离心压缩机叶轮材料FV520B冲蚀规律和机理的研究

利用高速冲蚀试验系统,以7 μm、10 μm、14 μm多角氧化铝微粒为冲蚀颗粒,在120 ~ 210 m/s冲击速度范围内,对离心式压缩机叶轮材料FV520B在模拟压缩机叶轮高速粒子冲蚀环境下的冲蚀规律进行了系统的试验研究。对冲蚀表面形貌进行分析,研究冲蚀磨损机理。结果表明：参与冲蚀的粒子质量在5 ~ 80 g之间时,冲蚀率先增加后减小即为冲蚀过渡期,冲蚀粒子质量大于80 g后冲蚀率趋于平稳,进入冲蚀稳定期;高、低强度的两种FV520B材料,均呈现出典型的塑性材料的冲蚀特性,最大冲蚀率分别出现在24°、18°的冲击角度附近;高强度FV520B在24°和90°冲击角度时的速度指数分别为3.37和3.68,速度指数随冲击角度的增大而增大;FV520B冲蚀磨损的实质是微切削与变形磨损共同作用,在低角度冲蚀时,以微切削磨损为主,而在大于60°的高角度冲蚀,以变形磨损为主。     

离心压缩机内固粒运动规律与冲蚀磨损的数值模拟

针对离心压缩机叶轮的冲蚀磨损问题,利用FLUENT中离散相模型、质量冲蚀率模型,对压缩机内部不同粒径的固体颗粒的运行轨迹、运动速度、偏聚浓度及造成的叶片冲蚀率的分布进行了数值模拟。结果表明:粒径为5~20μm的绝大部分的固体颗粒流经大叶片压力面附近流道;固体颗粒在运动到叶片前缘过程中速度迅速升高,在压力面腹侧会有所减小,后缘处重新升高;大叶片后缘根部固体颗粒浓度高、运行速度快,冲蚀磨损严重,且固体颗粒直径越大对大叶片压力面造成的冲蚀磨损越严重。     

压气机流道中砂粒轨迹及碰撞位置的计算方法研究

飞机在砂尘地带工作时会吸入大量砂粒,砂粒进入核心机后会对叶片造成永久性的磨损,改变发动机的总体性能,对发动机造成极大损伤。通过建立碰撞反弹数据库,采用颗粒轨道模型,并调用已存入数据库中的气动参数,对砂粒在叶片通道中的飞行过程进行数值模拟,获得了砂粒在压气机流道中的运动轨迹及碰撞位置,为掌握影响砂粒在压气机内部的运动轨迹及其碰撞点位置提供研究方法,同时也为今后提高压气机叶片相应部位强度的研究提供理论依据。     

SiC粒径对铜基复合材料载流磨损性能影响

采用粉末冶金法制备不同SiC粒径改性的SiC/C/Cu复合材料,研究SiC颗粒大小对材料组织结构和物理性能的影响;在载流摩擦磨损试验机上进行载流磨损试验,研究不同滑动速度下,SiC粒径对材料磨损率的影响。结果表明：在SiC/C/Cu复合材料中小颗粒SiC偏聚于C/Cu界面处,而大颗粒SiC均卡嵌在铜基体内,并且随着SiC颗粒的增大,复合材料硬度和密度稍有增加,孔隙率迅速降低,导电率增加;在较低滑动速度下,复合材料的磨损量随SiC粒径增大不断降低;在较高滑动速度下,随SiC粒径增大,复合材料的磨损率先降低后升高,25 μm SiC改性的复合材料具有最低的磨损率。     

固体颗粒对水力旋流器冲蚀磨损特性的影响

针对工业污水处理系统中水力旋流器壁面的冲蚀磨损问题,采用FLUENT软件中RSM模型和DPM模型模拟水力旋流器内液、固两相流的流动情况,并以Grant和Tabakoff碰撞模型求解器壁冲蚀磨损速率。研究了不同颗粒流速、粒径和质量流量条件下器壁冲蚀磨损规律以及最大冲蚀磨损位置。结果表明:旋流器壁面最大冲蚀磨损率随着颗粒流速的增大而呈指数递增,与质量流量呈正相关关系,但与颗粒粒径呈不完全线性增长关系;旋流器壁面冲蚀磨损率随着颗粒流速、粒径和质量流量的改变而不同,其中颗粒流速变化的影响最大、质量流量次之、粒径的影响最小;固体颗粒碰撞和磨削旋流器壁面而引起局部磨损,并且影响最大冲蚀磨损区域的出现位置。     

汽轮机部件渗硼层耐固体颗粒冲蚀性能研究

为研究不同状态下固体颗粒对渗硼层性能的影响,改善汽轮机部件耐固体颗粒的冲蚀性能,采用固体渗硼技术制备渗硼层,研究了不同温度、颗粒速度、冲击角度下渗硼层的磨损率,分析温度、固体颗粒速度、粒子冲击角度对渗硼层抗冲蚀性能的影响.结果表明渗硼层在高温状态下均呈现出脆性材料的抗固体颗粒冲蚀特性,磨损率随冲击角度的增大而增大.对于高参数汽轮机喷嘴压力面常见的粒子小角度冲蚀时,渗硼涂层可以使叶片抗磨损能力提高30～60倍,在大冲蚀角度下其抗冲蚀能力也能提高3～6倍.     

汽轮机再热后级内颗粒冲蚀特性

汽轮机再热后级内叶片受到固体颗粒冲蚀,严重影响着汽轮机的安全经济运行。以某超临界汽轮机再热后第1+1/2级(第一级与相邻级的喷嘴)扭叶片为研究对象,通过拉格朗日法模拟不同粒径颗粒三维运动轨迹,并采用Finnie冲蚀模型,研究不同动静轴向间隙及不同负荷下颗粒对叶片的冲蚀特性。结果表明,由于动叶高速旋转,颗粒撞击到动叶时会获得与主流方向相反的速度,进而又反弹回静叶。较大粒径颗粒在动静叶片轴向间隙内"反复反弹"是造成再热后级内冲蚀的主要原因。适当增大动静轴向间隙可以有效地减少反弹回静叶的颗粒数量。当动静轴向间隙为5 mm时,反弹回静叶的颗粒为10%,轴向间隙增大为8 mm时,没有颗粒反弹回静叶。当机组负荷降低时,固体颗粒撞击叶片后的反弹角增大、反弹回静叶的数量增多,颗粒在动叶和下级静叶轴向间隙内反弹后,只有极少颗粒能够流出下级静叶。     

爆炸喷涂CrC涂层耐固体粒子侵蚀性能研究

为研究不同状态下固体颗粒对爆炸喷涂CrC涂层性能的影响,改善产品耐固体颗粒的冲中蚀性能,采用爆炸喷涂技术制备涂层,研究了不同温度、颗粒速度、冲击角度下涂层的磨损率,分析温度、固体颗粒速度、粒子冲击角度对涂层抗冲蚀性能的影响.结果表明：爆炸喷涂CrC涂层在不同温度和速度下磨损率都表现出随角度的增大而增加的趋势,在90＆#176;时达到最大,表现为典型脆性材料的磨损特性.     

一种多层结构在冲蚀磨损中的数值研究

本文设计了一种针对冲蚀磨损的解决方案。利用多层材料的不同性能,达到减少冲蚀磨损的效果,这种结构具有一定的主动减摩性能。在不同的冲蚀条件下进行了仿真模拟,主要针对不同冲蚀速度进行研究,并且获得了较好的冲蚀磨损率。对于数值模拟,在计算流体动力学框架内采用了离散经验模型和用于材料侵蚀的Oka模型,仿真研究表明,这种多层材料在冲蚀速率100m/s以内的磨损率最多可以达到1.2×10-5kg/m2·s-1,具有良好的抗冲蚀磨损特性。     

燃气轮机高压涡轮叶片粒子磨损数值模拟

为研究颗粒粒径对燃气轮机高压涡轮叶片磨损程度的影响,运用CFX-TASCflow软件对粒子轨迹和磨损区域进行DPM(Discrete Phase Model)数值模拟,采用拉格朗日法对流场中大量粒子轨迹进行追踪,使用不同浓度的机场跑道粒子(粒径10~1 500μm)对叶片进行磨损仿真预测,利用CFD-Post提取磨损数据和图像。研究表明:直径为10~80μm的微粒倾向于跟随气流运动,对叶片造成轻微磨损;直径大于100μm的粗粒轨迹明显偏离气流路径,对叶片造成多次严重损伤;随着机场跑道粒子质量浓度的增加,叶片磨损质量线性增加,粒子质量浓度为600 mg/m3时叶片前缘与叶盆后部损伤最为严重,与文献实验结果吻合。通过一系列实验表明粒子平均磨损率为2.6 mg/g。     

Elevated Temperature Evaluation of Fretting and Metal Transfer between Coated Titanium Components

During fretting, small amplitude displacements and high normal surface loads combined with abrasive oxide particles cause surface damage that acts as initiation sites for fatigue cracks. Since these conditions are prevalent within the titanium dovetail joints of jet engines a wear mode analysis was performed on extended service jet engine disks and compressor blades. The results of the wear mode analysis indicated that titanium from the uncoated disk was transferred to the softer copper-nickel-indium coated dovetail surface of the blades. This transfer created titanium on titanium contact and eventually fretting wear. In order to simulate these conditions, a moderate displacement (125 μm), low cycle phase followed by a small displacement (25 μm), high cycle fretting phase utilizing a cylinder on flat configuration was developed. The analysis and test procedure developed during this study will ultimately aid in the selection and evaluation of a new coating capable of preventing fretting.     

静叶尾迹对压气机动叶非定常气动载荷的影响

以某型航空发动机压气机转子系统为研究对象,建立了单级叶盘的三维结构及流场模型。通过对滑移网格(sliding mesh,简称SM)方法与运动坐标系(moving reference frame,简称MRF)方法在计算耗时和收敛性方面的比较,证明了运动坐标系方法的准确性和高效性。考虑前一级静叶尾迹的影响,求解压气机内部在不同时刻的流动特性,得到静叶尾迹对动叶流场的非定常干扰情况。经过对压气机叶顶和轮毂、动叶压力面和吸力面非定常气动载荷的分析发现:在动叶流场的前缘形成了较主流区压力和速度较低的不均匀流场,且在动叶前缘叶顶位置受到的气动载荷最为显著;动叶压力面和吸力面气动载荷的分布规律相反,从叶顶至轮毂、前缘至尾缘,压力面非定常气动载荷的大小和波动幅度逐步递减,而吸力面却与其相反,呈现出逐步递增的趋势。该研究为某型航空发动机压气机叶盘转子系统的动力学设计提供了理论依据。     

Slurry erosion of polyphenylene sulfide-glass fiber composites

The erosive wear of glass-fiber-reinforced polyphenylene sulfide in a sand slurry has been investigated as a function of sand particle velocity and sand particle size. The morphology of slurry erosion failure has been examined by scanning electron microscopy and a possible equation for slurry erosion has been derived.     

Some Views on the Mapping of Erosion of Coated Composites In Tidal Turbine Simulated Conditions

This article presents a study of the erosion resistance of coated and uncoated polymer matrix composites for tidal turbine conditions. It focuses on the development of comparative erosive wear mode and mechanism maps for such materials. In our earlier work, testing of glass-fiber-reinforced polymer composites for tribological applications in marine simulated conditions, several erosion-related issues were highlighted. The combined effects of the NaCl solution and sand dramatically enhanced the erosive wear of the uncoated specimens. In order to address those issues, an erosion-resistant polymeric coating was applied to the composite and tested in marine simulated conditions with an extended range of sand particle size. The test results of the uncoated and coated composite have been compared in this research by erosive wear mode and mechanism maps techniques. These maps reveal that the coating has enhanced the erosion resistance. These findings provide significant progress toward materials selection approaches to manufacture of tidal turbine blades.     

Gas–Solid Erosive Wear of Biomimetic Pattern Surface Inspired from Plant

Gas–solid erosive wear is a phenomenon in which serious mechanical damage is caused by the impact of solid particles on a wall. In this study, we investigated the erosive wear characteristics and mechanism of biomimetic groove surfaces in gas–solid erosive wear. Orthogonal experimental results showed that the order of the factors that influenced the erosive wear of the biomimetic groove surface was morphology > space > feature size. The V-shaped groove surface exhibited the best erosive wear resistance over the smooth, square, and U-shaped groove surfaces. The surface microstrain calculated by X-ray diffraction lines was used to study the mechanism of erosive wear resistance enhancement of the biomimetic surface. The microstructure of the eroded surface was analyzed by scanning electron microscopy. The appearance of ribs on the biomimetic groove surface increased the erosive wear of the surface in a distal position with respect to the ribs themselves. This article shows more opportunities for bionic application in improving the anti-erosion performance of moving parts that work under dirt and sand particle environments.     

Design of a slurry erosion test rig

The design of a jet impingement slurry erosion test rig, built for laboratory use, is presented. This apparatus gives good control over many of the important test parameters, such as impact velocity, solid particle concentration and impact angle. An ejector nozzle is employed to entrain sand particles from a sand bed into a stream of water to form a slurry; after impingement, the abrasive particles and the water phase are separated and recycled. This makes the rig simple, economical and easy to operate and its pump and pipeline remain free from erosive wear. Experimental results are presented to illustrate the operation and performance of the rig.     

Dynamic test and fatigue life evaluation of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. To verify the reliability of the high cycle fatigue fracture of the 5 MW gas turbine engine blade being developed by Doosan Heavy Industries & Construction Co., Ltd., dynamic tests were conducted using real size compressor rigs according to previous studies. The dynamic safety margin of the 5MW gas turbine engine blade was calculated on the basis of the ratio between the dynamic stress and endurance limit stress respectively determined through the compressor rig and fatigue tests. The HCF characteristics and the fatigue life stability of the DGT-5 compressor blades were verified through these processes. A fatigue life design procedure for the gas turbine compressor blade was established on the basis of the design, analysis, and test processes implemented in a previous study. In sum, the 5 MW class gas turbine compressor blades were found to be well designed in terms of resonance stability and fatigue life.     

Design optimization of axial flow compressor blades with three-dimensional Navier-Stokes solver

Numerical optimization techniques combined with a three-dimensional thin-layer NavierStokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow, Governing differential equations are discretized using an explicit finite difference method and solved by a multi-stage Runge-Kutta scheme. Baldwin-Lomax model is chosen to describe turbulence. A spatially-varying time-step and an implicit residual smoothing are used to accelerate convergence. A steady mixing approach is used to pass information between stator and rotor blades. For numerical optimization, searching direction is found by the steepest decent and conjugate direction methods, and the golden section method is used to determine optimum moving distance along the searching direction. The object of present optimization is to maximize efficiency. An optimum stacking line is found to design a custom-tailored 3-dimensional blade for maximum efficiency with the other parameters fixed.