提高离心泵效率的可行性分析

通过对离心泵的叶轮结构和进口技术改进,充分利用叶轮内部空间,降低泵内损失,提高泵效率,称为新型离心泵。其特点一是减小叶轮盖板,使叶轮成为不完全封闭叶轮;二是叶片进口延长至叶轮进口附近,叶片的轴向部分和轴向径向之间的过渡部分为双曲混流叶片。     

超速预加载叶轮弹塑性模拟与试验验证

利用Workbench软件,只考虑叶片受到的离心力,忽略气动力和轴的作用力,对实际叶轮进行有限元模拟,得到了正常加载和超速预加载过程的应力与应变分布规律,并与X射线衍射仪测定的真实叶片残余应力分布规律进行对比。结果表明:两种加载情况下最大应力都出现在叶轮边缘,经过超速预加载后叶轮的最大应力减少了325 MPa,同时在整个超速预加载过程中等效塑性应变均不变。     

航空发动机离心叶轮叶片的振动设计

对航空发动机离心叶轮叶片的振动设计中的有关问题进行了探讨.介绍了离心叶轮的结构特点和振动破坏模式,探讨了引起共振的原因及相应的改进措施,讨论了离心叶轮叶片强度振动分析方法.     

五轴联动数控展成电解磨床原理与控制

为解决整体叶轮叶片型面的精加工难题,进行了五轴联动数控展成电解磨削整体叶轮的基础研究。根据数控展成电解磨削整体叶轮叶片型面这一加工方法的特点,在分析了数控展成电解磨削整体叶轮原理的基础上,对磨削系统的结构与运动进行了总体设计,提出了经济型多轴数控系统及其联动控制方法,建立了电解磨削非平行直纹展成曲面的数学模型,开发了五轴联动数控展成电解磨削自动数控编程系统,对航空发动机整体叶轮的叶片型面进行了电解磨削。五轴联动数控展成电解磨削技术为整体叶轮叶片型面的精加工提供了一种新的加工手段。     

不同型线的高效二元离心叶轮优化设计

对具有无叶扩压器的离心压缩机两元叶轮的三种叶片型线进行对比研究,采用单圆弧和等减速流型法设计离心叶轮叶片型线,得到其性能曲线和内部流场,运用正交设计试验方法对离心压缩机叶轮进行了变减速流型优化设计,并对比分析了变减速流型与等减速流型的性能曲线。结果表明当叶片的进出口角确定后,叶片型线改变时,叶轮做功能力略有提升,而对整个叶道内的静压和速度分布影响较大,以致影响级性能。     

基于前缘锯齿形叶片的多翼离心风机数值分析与实验研究

为减少叶片附近的涡流,降低多翼离心风机流场的流动损失和气动噪声,设计了一种具有锯齿形前缘的空调器用离心风机叶片。与常见改型叶片不同,并未从整个叶片宽度方向进行改进,仅从叶轮前盘沿叶片前缘的1/3叶轮宽度处开设锯齿结构。基于几何相似原理和FLUENT软件,对计算得出的不同锯齿结构进行数值模拟,结果显示:锯齿结构主要对聚集在靠近前盘的涡流进行破坏,蜗舌、叶片后缘和叶间涡流较原型叶片也明显减少,且降低了基频噪声。结果表明:在不同转速下,前缘锯齿形叶片多翼离心风机的整机风量较原型机基本不变,噪声值降低0.9～1.2 dB(A),输入功率降低2.75～3.55 W。说明具有锯齿形前缘结构的叶片,不仅能优化风机的风道性能,还能起到节能降噪的作用。     

汽轮机转子末叶片销孔加工装置的设计

位于汽轮机转子各级叶轮的末叶片采用锥型销孔锁紧结构。由于每两级叶轮间的距离最小可达到75mm,普通钻床很难达到钻孔要求。为了提高加工效率,针对目前某公司的加工现状,设计了一种新型的钻孔装置。新型的钻孔装置主要由定位与卡紧装置、进给装置、传动装置、平衡装置等四部分组成。装置在固定与卡紧部分巧妙的使装置在短时间内快速卡紧,并通过人工对手柄的控制,实现工作台在XYZ方向的移位。平衡装置能够最大减少工人的劳动强度,提高工作效率。     

叶片非均匀分布对斜流叶轮气动噪声的影响

针对某型斜流叶轮的气动噪声问题,基于FW-H方程利用FLUENT软件对叶片非均匀分布斜流叶轮的气动噪声进行数值模拟,获得叶片非均匀分布下斜流叶轮气动噪声的分布特性,并对比分析非均匀分布对气动噪声的影响规律。计算结果表明,叶片非均匀分布可以降低叶片基频及谐频上的声压幅值。研究结果可为斜流叶轮的优化设计提供理论依据。     

涡轮流量计内部流场数值模拟研究

利用数值仿真技术对涡轮流量计内部流场进行了研究,目的是为优化涡轮流量计的结构设计提供指导。利用叶轮转速与平均力矩系数存在线性关系,提出两点法确定叶轮在力矩达到平衡状态下的转速。数值分析结果表明,前导流件叶片后形成的尾流影响叶轮人口的流体速度分布,继而影响叶轮的旋转稳定性;叶轮叶片压力面上靠近叶片前缘以及吸力面上靠近尾缘处存在压力突变区,易产生脱流现象;叶轮轮毂前后间隙区内流体受叶轮旋转影响而易产生漩涡流和明显的切向速度分量。     

叶轮对汽轮机叶片振动特性的影响分析

汽轮机叶片振动特性是影响汽轮机安全性的关键因素之一。本文以某型叶片为研究对象,建立三维叶片有限元模型,在考虑叶片预应力条件下,分别讨论叶轮及工作转速对叶片振动特性的影响,并进行了相关的对比分析。通过叶片振动频率变化,分析工作转速及叶轮对叶片振动影响的主要阶次范围,为叶片有限元分析设计提供参考意见。     

基于三维实体造型的搅拌器叶轮结构反求及其抗磨性能

 某污水处理厂的潜水搅拌器叶轮磨损严重，且叶轮备件需从国外进口。为了解决该叶轮的抗磨损问题，实现备件的国产化，基于反求工程设计理论，应用三坐标测量机、Surfacer软件和Pro/E软件获得原叶轮的三维实体造型，所获得的叶轮实体造型与原型有较高精度的一致。应用叶轮实体造型，完成叶轮模具的制造、叶轮的抗磨损研究和备件的国产化工作。新叶轮已应用于该污水处理厂，并通过了现场生产运行试验。试验结果表明：叶轮的搅拌和推进效果很好，运行3个月后无磨损情况发生，经济效益和社会效益显著。     

Cooling slope casting to obtain thixotropic feedstock I: observations with a transparent analogue

New Rheocasting (the NRC process) is a recently developed semisolid processing route. There are two versions of this route. In one, molten alloy is poured directly into a tilted mould and through careful temperature control during cooling a spheroidal semisolid microstructure is achieved, before the material in the mould is upended into a shot sleeve and hence forced into a die. Alternatively, the molten alloy is poured onto a cooling slope and thence into a mould before processing. The aim of the work described in this article, and its companion, was to develop understanding of the microstructural development during the initial stages of this process i.e. in the mould before processing and with the cooling slope/mould combination. In this first article, an analogue system based on aqueous ammonium chloride has been used to visualise what happens when an alloy is poured into a tilted mould with a chill wall. In the companion article, the results for pouring A356 aluminium alloy directly into a mould, and also via a cooling slope into a mould are presented.     

Cooling slope casting to obtain thixotropic feedstock II: observations with A356 alloy

New Rheocasting (NRC) is a recently developed semisolid processing route. There are two versions of this route. In one, molten alloy is poured directly into a mould and through careful temperature control during cooling a spheroidal semisolid microstructure is achieved, before the material in the mould is upended into a shot sleeve and hence forced into a die. Alternatively, the molten alloy is poured onto a cooling slope and thence into a mould before processing. The aim of the work described in this paper, and its companion, was to develop the understanding of the microstructural development during the initial stages of this process, i.e. in the mould before processing and with the cooling slope/mould combination. In the previous paper, an analogue system based on aqueous ammonium chloride has been used to visualise what happens when an alloy is poured into a tilted mould with a chill wall, which acts to mimic the mould and the cooling slope in the NRC process. In this companion paper, the results for pouring A356 aluminium alloy directly into a mould, and also via a cooling slope into a mould, are presented.     

Numerical simulation of solid-liquid mixing characteristics in a stirred tank with fractal impellers

The hydrodynamics of solid-liquid mixing process in a stirred tank with four pitched-blade impellers, fractal 1 impellers, and fractal 2 impellers were investigated using computational fluid dynamics (CFD) simulation. An Eulerian-Eulerian approach, standard k-ε turbulence model, and multiple reference frames (MRF) technique were employed to simulate the solid-liquid two-phase flow, turbulent flow, and impeller rotation, respectively. The effects of impeller speed, impeller type, impeller spacing, impeller blade tilt angle, impeller blade shape, solid particle size and initial solid particle loading on the solid particle suspension quality were investigated. Results showed that the homogenous degree of solid-liquid system increased with the increase of impeller speed. The impeller spacing of T5/6 and T and impeller blade tilt angle of 60° and 45° were appropriate for the solid-liquid suspension process. Fractal shape impeller was more efficient than jagged shape impeller in solid-liquid mixing process. Larger particle diameter and higher initial solid particle loading resulted in less homogenous distribution of solid particles. It was found that fractal impeller could improve the solid particle suspension quality compared with four pitched-blade impeller under the same power consumption, increasingly so with the fractal iteration number of fractal impeller. Moreover, fractal impeller reduced the size of impeller trailing vortex and consumed less power consumption compared with four pitched-blade impeller at the same impeller speed, and the more the number of fractal iteration, the higher the impeller energy utilization rate of fractal impeller.     

拖钩套筒复合冷挤压数值模拟与毛坯优化

将挤压模具视为刚体,采用有限元分析软件MARC,对拖钩套筒零件进行了冷挤压过程的数值模拟计算。根据各主要阶段等效应力及等效应变的分布,总结了挤压过程中金属材料塑性流动的规律。以最大挤压力为目标,对毛坯的尺寸进行了优化,为挤压工艺的改善提供了依据。根据计算结果,得出了挤压完成后零件所受最大主应力数值及其分布规律,为后期模具强度的研究奠定了基础。     

A power transducer system for the ultrasonic lubrication of the continuous steel casting

A critical point in the continuous steel casting process exists in the meniscus zone of the cooled mould, i.e., the region in which the steel stream flowing out of the tundish nozzle starts to solidify. This is a critical point because of the sticking that occurs between the solid shell of steel and the mould. In this work, a new system for the ultrasonic lubrication of the continuous steel casting is proposed and experimentally tested. The basic idea is to excite one of the mould's natural vibration modes by means of a distributed ultrasonic source. This source is composed of an array of power emitters, with each of them placed upon an antinode of the mould. An experimental characterization of the vibrational behavior of a square mould was first carried out. The most active resonance modes of the mould were detected with an experimental technique based on a simple impedance measurement. The modal shape of the selected mode, and hence the position of antinodes, was obtained by means of interferometer measurements. Additional experimental investigations were performed by exciting mould vibrations with up to four piezoceramic disks placed on different sets of antinodes. Some positioning criteria to maximize the superposition effect were derived. Measurements were obtained through excitation of the mould with up to four Langevin-type power emitters, designed and manufactured to work at the mould's selected resonance frequency. These measurements have shown that, by increasing the number of emitters, the ultrasonic power transmitted to the mould and, consequently, the maximum available displacement, increases. Other practical advantages of the proposed system are highlighted and discussed.     

中开口钢包装桶模具结构研究及优化设计

目的 针对中开口钢包装桶生产工艺流程长、 模具套数多及占用压力机较多的问题, 对模具结构进行研究并提出优化设计方案。方法 分析生产工艺要求, 应用复合模具技术, 通过结构研究、 材料选择和优化设计方案, 计算各套模具的冲压力, 并确定压力机型号。结果 结构设计可靠、 制造方案优化的复合模具能满足生产工艺要求, 实现了合并工序的目的。结论 通过模具结构研究及优化设计、 改造生产流程、 应用复合模具合并工序, 可减少压力机台数, 提高了钢桶生产效率及经济效益。     

激光复合织构薄壁弯管模具成型试验

目的研究激光复合织构薄壁弯管模具的成型性能。方法分析模具与管件的摩擦对弯管成型的影响规律。利用激光毛化和微造型技术对弯管模具的夹块、压块、防皱板进行表面复合织构,完成了绕弯成型对比试验,采用直接测量法对成型件的外壁减薄率和截面畸变程度进行检测,结果弯管模具经过复合织构后,成型件外壁减薄率降低了0.5%~4.5%,截面畸变程度减轻了0.8%~2%,对于表面质量较好的不锈钢管,激光复合织构弯管模具能够使成型件表面保持较低的表面粗糙度和良好的光泽度。结论将激光复合织构技术应用于弯管模具,能够显著提高成型管件的质量。     

角膜曲率计轴位标准器的研制

为解决角膜曲率计的轴位检定,研制出角膜曲率计轴位标准器,由轴位模拟眼、轴位套筒与测量支架组成。轴位模拟眼为方形柱体,前表面为环曲面,后表面为磨砂平面,轴位模拟眼位于轴位套筒的方形通孔内,轴位套筒放置于测量支架的梯形测量槽内,通过装配和机械定位实现0°、45°、90°和135°的轴位测量,其轴位扩展不确定度U=0.5°(k=2)。实验结果表明,该轴位标准器可以满足各类角膜曲率计的轴位检定和校准。同时,还将提升现有角膜曲率计工作基准的测量能力,并为相关计量检定规程的修订和完善提供技术基础。     

摄像定位分段爆破技术在堵井处理施工中的应用

通过在堵井段上方搭设钻孔平台,进行套管跟进钻孔,采取自下而上分段爆破处理堵井,实现了快速疏通堵井的目的。拔管、装药、爆破检查全过程采用了摄像技术精确定位和监控,具有步骤简单、可操作性强、使用效果好和受施工条件限制小的优点。采用该方法进行堵井导通处理,既加快了施工进度、节约了成本,又可确保堵井处理全过程安全可靠。