Exit Part Research Articles

Control of a Circular Jet with a Disk-Type Bluff Body Using a Dielectric Barrier Discharge Plasma Actuator

In this study, a disk-type bluff body was installed at the upper part of a nozzle exit, and the circular jet inside the nozzle was controlled using a dielectric barrier discharge (DBD) plasma actuator (DBD-PA). The effects of the changes in the excitation frequency of the jet induced by the DBD-PA on the jet diffusion were elucidated. The experiments included visualization of the jet cross-section, particle image velocimetry analysis, and velocity measurements using an I-type hot-wire anemometer. When the DBD-PA was driven at a specific burst frequency (900–1400 Hz), a lock-in phenomenon occurred, in which the frequency of vortices generated in the initial jet coincided with the burst frequency. This lock-in phenomenon suppressed the merging of vortices by generating vortices at regular intervals. When vortex merging was suppressed, the jet was less likely to be entrained into the recirculation flow generated by the bluff body, thereby increasing the downstream jet width and average flow rate.

Exploring the atlantic part of the vertebral artery in the South Indian population and its implications in spine surgery.

A descriptive, quantitative cross-sectional study of the atlantic part (V3) of the vertebral artery (VA). This study aimed to bridge the research gap in the morphometry of the V3 segment of the VA in the South Indian population. The microsurgical anatomy of this segment of the VA has been explored in various populations, and a thorough understanding of the anatomy and course of the VA, particularly the V3 segment, is essential to prevent iatrogenic complications. Several computed tomography studies but a few cadaveric studies have explored the V3 segment of the VA in the South Indian population. This study examined 40 VAs from 20 embalmed cadavers that were obtained from the voluntary donation program, and Institutional Ethical Clearance was obtained before the study. The length, diameter, and angle of the vertical, horizontal, and exit parts of the V3 segment of the VA were documented after its exposure. The mean lengths of the right and left VAs on each part were nearly similar, except for the mean length of the horizontal part (right: 38.937 mm, left: 40.237 mm) and total length of the V3 segment (right: 66.870 mm, left: 70.350 mm). These morphometric parameters are essential to spine surgeons who intend to operate on a small part (vertical, horizontal, or exit part) of the V3 segment of the VA. The mean values of the parameters obtained in this study give average measurements or safe limits to surgeons for safe surgical procedures such as the occipital condyle screw technique and C1 laminectomy.

Distribution of river flow in the river bed

The article investigates the fractional and chemical composition of the river flow in the “Sokhsoy” riverbed and their potential applications. The main factors considered are the fractional and chemical composition of fluids flowing along with water in the channel and their changing proportions in water along the length of the channel. The primary components of the fractional composition of suspended solids in the river are particles with diameters of 1.0 - 0.05 mm and 0.05 - 0.001 mm, which account for an average total share of 22.64% and 5.78% in the entrance and exit parts, respectively, for the former, and 3.48% and 5.78% in the entrance and exit parts, respectively, for the latter. The chemical composition of the river discharges is found to be rich in nutrients necessary for plant development, making it a potential source of crop field nutrients. The results suggest that regulating the amount of chemical compounds is possible by controlling the distribution of river flows in the river, as well as the fractional and chemical composition of the flow.

An analysis of longitudinal residual stresses in EN AW-5083 alloy strips as a function of cold-rolling process parameters

Abstract Various process nonhomogeneities in the cold rolling lead to an uneven distribution of deformation across the strip cross-section, resulting in the induction of residual stresses. This study investigates the longitudinal residual stresses in cold-rolled EN AW-5083 aluminum alloy strips using the finite element method (FEM) to achieve reliable predictions. The impacts of process parameters, including the reduction ratio, coefficient of contact friction, and front and back tensions, were analyzed. Changes in residual stresses, depending on the process parameters, were determined by the distribution of linear and shear strains, as well as the strain hardening conditions at the exit part of the deformation zone. An increase in the reduction ratio from 20 to 50%, as well as an increase in the friction coefficient from 0.1 to 0.2, resulted in decreased stress values. The residual stresses on the strip surface, determined by the experimental deflection method, were consistent with the results obtained by FEM simulation. Under the impact of back and/or front tensions, there is a reduction in longitudinal residual stresses, with the front tension exerting the greatest influence. The research results show that the FEM is a reliable tool for predicting residual stresses in cold-rolled strips.

Increasing the accuracy of the process of automated counting of thin long products

Vibrating hopper feeders with an electromagnetic drive for automating the process of counting parts have become widely used. This process is necessary when transferring them to another workshop for the next technological operation. Also, it is necessary to count artificial products on the lot when packing them for packaging. Vibrating feeders are used to feed miniature, small, or medium-sized parts to the counting position of counting or packing machines. In this case, the parts supplied to these positions should be arranged in one layer. In addition, they should have a certain gap between them for reliable operation of the counting device. Basically, counters for such machines are made on the basis of photoelectric or inductive sensors. The disadvantage of inductive sensors is that they can only be used for metal objects. Photoelectric sensors are more versatile, so they have gained the most distribution for counting or filling machines. The principle of operation of the automatic counting position is that when the object to be counted is applied to it, it crosses the working area of the counting position and the sensor sends an impulse to the counting device. When using photoelectric sensors, parts or products cross the beam of the sensor and it supplies a counting pulse to the electronic counter at each crossing of the working beam. Basically, when using vibrating hopper feeders, the counting position is located either directly at the exit part of the transporting tray, or at the exit from it of the transported objects. The speed of transporting parts or products increases when moving up, because the amplitude of the horizontal component of oscillations increases when the diameter of the transporting tray increases. This is because the hopper of the vibratory feeder has a conical shape. This allows the parts to be refined in one layer. In addition, before the counting position, the parts must be separated from each other to create the necessary gap between them. This is necessary for the reliable operation of the photoelectric sensor. This system works reliably when the dimensions of the parts to be counted are larger than the diameter of the working beam of the sensor. But, when automating the counting of thin, long parts or products whose thickness is close to the size of the working beam of the sensor, the latter may cross it several times when passing through the zone of the counting position. This sharply reduces the accuracy of the counting process. This happens because the parts on the conveyor tray move with a small bounce due to the vertical component of the hopper's vibrations. Therefore, it became necessary to develop a new counting position system in order to increase the accuracy of the counting device for counting long thin parts or products (pins for electrical connectors, needles, matches, etc). The work considers a set of elements that affect the productivity and efficiency of counting devices based on vibrating hopper feeders with electromagnetic drives, for counting long thin parts or products of this shape.

Experimental Investigation of the Flow, Noise, and Vibration Effect on the Construction and Design of Low-Speed Wind Tunnel Structure

A wind tunnel is needed for a lot of research and model testing in the field of engineering design. Commercial wind tunnels are large and expensive, making them unsuitable for small-scale aerodynamic model testing. This work aims to experimentally investigate the effects of flow, noise, and vibration on constructing and designing a low-speed wind tunnel structure. The flow uniformity in the wind tunnel has been tested by measuring the velocity profiles inside the empty test section with a pitot-static tube at various fan frequencies. The experiment results showed a good flow uniformity of more than 90% across the test section area, and the maximum wind velocity achieved was about 25.1 m/s. Due to the stability of the flow near the exit test section, the vibration measurement revealed that the entrance portion has larger vibration fluctuations than the exit part. Furthermore, as the axial fan frequency increases, the noise level increases. At 40 Hz, the noise level enters the hazardous zone, which has an impact on the person who performs the measurement process. The resonance of the wind tunnel structure is an important measurement test that affects vibration measurement.

어포던스 이론을 고려한 졸음쉼터 구간별 구성요소의 시설 배치계획에 관한 연구 - 경부 고속도로를 중심으로 -

The main purpose of highways is to allow rapid passage of connections between regions, and although transportation demand has increased as it greatly contributed to high economic growth, it is a difficult problem to be solved in modern society, deepening the problem of population decline due to the death of many drivers. since the cost invested for infrastructure construction is concentrated only on adding facilities at once, the quality of service that users actually feel is low, so it can be said that the environment in which sensory, physical, cognitive and functional aspects are applied is very insufficient. Therefore, this study tried to derive the characteristics of each affordance type and the linkage between the facilities of the rest areas through previous studies and literature review of the rest areas. After dividing the section into three sections, the entry section, the parking section, and the exit section, the status of facilities and expression characteristics of each section were analyzed. As a result of the study, the sensory affordance type was included the highest in the entry part, and the functional affordance was the highest in the parking part and exit part. It was determined that the layout plan should be properly implemented. Finally, this study has significance in suggesting standards that can be applied to future highway rest area plans by studying environmental improvement and improvement plans for rest areas.

Techno-economic evaluation of medium scale power to hydrogen to combined heat and power generation systems

The European Hydrogen Strategy and the new « Fit for 55 » package indicate the urgent need for the alignment of policy with the European Green Deal and European Union (EU) climate law for the decarbonization of the energy system and the use of hydrogen towards 2030 and 2050. The increasing carbon prices in EU Emission Trading System (ETS) as well as the lack of dispatchable thermal power generation as part of the Coal exit are expected to enhance the role of Combined Heat and Power (CHP) in the future energy system. In the present work, the use of renewable hydrogen for the decarbonization of CHP plants is investigated for various fossil fuel substitution ratios and the impact of the overall efficiency, the reduction of direct emissions and the carbon footprint of heat and power generation are reported. The analysis provides insights on efficient and decarbonized cogeneration linking the power with the heat sector via renewable hydrogen production and use. The levelized cost of hydrogen production as well as the levelized cost of electricity in the power to hydrogen to combined heat and power system are analyzed for various natural gas substitution scenarios as well as current and future projections of EU ETS carbon prices.

Design and thermal simulations towards a high intensity radioactive ion source for ISOL@MYRRHA

MYRRHA will be the world’s first large-scale Accelerator Driven System project at power levels scalable to industrial systems. ISOL@MYRRHA will produce Radioactive Ion Beams (RIBs) using the Isotope Separation On-Line (ISOL) technique, with increased isotope production by high intensity primary beams over a long period while maintaining a high-quality RIB. Higher atom flux produced prevalently affects the ISOL ion source. A surface ion source is chosen as a first source because of its reliability and simple design. To understand the hot cavity’s behaviour, finite element thermal-electric simulations were performed. To start, a heating system study with experimental results from the SPES project was reproduced. This concept was then modified by: electrically insulating the source from its support, adding a feedthrough, transforming a passive thermal screen into an active part. With this heating system upgrade, the ion source temperature profile can be adjusted, especially at its exit part where high temperature is expected to play a crucial role in ion production and extraction.

Application of Computational Fluid Dynamics (CFD) Simulation for the Effective Design of Food 3D Printing (A Review)

The progress of food 3D printing (3DP) applications demands a full understanding of the printing behavior of food materials. Computational fluid dynamics (CFD) simulation can help determine the optimum processing conditions for food 3DP such as layer height, deposit thickness, volume flow rate, and nozzle shape and diameter under varied material properties. This paper mainly discusses the application of CFD simulation for three core processes associated with 3DP: (1) flow fields in the nozzle during the extrusion process; (2) die swelling of materials at the die (the exit part of the nozzle); and (3) the residual stress of printed products. The major achievements of CFD simulation in food 3DP with varied food materials are discussed in detail. In addition, the problems and potential solutions that modelers encountered when utilizing CFD in food 3DP were explored.

Enhance the energy and exergy performance of hydrogen combustion by improving the micro-combustor outlet in thermofluidic systems

The main reason for the heat loss of micro-combustors is the hot exhaust gases. In this study, the exit part of the conventional micro-combustor has been improved to increase the heat transfer between the hot combustion gases and the walls of the micro-combustor. For this purpose, several approaches have been applied, including porous media, perforated fins, and 24 and 8 tube outlets for outlet replacement. In these improved micro-combustors, the thermal performances of the combustion of the hydrogen-air are numerically have been investigated. The results reveal that new micro-combustors by enhancing the velocity of the exhaust gases or increasing the surface area of heat transfer or transferring the hot gases to the walls, has led to a decrease in the temperature of the exhaust gases. However, the wall temperature and its uniformity have increased in the improved micro-combustors. Raising the wall temperature and reducing heat loss have increased radiation efficiency, and reducing entropy generation and energy loss in presented geometries diminish the exergy loss and enhance the exergy efficiency. Also, results showed that micro combustor with porous media has the best energy and exergy performance. Finally, the electrical power generation of micro-combustors has been investigated by photovoltaic cells.

Revisiting freeway single tunnel crash characteristics analysis: A six-zone analytic approach

Considerable studies have been conducted to investigate the tunnels’ traffic safety. However, the entrance and exit parts of a tunnel are mostly considered symmetrical in previous studies, and the different lengths (long, medium, and short) of tunnels have not been separately studied. This study aims to investigate the characteristics of traffic crashes in freeway single tunnels by separately considering the entrance and exit of the tunnel as well as the different lengths of tunnels. A six-zone approach is proposed, and the data from 156 single tunnels in Hunan province, China, are applied for safety analysis. The crash rate, crash type, and contributing crash factors are compared between the conventional four-zone approach and the proposed method, and the three types of tunnels with different lengths are also compared for in-depth analysis.Results show that the proposed six-zone method provides a better understanding of the tunnels crash characteristics. The most crash-prone zones for long, medium, and short tunnels are the mid-zone, the entrance zone, and the access zone, respectively. Furthermore, at the tunnel entrance, drivers usually fail to maintain safe distance, which results in the high proportion of rear-end crashes, while at the tunnel exit, they do speeding and improper lane change that increases the risk of sideswipe, rollover, and collision with fixed objects. The study also discusses the crash occurrence mechanism for different types of tunnels. Findings of this study shed some light on the engineering and policy implications for improving traffic safety of the freeway tunnels.

Gunshot injury to the upper limb with an unusual bullet trajectory

Gunshot injuries are not common in European Union countries, although the trend is observed to increase their number over the years [1]. Firearm injuries to the upper extremity are very uncommon. The results of a Swedish study from an urban major trauma center showed only 3 cases of this injury location in a 73 total gunshot wounds treated in one year; the lower extremity was the most commonly involved [1]. If they occur, they are usually the result of accidental shots from hunting rifles, less commonly from police guns or as a result of criminal encounters. As the size of the upper extremity is not great (compared to, e. g. the trunk), the vast majority of these wounds are penetrative by character, with clearly visible entry and exit parts. The spectrum of tissue damage is usually complex, including bone fractures, vessel, nerve, tendon and muscle injuries. Treatment of gunshot wounds may be challenging, particularly if they require reconstruction of several structures [2], [3], [4]. Sometimes complex repairs may be not possible due to tissue defects and the risk of infection. We report the case of a gunshot wound involving the right forearm, arm and shoulder, running along the axis of the upper limb. The entry wound was located in the middle forearm, the trajectory ran along the whole arm and ended at the right clavicle, very close to the axillary artery, where the bullet was found. In spite of such a long distance travelled, the bullet wounded only the brachial artery in the cubital fossa.

Optimization of the process of reproducing units of mass and volume of liquid in a stream, mass and volumetric flow rates of liquid for calibration units with weighing devices

The publication presents an experimental method for estimating the minimum time interval for filling a storage tank with a working fluid with a fixed geometry of the nozzle of the flow switch of the calibration plant when playing units of mass and volume of fluid in the flow, mass and volumetric flow rates of the fluid. Experimental studies were performed in a wide range of mass flow rate 11,10–83,26 kg/s (40–300 t/h) with repeated static weighing of the working fluid. The flow switch is made with a fixed geometry of the flow part of the nozzle exit, which is typical for a large number of calibration units in use in our country with weighing devices. The graphical dependences of the mass flow rate on the time of filling the storage capacity obtained from the research results are the basis for optimizing the process of reproducing units of mass and volume of liquid in the flow, mass and volumetric flow rates of the liquid for calibration plants with weighing devices. These graphical dependencies made it possible to formulate recommendations on the reasonable choice of the minimum interval for filling the storage tank with working fluid in the studied range of mass flow rate. Optimization has been tested and can be extended to calibration units with weighing devices from various manufacturers with individual design and operating parameters.

Dynamics of mandrel holding mechanism of pipe-rolling line automatic mill

The different walled parameter of shells is one of the essential indices, determining quality of hot-rolled seamless pipes, produced at pipe-rolling line (PRL). Thickness variation of shell walls makes a considerable share of the longitudinal and cross-section different walled parameter of finished pipes. The phenomena is stipulated mainly by the rod dynamics with the mandrel in the mill deformation hearth. Based on a study of dynamic model of the mandrel holding mechanism rod, the character of dynamic processes progress at the exit part of PRL automatic mill determined, accounting the shell rolling parameters. A system of differential equations composed for the mandrel holding mechanism rod dynamics, accounting technological parameters and inertia parameters of the rolled shell. The solution of the differential equations system with variable coefficients until the forth approximation realized digitally by application of Runge-Kutt method for correspondent forms of the mandrel rod oscillation. The solution obtained taking the example of calculation of the PRL 350 automatic mill. The picture of dynamic processes of the mandrel holding mechanism rod system at realization of the whole technological process of seamless pipes production at the PRL 350 automatic mill specified. At that, the variable impact of the deformation hearth and change of the rolled shell mass were taken into account. A wide range of mathematic experiment accomplished, that enabled to select necessary technological and dynamic system parameters, determine the stable pipe rolling regimes. Analytical solution of the task obtained, that considerably differs from the earlier known mathematic models. The obtained solution reflects much better the dynamic processes in the mandrel holding mechanism rod system of the PRL 350 automatic mill and specifies the peculiarities of pipe longitudinal different-walled phenomena formation mechanism.

Crash analysis of expressway long tunnels using a seven-zone analytic approach

Research efforts have been made to understand tunnels’ traffic safety. Most of the previous studies have not considered the different features of tunnels with different ranges of length comprehensively. Generally, three- or four-zone approach has been adopted, with which the entrance and exit parts of a tunnel are considered symmetrical in the safety analysis. This study employs a seven-zone analytic approach for the safety investigation of 18 expressway tunnels with length ranging from 2 to 3 km. The results reveal that the crash rate increases firstly for the entrance zone, then decreases for the midzone and again increases at the exit zone. The high crash rates at the access, entrance, and transition zones are attributed to rear-end crashes. Although single-vehicle crashes take place in the mid and exit zones (1) at the tunnel entrance: failure to maintain safe distance; (2) in the midarea: failure to maintain safe distance, fatigue driving, overspeeding, and improper lane change; and (3) at the tunnel exit: overspeeding and improper lane change mainly contribute to the crash occurrence. Friedman test was performed to test the significance of the contributing factors. The crash occurrence mechanism is discussed for the selected long tunnels. Finally, engineering and policy countermeasures are recommended to improve traffic safety in expressway tunnels.

A novel structure design and fabrication method for low liquid consumption and high precision device of colorimeter in water quality detection

Colorimeters based on the Lambert Beer law is now being widely used in water quality detection system. In this paper, we reported a novel colorimeter with low liquid consumption and high precision by optimizing the design of its transition zone and detection area, which would improve the absorbance for specific elements. Combined with stereoscopic fabrication method, six parts including the entrance and exit parts of liquid, the fluid transition path, the detection area, the light intensity enhanced board and the accessories can be assembled on a miniaturized chip. Experimental results show that when the width of the main fluid path for the as-made system is 600 μm, the liquid consumption for every determination is 0.001 mg reducing agent, 0.003 mg chromogenic agent and 0.007 mL standard testing liquid, which was four times lower than traditional structures. The high precision and low liquid consumption have shown our colorimeter possessing the potential of improved absorbance and portable integrated structure for in situ water detection system.

Comparison of fly cutting and transverse planing for micropyramid array machining on nickel phosphorus plating

Nickel phosphorus (Ni-P) is a promising plating material for the moulds used in the precision glass moulding (PGM) of micropyramid structure components. A transverse planing method for machining Ni-P moulds with a micropyramid array pattern is analysed. Notable defects, including chippings and burrs, are observed on the exit and entry parts, respectively. The defect-forming mechanisms are analysed, and it is confirmed that a large cutting thickness and chip interference in non-free cutting tend to be the most effective methods for eliminating defects. Based on the above analysis, the diamond fly-cutting method is introduced into the micropyramid array Ni-P mould fabrication process. The advantage of the diamond fly-cutting method is revealed through comparison with the transverse planing method. To establish a contrast to the transverse planing method and evaluate the machining quality of the structure in the diamond fly cutting, a maximum effective cutting thickness of the remaining surface is proposed based on theoretical analysis. Finally, an experimental setup of ultraprecision fly cutting is established, and an ultraprecision micropyramid array is fabricated on nickel phosphorus plating.

Influence of Xenon and Krypton Flow Rates through the Acceleration Channel of Morozov’s Stationary Plasma Thruster on the Thrust Efficiency

Morozov’s stationary plasma thrusters (SPTs) operating with xenon have been successfully used for many years in space technology. At the same time, due to the high cost of xenon, interest has arisen in alternate working substances. In a number of works, specific features and characteristics of SPTs operating with krypton, which is produced in greater amounts and is one order of magnitude cheaper than xenon, were studied. It was shown that SPTs operating with krypton under typical SPT conditions have traditional characteristics; however, their thrust efficiency is significantly lower than that of thrusters operating with xenon. One of the main reasons for the reduction in the thrust efficiency is the lower conversion efficiency of krypton atoms into ions, which depends on many factors. The most important among them is the krypton flow rate, which determines the plasma density in the acceleration channel. The influence of this parameter on the characteristics of SPTs operating with krypton has not yet received sufficient study, and most works were carried out using one model and in a limited range of krypton flow rates. This paper presents results of a comparative study of the influence of the xenon and krypton flow rates on the characteristics of different-scale SPTs in a wide range of gas flow rates. The results of this study provide information on the specific features of SPTs operating with krypton for different values of the gas flow rate and different geometries of the exit part of the acceleration channel. This information can be helpful for the development of advanced thrusters operating with krypton.

Design and Analysis of Missile Nozzle

In this paper CFD analysis of pressure and temperature for a rocket nozzle with two inlets at Mach 2.1 is analyzed with the help of fluent software. When the fuel and air enter in the combustion chamber according to the x and y plot, it is burning due to high velocity and temperature and then temperature increases rapidly in combustion chamber and convergent part of the nozzle and after that temperature decreases in the exit part of the nozzle. It is concluded in this paper that two inlet rocket nozzle is having better performance than single inlet. We know that the driving forces such as conversation, pressure and temperature gradient can causes species transport, momentum transport and energy transport respectively. Scientist have been worked on “Comparison of the rocket engines efficiency in the case of low thrust orbit-to-orbit transfers” and their findings are the following: The main task of this paper is to compare two types of low thrust rocket engines: constant thrust vs. variable-thrust engines. They are concerned with efficiency, where efficiency is evaluated in the case of the orbit-to-orbit transfer with maximum payload mass in the central Newtonian gravity field.