Suction Holes Research Articles

The substantiation of parameters of sowing machine with adaptive dosing elements for seeding of corn

For sowing of corn precision seeders are used, one of the most complex and responsible details of which is a sowing machine. The purpose of this study is to substantiate the rational design and parameters of the dosing elements and the «superfluous» seeds seeder of the vacuum sowing device, which ensure an even increase in the supply of corn seeds to the furrow. A vacuum sowing machine is proposed for use in production, in which elongated suction holes are made on the sowing disk in such a way that their long axes are oriented to a radial direction at α angle. In addition, in the design of the sowing apparatus, the thickness of the first three projections of seeder for «superfluous» seeds is proposed to be made stepwise. Experiments carried out on the matrix of the orthogonal plan of the second order showed that the following parameters and tuning regimes of such a machine are rational for sowing corn seeds: width of suction holes tдэ = 3 mm; the smallest slot width in the vacuum chamber liner t = 3,0...3,5 mm; exhaustion in the vacuum chamber H = 5 kPa; thickness of the input edge of the working part of the “superfluous” seeds seeder h = 1,5 mm; angle of deviation of the longitudinal axes of the suction holes of the sowing disc from the radial direction α = 12...15 deg. Under laboratory conditions the machine provided the frequency of single seed feeds p1 = 99,0...99,5 %, which is close to the technological optimum. At the same time, the quality of seed dosing remained stable even with a significant increase in the angular velocity of the sowing disk.

118 Size Effect of Savonius Rotor with Suction Holes

118 Size Effect of Savonius Rotor with Suction Holes

Suction control of laminar separation bubble over an airfoil at low Reynolds number

A laminar separation bubble appears generally on the NACA2415 airfoil at low Reynolds number. In this paper, suction control of the laminar separation bubble over the NACA2415 airfoil at low Reynolds number are simulated. The effects of suction control on the flow field and the aerodynamic characteristics of the airfoil are focused on at different angles of attack. Numerical simulations show that employing the γ-Reθt transition model coupling the k–ω shear stress transport turbulence model can predict the laminar separation bubbles accurately. The results indicate that suction control can delay the transition, decrease the velocity gradient of the boundary layer and inhibit the production of the separation bubble. The effect of the suction control becomes better with the suction location getting closer to the separation bubble and the suction speed (the suction gas speed of suction hole) getting faster. The figure of merit is introduced to evaluate energy consumption of the suction control. In consideration of the economic effects, the suction control is suitable for the larger angle of attack situation at low Reynolds number.

Main characteristics of suction control of flow separation of an airfoil at low Reynolds numbers

The suction control of flow separation of a NACA0012 airfoil is studied numerically for Reynolds number Re=104, angle of attack α=2°, 4°, 6°, and 8°, and Re=105, α=4°. The suppression effects of suction are studied considering many parameters such as suction coefficient, location, angle, hole width, and porosity. The variations in energy consumption and lift–drag ratio during the control process are used for evaluating the control effects.

Research of the suction flow control on wings at low Reynolds numbers

Laminar separation and transition have significant effects on aerodynamic characteristics of the wing under the condition of low Reynolds numbers. Using the flow control methods to delay and eliminate laminar separation has great significance. This study uses the method combined with water tunnel test and numerical calculation to research the effects of suction flow control on the flow state and aerodynamic force of the wing at low Reynolds numbers. The effects of suction flow rate and suction location on laminar separation, transition and aerodynamic performance of the wing are further researched. The results of the research show that, the suction can control laminar separation and transition effectively, when the suction holes are in the interior of the separation bubble, and close to the separation point, the suction has the best control effect. When the Reynolds number is Re = 3.0 × 105, the suction flow control can make the lift-to-drag ratio of the wing increase by 8.62%, and the aerodynamic characteristics of the wing are improved effectively.

Numerical investigation of boundary layer suction on certain highly loaded aspirated compressor at low speeds

Boundary layer suction is considered to be an available approach to restraining or even eliminating flow separation and to improve the aerodynamic performance of the compressor. In this paper, a highly loaded axial-flow aspirated compressor based on a low-reaction design concept is investigated in detail to find an appropriate flow control strategy for boundary layer suction to achieve significant performance benefit. The flow control strategy consists mainly of the arrangement of suction hole and the aspirated flow rate. The geometrical models including aspiration cannulas, stator cavity and aspiration channel are novelly applied in this research to approach a real engineering application. Complete compressor maps are predicted by a three-dimensional computational fluid dynamics simulation. The distribution of the typical aerodynamic parameters and the partial flow structures are analysed at design and off-design conditions. Three-dimensional separation near the stall point is effectively suppressed by the aspiration on both hub and shroud, and better performance is achieved by a reasonable increase of aspirated flow rate; a peak efficiency of 0.91 and a total pressure ratio of 1.055 are attained at a total aspirated flow rate of 0.024 kg/s per passage. However, sudden turning of compressor maps at low inlet flow rate occurs without the aspiration on shroud, and a noticeable deterioration in performance occurs with the decreasing of the inlet flow rate. The main reason of performance deterioration is that the flow control efficiency of aspiration is not enough for effectively suppressing three-dimensional separation near the casing corner. The difference in the aspirated flow source is owed to the distinct flow feature at various locations caused by the aspiration efficiency of suction holes. A partial auto-readjustment feature of the suction flow rate with increasing flow separation has been found. The boundary layer suction with an appropriate flow control strategy is necessary for a higher efficiency, highly loaded aspiration compressor.

Passive Jet Flow Control Method for Suppressing Unsteady Vortex Shedding from a Circular Cylinder

AbstractA numerical simulation is performed to investigate a passive jet flow control method for suppressing the alternating vortex shedding from the circular cylinder. A hollow pipe is tightly set on the circular cylinder, and two arrangement cases for the holes are employed: one is a five-hole case, which means that five suction holes are set near the front stagnation point and five jet holes set near the rear stagnation point of the cylinder. The other is the full-hole case, which means the holes are equidistantly arranged on the hollow pipe. The incoming flow enters the suction holes and jets into the near wake from the outlet holes. Consequently, the wake vortex shedding alternately is manipulated or destroyed. The numerical simulations of baseline cases (without control) are first conducted to verify the reliability of the numerical model. Next, the two controlled cases (five hole-case and full-hole case) are investigated at the Reynolds number R=103−105. It is found that a remarkable mitigation for...

Wake control of vortex shedding based on spanwise suction of a bridge section model using Delayed Detached Eddy Simulation

In this paper, the DDES (Delayed Detached Eddy Simulation) is applied to study the spanwise suction control effect on wind-induced effect of a static bridge deck. Isolated suction holes are arranged on the lower surface of the test model in spanwise direction, and based on previous studies of similar bluff body, a proper distance of spanwise suction was chosen to trigger or amplify the most unstable secondary instability (i.e. Mode A) in wake. The simulation results show that the suction arranged close to the wake has the best control effect on reducing the fluctuating aerodynamic forces. Due to the mean-velocity modification by isolated spanwise suction, the virtual aerodynamic shape modification is generated, which could act as spanwise perturbation to suppress spanwise vortexes. The results indicate that the spanwise suction could trigger or amplify the Mode A instability, and hence lead to the dislocation of the spanwsie vortex or even completely suppress the spanwise vortex. In addition, the spanwise suction control can surpress spanwise vortex shedding in a wide Re range.

Vacuum chucking assist sheet for fixing flexible sheets during the printing process

A vacuum chuck is often used to fix substrates in the field of electronic device fabrication including printing of the device electrodes. A conventional vacuum chuck plate locally sucks only where suction holes exist. However, when we employ a film as the substrate to be printed, suction from the holes causes the film distortion, which results in misprinting. Thus, we have newly developed a chucking assist sheet to fix a film substrate on a vacuum chuck stage for high-quality electrode printing. When printing is performed, the sheet is located between the film substrate and the vacuum chuck stage. The developed sheet is composed of lower and upper layers of woven stainless steel mesh and non-woven fabric, respectively, and such a structure can significantly decrease misprinting resulting from the film distortion caused by suction. In the present paper, we present the design concept of this chucking assist sheet and details of its features.

Free sink vortex Ekman suction-extraction evolution mechanism

The suction-extraction phenomenon occurs in the formation process of free sink vortex (bathtub vortex), and it is a complex gas-liquid coupling matter. The Ekman layer coupling and its evolution mechanism involved in the above matter possess important scientific value and practical engineering significance. To address the above issue, a modeling and analytical method for the Ekman suction-extraction evolution mechanism of free sink vortex is proposed.#br#Based on the multiphase volume of fluid model and turbulent kinetic energy-dissipation (k-ε) model, a gas-liquid two-phase fluid dynamic model for free sink vortex Ekman suction-extraction is set up. Considering the rotating and shearing characteristics of sink vortex, a two-phase surface is reconstructed by piecewise linear interface construction method. Based on the above models, the internal relations between initial rotation velocity component, drainage capacity and Ekman suction-extraction are investigated, and the corresponding flow field profile regularities are revealed.#br#According to the results of a series of numerical instances, some regularities are obtained as follows. 1) If the initial velocity disturbance is variable, the distances of the suction and extraction holes from the container bottom both keep constant. In the suction stage, the suction hole is located at a fixed position above the container bottom surface, and the extraction hole is in the plane of the bottom surface. 2) If the initial disturbance is enhanced, the rotation velocity of the suction stage increases, and the suction and extraction heights and Ekman layer thickness become larger, while Ekman suction-extraction intensities of suction, extraction and penetration stages turn weaker. 3) If the initial disturbance is invariable, the heights of Ekman suction and extraction remain unchanged, and are independent of drainage capacity. 4) The small-scale vortexes separated from the large-scale ones in the bottom corner of container take on a phenomenon of flow around by a right-angle, which is caused by the viscosity of Ekman boundary layer and the potential flow of the sink hole. 5) Considering the stream line profiles of suction and extraction stages, the dispersion of stream lines keeps constant with the time going by, and the stream lines near the central region of vortex tend to be converged by increasing the gas-liquid coupling.#br#In general, the results can offer useful reference to the research work of free sink vortex formation mechanism, and provide technical supports for vortex suppression control of the areas of metallurgy pouring, chemistry separation and hydraulic drainage. The subsequent researches of the fractal based sink vortex evolution mechanism and lattice Boltzmann based phase surface tracing will be carried out.

Numerical investigation of steady suction control of flow around a circular cylinder

This paper numerically investigates the effectiveness of the control of steady suction on a stationary circular cylinder with several isolated suction holes on the surface at a subcritical Reynolds number. The control effectiveness as a function of the azimuthal position, spanwise spacing and suction flow rate of the suction holes on the control of the aerodynamic forces on the cylinder and the suppression of alternate vortex shedding are taken into account. The study of the azimuthal location of the suction holes indicates that azimuthal angles of θ=90° and 270°, which are close to the separation point, provide the most substantial decreases in the aerodynamic forces. When restricted to the most effective azimuthal angle, a remarkable control effectiveness can be achieved when the axial spacing between two neighboring suction holes is less than a minimum value even under a small suction momentum coefficient. However, if the axial spacing exceeds the minimum spacing, the control effectiveness will not be saturated even under a very large suction momentum coefficient. Thus, the cause of the effective aerodynamic force control is suggested to be a result of obvious three-dimensional phenomenon in the near wake, which is characterized by the generation of a convergent flow between two neighboring suction hole sections and a stronger, larger three-dimensional vortex pair adjacent to the convergent flow. It has been suggested that this strongly three-dimensional flow pattern is induced by the strong interaction between two neighboring but counter-rotating three-dimensional vortices separately produced by two neighboring suction holes. Moreover, the effects of such three-dimensional flow patterns are investigated in detail based on variations in the flow field and sectional aerodynamic forces in different cross sections. Finally, the upper limit of the axial spacing between two neighboring suction holes to form such a three-dimensional flow pattern is suggested to be between 0.75D and 1.5D when the suction flow rate exceeds a certain value.

The modified liposuction-curettage cannula for the treatment of secondary axillary bromhidrosis with subcutaneous scarring.

The modified liposuction-curettage cannula for the treatment of secondary axillary bromhidrosis with subcutaneous scarring.

GS24 分岐による濃度低下現象を用いた回転フィルターの開発 : 処理能力の向上

By using the phenomena that the concentration of particles decreased by passing through branch pipes, a rotating filter was developed to remove particles in two phase fluid. Its filtering effect about 2.1mm particles was explained well by the theory of branch pipes. In this report, filtering effects about 8.5 μm particles were studied. It was found that the filtering effects were better than the theoretical values, because the concentration of particle in the boundary layer on the rotating disk was less than that outside of boundary layer. Next, number of suction holes was increased from 8 to 12, and their filtering effects were studied. It was found that the filtering effects decreased with more than 9 holes.

The influence of shape and type of sowing disc cells on the seed dosage quality

Parameters of peripherally located cells were substantiated, and the influence of their step on the seeds uniformity in a row was determined. Difference in the seeds pitch in the sowing disk for sugar beet seeds ranges from 2.6 to 6.6 mm for round-shaped holes, and from 0 to 1 mm for cells, formed by a suction hole and shovel. That is, using cells, formed by the suction hole and shovel, will provide greater dosage uniformity initially. According to the research results, section of sowing machine for seeding cultivated crops, in which the proposed pneumatic device with a peripheral arrangement of cells and passive device for removing excess seeds by inertia method was used, was designed to exclude the major shortcomings of modern pneumatic sowing machines and improve their performance.

Analysis of resistance torque on the compact spinning with suction groove

The compact spinning with suction groove can eliminate or decrease the spinning triangle by airflow compacting and shape condensing of the groove, so the yarn hairiness can be reduced effectively for long staple fiber. But the resistance torques produced by the spinning tension and the negative pressure of airflow influence the twist propagation. This paper analyzes variation of the friction coefficient between the fiber bundles and the groove. The transfer process of the moment of the spinning tension and airflow is studied in the variation of the friction coefficient. The expression of the resistance torque is established in the gathering area. The results show that the many factors influence the resistance torque, such as the horizontal friction coeffecient between the fiber bundles and the groove, the spinning tension and the negative pressure, as well as the angle between two suction holes etc. The proper negative pressure and the spinning tension can prevent twist propagation, and can reduce the yarn hairiness and improve the yarn quality.

A numerical study on the lubrication system for a hermetic reciprocating compressor used in household refrigerators

This study presents a numerical investigation of an oil supply system for a hermetic reciprocating compressor used in household refrigerators. It is aimed to investigate the geometric parameters of the crankshaft affecting the mass flow rate of the lubricant released from the outlet of the crankshaft. The change of the mass flow rate from the outlet of the crankshaft associated with helix-screw indicates that with reducing the screw pitch, the mass flow rate decreases. An important finding is that increasing the depth of the helical channel plays a more significant role than increasing the width of the helical channel. The mass flow rate increases when the distance between the suction hole of the crankshaft and the oil sump bottom increases. The wall thickness of the crankshaft does not significantly affect the mass flow rate whereas it plays a crucial role in formation of the vortices around the crankshaft.

Influence of air supply on the performance and internal flow characteristics of a cross flow turbine

This study attempts to improve the efficiency of a given type of cross flow turbine by supplying air from air suction holes. A newly developed air supply method is adopted. CFD analysis of the cross flow turbine is carried out to investigate the performance and internal flow characteristics of the turbine in detail. The air layer prevents shock loss between water flow and axis and suppresses recirculation flow in the runner passage. Hence, it is necessary to measure the amount of air layer in the runner passage and examine its effect on the performance of the cross flow turbine. The result shows that the turbine efficiency has improved more as the newly developed air supply method is applied effectively.

Internal Flow Field Analysis of Air-Suction Roller-Type Precision Metering Device

In order to analyze the influence of structure parameter of air-suction roller-type precision metering device on the flow velocity and pressure, the flow field was calculation and simulation. Take the compressibility and the viscosity of the real gas into account, the N-S equations, RNG k-ε turbulence model and wall function were applied to measure the flow rate and pressure of the outlet under the conditions of changing the area of the suction holes and the diameter of shaft. The results revealed that compared with the shaft holes area, the diameter of center axis have a marked influence on the flow velocity and pressure of outlet. When the area of suction holes is constant, with the increase of shaft diameter, the outlet velocity increased and pressure decreased; when the diameter of axle is constant, with the shaft holes area increase, the outlet velocity increased and pressure decreased.

Simulation of Single Cell Trapping Via Hydrodynamic Manipulation

Microfluidic devices are important for the single cell analysis such as cell mechanical and electrical characterization. Single cell characterization could be related to many significant applications including early disease diagnosis. However to perform the single cell manipulation, firstly a single cell have to be isolated and a platform for the cell manipulation have to be provided. One of the methods to trap a single cell is by using hydrodynamic trapping in the microfluidic channel. This study provides a finite element model for single cell trapping for a yeast cell model. The objectives of the simulations are to obtain the appropriate channels’ geometry and optimized ratio of the fluid’s inlet and suction flow rate to trap a single yeast cell. Trap channel was designed to trap a 5μm yeast cell with a suction hole placed in the end of the trap channel. Design geometry and the ratio of fluid flow rates for the cell trapping model were studied using the hydrodynamic resistance concept. The analysis was carried out using numerical solutions from the finite element ABAQUS-FEA software. Using the cell trapping model, a single yeast cell able to be trapped into the trap channel with optimized channel’s suction hole’s geometry and appropriate fluid’s inlet and suction flow rate ratio. The appropriate QTrap/QMain ratio to perform cell trapping using hydrodynamic resistance concept is the ratio value above 1. A 5 μm yeast cell model able to be trap inside a trap channel with the height, width and length of 7 μm by manipulating the suction hole’s flow rate of 1.5 and 2.0 μm of height, 7 and 3 μm of length and width, respectively which situated at the centre edge of the trap channel.

SIMULATION OF THE PROCESS OF FLOW SEPARATION AT THE ENTRANCE OF SQUARE ASPIRATING PORT

We consider the flow at the inlet to the suction sq uare hole with sharp edges, which is located in an infinite space. The purpose of this study is to con struct a mathematical model of flow separation at t he entrance to square suction canal with sharp edges, located in infinite space, by using square vortex frameworks. As a part of ideology of the method of discrete vortices in the non-stationary quasiaxisymmetric formulation, we constructed the mathematical model of separated flow at the inlet to the square aspirating pipe and its software-algorithmic implementation. We have determined the velocity field at the entrance to suction channel and a line of flow separation. Determine the velocity field i n typical cross-sections of the suction channel, dime nsions of the efficient absorption, compression rat io of the jet. Were received analytical formulas for calc ulating separation surfaces current. Profiling the entrance opening of the suction hole detected on th e outlines separation surface will improve the acou stic and aerodynamic properties of the exhaust systems. The obtained results can be useful for designing of local exhaust ventilation of reduced energy consump tion.