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Calculating the composition of the combustion products serves as the starting point for the high-area ratio (HAR) rocket nozzle. The HAR rocket nozzle finds application in next-generation hypersonic vehicles and missiles. The gas dynamics, gas radiation, and turbulence-chemistry interactions (TCI) play a crucial role in simulations of hypersonic turbulent reactive flows through a rocket nozzle. The interaction of turbulence and chemistry leads to random species mixing and enhanced heat transfer. The k-omega shear stress transport (SST) model is employed to calculate the average flow fields. The eddy dissipation concept (EDC) with reduced chemistry is applied to capture the TCI in the nozzle. The spectral properties of H 2 O are calculated using the full spectrum k -distribution (FSK) model in conjunction with the first-order spherical harmonics method. The mass fractions of combustion products obtained from Particle Swarm Optimization (PSO) and Monte Carlo (MC) methods agree well with the Chemical Equilibrium with Applications (CEA) code. The flow fields obtained with the current solver are validated with the published experimental data. A significant rise and fall of 7–8% have been observed in the centerline flow properties when not including the TCI models in the flow solver. The centerline flow fields obtained with different discretization schemes are in good agreement. The radiative heat flux from the H 2 O species is more dominant than the convective. • Calculate the chemical equilibrium composition of product species for the H 2 –O 2 combustion using the Monte Carlo and PSO methods. • Modeling of the hypersonic turbulent reacting flow of a high-area-ratio (HAR) rocket nozzle in OpenFOAM. • Developed and implemented a spectral model to calculate the radiative properties of H 2 O gas in OpenFOAM. • Effects of turbulence-chemistry interactions (TCI) on the flow fields are analyzed. • Radiative and convective heat transfers are more significant near the throat area. [ABSTRACT FROM AUTHOR]

Currently, the primary method for controlling red tides in the ocean involves spraying water solutions with special chemicals as solutes. High-pressure spraying results in the formation of typical jet structures. In this study, numerical simulation methods are employed to investigate the velocity variations, turbulent characteristics, and gas content distribution of jet flow fields under different initial jet flow pressures, cone angles, and nozzle diameters. Based on practical application scenarios, cluster analysis is used to explore the similarities and differences in jet equivalent diameters under different parameter conditions. The research findings indicate the following. (1) The difference of jet velocity distribution at the far field exit will be enlarged with the increase in the nozzle cone angle. When the nozzle cone angle is 4 mm, the velocity uniformity at the outlet is the best. (2) The TKE of the flow field has no consistent change law along the central axis. At the jet exit, the TKE shows an obvious multi-peak structure. (3) The gas content demonstrates a typical "double-valley" feature at the jet outlet cross-section. Increasing the initial pressure leads to a decrease in the gas content within the jet due to reduced entrainment, while the entrainment range remains largely constant. (4) Cluster analysis reveals that the similarity of jet flow width when it reaches the water surface is minimal compared to other operating conditions when the initial pressure is 0.36 MPa, the cone angle is 115°, and the nozzle diameter is 2 mm. All conditions can be categorized into two or three groups to ensure jet effectiveness. The study results provide scientific guidance for selecting spray devices for controlling red tides in the ocean. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper deals with CFD analyses of the difference in the nature of the shock waves in supersonic flow under atmospheric pressure and pressure conditions at the boundary of continuum mechanics for electron microscopy. The first part describes the verification of the CFD analyses in combination with the experimental chamber results and the initial analyses using optical methods at low pressures on the boundary of continuum mechanics that were performed. The second part describes the analyses on an underexpanded nozzle performed to analyze the characteristics of normal shock waves in a pressure range from atmospheric pressure to pressures at the boundary of continuum mechanics. The results obtained by CFD modeling are prepared as a basis for the design of the planned experimental sensing of density gradients using optical methods, and for validation, the expected pressure and temperature courses from selected locations suitable for the placement of temperature and pressure sensors are prepared from the CFD analyses. [ABSTRACT FROM AUTHOR]

Consideration has been given to the specific features of the work process of a hydro-steam turbine operating on the principle of Segner′s wheel. A method has been suggested for the organization of entry into the turbine channels that ensures minimum hydraulic losses. It has been shown that losses due to the friction of the rotor wheel rotating in a steam-water medium have a number of specific features that do not allow their reliable calculation assessment at present. At the same time, some maximum estimates have shown that these losses can be quite significant in the turbine' s total energy balance and force one to pay serious attention to the aerodynamic properties of the periphery zone of the turbine rotor wheel. It has been established that the diversion of the nozzle axes′ direction from the direction of the circumferential velocity of motion of the center of the nozzles' outlet cross section with a view to preventing structure elements from getting into their jets results in a drop of the turbine capacity, which brings about the need for seeking a compromise solution in selecting the angle of this deviation. The calculation assessment of the optimum ratio of the circumferential velocity of motion of the nozzle outlet section to its fictitious velocity corresponding to the available heat drop in a hydro-steam turbine has shown that it lies within 0.32–0.37, depending on the nozzle velocity coefficient, and the flat pattern of the said dependence provides certain freedom to the designer in selecting the turbine design dimensions. [ABSTRACT FROM AUTHOR]

Water energy is one of the potential renewable energy, the problem so far has a low efficiency of the blade Pelton shape. So it takes a series of tools to know characteristics and performance of the Pelton turbine as a hydroelectric power plant in this research. Pelton turbines work by utilizing the potential energy of water stored at a certain head, which flows through a penstock/pipe that is equipped with a nozzle at the end. The high head causes the water to be under high pressure when it reaches the nozzle. The water coming out of the nozzle becomes kinetic energy in the form of a pressurized water jet, which is used to rotate the runner of the Pelton turbine. In this study, the effect of the number of nozzles used to rotate the Pelton turbine was analyzed, with the result that the number of nozzles is directly proportional to the efficiency of the Pelton turbine. Where the highest efficiency value is obtained by using 3 nozzles with a maximum efficiency value of 13.7 %, at 2 nozzles of 12.209 % and at 1 nozzle of 8.82 %. [ABSTRACT FROM AUTHOR]

Considering the demand for the optimization of the technical factors of spraying for a greater area coverage and minimal drift, field tests were carried out to determine the interaction between the area coverage, number of droplets per cm2, droplet diameter, and drift. The studies were conducted with two different types of sprayers (axial and radial fan) in an apple orchard and a vineyard. The technical factors of the spraying interactions were nozzle type (ISO code 015, code 02, and code 03), working speed (6 and 8 km h−1), and spraying norm (250–400 L h−1). The airflow of both sprayers was adjusted to the plantation leaf mass and the working pressure was set for each repetition separately. A method using water-sensitive paper and a digital image analysis was used to collect data on coverage factors. The data from the field research were processed using four machine learning models: quantile random forest (QRF), support vector regression with radial basis function kernel (SVR), Bayesian Regularization for Feed-Forward Neural Networks (BRNN), and Ensemble Machine Learning (ENS). Nozzle type had the highest predictive value for the properties of number of droplets per cm2 (axial = 69.1%; radial = 66.0%), droplet diameter (axial = 30.6%; radial = 38.2%), and area coverage (axial = 24.6%; radial = 34.8%). Spraying norm had the greatest predictive value for area coverage (axial = 43.3%; radial = 26.9%) and drift (axial = 72.4%; radial = 62.3%). Greater coverage of the treated area and a greater number of droplets were achieved with the radial sprayer, as well as less drift. The accuracy of the machine learning model for the prediction of the treated surface showed a satisfactory accuracy for most properties (R2 = 0.694–0.984), except for the estimation of the droplet diameter for an axial sprayer (R2 = 0.437–0.503). [ABSTRACT FROM AUTHOR]

On a mounted laboratory stand, comparative tests were carried out on the effectiveness of spraying wheat plants with liquid using a multi-rotor drone. The study was undertaken with and without propeller rotations. The lack of rotations simulated spraying by a ground sprayer. The height of the drone's displacement above the plants was similar to that of the nozzles above the plants used when spraying with field sprayers, 0.5 m and 1.0 m. The speed of the drone movement was 0.57 and 1.0 m·s−1. The effects of the height and speed of the drone's movement and the impact of the airflow on the volume and uniformity of the liquid application on the plants were assessed. In addition, changes in the transverse distribution of liquid volume in the droplet stream and the transverse distribution of the air velocity in its stream were evaluated. The liquid was sprayed at a constant pressure of 0.2 MPa. The study's results show that the low height of the drone displacement not only had a strong effect on increasing the liquid volume applied to the plants but also improved the uniformity of application at plant levels. It was also noticed that, at a height of 0.5 m, there was a significant irregularity in the air stream under the drone. [ABSTRACT FROM AUTHOR]

Sediment management is a significant part of the decision-making process that hydraulic engineers need to undertake as it has a direct bearing on the environment. Sediment dredging from around intake structures and reservoirs impose a high operating cost. Jets can efficiently remove large quantities of sediment at low operational costs. This study assesses the scouring pattern development by changing nozzle parameters to achieve maximum scouring conditions. Toward this end, scour holes induced by jets generated using the nozzles with four inner angles (30°, 45°, 60°, and 90°) are tested on a cohesionless sediment bed. The experimental results show that the inner nozzle angle, α, and the densimetric Froude number, F0, affect the scour pattern. This work illustrates that the scour hole dimensions grow with increasing α and F0. Based on the velocity measurements, for the range of jet discharges considered herein, the relative velocity Um/U0 is increased by 20%–25% for the nozzle with α = 90° compared to the nozzle with α = 30°. [ABSTRACT FROM AUTHOR]

• Effect of L/D ratios and swirl generator materials was analyzed and discussed. • Thermal separation was enhanced by low thermal diffusivity vortex generator. • Optimum L/D ratio and operating conditions were indicated by isentropic efficiency. • Non-metal swirl generator integrated with a metal vortex tube was recommended. The current research investigates the effects of the swirl generator material, the tube length to diameter (L/D) ratio, and the vortex tube housing material on its performance. Two vortex tube were designed and constructed using either stainless or brass. In addition to testing different materials for the housing, 5 different materials were examined as potential options for the swirl generator, including stainless steel, brass, polyamide, acrylic and wood. All were having nozzle number of 6. The study encompassed three main areas: examining the impact of various L/D ratios on an entirely stainless vortex tube (ESVT) and an entirely brass vortex tube (EBVT), exploring various swirl generator materials at an optimal L/D ratio for the stainless vortex tube and the brass vortex tube, and investigating the influence of an optimal swirl generator material with varying L/D ratios for the stainless and brass vortex tubes. Operating conditions were controlled for all tests, the natural refrigerant, compressed air was used, the inlet pressure was set to 3.0 bar and the cold mass fraction was varied from 0.40 to 0.90. The results revealed that the performance of the ESVT was greater than the EBVT. The best combination was the polyamide swirl generator and brass vortex tube with an L/D ratio of 19.0. This resulted in the maximum isentropic efficiency of 0.27 at a cold mass fraction of about 0.47. [ABSTRACT FROM AUTHOR]

3D bioprinting is a promising technique for creating artificial tissues and organs. One of the main challenges of bioprinting is cell damage, due to high pressures and tensions. During the biofabrication process, extrusion bioprinting usually results in low cell viability, typically ranging from 40% to 80%, although better printing performance with higher cell viability can be achieved by optimising the experimental design and operating conditions, with nozzle geometry being a key factor. This article presents a review of studies that have used computational fluid dynamics (CFD) to optimise nozzle geometry. They show that the optimal ranges for diameter and length are 0.2 mm to 1 mm and 8 mm to 10 mm, respectively. In addition, it is recommended that the nozzle should have an internal angle of 20 to 30 degrees, an internal coating of ethylenediaminetetraacetic acid (EDTA), and a shear stress of less than 10 kPa. In addition, a design of experiments technique to obtain an optimal 3D bioprinting configuration for a bioink is also presented. This experimental design would identify bioprinting conditions that minimise cell damage and improve the viability of the printed cells. [ABSTRACT FROM AUTHOR]

Choosing the right metal AM equipment and material is a highly intricate process that forms a crucial part of every manufacturing company's strategic plan. This study undertakes a comprehensive comparison of the performance and material properties of three Metal Additive Manufacturing (AM) technologies: Powder Bed Fusion (PBF), Metal Filament Deposition Modeling (MFDM), and Bound Metal Deposition (BMD). An automotive nozzle was selected and manufactured using all three technologies and three metallic materials to understand their respective advantages and disadvantages. The samples were then subjected to a series of tests and evaluations, including dimensional accuracy, mechanical properties, microstructure, defects, manufacturability, and cost efficiency. The nozzle combinations were PBF in aluminum, MFDM in stainless steel, and BMD in hard tool steel. The results underscore significant differences in functionality, material characteristics, product quality, lead time, and cost efficiency, all of which are crucial factors in making equipment investment decisions. The conclusions drawn in this paper aim to assist automotive industry equipment experts in making informed decisions about the technology and materials to use for parts with characteristics like these. Future studies will delve into other technologies, automotive components, and materials to further enhance our understanding of the application of metal AM in manufacturing. [ABSTRACT FROM AUTHOR]

The trend toward the scalability of fused filament fabrication requires strategies to reduce printing time. One way consists in using calibrated nozzles with larger diameters. However, the reduction in manufacturing time is accompanied by reduced printing resolution and changes in the control of the material's viscous behavior. In this work, the parametric calibration was performed on a 1 mm diameter nozzle printing cubic models in polylactic acid. The procedure was divided into three steps: (i) identification of printing defects; (ii) systematic parametric study (based on Taguchi method); and (iii) interactive parametric refinement. The calibration of the 1 mm nozzle involved the analysis of six fused filament fabrication variables: layer thickness, extrusion temperature, extrusion multiplier, infill speed, perimeters speed, and first layer speed. Their effects were analyzed considering esthetic quality, dimensional and shape conformity, mass, and compression modulus variation of the parts. Despite the high degree of customization of fused filament fabrication printers, the results show that switching to a larger nozzle is not "plug-and-play". The user needs to know the correlations between the printability of the material and the effects of the variables involved in slicing, especially extrusion multiplier and layer thickness. Both variables act directly on the main problem of printing with a 1 mm nozzle, controlling the extrusion volume with the best accommodation of the material between and within layers. The main contribution of the study highlights that large diameter nozzles can induce poorly distributed accumulations of excess material, which decreases the quality of surfaces, deforms parts, destabilizes dimensions, and disorganizes the mesostructure (reducing rigidity) of the models. Finally, the parameter refinement process defined a base configuration for future studies to improve 3D printing with 1 mm nozzles. [ABSTRACT FROM AUTHOR]

Wax deposition is one of the most common complications in oil production. The most promising method of preventing wax depositing is dosing of wax inhibitors. Based on the results of studies at the Cold Finger installation, it was found that dosing an inhibitor at a temperature below wax appearance temperature reduces the efficiency of the inhibitors. Based on large scale, numerical simulation was found that dosing by "drop" injection through the impulse tube leads to the accumulation of the inhibitor in the near-wall zone and low distribution over the cross section of the tubing. When dosing with a nozzle, the degree of distribution of the inhibitor increases and reaches the highest value at a nozzle diameter of 0.5 mm and a length 1.5 cm. The influence of flow rate on the degree of inhibitor distribution was also evaluated. It was found that with an increase in the flow rate to 45 m3/day, the distribution of inhibitor improves and reaches the highest value, after which it does not change. The results of the work performed will make it possible to scientifically substantiate the choice of the inhibitor dosing site in order to achieve the greatest efficiency and reduce the cost of servicing oil wells. [ABSTRACT FROM AUTHOR]

Uniform air distribution is the basic condition for the stable operation of circulating fluidized beds and closely related to the hole layout of nozzles and the air outlet conditions. In this paper, CAD modeling software is used to establish different opening types for nozzles and the corresponding gasifier models, and Fluent simulation software for numerical simulations (k-ε model) is introduced to the hydrodynamic behavior of the upper opening, the side opening and the combined opening types of nozzles, as well as the corresponding single-nozzle fluidized bed gasifiers. The flow field distribution under the above opening modes is obtained, including the velocity distribution, static pressure distribution, and total pressure distribution, and the influence of the boundary conditions, including the inlet gas velocity and outlet pressure, on the flow field distribution inside the nozzle and in the single-nozzle fluidized bed gasifier is also investigated. The simulation results show that the suitable optimal operating conditions for the coal gasifier can be achieved with an inlet velocity of 30 m/s and an outlet pressure of 25 kPaG. Under the above conditions, the local fluidization dead zone at the elbow and top of the nozzle is narrower, the uniformity of the wind velocity can be improved, the pressure drop of the inner core tube of the nozzle is gentle, and the pressure distribution tends to be stable. Theoretically, the anti-slag performance of the nozzle is improved, which will enhance the stability and reliability of the operation of the gasification unit. [ABSTRACT FROM AUTHOR]

Purpose: to develop software for the process of arranging sprinklers on the water-conducting belt of a sprinkler to improve the irrigation quality. Materials and methods. As a theoretical basis for creating software, the traditional methods of algorithmization and programming based on the processes of algorithm design for solving the problem of calculating the optimal spacing and flow-pressure characteristics of deflector nozzles on the water-conducting belt of sprinklers, respectively, formalized in the form of a scheme, and writing the source code in the object-oriented programming language Python were used. Results. To replenish the domestic scientific and technical base for digitalization of engineering and reclamation work with information tools, software for the process of arranging sprinklers on water-conducting belt of a sprinkler for uniform distribution of artificial rain along the irrigated area has been developed. The algorithm graphical model is represented by three blocks. The “Source data input” block provides a choice of the type of sprinkler, the operating flow rate of irrigation water, as well as the material of the water conducting belt. In the “Intermediate and target values calculation” block, the irrigation water loss, head loss, distance between the end and first nozzles, as well as the total number of sprinklers are calculated. In the “Cyclic computation and output of results” block, head losses along the length and local pressure losses are determined for each section, the sum of which makes up the total head losses. Using the designed software, computations were performed using the example of a cantilever sprinkler with 4 sections of steel pipeline, a total flow rate of 6 l/s and a pressure at the end of the console of 10 m. It was determined that to ensure the uniform distribution of artificial irrigation along the irrigated area, it is necessary to install 9 sprinklers with variable spacing along the length console, and to provide a head at the beginning of the sprinkler machine of 23.8 m, taking into account the total head loss of 13.8 m. Conclusions: the software allows simulating the optimal arrangement of deflector nozzles of the same size on a water-conducting belt at the design stage of double-cantilever and multi-tower lateral sprinklers.

The use of a vent on a gas stove affects the mixing of air with fuel. This study examines the effect of different vent diameters on the performance of Dimethyl Ether (DME) gas-fueled stoves. A nozzle with variations in vent diameter of 3 mm, 2 mm, 1 mm, and no vent with a nozzle diameter of 0.96 mm at each vent. Installed on the fuel ignition system, the flame, heat intake, and combustion efficiency were tested. From the test results at a pressure of 280 mmH2O, the highest flame noise value after shutdown was obtained at the nozzle with a 1 mm vent which amounted to 64.2 dB, the highest heat intake value at the nozzle with a 1 mm vent which amounted to 1.6625 kW, and the highest efficiency value at the nozzle with a 3 mm vent which amounted to 59.135%.

In this paper, various configurations of jet nozzles are analyzed, as well as their design. The effects of the inlet chamfer of jet nozzles on their flow rate and range are considered. It is shown out that today it is expedient to make precision micro-holes of the nozzles using high-precision three-dimensional electric-erosion equipment. The optimal design parameters of jet nozzles are also determined.

The paper highlights that in industrial plantings, pests and weeds control is conducted using sprayers. To establish the required liquid fl ow rate, it is necessary to use calculations for sprayer adjustment. A small-sized, remotely controlled «GNOM» unit, developed at Gorsk Agrarian University, is designed for various tasks, including herbicidal spraying in fruit nurseries. (Research purpose) The research aims to substantiate the optimal parameters of the spraying unit in the herbicide treatment module. It also seeks to investigate the dependence of the flow rate of the working fluid and quality of liquid spray on the pressure in the system. (Materials and methods) A laboratory installation was developed to study the spray characteristics. Nylon threads with diameters of 100 and 250 micrometers were placed within the spray zone, and the resulting liquid spray was captured using a Nikon COOLPIX 58100 digital camera. Each subsequent experiment was carried out at a liquid pressure of 0.05 megapascals more than the previous one. (Results and discussion) The experiments resulted in obtaining images of the spray swath for a small-sized self-propelled unit, allowing for the categorization of the spray based on droplet sizes. The theoretical analysis demonstrated how changes in the air volume within the tank influence both the pressure and quality of the liquid spray. Additionally, it showed how the dispersion depends on the pressure of the working fluid. (Conclusions) The analysis of the working fluid spray showed that at a pressure in the hydraulic system in the range from 0.65 to 0.75 megapascals and a spray angle of 90 degrees, the highest quality fine spray is observed, the flow rate of the working fluid is in the range of 0.4-0.6 liters per minute, which very signifi cantly affects the size of the treated area in the direction of its increase at one tank refueling unit.

Encapsulation is a very relevant process today, as it allows you to protect the encapsulated material (probiotic) from environmental influences: moisture, heat, etc., thereby increasing the chances of squeezability. To select the optimal percentage of sodium alginate 0.5%, 0.8%, 1%. The experiments were carried out at temperatures of the gel-forming mixture from 20 to 50 ℃. A nozzle with an outlet hole d= 1,2×10-3м was selected as the most optimal both in terms of performance and quality of the capsules obtained. When determining the viscosity in the Brookfield viscometer, the constant mode goes out after the rotor speed from 0,333 с-1 до 0,833 с-1. A suspension of a strain of propionic acid bacteria Propionibacterium freudenreichii was added to the resulting mixture. Eventually, rounded capsules containing the probiotic Propionibacterium freudenreichii were obtained, which can be used in further technological processes in the production of food products of therapeutic and preventive action or in the production of pharmacological preparations. The gellike raw material, when pressurized with a gear pump, experiences instantaneous elastic deformation and further, at a stress exceeding the yield strength, viscoplastic deformation. Under the influence of pressure and the deformations tested, the gellike raw material enters the nozzle, is sprayed, and then forms microcapsules. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Textiles & Engineers / Tekstil ve Mühendis is the property of Union of Chambers of Turkish Engineers & Architects, Chamber of Textile Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the manufacturing sector, there is a constant effort to improve procedures to produce high-quality goods at a lower cost. Academics are improving aspects of the metal machining process to increase efficiency. New techniques have been developed to achieve this, utilizing better production procedures and more advanced technological tools. It is essential to optimize production processes and minimize their negative impact on the environment and human health. Therefore, environmentally friendly machining operations, such as minimal quantity lubrication (MQL) machining, are being implemented. MQL is used in metal removal processes like milling, drilling, and turning to reduce the use of cutting fluids. The effectiveness of MQL can be improved by misting the flank face and the area near the chip tool contact. A turning center suitable for MQL configuration has been developed as part of the current research project. During the turning of Inconel 718 under dry, conventional fluid, and conventional fluid under MQL process conditions, forces and surface roughness data were examined. [ABSTRACT FROM AUTHOR]

Creating a high-quality aircraft engine is closely connected to the problem of obtaining the jet flow characteristics that appear while an aircraft's engine is in operation. As natural experiments are costly, studying turbulent jets by numerical simulation appears practical and acute. Biconic nozzle supersonic jet flow is the research subject of this article. A compression and expansion train of waves called barrels were formed in the jet flow at preset conditions. The simulation was performed on an unstructured numerical grid. In order to enhance the calculation accuracy in the shock-wave domain, a hybrid gradient computation scheme and numerical grid static adaptation method were applied in the regions of gas-dynamic values' significant differential. This approach resulted in a description of nozzle supersonic gas flow structure. It was shown that building local refinement when using a static adaptation numerical grid contributed to improving the accuracy of determining shock waves' fronts. In addition, this approach facilitated the identification of the Mach disk in the flow when using an unstructured grid, allowing for calculation schemes not higher than a second-order of accuracy. [ABSTRACT FROM AUTHOR]

The paper presents a methodology that combines experimental measurements and mathematical-physics analyses to investigate the flow behavior in a nozzle-equipped aperture associated with the solution of its impact on electron beam dispersion in an environmental scanning electron microscope (ESEM). The shape of the nozzle significantly influences the character of the supersonic flow beyond the aperture, especially the shape and type of shock waves, which are highly dense compared to the surrounding gas. These significantly affect the electron scattering, which influences the resulting image. This paper analyzes the effect of aperture and nozzle shaping under specific low-pressure conditions and its impact on the electron dispersion of the primary electron beam. [ABSTRACT FROM AUTHOR]

Accurate modelling of nozzle expansion and associated phase-change processes of CO 2 is critical for optimal design of CO 2 ejectors for refrigeration and air-conditioning systems. The study evaluates the performance of the homogeneous equilibrium model (HEM) in simulating the two-phase flashing nozzle flow of CO 2 for different divergence angles and for subcritical and supercritical inlet conditions. The study also applies the HEM to simulate the transcritical CO 2 flow in a two-phase ejector under various conditions. For nozzle flow at small divergence angles, the prediction of HEM is closer to the experimental data and superior to that of the mixture model. The accuracy of HEM decreases for drastic expansions of CO 2 , and the reason for the inadequate prediction of pressure and temperature in such scenarios is be explained by a critical analysis of the phase transformation process. It is found that the accuracy of the HEM simulations depends on the nozzle geometry. The numerical results for the ejector flow show good agreement with the experimental data. The results for the single and double-choking cases show variations closely related to the shock properties and the mixing process. The study represents the first attempt to investigate the mixing process of the flows in the ejector from the perspective of thermal energy transfer in addition to momentum transfer. [ABSTRACT FROM AUTHOR]

Effective spraying is essential for modern agricultural production, to ensure a high-quality and abundant harvest. Simultaneously, it is crucial to minimise the negative impact of crop protection products on the environment. To achieve this, it is necessary to implement the appropriate technical and technological parameters for the treatment and to consider the conditions under which the treatment is carried out. The aim of this study was to determine the relationship between the speed of the sprayer, the pressure of the liquid, and the type of nozzles, as well as air temperature and wind speed, in terms of the degree of coverage of the sprayed surfaces. The degree of coverage was analysed by spraying water-sensitive papers placed on the artificial plant, positioned to obtain horizontal and vertical surfaces. The study found that standard single flat fan nozzles provided greater coverage on upper horizontal surfaces, while standard nozzles were more effective for vertical transverse approach surfaces at lower fluid pressures and travel speeds. Neural networks were used to develop models of the relationships studied. Models with high accuracy for the validation data set were obtained in the case of the coverage of the vertical transverse leaving surface and the upper level surface (R = 0.93 and R = 0.86). These models were used to determine the optimum values of the technical parameters of the spraying process under the selected weather conditions. The maximum spray coverage (41.49%) was predicted for the XR nozzle under the following conditions: pressure = 200 kPa, driving speed = 1.4 m·s−1, temperature = 21.73 °C and wind speed = 0.32 m·s−1. Based on the sensitivity analysis of the neural models it was found that the greatest effect on the coverage of the vertical transverse leaving surface was observed for temperature and the coverage of the upper level surface was mostly influenced by driving speed. [ABSTRACT FROM AUTHOR]

In reciprocating internal combustion engines, the calculation of the heat transfer coefficient (HTC) is essential to estimate the heat transfer during combustion in the combustion chamber. The HTC calculation takes into account fluid flow and combustion processes and varies as a function of crank angle and location within the chamber. The mean HTC value is commonly used to calculate the thermo-mechanical analysis of various combustion chamber components. In this study, dynamic grids for the intake port, exhaust port and chamber are created in the chamber modelling section of the AVL-Fire software. The intake and combustion processes are then simulated and the calculated pressure data are compared with experimental data at 2800 rpm with 1, 3 and 6 hole injectors. Finally, the distribution of HTC over the chamber walls was evaluated using a time step method. The research also included verification of the HTC results with theoretical data obtained by Woschni and Hohenberg. In addition, with the decreasing availability of fossil fuels and the need for lower exhaust emissions from diesel engines, the use of blends of diesel and hydrogen fuel has become widespread. In this engine, a mixture of 10 % hydrogen and 90 % diesel fuel is used. The final results show that the heat transfer coefficient increases by approximately 1.72 % when hydrogen is added to diesel fuel due to the number of collisions between hydrogen and other fuel components. • Increasing the number of injector holes reduces the pressure in the cylinder. • Adding hydrogen to diesel fuel increases the heat transfer coefficient. • Adding hydrogen to diesel fuel increases engine power and NOx. • Increasing the number of nozzle holes reduces the depth of fuel penetration into the combustion chamber. [ABSTRACT FROM AUTHOR]

A combination of experimental measurement preparations using pressure and temperature sensors in conjunction with the theory of one-dimensional isentropic flow and mathematical physics analyses is presented as a tool for analysis in this paper. Furthermore, the subsequent development of a nozzle for use in environmental electron microscopy between the specimen chamber and the differentially pumped chamber is described. Based on experimental measurements, an analysis of the impact of the nozzle shaping located behind the aperture on the character of the supersonic flow and the resulting dispersion of the electron beam passing through the differential pumped chamber is carried out on the determined pressure ratio using a combination of theory and mathematical physics analyses. The results show that nozzle shapes causing under-expanded gas outflow from the aperture to the nozzle have a worse impact on the dispersion of the primary electron beam. This is due to the flow velocity control. The controlled reduction in the static pressure curve on the primary electron beam path thus causes a significantly higher course of electron dispersion values than variants with shapes causing over-expanded gas outflow. [ABSTRACT FROM AUTHOR]

Taking the large storage tank as the cleaning object, a cleaning robot integrating shoveling, crushing, sweeping and dust-absorbing was developed, and its dust-absorbing system was analyzed and optimized. Firstly, Fluent- EDEM gas-solid coupling was utilized to simulate the dust-absorbing system. By analyzing the fluid distribution and particle trajectory, the internal structure of the dust collection box was optimized to reduce the dust particles entering the fan box. Then, by analyzing the structural parameters of the suction nozzle, the influence of the nozzle shoulder angle, nozzle length, and shoulder height on the dust-absorbing effect was explored, and the parameters were determined, so as to reduce the energy loss and increase the flow rate on both sides of the nozzle. Finally, through the dust suction test, different models of nozzles were tested for dust suction, and the wind speed at the nozzle was measured, and the leakage of dust particles on both sides of the nozzle was significantly reduced after optimization, which verified the reliability of the simulation results and provided a theoretical basis for the design of the sweeping robot. [ABSTRACT FROM AUTHOR]

Slag entrapment from metal–slag interface during continuous casting operations has been a major area of concern for steelmakers globally. The presence of inactive regions in the upper region of the mold poses another challenge. Proper flow behavior of the molten metal coming out of the nozzle in the mold is required to overcome these challenges. Nozzle design greatly affects the flow pattern of the molten steel inside the mold. The present investigation is an attempt to study the flow and solidification behavior in a slab caster mold with the use of a novel‐designed hexa‐furcated nozzle using numerical investigation results. The casting speed and submerged entry nozzle (SEN) depth are varied to study the effect of these parameters on minimizing the inactive zones in the mold and the steel/slag interface fluctuations. The results show that the interface fluctuation increases at higher casting speed and lower SEN depth. The residence time distribution (RTD) analysis was also performed for different cases to investigate the flow behavior. The validation of the fluid flow and RTD curve inside the computational domain is carried out with the use of physical modeling. [ABSTRACT FROM AUTHOR]

The main goal of these scientific studies, which are reflected in this work, is aimed at finding ways to improve quality indicators in the implementation of laser processing of tubular thin-walled blanks. The analysis of literary sources showed that the majority of scientific research is aimed at improving the process of combined gas-laser cutting of relatively thick metal plates. Compared to this, the process of interaction of a focused laser beam and a flow of compressed gas with thin-walled tubular blanks is more complicated. Because it is necessary to take into account the effect of laser radiation on the lower part of the tubular workpiece, as well as the effect of gas pressure, which can distort the geometric configuration of the medical endoprosthesis. After a thorough analysis of a priori information, a strategy of theoretical research was developed, followed by an adequacy check by obtaining experimental samples of medical endoprostheses. Namely, with the help of the Fluent 6.2 software package, the process of the propagation of the auxiliary gas jet at the outlet of the conical nozzle and its interaction with the tubular thin-walled workpiece was simulated. A method of modeling the process of spreading the jet of auxiliary gas at the outlet of the conical nozzle has been developed. Which made it possible to determine the limit values of the auxiliary gas pressure distribution along the axis of the nozzle at which deformation processes and distortion of the geometric configuration of the medical endoprosthesis occur. According to the results of the modeling of the process of the interaction of the auxiliary gas with a cylindrical thin-walled blank, an experimental batch of blanks for medical endoprostheses with a diameter of 1.6 and 4 mm with the simplest ”linear” design of the pattern and different thread lengths and a circle step equal to 0.16 mm was produced. Medical endoprostheses are widely used in medicine for the treatment of such dangerous diseases as thrombophlebitis. [ABSTRACT FROM AUTHOR]

The exploration and development of new hydrocarbon deposits is facing increasing challenges as the global shift to renewable energy sources, such as shallow geothermal deposits, wind farms, and photovoltaics, reduces the dependence on hydrocarbons. To navigate this evolving landscape, it becomes crucial to find solutions that optimize the energy extraction efficiency while maximizing the use of hydrocarbon deposits. This requires exploring opportunities in existing fields and wells, including those slated for decommissioning. This article discusses the potential for extracting resources from seemingly depleted fields, where some 60–70% of the resources remain unrecoverable due to low reservoir energy. Meeting this challenge requires the implementation of secondary and tertiary EOR methods that involve the introduction of external energy to increase reservoir pressure and enhance resource recovery. One of the proposed innovative tertiary methods involves reaming the reservoir using multiple small-diameter radial boreholes generated by a hydraulic drilling nozzle. This strategy is designed to intensify the contact between the production hole and the reservoir layer, resulting in increased or commenced production in certain cases. The described method proves to be a practical application in hydrocarbon deposits, offering the dual benefits of mitigating environmental pollution by eliminating the need for drilling new boreholes and providing a cost-effective means of accessing resources in decommissioned deposits with insufficient reservoir energy for self-exploitation. Another article points out the design variation of a hydraulic drilling nozzle tailored specifically for reaming a reservoir layer. Taking the above into account, this article provides very practical information for future projects in which paths should be sought for the design and development of hydraulic wellheads, among other things, in order to intensify the production from hydrocarbon deposits. [ABSTRACT FROM AUTHOR]

In this work, an experimental analysis of the performance of a cross-flow turbine, commonly referred to as a Michell–Banki turbine (MBT), is carried out for small-scale hydropower production in rural areas located in developing countries to support their social and economic development activities. The study investigates how the efficiency of the MBT is influenced by the presence or absence of a nozzle, along with variations in the internal guide vane (GV) and its angle. The runner had 26 blades that were arranged symmetrically in the periphery between two circular plates. The designed MBT had the ability to generate a maximum of 100 W of power at a water flow rate and a head of 0.009 m3/s and 0.6311 m, respectively. The experimental tests were carried out using a hydraulic bench. The turbine efficiency without the inner GV was found to be higher than that of the turbine with the inner GV; i.e., it was found that the utilization of the GV did not enhance the efficiency of the MBT due to the occurrence of a choking effect. A maximum hydraulic efficiency of 85% was achieved in the turbine without an inner GV in comparison with the efficiency achieved (77%) with this device and an optimum opening angle of the GV of 24° (75% of opening). In this regard, the GV design should be carefully carried out to improve the MBT efficiency. Additionally, the effect of the GV shape on the MBT performance should be experimentally investigated to obtain a more general judgment regarding the role of this device. [ABSTRACT FROM AUTHOR]

The first sample of the resistojet, which together with the arcjet belongs to the class of electrothermal thrusters, was developed in 1929-33 by the Ukrainian designer Valentyn Hlushko. Electrothermal thrusters combine the gas-thermodynamic principle of acceleration in a profiled nozzle with the use of electrical energy to heat the propellant. In resistojets, energy is supplied to the gas by an ohmic heater. In arcjets, the source of energy is the arc discharge. The advantage of this type of thruster is the greater value of the specific impulse compared to chemical rocket engines with solid or liquid propellants. In view of the inverse proportionality of the specific impulse to the square root of the molecular weight, hydrogen was initially chosen as the propellant. However, the operation of electric propulsion thrusters involves long-term propellant storage and excludes the use of hydrogen in liquid form. When stored in a gaseous state, due to the significant rarefaction of hydrogen, the mass of the balloon significantly exceeds the mass of hydrogen itself, negating the gain in propellant mass reduction compared to chemical engines. Interest in the development of electrothermal thrusters was revived by the proposal to use molecular propellants: ammonia and hydrazine. A mathematical model and a method for calculating thermochemical processes in the primary dissociation and secondary synthesis reactions of molecular nitrogen and hydrogen in the nozzle of an electrothermal thruster were developed in this work. The calculation method involves the use of continuity, momentum, and energy equations, considering the change in the molecular composition as the gas expands in the nozzle. The problem of lack of equilibrium constants was solved by generalizing the Saha ionization formula to the case of the interaction between nitrogen and hydrogen atoms. The calculation results demonstrate the possibility of obtaining a specific impulse at the level achieved when working on hydrogen. The necessity of using the non-stationary form of the equations during the creation of the process model in the heater or thruster arc is also indicated.

This research has dealt with the simulation of liquid nitrogen cavitation inside a convergent nozzle. This is important in cryogenic industrial applications. So in this study, computational fluid dynamics methods have been used for simulating the cavitation phenomenon. The Two-phase model in this research has been a hybrid/mixed model. Also, k- ε turbulence model has been employed in realizable state. For meshing the nozzle geometry, Gambit software has been used, while for numerical simulation, Ansys Fluent software has been employed. For simulation of cavitation, Schnerr and Sauer cavitation model has been utilized. This research has also examined the effect of changing the nozzle outlet diameter and the impact of changing the pressure difference in the inlet and outlet of the nozzle on the cavitation. As a novelty and unlike what would have been expected based on the Bernoulli effect, the results obtained from the simulation showed that the increase/decrease in the nozzle's outlet diameter resulted in an enhanced/diminished extent of cavitation in the nozzle's outlet region. Also, the increase/decrease of the pressure difference in the input and output of the nozzle would lead to a higher/lower extent of cavitation. This research also found that the effect of altering the nozzle's outlet diameter on the extent of cavitation has been far higher than the effect of changing pressure difference in its inlet and outlet. The results also indicated that upon reduction of the nozzle's outlet diameter from the base state (1.02 mm) by 10, 20, 30, 40, and 50 %, the volume fraction of the vapor diminished by 22.23, 43.029, 60.66, 74.73, and 87.16 % respectively. Finally, with the increase in the nozzle's outlet diameter from the base state (1.02 mm) by 10, 20, 30, 40, and 50 %, the volume fraction of the vapor increased by 26.83, 55.27, 84.47, 117.12, and 149.31 % respectively.

This article considers how the shape of the inner channel in the anode assembly affects plasma flow velocity in a plasma torch. Three different shapes of the anode assembly were analyzed, all with a conical confusor part of 50 mm in length: with a diameter transition from 12 to 6 mm, from 12 to 8 mm, and from 12 to 10 mm. A computer experiment was performed using the finite element method and then validated by the subsequent full-scale experiment on a laboratory plasma unit. The obtained results were verified. The verification outcomes showed a satisfactory convergence and were consistent with the published data. A review of the existing plasma unit designs for powder production, application of functional coatings, and surface modification was carried out. The software packages implementing the finite element method to solve these problems were examined. The study yielded practical recommendations for consumers and developers of plasma equipment and identified the shapes of the anode assembly enabling both supersonic and subsonic plasma flow regimes.