汽蚀对离心泵性能影响的实验研究

离心泵长时间运转后,会出现危害严重的汽蚀现象,造成泵性能下降,严重时影响泵的效率、寿命,甚至造成离心泵内部部件损坏。文章通过改变进口压力的方法对单泵、双泵并联、双泵串联等工况下汽蚀对离心泵性能影响进行实验研究。结果表明:当进口压力小于输送液体的饱和蒸汽压时,液体开始发生气化并伴随气泡产生,表明泵内发生汽蚀;汽蚀初期离心泵的效率开始下降,但表现不明显;随着汽蚀不断增大至严重汽蚀区时,Q 1~η曲线出现陡坡,效率出现明显下降并伴随嗡响。实验证明采用提高泵的进口压力等措施可适当减小汽蚀对泵性能的不利影响。     

某核电机组水压试验泵汽轮发电机组启动试验不成功分析处理

对某核电机组水压试验泵汽轮发电机组启动试验不成功进行了分析与处理。由于限流器单向密封圈老化,导致2LLS003VV阀门开启时间与2LLS001VV阀门开启时间不匹配,从而导致小汽机瞬时进汽量过大,启动过程中跳机。根据原因分析制定处理措施,解决了小汽机启动试验不成功问题。     

一种适用于超高速冲压新型产品的冲裁模具结构

为实现超高速模具量产,对经典的U型冲裁结构进行了优化,将原始的分离式U型冲裁和下废料双工位优化为单工位一步式冲裁和下废料工艺,新结构将产品切除和废料切除工位融合到一起,提高了U型凸模的强度、缩短了模具长度、减小了跳废料率,保证了产品质量;新结构在同一工位上同时获得产品且切除废料,无需采用连料方式传送废料,从而缩短了原材料的宽度,降低了材料成本,减少了误送。同时,模具速度从原有的800次·min-1提高到2000次·min-1,实现了超高速的目的,并且该新结构被成功地推广到其他相类似的结构中,实现了技术的互通性。     

Centrifugal Pumps as Extractors

The generation of dispersions with defined droplet size distributions is important for liquid-liquid extraction. In this respect, the capability of a centrifugal pump to generate dispersions was investigated for different operating points. For the analysis of the mixing process, a centrifugal pump was designed translucent. High-speed images reveal the mechanism of particle breakup. Optical measurement technology and image processing with neural networks were used to determine droplet size distributions. The influence of flow rate, rotational frequency and holdup are discussed for a paraffin oil-water system.     

天玛国产化泵站常见故障分析

为了更好地指导天玛国产化泵站的推广和应用,对天玛国产化泵站优点及常见故障展开分析与探讨。从该泵站的结构组成出发,通过对比进口泵站,阐述了该泵站在增加乳化油箱系统、回液箱系统及一台高压泵,改进乳化液混液系统、采用先进的RS485通讯系统、单泵采用两种供液方法和独立的强制润滑系统、喷雾泵采用两种机械调压方法等方面具有的优势;以表格的形式列出了该泵站不同类型的故障描述和说明。分析认为,该泵站不仅具有进口泵站的先进设计和制造技术,还充分考虑了神东公司井下现场的实际需要,可以有效地替代进口泵站,满足高产高效矿井的要求,具有一定的推广价值。     

A novel adaptive convolutional neural network for fault diagnosis of hydraulic piston pump with acoustic images

As an essential part of hydraulic transmission systems, hydraulic piston pumps have a significant role in many state-of-the-art industries. Thus, it is important to implement accurate and effective fault diagnosis of hydraulic piston pumps. Owing to the heavy reliance of shallow machine learning models on the expertise and experience of engineers, fault diagnosis based on deep models has attracted significant attention from academia and industry. To construct a deep model with good performance, it is necessary and challenging to tune the hyperparameters (HPs). Since many existing methods focus on manual tuning and use common search algorithms, it is meaningful to explore more intelligent algorithms that can automatically optimize the HPs. In this paper, Bayesian optimization (BO) is employed for adaptive HP learning, and an improved convolutional neural network (CNN) is established for fault feature extraction and classification in a hydraulic piston pump. First, acoustic signals are transformed into time–frequency distributions by a continuous wavelet transform. Second, a preliminary CNN model is built by setting initial HPs. The range of each HP to be optimized is identified. Third, BO is employed to select the optimal combination of HPs. An improved model called CNN-BO is constructed. Finally, the diagnostic efficiency of CNN-BO is analyzed using a confusion matrix and t-distributed stochastic neighbor embedding. The classification performance of different models is compared. It is found that CNN-BO has a higher accuracy and better robustness in fault diagnosis for a hydraulic piston pump. This research will provide a basis for ensuring the reliability and safety of the hydraulic pump.     

一种考虑介质污染度的液压泵轴尾机械密封磨损的计算方法

为了准确计算液压柱塞泵机械密封的磨损,基于有限元方法提出一种考虑污染度水平和机械密封运动工况的磨损量计算方法。首先,针对单个磨粒模型建立机械密封表面的有限元模型,并基于实际工况进行仿真;然后对仿真和实验数据进行回归分析,确定单个磨粒造成的磨损量;最后研究介质中多种磨损颗粒对机械密封表面磨损的综合影响,提出一种考虑油液污染度的液压柱塞泵轴尾密封磨损的计算模型。通过对轴尾密封的表面观测结果,验证机械密封的磨损形式,并计算得出实际磨损量。通过对比基于提出的模型的解析结果与实际观测结果,证明提出的方法在计算含污染颗粒的机械密封磨损量时的有效性。     

庞庞塔煤矿综采工作面恒压供液系统研究

结合庞庞塔煤矿综采工作面的具体应用现状,设计了变频驱动控制的恒压供液系统。在泵出口管道中设置压力传感器、流量计等,同时在每台液压支架乳化液入口处安装一个蓄能器。压力、流量等数值由各种传感器来进行采集,并把监测到的数据反馈给PLC控制器。PLC控制器通过把传感器送来的数据和系统预设好的数值进行比较来判断供液系统是否需要加压或着减压,以此通过变频器来改变电机的转速,以实现供液系统维持恒压状态。     

异形医用双腔导管挤出离模膨胀变形机理与调控

如何准确预测和精密调控异形医用双腔导管的离模膨胀变形是实现其精密成型的关键技术。通过传统和气辅精密成型的对比分析，研究表明离模膨胀变形是由熔体的第二法向应力差驱动的径向二次流动所诱发，传统挤出成型会产生较大的第二法向应力差，第二法向应力差驱动诱发的径向二次流动是离模膨胀变形的直接驱动力，从而导致传统挤出成型的异形医用双腔导管不仅产生离模膨胀，而且还产生椭圆度误差，其最大离模膨胀比和椭圆度误差分别为1.86和6.3 %。异形医用双腔导管的气辅精密挤出成型基本可以消除熔体的第二法向应力差，必然消除了挤出成型过程的径向二次流动，从而实现了异形医用双腔导管的精密控形。