Slower Evaporation Research Articles

Investigating Spray Characteristics of Synthetic Fuels: Comparative Analysis with Gasoline

Article Investigating Spray Characteristics of Synthetic Fuels: Comparative Analysis with Gasoline Weidi Huang 1,2, Mitsuharu Oguma 2, Koichi Kinoshita 2, * , Yohko Abe 2, and Kotaro Tanaka 1,3 1 Carbon Recycling Energy Research Centre, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi 316-8511, Japan 2 Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology, Namiki 1-2-1, Tsukuba 305-8564, Japan 3 Graduate School of Science and Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi 316-8511, Japan * Correspondence: koichi-kinoshita@aist.go.jp Received: 13 March 2024; Revised: 22 May 2024; Accepted: 31 May 2024; Published: 5 June 2024 Abstract: Studying synthetic fuels is imperative due to their potential to offer sustainable alternatives to conventional fossil fuels, thereby addressing environmental concerns, enhancing energy security, and facilitating the transition to cleaner and more efficient transportation systems. This study presents an experiment analysis concentrating on spray characteristics of five types of synthetic fuels (bio-naphtha, EtG, G40, bio-ethanol, and DMC) in a comparison with gasoline. The experiment was conducted ranging from non-evaporated conditions to evaporated conditions, to thoroughly assess the spray behavior of the tested fuels. Results showed that EtG and G40 share similar properties with conventional gasoline. The discharge coefficient (Cd) was found to increase closely linearly with the square root of fuel density. Under non-evaporated condition (Ta = 25 °C), except for DMC, the spray tip penetration of other fuels deviates within ±5% compared to gasoline. Under evaporated condition (Ta = 200 °C), EtG maintains a spray tip penetration within ±5% of gasoline, while bio-naphtha, G40, and DMC fall within ±10% of gasoline. Notably, bio-ethanol shows a 12% higher penetration compared to gasoline, likely due to its slower evaporation and higher latent heat of vaporization.

Polymorphism at hexadecanoic-acid crystals investigated through structural and vibrational studies

Hexadecanoic acid (HA) is a saturated fatty acid with wide industrial application due to its important chemical and physical properties. However, understanding of its polymorphic characteristics under a specific growth condition is still an open question. This paper shows HA crystals grown by the slow evaporation method with five different solvents. The polymorphism was evaluated by X-ray diffraction, Raman and Fourier-transform infrared (FT-IR) spectroscopy. Most of the crystals presented two main polymorphic phases, and the C polymorphic form common among samples appeared as a progressive increase with increasing solvent polarity. Nevertheless, solvents with slower evaporation allowed to obtain the Bm form as a minor phase. Furthermore, polar solvents with rapid evaporation allowed the growth of the Em form as a secondary phase. Vibrational analysis on the Raman- and IR-active bands indicated that almost all inter-molecular modes are more likely to gauche conformation than all-trans conformation. This behavior is due to changes in the hydrogen bonds (O−H.O) and, mainly, in the C-C bonds around the carboxylic group (COOH) that form the dimers between the pairs of molecules within the crystalline lattice.

Cryptogams build up a living microcosm: Geoecological effects of biocrusts on volcanic tephra (Haleakalā, Maui, Hawai’i)

This study analyzes data of moss/lichen biocrusts on volcanic tephra at 2335 m in Haleakalā Crater (Maui, Hawaiʻi). Samples were compared among three adjacent positions: rolling crusts, pinnacled crusts, and bare tephra; two profiles contrasted substrate variation in crust and tephra areas. Field experiments assessed soil shear- and compressive-strength, infiltration rates, and diurnal soil temperatures; a lab experiment measured evaporation from crust specimens for 9 days. Biocrusts significantly affected physical, chemical, and structural soil properties. Fine particles, organic matter, and water storage were appreciably greater in biocrusts. Microsampling indicated upper-pinnacle sections accumulated more fine grains due to capture of volcanic ash, and also contained greater organic matter, than lower-pinnacle portions. Crust areas experienced infiltration rates ~2.8 times faster than tephra; mean diurnal temperatures were 12.1 °C (26.9 vs 39.0 °C) cooler in crusts than in tephra. Saturated crust specimens stored ~2.7 times more moisture than tephra soils; slower evaporation in biocrusts significantly lengthened the period over which poikilohydric cryptogams are able to maintain metabolic activity. Soil shear- and compressive-strength were higher on crusts than on tephra. Biocrust soils showed greater fertility, as available Ca2+, Mg2+, K+, P, NH4+-N, and cation-exchange capacity were higher than in tephra. NH4+-N was more concentrated under rolling crusts than in pinnacled ones; this is mainly ascribed to sampling methodology. Buried profile horizons suggest the site experienced additional tephra deposition during episodic volcanic eruptions. A developmental model assesses interactions among soil and environmental processes, and provides an integrated geoecological view of linkages that influenced biocrust genesis.

An investigation of mixture formation characteristics of a free-piston gasoline engine with direct-injection

The free-piston engine generator (FPEG) is regarded as a substitute of conventional combustion engine (CCE) because of special operation mechanism and potential advantages. This article presents an investigation to analyze the fuel spray and mixture formation characteristics of a direct injection gasoline FPEG by comparing a corresponding CCE. A full-cycle multi-dimensional fuel spray model is established by coupling with dynamic, and then it is validated experimentally to predict fuel diffusion and mixture formation in the FPEG. Results indicate that compared with the CCE, the FPEG operates with lower in-cylinder gas turbulence, pressure and temperature during injection stage, so the fuel spray in FPEG receives a smaller gas resistance and behaves more impingement, longer penetration, slower evaporation, larger sauter mean diameter (SMD), and lower mixture uniformity in this stage than the CCE. However, the slower compression process of FPEG not only makes that the fuel droplets evaporates earlier, but also provides a longer duration for fuel-air mixing and diffusion. Therefore, at the moment of spark ignition, a more homogeneous mixture is formed in the FPEG, and it shows smaller SMD and higher concentration around spark plug than the CCE. This phenomenon may facilitate the spark ignition and high efficiency combustion.

Charging and Release Mechanisms of Flexible Macromolecules in Droplets.

We study systematically the charging and release mechanisms of a flexible macromolecule, modeled by poly(ethylene glycol) (PEG), in a droplet by using molecular dynamics simulations. We compare how PEG is solvated and charged by sodium Na+ ions in a droplet of water (H2O), acetonitrile (MeCN), and their mixtures. Initially, we examine the location and the conformation of the macromolecule in a droplet bearing no net charge. It is revealed that the presence of charge carriers do not affect the location of PEG in aqueous and MeCN droplets compared with that in the neutral droplets, but the location of the macromolecule and the droplet size do affect the PEG conformation. PEG is charged on the surface of a sodiated aqueous droplet that is found close to the Rayleigh limit. Its charging is coupled to the extrusion mechanism, where PEG segments leave the droplet once they coordinate a Na+ ion or in a correlated motion with Na+ ions. In contrast, as PEG resides in the interior of a MeCN droplet, it is sodiated inside the droplet. The compact macro-ion transitions through partially unwound states to an extended conformation, a process occurring during the final stage of desolvation and in the presence of only a handful of MeCN molecules. For charged H2O/MeCN droplets, the sodiation of PEG is determined by the H2O component, reflecting its slower evaporation and preference over MeCN for solvating Na+ ions. We use the simulation data to construct an analytical model that suggests that the droplet surface electric field may play a role in the macro-ion-droplet interactions that lead to the extrusion of the macro-ion. This study provides the first evidence of the effect of the surface electric field by using atomistic simulations. Graphical Abstract ᅟ.

Formation of coffee-stain patterns at the nanoscale: The role of nanoparticle solubility and solvent evaporation rate

When droplets of nanoparticle suspension evaporate from surfaces, they leave behind a deposit of nanoparticles. The mechanism of evaporation-induced pattern formation in the deposit is studied by molecular dynamics simulations for sessile nanodroplets. The influence of the interaction between nanoparticles and liquid molecules and the influence of the evaporation rate on the final deposition pattern are addressed. When the nanoparticle-liquid interaction is weaker than the liquid-liquid interaction, an interaction-driven or evaporation-induced layer of nanoparticles appears at the liquid-vapor interface and eventually collapses onto the solid surface to form a uniform deposit independently of the evaporation rate. When the nanoparticle-liquid and liquid-liquid interactions are comparable, the nanoparticles are dispersed inside the droplet and evaporation takes place with the contact line pinned at a surface defect. In such a case, a pattern with an approximate ring-like shape is found with fast evaporation, while a more uniform distribution is observed with slower evaporation. When the liquid-nanoparticle interaction is stronger than the liquid-liquid interaction, evaporation always occurs with receding contact line. The final deposition pattern changes from volcano-like to pancake-like with decreasing evaporation rate. These findings might help to design nanoscale structures like nanopatterns or nanowires on surface through controlled solvent evaporation.

Controlled initial surge despite high drug fraction and high solubility

Potential connections between release profiles and solvent evaporation rates alongside polymer chemistry were elucidated for the release of tetracycline hydrochloride from two different poly (d, l-lactide-co-glycolide) (PLGA) film matrices containing high drug fractions (50%, 30%, and 15%), and prepared at two distinct solvent evaporation rates. At highest tetracycline concentrations (50%), (i) the early release rates were ≤0.5 μg/min in all cases; (ii) release was linear from systems fabricated with lower lactic content and slower solvent evaporation rate and bimodal from systems fabricated with higher lactic content and faster evaporation rate; (iii) surface fractions covered by the drug were similar at both evaporation rates for 85:15 PLGA but very different for 50:50 PLGA, leading to unexpectedly reduced early release from 50:50 PLGA than from 85:15 PLGA when both the matrices were fabricated using a slower evaporation rate. These features remained unaffected in case of low drug concentration. Results suggested that during the formation of the drug-polymer microstructure, the combined effect of polymer chemistry and solvent evaporation rate sets apart the surface characteristics and the initial release profiles of systems containing high drug fraction, and an appropriate combination of these parameters may be utilized to control the early stage of drug release.

Three-Dimensional Network of Cation-Cation-Bound Neptunyl(V) Squares: Synthesis and in Situ Raman Spectroscopy Studies.

Cation-cation interactions (CCIs) are an essential feature of actinyl chemistry, particularly neptunyl(V). To better understand the formation mechanisms of CCIs, the crystallization process of Np(V) CCI compounds has been explored during the evaporation of acidic Np(V) stock solutions using X-ray diffraction and both ex situ and in situ Raman spectroscopy. At least four Np solid products have been isolated from evaporation of the same Np(V) acidic solution. In situ evaporation using a continuous wave laser (532 nm) as a local heat source produced similar solid products to ex situ experiments with matching Raman signatures. The formation of these products is highly dependent on the evaporation conditions. Slower evaporation appears to favor the formation of a new neptunyl(V) compound, (NpO2)Cl(H2O)2 (1), over other solid products. The structure of 1 features a three-dimensional network of NpO2(+) cations, where neighboring Np(V) ions are only connected to each other through CCIs in a square arrangement. The O═Np═O stretching region shows similar Raman bands in both the solids and solution suggesting that CCIs between Np(V) cations exist prior to crystallization. These results provide new insight into the formation mechanism of Np(V) CCI compounds from solutions.

Effect of Vaporizer Temperature on Ambient Non-Refractory Submicron Aerosol Composition and Mass Spectra Measured by the Aerosol Mass Spectrometer

Aerodyne Aerosol Mass Spectrometers (AMS) are routinely operated with a constant vaporizer temperature (Tvap) of 600°C in order to facilitate quantitative detection of non-refractory submicron (NR-PM1) species. By analogy with other thermal desorption instruments, systematically varying Tvap may provide additional information regarding NR-PM1 chemical composition and relative volatility, and was explored during two ambient studies. The performance of the AMS generally and the functional integrity of the vaporizer were not negatively impacted during vaporizer temperature cycling (VTC) periods. NR-PM1 species signals change substantially as Tvap decreases with that change being consistent with previous relative volatility measurements: large decreases in lower volatility components (e.g., sulfate, organic aerosol [OA]) with little, if any, decrease in higher volatility components (e.g., nitrate, ammonium) as Tvap decreases. At Tvap < 600°C, slower evaporation was observed as a shift in particle time-of-flig...

The Concrete Protective Effect of Silane Impregnated Materials with Different Molecular Chain Structure

The concrete building protection materials is widely used in the hydraulic and bridge engineering. It was found that integral silane treatment can improve the durability of concrete.Compared with other protective methods, Silicone protect materials is the most convenient and environmentally-friendly.The silicone materials can effectively block the invasion of harmful substances such as water and chloride ions, and prevent the occurrence of the freeze-thaw damage. Few studies reported the protective effects of silane material which have different molecular structures .We found that Silane with relatively long molecular chain structure have a slower evaporation rate .When the concrete surface treated with such a silane material,the concrete surface has a 22% longer time to dry, so that the depth of penetration increased 16% for a longer concrete infiltration reaction time. we also studied the impact of temperature and humidity on the drying time of silane material , found using a suitable surface moisture conditions can get better protection.

Time-Dependent Solid-State Polymorphism of a Series of Donor–Acceptor Dyads

In order to exploit the use of favorable electrostatic interactions between aromatic units in directing the assembly of donor-acceptor (D-A) dyads, the present work examines the ability of conjugated aromatic D-A dyads with symmetric side chains to exhibit solid-state polymorphism as a function of time during the solid formation process. Four such dyads were synthesized and their packing in the solid-state from either slower (10-20 days) or faster (1-2 days) evaporation from solvent was investigated using single crystal X-ray analysis and powder X-ray diffraction. Two of the dyads exhibited tail-to-tail (A-A) packing upon slower evaporation from solvent and head-to-tail (D-A) packing upon faster evaporation from solvent. A combination of single crystal analysis and XRD patterns were used to create models wherein a packing model for the other two dyads is proposed. Our findings suggest that while side chain interactions in asymmetric aromatic dyads can play an important role in enforcing segregated D-A dyad assembly, slowly evaporating symmetrically substituted aromatic dyads allows for favorable electrostatic interactions between the aromatic moieties to facilitate the organization of the dyads in the solid-state.

Numerical study on spray and combustion characteristics of diesel and soy-based biodiesel in a CI engine

This study is to investigate spray, combustion and emission characteristics of mixtures of diesel and soy-based biodiesel in a CI engine. A surrogate mechanism is developed by combining the skeletal mechanisms of methyl butanoate and n-heptane. Thermophysical properties are validated against measured tip penetrations and Sauter mean diameters (SMDs) of nonreacting sprays. Biodiesel shows spray characteristics of larger SMD’s, lower volatility and slower mixing with ambient air due to larger viscosity and surface tension. Engine simulation is performed by the CMC-ISR model to resolve coupling between chemistry and turbulence. There is no noticeable difference in ignition delays of diesel and biodiesel, while flame propagates slower with slower evaporation and mixing for biodiesel. Results are in good agreement for pressure traces, NOx and trends of variation of CO and PM in a range of operating conditions. NOx decreased for BD<60% and increased for BD>60% with increasing biodiesel fraction, while PM and CO decreased due to the oxygen content in biodiesel in the test engine.

Inhalable sustained release rifampicin microparticles: preparation and evaluation of in vitro and in vivo deposition

To increase the local therapeutic effect and reduce the systemic side effects of rifampicin (RIF), an anti-tuberculosis drug, lung targeting was investigated in the present study. Poly lactide-co-glycolide (PLGA) microparticles containing RIF were prepared by spray-drying method, mixed with an equal volume of lactose monohydrate (LAC) and delivered to the lung as a dry powder inhaler (DPI). Various ratios of ethyl acetate (EA), and dichloromethane (DCM) were used as solvent throughout the microparticle preparation. The use of large fractions of EA resulted in a slower evaporation rate and led to the formation of more spherical microparticles. Furthermore, the density of the microparticles and process yield increased, and release rate was reduced. In vivo experiments showed that changing the solvent of PLGA 75:25 from pure DCM to DCM/EA 67:33 mixture resulted in altering the T max value from 36 to 48 h, C max from 0.53 to 0.43 μg/mL, and local drug concentration at 60 h from 406 to 612 μg/gram tissue.

Solvent and substrate effects on inkjet-printed dots and lines of silver nanoparticle colloids

The shape changes of inkjet-printed dots and lines were investigated by varying the primary solvent of nanosilver colloids, surface wettability and substrate temperature. The morphological changes in dots and lines in array patterns due to the interaction between neighboring dots or lines during evaporation was also examined for two different nanosilver colloids. In order to examine the effect of solvent evaporation rate, two different solvents with different boiling points (BP) were employed for nanosilver inks. With a fluorocarbon film coating and subsequent ultraviolet ozone (UV/O3) treatment, various surface wettability conditions were obtained on silicon (Si) wafers. Substrate temperature was varied from room temperature to 80 °C, and droplets from a 50 µm diameter nozzle were printed onto the substrate after optimizing the ejection of individual droplets. The results indicate that the shapes and sizes of dots and lines are sensitive to changes in both surface energy and substrate temperature, and the ink with a higher BP solvent produces larger dots under the same surface condition due to its slower evaporation. Dots and lines with better quality are achieved using the ink with a lower BP solvent. The morphological changes in dot and line arrays are dependent on the evaporation rate of the primary solvent as well as the distance between neighboring features. As a result, selecting a proper solvent for nanosilver ink is very crucial for controlling the shape and morphology of inkjet-printed patterns.

Transient heating of an evaporating droplet with presumed time evolution of its radius

New solutions to the heat conduction equation, describing transient heating of an evaporating droplet, are suggested, assuming that the time evolution of droplet radius Rd(t) is known. The initial droplet temperature is assumed to be constant or allowed to change with the distance from the droplet centre. Since Rd(t) depends on the time evolution of the droplet temperature, an iterative process is required. Firstly, the time evolution of Rd(t) is obtained using the conventional approach, when it remains constant during the timestep, but changes from one timestep to another. Then these values of Rd(t) are used in the new solutions to obtain updated values of the time evolution of the distribution of temperatures inside the droplet and on its surface. These new values of droplet temperature are used to update the function Rd(t). This process continues until convergence is achieved, which typically takes place after about 15 iterations. The results of these calculations are compared with the results obtained using the previously suggested approach when the droplet radius was assumed to be a linear function of time during individual timesteps for typical Diesel engine-like conditions. For sufficiently small timesteps the time evolutions of droplet temperatures and radii predicted by both approaches coincided. This suggests that both approaches are correct and valid. Similarly to the case when droplet radius is assumed to be a linear function of time during the timestep, the new solutions predict lower droplet temperature and slower evaporation when the effects of the reduction of Rd are taken into account. It is shown that in the case of constant droplet initial temperature, models both taking and not taking into account the changes in the initial droplet temperature with the distance from the droplet centre predict the same results. This indicates that both models are correct.

Device Performance and Polymer Layer Morphology in Polymer Bistable Device (PBD): The Control of Physicochemical Properties of Solvent

The surface morphology control of poly(N-vinyl carbazole) (PVK) layer for the improvement of polymer bistable devices (PBDs) performance was investigated based on the simultaneous consideration of the compatibility of polymer with solvent and the polymer ordering behavior during the solvent evaporation by introducing the bisolvent system of chloroform and 1,1,2,2-tetrachloro-ethane (TCE). It was confirmed by ultra violet (UV)-vis spectroscopy that PVK has significantly higher compatibility with chloroform than TCE. On the other hand, atomic force microscope (AFM) revealed that the chloroform/TCE = 9/1 bisolvent led to the improved film morphology (the surface roughness of 0.190 nm) than chloroform, because the presence of TCE representing slower evaporation rate contributed to the enhancement of PVK ordering and arrangement during the solvent evaporation for the film formation. The great correlation was made between the film morphology properties and I-V characteristics of PBDs. The PBDs with PVK layer cast from the chloroform/TCE = 9/1 bisolvent showed dramatically improved bistability characteristics (Vth approximately equal to 2 V and Ion/Ioff ratio > 10(3)).

Diffusion-Evaporation Studies of Binary Mixtures in Capillary Tubes

Evaporation in restricted domains, e.g. in capillaries, is of industrial importance but is poorly understood. Where the evaporating liquid is a binary mixture, preferential evaporation of the more volatile component occurs initially and the evaporation rate is not constant, indeed it appears to occur in stages. Experiments of evaporation from the entrance of a capillary were performed for various binary mixtures of acetone and water and for pure liquids for comparison. Measurements of mass were taken over time for a range of capillary diameters from 0.6 mm to 2 mm. For simplicity, the experiments were performed with the meniscus “stationary” at the entrance of the tube, rather than allowing the meniscus to recede. The data were analysed and showed that, for the binary mixtures, the evaporation process had two distinct stages for the mixtures. The second stage always had a lower slope than the first, indicating a slower evaporation (similar multistage evaporation processes have been observed for sessile drops of binary mixtures). There are many phenomena at work in this process: surface evaporation; diffusion (or natural convective mass transfer) in the air beyond the capillary; diffusion in the binary mixture; circulation in the liquid; thermal effects of evaporative cooling. These are investigated, comparisons made and further studies are proposed.

Molecular simulations of droplet evaporation by heat transfer

Droplet evaporation by heat transfer is investigated by molecular dynamics simulations for a pure Lennard-Jones fluid. Two different initial conditions are treated: (1) a droplet surrounded by its vapor in equilibrium, (2) a cold droplet surrounded by warm vapor. In both cases heat is transferred from a heat bath. Results are the numbers of droplet molecules N d and density, drift velocity, and temperature profiles as functions of time. For the small droplets considered N d depends on the definition of a droplet molecule. The density profiles as function of time show a transition from a droplet with liquid–vapor interface to a cluster of interfacial type and finally to the gas state. The temperature at a given time is nearly constant within the droplets or clusters but strong gradients occur in the gas. In case of evaporation of a cold droplet surrounded by warm vapor we observed initially cooling down of the droplet corresponding to pressure jump evaporation and thereafter slower evaporation because of lower initial state vapor density.

Ultrathin PMMA films spin-coated from toluene solutions

Films of atactic poly(methyl methacrylate) (PMMA) were produced by spin-coating from toluene solutions, and their properties were compared to similar PMMA films produced by spin-coating from chloroform [Walsh and Franses, Thin Solid Films 347 (1999) 167]. Two-angle ellipsometry at λ=6328 Å was used to probe the film thicknesses, refractive indices, and their overall quality and uniformity. Ellipsometry was also used with microspot optics at one angle to determine the film thickness uniformity. The films from toluene were approximately 4-fold thinner, but more uniform and of higher quality, than the films from chloroform, evidently because of the lower volatility and slower evaporation, of toluene. Films with thicknesses d 1=0.003 to 1 μm were produced for initial PMMA concentrations c=0.1–10 wt.%, and spinning speeds of 1000–3000 rpm. The thicknesses fit the equation d 1 (μm)=0.92 c 1.56 ω −0.51. The ω-dependence agrees with predictions of simple theoretical models. The results may find use in production of high-quality polymer films for resists or other applications.

Preparation of Inks with Monodisperse Colloidal Silica and their Self-Assembly in a Ink-Jet Printed Droplet

AbstractSemispherical self assemblies of colloids have been fabricated on a substrate using inkjet printing with an ink of submicron-sized monodisperse silica particles. Colloidal silica has been prepared by Stöber process. The shape and monodispersity of the synthesized colloidal particles were observed by scanning electron microscopy (SEM) and laser light scattering particle analyzer. Simple test patterns on various substrates (silicon wafer, Cu foil, and Mylar film) were printed with commercial HP printer. It was found that the uniformity and spatial extent of the self-assembled colloidal silica within a dot were significantly influenced by the contact angle between ink and substrates. Ink droplets printed on the hydrophobic Mylar film maintain a higher contact angle as compared to the hydrophilic substrates such as Si wafer. Slower evaporation and high capillary stress exerted on the ink droplet allow hemispherical colloidal aggregates with an ordered internal structure on Mylar film.