Improvement of Impeller Blade Structure for Gas Injection Refining under Mechanical Stirring简

Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central part of the impeller is disk- or plate-shaped, and the blades are fitted to the side of the disk or plate. In addition, a disk is put on the top side of the impeller blades. The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller. These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller. In addition, the sloped swept-back impeller requires less power consumption. The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidi- rectional impeller rotation and without installing baffles. The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath. Highly efficient gas injection refining can be established under the conditions of proper impeller size, larger nozzle immersion depth, larger eccen- tricity and rotation speed of the impeller. The sloped swept back blade impeller can decrease the power consumption and vet improve the bubble disintegration and wide dist~ersion in the bath.     

Improvement of Impeller Blade Structure for Gas Injection Refining under Mechanical Sirring

The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments.A sloped swept-back blade impeller is proposed for the purpose.The central part of the impeller is disk-or plate-shaped,and the blades are fitted to the side of the disk or plate.In addition,a disk is put on the top side of the impeller blades.The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller.These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller.In addition,the sloped swept-back impeller requires less power consumption.The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidirectional impeller rotation and without installing baffles.The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath.Highly efficient gas injection refining can be established under the conditions of proper impeller size,larger nozzle immersion depth,larger eccentricity and rotation speed of the impeller.The sloped swept-back blade impeller can decrease the power consumption and yet improve the bubble disintegration and wide dispersion in the bath.     

TRT透平机叶片断裂分析

对某厂2号TRT透平机一级动叶片中断裂叶片的化学成分、宏观断口以及金相组织进行了分析,结果表明,该叶片属于腐蚀疲劳断裂,其疲劳裂纹起源于叶片进气边边缘部位的腐蚀麻点处,腐蚀麻点是由于叶片与湿积灰中的腐蚀性介质Cl-,SO4-等发生反应造成的。     

叶片形状对涡轮桨搅拌槽内尾涡特性的影响

Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their relationship with turbulence properties in a stirred tank of 0.48 m diameter, agitated by four different disc turbines, including Rushton turbine, concaved blade disk turbine, half elliptical blade disk turbine, and parabofic blade diskturbine. Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail. The location, size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics. The larger curvature resulted in longer residence time of the vortex at the impeller tip, bigger distance between the upper and lower vortices and longer vortex life, also leads to smaller and stronger vortices. In addition, the turbulent kinetic energy and turbulent energy dissipation in the discharge flow were determined and discussed. High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them. Although restricted to single phase flow, the presented results are essential for reliable design and scale-up of stirred tank with disc turbines.     

Life assessment for creep and fatigue of steam turbine components

Improvement of life assessment technologies for power plant materials and components is important in order to meet demands for economy and reliability. As for steam turbines, blade root and disc joints are one of the critical parts in turbines that experience the most severe creep and fatigue damage under high temperature or corrosive environment. In these parts, the structural stress concentration areas are close to the contact planes of blades and rotors, and this produces a complicated stress-strain field. Therefore, life assessment technologies based on precise stress analysis methods and damage mechanisms are necessary to ensure the reliability and economy of steam turbines. In this paper, creep and fatigue tests results by using component specimens simulating blade and rotor joint portions are described. Damage mechanisms of joint portions were investigated based on the observations of the micro-crack initiation and growth behaviors. Life assessment methodologies for joint structures are also discussed, based on the micro-damage, micro-crack or micro-cavity, and nonlinear finite element analyses of component specimens.     

The Growth of Hematite Blades during the High Temperature Oxidation of Iron

Micron-size blades of hematite (α-Fe2O₃) are observed to grow out of the oxidized surface of iron at high temperatures. The characteristics of these blades are described in the literature. The blades are observed to be twinned such that the plane of the blade is parallel to the (01−11) twin plane (K ₁), the blade axis is [−2110], and the direction of shear (η₁) is [0−112]. In addition, there is a hollow tunnel up the axis of each blade. It is suggested that the blades grow by surface diffusion of iron cations from the underlying magnetite through the tunnels to the blade tips; some lateral growth occurs by diffusion of these cations in the twin planes. The tunnels eventually become blocked in mature blades, forming a string of elongated voids, and further growth ceases.     

Formation of Gradient Structures in the Zone of Joining a Deformable Nickel Alloy and a Single-Crystal Intermetallic Alloy during Thermodiffusion Pressure Welding and Subsequent Heat Treatment

The possibility of formation of a high-quality solid-phase joint of an Ni₃Al-based single-crystal intermetallic VKNA-25 blade alloy with a high-temperature deformable EP975 disk alloy by pressure welding is studied to create high-performance one-piece blisk unit for the next-generation aviation gas turbine engines and to decrease the unit mass. The influence of the conditions of thermodiffusion pressure welding under the hightemperature superplasticity of the disk alloy and the influence of heat treatment of welded joints on the gradient structures in the welded joint zone and the structure at the periphery of the welded samples are investigated.     

铜基预合金粉末制备金刚石锯片的性能研究

采用共沉淀法制备了不同铜铁配比（质量比:45:35、50:30、55:25）的铜基预合金粉末,利用真空热压法烧结得到含金刚石的铜基结合剂刀头,通过激光焊接的方法制备出铜基结合剂金刚石锯片,研究了铜基预合金粉末中铜铁含量（质量分数）对金刚石锯片性能的影响。利用扫描电子显微镜观察锯片断面的显微组织形貌,并测量不同铜铁含量锯片的硬度和磨损量。结果表明:在三种配比中,当铜和铁质量比为50:30时,铜基结合剂与金刚石间的结合最佳,锯片性能最好,硬度最高（HRB 118）,锯片的磨损量最少（1.16 g）。     

Strength of Glued-In Bolts after Full-Scale Loading

In 1993 after 9 years of use, one of the wooden blades of a windmill was struck by lightning. After demounting, the damaged blade was handed over to the Technical University of Denmark, Lyngby, for the investigation of potential fatigue damage. This paper presents an experimental determination of the residual strength of the glued-in bolts that served as the blade to rotor hub connection in the windmill. The load history of the bolts, the test method, the observed fracture modes, and the force displacement curves are presented along with the recorded residual strength of the bolts. The bolts with a length of 500 mm had a special hollow tapering giving them a higher load-bearing capacity than solid bolts of equal dimensions. An FEM analysis confirms the higher load-bearing capacity. The mean residual stength was found to be 362 kN with a standard deviation of 37 kN, which is 95% of the predicted strength based on short-term tests on similar bolts. At fracture, a displacement between 0.4 and 1.0 mm was observed. In the majority of failures, the bolts were pulled out like a cork from a bottle.     

Service failure of hot-stage turbine blades:

Surface-connected porosity in current military aircraft hot-stage turbine engine blades is associated with blade failure. Oxidation ratcheting is suggested as the failure mechanism. Sta- tistical comparison of new and used blade populations showed that for blades cast with an equiaxed structure, the porosity in new blades was associated with crack formation on the con- cave surface of the used blades. The pores did not tend to develop into cracks on the compressed (convex) surface of the blade. Insufficient suitable data on directionally solidified blades pre- vented similar statistical correlations. However, metallography of the directionally solidified blades showed that the in-service cracks were related to oxidation inside surface-connected pores and that the cracks were oriented in the same direction as the (axial) casting pores. Thus, the proposed failure mechanism through ratcheting is based on the following insights: (1) the blades are thermally cycled as a normal part of service; (2) the hot blades expand and the open pores are filled with oxide; (3) when the blade is cooled, thermal contraction of the metal is greater than the oxide, causing compressive stress and yield; and (4) thermal expansion of the blades opens the pores again, since yield relaxed compressive stress at low temperature. These insights were supported by metallographic and computer-simulation studies which showed that the pores grow 20 to 50 pct in width per 100 missions (about 90 hours of operation) for a military aircraft on a typical mission profile.     

Microstructure,creep properties,and rejuvenation of service-exposed alloy 713C turbine blades

A study was carried out on the microstructure and creep properties of aero engine first-stage turbine blades made from Alloy 713C nickel-base superalloy. Results are reported for new blades, blades in two service-exposed conditions, and service-exposed blades subjected to one of three rejuvenation treatments: a recoating heat treatment, a hot isostatic pressing (HIP) + recoating heat treatment, and a HIP + controlled cooling + recoating heat treatment. The blade microstructure undergoes significant change during service, and this leads to a loss in creep properties exhibited by specimens machined from the blade airfoils. Good correlations were observed between the rupture time and the amount of blade airfoil untwist and between the minimum creep rate and the amount of untwist. The recoating heat treatment and the HIP + controlled cooling + recoating treatment were moderately successful in restoring the microstructure and creep properties of the service-exposed blades. In comparison, the HIP + recoating treatment was very successful in rejuvenating creep properties but only for blades having a chemical composition with a lower propensity to form σ phase. For the blades with an unfavorable composition, σ phase was found to form preferentially near the grain boundaries during creep testing, and this had a detrimental effect on the creep properties. Nonetheless, the degree of rejuvenation for these blades was always at least as good as that obtained through the recoating heat treatment alone. Formerly National Aeronautical Establishment     

Failure Assessment of the First Stage Blade of a Gas Turbine Engine

The gas turbine engine under investigation in this paper was in service after major overhaul for about 2 h at 9:47 A.M. on 18 October, 2014. The 60 MW gas turbine engine experienced a forced break down because of extremely high vibrations and subsequent output power reduction. The blade was made of Inconel 738LC nickel-based super-alloy. Evaluation of the microstructures of the root and tip of the damaged blade, showed no significant change in the microstructure. In closer observation of the fractured blade, some points affected by impact of the remaining airfoil were observed. Metallurgical investigations of the damaged zones of the fractured blade showed many iron rich zones near the fractured surface. The morphology of the fractured surface showed a semi-brittle fracture due to the impact. Finally, it was concluded that the main reason for the gas turbine failure was domestic object damage due to the impact of the liberated components of the turbine engine on the blades.     

金刚石有序排列对锯片性能的影响

排布方式合理的有序排列金刚石锯片能明显提高锋利性,增加寿命。试验采用2片无序排列锯片和4片有序排列锯片切割混凝土,不同排布方式的锯片切割性能有很大的差异。介绍了有序排列锯片制作的工艺流程,并且从理论上分析了排布参数对切割性能的影响,提出横向间距和纵向间距是有序排列方式设计中最重要的两个参数。     

Experimental-calculation study of ion-plasma thermal barrier coatings for turbine blades made of intermetallic nickel superalloys

The ion-plasma thermal barrier coatings deposited onto samples and blades made of intermetallic VKNA-1V and VKNA-25 alloys are tested in a laboratory. The external ceramic layer of the thermal barrier coatings (TBC) is formed by magnetron sputtering of zirconium alloy targets and has a columnar structure. The influence of NiCrAlY(Re, Ta, Hf) + AlNiY(Hf) + ZrYGdO TBC on the long-term strength at a test temperature of 1200°C and on the high-cycle fatigue at a temperature of 900°C is studied. Blades with TBC are subjected to thermal cycling tests in the temperature range 950 ? 400°C and 1050 ? 400°C during air cooling and in the range 950 ? 200°C during water cooling at 500 cycles. The temperature fields in the cross section of a blade airfoil during thermal cycling are calculated. The laws of formation of fracture zones and the development of thermal fatigue cracks under the conditions that are close to the operating conditions of nozzle TBC-containing blades are investigated.     

Membrane fatty acid analysis of Antarctic bacteria

The removal of most ceramic brackets is accomplished by specially designed pliers that apply some form of tensile or shear force to the tooth surface. While the shear and tensile bond strengths for ceramic brackets in vitro have been reported, a simulation of the actual force application when using sharp-edged debonding pliers to debond a bracket has not. The purpose of this study is to determine the effectiveness and the force levels generated by the use of both the wide and the narrow blades in the debonding of ceramic brackets. The present findings indicate that the narrow blades effectively debonded ceramic brackets with a significantly lower mean debonding force (120 kg/cm2) than the wider blades (150 kg/cm2). The surface area of the blade in contact with the bracket-adhesive interface is less for the narrow blade (2.0 mm) than for the wide blade (3.2 mm). This relatively smaller contact area is sufficient to debond a bracket at a significantly lower debonding force.     

航空发动机叶片叶尖耐磨封严涂层技术及其发展

航空发动机封严涂层体系是控制其转子和静止件间隙的主要措施,其中叶片叶尖耐磨封严涂层可以使叶尖在与机匣或外环块封严结构或涂层刮擦时得到保护,并达到缝隙最小化的设计要求.本文综述了国内外叶片叶尖耐磨封严涂层的材料组成、制备工艺、应用及其优缺点,简述了国内耐磨封严涂层技术现状及发展要求,提出了针对新型高性能航空发动机的发展迫...     

抽拉速率对高温合金叶片定向凝固组织的影响

采用以液态金属锡作为冷却介质的定向凝固设备,研究了五种不同的抽拉速率对叶片定向结晶组织的影响。结果表明抽拉速率对高温合金叶片的定向结晶组织具有重要的影响,抽拉速率为6mm/min时,可保证叶片的良好成形,定向柱晶挺直,晶粒沿竖直方向排列整齐,晶粒大小均匀。抽拉速率增大,合金组织细化,枝晶间距变小。     

离心式高炉鼓风机扩压叶片断裂事故分析及处理

通过高炉鼓风机扩压叶片断裂事故，从化学分析、物理检验，结合使用情况对扩压叶片断裂原因进行了详细分析，并提出了改进措施。     

Optimization of Rotating Blades with Dynamic‐Behavior Constraints

The optimal design of rotating pretwisted blades subject to dynamic behavior constraints is studied. The restrictions on multiple blade natural frequencies and on maximum blade dynamic deflections are considered the dynamic behavior constraints. The aerodynamic forces acting on the rotating blades are simulated as harmonic excitations. Optimization techniques of the optimality‐criterion method and the method of modified feasible directions have been successfully developed and applied to minimize the weight of rotating pretwisted blades. Based on these techniques, the numerical results show that the effect of setting angle on the optimal design weight for the first frequency‐constraint case is more significant than that for the second frequency‐constraint case. It is also shown that the changes of pretwist angle will considerably affect the optimal design weight for the second frequency‐constraint case. However the effect is not significant for the fundamental frequency‐constraint case. The results also indicate that the increase of rotating speed will decrease the optimal design weight.     

三层桨搅拌槽内三维流场的数值模拟

采用计算流体动力学(CFD)的方法,对稀土萃取过程中上两层为平直叶、底层为涡轮桨叶的三层组合桨搅拌槽内三维流场进行了研究。利用标准的k-epsilon双方程模型对无机相(水)和有机相(P507)的混合液在搅拌槽中产生的流场进行数值计算,得到这种搅拌桨以恒定转速300r/min在搅拌槽内转动时产生的速度场和压力场,以及速度分布云图、速度矢量图以及压力云图,为搅拌桨的设计与改进提供理论基础。