整体叶盘叶型电解加工流场设计及实验简

 电解加工（ECM）是航空发动机整体叶盘制造的主要技术之一,其电解液流场稳定性是影响电解加工精度和表面质量的核心因素。本文在分析原有的二维流场基础上,针对流体在不同流道截面下的流场状态,提出了一种三维复合电解液流场模式,即三股电解液分别从毛坯进气边、叶盆叶根、叶背叶根流入,由排气边交汇流出。采用有限元法对三维复合流场及两类二维流场开展仿真分析,分析结果表明三维复合流场改善了流道突变区域流场状态,有效抑制了二维流场的流场缺陷,有助于提高流场稳定性。对加工区液体流态进行了判断,其结果显示三维复合流场可以满足电解加工要求。开展了3种流场模式的加工速度比较实验,三维复合流场达到的进给速度最高,较二维流场可显著提升加工效率。采用三维复合流场开展了多叶片扇段加工,获得了较好的重复精度与表面质量。     

基于电解扫掠成形原理的整体叶盘叶根加工方法

采用片状或管状阴极电解加工(ECM)后的整体叶盘由于加工运动、阴极形状等原因在叶根处会形成一定的加工残留,影响整体叶盘的加工精度。针对叶片电解加工后形成的叶根残留,开展去除叶根残留电解加工方法的研究,解决叶根电解加工的阴极结构、加工路径设计等难题。首先,分析了叶根的残留分布情况以及叶间通道的结构,采用了电解扫掠成形加工方案。其次,设计了阴极结构与加工路径,在阴极结构上采用了扇形流道并分析了电解液流速分布,通过增加引流槽、改变倾角等措施改善了流场;对阴极的运动路径进行了规划,利用专用仿真软件对阴极运动干涉与加工程序进行了检验;通过附加叶盘转动补偿了由于不同截面内叶间通道宽度与阴极刃口尺寸不一致给加工带来的不足。最后,制作了电解加工装置并通过试验对叶根电解加工方法进行了验证。试验结果表明,该加工方法有效去除了叶根残留,加工表面质量好,加工精度达到了要求。     

整体叶盘电解加工电解液进液角度优化研究

整体叶盘电解加工中,流场对加工稳定性起着重要作用,电解液进液角度对流场均匀性具有重要影响。针对由叶尖至叶根流动模式,设计了5种电解液进液角度流动模型（12°、22°、32°、42°以及52°）,并开展电解加工流场仿真研究。结果表明,电解液进液角度为32°时,平均流速为19.01 m/s,流速均方差为6.33,满足整体叶盘电解加工对流场的要求。在电解液进液角度为32°的流场形式下,开展整体叶盘电解加工试验,加工过程稳定,试件表面无流纹,加工精度为0.12 mm,表面粗糙度为Ra0.353μm,验证了流场的合理性。     

整体叶盘磨粒流加工仿真与试验研究

针对航空发动机扩压器整体叶盘内流道表面加工成本高和效率低的问题,提出采用磨粒流加工方法。通过建立有无上压盖及引流芯模的流道仿真模型,对比分析了两种模型下仿真流场的分布规律。在此基础上,对工件的夹具结构进行了改进并利用该夹具对扩压器整体叶盘内流道表面进行了磨粒流光整加工试验。结果表明:增加上压盖及引流芯模结构后,有效改善了整体叶盘大端和小端处的局部流场,解决了加工效果不一致和锐边被磨料冲蚀的问题,加工后流道表面粗糙度降低了0.6μm,表面质量得到了进一步提高。     

基于精密电解工艺的叶片进排气边形状控制方法

针对高温合金复杂曲面叶片进排气边尺寸和形状的高精度要求,开展了精密电解加工试验研究。结果表明,利用振动进给电解机床与优化电极设计方法可以有效提高电解加工叶片进排气边尺寸形状精度。使用电导率85~90m S/cm,温度25℃的Na NO3电解液,叶盆和叶背电极振幅0.4mm,振频40Hz可加工出中心型面进气边形状满足设计要求,排气边接近设计要求的试件。在此基础上,探索采用振动光饰工艺作为精密电解加工技术的辅助手段解决叶片进排气边形状控制难题的方法。     

脉动态电解加工

电解加工在航空航天装备的核心部件制造中起到了重要作用。为了满足这些高科技产品的发展需求,它的加工精度需要进一步提高。电解加工过程中产生的氢气、温升及去除物,会显著影响加工间隙中电解液电导率的分布,并降低加工精度。脉动态电解加工将工具振动与脉冲给电优化耦合,改变了间隙状态,提高了精度和稳定性。拷贝式、旋印式、削边电极线切割式等3种脉动态电解加工形式分别对应叶片类、机匣类、榫槽类结构的加工表现出很好的工艺效果。     

群孔管电极电解加工均流设计及其试验研究

 为提高群孔电解加工的稳定性和成形精度,对群孔管电极电解加工(ECD)的分流腔流场进行了建模分析。通过对分流腔进行数值求解,研究了分流腔电解液的分布规律,并分析得到了影响电解液分流均匀度的主?问?分流腔直径),进而对其进行了优化设计。基于该优化设计并结合试验得到了适合正流群孔电解加工的分流均匀度系数和相应的尺寸系数。采用优化的分流腔参数和加工参数进行试验,得到了尺寸精度较好的长排孔结构,孔间距5 mm,孔径为(1.03±0.03)mm,其加工过程稳定,无短路现象。通过优化分流腔结构可以提高其分流均匀度,从而使电解孔加工的稳定性显著增加,加工精度提高。     

应用数学成果——Ⅰ级涡轮叶片电解试验

一、试验目的过去,用电解加工的方法加工某机Ⅰ级涡轮叶片,只限叶盆加工余量为0.05毫米以上的,否则容易超差报废,而且叶背不能电解加工,只能机械抛光。对此,我们对原工艺装置进行了调整,改进了流场,取消了压背,优选了电解液,实现了叶盆、叶背同时进行电解加工。为了进一步提高叶片电解精度(即整平比),并找出影响叶片电解加工质量的主要因素,提高生产效率,故对电解加工有关参数运     

微幅往复走丝微细电解线切割试验研究

 微细电解线切割是一种新型的微细加工技术,适合高精度金属窄缝、窄槽等微细结构的加工,由于加工间隙内电解产物排出困难,容易影响加工精度。为了提高产物排出效率,提出线电极微幅往复走丝促进加工间隙内电解产物排出的方法,改善了加工稳定性,提高了加工精度和加工效率。建立了间隙内电解产物排出效率对加工精度、加工速度影响的数学模型,分析了线电极走丝速度和走丝幅值对间隙内电解产物排出和电解液更新的影响。通过试验研究了线电极的走丝速度和走丝幅值对加工精度和加工效率的影响规律,采用优化参数在厚度为80 μm的钴基弹性合金上进行微槽结构加工,底面粗糙度约为0.45 μm,倒角半径小于8 μm。结果表明线电极轴向微幅往复走丝可以有效地提高加工质量和加工效率。     

添加络合剂电解加工小孔的实验研究

本文通过向电解液中加入络合剂与常规电解加工进行了侧面间隙、加工效率的对比实验,对添加络合剂的加工机理以及实验结果进一步分析。实验分析表明,和常规电解加工小孔相比,添加络合剂使得加工间隙内气、液、固三相流场更趋于气、液两相流场,改善了流场分布的均匀性,从而使得加工过程中侧面间隙变小,加工精度和加工效率得到提高。     

Flow field design and experimental investigation of electrochemical machining on blisk

Flow field is a crucial factor to influence the stability and surface quality in the electrochemical machining (ECM) of blisks. A four-way flow mode was proposed to eliminate mixing regions of electrolyte at the leading and tailing edges. Two flow field models were described separately in this report: a W-shaped flow mode and a four-way flow mode. The flow field was analyzed through a finite element method. The results showed that, in comparison with the W-shaped flow mode, the distribution of electrolyte flow was more uniformed and the mixed region in the flow channel was improved. The pressure of the leading and tailing edges inlets was optimized, and optimal pressure of 0.6 MPa was determined. In addition, verification experiments were performed, and the results showed that the stability, efficiency, and quality of the profiles of the blisk blade manufactured by ECM were enhanced in the new flow mode.     

Simulation and experimental investigation on a dynamic lateral flow mode in trepanning electrochemical machining

An appropriate flow mode of electrolyte has a positive effect on process efficiency, surface roughness, and machining accuracy in the electrochemical machining(ECM) process. In this study, a new dynamic lateral flow mode, in which the electrolyte flows from the leading edge to the trailing edge, was proposed in trepanning ECM of a diffuser. Then a numerical model of the channel was set up and simulated by using computational fluid dynamics software. The result showed that the distribution of the flow field was comparatively uniform in the inter-electrode gap. Furthermore, a fixture was designed to realize this new flow mode and then corresponding experiments were carried out. The experimental results illustrated that the feeding rate of the cathode reached 2 mm/min, the best taper angle was about 0.4°, and the best surface roughness was up to Ra= 0.115 lm. It reflects that this flow mode is suitable and effective, and can also be applied to machining other complex structures in trepanning ECM.     

Electrochemical trepanning with uniform electrolyte flow around the entire blade profile

In the traditional machining process for diffusers, blades are easily deformed, and methods suffer from high tool wear and low efficiency. Electrochemical machining(ECM) possesses unique advantages when applied to these difficult-to-machine materials. In the ECM process, theflow field plays a crucial role. Here, an electrolyte flow mode that supplies uniform flow around the entire blade profile was adopted for electrochemical trepanning of diffusers. Various flow rates were employed to obtain the optimal flow field. Simulations were conducted using ANSYS software, and results indicated that increasing the flow rate substantially afforded a more uniform flowfield. A series of experiments was then performed, and results revealed that increasing the flow rate greatly improved both the machining efficiency and the surface quality of the diffusers. The maximum feeding rate of the cathode reached 4 mm/min, the blade taper of the concave part decreased to 0.02, and the blade roughness was reduced to 1.216 lm. The results of this study demonstrated the high feasibility of this method and its potential for machining other complex components for engineering applications.     

Optimization of flow field in electrochemical trepanning of integral cascades (Ti6Al4V)

Ti6Al4V is widely applied in the integral cascades of aero engines. As an effective machining method, electrochemical trepanning (ECTr) has unique advantages in processing surface parts made of hard-to-cut materials. In ECTr, the state of the flow field has a significant effect on processing stability and machining quality. To improve the uniformity of the flow field when ECTr is applied to Ti6Al4V, two different flow modes are designed, namely full-profile electrolyte supply (FPES) and edges electrolyte supply (EES). Different from the traditional forward flow mode, the flow directions of the electrolyte in the proposed modes are controlled by inlet channels. Simulations show that the flow field under EES is more uniform than that under FPES. To further enhance the uniformity of the flow field, the structure of EES is optimized by modifying the insulating sleeve. In the optimized configuration, the longitudinal distance between the center of the inlet hole and the center of the blade is 6.0 mm, the lateral distance between the centers of the inlet holes on both sides is 16.5 mm, the length to which the electrolyte enters the machining area is 1.5 mm, and the height of the insulating sleeve is 13.5 mm. A series of ECTr experiments are performed under the two flow modes. Compared with EES, the blade machined by FPES is less accurate and has poorer surface quality, with a surface roughness (R_a) of 3.346 μm. Under the optimized EES, the machining quality is effectively enhanced, with the surface quality improved from R_a = 2.621 μm to R_a = 1.815 μm, thus confirming the efficacy of the proposed methods.     

薄型中空电极振动电解切割TB6钛合金

TB6钛合金由于具有优越的性能,广泛地用于航空航天领域。然而从大余量的TB6钛合金锻铸件毛坯加工成复杂结构的零件,其加工效率低,刀具和机床成本高,造成了极大的浪费。为解决这一问题,提出了一种利用薄型中空电极进行快速大余量去除的电解加工(ECM)方法,即将零件与多余材料切割分离,有望较大程度提高加工效率,降低加工成本。为改善电解加工流场特性,提高加工精度,对电极施加振动,并对薄型中空电极的振动切割进行了建模分析和试验研究。试验结果表明,合适的振动幅值和频率(A=0.05mm,f=50Hz)可以使得各处电解液电导率趋于一致,从而提高加工的精度、稳定性和效率。复杂结构件的成功切割证明了薄型中空电极振动电解切割加工技术具有一定的适用性。     

Design and optimization of electrolyte flow fields in electrochemical machining of cross-channel array with tool vibration

A metallic interconnect plate with a flow channel array is one of the most important elements in a solid oxide fuel cell(SOFC). Electrochemical machining(ECM) is considered to be an adoptable technology for fabricating flow channels in an interconnect plate on account of its efficiency and low cost. With respect to the traditional electrolyte flow mode in ECM cross-channel array, the electrolyte usually flows from one side to the opposite side of the rectangular processing area. However, obvious...     

航空发动机整体叶盘磨料水射流开坯加工技术研究进展

整体叶盘结构是航空发动机技术发展的一个重要方向，且多采用难加工材料，如何实现整体叶盘高质高效加工是机械制造领域亟待解决的难题之一。通过高压磨料水射流（AWJ）加工技术实现整体叶盘毛坯的开坯粗加工，是一种有效缩短整体叶盘加工周期、降低昂贵铣削刀具成本、提高开坯效率的工艺手段。本文就磨料水射流加工材料去除机理、复杂曲面轨迹优化、多物理量和机械量参数组合优化和整体叶盘开坯设备概述了国内外的研究现状，在此基础上，针对当前具有复杂曲面结构的整体叶盘开坯面临的关键问题，提出了若干解决思路和技术途径，指出了高压磨料水射流在复杂曲面零件高效加工中的发展趋势。     

Improving profile accuracy and surface quality of blisk by electrochemical machining with a micro inter-electrode gap

Electrochemical machining (ECM) has emerged as an important option for manufacturing the blisk. The inter-electrode gap (IEG) distribution is an essential parameter for the blisk precise shaping process in ECM, as it affects the process stability, profile accuracy and surface quality. Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk. To achieve micro-IEG (<50 μm) blisk finishing machining, this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration. The modelling and simulation of the blisk micro-IEG machining have been carried out. Exploratory experiments of variable-parameters blisk ECM were carried out. The results illustrated that the IEG width reduced with the progress of variable parameter process. The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 μm and 21 μm, respectively. The profile deviation for the blade’s concave surface and convex surface are 49 μm and 35 μm, while the surface roughness reaches R_a = 0.149 μm and R_a = 0.196 μm, respectively. The profile accuracy of the blisk leading/trailing edges was limited to within 91 μm. Compared with the currently-established process, the profile accuracy of the blade’s concave and convex profiles was improved by 50.5 % and 53.3 %, respectively. The surface quality was improved by 53.2 % and 50.9 %, respectively. Additionally, the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution. Some electrolytic products were dispersed on the machined surface, and their components were mainly composed of the carbide and oxide products of Ti and Nb elements. The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM, which can be used in engineering practice.