Outlet Orifice Research Articles

A Mathematical Model for Conical Hopper Mass Efficiency

Almost every branch of industry, at a certain point, utilizes omnifarous materials in their granular form. A key constituent in many bulk material logistic systems is the hopper, which usually acts as a buffering component. In order to achieve the desired throughput, the geometry of the particular hopper must be carefully determined. Considering the geometric properties of the given hopper, the inclination of the walls and the outlet orifice characteristics are the pivotal determinants of hopper functionality. In this paper, the authors have developed an analytical model of the conical hopper’s mass efficiency and compared the model with the experimental results for two distinctive granular materials. The model inputs were: the density of the bulk material, critical angle of material repose, generatrix inclination angle of the cone, and diameter of the circular outlet. The experiment was conducted according to a 32 full factorial design. The repeatability of the results was examined according to Cochran’s theorem and the adequacy of the data was evaluated via Fisher’s criterion, which confirmed the quality of the mathematical model. The error of the developed model does not exceed 4.5%.

Multi-Objective Topology Optimization of Conjugate Heat Transfer Using Level Sets and Anisotropic Mesh Adaptation

This study proposes a new computational framework for the multi-objective topology optimization of conjugate heat transfer systems using a continuous adjoint approach. It relies on a monolithic solver for the coupled steady-state Navier–Stokes and heat equations, which combines finite elements stabilized by the variational multi-scale method, level set representations of the fluid–solid interfaces and immersed modeling of heterogeneous materials (fluid–solid) to ensure that the proper amount of heat is exchanged to the ambient fluid by solid objects in arbitrary geometry. At each optimization iteration, anisotropic mesh adaptation is applied in near-wall regions automatically captured by the level set. This considerably cuts the computational effort associated with calling the finite element solver, in comparison to traditional topology optimization algorithms operating on isotropic grids with a comparable refinement level. Given that we operate within the constraint of a specified number of nodes in the mesh, this allows not only to improve the accuracy of interface representation and motion but also to retain the high fidelity of the numerical solutions at the grid points just adjacent to the interface. Finally, the remeshing and resolution steps both run within a highly parallel environment, which makes it possible for the proposed algorithm to tackle large-scale problems in three dimensions with several tens of millions of state degrees of freedom. The developed solver is validated first by minimizing dissipation in a flow splitter device, for which the method delivers relevant optimal designs over a wide range of volume constraints and flow rate distributions over the multiple outlet orifices but yields better accuracy compared to reference data from literature obtained using uniform meshes (in the sense that the layouts are more smooth, and the solutions are better resolved). The scheme is then applied to a two-dimensional heat transfer problem, using bi-objective cost functionals combining flow resistance and thermal recoverable power. A comprehensive parametric study reveals a complex arrangement of optimal solutions on the Pareto front, with multiple branches of symmetric and asymmetric designs, some of them previously unreported. Finally, the algorithmic developments are substantiated with several three-dimensional numerical examples tackled under fixed weights for heat transfer and flow resistance, for which we show that the optimal layouts computed at low Reynolds number, that are intrinsically relevant to a broad range of microfluidic application, can also serve as smooth solutions to high-Reynolds-number engineering problems of practical interest.

Influence of Nozzle Geometry and Scale-Up on Oil Droplet Breakup in the Atomization Step during Spray Drying of Emulsions

Spray drying of oil-in-water emulsions is a widespread encapsulation technique. The oil droplet size (ODS) significantly impacts encapsulation efficiency and other powder properties. The ODS is commonly set to a specific value during homogenization, assuming that it remains unchanged throughout the process, which is often inaccurate. This study investigated the impact of atomizer geometry and nozzle dimensions on oil droplet breakup during atomization using pressure-swirl atomizers. Subject of the investigation were nozzles that differ in the way the liquid is set in motion, as well as different inlet port and outlet orifice dimensions. The results indicate that nozzle inlet port area may have a significant impact on oil droplet breakup, with x90,3 values of the oil droplet size distribution decreasing from 5.29 to 2.30 µm with a decrease of the inlet area from 2.0 to 0.6 mm. Good scalability of the findings from pilot to industrial-scale was shown using larger nozzles. A simplified theoretical model, aiming to predict the ODS as a function of calculated shear rates, showed reasonable agreement to the experimental data for different atomization pressures with coefficients of determination of up to 0.99. However, it was not able to predict the impact of different nozzle dimensions, most likely due to changes in flow characteristics. These results suggest that the stress history of the oil droplets might have a larger influence than expected. Further studies will need to consider other zones of high stress in addition to the outlet orifice.

Endoscopic intramural cystogastrostomy for treatment of peripancreatic fluid collection: A viewpoint from a surgeon.

Percutaneous or endoscopic drainage is the initial choice for the treatment of peripancreatic fluid collection in symptomatic patients. Endoscopic transgastric fenestration (ETGF) was first reported for the management of pancreatic pseudocysts of 20 patients in 2008. From a surgeon's viewpoint, ETGF is a similar procedure to cystogastrostomy in that they both produce a wide outlet orifice for the drainage of fluid and necrotic debris. ETGF can be performed at least 4 wk after the initial onset of acute pancreatitis and it has a high priority over the surgical approach. However, the surgical approach usually has a better success rate because surgical cystogastrostomy has a wider outlet (> 6 cm vs 2 cm) than ETGF. However, percutaneous or endoscopic drainage, ETGF, and surgical approach offer various treatment options for peripancreatic fluid collection patients based on their conditions.

Numerical Analysis on the Static Performance of Gas Journal Bearing by Using Finite Element Method

In this paper, finite element method is used to calculate the static performance of gas journal bearing, in which rotation speed term is introduced into the stiffness matrix of linear triangular element to realize the performance calculation of the bearing with rotation speed. The results indicate that the average gas film thicknesses corresponding to the maximum load capacity and stiffness, and the minimum attitude angle increase with the growth of orifice diameter. Load capacity and stiffness significantly improved with the increase of rotation speed, eccentricity ratio and supply pressure when the bearing has thin average gas film thickness. Attitude angle increases with the growth of rotation speed, while the growth rate slows down or even decreases at high speed. The most effective way of reducing attitude angle is to increase supply pressure. It can be found that rotation speed affects attitude angle through changing gas pressure difference between two orifices, while other parameters have the same effect by changing gas pressure at orifice outlet.

Flow analysis of a control ball valve in a common rail fuel injector

The electronic control common rail fuel injection system is one of the key technologies being used in modern diesel engines to improve the engine performance. A numerical simulation was conducted to study the characteristics of the fuel flow around the ball valve in the common rail fuel injector. The lift of the control ball valve and static pressure of the flow field around the control ball valve were measured respectively. The simulation was performed with the measurements as boundary conditions such that the flow characteristics can be correlated with the valve lift and the pressure upstream of the ball valve. Simulation results showed that during the valve opening and closing, a high pressure area appeared below the ball valve, while cavitation appeared in the area around the control ball valve. Specifically, the cavitation mainly appeared around the sealing circle, and its upstream area and the conical surface from the entrance to a certain distance downstream. The flow throttling happened at the outlet orifice under the steady-state condition when the valve was at the maximum opening position. The cavitation around the control ball valve was more serious under higher rail pressure conditions. The formation and development of the cavitation was found to be depending on the lift position of the ball valve and pressure of the flow around the ball valve during the valve opening and valve closing. Higher value of void fraction appeared in the flow when the lift of the ball valve was at a larger opening position. It was found that cavitation around the ball valve will affect the consistency and stability of the fuel flow. And cavitation erosion found at the valve seat from a simplified durability test appeared to be close to the place where cavitation appeared from simulation. Therefore, it is suggested that simulation work can be used to examine if cavitation occurs in the flow path of the control ball valve inside the injector in design phase and make necessary changes on the design to prevent the cavitation and the resulting damages to the control ball valve in the injector.

Analysis and design of an inverted oscillating water column for energy storage under choked flow conditions

A novel idealised system based on an inverted, oscillating water column (iOWC) immersed in a mass of water as a potential mechanism for energy storage has been investigated. The system consists of a cylindrical tube separated by a moving disc, dividing the device into two chambers. One chamber contains air and the other water. During the discharge, water enters and contributes to the compression of the air enclosed in the lower chamber. Simultaneously, the compressed air exits the iOWC, ideally at atmospheric choked conditions. The device has been conceived for the energy storage during low-price periods, and for the recovery (e.g. through a low-pressure gas turbine) during peak-pricing hours. The performance the iOWC has been examined for two main design parameters, namely the aspect ratio Λ and of the nondimensional size of the outlet orifice δ. It has been concluded that Λ=16.5 and δ=0.0044 might be a realistic configuration for the practical implementation because (i) the gas is choked at the exit orifice, and (ii) the iOWC’s performance is stable (with relatively small oscillations). Additionally, a thermal study analysing the gas temperature has been conducted. Approximate theoretical solutions for the variables in study have been provided.

Analysis of the structure of the atomized fuel spray with marine diesel engine injector in the early stage of injection

This paper presents the results of the experimental research of the atomized fuel spray with the marine diesel engine injector in the constant volume chamber. The specificity of the phenomena occurring in the marine engine cylinder was the reason to use the optical visualisation method in the studies – the Mie scattering technique. This work presents an analysis of the influence of different geometry of outlet orifice and opening pressures of marine diesel injector on the macrostructure of the fuel spray. In the results, it was observed that the increased L/D ratio of the outlet orifice of the injector caused: an increase in the spray cone angle and a decrease in the spray tip penetration in the early stage of injection. Furthermore, it was defined that the characteristic of spray tip penetration over time was power, whereas the spray cone angle over time was a logarithmic function.

Case Study of Stormwater Control by Permeable Road in Commercial Centre under Equatorial Climate

This paper describes the investigation into stormwater control measures of a 3,425 m2 commercial centre with 61% of the total areas which were tarred surfaces. Targeting these surfaces, permeable roads of various surface areas from 10 to 34% of the total areas were modelled using Storm Water Management Model version 5.0. Testing the permeable roads for very-short duration storms ranging from 5 to 15 minutes, the study found that the catchment area contributing water for detention purposes played a major role in stormwater control. Other than that, the orifice outlet attached to the storage facility was dominant in determining the flow than the storage depth.

The effect of bubble size in descaling process of bubble flow pipes based on leaky ultrasonic guided waves

Crystal scaling in gas-liquid two phase flow pipes is a common issue in many fields, such as chemical engineering, water industries, and energy industries, posing a great threat to the production process and the environment. The characters of air bubbles in the bubble flow have a serious impact on the ultrasonic guided wave descaling inside a pipe. The interaction mechanism between the air bubbles with various sizes and the cavitation bubbles are studied in this paper by combined the finite element method and the bubble dynamics equation, qualitatively analyzing the impact of the air bubble size and the acoustic pressure in the fluid field on the leaky ultrasonic guided waves descaling. The numerical and experiment results show that the maximum expansion radius ratio of cavitation bubble is suppressed from 2.4 to 1.3 when the radius of air bubble grows from 0.5 mm to 4.5 mm. The Ca content removal ratio at 35.5 cm was 81 %, 66 % and 28 %, while the Ca content removal ratio at 60 cm was 76 %, 56 % and 16 % when the gas outlet orifice is 100 μm, 200 μm and 300 μm respectively in the experiment. The results indicate that large bubbles in two phase flow inhibit the cavitation effect of cavitation bubbles and reduce the effectiveness of descaling.

Flow Characteristics of Orifice Plate in Vertical Multistage Flash Evaporator for Waste Heat Recovery

A vertical multistage flash device uses orifice plates as pressure isolation devices, so wastewater flows from the upper stage to the next stage by its gravity, which can significantly lower the system’s surface area. To study the resistance characteristics of the flash flow during wastewater flowing through the pressure isolation device, a flow and flash model for the wastewater in an orifice was developed and the corresponding flash process was numerically investigated by FLUENT. The effects of the inlet temperature of wastewater, flash pressure, and orifice thickness on the flash were analyzed. The results show that the closer to the orifice outlet we are, the lower the temperature of wastewater and the larger the vapor volume fraction become. While the temperature is lower, the vapor volume fraction is larger near the orifice wall than it is towards the center. While the temperature reduction of wastewater is not immediately apparent, the vapor volume fraction in the orifice increases as the pressure differential between the orifice’s input and output increases.

Design of engineering work for the sustainable management of water resource in the department of Tolima

The Autonomous Regional Corporation of Tolima - CORTOLIMA, as the highest environmental authority of the Department, is in charge of the environment and renewable natural resources administration, with water sources being one of the resources monitored and regulated through management processes that guarantee the efficient use of this resource. The water concessions are the mechanism designed to exercise control over the users who take advantage of the water resource in the different uses allowed by law through environmental monitoring that verifies the processes from its capture, conduction, storage, management, and water disposal. Although Tolima has concessioned water users, most do not comply with the construction of the catchment and control works due to their high implementation costs. This document presents a design alternative based on the submerged orifice formula, aimed at small users, which allows them to guarantee only the concessioned flow and minimize the negative impacts on water sources. The design of the control identifies that the outlet orifice diameters in 3/8”, 1/2", 3/4 ", 1”, and 1 1/4”, with heights ranging from 0.01 m up to 0.49 m, are ideal for flows between 0.02 and 1 L/s. This is represented through a calibration curve, the environmental authority's primary input for the review and control of the flow captured.

Numerical simulation optimization of neutral flow dynamics in low-power Hall thruster

This paper utilizes a low-power Hall thruster to investigate its flow field’s neutral flow dynamics. Specifically, under a free molecular flow with a high Knudsen number (Kn>10), we employ the flow conductance theory to investigate the interplay between the internal structural parameters of the thruster flow field and its conductance, which is directly reflected in the neutral gas distribution.Hence, first, we increase the number and diameter of the orifices in the buffer chamber so that the baffle effectively increases the flow field conductance, and thus the number density (nn) of the neutral gas in the discharge channel increases. This phenomenon reduces the ionization mean free path (λi) and thus increases the utilization rate (ηi) of the neutral gas. Then, we alter the baffle orifices distribution to an unequally spaced distribution and stagger the outlet orifices, resulting in a highly homogeneity neutral gas distribution in the circumferential direction, ultimately increasing the effective outlet area and reducing the backflow probability of the neutral gas molecules. This operation reduces the low-frequency oscillation amplitude and thus enhances the thruster’s operation stability. Finally, we explore the influence of the entire operating conditions, especially temperature and mass flow rate variations, on the universality of the simulation results. Overall, this work provides a new concept for optimizing the neutral flow field dynamics of a Hall thruster.

A Numerical Study on the Characteristics of the Pressurized Water Reactor’s (PWR) Primary Moisture Separator Using the Particle Tracking Method

The primary moisture separator—a key component in the PWR nuclear power plant—determines the quality of supplied steam to a turbine. Investigating its characteristics is important because supplying steam with excessive droplet entrainment results in damages to pipes, valves, and turbines in power plant circuits. In this numerical study, the particle tracking method in the Eulerian–Lagrangian methodology is used to investigate the characteristics of a primary moisture separator. Various swirl vanes with different bending angles, vane quantities, and vane locations are chosen to investigate the effect of design parameters on characteristics of the primary moisture separator. Additionally, the water droplet size is considered to vary from 0.01 to 50 μm in this study. The pressure drop between the inlet and outlet, the steam quality at the orifice outlet, and the particle collection ratio are discussed in this paper. The results show that steam quality increases as the bending angle decreases, and increasing the number of swirl vanes increases both the pressure drop and the steam quality.

Investigations of string cavitation and air back suction during injection duration in the scaled-up diesel fuel injection nozzle

The flow inside the diesel fuel injector nozzle is directly associated with the subsequent jet atomization and fuel–air mixture performance, and finally affects the combustion efficiency and emission. In this study, high-speed microscope imaging technology is applied to capture the complex multiphase flow and near-field spray during the process of fuel injection. Besides normal optical experiments for nozzle internal flow and spray, the submerged jet experiment for comparison is also carried out to investigate the phenomenon of air back suction. Combined with the simulation of a three-component multiphase model, the difference between air and cavitation vapor is analyzed. Results show that the submerged jet experiment will not change the internal flow field but can eliminate the influence of air. The shaded area in the hole obtained by the shadow method may be the sucked air or vapor generated by string-type cavitation phase change. Both can coexist in the hole and are closely related to the swirling intensity and the spray structure, respectively. When the needle lift is low, the internal flow field has larger swirling intensity resulting in a kind of hollow spray. The low-pressure region exists in the vortex core, nearly at the axis of the nozzle orifice. The ambient air will be sucked into the orifice to form an air column under the action of pressure difference, which is also easy to occur under low injection pressure. When the needle lift is high, the weak swirl intensity leads to hole-to-hole string cavitation which has weak cavitation intensity and obvious periodicity. At this time, the results of non-submerged and submerged jet experiments are basically the same. In addition, the cavitation bubble near the orifice outlet was observed, for the first time, to move upstream under the action of the pressure difference inside and outside the orifice in the submerged jet experiment. It can be predicted that in the non-submerged jet experiment, the ambient air will be sucked into the orifice to form an air column.

Designing a new bell-type primary air nozzle for large-scale circulating fluidized bed boilers

The design of energy efficient engineering systems is crucial for sustainable operation when economic and environmental consequences are considered. Circulating Fluidized Bed (CFB) boilers, which are among the major contributors to world electricity production, are still increasing in numbers and unit sizes. Primary air nozzles are key components of CFB boilers that may decrease energy consumption and increase energy efficiency, and they need to be carefully designed. There are certain types of nozzles commonly used in the air distribution grate, but even minor design improvements on the nozzle can significantly decrease the pressure loss. This work is about optimizing the bell-type primary air nozzle used in the Turkish lignite-fired ÇAN Thermal Power Plant (CTPP), which has two 160 MWe CFB boilers, through computational fluid dynamics (CFD). Initially, the bell-type nozzle was designed newly by changing the inner head holes geometry. After that, the nozzle geometry was optimized by changing the orifice size and angle to decrease the pressure drop, increase the orifice velocity outlet, and flow uniformity through CFD simulations. With the optimum nozzle geometry, the velocity at the outlet orifices was increased, and a decrease of 2.86 kPa was achieved in the total pressure loss. Furthermore, when the nozzle orifices were designed downwardly with an angle of 105°, pressure drop across the nozzle decreased by 7.6 %, and the uniformity index increased by 2 % at the outlet orifices. Using the bell-type primary air nozzle, which is newly designed, in the CTPP boiler not only will save 2.26 GWh/year of energy consumption but also minimize the backflow risk in the boiler operation.

Surgical Treatment of a Giant Popliteal Venous Aneurysm and Arteriovenous Fistula on the Adjacent Femoral Vein and Its Postoperative Findings.

A case of a giant popliteal venous aneurysm that caused massive pulmonary thromboembolism with an arteriovenous fistula draining into the adjacent proximal femoral vein is reported herein. Deep veins in the lower leg were occluded by thrombi. The inlet and outlet orifice inside the aneurysm was closed and aneurysmorraphy was performed. The fistula was retained on the estimation that it would maintain the blood flow and prevent thrombus formation inside the femoral vein. The aneurysm was shrunk, the femoral vein was patent, and the fistula was not observed 1 year later, although it still existed 1 week after the operation.

Study on the factors influencing air valve protection against water hammer with column separation and rejoinder

Abstract Air valves are used to suppress negative water pressures in water transmission pipelines. They also play a key role during the water filling and drainage stages in pipeline systems. However, systematic guidelines for the selection of air valve parameters are lacking. In practical engineering applications, the selection is mainly based on personal experience. If the selected parameters are not appropriate, negative pressures can occur in a pipeline due to insufficient air inflow or destructive water hammer pressures with column separation and rejoinder, which are caused by rapid air discharge. Given the subjectivity of the selection of air valve parameters in engineering applications, this paper introduces the structure and working principle of two different types of air valves. Combined with engineering examples, the one-dimensional transient flow elastic model and the characteristic method are used to conduct numerical simulations in MATLAB to investigate the influences of the air valve type, the inlet and outlet orifice diameters, and the inflow and outflow discharge coefficients on protection against water hammer with column separation and rejoinder. The inflow and outflow coefficients of the anti-slam air valve have a slight influence on preventing water hammers with column separation and rejoinder. The research results provide a theoretical basis for the rational selection of air valves in practical engineering applications.

Study of the Influencing Factors on the Small-Quantity Fuel Injection of Piezoelectric Injector.

The piezoelectric injection-system provides a reliable approach for precise small-quantity fuel injection due to its fast, dynamic response. Considering the nonlinearity of a piezoelectric actuator, the complete electro-mechanical-hydraulic model of the piezoelectric injector was established and verified experimentally, which showed that it could accurately predict the fuel injection quantity. The small-quantity fuel injection with different driving voltages, pulse widths, and rail pressures was analyzed. The effects of key structural parameters of the injector on the delivery, control-chamber pressure fluctuation, and small-quantity injection characteristics were studied. The results show that the linearity of the curve of the injection volume with the pulse width was relatively poor, and there was a significant inflection point when the piezoelectric injector worked in the small pulse width region (PW < 0.6 ms). The bypass valve significantly accelerated the establishment of the control-chamber pressure, reduced the pressure fluctuation in the chamber, shortened the closing delay and duration of the needle valve, and reduced the rate of the fuel-quantity change so that it provided a greater control margin for the pulse width over the same fuel volume change interval. Under the condition of a small-quantity fuel injection of 20 mm3, decreasing the inlet orifice diameter and increasing the outlet orifice diameter shortened the minimum control pulse width and fuel injection duration required for the injector injection, which is beneficial for multiple and small-quantity fuel injection. However, these behaviors reduce the control margin for the pulse width, especially in small pulse width regions.

Structural basis for long-chain isoprenoid synthesis by cis-prenyltransferases.

Isoprenoids are synthesized by the prenyltransferase superfamily, which is subdivided according to the product stereoisomerism and length. In short- and medium-chain isoprenoids, product length correlates with active site volume. However, enzymes synthesizing long-chain products and rubber synthases fail to conform to this paradigm, because of an unexpectedly small active site. Here, we focused on the human cis-prenyltransferase complex (hcis-PT), residing at the endoplasmic reticulum membrane and playing a crucial role in protein glycosylation. Crystallographic investigation of hcis-PT along the reaction cycle revealed an outlet for the elongating product. Hydrogen-deuterium exchange mass spectrometry analysis showed that the hydrophobic active site core is flanked by dynamic regions consistent with separate inlet and outlet orifices. Last, using a fluorescence substrate analog, we show that product elongation and membrane association are closely correlated. Together, our results support direct membrane insertion of the elongating isoprenoid during catalysis, uncoupling active site volume from product length.