The Statistical Description of a Spray in Terms of Drop Velocity, Size and Position
Statistical description of spray formation in terms of drop velocity, size and position
SPRAY↗
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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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Production of monodisperse sprays.
Monodisperse sprays production technique using Rayleigh criterion for breakup of capillary jets by mechanically vibrating uniform size capillary needles arranged in parallel
VIBRATION EFFECT↗
Simplified guide to thermal-spray coatings.
Metal surface property improvement by thermal- spray coating noting flame plating
FLAME PLATING↗
Plasma-sprayed dielectric coatings for heat sinks in electronic packaging.
Plasma sprayed alumina and beryllia dielectric coatings for heat sinks in electronic packaging, emphasizing heat dissipation from heat/generating components
ELECTRONIC PACKAGING↗
A spray-on electrode for recording the electrocardiogram during exercise.
Spray-on electrode for recording electrocardiograms during exercise
ELECTRODES↗
Production Mechanisms, Number Concentration, Size Distribution. Chemical Composition, and Optical Properties of Sea Spray Aerosols
Over forty scientists from six countries convened in Raleigh, NC on June 4-6 2012 to review the status and prospects of sea spray aerosol research. Participants were researchers from the oceanography and atmospheric science communities, including academia, private industry, and government agencies. The recommendations from the working groups are summarized in a science prioritization matrix that is meant to prioritize the research agenda and identify areas of investigation by the magnitude of their impact on proposed science questions. Str
sea spray aerosol↗
Radiation Shielding Plasma Sprayed Coatings Heads to International Space Station for MISSE-17 Experiments
NASA's Artemis program aims to return to the moon in search of scientific discoveries and establish a habitat using in-situ resource utilization. However, the past lunar explorations presented challenges, such as thermal cycles, solar and intergalactic cosmic radiation, and severe abrasive interaction of sharp lunar regolith particles[1]–[4].Dust mitigation and radiation shielding have become the most important concerns for lunar structural components and rovers which can fail abruptly without a protective solution. To counter these threats, Plasma Forming Laboratory(PFL) at Florida International University (FIU), in collaboration with NASA, has developed a novel multi-functional coating to protect the components synergistically against abrasion, erosion ,and radiation. The titanium-boron nitride composite coatings were prepared using the atmospheric plasma spray technique from engineered composite powders [5], [6].The coatings were subjected to extensive characterization and tribological study with lunar mare simulant JSC-1A, which shows tremendous improvement in the wear performance. The coatings subjected to neutron radiation shielding experiments at NASA Langley Research Center exhibited significantly improved neutron attenuation capacity compared to the substrate. The coating is selected to undergo radiation exposure on the International Space Station as a part of MISSE-17 (Materials International Space Station Experiment).
Thermal Spray↗
Investigation of the Mechanical Degradation of Zinc-Based Cold Spray Coatings for Steel Pipelines
Internal corrosion in wet natural gas is a big challenge in the oil and gas industry due to corrosive constituents such as carbon dioxide (CO2), hydrogen sulfide (H2S), other forms of sulfur, and water in the gas stream. To mitigate internal corrosion, zinc-based cold spray coatings were designed for use in natural gas pipelines to increase the lifespan of the pipeline network. However, one of the requirements in designing internal coatings is the resistance of the coatings to mechanical forces applied on the pipeline's internal wall during pigging operations. These forces are primarily compressive and shear/friction forces. This study examines material properties that must be considered when evaluating mechanical considerations. To determine the viability of the developed coatings with respect to the shear/friction forces, the shear adhesion and wear resistance of the materials have been evaluated. Shear adhesion testing was performed with modified clevises to determine the shear stress required to cause adhesion failure at the coating/substrate interface. Scanning electron microscopy was utilized to characterize the interfaces after failure. Wear testing was performed on coatings and pipeline materials utilizing pin-on-drum testing. These tests display the stress limitations and wear that the coatings can tolerate from pigging.
mechanical degradation↗
Spray Pyrolysis-Aerosol Deposition for the Production of Thick Yttria-Stabilized Zirconia Coatings
Aerosol deposition (AD) is a coating technique wherein particles are impacted onto a target substrate at reduced pressures, and supersonic particle impact velocities lead to coating consolidation. The limiting step in AD application is often not supersonic deposition operation, but aerosolization of powder particles with the proper size distribution; the translational impact velocity is strongly size-dependent. It is demonstrated that by directly synthesizing particles in the gas phase, size-controlled ceramic particles can be injected into AD systems. This in situ formation step obviates the need for particle aerosolization. Ultrasonic spray pyrolysis (USP) is applied to produce yttria-stabilized zirconia (YSZ), and USP is directly coupled with AD to produce consolidated, thick, YSZ coatings on metal substrates. USP-AD yields YSZ coatings on stainless steel and aluminum substrates with porosities <0.20, which grow to thicknesses beyond 100 μm. Aerodynamic particle spectrometry and electron microscopy reveal that the depositing particles are 200 nm–1.2 μm in diameter, though each particle is composed of nanocrystalline YSZ. Supporting computational fluid dynamics calculations demonstrate that the YSZ particle impact speeds are above 300 m s -1 . Thermal conductivity measurements demonstrate that USP-AD coatings have conductivities consistent with those produced from high-temperature processes.
36 MATERIALS SCIENCE↗
Large‐Scale 2D Perovskite Nanocrystals Photodetector Array via Ultrasonic Spray Synthesis
Abstract 2D perovskite (PVSK) single crystals have received significant attention due to their unique optical and optoelectronic properties. However, current synthesis methods face limitations, particularly in large‐area fabrication, which remain critical barriers to practical applications. In this study, the synthesis of red/green/purple‐blue‐colored 2D PVSK nanocrystals over a large area (4‐inch wafer) and the fabrication of high‐performance photodetector arrays are presented via a facile yet efficient spray‐coating approach with a liquid‐bridge transport effect. The photodetector array achieves 100% working yield, high photo‐responsivity (1.5 × 10 6 A W −1 ) and specific‐detectivity (1.1 × 10 16 Jones) with competitive photomapping characteristics. An intelligent vision system for automatic shape recognition is further demonstrated with a recognition rate exceeding 90%. This study provides significant advances in the scalable synthesis of nanoscale 2D PVSK crystals, their integration into large‐area optoelectronic devices, and their potential use in artificial‐intelligence systems.
Lee, Yoon Ho [Davidson School of Chemical Engineer↗
Heterogeneous Catalysis by Fullerene C 60 : Photocatalytic Dehydro‐Dimerization of Primary Amines and Tetrahydroquinolines Studied Using Thread Spray Mass Spectrometry
Abstract Removal of a catalyst after a catalytic process is a time‐consuming and challenging process. In this paper, a fullerene catalyst coated on cellulose thread is developed and applied it in a heterogeneous photoreaction screening via a thread spray mass spectrometry (MS) platform. The surface of the cellulose thread is modified with NH 2 groups, which subsequently allows immobilization of fullerene C 60 on the thread. The final fullerene functionalized thread is placed in a glass capillary and the solution of the reactant to be interrogated is added. The assembly of thread and glass capillary is placed in front of a mass spectrometer, which serves as an online photoreaction platform after a light source and direct current high voltage are applied. As an ambient ionization approach, the photocatalytic reaction screening platform enabled real‐time MS characterization of products and intermediates and using only nanomole quantities of reactants. Fullerene C 60 is identified to facilitate dehydro‐dimerization reactions from amines. Norharmane shows a unique photo‐oxygenated dimer formation. The functionalized threads immobilized with fullerene C 60 are reusable, confirming the heterogeneous nature of the platform. Thus, this system provided real‐time screening of reactions catalyzed by fullerene C 60 and a means to investigate the reaction mechanism.
Chemistry↗
Image processing methods for Rayleigh scattering measurements of diesel spray mixing at high repetition rate
This work describes the diagnostic implementation and image processing methods to quantitatively measure diesel spray mixing injected into a high-pressure, high-temperature environment. We used a high-repetition-rate pulse-burst laser developed in-house, a high-speed CMOS camera, and optimized the optical configuration to capture Rayleigh scattering images of the vaporized fuel jets inside a constant volume chamber. The experimental installation was modified to reduce reflections and flare levels to maximize the images’ signal-to-noise ratios by anti-reflection coatings on windows and surfaces, as well as series of optical baffles. Because of the specificities of the high-speed system, several image processing techniques had to be developed and implemented to provide quantitative fuel concentration measurements. We find that these methods involve various correction procedures such as camera linearity, laser intensity fluctuation, dynamic background flare, as well as beam-steering effects. Image inpainting was also applied to correct the Rayleigh scattering signal from large scatterers (e.g. particulates). The experiments demonstrate that applying planar laser Rayleigh scattering at high repetition rate to quantitatively resolve the mixing of fuel and ambient gases in diesel jets is challenging, but possible. The thorough analysis of the experimental uncertainty and comparisons to past data prove that such measurements can be accurate, whilst providing valuable information about the mixing processes of high-pressure diesel jets.
47 OTHER INSTRUMENTATION↗
Micro-cold Spray Deposition of YSZ Films from Ultrafine Powders Using a Pressure Relief Channel Nozzle
Abstract The use of ultrafine powders in the micro-cold spray (MCS) process, also referred to as the aerosol deposition method, typically results in porous and/or poorly adhering films because the particles do not impact at a high enough velocity for sufficient plastic deformation and interparticle bonding to occur. Under typical operating conditions, particles < 100 nm accelerate to high velocities but then are slowed by the stagnant gas in the bow shock that forms just upstream of the substrate. Using larger particles reduces particle slowing, but large particles can cause erosion of the film at high impact velocity, decreasing deposition efficiency. In this study, a pressure relief channel nozzle using helium as a carrier gas is proposed such that high-velocity deposition of yttria-stabilized zirconia particles as small as 10 nm in diameter is possible. This is well below the size range of powders previously used for MCS. The proposed nozzle design increases impact velocities for 10, 20, and 50 nm particles by ~ 880, 560, and 160 m/s, respectively, when compared to a conventional nozzle. Experimental deposition of ultrafine 8YSZ powder shows that the pressure relief channel nozzle results in lower porosity and more uniform deposits, with a ∼ 186% increase in deposition efficiency.
Materials Science↗
Failure Analysis of Gas Spray Atomization Crucible Materials
An attempted induction melt for gas spray atomization of a Pd alloy at Savannah River National Laboratory experienced a series of faulty thermocouple readings leading to failure of multiple alumina ceramic components and the loss of the metal charge. The spherical powders are used in research and development efforts for hydrogen storage applications. The failure of the thermocouples led to high operating temperatures exceeding the expected operating temperatures. Estimated temperatures of the liquid metal were established by the comparison of the radio frequency power output and multiple temperature readings and determined to have exceeded the functional temperature range of the alumina components. Failure analyses of the event included characterization of the components using visual observation and X-Ray computed tomography of the frozen ingot.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Enhanced flow boiling heat transfer on chromium coated zircaloy-4 using cold spray technique for accident tolerant fuel (ATF) materials
Flow boiling heat transfer tests were conducted to evaluate the Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) of conventional and accident tolerant fuel (ATF) cladding materials, i.e., bare Zircaloy-4 (Zr4), and Zircaloy-4 coated with Chromium using physical vapor deposition (PVD) (Zr4-Cr-PVD) and cold spray process (Zr4-Cr-CS), respectively. The tests were performed on a single heater rod with a uniform heat flux profile, at the atmospheric pressure, inlet temperature (24 °C) and mass flow rate (750 kg/m 2 s). HTC’s were increased by 5.2% and 3.3% on Zr4-Cr-CS compared to bare Zr4 and Zr4-Cr-PVD. Improved HTCwas attributed to the increased void fraction and high roughness (Ra = 532 nm) of the Zr4-Cr-CS. In detail, the micro-cavities, which act as bubble seeds, were entirely distributed on the Zr4-Cr-CS, and these micro-cavities generated smaller and faster bubbles, thus the void fraction increased by 10.9% compared to bare Zr4. HTC is improved by these smaller and faster bubbles which can remove heat from the heater rod surface more efficiently. To identify the exact location of CHF, the surface temperature profile was measured using advanced fiber-optic sensors which have high temporal/spatial resolution (distance between point to point: ~2.5 mm, frequency ~100 Hz). CHF occurred at 80–95% along the heated length and showed an 11.6% reduction on Zr4-Cr-CS compared to bare Zr4. We hypothesize the CHF reduction was caused by the lower wettability of the Zr4-Cr-CS which reduces the liquid supply to the surface, and vigorous bubble accumulation owing to high void fraction near the outlet, which results in early formation of the vapor film. During the post-CHF quenching phase, the rougher Zr4-Cr-CS showed larger cooling rates compared to the bare Zr4 and Zr4-Cr-PVD, preventing of oxidation by chromium layer. In conclusion, we demonstrate that the high roughness on the Zr4-Cr-CS increased the number of micro-cavities on the surface, resulting in 5.2% increase in HTC and improvement in the quenching heat transfer performance whereas CHF was 11.6% reduced compared to bare Zr4. Overall statistically there is little effect in the coating with regards to CHF and slight improvement in HTC.
42 ENGINEERING↗
Soot and PAH formation in high pressure spray pyrolysis of gasoline and diesel fuels
Time-resolved soot and PAH formation from gasoline and diesel spray pyrolysis are visualized and quantified using diffuse back illumination (DBI) and laser induced fluorescence (LIF) at 355 nm, respectively, in a constant-volume vessel at 60 bar from 1400 to 1700 K for up to 30 ms. The delay, maximum formation rate, and yield of soot and PAHs are compared across fuels and temperatures and correlated with the yield sooting indices on either the mass or mole basis. The delays generally decrease with increasing temperature, and the formation rates of both PAHs and soot generally increase with temperature. The apparent PAH-LIF yield may decrease with temperature due to PAH growth and conversion into larger species, signal trapping, and thermal quneching. Soot yield generally increases with temperature. The mass-based YSI correlates reasonably well with soot delay, but YSI does not correlate well with soot yield. Here, the mass-based YSI is a more appropriate predictor of sooting propensity than the mole-based YSI.
42 ENGINEERING↗
High pressure/high temperature multiphase simulations of dodecane injection to nitrogen: Application on ECN Spray-A
The present work investigates the complex phenomena associated with pressure/high temperature dodecane injection for the Engine Combustion Network (ECN) Spray-A case, employing more elaborate thermodynamic closures, to avoid well known deficiencies concerning density and speed of sound prediction using traditional cubic models. A tabulated thermodynamic approach is proposed here, based on log 10 (p)-T tables, providing very high accuracy across a large range of pressures, spanning from 0 to 2500 bar, with only a small number of interpolation points. The tabulation approach is directly extensible to any thermodynamic model, existing or to be developed in the future. Here NIST REFPROP properties are used, combined with PC-SAFT Vapor-Liquid-Equilibrium to identify the liquid in mixtures penetration, hence avoiding the use of an arbitrary threshold for mass fraction. Identified liquid and vapour penetration are compared against experimental data from the ECN database showing a good agreement, within approximately 3–8% for axial penetration of liquid, 2% for vapor axial penetration and within experimental uncertainty for radial distribution of mass fraction. Analysis of the vortex evolution indicates that driving mechanisms behind the jet break-up are vortex tilting/stretching, then baroclinic torque, leading to Rayleigh-Taylor instabilities, closely followed by vortex dilation and finally viscous effects.
42 ENGINEERING↗
Corrosion behavior in aluminum/galvanized steel resistance spot welds and self-piercing riveting joints in salt spray environment
Here, this paper underlined the corrosion behavior of aluminum alloy/galvanized steel joints fabricated by resistance spot welding (RSW) and self-piercing riveting (SPR) exposed to different salt-spray cycles. It was found that the crevice generated by different joining methods has an important impact on corrosion behavior. Compared with the RSW joint, less corrosion happened on the coupled regions in SPR joints because of the higher local pH value resulted from the smaller crevice. The crevice, however, has less impact on the types of corrosion products. Galvanic corrosion happened in the coupled region for both RSW and SPR joints. The Pourbaix diagram explained the stable corrosion products of Al and Zn—Fe alloy, which are Al 2 O 3 , ZnO, and Fe 3 O 4 . Additional corrosion products observed from the experiment included α-Al(OH) 3 , Ca 4 Al 2 (CO 3 )(OH) 12 (H 2 O) 5 , Zn 5 (OH) 8 Cl 2 (H 2 O), Zn 5 (CO 3 ) 2 (OH) 6 , and Fe 2 (OH) 2 (CO 3 ), which can be understood by considering the metastable corrosion products, Pourbaix diagram, and possible chemical reactions.
36 MATERIALS SCIENCE↗