Air caloric test: irrigation technique

The technique of using air to perform the caloric test is discussed. Greater temperature differences and larger volumes of air are needed to achieve stimulations equal to those caused by water irrigations. Special consideration must be given to the design and operation of air irrigation equipment. The effects of irrigating a wet canal and of misdirecting the air jet are discussed. A new air irrigation apparatus is described.     

Effect of Jet Air Content on Plunge Pool Scour

The effect of air discharge on plunge pool scour was investigated by using a simplified experimental configuration. Instead of considering the complete arrangement involving chute and deflector resulting in an air-water jet impinging on a sediment surface, the mixture flow was produced with a circular pipe for which the air concentration and the jet diameter close to impact on the free water surface are known. The results of this study were primarily directed to the definition of a three-phase Froude number that accounts for the combined effects of an air-water mixture jet on scour. The analysis of data allows simple estimates of the scour geometry including a generalized scour profile, the width of scour, and the temporal advance of the extreme scour depths. It was pointed out that for a certain water velocity and selected grain characteristics, the addition of air to the jet results in an increase of scour depth. However, if the reference would be the air-water mixture velocity, scour depth decreases significantly by the addition of air to the jet.     

The physical behavior of a gas jet injected horizontally into liquid metal

The gas fraction and bubble frequency distributions in a submerged air jet, injected horizontally into mercury, have been measured under isothermal, nonreactive conditions for nozzle diameters of 0.325 and 0.476 cm and jet Froude numbers ranging from 20.5 to 288. The measurements reveal that the jets expand extremely rapidly upon discharge from the nozzle with an initial expansion angle of 150 to 155 deg. This value, which is over seven times greater than is found with air jets in water, indicates that the physical properties of the liquid exert considerable influence on the jet behavior. In conjunction with the rapid expansion, the air jets in mercury were also found to penetrate extensively behind the nozzle, and in many respects resembled a vertically injected jet. The extent of backward penetration of the jets was constant for all blowing conditions studied while the forward penetration increased with both increasing jet Froude number and nozzle diameter. The measured jet penetration in both the forward and backward directions were considerably larger than expected from model predictions. The core of the jets consists of a high concentration of gas bubbles. Both the gas volume fraction and bubble frequency in the core increase with increasing jet Froude number and nozzle diameter. The gas concentration and bubble frequency decrease with increasing distance along the jet trajectory due presumably to entrainment of liquid metal and bubble coalescence. On the basis of these findings, it is likely that process jets, such as are injected into copper converters, also expand rapidly and penetrate only a short distance into the bath. Thus rather than reacting in the middle of the bath, the jets may be impinging on the backwall refractory and contributing to the erosion observed there.     

Experimental Study of Flow in a Vortex Drop Shaft

Model experiments were conducted to investigate the performance of a vortex drop structure with a relatively small height to diameter ratio. Detailed measurements of wall pressure and water thickness of annular jet flow were obtained along the vertical drop shaft, and the rate of air entrainment was measured. The results confirmed the high efficiency of energy dissipation in the vortex drop structure even for a relatively small drop height. The air entrainment rate was found to be significant, and good correlation was observed between the rate of air entrainment and the water jet velocity. The one-dimensional frictional free-vortex flow model was extended to include the effects of pressure forces. While the energy loss in the drop shaft can be simulated by correcting the friction factor, both the frictional model and the extended model significantly underpredict the wall pressure.     

完全膨胀的目标设计改进喷砂枪喷管

为改变普通喷砂枪效率低下只适用于处理小型工件的现状,运用CFD方法系统计算了Laval喷管和同口径普通收缩喷管的流场,提出并论证了以完全膨胀状态气流为目标的Laval喷管设计观点。以提高喷气速度和超声速气流长度为有效途径提高喷砂枪效率。     

Behavior of an Air Curtain Subjected to Transversal Pressure Variations

The mass transfer and the influence of sudden external perturbations on the behavior of an air curtain are evaluated by means of experimental and numerical studies. The air curtain, consisting of a plane air jet, is combined with a laminar flow unit. They constitute an “open” protection device intended to protect a localized area against any external airborne contamination. The external perturbations are characterized by fast pressure changes, such as drafts which can be experienced in a room. Numerical and experimental results both show that the air jet is strongly perturbed by the pressure gradient in the lateral direction. The jet is subjected to a brutal back and forth motion, breaks, and generates a swirl which is responsible for pollution entrainment inside the protected area. Gas concentration measurements suggested that there is an inlet jet velocity for which the pollution is minimal. These experimental results, corresponding to a strongly unsteady flow, were qualitatively well-predicted by the standard k-ε model.     

Aeration Characteristics of Ski Jump Jets

Scour downstream of ski jumps may be avoided by jet deflection to an area where the energy dissipation is accomplished. The main purpose of this experimental study was the analysis of the jet air entrainment downstream of a ski jump, both for pure water and preaerated approach flow conditions. A systematic variation of the Froude number and the flow depth in the approach flow channel resulted in a range of discharge characteristics, whereas the geometry of the ski jump was maintained for all tests. The air concentration profile was measured at different locations downstream from the ski jump to evaluate the: (1) jet air concentration distribution; (2) location of minimum air concentration along the mixture flow jet and development of the minimum and the cross-sectional average air concentrations; (3) jet trajectories; and (4) process of air entrainment characteristics and jet disintegration. The results demonstrate the significant effect of the approach flow Froude number, the approach flow depth, and of preaeration on jet disintegration.     

高速电弧喷涂枪结构对雾化性能影响的分析

使用流体分析软件建立了高速电弧喷涂枪雾化气流场的三维模型,计算了喷枪气流速度场的分布特征,并基于数值模拟优化设计了新型陶瓷喷嘴结构的高速电弧喷涂枪,通过高速摄像法测试了高速电弧喷涂枪的雾化性能。结果表明,高速电弧喷涂枪的气体射流高速区分布集中、速度值高、有利于熔滴的雾化,喷涂试验也显示设计的喷枪焰流张角小、熔滴飞行速度、温度的分布有利于涂层的沉积。     

Water model study of horizontal molten steel-Ar two-phase jet in a continuous casting mold

A water model study was carried out to understand the behavior of a molten steel and Ar gas two-phase jet issuing out of a submerged entrance nozzle in continuous casting modls. A mixture of water and air was injected horizontally from a circular pipe settled flush with the narrow face of a mold having a rectangular cross section. The water-air two-phase jet thus generated was pulled upward through the effect of buoyancy force acting on air bubbles. The deflection of the jet in the upward direction was correlated by introducing a velocity scale, which could characterize the upward moving velocity of the jet. The mean velocity and turbulence components of water flow were measured with a laser Doppler velocimeter. Empirical equations were proposed for predicting the two velocity components.     

铜镍矿氧气顶吹自热熔炼氧枪射流速度分布规律

运用相似理论,研究了氧气顶吹自热熔炼炉氧枪射流速度分布规律,并建立了相应的数学模型。不同截面上氧枪射流速度的分布特点为随着与氧枪喷口距离的增加,速度分布趋于平缓。无因次速度分布方程为：ｕ／ｕｍ＝「１－（ｒ／ｒｂ）＾１．５０３２」＾１．８６４２;同一截面上随着径向距离的增加,射流速度降低,且径向速度分布具有自模性。此研究对完善氧气顶吹自热熔炼炉的实际生产操作具有指导意义。     

Studies of interface deformations in single- and multi-layered liquid baths due to an impinging gas jet

An impinging gas jet on a molten bath having a slag layer on top is encountered in various metal processing operations. The impinging region was studied using a physical model consisting of an air jet and water bath. Kerosene and corn oil were used as the second layer to investigate the role of the slag layer properties on interface shape and bath circulation. The interface shapes were measured both photographically and by using a surface-tracking resistance probe. The limiting condition at which the jet breaks through the kerosene or corn oil layer and reaches the water layer was determined experimentally. A phenomenological model for the prediction of penetration depth is developed for both short and long jet heights for liquid baths with and without a second liquid layer on top.     

Studies on the behaviour of mist jet and its cooling capacity of hot steel surface

The present study is concerned with the design of mist nozzle to produce air/water mist jet, and to investigate the behaviour of mist jet and its capacity to cool the hot steel surface. The behaviour of the mist jet is studied by collecting water at different axial distances. Radial water flux profile is correlated with a Gaussian type of distribution function under a wide range of experimental conditions. Maximum water flux in the mist jet is correlated with the downstream axial distance and water-loading ratio. Water-loading ratio is found to influence water flux more strongly than axial distance. Radius of the mist jet is correlated with the downstream distance. It is found that the mist jet cools a crack-sensitive steel without Cracking and, at the same time, produces a martensite type of structure.     

Confinement Effects in Shallow-Water Jets

This paper documents measurements of the mean velocity field and turbulence statistics of an isothermal, round jet entering a shallow layer of water. The lower boundary of the jet was a solid wall and the upper boundary a free surface. The jet axis was midway between the solid wall and the free surface in all cases. Experiments were performed at a Reynolds number of 22,500 for water layer depths 15, 10, and 5?times the jet exit diameter (9?mm). Particle image velocimetry measurements were made on vertical and horizontal planes—both containing the axis of the jet. The measurements were taken from 10 to 80 jet diameters downstream. Results showed that, for the highly confined cases at downstream locations, the axial velocity was quite uniform over the depth, with a mild peak below the jet axis. In the horizontal plane, the velocity profiles were slightly narrower than the free jet profile, but in the vertical plane, they were wider. The mean vertical velocity profiles showed that entrainment was suppressed in the vertical direction. At the same time, the lateral velocity profiles indicate that fluid flows from the sides toward the jet centerline. For the shallow cases, the mean vertical velocity becomes negative over most of the depth at downstream locations, indicating that this inflow from the sides is directed downward toward the solid wall. The relative turbulence intensity results were suppressed in the axial and vertical directions and mildly enhanced in the lateral direction. As well, the Reynolds shear stress in the vertical plane was significantly reduced by the vertical confinement, while in the horizontal plane it was only slightly affected by the confinement.     

Experimental Investigation on Influence of Aeration on Plane Jet Scour

A series of experiments was conducted to investigate the influence of aeration on plane jet scour. The scour holes caused by the aerated and the nonaerated jets were compared under the same conditions of jet velocity, water discharge per unit width, and tailwater depth. A quantitative relationship between the air concentration of jet and the relative scour depth was established, which is not affected by jet velocity and water discharge per unit width. The profile of the scour hole was found to mainly depend on the scour depth under the same conditions of bed material and tailwater depth and affected very little by the air concentration itself in the test range. The aeration influences the shape of the scour hole mainly through decreasing the scour depth. The scour holes formed under aerated and nonaerated conditions are self-similar.     

Production of bronze powders by water jet cooled rotating disc atomisation

Abstract

New type of water jet cooled rotating disc atomisation unit was designed and constructed. The raw material was melted in graphite crucible with high frequency induction heating, and atomisation was performed in high purity argon gas atmosphere. Cu–10Sn alloy was atomised to investigate the effect of production parameters, such as disc speed, disc surface condition, liquid metal flowrate, disc fin number and superheat of liquid metal with respect to mean particle size and powder yield rate. The produced powders appeared spherical, rounded, ligamentous, irregular and flaky, depending on particle size. The mean particle size of produced powders was in the range of 100–250 μm with 65–85% powder yield rate depending of atomisation parameters. The ZrO₂ material coated disc with four fins gave the finer mean particle size and higher powder yield rate in comparison with uncoated disc with two fins.     

Modeling of Evaporation Reduction in Drip Irrigation System

Surface drip irrigation is an efficient system for delivering water to crops; however, conditions at the soil surface affect evaporation rate and efficiency. A method is proposed, sand tube irrigation (STI), to increase the efficiency of drip irrigation systems. This method is specific to permanent tree crops where soil is not tilled or turned. The STI method consists of removing a soil core beneath the emitter and filling the void with coarse sand. The SWMS??2D model, implemented in a 3D axisymmetric form, was used to simulate infiltration, water redistribution, evaporation from the soil surface, and rise of water inside the sand tube. Model simulations were compared with laboratory measurements determined from a weighing lysimeter. The simulated values of water height inside the sand tube and temporal position of the wetting front in both lateral and upward directions closely matched the experimental measurements. The advancement of the wetting front in the downward direction and evaporation estimates was predicted with less accuracy. Experiments showed that relative to surface drip irrigation, the STI method reduced evaporation by approximately 26% over a 4-day period.     

Border Irrigation Field Experiment.?II: Salt Transport

This paper presents results from an experiment to measure the salt transport processes within a border-irrigated bay in northern Victoria, Australia, an area with shallow saline ground water and cracking soils. The overland flow and drainage salinity measurements showed that lateral surface washoff of salt from the soil surface was the main process of salt transport into surface water. Soil salinity measurements showed that, although salt was removed from the near-surface soil, there was negligible leaching downward through the profile. This was due to the near saturation of the soil, the presence of cracks that minimize the vertical leaching, as well as the lack of deep drainage of ground water. These findings highlight the importance of lateral washoff in the transfer of salt from irrigation bays, suggesting that reduction in irrigation event volumes is likely to reduce salt export and thus affect the sustainability of irrigation in this area.     

料仓清堵助流装置—空气炮的应用

料仓内物料起拱、堵塞是一较普遍存在的问题，采用空气炮破拱、清堵，改善料仓内物料的流动性是一种较理想的方法。本文介绍了国内外有关空气炮的开发研制和应用情况，以及空气炮的功能、特点和工作原理，给出了空气炮喷爆能量的计算方式，并对空气炮的选用方法及安装要点作了介绍，可供参考。     

轧钢高压水除鳞喷射阀启闭特性分析

轧钢高压水喷射除鳞对提高钢材轧制表面质量效果明显 ,除鳞喷射阀结构特殊 ,由气压驱动 ,其启闭特性与一般水阀不同。分析了其阀芯所受水压力 ,液流力及密封的摩擦力 ,从而给出了启闭喷射阀所需气压作用力的计算式 ,并以研制的喷射阀的实际数据作为例子计算了该阀的启闭特性 ,解决了阀门流量大 ,压力高启闭难的问题。     

济钢第三炼钢厂EH36高强度船板生产工艺研究与实践

通过对济钢第三炼钢厂采用KR铁水预脱硫处理、120 tBOF副枪终点控制及脱氧合金化、LF造白渣泡沫渣埋弧操作、VD真空脱气处理后喂硅钙线、CCM全程保护浇铸流程生产EH36厚规格(50 mm)高强度船板进行了系统分析和研究,确定了各工序关键参数和操作控制要点。