Mixing Nozzle Research Articles

Spray characteristics of steam-assisted oil atomization in Y-jet nozzles

Twin-fluid atomizers, valued for handling viscous fluids and high operating loads, are extensively used in combustion processes and oil refineries. In the latter scenario, internal mixing nozzles are employed in fluid catalytic cracking units for oil dispersion using steam as the dispersing medium. While steam-assisted atomization studies often focus on flue gas analysis, the associated steam/oil internal mixing process and the spray droplet dynamics lack proper investigation. Accordingly, this work explores the Y-jet nozzle performance for oil atomization using steam, aiming to determine favorable conditions for obtaining a stable spray with fine droplet distribution. This analysis is accomplished by characterizing the mixing chamber pressure, investigating the spray boundary instabilities using high-speed images, and exploring the spray droplet size using the shadowgraphy technique. Work relevance relies on performing experiments at industrially representative conditions, characterized by the similarity of important dimensionless numbers. Additionally, the nozzle design is optimized by varying key geometric parameters. The nozzle geometry and the operating condition impact on the steam-assisted atomization performance and spray behavior constitutes the main findings of this work. The outcomes highlight the relevance of the fluid dynamics investigation for optimized nozzle performance, involving a balance between spray stability and fine droplet distribution generation.

Experimental and Numerical Simulation Studies on the Atomization Characteristics of the Internal Mixing Nozzle and Its Field Application

Experimental and Numerical Simulation Studies on the Atomization Characteristics of the Internal Mixing Nozzle and Its Field Application

Complex concrete elements for the production of recyclable formwork by extrusion and milling

AbstractThe paper presents an additive process for the sustainable production of a recyclable formwork system based on concrete extrusion and milling, which allows the resource‐efficient production of complex precast concrete parts. Within the framework of research work, concrete formulations were developed and characterized, which are produced close to the final contour by means of extrusion and then brought into the final form by means of high‐precision machining. The resulting mould is used for the production of precast concrete parts. In order to increase the complexity of the components while further saving material, a forced mixing nozzle was designed which allows admixtures to be added shortly before the concrete is extruded. The integration of a concrete setting accelerator allows the production of higher overhangs of the components. The faster solidification of the concrete also reduces the printing time and the amount of material required, because the higher stability eliminates the need for individual support structures. After use as formwork, the recycling process continues, and the recycled material will be added back to the printing process. The development of the new near‐net‐shape technology is key for the success of efficient sustainable production of concrete components.

CFD Simulation Study for Abrasive Waste Management Using Water Eductors for Abrasive Waterjet Cutting Collector Tanks

The work is mainly aimed at solving technical problems in the field of unconventional fluid-jet processing, a field in which ISIM Timisoara has developed technical and technological expertise. A crucial part of an effective cleanup process is the secure transportation and disposal of sludge-type materials and related clean-up waste in the industry to a designated site and then to waste treatment plants, as ecological regulations continue to evolve. As a result, experts strive to discover the most state of the art and effective methods for storing and cleaning produced waste.The technical solution studied in this paper consists in obtaining an efficient system for the evacuation of the waste water and abrasive mixture, elements generated during abrasive waterjet cutting, in the shortest time, without stopping the technological cutting process.In this sense, a water eductor system is studied, by carrying out a preliminary experimental program, for use in abrasive waterjet installations collector tanks, by CFD simulation process.The operating parameters of eductor-type mixing nozzles and their effect on the liquid abrasive mixture in a tank of an abrasive-water jet cutting system were analysed.

Sequential fixed-fluidized bed foam granulation (SFFBFG) and drying: Multivariate model development for water content monitoring with near–infrared spectroscopy

Foam granulation (FG) is a non-conventional technique in which a binding solution is sprayed as aqueous foam. The main objectives of this work are, converting a lab-scale fluidized bed dryer into a fluidized bed foam granulator and dryer. Second, developing a partial least squares regression model for monitoring granules water content during this process, and third, bringing forward sufficient evidence of the fluidized bed foam granulation process feasibility. In this work, a mini-Glatt fluidized bed apparatus was used and aqueous foam was produced through an internal mixing nozzle located above the static powder bed, which is fluidized after foam dispensing. A micro-NIR probe was inserted across the powder container and gather spectral data during granulation and drying. The calibration model was built using the spectral data by Random Subset Cross-Validation and validated externally. Concerning the results, an Rcal2 and RMSECV of 0.945 and 1.67% w/w were obtained respectively. Model validation gave an Rval2 and RMSEP of 0.9 and 2.7% w/w respectively, demonstrating the ability of NIR spectroscopy to predict granules water content. The scanning electron microscopy (SEM) pictures validated the process feasibility.

Internal mixing air-assisted spray nozzle for large droplets: Experimental measurements and numerical simulations

In the present study, detailed experimental measurements of a large-droplet spray nozzle under a wide range of operating conditions have been conducted at China Aerodynamics Research and Development Center (CARDC) low-speed vertical wind tunnel facility. The droplet size distributions obtained from these measurements have been modeled using the Rosin-Rammler distribution. A multi-physics multi-phase numerical model for the simulation of the complex spray dynamics associated with the large-droplet spray nozzle has been developed in order to support the performance characterization of this device. More specifically, the primary breakup of liquid (water) in the atomizer-produced spray is modeled using a volume of fluid (VOF) to discrete phase model (DPM) transition representation. The numerical model is validated using the experimental measurements. The small relative error between the numerical predictions and experimental measurements for the droplet size distribution and for a number of characteristic droplet diameters suggest that the numerical model provides accurate high-fidelity predictions of the spray dynamics of the large-droplet spray nozzle. Moreover, it is shown that a simple modification of the spray nozzle (increasing the length of the mixing chamber by 50%) has a significant effect on the performance of the nozzle. In particular, the droplet median volumetric diameter and the spray angle are increased as the air pressure is decreased. Furthermore, an increase in the nozzle mixing chamber length results in a much broader droplet size distribution. The validated VOF-to-DPM transition model developed in this study can be used for a future redesign (involving modifications of some key geometric parameters) of the original large-droplet spray nozzle to generate reliably and robustly larger droplets required to simulate various supercooled large droplet conditions of practical relevance.

CFD simulation and performance evaluation of gas mixing during high solids anaerobic digestion of food waste

To analyze the flow characteristics of the gas-mixed high solids anaerobic digestion (HS-AD) system and optimize the mixing performance, the mixing performance of gas and non-Newtonian fluid in the HS-AD system was investigated using the CFD simulation. The mixing energy magnitude, input pattern and nozzle inlet angle were optimized by evaluating available mixing indices. The performed experiments showed that the non-Newtonian fluid properties and consistency index of the food waste increased as the total solid increased. Moreover, it was found that the higher the reactor diameter, the greater the input energy, the smaller the dead zone, and the higher the global velocity gradient. Under specific input energy conditions, more mixing was achieved with the gas dispersed inlet compared with the centralized inlet. Symmetrical nozzles were arranged in the digester with a spacing of 180°, and mixing was the most effective when each nozzle formed an angle of 45° with the horizontal tangent of the reactor wall. As for the available mixing indices, both local velocity gradient and UI were the key ones and more meaningful to reflect mixing homogeneity of the system. The obtained results demonstrate that CFD is a powerful tool to optimize the mixing performance in high solids anaerobic digestion systems.

Injection Molding of Soft Robots

AbstractTo date, injection molding has not been a practical manufacturing method for soft robots due to machine costs, large volumes of liquid silicones required, and the inability to change materials quickly between shots. Injection molds are typically machined from metals to allow for high pressure and clamping forces, which further limits the ability to rapidly prototype soft robots when molds could cost thousands of dollars. To circumvent these issues, a low‐cost injection molding system and process are pioneered. In this article, the apparatus, design process, economics, and workflow are described using standard stereolithography and polyjet 3D printers to rapidly iterate on soft robot designs. The mold design process is further detailed to allow for proper material flow, clamping, alignment, and rapid curing times. Static mixing nozzle efficacy is characterized with common silicone materials compared to manual mixing and centrifugal planetary mixing. Lastly, a number of applications that could only be achieved through injection molding due to geometry, embedded components, or cure times are presented.

On-grid and in-flow mixing for time-resolved cryo-EM.

Time-resolved cryo-electron microscopy (TrEM) allows the study of proteins under non-equilibrium conditions on the millisecond timescale, permitting the analysis of large-scale conformational changes or assembly and disassembly processes. However, the technique is developing and there have been few comparisons with other biochemical kinetic studies. Using current methods, the shortest time delay is on the millisecond timescale (∼5-10 ms), given by the delay between sample application and vitrification, and generating longer time points requires additional approaches such as using a longer delay line between the mixing element and nozzle, or an incubation step on the grid. To compare approaches, the reaction of ATP with the skeletal actomyosin S1 complex was followed on grids prepared with a 7-700 ms delay between mixing and vitrification. Classification of the cryo-EM data allows kinetic information to be derived which agrees with previous biochemical measurements, showing fast dissociation, low occupancy during steady-state hydrolysis and rebinding once ATP has been hydrolysed. However, this rebinding effect is much less pronounced when on-grid mixing is used and may be influenced by interactions with the air-water interface. Moreover, in-flow mixing results in a broader distribution of reaction times due to the range of velocities in a laminar flow profile (temporal spread), especially for longer time delays. This work shows the potential of TrEM, but also highlights challenges and opportunities for further development.

Optimized Design of Internal Mixing Nozzle for Asphalt Oil Based on Fluent

The design of the nozzle has an important influence on the atomization effect of asphalt oil in the road maintenance process. Fluent is used to numerically analyze the atomization process of asphalt oil in an internal mixing nozzle. The physical model of the nozzle was established, and the influence of the gas inlet pressure on the atomization cone angle and the SMD of atomized droplets was discussed. At the same time, the SMD of atomized droplets in different cross-sections downstream of the nozzle was studied. The results show that with the increase of the gas inlet pressure, the atomization cone angle of the asphalt oil gradually increases first and then decreases, and the SMD of the droplets gradually becomes smaller. As the distance between the cross-section and the nozzle outlet becomes larger, the SMD of the droplets on the cross-section first gradually becomes smaller and then remains basically unchanged. According to this rule, it provides a reference for the design of the internal mixing nozzle.

Development of Virus Sterilization Device Applying Filtered Vent Technology

We have developed a demonstration machine of a large-capacity air purification system that purifies a large amount of polluted air using a gas-liquid mixing nozzle and a multi-layer metal fiber filter. A gas-liquid mixing nozzle, driven by the air blower, sucks and accelerates water to form a high-speed two-phase flow. In the centrifugal force field, all the fine particles and aerosols in the bubbles are transferred to the liquid phase water, and the hypochlorite water whose disinfecting effect has been confirmed by the Product Evaluation Technology Infrastructure Organization (NITE). The demo machine can remove fine particles and viruses in the air at 100 m3 per hour with a single nozzle. We have also developed a large-capacity air purification system that can purify 2400 m3 of air per hour with 24 nozzles. In the virus removal evaluation test conducted by The Japan Textile Products Quality and Technology Center (QTEC), the sterilization performance of 99.975% or more was confirmed. We aim to put this technology to practical use at an early stage to purify the air in hospitals, schools, office buildings, etc.

A measuring system for monitoring multi-nozzle spraying tools

Spray tools with multi-nozzle-arrays are used in a wide variety of applications. Monitoring the functionality of complex spraying tools with a large number of individual nozzles is a great challenge. For this purpose, we have developed a measurement technique based on the wetting pattern, which forms on a surface during spray impingement. To investigate the performance of this measurement technique we applied a spraying tool with nine external mixing air-water nozzles, the geometric alignment of which can be freely adjusted. In the first test series, the precision of the evaluation of the nozzle alignment is determined. The second test series focuses on the individual sizes of the wetted areas. Here the reproducibility, the influences of the operating modes and the nozzle type were evaluated. Subsequently, the functionality is tested in an exemplary test case in which two of nine nozzles were readjusted in a defined manner. Finally, the wetting pattern resulting from injecting a full spray is discussed and the necessary image processing steps are provided. In summary, this measuring system allows efficient, fast and cost-effective control and documentation of the alignment and functionality of spraying tools, thereby avoiding production downtime and related costs.

Pressure Elevation of High-Performance Steam-Water Condensing-Injector

The steam-water condensing injector (SI) is a device capable of producing high-pressure subcooled liquid streams by combining steam and subcooled liquid jet at a higher pressure than the inlet streams. The present study investigated the SI's pressure elevation mechanism using supersonic steam and a subcooled water jet. The experiment was carried out using central-water jet type SI equipped with an overflow port at the inlet steam pressures of 0.3 to 0.7 MPa and inlet liquid mass flow rates of 0.4 to 0.7 kg/s. Axial pressure and temperature distributions were measured at the mixing nozzle and diffuser sections to study the pressure elevation mechanism. Based on the analytical foundation laid by Grolmes (1968), the one-dimensional analytical model was implemented by treating SI's two-phase flow regimes as inverted annular and dispersed flows. For the current SI geometry and operating conditions, the present one-dimensional model could predict the axial pressure distribution of the SI and the maximum discharging pressure with reasonable accuracy for sufficiently high inlet flowrate ratio conditions.

Effect of elevated pressure on air-assisted primary atomization of coaxial liquid jets: Basic research for entrained flow gasification

Highly resolved numerical simulations have been conducted for a generic, coaxial air-blast atomizer designed for fundamental research of entrained flow gasification processes. Objective of the work is to gain a detailed knowledge of the influence of elevated reactor pressure on the primary atomization behaviour of high-viscous liquid jets. In agreement with measured breakup morphology and breakup regimes proposed in literature, the simulations yield a pulsating mode instability of liquid jet, along with disintegrations of fibre-type liquid fragments for different pressures. From the mechanism point of view, the breakup process has been shown to be triggered by concentric, axisymmetric ring vortices, which disturb the liquid jet surface in a first stage and penetrate further into the intact core, leading to interfacial instabilities and pinch-off of liquid ligaments. The liquid jet breaks up faster at elevated pressure, leading to a shorter core length LC. The calculated exponent (b≈−0.5) of the power law for fitting the decrease of LC with p agrees well with measured correlations from literature in terms of varied momentum flux ratio M and Weber number WeG, although water jets, atmospheric pressure and different air-assisted, external mixing nozzles were used in these works. Therefore, the effect of elevated pressure is equivalent to that of increased M or WeG, which scale linearly with p or the gas density for the current setup. The specific kinetic energy of liquid kL has been found to be increased with p, which is particularly pronounced in the high frequency range. A first-order estimate has been proposed, which can be used for the evaluation of liquid kinetic energy or droplet velocity within the spray. The results have been validated by simulations with twice-refined resolution, yielding a grid-independence behaviour with respect to the primary breakup characteristics. However, the follow-up processes with secondary breakup and spray dispersion are reproduced better by using the finer grid.

A simple method to set the spray properties for flame spray pyrolysis production of nanoparticles

The most critical part of the flame spray pyrolysis (FSP) process is the nozzle, since it plays a key role in setting the spray properties. In this study, we developed an approach to adjust the nozzle throat gap size for a desired dispersion gas flow rate and upstream pressure, based on the external size and shape of a two phase external mixing nozzle. An equation was derived and validated by comparing the predicted gas flow rates with the data provided in a commercial nozzle supplier chart. Experiments were also conducted in our lab-scale FSP reactor to test the validity of the predictions. The approach developed here was found to closely predict the gap size necessary to pass the required dispersion gas flow at a desired pressure drop. Error in predictions was found to be less than 3% at an upstream pressure range of 3–10 bars. The isentropic flow assumption for perfect gases across the convergent-divergent nozzle was found to fail below 2 bars, consistent with the theory applied. By using the method here, the nozzle setting for a desired operation in an FSP process can be easily done, minimizing the time-consuming trial and error steps needed otherwise.

Experimental and Numerical Simulation of Flow Pattern Evolution in a Flow Mixing Nozzle under a Moderate Inlet Flow Rate.

A flow mixing nozzle is a novel two-phase flow nozzle with a simple structure and has broad application prospects in the industrial field. However, the research on the working characteristics of this nozzle is mainly focused on a low inlet flow rate. There are few research studies on the working characteristics of the moderate and high flow rates which are more concerned in the industrial field, which limits the application of the flow mixing nozzle. In this paper, the experimental and simulation studies on the internal two-phase flow pattern and spray form of the flow mixing nozzle under a moderate inlet flow rate are carried out. The results show that the change in the two-phase inlet flow rate and the tube hole distance of the nozzle will affect the gas and liquid inertia force, thus affecting the working characteristics of the nozzle. The enhancement of gas inertia force will cause the flow pattern inside the nozzle to change to an unstable radially concave cone, and the spray form will be converted to atomization; the atomization effect of the liquid is better. The enhancement of the liquid inertial force will cause the flow pattern inside the nozzle to change to a radially convex cone, and the spray form will be converted to breakup; the atomization effect of the liquid is poor. The liquid surface tension maintains the existence of the cone inside the nozzle and plays a dominant role in jet atomization when the gas and liquid inertial forces are weak. In addition, the study also found that because of the compressibility of gas, the orifice has a reinforcing effect on gas inertia force.

Experimental studies and multi-factor analysis of the fuel component distributions over the mixing head nozzles of the liquid rocket engine

A model device of the liquid rocket engine mixing head for experimental determination of hydraulic non-uniformity of fuel distribution is described. Schemes of hydraulic and gas-dynamic test benches are given. The results of the planned factor experiment to determine the array of flow rates through individual sprayers are presented. Neural network regression factor models were created to evaluate the criterion of non-uniformity. The influence of various factors on the parameters of non-uniformity is estimated

The impact on the mechanical properties of multi-material polymers fabricated with a single mixing nozzle and multi-nozzle systems via fused deposition modeling

Multi-material 3D printing and process parameters optimization using multiple extruders are the significant challenges of fused deposition modeling (FDM). This paper focuses on the filament extrusion method and presents a comparison of two modes: multi-material single mixing nozzle and multi-material multiple nozzles, thereby linking technology with the mechanical properties. Tensile testing specimens were printed in two different scenarios to validate the comparison: (1) multi-material multi-layered section printed using a multi in-out single mixing nozzle and (2) multi-material multi-layered section printed using a multiple extrusion nozzle within the same carriage. Both modes followed a rectilinear infill pattern and different material combinations. The material combinations implemented included ABS-HIPS, ABS-PLA, PLA- HIPS, and PLA-HIPS-ABS. A behavioral study was evaluated on the mechanical properties of these materials. The results provide a tool for selection on which type of mode is considered suitable for maximizing efficiency and performance to fabricate a multi-material 3D printed product.

Theoretical Uniformity Analysis and Improvement of Spray Deposition by Mixing Nozzles with Heating Conditions

Spray coating is widely used in the manufacture of deposited layers of electronic devices due to its unique advantages of high-speed deposition over a large area. To improve the spray deposition process for further low-cost and uniform production, the uniformity of the spray deposition should be systematically investigated. The current study, however, mainly focuses on the experimental trials with few numerical directions especially for the mixing nozzle sprayers with heating conditions. In the paper, we conduct a theoretical study on the uniformity of the internal and external mixing nozzles. The influencing factors include the initial angle, the total ink flow rate, the transporting gas velocity and the distance from the nozzle to the substrate. Then, the orthogonal test method is adopted to obtain the optimal combination of the parameters. Finally, the effects of different heating modes on the uniformity have been further studied. The results show that these factors influence the uniformity with the two types of nozzles to a different degree. The evaporation of the atomized droplets can effectively improve the uniformity in a certain temperature range. The heating temperature with the highest uniformity is various depending on the heating modes, which should be carefully addressed during the actual production.

The Effects of Heating Conditions on the Spray Uniformity of the Mixing Nozzle

Organic electronic devices such as organic thin-film transistors and organic light-emitting diodes have similar structures, which are composed of various layers with different functions. The thickness and uniformity of the deposited layer quite affect the performance of devices. Therefore, it is important to produce a deposited layer with high uniformity. Spray coating is the method which has a unique advantage for high-speed deposition over large areas, and the temperature has a greater influence on the uniformity. In order to study the effect of heating temperature on the uniformity, two types of nozzles including internal mixing and external mixing nozzles were studied. The position of the heating surface is set at the top, surrounding and bottom of the fluid zone. The results show that the spray uniformity can be effectively improved when it is heated, while the temperature with the highest uniformity is different.