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Results for “Liquid Breakup”

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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Two Phase Detonation Studies Conducted in 1971

The research covered by this third annual progress report represents a continuation of our efforts devoted to the study of detonation waves in liquid-gas systems. The motivation for the work is associated with liquid propellant rocket motor combustion instability although certainly the studies are also applicable to internal combustion engines, jet propulsion engines, safety aspects of spilled liquid fuel, coal mine explosions, and weaponry. The research has been divided into 5 phases, although all of them are intimately related. For the most part these phases are briefly summarized and the reader is referred to other publications for a more complete treatment. The exception to this is where the material herein represents the only printed information available on the particular facet of the problem. Phase A has been primarily concerned with the breakup and ignition of fuel drops by shock waves. The experimental portion of this study as well as a theoretical treatment of the ignition behavior was completed in the past year. The research is now concentrating on the passage of a shock wave over a burning drop. Phase B has been devoted to the assessment of the approximate energy release pattern in two phase detonations insofar as they affect the significant overpressures observed.

Nicholls, J. A.↗
DOE OSTI2022

Fluid Flow Observations of The Spray Near-Field Using High-Speed X-Ray Imaging

Sprays are important to may industrial processes, but the near-field region where spray formation takes place is difficult to visualize and characterize through visible light imaging because this region is typically optically dense. X-ray imaging is one technique that can penetrate this optically dense region and provide unique observations of the spray formation process. This study uses high-speed white beam X-ray imaging conducted at the Advanced Photon Source to capture spray formation dynamics from a canonical airblast atomizer. In this work, a range of momentum flux ratios are visualized by varying the gas flow rate while the liquid flow rate is held constant. The use of X-rays show overlapping flow structures including bags, ligaments, mushrooms, and webs. Air bubbles are captured within the liquid regions, and a very dynamic crown forms at the liquid needle exit at higher momentum flux ratios. Finally, at the highest momentum flux ratios, air bubbles and liquid droplets are observed migrating upstream in the center of the crown, and this motion is attributed to a toroidal recirculation cell at the nozzle exit.

47 OTHER INSTRUMENTATION↗
NASA NTRS1972

Atomization of liquid droplets in a convective gas stream.

New experimental results are reported for the atomization of liquid droplets by a high-speed air stream. A series of experiments are described in which water droplets, ranging in diameter from 1000 to 2700 microns, were introduced into the test section of a shock tube and allowed to interact with the convective flow established by the passage of a propagating shock front. A rotating drum camera system was employed to obtain a collection of streak photographs of the atomization process from which the breakup time, the breakup distance, and the ultimate atomized particle size were determined.

Ranger, A. A.↗
NASA NTRS1993

Atomization and vaporization characteristics of airblast fuel injection inside a venturi tube

This paper describes the experimental and numerical characterization of the capillary fuel injection, atomization, dispersion, and vaporization of liquid fuel in a coflowing air stream inside a single venturi tube. The experimental techniques used are all laser-based. Phase Doppler analyzer was used to characterize the atomization and vaporization process. Planar laser-induced fluorescence visualizations give good qualitative picture of the fuel droplet and vapor distribution. Limited quantitative capabilities of the technique are also demonstrated. A modified version of the KIVA-II was used to simulate the entire spray process, including breakup and vaporization. The advantage of venturi nozzle is demonstrated in terms of better atomization, more uniform F/A distribution, and less pressure drop. Multidimensional spray calculations can be used as a design tool only if care is taken for the proper breakup model, and wall impingement process.

Sun, H.↗
NASA NTRS2017

Behavior of a Salt Water Solution Near the Critical Point Under Microgravity Conditions

The Supercritical Water Mixture (SCWM) experiment conducted on the International Space Station (ISS) is designed to study a salt-water solution in the vicinity of the critical transition with a test cell filled with Na2SO4 (aq) 0.5-w. This salt is a Type II salt which undergoes a dramatic decrease in solubility past waters critical point. The paper discusses the liquid-vapor-salt distribution in the test cell for subcritical, trans-critical, and supercritical regimes. In 0-g, the vapor-liquid interface manifests itself by the presence of a large single vapor bubble that is flattened between the two windows. In contrast with pure water, the vapor bubble remains centered in the test cell and is stable for temperatures up to Tc - 50 mK. The processes leading to critical transition during heat-up, as marked by the break-up of the vapor bubble, depends on the applied heating rate. For temperature ramps 1 mKmin, the bubble interface begins to breakup with the formation of a large number of smaller bubbles. For larger temperature ramps (10mKmin), temperature gradients arise in the cell pushing the bubble toward a window surface. As the critical threshold is crossed small variations in cell temperature ( 1 mK) cause an observable spatial variation in density. However, this spatial variation is not discernible as the temperature is increased further into the supercritical regime. The salt precipitation in the vicinity of the critical crossing appears to be heterogeneous in nature with precipitates observable on the cell windows. Direct imaging as well as light scattering indicate a hexagonal structure of the precipitated salt crystals in the near critical regime. The salt deposition is not fully reversible as the temperature is reduced due to window corrosion effects which traps some of the precipitated salt. Critical temperatures as high as 1.9 K above the value for pure water (647.25 K) have been measured. Finally, results on the critical transition phenomena in the presence of an imposed temperature gradient, demonstrating the remarkable stability of the central bubble, are also presented.

near-critical↗
NASA NTRS1999

Drop Ejection From an Oscillating Rod

The dynamics of a drop of a Newtonian liquid that is pendant from or sessile on a solid rod that is forced to undergo time-periodic oscillations along its axis is studied theoretically. The free boundary problem governing the time evolution of the shape of the drop and the flow field inside it is solved by a method of lines using a finite element algorithm incorporating an adaptive mesh. When the forcing amplitude is small, the drop approaches a limit cycle at large times and undergoes steady oscillations thereafter. However, drop breakup is the consequence if the forcing amplitude exceeds a critical value. Over a wide range of amplitudes above this critical value, drop ejection from the rod occurs during the second oscillation period from the commencement of rod motion. Remarkably, the shape of the interface at breakup and the volume of the primary drop formed are insensitive to changes in forcing amplitude. The interface shape at times close to and at breakup is a multi-valued function of distance measured along the rod axis and hence cannot be described by recently popularized one-dimensional approximations. The computations show that drop ejection occurs without the formation of a long neck. Therefore, this method of drop formation holds promise of preventing formation of undesirable satellite droplets.

Wilkes, E. D.↗
NASA NTRS1991

Static shape and instability of an acoustically levitated liquid drop

Dynamical aspects of a drop drastically flattened by acoustic radiation stress are considered. Its static equilibrium has been studied, starting with a dislike shape and modeling the sound field and the associated radiation stress according to this geometry. It is suggested that, at low viscosity, the ripples are capillary waves generated by the parametric instability excited by the membrane vibration, which is driven by the sound pressure. Atomization occurs whenever the membrane becomes so thin that the vibration is sufficiently intense. Buckling occurs when an existent equilibrium is unstable to a radial oscillation of the membrane because of the Bernoulli effect. The radiation stress at the rim of the flattened drop is also destabilizing and leads to horizontal expansion and subsequent breakup.

Lee, C. P.↗
DOE OSTI2023

SAF Combustion & Soot Processes [Slides]

The atomization, mixing, combustion and emissions characteristics of aviation fuels were measured using a novel approach based on a non-continuous injection scheme called the single-hole atomizer (SHA). High-speed microscopy revealed differences between fuels in terms of evaporation and mixing regimes over conditions relevant to modern and next generation aero-engine combustors. Measurements of liquid and vapor penetration, mixing fields, combustion and emissions metrics (ignition delay, lift-off length, PAH formation, soot mass) highlighted the effects of fuels and combustor conditions. The experimental results are being leveraged to adjust and validate chemical and CFD models. Detailed analysis of sampled soot showed subtle differences in soot morphology between fuels. The results revealed the presence of contaminants potentially affecting surface chemistry and the nucleation propensity of water droplets on particles. Chemical mechanisms for NJFCP A-2, C-1 and C-4 showed good performance over a large parameter space. Spray breakup at relight conditions is vastly different from the atomization observed at high pressure. CFD simulations of the SHA target conditions confirmed the good behavior of the C-1 kinetic mechanism. The simulations support the strong relationship between low and high temperature reactions. New altitude chamber facility to enable detailed characterization of the heterogeneous nucleation process of water on aerosol particles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Implementation of Surface Tension on a Reacting Flow Solver, PeleLM: Preprint

In liquid rocket engines, the fuel is supplied to the combustion chamber in the liquid state though injectors. Such fuel undergoes atomization, vaporization, and combustion processes. To design reliable and efficient injectors, it is required to understand the full processes. This research is part of an effort to develop a full atomization-vaporization-combustion solver from first principles. As an initial step to tackle the atomization process, a multiphase flow solver is under development. For the development, a library of the volume of fluid scheme for multiphase, IRL is coupled with a reacting Navier-Stokes equation solver, PeleLM. Furthermore, as the surface tension has considerable effects on spray breakup. surface tension is implemented in the momentum equation using the continuum surface force model and the improved height function technique.

height function↗
DOE OSTI2024

Challenging Common Assumptions of Thick-Wall Chamber Dynamics in Inertial Fusion Systems using MOOSE

As an increasing number of companies look toward commercial Inertial Fusion Energy (IFE) designs, there is a pressing need to understand the physics of thick-wall chamber gas dynamics. The thick liquid wall approach implements a renewable wall to mitigate the fusion target emissions, thereby reducing the radiation damage rate and significantly extending the lifetime of chamber structures, leading to increased plant availability and reduced waste streams in comparison to dry wall chamber designs. It is necessary, however, to assess the critical performance and safety aspects of these systems. For example, it is crucial to predict (1) where the mass ablated from the liquid walls will vent, which determines the placement of condensing surfaces; (2) debris propagation up the beam lines, which provides essential information for design and protection requirements; (3) peak pressures and impulse on chamber walls, which affect chamber structural design; and (4) momentum transfer to the liquid jets, which constrains the shape and positioning of the jets. In turn, the chamber design and its liquid walls affect shielding requirements, material activation, and tritium fuel cycle. Currently available simulation tools, however, are unable to accurately capture key thick-wall chamber dynamics. Significant assumptions are often made to simplify the system and reduce computational cost and modeling capability needs, but the impact of these assumptions on simulation predictions has not been evaluated. For example, no three-dimensional simulations can be found in the open literature to evaluate gas venting and momentum transfer to the jets with simulations using two-dimensional domains to represent complex three-dimensional geometries. Moreover, limited studies have been dedicated to jet breakup due to both turbulence and neutron heating, and no studies have been found that evaluate how jet breakup can impact shock-jet interaction. Furthermore, effects of radiative heat transfer have rarely been included for the hydrodynamic phase of shock propagation, and integration of proper equations of state in shock dynamics codes has been mostly exploratory. In this study, we use the flexible, high-fidelity Multiphysics Object-Oriented Simulation Environment (MOOSE) to model these complex phenomena and inform design and safety studies. Capabilities to model thick-wall chamber gas dynamics are being developed, and the impact of the assumptions listed above (i.e., two-dimensional vs three-dimensional, absence of jet breakout, no radiative heat transfer, and ideal gas behavior) are being quantified.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Challenging Common Assumptions of Thick-Wall Chamber Dynamics in Inertial Fusion Systems Using MOOSE-based Multiphysics Simulations

As an increasing number of companies look toward commercial Inertial Fusion Energy (IFE) designs, there is a pressing need to understand the physics of thick-wall chamber gas dynamics. The thick liquid wall approach implements a renewable wall to mitigate the fusion target emissions, thereby reducing the radiation damage rate and significantly extending the lifetime of chamber structures, leading to increased plant availability and reduced waste streams in comparison to dry wall chamber designs. It is necessary, however, to assess the critical performance and safety aspects of these systems. For example, it is crucial to predict (1) where the mass ablated from the liquid walls will vent, which determines the placement of condensing surfaces; (2) debris propagation up the beam lines, which provides essential information for design and protection requirements; (3) peak pressures and impulse on chamber walls, which affect chamber structural design; and (4) momentum transfer to the liquid jets, which constrains the shape and positioning of the jets. In turn, the chamber design and its liquid walls affect shielding requirements, material activation, and tritium fuel cycle. Currently available simulation tools, however, are unable to accurately capture key thick-wall chamber dynamics. Significant assumptions are often made to simplify the system and reduce computational cost and modeling capability needs, but the impact of these assumptions on simulation predictions has not been evaluated. For example, no three-dimensional simulations can be found in the open literature to evaluate gas venting and momentum transfer to the jets with simulations using two-dimensional domains to represent complex three-dimensional geometries. Moreover, limited studies have been dedicated to jet breakup due to both turbulence and neutron heating, and no studies have been found that evaluate how jet breakup can impact shock-jet interaction. Furthermore, effects of radiative heat transfer have rarely been included for the hydrodynamic phase of shock propagation, and integration of proper equations of state in shock dynamics codes has been mostly exploratory. In this study, we use the flexible, high-fidelity Multiphysics Object-Oriented Simulation Environment (MOOSE) to model these complex phenomena and inform design and safety studies. Capabilities to model thick-wall chamber gas dynamics are being developed, and the impact of the assumptions listed above (i.e., two-dimensional vs three-dimensional, absence of jet breakout, no radiative heat transfer, and ideal gas behavior) are being quantified.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

First Measurement of Sub-GeV $ν_μ$ Charged-Current Coherent Pion Production on Argon in MicroBooNE

We report a measurement of the charged-current coherent pion production cross section on argon using the MicroBooNE liquid argon time projection chamber exposed to the Booster Neutrino Beam at Fermilab. The measurement uses the MicroBooNE data set corresponding to $1.26 \times 10^{21}$ protons on target with a mean neutrino energy of $0.8$~GeV. The flux-averaged cross section is measured to be $(9.1 \pm 1.2_{\text{stat}} \pm 1.2_\text{syst}) \times 10^{-40}\,\text{cm}^2/\text{Ar}$. This result represents the first measurement of charged-current coherent pion production on argon at sub-GeV neutrino energies. Due to its clean two-body kinematics, where the neutrino interacts coherently with the entire nucleus producing a forward muon and pion with no nuclear breakup, this process provides a useful tool for constraining neutrino flux uncertainties in current and future oscillation experiments such as DUNE.

Abratenko, P. [Tufts U.] (ORCID:0000000169455941)↗
DOE OSTI2022

High-repetition-rate, multi-MeV deuteron acceleration from converging heavy water microjets at laser intensities of 10 21 W/cm 2

Herein we demonstrate high repetition-rate deuteron acceleration by irradiating a continuously flowing, ambient temperature liquid heavy water jet with the high-intensity ALEPH laser. The laser delivered up to 5.5 J (120 TW, 1.2 × 10 21 W/cm 2 ) laser energy on target at 0.5 Hz. A high repetition-rate Thomson parabola spectrometer measured the deuteron beam energy spectra on each shot for 60 sequential shots (two minutes). Peak fluxes of 5 x 10 10 deuterons/sr/pulse, corresponding to an average flux of 1.5 x 10 12 deuterons/sr/min, were demonstrated with deuteron energies reaching up to 4.4 MeV. High shot-to-shot stability is observed up to 40%–50% of the maximum deuteron energy. These deuteron beams are suited for fast neutron production through deuteron breakup in a converter yielding energies similar to deuteron–deuteron (D–D, 2.45 MeV) fusion reactions of importance for material damage studies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

A physics-driven Σ-Y atomization model for heavy-duty engine simulations

The atomization of a liquid jet is a multi-scale and multi-physics problem of interest for many engineering applications. Particularly, it drives the fuel-oxidizer mixing and dictates the efficiency of combustion engines. High-fidelity multi-phase simulations remain challenging due to the excessive computational cost required to capture all the atomization scales. Thus, atomization models are necessary to represent sub-grid liquid structures. Here, in this work, a modified Σ-Y model in the context of Eulerian-Lagrangian Spray Atomization (ELSA) is used to transport the surface area density of the spray. The model's predictive performance is assessed under various operating conditions relevant to heavy-duty engines using the Engine Combustion Network (ECN) Spray C and Spray D research-grade injectors. The classic droplet collision formulation of the Σ-Y model alone does not replicate the response of the measured spray surface area to changes in injector, ambient pressure, and injection pressure, requiring individual tuning of the model's parameters. Instead, a transition between dense and dilute spray breakup mechanisms is proposed in terms of the average droplet spacing. The collision breakup mechanism represents the dilute spray, whereas the droplet size in the dense spray is driven by a competition between the integral scale of turbulence and the balance between the turbulent kinetic energy and the surface energy of the droplets. Such an approach minimizes the requirements for model tuning. Moreover, the role of the constants of a compressible standard k-ε RANS model is assessed in the injector's internal flow and external spray simulation framework, and an updated set is proposed. The results are validated against x-ray radiography and Ultra-Small Angle X-ray Scattering (USAXS) data and highlight the predictive capabilities of the proposed physics-driven Σ-Y model, which is compatible with engine simulation turnaround times.

42 ENGINEERING↗
NASA NTRS2003

Unstructured LES of Reacting Multiphase Flows in Realistic Gas Turbine Combustors

As part of the Accelerated Strategic Computing Initiative (ASCI) program, an accurate and robust simulation tool is being developed to perform high-fidelity LES studies of multiphase, multiscale turbulent reacting flows in aircraft gas turbine combustor configurations using hybrid unstructured grids. In the combustor, pressurized gas from the upstream compressor is reacted with atomized liquid fuel to produce the combustion products that drive the downstream turbine. The Large Eddy Simulation (LES) approach is used to simulate the combustor because of its demonstrated superiority over RANS in predicting turbulent mixing, which is central to combustion. This paper summarizes the accomplishments of the combustor group over the past year, concentrating mainly on the two major milestones achieved this year: 1) Large scale simulation: A major rewrite and redesign of the flagship unstructured LES code has allowed the group to perform large eddy simulations of the complete combustor geometry (all 18 injectors) with over 100 million control volumes; 2) Multi-physics simulation in complex geometry: The first multi-physics simulations including fuel spray breakup, coalescence, evaporation, and combustion are now being performed in a single periodic sector (1/18th) of an actual Pratt & Whitney combustor geometry.

Ham, Frank↗
NASA NTRS2004

Characterization of Space Shuttle External Tank Thermal Protection System (TPS) Materials in Support of the Columbia Accident Investigation

NASA suffered the loss of the seven-member crew of the Space Shuttle Columbia on February 1, 2003 when the vehicle broke apart upon re-entry to the Earth's atmosphere. The final report of the Columbia Accident Investigation Board (CAIB) determined that the accident was caused by a launch ascent incident-a suitcase-sized chunk of insulating foam on the Shuttle's External Tank (ET) broke off, and moving at almost 500 mph, struck an area of the leading edge of the Shuttle s left wing. As a result, one or more of the protective Reinforced Carbon-Carbon (RCC) panels on the wing leading edge were damaged. Upon re-entry, superheated air approaching 3,000 F breached the wing damage and caused the vehicle breakup and loss of crew. The large chunk of insulating foam that broke off during the Columbia launch was determined to come from the so-called bipod ramp area where the Shuttle s orbiter (containing crew) is attached to the ET. Underneath the foam in the bipod ramp area is a layer of TPS that is a cork-filled silicone rubber composite. In March 2003, the NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama received cured samples of the foam and composite for testing from the Michoud Assembly Facility (MAF) in New Orleans, Louisiana. The MAF is where the Shuttle's ET is manufactured. The foam and composite TPS materials for the ET have been well characterized for mechanical property data at the super-cold temperatures of the liquid oxygen and hydrogen fuels used in the ET. However, modulus data on these materials is not as well characterized. The TA Instruments 2980 Dynamic Mechanical Analyzer (DMA) was used to determine the modulus of the two TPS materials over a range of -145 to 95 C in the dual cantilever bending mode. Multi-strain, fixed frequency DMA tests were followed by multi-frequency, fixed strain tests to determine the approximate bounds of linear viscoelastic behavior for the two materials. Additional information is included in the original extended abstract.

Wingard, Charles D.↗
NASA NTRS1990

Interfacial dynamics of two liquids under an oscillating gravitational field

The evolution of two miscible liquids meeting at an initially sharp interface inside a cavity under microgravity g-jitter conditions is studied numerically. The response of the interface and kinematics of the flowfield to various g-jitter accelerations and aspect ratio variations is shown. The interface region acts like a vortex source sheet, and it can be unstable to Kelvin-Helmholtz and Rayleigh-Taylor instabilities. The vortices produced along the interface can serve as a stirring mechanism to promote local mixing. Below the critical Stokes-Reynolds number, the destabilization of the interface results in deformation into wavy structures. In some parameter regions, these structures oscillate in time; in others, they are quasi-steady. Above the critical Stokes-Reynolds number, 'chaotic' instability results, and the interface breaks into concentration pockets. The morphology of the initial breakup is similar to observed Rayleigh-Taylor instability. Subsequent mixing of the two fluids after the breakup of the interface is then very rapid.

Duval, Walter M. B.↗
NASA NTRS1994

A Theoretical Evaluation of Secondary Atomization Effects on Engine Performance for Aluminum Gel Propellants

A one-dimensional model of a gel-fueled rocket combustion chamber has been developed. This model includes the processes of liquid hydrocarbon burnout, secondary atomization. aluminum ignition, and aluminum combustion. Also included is a model of radiative heat transfer from the solid combustion products to the chamber walls. Calculations indicate that only modest secondary atomization is required to significantly reduce propellant burnout distances, aluminum oxide residual size and radiation heat wall losses. Radiation losses equal to approximately 2-13 percent of the energy released during combustion were estimated. A two-dimensional, two-phase nozzle code was employed to estimate radiation and nozzle two-phase flow effects on overall engine performance. Radiation losses yielded a 1 percent decrease in engine I(sub sp). Results also indicate that secondary atomization may have less effect on two-phase losses than it does on propellant burnout distance and no effect if oxide particle coagulation and shear induced droplet breakup govern oxide particle size. Engine I(sub sp) was found to decrease from 337.4 to 293.7 seconds as gel aluminum mass loading was varied from 0-70 wt percent. Engine I(sub sp) efficiencies, accounting for radiation and two-phase flow effects, on the order of 0.946 were calculated for a 60 wt percent gel, assuming a fragmentation ratio of 5.

Mueller, D. C.↗