Radial Air Flow Research Articles

Effects of radial air flow quantity and location of an air curtain generator on dust pollution control at fully mechanized working face

To better understand the effects of radial air flow quantity and the location of air curtain generator on dust pollution control, the 2–1092 fully mechanized working face in Xinzhi coal mine (Huozhou Coal Electricity Group Co., Ltd., Shanxi, China) was numerically simulated in the present study. A full-scale physical model of the working face was established; then, based on airflow-dust particle two-phase flowing characteristics, the k-ε-Θ-kp mathematical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the effects of ventilation parameters on airflow migration and dust diffusion were numerically investigated using FLUENT. The results show that the increase of the radial air flow quantity (denoted as φ) and the distance of the air curtain generator from working face (denoted as dw) is beneficial to the formation of a dust-control air curtain. At a constant dw, the dust diffusion distance (denoted as D) decreases with the increase of φ. At a constant φ, D decreases with the increase of dw when a dust-control air curtain is formed; otherwise, the increase of dw leads to the increase of D. By analyzing the simulation results, the optimal ventilation parameters for 2–1092 fully mechanized working face and those working faces under similar production conditions are determined as: φ=240–270m3/min and dw=20–30m.

A canonical geometry to study wall filming and atomization in pre-filming coaxial swirl injectors

A coaxial twin counter-rotating air swirl prefilming injector with necessary optical access, is developed to visualize and quantify its internal fluid dynamics. This research injector consists of a simplex nozzle arranged at the center of two coaxial counter-rotating radial air flow swirlers, and two transparent coaxial tubes are attached, one each to the primary and secondary air swirl paths. Spray from the simplex nozzle is swirled by the primary air and impinges on the inner tube—the prefilmer, undergoes filming, and convects to the tube tip to form a liquid rim, which is sheared by the counter-rotating swirl into finer droplets. Stage-wise phase Doppler particle analyzer measurements indicate the final spray to be much finer than the simplex nozzle spray after undergoing the above processes. Time resolved laser induced fluorescence (TR-LIF) imaging techniques are applied to visualize the wall filming and primary atomization inside the injector. The simplex nozzle spray velocity under the influence of air swirl flow is measured using stereo-particle image velocimetry. The precessing vortex core from the primary swirl imparts a precessing motion to the simplex spray, which in turn induces a non-uniform filming on the prefilmer. The droplet impingement on the prefilmer leads to splashing and crater formation on the surface. The crater size distribution is obtained and compared to the droplet size of the injector spray before impingement. The film thickness variation on the prefilmer surface and the rim thickness are estimated from planar LIF experiments along with a long distance microscope. The thickness of the liquid rim is identified as a major factor in determining the final droplet size at the injector exit. These are correlated to SMD at the injector exit at different air flow rates.

Effect of suppressing dust by multi-direction whirling air curtain on fully mechanized mining face

A combined method of numerical simulation and field testing was adopted in this study in the interest of solving the problem of hard to control high concentrate dusts on a fully mechanized mining face. In addition, the dust suppression effect of a multi-direction whirling air curtain was studied in this paper. Under the influence of the wall attachment effect, the compressed air which blows out from the two-phase or three-phase radial outlets on the generator of the air curtain can form a multi-direction whirling air curtain, which can cover the whole roadway section of a fully mechanized mining face. The traditional method of controlling dust is a forcing system with exhaust overlap which has the major disadvantage of lacking a jet effect and consequently results in poor dust control. It is difficult to form the air flow field within the range of Lp⩽5Sr. However, due to the effect of this novel system, the radial airflow can be turned into axial airflow allowing fresh air to flow through the length of the heading. The air flow field which is good at controlling dust diffusion can be formed 12.8m from the heading face. Furthermore, the field measurement results show that before the application of a multi-direction whirling air curtain, the dust concentration is 348.6mg/m3 and 271.4mg/m3 respectively at the roadway cross-section measurement points which are 5m and 10m from the heading face. However, after the application of the multi-direction whirling air curtain, the dust concentration is only 61.2mg/m3 and 14.8mg/m3, respectively. Therefore, the dust control effect of a multi-direction whirling air curtain is obvious.

Optimization of outer diameter of Bernoulli gripper

A Bernoulli gripper is a pneumatic manipulator, capable of sucking and gripping. It is widely employed in automated production lines. It uses an axisymmetric radial airflow to create negative pressure that produces suction force. In this study, an important design parameter, namely, the outer diameter, is addressed both theoretically and experimentally. First, a theoretical model of the air flow between the gripper and the workpiece is created, based on which the theoretical formulas for calculating the pressure distribution and suction force are derived. It is found that the outer diameter of the gripper has a major impact on the suction force, and its design is closely related to the gap height and the supply mass flow rate. Then, the relationship between the outer diameter and the suction force and that between the gap height and the suction force are discussed, based on which a method for finding the optimal outer diameter is presented. Meanwhile, the pressure distribution is investigated in an attempt to explain the impact of the variation in the outer diameter on the flow phenomenon. Finally, the values of the optimal outer diameter for a range of supply mass flow rates are calculated and the tendency of the optimal outer diameter to change with the supply mass flow rate is revealed, which is of great importance to the design of a Bernoulli gripper.

Experimental Investigations on Effect of Particles Removal in Cleanroom with Non-Unidirectional Airflow

Efficient airflow delivery is key to achieve effective contamination control for a high-performance cleanroom. The influence of airflow organization on effect of particles removal in cleanroom with non-unidirectional airflow was investigated in this paper. A series of experiments were conducted on a cleanroom experimental platform with different airflow organization modes and supply air volume variation by frequency converter ( 40 to 50 Hz, 5Hz interval) on air-supply fan unit. The results showed that higher cleanliness could be gained at local area in cleanroom with radial airflow organization. Moreover, the outcomes from these experiments indicated that particle concentration at measuring points appeared more orderly when the cleanroom operated with radial airflow organization. The conclusion can be drawn that radial airflow can benefit contamination control at local area for cleanroom operation with non-unidirectional airflow when compared with ceiling-supply and wall-return airflow organization.

Theoretical and Experimental Study of Factors Affecting the Suction Force of a Bernoulli Gripper

AbstractA Bernoulli noncontact gripper can generate suction force to achieve noncontact handling by use of axisymmetric radial airflow. An experimental and theoretical study of the factors that affect the suction force and its variation is conducted. First, a theoretical model of the pressure distribution is developed, taking into consideration the inertial effect of airflow deceleration, viscous effect, total pressure of the central air-supply hole, and gap height between the gripper and the workpiece. Based on the model, the suction force is calculated. Then, the pressure distribution and suction force are measured experimentally. The theoretical calculation and experimental results reveal that the inertial effect causes a negative pressure distribution and resulting suction force, while the viscous effect and the total pressure of the central air supply give rise to positive distributions and a resulting repulsive force. Because the repulsive force is inversely proportional to the gap height to a highe...

Effect of Substrate Flexibility on the Pressure Distribution and Lifting Force Generated by a Bernoulli Gripper

This paper presents the modeling and analysis of the pressure distribution and lifting force generated by a Bernoulli gripper when handling flexible substrates such as thin silicon wafers. A Bernoulli gripper is essentially a radial airflow nozzle used to handle large and small, rigid and nonrigid materials by creating a low pressure region or vacuum between the gripper and material. Previous studies on Bernoulli gripping have analyzed the pressure distribution and lifting force for handling thick substrates that undergo negligible deformation. Since the lifting force produced by the gripper is a function of the gap between the handled object and the gripper, any deformation of the substrate will influence the gap and consequently the pressure distribution and lifting force. In this paper, the effect of substrate (thin silicon wafer) flexibility on the equilibrium wafer deformation, radial pressure distribution and lifting force is modeled and analyzed using a combination of computational fluid dynamics (CFD) modeling and finite element analysis. The equilibrium wafer deformation for different air flow rates is compared with experimental data and is shown to be in good agreement. In addition, the effect of wafer deformation on the pressure and lifting force are shown to be significant at higher volumetric airflow rates. The modeling and analysis approach presented in this paper is particularly useful for evaluating the effect of gripper variables on the handling stresses generated in thin silicon wafers and for gripper design optimization.

비접촉식 웨이퍼 그리퍼용 공압 파지식 헤드 설계

The recent manufacturing process in the thin wafers and flat panel necessitate new approaches to reduce handling fragile and surface-sensitive damage of components. This paper presents a new pneumatic levitation for non-contact handling of parts and substrates. This levitation can achieve non-contact handling by blowing air into an air pressure pick-up head with radial passages to generate a negative pressure region. Negative pressure is caused by the radial air flow by nozzle throat and through holes connecting to the bottom region. The numerical analysis deals with the levitational motion with different design factors. The dynamic motion is examined in terms of force balance(dynamic equilibrium) occurring to the flow field between two objects. The stable equilibrium position and the safe separation distance are determined by analyzing the local pressure distribution in the fluid motion. They make considerable design factors consisting the air pressure pick-up head. As a result, in case that the safe separation distance is beyond 0.7mm, the proposed pick-up head can levitate stably at the equilibrium position. Furthermore, it can provide little effect of torque, and obtain more wide picking region according to the head size.

Modeling and Prediction of the Flow, Pressure, and Holding Force Generated by a Bernoulli Handling Device

This paper presents the modeling and prediction of the air flow, pressure, and holding (or lifting) force produced by a noncontact Bernoulli gripper, which is essentially a radial air flow nozzle used to handle small and large rigid and nonrigid materials. Previous studies have demonstrated the turbulent behavior of the flow and the presence of a flow separation region at the nozzle of the gripper. Here, a Reynolds stress model has been implemented in a finite volume based segregated Reynolds-averaged Navier–Stokes solver. Compressible air is modeled to capture the effect of the high flow velocities generated by the nozzle. In addition an experimental setup is designed to validate the model. Experimental results of air pressure and lifting force agree favorably with those predicted by the model. This model could be used to understand the influence of handling variables such as the stand-off distance and air flow rate on the suction pressure distribution and lifting force acting on the handled object.

Measurement of permeability of continuous filament mat glass–fibre reinforcements by saturated radial airflow

The measurement of fibre reinforcement permeability is important for the understanding, optimisation and modelling of RTM and resin infusion processes. This work investigates the use of a saturated radial air flow experiment for measuring the permeability of continuous filament mat (CFM), which is a common reinforcement type used for industrial RTM parts. The use of air, rather than liquid resin, is cleaner, quicker and potentially easier to control. The paper considers the problems inherent in using a compressible fluid, instead of a liquid, for the measurement of permeability, and the requirements for maintaining laminar flow. It describes the instrumentation used for flow and pressure measurement, and the effect of varying flow rate. Results compare favourably with published permeability values based on liquid flow experiments, and are independent of flow rate within the range of values investigated.

Flows on the nozzle plate of an inkjet printhead

Flow patterns of ink layers on the nozzle plate of a piezo-driven printhead are investigated. Two different flow types are identified. First, a jet of droplets induces a radial airflow in the direction of the jet, which in turn causes a liquid flow towards the nozzle. Second, the movement of the meniscus in the nozzle causes an equally strong flow, but completely different flow patterns. The results are presented in a phase diagram with pulse amplitude and firing frequency as parameters.

2507 内面ブラストノズル(G05-2 噴流(2),G05 流体工学)

We know sandblasting techniques for wide processing on the work that is processing method to impinge gas-solid flow on the work. The inside sandblasting nozzle to process the inner surface of various pipes is developed. Mechanism of old type inside sandblasting nozzle is that the gas-solid flows supplying in center direction impinge on inner wall through the curved part of the nozzle. So the old type inside nozzle has disadvantage to have intense abrasion at the curved part of the nozzle. In this investigation we developed new type inner sandblasting nozzle applying the characteristics of the impinging jets that are produced by the impingement of the jet on small plate. The radial airflow blows uniformly the solid particles supplied through gap between inner and outer pipes to the wall and process the wall. So the new inside sandblasting nozzle is tuff for abrasion by the solid particles.

Ventilation rates of micro-climate air annulus of the clothing-skin system under periodic motion

A novel three-dimensional dynamic model is developed from first principles of mass and energy conservation of the modulated internal airflow in the variable annulus size between the clothing and the skin surface in presence of clothing apertures. The developed model solves for the flow and heat transfer problem in a finite length cylindrical annulus where the inner cylinder is oscillating within an outer fixed cylinder of porous fabric boundary. The changing annulus size induces pressure variations that cause air flow in the angular and the radial directions. In addition, axial airflow is present due to clothing open aperture to the atmosphere at one end of the annulus (sleeve or neck opening). The axial and angular flows in the trapped air layer are assumed locally governed by Womersley solution of time-periodic laminar flow in a plane channel in each direction. The 3-D model predicted the ventilation radial airflow through the fabric, the angular and axial airflow induced by the motion of the inner cylinder, and the sensible and latent heat losses from the skin due to ventilation with the presence of an open or closed aperture. Experiments were conducted using tracer gas method to measure time and space-averaged air ventilation rates induced by inner cylinder periodic motion within a fabric cylindrical sleeve at spacing amplitude ratio with respect to the mean of 0.8 for both closed and open aperture cases. The ventilation rates within the annulus predicted by the 3-D model agreed well with experimental data at higher frequencies. For closed aperture situation at an amplitude ratio of 0.8, the mean percentage errors of the measurements compared with the predicted values of the model were 52%, 27.5% and 6.7% corresponding to the frequencies of 30 rpm, 40 rpm, and 60 rpm, respectively. Measured ventilation rates for open aperture agreed well with predicted ventilation rates at high frequencies giving lower values of total air renewal than the closed aperture results where the measured reductions in total ventilation rate compared to closed aperture were 8.5% and 14.3% corresponding to the frequencies of 40 rpm and 60 rpm, respectively. In addition, the model results showed that under walking conditions, a permeable clothing system with an open aperture reduced the heat loss from the skin by less than 1% when compared to the closed aperture clothing system. These results are consistent with previously published empirical data on air layer resistance for open and closed aperture of high air permeable fabric.

2913 フォイルディスクの基礎的研究 : 2次流れについて(S64-1 トライボロジーの基礎と応用(1),S64 トライボロジーの基礎と応用)

Warping of foil disk turning over a flat solid surface was studied in connection with a magnetic flexible memory devices. Experiments were carried out to measure the rotating speed of moire-topography pattern due to the warping and to measure, by means of a hot-wire anemometer, the blow-off velocity of radial air flow from edge of the disk under various conditions. It was fund that the warping was caused by the secondary air flow between the foil disk and the solid surface

2641 爪チャックの回転に起因するCNC旋盤加工空間内の空気流挙動の数値解析(G13 新加工技術,G13 生産加工・工作機械)

In order to solve some problems relating to airflow caused by rotating chuck of a CNC lathe or turning center, the airflow in a closed space assumed a machining space is investigated by the MAC (Maker-and-Cell) method. An analytical model and calculated grids are a three-dimensional space assumed a machining space and the staggered grids respectively. The analytical results have good accordance with characteristic airflow patterns observed by means of the tuft and tracer methods; (1) A radial airflow blowing from the rotating chuck strikes the panel near the headstock side, and then goes in the direction of tailstock through the surface of panel. (2) An entrained-flow exists around the rotating chuck. (3) The separation of airflow from the panel is observed on the left, right, upper and bottom panels.

Lubricant flow under a flying head on a thin-film disk

The thickness of lubricant on magnetic disk surface decreases because of disk rotation and head flying. In order to simulate the lubricant flow on rotating disks in magnetic disk drives, we developed a finite-element-method code, which takes into account the effects of centrifugal force and the shear force caused by the air flow. Using this code, we studied the change in lubricant thickness on rotating magnetic disks with and without flying head. We first compared the measured and simulated decreases in lubricant thickness on rotating disks without flying head. They agreed well in two cases with and without radial air flow on the disk. We considered this proved our code. We then compared the measured and simulated changes in lubricant thickness under a two rail flying head. They had similar shapes with a valley under each rail. However, the calculated change was two orders of magnitude smaller than the measured change. This discrepancy between them must be eliminated to design future disk drives with simulation.

PA—Precision Agriculture: Variation of Spray Deposit and Loss with Air-jet Directions applied in Orchards

Axial fans with a radial air flow have been most commonly used in fruit growing areas. These generate a large radial plume which is poorly targeted for modern intensive orchards. A high-volume directed air-jet system (HVDAS) sprayer, based on a standard axial fan has been developed to determine the influence of the air jet direction generated by the sprayer on the in-canopy spray deposit and off-target loss in orchards of different tree row volumes. Three sprayers with axial fans but with different air discharge systems were compared (conventional, cross-flow, HVDAS with the air spouts directed at 20 and at 40° upwards). The treatments were carried out in dwarf and semi-dwarf orchards. In modern orchards, the HVDAS sprayer with air spouts set 20° upwards produced a higher in-canopy deposit and a lower off-target loss than the conventional and cross-flow sprayers. Further raising of the air spouts directing the air-jets at 40° upwards, increased the spray loss and enhanced the risk of airborne drift without any influence on spray deposit.

Analytical solution of transient radial air flow to an extraction well

The non-linear partial differential equation describing the transient radial flow of air towards an extraction well has attracted extensive attention. Several linearized analytical solutions have been derived by adapting analytical solutions for groundwater flow. However, the validity of these linearized solutions remains unjustified because the exact non-linear solution for transient radial air flow to a well has not been available. In this study, an exact analytical solution is obtained using the Boltzmann transformation, and the pressure is calculated using the Newton–Raphson method. The solution provides a means for evaluating linearized analytical solutions and verifying numerical models. Examples are presented to test linearized analytical solutions for air flow towards an extraction well. Tests indicate that errors in pressure calculation using linearized analytical solutions are relatively small when the governing equation and boundary conditions are linearized with respect to pressure-squared. However, the errors owing to linearization are unacceptably large when the governing equation and boundary conditions are linearized with respect to pressure. Linearization with respect to pressure-squared is therefore recommended in adapting groundwater flow solutions. The new technique developed in this paper results in a solution that is simple to implement and requires very little computational effort. The technique can be applied to solve many other nonlinear diffusion problems.

Integral Method for Calculating the Characteristics of a Turbulent Boundary Layer on a Rotating Disk: Quadratic Approximation of the Tangent of the Flow Swirl Angle

An improved approximation of the radial velocity profile observed in a turbulent boundary layer on a rotating disk is proposed on the basis of the assumption that the tangent of the swirl angle of the flow is described by a quadratic function. The integral method based on this assumption provides better agreement between the computational and experimental results for the radial velocity profile, the near-wall value of the tangent of the swirl angle, and the flow rate through the boundary layer. For the coefficient of the frictional moment, the accuracy achieved with the proposed method is the same as that available by the Karman method. The solutions to the equations describing the boundary layer are compared to the computational data reported in the literature for three different cases: a radial air flow around the disk, a rotation of the fluid by the law typical of a solid body, and a medium with the Ekman layers.

The reduction of thermal nitrogen oxides (NOx) emission using staged combustion in furnace

The experimental study described in this paper is to investigate the control of thermal nitrogen oxides emissions from a 2.28 MW gas-fired test furnace. Tests, including changing axial or radial air flow rate, adding cooling water, and adding staged air, were performed to characterize and optimize the fuel-rich burning zone and the fuel-lean burnout zone independently. Detailed measurements of O2, CO2, CO, NO and NOx were made at the fuel-rich burning zone and furnace exit. The influence of forming CO, NO and NOx was examined. Results indicated that adding staged air in the fuel-rich burning zone (75 cm from burner) will reduce the maximum NO and NOx emissions. Adding cooling water in a right position may further lower the NO and NOx emissions. In addition, the least formation of thermal nitrogen oxides in the first stage fuel-rich burning zone will occur at the stoichiometric ratio’s inverse value, (φ1)−1, 0.65 to 0.7.