressure range. Liquid density is smoothly evolving between 60 and 150 GPa from values calculated for magnetic liquid to those calculated for non‐magnetic liquid, compatibly with a continuous spin crossover in liquid FeO. The present findings support the potential decorrelation between insulator/metal transition and the high‐spin to low‐spin continuous transition, and relate the changes in the microscopic structure with macroscopic properties, such as the closure of the Fe‐FeO miscibility gap. Finally, these results are used to construct a parameterized thermal equation of state for liquid FeO providing densities up to pressure and temperature conditions expected at the Earth's core‐mantle boundary.

Morard, Guillaume↗
DOE OSTI2018

Single crystal toroidal diamond anvils for high pressure experiments beyond 5 megabar

Static compression experiments over 4 Mbar are rare, yet critical for developing accurate fundamental physics and chemistry models, relevant to a range of topics including modeling planetary interiors. Here we show that focused ion beam crafted toroidal single-crystal diamond anvils with ~9.0 μm culets are capable of producing pressures over 5 Mbar. The toroidal surface prevents gasket outflow and provides a means to stabilize the central culet. We have reached a maximum pressure of ~6.15 Mbar using Re as in situ pressure marker, a pressure regime typically accessed only by double-stage diamond anvils and dynamic compression platforms. In conclusion, optimizing single-crystal diamond anvil design is key for extending the pressure range over which studies can be performed in the diamond anvil cell.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Phase transition induced strain in ZnO under high pressure

Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. Ultimately, these findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Pressure-induced densification in GeO{sub 2} glass: A transmission x-ray microscopy study

Nanoscale transmission x-ray microscopy measurements have been performed to determine the effect of pressure (P) on the volume (V) change in GeO{sub 2} glass up to 38.5 GPa. The P-V data show a continuous increase upon compression, indicating that the density-driven structural transformation is a gradual process. Over the pressure range studied, a transition is observed at approximately 10–13 GPa, where the material displays distinct compression behaviors. The pressure-induced densification that involves the coordination number change has been discussed. Using this newly developed high-pressure imaging technique with tens of nanometer resolution, we have provided a direct and unequivocal way for measuring density of amorphous materials to much higher pressures with accuracy rivaling x-ray diffraction of crystalline solids.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗