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At least 595 records · Page 33

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Devices and methods for separating components

A method, system, and device for separating components is described. A vessel is provided. A first volume of a process liquid, containing a first component and a second component, is passed into an inner chamber. The piston retracts to a first position. The fluid inlet is closed. The piston is retracted to a second position, causing the first component and a first portion of the second component to flash to form a vapor stream while a second portion of the second component freezes to form a solid product stream. The fluid outlet is then opened. The piston is advanced to a third position that results in a third volume, smaller than the first volume, such that the vapor stream is expelled. The fluid outlet is closed. The piston is fully closed such that the solid product stream is pressed into and extruded through the solids outlet.

Baxter, Larry↗

DOE OSTI2018

Integral Model of Noise of an Engine-Propeller Power Plant

A semiempirical model is proposed for estimation of the noise levels produced by aircraft piston power plants in the far acoustic field, which takes account of the main sources of noise. The acoustic field is considered as a superposition of fields formed by the radiations from a propeller and a piston engine. For calculation estimation of the levels of tonal noise of the propeller, it is proposed that a semiempirical method developed by the authors earlier be used. To determine the levels of vortex propeller noise which is presumably dominant in the broad-band noise of tractor propellers, it is proposed that one analytical model of trailing-edge noise be used. An empirical model of noise is proposed for calculation of the acoustic characteristics of a piston engine. Good agreement is shown between calculated and experimental data on the noise of power plants with tractor propellers. The data have been derived in acoustic testing of light aircraft of the An-2, Yak-18T, MAI-223M, and F30 type under static conditions at the aviabase of the Moscow Aviation Institute. Lines of further research are formulated for improvement of this procedure and expansion of the field of its application.

42 ENGINEERING↗

DOE OSTI2026

Dynamic modeling of near isothermal compressor for Transcritical carbon dioxide cycle to support efficiency improvement

Compressors are the primary components of energy consumption in vapor compression systems, drawing considerable research effort to reduce carbon emissions and improve energy efficiency. This work presents an isothermal compressor that integrates the compression chamber with the gas cooler to achieve near-isothermal compression, resulting in up to 30% energy reduction compared to traditional isentropic compression, according to the experiment results. A detailed dynamic model for the isothermal compression cycle of carbon dioxide (CO 2 ) is first presented, coupled with a liquid-piston model for chamber design. The model is experimentally validated on a 3.5 kW prototype, yielding a 6.2% relative error in chamber pressure and a 0.5 K deviation in chamber temperature. The liquid piston exhibits reduced frictional heating and geometric adaptability relative to the mechanical piston. Leveraging these attributes, the study further evaluates approaches that enhance the heat transfer to achieve isothermal compression by increasing the effective heat transfer area during compression. As a result, simulations demonstrated up to a 5% improvement in the coefficient of performance over the baseline case through chamber design, providing guidelines for design of isothermal compression cycle.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2012

Effects of Gasoline Direct Injection Engine Operating Parameters on Particle Number Emissions

A single-cylinder, wall-guided, spark ignition direct injection engine was used to study the impact of engine operating parameters on engine-out particle number (PN) emissions. Experiments were conducted with certification gasoline and a splash blend of 20% fuel grade ethanol in gasoline (E20), at four steady-state engine operating conditions. Independent engine control parameter sweeps were conducted including start of injection, injection pressure, spark timing, exhaust cam phasing, intake cam phasing, and air-fuel ratio. The results show that fuel injection timing is the dominant factor impacting PN emissions from this wall-guided gasoline direct injection engine. The major factor causing high PN emissions is fuel liquid impingement on the piston bowl. By avoiding fuel impingement, more than an order of magnitude reduction in PN emission was observed. Increasing fuel injection pressure reduces PN emissions because of smaller fuel droplet size and faster fuel-air mixing. PN emissions are insensitive to cam phasing and spark timing, especially at high engine load. Cold engine conditions produce higher PN emissions than hot engine conditions due to slower fuel vaporization and thus less fuel-air homogeneity during the combustion process. E20 produces lower PN emissions at low and medium loads if fuel liquid impingement on piston bowl is avoided. At high load or if there is fuel liquid impingement on piston bowl and/or cylinder wall, E20 tends to produce higher PN emissions. This is probably a function of the higher heat of vaporization of ethanol, which slows the vaporization of other fuel components from surfaces and may create local fuel-rich combustion or even pool-fires.

02 PETROLEUM↗

DOE OSTI2014

Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2015

Acoustic non-diffracting Airy beam

The acoustic non-diffracting Airy beam as its optical counterpart has unique features of self-bending and self-healing. The complexity of most current designs handicaps its applications. A simple design of an acoustic source capable of generating multi-frequency and broad-band acoustic Airy beam has been theoretically demonstrated by numerical simulations. In the design, a piston transducer is corrugated to induce spatial phase variation for transducing the Airy function. The piston's surface is grooved in a pattern that the width of each groove corresponds to the half wavelength of Airy function. The resulted frequency characteristics and its dependence on the size of the piston source are also discussed. This simple design may promote the wide applications of acoustic Airy beam particularly in the field of medical ultrasound.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

A gas-dynamical approach to radiation pressure acceleration

The study of high intensity ion beams driven by high power pulsed lasers is an active field of research. Of particular interest is the radiation pressure acceleration, for which simulations predict narrow band ion energies up to GeV. We derive a laser-piston model by applying techniques for non-relativistic gas-dynamics. The model reveals a laser intensity limit, below which sufficient laser-piston acceleration is impossible. The relation between target thickness and piston velocity as a function of the laser pulse length yields an approximation for the permissible target thickness. We performed one-dimensional Particle-In-Cell simulations to confirm the predictions of the analytical model. These simulations also reveal the importance of electromagnetic energy transport. We find that this energy transport limits the achievable compression and rarefies the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

A novel method for correction of temporally- and spatially-variant optical distortion in planar particle image velocimetry

In-cylinder flow measurements are necessary to gain a fundamental understanding of swirl-supported, light-duty Diesel engine processes for high thermal efficiency and low emissions. Planar particle image velocimetry (PIV) can be used for non-intrusive, in situ measurement of swirl-plane velocity fields through a transparent piston. In order to keep the flow unchanged from all-metal engine operation, the geometry of the transparent piston must adapt the production-intent metal piston geometry. As a result, a temporally- and spatially-variant optical distortion is introduced to the particle images. Here, to ensure reliable measurement of particle displacements, this work documents a systematic exploration of optical distortion quantification and a hybrid back-projection procedure that combines ray-tracing-based geometric and in situ manual back-projection approaches.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2016

Analytical Solution to the Pneumatic Transient Rod System at ACRR

The ACRR pulse is pneumatically driven by nitrogen in a system of pipes, valves and hoses up to the connection of the pneumatic system and mechanical linkages of the transient rod (TR). The main components of the TR pneumatic system are the regulator, accumulator, solenoid valve and piston-cylinder assembly. The purpose of this analysis is to analyze the flow of nitrogen through the TR pneumatic system in order to develop a motion profile of the piston during the pulse and be able to predict the pressure distributions inside both the cylinder and accumulators. The predicted pressure distributions will be validated against pressure transducer data, while the motion profile will be compared to proximity switch data. By predicting the motion of the piston, pulse timing will be determined and provided to the engineers/operators for verification. The motion profile will provide an acceleration distribution to be used in Razorback to more accurately predict reactivity insertion into the system.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2017

Near-isothermal-isobaric compressed gas energy storage

In this paper, the effectiveness of storing energy by compressing and expanding a condensable gas is evaluated. A high efficiency energy storage system, which stores energy by compressing/expanding gas (air) using a liquid (water) piston has been recently introduced and extensively studied. With the use of the liquid piston, the inefficient gas turbomachines used in conventional gas compression/expansion systems are replaced with high efficiency hydraulic machines. Utilizing heat transfer techniques and replacing the non-condensable air with a condensable gas (i.e. CO 2 , synthetic refrigerants, hydrocarbon refrigerants, etc.) have been proposed as methods to improve energy density and roundtrip efficiency of such systems, leading to near isothermal and near isobaric charge/discharge processes. In order to investigate the effectiveness of the proposed concept, a miniature lab-scale experimental setup was designed and built to investigate the compression/expansion characteristics and energy storage efficiency of a system utilizing R134a as the energy storage (primary) working fluid, and mineral refrigerant oil as the liquid piston (secondary) working fluid. Several tests are carried out to quantify energy storage efficiency and energy density. It is found that improving heat transfer rates from/into the storage fluid results in increased efficiency and energy density. A heat-transfer enhancement strategy to achieve near isothermal, isobaric expansion and compression is proposed and investigated experimentally. Some results are generalized and presented in non-dimensional form which can be applied to describe and/or design scaled-up systems. Lastly, a potential working fluid for a scaled-up system is discussed.

25 ENERGY STORAGE↗

DOE OSTI2022

HIDRA-MAT liquid metal droplet injector for liquid metal applications in HIDRA

A liquid metal droplet injector was explicitly designed for the Hybrid Illinois Device for Research and Applications Material Analysis Test-stand (HIDRA-MAT) at the University of Illinois Urbana-Champaign to prepare liquid metal plasma-facing components (PFCs) for plasma exposure. The design goals were to create a compact, reliable, and robust design that could apply liquid metal droplets in-vacuo to a variety of samples. The injector was designed for liquid metal use, and results discussed pertain to lithium. The injector can produce lithium droplets of consistent size by utilizing programmable piston movement. Here, droplet formation data is presented for four different piston step sizes (0.125 mm, 0.25 mm, 0.5 mm, and 1 mm) at three different nozzle temperatures (185 °C, 230 °C, and 270 °C). Droplets are formed on the injector nozzle tip and a linear shift mechanism vertically translates the droplet to the substrate for application. This design prevents the droplet from inadvertently detaching off the nozzle and falling to the sample. Application of the liquid metal droplet ensures placement consistency on the substrate and helps avoid damage to components in HIDRA-MAT that should not interact with liquid metals. A description of the liquid lithium droplet creation and application results is given and provides additional insight into the cooling and oxidation of lithium droplets under vacuum conditions. A second nozzle was fabricated and demonstrated repeatability in droplet diameter creation having a variance of ±0.14 mm for droplets created from the same number of piston steps. The end-use for the injector on HIDRA-MAT is to apply liquid metals to PFCs and expose them to HIDRA's plasma with subsequent intershot in-vacuo surface analysis in HIDRA-MAT for plasma-material interaction studies.

42 ENGINEERING↗

DOE OSTI2023

Modeling Ethanol-Blend Fuel Sprays under Direct-Injection Spark-Ignition Engine Conditions

Computational modeling of fuel-injection and fuel-impingement processes was carried out to provide insight into previous experimental results obtained from a direct-injection spark-ignition research engine operated with various ethanol and aromatic fuel blends. Seven model fuels were evaluated using both single- and split-injection strategies. Model results showed that droplet vaporization enriched the concentrations of aromatic species in the liquid phase, especially those with low vapor pressure, and ethanol-containing fuels altered droplet sizes and led to increased liquid-phase mass in the cylinder. For the spray-modeling conditions studied, most of the injected fuel remained in the liquid phase, which would be expected to result in more fuel impingement on cylinder or piston surfaces. Fuel impinging on lower cylinder-temperature surfaces was found to create wall films that could interact with the piston during the compression stroke. Fuel impinging on hotter piston-temperature surfaces vaporized more readily, but for fuels with high ethanol and aromatic content, wall films remained and were highly concentrated with lower vapor pressure and aromatic compounds. These films could lead to pool fires during combustion and therefore significant particulate matter emissions.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗

DOE OSTI2013

Multistage ion acceleration in finite overdense target with a relativistic laser pulse

“Multistage ion acceleration” has been analytically and computationally studied in the relativistic regime. For non-relativistic piston velocities, this phenomenon has been described before. But, as we go to relativistic piston velocities, the non-relativistic results hold no more. We have presented a fully relativistic calculation for second stage ion velocities and energies. To verify our calculations, we performed a fully relativistic 1D3V particle in cell simulations using the code LPIC++. It has been found that the relativistic calculations matched very well with the simulation results. Also, it has been seen that at relativistic piston velocities, the non-relativistic results differed by a significant margin. The feasibility of this process has been further established by three dimensional particle in cell simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Analysis of steady compaction waves in polyurea aerogel

In this work, steady compaction waves in an inert porous material are investigated using a p - α model. In a steady traveling wave reference frame, the one-dimensional Euler equations are reduced to a set of ordinary differential equations. A Mie-Grüneisen equation of state (EOS) is used with parameters calibrated for polyurea aerogel (PUA). Analytic solutions for non-equilibrium compaction are developed which compliment numerical simulations and are able to predict the complete wave structure, including the compaction wave speed, zone length, and final compacted solid volume fraction. The dynamic compaction of PUA is studied for a range of piston velocities. Three regions of behavior are identified: supersonic, subsonic-complete, and subsonic-partial compaction. Below a critical piston velocity, a subsonic compaction wave is produced without a leading shock. Finally, at even lower piston velocities, there is partial compaction and a greater dependence on the dynamic compaction relation. Some features and limitations of the current model are discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Shear Strength and Release of Large Cryogenic Pellets from the Barrel of a Shattered Pellet Injector for Disruption Mitigation

Shattered pellet injection (SPI) has been chosen as the baseline disruption mitigation system on ITER due to its ability to rapidly inject material deep into the plasma to greatly increase the plasma density and radiate the thermal energy. SPI utilizes a mechanical punch or high-pressure gas to release and accelerate a pellet that has been cryogenically desublimated in the barrel of a pipe gun. Various material injection combinations could possibly be implemented during different phases of a disruption event to radiate plasma energy, reduce electromagnetic loads on machine components, avoid the formation of runaway electrons, or to dissipate runaway electrons that form. Each injection phase could possibly utilize combinations of deuterium, neon, or argon. In this paper we outline experimental measurements of pellet material shear strength at SPI operating temperatures to understand the force needed to release SPI pellets. Deuterium, neon, argon, and deuterium-neon mixture pellets with diameters of 8.5, 12.5, and 15.7 mm are formed at a range of relevant gas pressures and temperatures and dislodged from the cold zone with a slow-moving piston driven by a motor. The slow-moving piston is kept above the triple point temperature of the material while the pellet is forming, then cooled to below the triple point temperature before contacting the pellet to minimize any thermal conduction to the pellet. The piston incorporates a load cell to measure the force applied when the pellet breaks away from the cold zone in the barrel.The ability of the gas and punch methods to exceed the shear strength of the studied pellet materials for release has been analyzed. High pressure gas delivered by fast opening valves produce pressure shock to the pellet due to supersonic expansion of the propellant gas. Pressure (and therefore, force) oscillations are present due to transverse density propagation throughout the breech volume. Mechanical punches deliver an impact force through a high-kinetic energy impact. The effect of the mechanical shock on the pellet has been explored and will be presented in this paper. Scaling to larger ITER size SPI pellets will be described.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Enhancing the efficiency benefit of thermal barrier coatings for homogeneous charge compression ignition engines through application of a low-k oxide

Prior experiments reported by the authors have proven the hypothesis that achieving a dynamic temperature swing on the combustion chamber surface will lead to improved thermal and combustion efficiencies of the homogeneous charge compression ignition engine. A thin layer of yttria-stabilized zirconia, roughly 150 μm, was plasma sprayed on the piston top. It led to markedly advanced ignition and heat release in the gasoline homogeneous charge compression ignition engine, accompanied with reduced unburnt hydrocarbon and carbon monoxide emissions, improved combustion efficiency, and a higher thermal efficiency. A related computational study highlighted the critical role of coating thermal conductivity in achieving a desired dynamic response; hence, the second phase of experimental investigations focused on introducing structured porosity in the yttria-stabilized zirconia coating, as a means of reducing effective conductivity. Indeed, additional incremental improvements were observed, as well as limitations related to adverse effects of the surface roughness and the fuel interactions with the surface roughness and open pores. Erosion can also be a problem in a direct injection engine. Therefore, the third round of investigations focused on a material with a natively low conductivity (low-k), sprayed on the top of an Al piston in a relatively dense form, and in a way that yields a smooth surface. The objective was to capitalize on the low conductivity, while avoiding the pitfalls accompanying high-porosity formulations. The heat-storage capacity was limited by keeping the thickness relatively low. The results verify the paramount importance of thermal conductivity in the context of high “temperature swing” behavior and indicate a potential to improve the homogeneous charge compression ignition engine’s combustion efficiency roughly 1.5%, with the overall indicated efficiency improvement on the order of 5%, on a relative basis. In addition, the low-k oxide thermal barrier applied to the piston extended significantly the low-load homogeneous charge compression ignition operability limit.

42 ENGINEERING↗

DOE OSTI2012

Fast 3D Surface Extraction

Ocean scientists searching for isosurfaces and/or thresholds of interest in high resolution 3D datasets required a tedious and time-consuming interactive exploration experience. PISTON research and development activities are enabling ocean scientists to rapidly and interactively explore isosurfaces and thresholds in their large data sets using a simple slider with real time calculation and visualization of these features. Ocean Scientists can now visualize more features in less time, helping them gain a better understanding of the high resolution data sets they work with on a daily basis. Isosurface timings (512 3 grid): VTK 7.7 s, Parallel VTK (48-core) 1.3 s, PISTON OpenMP (48-core) 0.2 s, PISTON CUDA (Quadro 6000) 0.1 s.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

Development of Cone Wedge Ring Expansion Test to Evaluate Mechanical Properties of Clad Tubing Structure

To determine the hoop tensile properties of irradiated fuel cladding in a hot cell, a cone wedge ring expansion test method was developed. A four-piece wedge insert was designed with tapered angles matched to the cone shape of a loading piston. The ring specimen was expanded in the radial direction by the lateral expansion of the wedges under the downward movement of the piston. The advantages of the proposed method are that implementation of the test setup in a hot cell is simple and easy, and that it enables a direct strain measurement of the test specimen from the piston’s vertical displacement soon after the wedge-clad contact resistance is initiated.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗