高温镍基合金涡轮叶片气膜冷却孔电解加工基础试验研究

以探究工艺参数对冷却孔的加工精度和加工效率的影响为主要目的,以高温镍基合金Inconel718为基材进行电解加工气膜冷却孔的基础试验研究。首先利用正交试验初步优化了管电极电解加工冷却孔的参数,其次通过单因素试验进一步研究了电解液入口压力P、加工电压U和电极进给速度f等关键加工参数对加工精度及加工蚀除率的影响,最终确定了最优加工参数组合。试验结果表明:电极进给速度对单边间隙的影响最大,电解液入口压力对单边间隙的影响最小;加工电压对材料蚀除率的影响最大,进给速度对材料蚀除率的影响最小。试验获得的最佳加工参数为:电解液入口压力为0.4 MPa,加工电压为9 V,电极进给速度为0.42 mm/min,在此参数组合下加工出冷却孔的加工精度和加工效率为最优。     

涡轮叶片冷却孔电解加工电解液流场CFD分析研究

以航空发动机涡轮叶片常用材料高温镍基合金Inconel718为基材进行气膜冷却孔电解加工试验,通过30组对比试验,以短路次数和单边间隙△_s作为性能评价指标,探讨了加工电压U和电解液浓度ζ对冷却孔加工效率和加工精度的影响规律。基于CFD软件,进一步着重研究了电解液速度及涡流等因素对冷却孔加工的影响规律。CFD分析得出:随着电解液浓度的升高,速度场分布均匀,涡流变化梯度增大,加工稳定性提高,加工精度降低;随着电压的升高,冷却孔锥度变大,加工精度较低,涡流变化较小,当电压较大时,较多气体析出,导致速度场分布不均匀且不连续,加工稳定性变差。     

发动机冷却孔电解加工机床研制及试验研究

航空发动机气膜冷却孔的加工是目前航空工业中亟需解决的主要问题之一,在分析对比了各种航空发动机气膜冷却孔的加工方法优缺点的前提下,利用电解加工的优点,设计研制了一台航空发动机气膜冷却孔电解加工机床,机床主要由循环系统,进给系统,控制系统和监测系统等四部分组成,可以很好地解决航空发动机在高强度高硬度材料上具有一定倾斜角的冷却孔难加工的问题,并以某航空发动机涡轮叶片气膜冷却孔的加工为例,以镍基高温合金Inconel718为材料,对该机床结构设计的合理性和加工稳定性加以验证。     

酒石酸钠对叶片冷却孔电解加工的影响研究

以航空发动机涡轮叶片常用材料Inconel718高温镍基合金为基材进行气膜冷却孔电解加工试验。基于自行研制的数控电解加工机床系统,通过30组对比试验,分析了在不同浓度硝酸钠电解液中添加2%浓度的酒石酸钠添加剂后对冷却孔加工过程稳定性及加工精度的影响规律。试验结果表明:硝酸钠电解液添加2%浓度的酒石酸钠后,电解加工区域的固态电解产物和加工过程的短路次数明显减少,加工稳定性得到很大改善,同时所加工冷却孔的单边侧面间隙有所减小,酒石酸钠的加入对提高冷却孔加工过程的稳定性有明确而积极的意义,对提高其加工精度也有一定的作用。     

排尘孔涡轮冷却叶片叶顶流动与传热研究

涡轮叶片叶顶排尘孔用于清除冷气中掺杂的尘粒,以保证气膜孔和冲击孔的可靠工作,但排尘孔射流引起叶顶流动和传热问题。采用参数化方法建立有、无排尘孔涡轮冷却叶片几何模型,基于包含叶片主体、主燃气通道和三腔回流式内冷却通道的全局模型,采用流热耦合数值分析,开展排尘孔对涡轮冷却叶片叶顶流动与传热问题的初步研究。研究结果表明,对比有、无排尘孔叶片,排尘孔射流可降低叶顶平均温度约25 K;冷却通道对流换热作用和叶顶排尘孔射流可使叶顶平面降温400～600 K,冷却效果与冷却通道冷气流量和尘孔结构在叶顶位置相关;排尘孔叶顶射流对叶顶间隙高温燃气泄漏具有阻碍作用,可以提高叶片总压恢复系数约0.5%～1.5%,随着冷气流量的增大,这种作用增强;尘孔结构设计应兼顾射流对叶顶流动与传热的共同影响。     

涡轮机叶片固定螺杆的加工尺寸分析

涡轮机的各级叶片是由叶片和固定螺杆共同完成一级整圈叶片的锁紧,文中对叶片固定螺杆孔加工时涉及到的A G、A G A和A LF定位参数进行有限元分析,计算螺杆与叶根的应力情况,最后进行比较,选择较为合适的固定螺杆孔加工参数。     

复杂结构单晶涡轮叶片气膜孔制孔质量控制及改进研究

现代高性能发动机涡轮前温度高,涡轮叶片采用在单晶高温材料基础上设计多腔内冷结构,叶身表面排布呈众多空间分布的气膜孔。气膜孔加工是叶片制造的关键环节,对叶片的冷却效果和工作可靠性有直接影响。本文针对某高压涡轮转子叶片,基于某批次叶片的高周疲劳试验结果,对其进行了打孔质量分析,并对打孔质量的控制和改进方法进行了研究,研究表明通过过程控制可以有效避免孔相交,满足疲劳寿命要求。     

玻璃孔加工的试验研究

研究了电镀金刚石工具结构和加工参数对玻璃孔加工质量和加工效率的影响。试验结果表明，在电镀金刚石工具端部开槽，可获得小的玻璃爆边直径和高的材料去除率。冷却方式影响玻璃孔的加工质量，主轴转速和配重载荷影响玻璃孔的加工效率。     

发动机缸盖加工关键工艺研究

汽车机缸盖是发动机上的关键部件之一,其加工精度的好坏将直接影响发动机的整体性能.提高气门座圈和导管孔的加工精度不但能延长发动机的使用寿命,而且能够降低发动机的油耗.针对发动机缸盖上关键特征气门座圈和导管孔的加工,对发动机缸盖气门座圈和导管孔加工工艺的发展、加工过程中常用的加工刀具、加工过程中常用的冷却方式、切削参数的选择和主轴的刚性对特征加工精度影响这五个主要因素进行了研究和分析,并给出了提高气门座圈和导管孔的加工精度的建议.     

末端执行器制孔精度试验研究

对末端执行器制孔孔径和孔距误差进行了试验研究,采用正交试验的方法对影响制孔精度的因素加以分析,得到了主轴转速、进给量、冷却方式、刀具参数对制孔精度的影响规律,为自动化钻孔工艺参数选择提供参考依据.     

Analysis of contoured holes produced using STED process

Recent developments in air engines call for more efficient means of turbine blade cooling to have higher power generation for the same unit size with increased inlet air temperature. To allow the turbine to operate at higher temperature, thousands of cooling holes are drilled in turbine blades. In order to increase heat transfer in cooling holes, the present design demands the wall of the cooling passage should be provided with contoured ribs. These irregularities help in inducing turbulence in the flow of cooling air, thereby increasing the rate of heat transfer. For drilling these kinds of contoured deep holes in a turbine blade made of material such as Inconel, the conventional drilling techniques are not suitable. The shaped tube electrolytic drilling (STED) is used to perform the task of drilling contoured holes in difficult-to-machine materials. In the present case, contoured holes are drilled by using two distinct feed rates f ₁ and f ₂ alternately (f ₁ > f ₂) and two types of workpiece materials, namely stainless steel and Inconel superalloy. Experimentally obtained profiles are compared with the profiles derived theoretically from the basic electrochemical machining equations. Quality performance factor is evaluated for the machined holes to find the best hole profile. From the present study, it has been observed that by varying the process parameters (viz., voltage (V), faster feed rate (f ₁), and slower feed rate (f ₂)) during drilling and fixing different step lengths, various types of hole profiles can be generated using STED process.     

旋转超声电解复合加工小孔的仿真加工

为研究旋转超声电解复合加工小孔的成型过程,进行了旋转超声电解复合加工小孔试验,得到了不同加工时间孔的截面,并根据试验参数,进行了基于ANSYS的二维仿真加工和三维仿真加工。对小孔的入口直径、底面直径和加工深度进行了对比分析,结果表明由于三维仿真加工中采用了管电极,并考虑了电解加工中阴极超声高频振动对电解液电导率的影响,故其仿真结果更加接近试验值,间接证明了旋转超声电解复合加工小孔三维仿真加工的可靠性,展示了不同时刻的三维加工型腔,为旋转超声电解复合加工的成型过程和成型规律的研究提供了参考。     

Research on ECM process of micro holes with internal features

Micro holes with internal features are widely used as spray holes and cooling holes nowadays, which are usually required to be with high aspect ratio and shape accuracy, as well as good surface quality. An electrochemical machining (ECM) process is presented to machine these micro holes with diameter <200 μm. A quantitative relation between micro-hole diameter and machining parameters including voltage, duty ratio and feedrate is obtained through orthogonal experiments. According to the designed shape of internal features, change rules of machining parameters for varied diameters in different depth are obtained, and then micro holes with internal features are shaped precisely. Taking reverse tapered hole as an example, ECM experiments by varying parameters of voltage, duty ratio and feedrate (called varying voltage machining, varying duty ratio machining and varying feedrate machining, respectively) are carried out. Micro holes with inlet diameter of 178 μm and taper angle of 1.05° are shaped on a 1.0 mm-thick workpiece of 18CrNi8. The deviation of inlet is <3 μm and the taper-angle error is <0.1° in varying voltage machining. The corresponding dimensional accuracy of taper angle is improved by 51% than that of varying duty ratio machining under the same efficiency. The machining efficiency of varying voltage machining is increased by 36% compared to the efficiency in varying feedrate machining. In addition, the micro holes with complex features of funnel shape and bamboo shape are machined.     

Experimental investigation and simulation of heat flux into metallic surfaces due to single discharges in micro-electrochemical arc machining (micro-ECAM)

In this work, single discharges of electrochemical arc machining are examined. The heat-affected zone is analyzed, and a model is set up to simulate the heat transfer into the workpiece. As an input parameter of the simulation, the temperature of the electrochemical arc machining process was determined to be 3,500 K by means of emission spectroscopy. The simulation shows that the diameter of the heat-affected zone is less dependent on discharge duration and heat transfer due to heat flux than on the arc spot diameter. As a result of the investigation, it became clear that varying diameters of the heat-affected zone have to evolve from different diameters of the plasma channel’s arc spot. Understanding the heat distribution into the workpiece in electrochemical arc machining with micro-machining parameters allows the further development of a micro-drilling process for electrically conductive materials based on electrochemical arc machining.     

Rapid casting of turbine blades with abnormal film cooling holes using integral ceramic casting molds

Film cooling is an important cooling method to decrease the turbine blade surface temperature, and its average cooling efficiency is mainly dependent on the cooling structures of internal passageways and the shapes of film cooling holes. Compared with standard cylindrical film cooling holes, abnormal film cooling holes have higher average cooling efficiency. But it is difficult to manufacture these holes using traditional machining methods. In this paper, a novel process was developed to fabricate turbine blades with abnormal film cooling holes by combining stereolithography (SL) technology with gelcasting technology. To decrease the drying shrinkage, the freeze-drying technique was applied to treat the wet ceramic casting mold green body surrounded by the SL mold, and the proper sintering process parameters were determined for lowering the sintered shrinkage. Finally, the integral ceramic casting mold was obtained, and a turbine blade with converging–diverging film cooling holes was rapidly cast to verify the feasibility of the proposed process.     

State-Of-Art,Challenges, and Outlook on Manufacturing of Cooling Holes for Turbine Blades

A cooling hole is important structure of turbine blades for high-performance aircraft engines. It is very challenging to manufacture cooling holes in superalloys including nickel-based and titanium alloys. This article aims to provide a critical assessment on the major types of machining processes for manufacturing cooling holes. The process mechanism, efficiency, form accuracy, and surface integrity of the state-of-art of four machining processes, i.e., mechanical drilling (MD), electrical discharge drilling (EDD), laser drilling (LD), and electrochemical drilling (ECD) have been thoroughly analyzed and compared in details. The future challenges and future potential research directions for the machining processes are also discussed.     

致密多孔层板冷却结构研究

应用FLUENT软件对内部绕流形式不同的7种层板结构进行流动与换热的耦合计算,分析扰流柱、冲击孔、气膜孔之间的排布方式以及堵塞比等参数对层板冷却效率与相对压力损失的影响规律。研究表明,层板结构以冲击孔和气膜孔呈现长菱形分布、扰流柱呈梭子形排布的方式较好,压力损失小,综合冷却效率可以提高10%左右;在进气流量相同的情况下,不同的层板结构压力损失相差不大,压力损失主要发生在从环腔经气膜壁进入火焰筒流出的过程中;增加扰流柱的数量或者是增大扰流柱的直径都会带来堵塞比的增大,层板的相对压力损失会随之增加,综合冷却效率增大,一定程度上强化了换热。     

Modeling and comparing of steady thermal state at gear milling by conventional and environment-friendly cooling method

The paper considers the thermal processes in gear machining being focused on comparison of several cooling and lubricating techniques used at gear milling. The study represents just a part of a complex research concerning the implementation of environment-friendly techniques to gear milling. The issues in the field of stationary heat transfer were conducted using finite elements analysis, a widely applicable method in engineering using Algor software. Modeling of steady thermal state in the gears at the end of the milling process has been done using the results of experimental researches and consisted of several steps: creation of gear model based on geometrical parameters; setting of boundary conditions; modeling of stationary thermal fields in the gear after processing by five different cooling methods; graphs of strains variation and heat stress; processing and interpretation of results.     

橡胶内衬台阶孔的加工技术

橡胶的回弹性大，导热性差，强度低，属于难加工非金属材料之一，本文阐述通过应用工艺装置改变切削区及其周围材料的受力状况，冷却润滑，优选刀具结构参数和加工工艺参数等多种技术途径研究提高橡胶台阶孔的加工质量和效率，加工试验取得了理想的效果。