Spray Jet Research Articles

Effect of successive sprays on liquid distribution in fluidized beds

In processes such as Fluid Coking™, agglomerate formation should be minimized since it reduces the yield of valuable products, and degrades operability because of the fouling of internals. An experimental model, consisting of an aqueous solution of gum arabic with a dye, has been successfully developed to simulate the formation of agglomerates in the Fluid Coking™ process, where bitumen is sprayed into a fluidized bed of coke particles The particles wetted by a spray could be predicted by assuming that all the particles in the wake of bubbles formed from the tip of the spray jet have been wetted by the injected liquid. The transfer of liquid from particles wetted with the spray to dry bed particles was relatively ineffective, as the number of wet particles increased by only 50%. With successive liquid injections, the proportion of the liquid trapped in agglomerates increases in latter injections: large agglomerates from earlier injections accumulate above the grid and are carried by gas bubbles into the spray jet cavity, where they seed fresh agglomerates.

A device for harvesting and utilization of non-grain part of crop and fertilization

An effective method of harvesting grain crops using straw for fertilization, which can be carried out by installing a device on the harvester for spraying the crushed straw mass with a working liquid using a pneumatic slot sprayer designed in Kuban State Agrarian University. The device and the process of operation of this device with pneumatic slotted sprayers of working fluid are considered. Various parameters of sprayers have been studied: the air pressure supplied to the spray jet and the position of the equalizing tank that regulate the static pressure of fertilizers for setting the specified flow rate.

Structures of liquid jets in supersonic crossflows in a rectangular channel with an expansion section

The structures of liquid jets in supersonic crossflows (LJISC) are characterized by using high-speed photography and shadowgraph techniques. These flow structures substantially interfere with the atomization and mixing of the jet. Experimental studies on flow and spray fields are performed under various Mach numbers, injection positions, and injection angles. The results establish that (1) the evolution process of LJISC in the expansion section can be divided into three stages, namely, aerodynamic induced liquid column fracturing, expansion wave promoted spray accelerating, and compression wave disturbed spray blending, and (2) increasing the injection angle or the incoming Mach number effectively improves the penetration depth of the jet spray and enhances the gas–liquid mixing efficiency. However, the position of injection has little effect on the penetration depth. This research provides a critical and deep understanding about the atomization process of injection in an air-breathing engine with a combustion chamber with an expansion section.

Assessing Nozzle Geometry, Spacing and Height Effect on Pesticide Spray Characteristics and Swath from Ground and Aerial Sprayers

Nozzle is the basic aperture that controls pesticide spray jet onto targeted substrates. It is moulded from stainless steel, brass, ceramic and plastics at different wear rates. The efficiency of pesticide application is dependent on chemical efficacy and nozzle type. Both flat fan and hollow cone nozzles are commonly used to enhance pesticide spray characteristics and deposition. The surface coverage and spray distribution are influenced by nozzle spacing and spraying height. Therefore, using a nozzle type, spacing and spraying height that give pesticide spray-overlap is of interest to researchers. This review therefore analyses the effect of nozzle geometry, nozzle spacing and spraying height regimes on pesticide spray droplets characteristics from mechanical boom sprayers. To improve on uniformity of pesticides spray coverage on plant surfaces, a unitary relative span is reported suitable for application, but there had not been clearly defined nozzle type, spacing and height regime for effective spraying. The review further proposes an optimum parameters combination with specific nozzle type, spacing and spraying height for efficient application of pesticides.

Determination of blood glucose parameter from human blood serum by using a quartz crystal microbalance sensor coated with phthalocyanines compounds

Determining the blood glucose level is important for the prevention and treatment of diabetes mellitus. We developed a sensor system using Quartz Crystal Microbalance (QCM) to determine the blood glucose level from human blood serum. This study consists of two experimental stages: artificial glucose/pure water solution tests and human blood serum tests. In the first stage of the study, the QCM sensor with the highest performance was identified using artificial glucose solution concentrations. In the second stage of the study, human blood serum measurements were performed using QCM to determine blood glucose levels. QCM sensors were coated with phthalocyanines (Pcs) by jet spray method. The blood glucose values of 96 volunteers, which ranged from 71 mg/dL to 329 mg/dL, were recorded. As a result of the study, human glucose values were determined with an average error of 3.25%.

Effects of intake swirl on the fuel/air mixing and combustion performance in a lateral swirl combustion system for direct injection diesel engines

To study how intake swirl affects the combustion performance of the lateral swirl combustion system (LSCS), experiments under different swirl ratios were carried out in a single-cylinder diesel engine to optimize the circumferential injection angle (CIA) and test the eventual combustion performance. Then, simulation under different swirl ratios was conducted to reveal the influence mechanisms of intake swirl on the fuel/air mixing characteristics of the LSCS.Experimental results show that, as the swirl ratio (SR) was increased from 0 to 1.0, the optimal CIA increased 2.5° in the opposite direction to that of the intake swirl. Besides, the LSCS obtained better combustion performance with SR = 0 than with SR = 1.0, especially at high loads and low excess air coefficients. Simulation results indicate that, generating intake swirl weakens the wall-flow-guided and interferential interactions of the LSCS, thereby deteriorating the in-cylinder air utilization and fuel/air mixing uniformity, especially at high loads and low excess air coefficients, in which the interactions between the LSCS chamber and spray jets is strong due to the enhanced spray penetration ability. Therefore, the LSCS without intake swirl obtains the optimal fuel/air mixing and combustion performance in DI diesel engines.

Displacement speed statistics in an open turbulent jet spray flame

In this study, a three-dimensional Direct Numerical Simulation of an open turbulent jet spray flame has been used to investigate the statistical behaviour of displacement speed Sd and its components to provide physical explanations for the observed behaviours at different axial locations downstream of the jet exit. The open turbulent jet spray flame exhibits fuel-lean conditions close to the jet exit but fuel-rich conditions have been observed further downstream due to the evaporation of fuel droplets. For the axial locations considered, combustion takes place under low Damköhler number conditions. The displacement speed of reaction progress variable isosurfaces shows qualitatively similar behaviour for all axial locations considered – predominantly positive across the major part of the flame but with small, potentially negative, values towards the burned-gas-side. The components of displacement speed arising from chemical reaction rate and flame normal molecular diffusion remain leading order contributors and the competition between these determines the mean behaviour of displacement speed. These observations are consistent with studies of turbulent spray flames in canonical configurations and low Damköhler number turbulent premixed and stratified flames. This suggests that flow geometry in the absence of mean curvature might not be important in determining the mean behaviour of displacement speed and its components. Therefore, the modelling methodologies employed for turbulent stratified flames can potentially be extended for turbulent spray flames. However, the modelling methodologies, which implicitly assume equality between the surface-weighted values of density-weighted displacement speed and local laminar burning velocity, might be rendered invalid for turbulent spray flames.

Liquid jet breakup and spray formation with annular swirl air

Spray formation is important for liquid fuel combustion from the perspective of emissions and sustaining combustion. Employing swirl flow increases turbulent intensity, which leads to a much-desired outcome for sprays in a reduction of the jet breakup length, better air-fuel mixing and vaporization characteristics, and stabilizes the combustion operation. The present investigation endeavors to characterize the near field spray developing region of a swirl airblast atomizer. The high-speed digital imaging system is employed to record the unsteady dynamics when the liquid jet breaks to form mono-disperse or poly-disperse drop size distribution depending upon the atomizing air to liquid jet momentum ratio. The coherent spatial nature of the atomization process is identified using Proper Orthogonal Decomposition (POD) of acquired high-speed images of the spray in the near field. The simultaneous droplet size and velocities (axial, radial, and tangential) are measured through Phase Doppler Particle Analyzer (PDPA) technique to quantify the effect of the flow field on spray characteristics in the near field of an atomizer. Joint probability distributions of drop size and velocity along with Weber number distribution provide insight into the spray developing near field region. The spatial variations in the drop size distribution are found to be a function of turbulent Weber number (Wet) and shear Weber number (Wes) distribution. Double Gaussian function representing superimposed distributions for larger and smaller droplets provides the highest confidence fit for both velocity and dropsize distributions throughout the flow field. The volume-averaged statistics are proposed for a better description of the actual spray quality.

Investigation of post-injection strategies for diesel engine Catalyst Heating Operation using a vapor-liquid-equilibrium-based spray model

Most multidimensional engine simulations spend much time solving for non-equilibrium spray dynamics (atomization, collision, vaporization). However, their accuracy is limited by significant grid dependency, and the need for extensive calibration. This is critical for modeling cold-start diesel fuel post injections, which occur at low temperatures and pressures, far from typical model validation ranges. At the same time, resolving micron-scale spray phenomena would render full Eulerian multiphase calculations prohibitive. In this study, an improved phase equilibrium based approach was implemented and assessed for simulating diesel catalyst heating operation strategies. A phase equilibrium solver based on the model by Yue and Reitz [1] was implemented: a fully multiphase CFD solver is employed with an engineering-size engine grid, and fuel injection is modeled using the standard Lagrangian parcels approach. Mass and energy from the liquid parcels are released to the Eulerian multiphase mixture according to an equilibrium-based liquid jet model. An improved phase equilibrium solver was developed to handle large real-gas mixtures such as those from accurate chemical kinetics mechanisms. The liquid-jet model was improved such that momentum transfer to the Eulerian solver better reproduces the physical spray jet structure. Validation of liquid/vapor penetration predictions showed that the model yields accurate results with very limited tuning and low sensitivity to the few calibration constants. In-cylinder simulations of diesel catalyst heating operation strategies showed that capturing spray structure is paramount when short, transient injection pulses and low temperatures are present. Furthermore, the EP model provides improved predictions of post-injection spray structure and ignitability, while conventional spray modeling does not capture the increase of liquid penetration during the expansion stroke. Finally, the only important EP model calibration constant, Cliq, does not affect momentum transfer, but it changes the local charge cooling distribution through the local energy transfer, which makes it candidate to additional research. The results confirm that non-equilibrium spray processes do not need to be resolved in engineering simulations of high-pressure diesel sprays.

High pressure jet spray drying of condensed skim milk results in powders with enhanced interfacial properties

Abstract Condensed skim milk was processed through a continuous, custom-made high pressure jet spray dryer system (HPJ-SD) at 100–500 MPa. The resulting skim milk powders (SMPs) were evaluated for physiochemical and structural properties. The 500 MPa SMP exhibited increased particle density (1.48 g/cm3) compared to the ≤300 MPa SMP (1.33 g/cm3), but particle size analysis reflected no significant differences between these samples with D[4,3] values of 10.8 μ (100 SMP) and 12.2 μ (500 SMP). The 500 MPa SMP also had a reduced solubility and increased protein surface coverage compared to the 100 MPa SMP. The viscosity of the reconstituted HPJ-SD SMPs (9% w/w) increased from 2.3 mPa s (100 MPa) to 6.0 mPa s (500 MPa). The foam stability of the 500 MPa reconstituted SMP was exceptional with a foam head that remained stationary for 8 h (FVSI of 100%), while the foam in the 100 MPa reconstituted SMP diminished almost entirely in 2 h (FVSI of 21.3%). Evaluation of emulsification ability for reconstituted SMPs (1:9 oil in 2% diluted reconstitute w/w) revealed a 1.6-fold reduction in destabilization rate for the 500 MPa SMP compared to the 100 MPa SMP. HPJ-SD powders have physiochemical properties that can be utilized in a variety of clean label applications including ice cream or specialty beverages (e.g., cappuccino coffee).

Unveiling the importance of process parameters on droplet shrinkage and crystallization behaviors of easily crystalline material during spray drying

This study investigated droplet shrinkage and crystallization behaviors of easily crystalline mannitol model material. Different sized droplets were generated from feeds of different solid contents and dried into uniform microparticles via a microfluidic jet spray dryer. The droplet shrinkage behavior was characterized by comparing the size of dried microparticles and initially atomized droplets. Morphology and polymorphs of the microparticles were analyzed via SEM and XRD. Droplet shrinkage and crystallization behaviors were shown to be closing related to size, morphology, and polymorph of the spray dried microparticles. Droplets with small size or low solid content followed perfect shrinkage behavior, while droplets with larger sizes or higher solid contents demonstrated less shrinkage due to the earlier precipitation of a crust. Dense, partially hollow, or hollow spherical particles with different polymorphs (mixture of α- and β-mannitol or fully β-mannitol) were obtained depending on the process parameters, indicating the occurrence of different crystallization behaviors.

Ship hull slamming analysis with smoothed particle hydrodynamics method

In the marine and ocean engineering area, the water-entry process is a typical problem of fluid-solid interaction, which involves complex phenomenon such as the large deformation of free surface and considerable structure movement. In this process, the predicting impact load and summarizing the evolution law of the free surface deformation have important reference significance for the hull structure design. To address this issue, numerical simulations are carried out using a robust Smoothed Particle Hydrodynamics (SPH) model. The accuracy of the present SPH model is firstly validated by simulating the water entry of bow-flare section in two and three dimensions, respectively. Then, we investigate the variation characteristics of impact load and the evolution of free surface during the entry of the bow-flare ship section with different roll angles (θ=0∘∼20.3∘). Attention is focused on the flow separating phenomenon and the spray jet on the free surface. Finally, the water entry of a three dimensional ship hull is simulated. The velocity and pressure of flow field are analyzed and some conclusions are drawn.

Evolution of Surface Density Function in an Open Turbulent Jet Spray Flame

A three-dimensional Direct Numerical Simulation of an open turbulent jet spray flame representing a laboratory-scale burner configuration has been used to analyse the statistical behaviours of the magnitude of reaction progress variable gradient left| {nabla c} right| [alternatively known as the Surface Density Function (SDF)] and the strain rates, which affect its evolution. The flame has been found to exhibit fuel-lean combustion close to the jet exit, but fuel-rich conditions have been obtained further downstream due to the evaporation of fuel droplets, which leads to the reduction in the mean value of the SDF in the downstream direction. This change in mixture composition in the axial direction has implications on the statistical behaviours of the SDF and the strain rates affecting its evolution. The mean value of dilatation rate remains positive, whereas the mean normal strain rate assumes positive values where the effects of heat release are strong but becomes negative towards both unburned and burned gas sides. The mean values of dilatation rate, normal strain rate and tangential strain rate decrease downstream of the jet exit. However, the mean behaviours of displacement speed and its components do not change significantly away from the jet exit. The mean values of normal strain rate arising from flame propagation remain positive and thus act to thicken the flame. The mean tangential strain rate due to flame propagation (alternatively the curvature stretch rate) remains negative throughout the flame at all axial locations investigated. The mean effective normal strain rate assumes positive values throughout the flame and it increases in the downstream direction for the present case, which is consistent with the reduction in the peak mean value of the SDF in the axial direction. The mean effective tangential strain rate (alternatively stretch rate) assumes negative values throughout the flame at all axial locations.

Applications of electrostatic probes in fluidized beds

The electrostatic charge in a fluidized bed can be applied to provide local information on the bed hydrodynamics. Electrostatic probes can withstand adverse conditions that would be an issue for other measurement probes, such as high temperatures (limited by metal), high velocities (e.g. 2 m/s), high bed densities (1500 kg/m3), and large-scale equipment. The objective of this study was to investigate various applications of electrostatic probes in fluidized beds.Results obtained with an array of 45 probes arranged in 5 rows provided the local bubble gas flux and bubble velocity. They could also be used to detect any slugging. When liquid was sprayed into the gas-fluidized bed, the electrostatic probes could provide the penetration of the gas-liquid spray jet, detect bogging and measure the free moisture, i.e. the amount of liquid that was not trapped within wet agglomerates. The electrostatic probes measurements were validated with alternate measurement methods.

Determination of an Optimal Oil Jet Nozzle Layout for Helical Gear Lubrication: Mathematical Modeling, Numerical Simulation, and Experimental Validation

To provide a basic guidance for the selection of nozzle layout, a mathematical model of the impingement depth for helical gears under oil jet lubrication is established. Furthermore, computational fluid dynamics (CFD) methods are adopted to validate the effectiveness and accuracy of the derived impingement model. Firstly, the distribution characteristics of the oil volume fraction and oil-gas pressure in meshing area were obtained in flow field simulation. Meanwhile, the influence of spray angle, jet velocity, and gear ratio on lubrication effect was obtained. Then, the transient temperature field of the tooth surface was simulated by the method of thermal-fluid coupling analysis, and the lowest temperature distribution and the corresponding oil jet velocity were determined. Finally, experiments on the temperature characteristics measured by an infrared thermal imager of helical gears with different nozzle parameters were carried out in a gear test rig. The simulation results of transient temperature field are in good agreement with those obtained by experiments, and it indicates that the thermal-fluid coupling analysis method is correct and feasible to predict the temperature field of the helical gear pair under oil injection jet lubrication.

Theoretical analysis on the atomization characteristics of liquid nitrogen jets

Atomization with cryogenic fluids is complicated due to the combined effects of both the mechanical breakup and thermodynamic flashing. However, the weight of the two effects on the atomization has not been determined yet. This paper proposes a hybrid mathematical model to evaluate the weight of the thermodynamic effect and aerodynamic effect. The entire process of jet spray breakup, including the primary breakup and secondary atomization, is described in the model. A linear stability analysis is carried out using the dispersion equations for the primary breakup. In the secondary atomization, the Taylor analogy breakup and bubble micro-explosion models are employed to study aerodynamic and thermodynamic effects on the atomization, respectively. The homogeneous nucleation is implemented in the bubble micro-explosion models. A criterion is obtained which can be evaluated to predict the dominant effect. Accordingly, the influence of factors such as ambient pressure and other physical parameters on the atomization process is analyzed. The results reveal that, under low ambient pressure, thermodynamic flashing is stronger. Besides, the mechanical action is restrained when the surface tension is increased.

Estimation of Particle Mass Flow Rate in Free Jet Using In-Flight Particle Diagnostics in Plasma Spraying

In-flight particle diagnostics have enhanced our understanding of thermal spraying and improved coating reproducibility. However, no methodology to verify the measured in-flight particle properties has been proposed in the literature yet. This methodology requires describing the entire free jet from accurate measured values. This study deals with a novel method to verify the measured in-flight particle sizes and velocities by estimating the particle mass flow rate (PMFR) in the free jet. To this end, the entire free jet cross section was divided into several non-overlapping focal planes, and the size and velocity of the in-flight particles were measured by optical diagnostics at these focal planes. The PMFR of the powder feeder was used as a reference to validate the determined PMFR in the free jet. The results showed a good agreement with the PMFR of the powder feeder and could be replicated with different feedstock powders, demonstrating the capability of the developed method. Furthermore, the determined PMFR distribution in the entire free jet, referred to as digital footprint, agreed well with the height of the experimental footprints of the spray jet on a substrate. Consequently, it can be concluded that the spatial PMFR distribution was also properly measured.

Atomization and evaporation process of liquid fuel jets in crossflows: A numerical study using Eulerian/Lagrangian method

Liquid fuel atomization in transverse uniform gaseous flow, i.e., crossflow, is widely utilized in aircraft engines and is considered an important aspect for engine development. The atomization-evaporation process of liquid fuel jet spray in the vicinity of a nozzle in crossflows is investigated by a detailed numerical simulation using an Eulerian/Lagrangian framework. The Eulerian framework is applied for each gas and liquid continuum fluid phase, whereas the Lagrangian framework is applied for the dispersed droplets generated by the atomization process. To capture the gas-liquid interface with an accurate surface tension in the Eulerian framework, a coupled Levelset and volume-of-fluid (CLSVOF) method is used. The evaporation of Lagrangian droplets is considered by a non-equilibrium Langmuir-Knudsen evaporation model. The results show that the trends of the jet trajectory and primary breakup behavior of liquid column are well captured and in good agreements with the previous experimental and analytical studies. The aerodynamic Weber number significantly influences the primary breakup behavior and the vortex development and morphology behind the liquid column, which tends to drastically change the evaporation process as well.

Experimental study on erosion initiation via liquid droplet impingement on smooth and rough walls

This paper presents an experimental study on erosion initiation via liquid droplet impingement on smooth and rough aluminum (A1070) walls. Experiments were conducted using a spray jet apparatus with three different orifice diameters at various nozzle pressures, which facilitated the variation of droplet characteristics, such as droplet velocity and diameter, which were measured using particle image velocimetry and a shadowgraph imaging technique, respectively. Experimental results are presented for the incubation period based on the spray flow rate, droplet diameter, impact velocity, and surface roughness. It was determined that the incubation period decreases with increasing impact velocity and surface roughness, while droplet diameter has a relatively minor effect on the incubation period. Furthermore, the incubation period based on the impact velocity and surface roughness is defined by an empirical equation for prediction. Scanning electron microscopy observations of erosion initiation on the rough walls reveal that erosion damage was initiated along crystal grain boundaries on the smooth wall, but much larger pits were generated on the rough surface based on the stress concentration effects of the roughness.

Experimental and 3-D Numerical Heat Transfer Analyses of Dual Spray Water Nozzle Impingement on a Flat Plate

Spray impingement cooling is the major method currently used to cool steel after the hot-rolling process. In this study, dual nozzles are used to investigate the cooling character of the flat plate using for the spray impingement cooling process. Based on an experimental temperature measurement, a three-dimensional numerical model is set up to calculate the transient heat transfer coefficient of the cooling plate by solving the inverse heat conduction problem with the conjugate gradient method. Both the experimental and numerical results indicated that an interference region appeared between the two jet spray impingement regions. The interference pitch varied with the flow rates, the height from the plane to the jet outlet, and the distance between the two jets. As water spread over the plate, the heat dissipation region gradually stretched from the impingement region to the interference and flow regions. A peak in the heat flux curve was observed when the water arrived at the wet front of the flow. Meanwhile, the peak in the heat flux decreased as the distance from the impingement region increased. A maximum local heat transfer coefficient 23,000 W/(m2K) was observed in this experiment. The global average heat transfer coefficient increased with increases in the water flow rate, but it decreased with increases in the pitch.