Atomization Characteristics Research Articles

Atomization and evaporation characteristics of liquid ammonia spray under engine intake stroke conditions

Atomization and evaporation characteristics of liquid ammonia spray under engine intake stroke conditions

Secondary atomization characteristics of coal water paste

Secondary atomization characteristics of coal water paste

Searching for signatures of Fe II atomic processes in spectra of active galactic nuclei

We use a large sample of Type 1 active galactic nuclei (AGNs) spectra in order to investigate which atomic processes are responsible for some observed properties of the Fe II emission lines and how they are connected with macroscopic physical characteristics of AGN emission regions. We especially focus on the violated relative intensities between different optical Fe II lines, whose relative strengths do not follow the expected values according to atomic parameters. We investigated the connection between this effect and the ratio of optical to UV Fe II lines (Fe II_opt/Fe II_UV). We divided the optical Fe II lines into two large line groups: consistent (Fe II_cons), whose relative intensities are in accordance with their atomic properties, and inconsistent (Fe II_incons), whose relative intensities are significantly stronger than theoretically expected. We fitted the spectra with a flexible and complex optical Fe II model, where both consistent and inconsistent Fe II lines were divided into several line groups according to their atomic characteristics and fitted independently in order to obtain more empirical clues about their properties. We focused particularly on understanding the processes that produce strong inconsistent Fe II lines, and therefore, we investigated their correlations with Fe II_cons as well as with UV Fe II lines and some measured spectral parameters. The ratios of Fe II_incons/Fe II_cons and Fe II_opt/Fe II_UV increase as the Eddington ratio increases and as the line widths decrease. It is possible that both ratios are affected by the process of self-absorption of stronger lines, which is responsible for the transmission of energy from the UV to the optical Fe II emission lines and, analogously, from the Fe II_cons to the Fe II_incons lines. In this scenario, the high Eddington ratio causes an increase in the optical depth in Fe II lines, which results in the triggering of the process of self-absorption. Measured average widths for different Fe II line groups indicate the stratification of the optical Fe II emission region. This implies that the observed Fe II spectrum is probably a complex mixture of radiation from emission regions with different physical conditions and distances from the black hole.

Assessment of an effervescent breakup model for Lagrangian simulations of real fuel sprays

Flash boiling drastically alters the characteristics of spray atomization and plume structure, which could impose challenges for modern propulsion systems design regarding fuel/air mixture formation and emission performances. Numerical simulations serve as effective tools to understand and predict flash boiling sprays for modern engine applications. This study carried out Eulerian-Lagrangian spray simulation campaigns for two gasoline injectors, and realistic single-composite and multi-component fuel models were used instead of simple surrogates. A validated effervescent breakup model was adopted to account for the non-trivial breakup mechanism induced by bubble nucleation within the liquid droplets. Effects of key model parameters were discussed in detail to propose a consistent set of model constants, and comprehensive validation was achieved against near- and far-field spray experiments. The effervescent breakup model has demonstrated satisfactory effectiveness, and the numerical findings also highlight the necessity of employing real fuel properties for spray analysis.

Number Count Characteristics of Cold Atoms in a Magnetic Trap for Temperature Estimation

Number Count Characteristics of Cold Atoms in a Magnetic Trap for Temperature Estimation

Effect of Using Types and Concentrations of Ureolytic Bacteria on Flexural Capacity of High-Strength Concrete with Self-Healing Concrete Capabilities

Abstract Concrete’s deflection and cracking are influenced by flexural capacity. High-strength concrete tends to have high hydration rate, making it susceptible to microcracks, thus, early maintenance is required. The weak nature of concrete against tensile forces allows microcracks to occur and can propagate into macrocracks if the cracks are not detected. Therefore, an innovation emerged called self-healing concrete enabling concrete to cover microcracks independently. This method can be used to heal concrete cracks, involving bacteria in concrete mixture that are active when cracks occur by producing calcite (CaCO3) to close the cracks. In this study, ureolytic bacteria of genus Bacillus sp., Staphylococcus sp., and Solibacillus sp. were used. Specimen used was beam with dimensions of 400mmx100mmx100mm, which was strengthened with 1D10 mm tensile reinforcement to prevent brittle collapse of beam. Variations in bacterial mixture used were 0%; 0.5%; 0.6%; and 0.7% of the cement weight which encapsulated in diatomaceous earth altogether with urea and Ca2+ as precursors and nutrient broth as bacterial nutrients. Encapsulation pellet dosage was 10% from fine aggregate weight. At initial testing stage, cracking load amounting 70% of 7 days non-bacterial concrete flexural tensile strength was imposed to give initial cracks to concrete, then, treatment was conducted for 28 days by immersion in water to visually observe the self-healing process of calcite growth (CaCO3) for 7, 14, 21 and 28 days. After accomplishing crack healing process, ultimate flexural tensile strength testing was performed. The highest average flexural capacity results were obtained in high-strength concrete with 0.6% Bacillus sp. bacteria of 6.34 ton with an average calcite length of 41.00 mm. To analyse atomic structure characteristics of bacterial concrete, XRD testing was carried out and the results showed that bacterial concrete of Bacillus sp. had the highest percentage of amorphous phase, i.e., 82.63%, and contained 33.66% calcite compounds.

Experimental study on ignition characteristic and performance of a two-stroke engine fueled with aviation kerosene

Two-stroke spark ignition engines are widely used in Unmanned Aerial Vehicles. Aviation kerosene offers advantages over aviation gasoline due to its higher flash point and lower volatility, making it likely to be adopted more widely in the future. However, the poor evaporation and atomization characteristics of aviation kerosene result in suboptimal ignition performance, especially in the engine start-up phase. To explore the fitting mixture concentration and temperature conditions for achieving better ignition performance of aviation kerosene, A series of experimental studies are conducted on a two-stroke engine. The intrinsic factors affecting engine performance are analyzed. The experimental results indicate that optimal ignition characteristics, maximum power output, and a reduced misfire rate can be achieved at mixture concentration of 0.6 and mixture temperature of 80?C. Furthermore, the misfire rate is most sensitive to the combustion duration, while the cyclic variations show significant sensitivity to ignition delay. The results provide guidance for optimizing ignition performance during the start-up phase of two-stroke engines fueled with aviation kerosene.

Effects of Temperature and Injector Structure on Atomization Characteristics of Bipropellant – Experimental Study

Effects of Temperature and Injector Structure on Atomization Characteristics of Bipropellant – Experimental Study

SchNet_IIA: Potential Energy Surface Fitting by Interatomic Interactions Attention Based on Transfer Learning Analysis.

Machine learning methods for fitting potential energy surfaces and molecular dynamics simulations are becoming increasingly popular due to their potentially high accuracy and savings in computational resources. However, existing application models often rely on basic architectures like artificial neural networks (ANNs) and multilayer perceptron (MLP), lagging behind cutting-edge technologies in the machine learning domain. Furthermore, the complexity of current machine learning frameworks leads to reduced interpretability and challenges for improvement. Herein, we developed a model analysis method based on the feature-representation-transfer approach to directly perform causal analysis on the model. The internal action characteristics of the SchNet framework were successfully analyzed by constructing different source tasks and we proposed interatomic interactions attention for the characterization of doped clusters. The accuracy was enhanced by 0.015 eV/atom compared to the original model. The ability to capture atomic environment characteristics was significantly improved. The activation function was smoothed resulting in a 23.47% increase in the convergence speed. Our SchNet_IIA model demonstrates superior performance in capturing interatomic interactions. Our present work is of distinctive value as it presents a novel transfer learning analysis method with the potential to evolve into a generalized model analysis approach, providing new perspectives and solutions for the field.

Unveiling the Critical Role of High/Low‐Index Facets in Nanostructured Energy Materials for Enhancing the Photoelectrochemical Water Splitting

The surface properties of nanostructured materials, especially the role of facets, have emerged as a central focus in improving photoelectrochemical (PEC) performance. High/Low‐index facets in semiconductor nanostructures feature unique atomic structures, chemical reactivity, and electronic characteristics, critically influencing light absorption, charge separation, and catalytic activity, significantly enhancing the PEC efficiency. High‐index facets, distinguished by distinct atomic structures, generally demonstrate enhanced catalytic activity owing to their higher surface energy and increased density of reactive sites. However, they tend to be less stable compared to low‐index facets. In contrast, low‐index facets offer better thermodynamic stability but may have reduced catalytic activity. Achieving the balance between these properties is critical for designing materials that maximize performance and durability in PEC water‐splitting applications. Recent developments in synthetic techniques, including hydrothermal/solvothermal procedures and epitaxial growth, have facilitated precise control over the exposure of specific facets, allowing for the customization of nanostructured materials to optimize efficiency. This review paper comprehensively analyzes the faceted materials and their diverse methodologies for synthesis, modification, and transformation of geometrical arrangements into facets of various semiconductor materials. A deeper understanding of crystal‐facet engineering in crystals with tailored configurations has revealed substantial potential for the systematic design and synthesis of advanced micro‐/nanostructures.

Optimization Design and Atomization Performance of a Multi-Disc Centrifugal Nozzle for Unmanned Aerial Vehicle Sprayer

The nozzle is a crucial component in unmanned aerial vehicle (UAV) sprayers. The centrifugal nozzle offers unique advantages; however, there is a scarcity of published research regarding the structural parameters, spraying parameters, and practical applications specifically for UAV spraying. Furthermore, there is a need for UAV-specific nozzles that demonstrate high efficiency and excellent atomization performance. In this present study, a multi-disc centrifugal nozzle (MCN) capable of controlling droplet size was designed and optimized. The droplet size spectra with different atomizing discs were tested, and indoor and field tests were conducted to investigate the atomization and spray deposition characteristics of the MCN. It was found that the MCN with six atomizing discs with a curved groove, a disc angle of 120°, and a disc diameter of 77 mm demonstrated better atomizing performance. The volume median diameter was 96–153 μm, and the relative span was 1.0–1.3. Compared with the conventional hydraulic nozzle, this nozzle increased the effective spray swath width from 2.5–3.0 m to 4.0–5.0 m and promoted the average deposition rate by 132.4% at a flying height of 1.0 m and a flying speed of 3.0 m/s, which tends to raise the operation efficiency by four to five times. This study can provide a reference for the design and optimization of centrifugal nozzles for a UAV sprayer and the selection of operating parameters in aerial spraying operations.

Einstein frequency of individual chalcogen bonds in Cu(In,Ga)Se2 and Cu(In,Ga)S2: Indicator of diffusion property of Cu, In, and Ga atoms

Elucidating the characteristics of the Cu-Se, In-Se, and Ga-Se bonds in chalcopyrite-type Cu(In,Ga)Se2-based semiconductors can aid the design and fabrication of highly efficient thin-film photovoltaic devices. In this study, we used extended X-ray absorption fine structure (EXAFS) analyses to evaluate the characteristics of chemical bonds in Cu(In,Ga)Se2 and Cu(In,Ga)S2 powder samples at low temperatures (10–300 K). The temperature dependence of the structural and vibrational disorder (Debye–Waller factor) provides the Einstein temperature of an individual bond in Cu(In,Ga)Se2-based materials. The analyzed Einstein temperature, which is proportional to the Einstein frequency, increased in the order of Cu–Se(S) < In–Se(S) ≤ Ga–Se(S), and the S-containing bond had a higher Einstein temperature than the corresponding Se-containing one. We also analyzed the effect of the Ga/(Ga + In) ratio on the Einstein temperature of each chemical bond. The force constant of the oscillator (i.e., the bond) was determined from the Einstein frequency using the reduced mass of the constituent atoms. The obtained bond properties were found to correlate with the diffusion characteristics of the constituent atoms in CuInSe2-based solar cell materials.

Assessing the potential spray drift of a six-rotor unmanned aerial vehicle sprayer using a test bench and airborne drift collectors under low wind velocities: impact of atomization characteristics and application parameters.

The unmanned aerial spraying systems (UASS) have gained widespread use for plant protection in recent years. However, spray drift from UASS is a major concern when controlling weeds over large areas and warrants a thorough investigation. This study examined the atomization characteristics of the herbicide florpyrauxifen-benzyl under downwash airflow using a UASS spray test platform. Potential spray drift was assessed using a test bench (TB) and airborne drift collectors (ADCs) in the field under low wind speeds (<1 m s-1). Atomization characteristics were significantly affected by the spray liquid, adjuvant, nozzle type and spray pressure. The addition of an adjuvant reduced the liquid sheet length, improved physicochemical properties and increased droplet size under the downwash airflow field. Drift evaluation in the field using the TB revealed that sediment spray drift predominantly occurred from the middle to the entire length of the device when fine-to-medium droplets were produced after the sprayer passed. ADC assessment found that higher flight altitudes and finer droplets resulted in higher drift values, whereas the addition of an adjuvant and the use of an air-induction nozzle reduced drift <3 m aboveground. The combination of using TB in the target area and ADCs in the off-target area as an alternative method to determine residual droplets in the current airflow provided valuable insights into airborne drift assessment for UASS. © 2024 Society of Chemical Industry.

Experimental investigation of the atomization characteristics of pre-filming atomizer with low-temperature fuel

Pre-filming atomizers are used in low pollution center staged combustion chambers, which face high-altitude and low-temperature ignition problems during the operation of aircraft engines. By using a pre-filming atomizer, a thin liquid sheet is formed on the plate and encounters a high-velocity swirling airstream which lead to the atomization of the fuel. In this study, an experimental investigation was conducted to explore the flow characteristics and atomization characteristics of a pre-filming atomizer with low-temperature fuel. The dynamic process of the fuel atomization in the pre-filming atomizer was measured, and the fluctuation frequency, breakup length of the liquid film surface, and the spray particle size in the secondary atomization area were obtained. The results demonstrate that the atomizer flow number increases with a reduction in fuel temperature, attributed to the increased fuel density and mitigated cavitation effects. Concurrently, as the fuel temperature decreases, the surface fluctuation frequency of liquid film diminishes due to the heightened surface tension and internal viscosity of the fuel. The aerodynamic shear force reduces as the relative velocity between the fuel and air flow decreases, leading to an extended average liquid film breakup length. And the spray particle size generated in the secondary atomization area increases slightly due to the relatively minor impact of fuel temperature on atomization characteristics compared to the dominant role of aerodynamic forces. Finally, the fuel temperature mainly affects the atomization characteristics of the pre-filming atomizer by the physical properties and fuel flow rate, which is primarily represented under small air flow conditions.

Investigation of internal flow and mixing characteristics in dual-orifice atomizers

Dual-orifice atomizers have been developed to overcome the limitations of simplex atomizers—where “simplex” refers to having only a single flow channel—which cannot adjust flow rates over a wide range. This study explores the internal flow and mixing characteristics of dual-orifice atomizers using the Volume of Fluid method. The effects of four key parameters—primary post thickness, primary recess length, secondary swirl number, and mass flow rate ratio—on flow dynamics and atomizer performance, particularly exit film thickness and spray cone angle, are investigated. The results reveal that, before mixing, the low-pressure region created by the swirling flow inside the secondary nozzle increases the primary flow angle and reduces the thickness of the primary liquid film. After mixing, the velocity difference between the primary and secondary flows enhances atomization by promoting greater instability. The impingement position of the primary liquid film is influenced by recess and the low-pressure region inside the secondary nozzle, with longer recess lengths shifting the impingement point upstream. Increases in secondary swirl number, mass flow rate ratio, and primary post thickness further enlarge the low-pressure region, causing the impingement point to move upstream. The mixing regime is defined by the impingement position, with tip mixing creating velocity stratification that increases the instability. The performance of dual-orifice atomizers depends on the impingement position, resulting mixing regime, and secondary flow's swirl intensity. These findings provide valuable insights for optimizing atomizer design to improve performance.

Effects of pre-injection parameters on spray characteristics of high-pressure common rail diesel engines

A verified hydrodynamic spray model was used to investigate the effects of multiple injection strategies on fuel bundle development and atomization characteristics of diesel fuel under typical conditions of direct-injection, turbocharged, and high-speed automotive diesel engines. Emphasis is placed on the effect of injecting a small amount of pre-injection fuel prior to the main injection on the spray development process. In addition, the effect and degree of influence of pre/main-injection interval time and pre-injection fuel ratio on spray macro- and micro-parameters in the two-injection strategies. The results show that at the end of the injection process, as the pre/main-injection interval time increases, the spray gas phase penetration distance increases, the spray width and the spray volume of the high-temperature region decrease, and the fuel concentration in the vicinity of the nozzle is in a decreasing trend. As the pre-injection ratio increases, the spray gas phase penetration distance decreases, the spray width, the spray volume of the high-temperature region increases, the spray volume between the fuel equivalence ratio of 0.8–1.2 decreases, and the fuel concentration at the front end of the spray tends to increase. The effect of the proportion of pre-injection fuel on spray width, spray volume of the high-temperature region, and spray volume between the fuel equivalence ratio of 0.8–1.2 was 4.88, 4.56, and 11.5 times that of changing the pre/main-injection interval time, respectively. The research provides a basis for optimizing the injection strategy and applying multiple injection technology in high-pressure common rail diesel engines.

Influence of adjacent nozzles on flow and fuel atomization characteristics of the central nozzle in a triple-nozzle combustor

This paper examined the influence of adjacent nozzles on the flow and fuel atomization characteristics of the central nozzle in a triple-nozzle model combustor. High-frequency particle imaging velocimetry testing for airflow and phase Doppler particle analyzer testing for fuel particles were employed. Under the central nozzle air intake mode, the momentum exchange between the swirling flow and the surrounding stationary air leads to a seemingly shrinking flow field. While under the triple nozzles air intake mode, the low static pressure at the geometric center between adjacent nozzles attracts the swirling flows to converge, resulting in a larger expansion angle. Confinement has a complex impact on swirling flow. When the angle of the swirling airflow is small, it guides the flow to expand. However, when the angle becomes too large, it restricts further expansion. Observed Sauter mean diameter (SMD) peaks for the tested cases lie within a similar range, suggesting comparable spray angles. Nevertheless, the triple-nozzle air intake mode exhibits consistently higher SMD values and significantly greater spray core penetration depth. Instantaneous flow characteristics deepen the understanding of these differences in atomization results. The large range of airflow oscillation under the central nozzle air intake mode allows the airflow to directly interact with the droplets. While under the triple-nozzle air intake mode, the air flow path is too far away from the spray, resulting in that most droplets do not receive sufficient aerodynamic forces for atomization.

Experimental and numerical investigation of spray characteristics of gas–liquid swirl coaxial injectors

To investigate the velocity distribution and atomization characteristics of gas–liquid swirl coaxial (GLSC) injectors, atomization experiments and simulations were conducted under atmospheric conditions. The velocity distribution and morphology of the spray from GLSC injectors at varying gas–liquid ratios were measured using particle image velocimetry. The gas–liquid interaction, breakup dynamics, and the velocity of liquid sheet were simulated based on the three-dimensional volume of fluid to discrete particle model (VOF-to-DPM) and octree adaptive mesh refinement. Additionally, a method for extracting droplet diameters from high-quality images has been developed and validated. The results indicate that the sprays maintain a stable cone when the gas–liquid ratio is low. As the gas–liquid ratio increases, particularly at larger recess ratios, self-pulsation phenomena occur. During self-pulsation, the spray cone angle is enlarged, and the breakup length shortens. In a stable spray field, the center exhibits a low velocity region (5–10 m/s), while the spray periphery shows a high velocity region (20–25 m/s). Self-pulsation is induced by the “Klystron effect,” which arises from the Kelvin–Helmholtz (K–H) instability at the gas–liquid interface. The center of the self-pulsated spray transitions to a high velocity region due to the accelerated droplet motion driven by the annular gas flow through the spray's center. The radial distribution of mean droplet diameters for both stable and self-pulsated sprays has been summarized. As the gas–liquid ratios and recess ratios increase, the global droplet diameters gradually decrease, with a 75% of droplet diameters falling between 0 and 0.1 mm.

Analysis of atomization characteristics in submerged top-blowing with a swirling spray lance

Analysis of atomization characteristics in submerged top-blowing with a swirling spray lance

Experimental investigation of the characteristics of direct injection nozzle sprays in an afterburner environment

This study examined the atomization characteristics of direct injection nozzles under high-temperature, large-Mach inflow conditions using a high-speed camera. The effect of inflow conditions on fuel breakup length, fuel concentration field, and particle size spatial distribution was quantitatively analyzed by using image processing techniques. Experimental results indicate the following: 1) When the liquid-to-gas momentum ratio and inflow Mach number (Ma) are equal, the breakup length, fuel field boundary, and droplet distribution in the jet core region remain consistent for the same nozzle under room-temperature air and high-temperature gas conditions. 2) A breakup length model based on the breakup time of the liquid column is proposed. 3) The logarithmic fuel trajectory formula can effectively predict the physical phenomenon of the movement of fuel particles with the gaseous flow downstream of the injection point after their kinetic energy is depleted, with a prediction error of no >10 %. 4) The spatial distribution of particle sizes reveals that within the selected range of liquid-phase jet velocity, the distribution range of the Sauter mean diameter (SMD) of the jet core area in gas-flow environments with large Ma is similar. At the same axial position, a positive correlation exists between SMD and nozzle diameter. The results of this study have guiding importance for the design of integrated afterburner nozzles.