Optimal Design of High-Speed Partial Flow Pumps using Orthogonal Tests and Numerical Simulations

To investigate the influence of structural parameters on the performances and internal flow characteristics of partial flow pumps at a low specific speed of 10000 rpm,special attention was paid to the first and second stage impeller guide vanes.Moreover,the impeller blade outlet width,impeller inlet diameter,blade inclination angle,and number of blades were considered for orthogonal tests.Accordingly,nine groups of design solutions were formed,and then used as a basis for the execution of numerical simulations(CFD)aimed at obtaining the efficiency values and heads for each design solution group.The influence of impeller geometric parameters on the efficiency and head was explored,and the“weight”of each factor was obtained via a range analysis.Optimal structural parameters were finally chosen on the basis of the numerical simulation results,and the performances of the optimized model were verified accordingly(yet by means of CFD).Evidence is provided that the increase in the efficiency and head of the optimized model was 12.11%and 23.5 m,respectively,compared with those of the original model.

Noise reduction mechanism of high-speed railway box-girder bridges installed with MTMDs on top plate

The issue of low-frequency structural noise radiated from high-speed railway(HSR) box-girder bridges(BGBs) is a significant challenge worldwide. Although it is known that vibrations in BGBs caused by moving trains can be reduced by installing multiple tuned mass dampers(MTMDs) on the top plate, there is limited research on the noise reduction achieved by this method. This study aims to investigate the noise reduction mechanism of BGBs installed with MTMDs on the top plate. A sound radiation prediction model for the BGB installed with MTMDs is developed, based on the vehicle–track–bridge coupled dynamics and acoustics boundary element method. After being verified by field tested results, the prediction model is employed to study the reduction of vibration and noise of BGBs caused by the MTMDs. It is found that installing MTMDs on top plate can significantly affect the vibration distribution and sound radiation law of BGBs. However, its impact on the sound radiation caused by vibrations dominated by the global modes of BGBs is minimal. The noise reduction achieved by MTMDs is mainly through changing the acoustic radiation contributions of each plate of the bridge. In the lower frequency range, the noise reduction of BGB caused by MTMDs can be more effective if the installation of MTMDs can modify the vibration frequency and distribution of the BGB to avoid the influence of small vibrations and disperse the sound radiation from each plate.

Design of high-speed signal acquisition system and analysis of signal integrity

The device is used for the test on the fuze detonating time according to the initial velocity of the projectile and the altitude and speed of enemy aircraft flight. For the special requirements of the high-speed signal acquisition in the process, the characteristics of the measured signal are analyzed. The system is investigated in chip selection, signal transmission, signal processing, signal storage, post-production PCB design, etc. The appropriate measures and solutions which affect the integrity and accuracy of the signal in each process are proposed. The rules for the layout of the device and wiring are made. The result show that the measurement values are accurate without loss of data.

利用Altium Designer进行PCB设计——以火灾预警系统为例

以火灾预警系统为例,介绍了利用Altium Designer软件进行PCB设计的过程。包括电路原理图、PCB图绘制的流程和方法以及用曝光法制作PCB实物的步骤和方法。总结了设计过程中的一些经验和技巧,为PCB设计学习者和爱好者提供参考。

Advances in design theories of high-speed railway ballastless tracks

The design theories of the ballastless track in the world are reviewed in comparison with the innovative research achievements of high-speed railway ballastless track in China.The calculation methods and parameters concerning train load,thermal effect,and foundation deformation of high-speed railway ballastless track,together with the structural design methods are summarized.Finally,some suggestions on the future work are provided.

Aerodynamic design on high-speed trains

Compared with the traditional train,the operational speed of the high-speed train has largely improved,and thedynamicenvironmentofthetrainhaschangedfromoneof mechanical domination to one of aerodynamic domination.The aerodynamic problem has become the key technological challenge of high-speed trains and significantl affects the economy,environment,safety,and comfort.In this paper,the relationships among the aerodynamic design principle,aerodynamic performance indexes,and design variables are firs studied,and the research methods of train aerodynamics are proposed,including numerical simulation,a reducedscale test,and a full-scale test.Technological schemes of train aerodynamics involve the optimization design of the streamlined head and the smooth design of the body surface.Optimization design of the streamlined head includes conception design,project design,numerical simulation,and a reduced-scale test.Smooth design of the body surface is mainly used for the key parts,such as electric-current collecting system,wheel truck compartment,and windshield.The aerodynamic design method established in this paper has been successfully applied to various high-speed trains（CRH380A,CRH380 AM,CRH6,CRH2 G,and the Standard electric multiple unit（EMU）） that have met expected design objectives.The research results can provide an effective guideline for the aerodynamic design of high-speed trains.

Parameters studies for rail wear in high-speed railway turnouts by unreplicated saturated factorial design

Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses(wheel-rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors(direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong 93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action ofbiaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value （high-cycle long-term dynamic strength） under the circum- stance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K30 were deduced, based on the characteristics of cumulative defor- mation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uni- axial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced sub- grade bed in the double-layer subgrade mode along with the change of K30 at the subgrade bed bottom. The double-layer structure mode of ＂closure on the upper layer and drainage on the lower layer＂ was proposed in order to meet the water- proofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10 4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10 2 cm/s is adopted on the lower layer.

基于响应曲面法的PCB/WCF改性沥青混合料优化设计

为改善废轮胎热解炭黑(PCB)改性沥青混合料的水稳定性,利用废弃鸡羽毛(WCF)的羊毛状纤维有益于沥青混合料水稳定性提升的特点,制备了AC-13 PCB/WCF改性沥青混合料。首先通过激光粒度仪,扫描电子显微镜与能谱仪分析了PCB与WCF的微观形貌与表面化学元素分布。然后基于响应曲面法(RSM)设计了PCB掺量、WCF掺量以及油石比对沥青混合料AC-13的空隙率、马歇尔稳定度以及冻融劈裂抗拉强度比影响的试验方案。最后通过方差分析(ANOVA)方法研究了3个自变量及其交互作用对沥青混合料的空隙率、马歇尔稳定度以及冻融劈裂抗拉强度比的影响,并建立了PCB/WCF改性沥青混合料AC-13性能预测模型。结果表明:PCB的粒径分布集中在197~358 nm,表面灰分会降低PCB与沥青的相容性;WCF羽轴两侧的羽片呈扇状分布,主要化学元素为碳、氮、氧、硫。由优化模型获得的PCB/WCF改性沥青混合料AC-13最佳优化参数为,PCB掺量0.52%,WCF掺量0.36%以及油石比5.5%;对应预测值为空隙率3.85%,马歇尔稳定度11.79 kN以及冻融劈裂抗拉强度比84.56%;基于最优参数配合比制备的PCB/WCF改性沥青混合料AC-13验证试验结果为空隙率3.69%,马歇尔稳定度11.6 kN以及冻融劈裂抗拉强度比84.9%,且都在95%置信区间内,表明模型具有较好的预测能力;优化设计的PCB/WCF改性沥青混合料AC-13的预测值和试验验证值均满足中国改性沥青混合料的性能要求。

高速PCB传输线信号完整性设计要点研究

为了解决高密度、集成化高速PCB中传输线因走线空间有限,走线设计不当所带来的信号完整性问题,采用理论分析、经验值设计、仿真分析的手段对8层高速PCB设计进行研究.分析高速PCB走线设计对传输线反射、串扰等信号完整性问题的影响.在PCB布线完成后,通过SI⁃wave软件仿真对PCB传输线线宽、线间距和阻抗值大小对信号完整性的影响进行研究,验证设计经验值3 W间距和50Ω阻抗的可靠性.指导PCB信号走线设计,达到信号的完整性,以期为实际工程实践应用提供参考和借鉴.

一种5G基站用PCB的压合填孔研究

在5G基站56 bps主板设计中,常用到高频材料与高速材料混压的M+2结构。针对M+2结构的印制电路板(PCB),在常规生产工艺中的二次压合之前,需要先使用树脂塞孔将2个子板的过孔填实。但树脂塞孔流程长,且子板叠构不对称,板翘影响其他工序加工。主要介绍一种半固化片(PP)三明治塞孔工艺替代树脂塞孔工艺,对于M+2钻带结构的板,使用本工艺时,子板在二次压合前,盲孔不需要做树脂塞孔。在二次压合的时候,直接使用PP填孔,既能保证填孔的饱满度、各项PCB品质要求,又能减少流程,降低加工成本,并且还能大幅度提升生产效率。

Multi-objective reliability optimization design of high-speed heavy-duty gears based on APCK-SORA model

For high-speed heavy-duty gears in operation is prone to high tooth surface temperature rise and thus produce tooth surface gluing leading to transmission failure and other adverse effects,but in the gear optimization design and little consideration of thermal transmission errors and thermal resonance and other factors,while the conventional multi-objective optimization design methods are difficult to achieve the optimum of each objective.Based on this,the paper proposes a gear multi-objective reliability optimisation design method based on the APCK-SORA model.The PC-Kriging model and the adaptive k-means clustering method are combined to construct an adaptive reliability analysis method(APCK for short),which is then integrated with the SORA optimisation algorithm.The objective function is the lightweight of gear pair,the maximum overlap degree and the maximum anti-glue strength;the basic parameters of the gear and the sensitivity parameters affecting the thermal deformation and thermal resonance of the gear are used as design variables;the amount of thermal deformation and thermal resonance,as well as the contact strength of the tooth face and the bending strength of the tooth root are used as constraints;the optimisation results show that:the mass of the gear is reduced by 0.13kg,the degree of overlap is increased by 0.016 and the coefficient of safety against galling Compared with other methods,the proposed method is more efficient than the other methods in meeting the multi-objective reliability design requirements of lightweighting,ensuring smoothness and anti-galling capability of high-speed heavy-duty gears.

嵌入式系统中PCB设计的EDA自动化流程优化

针对嵌入式系统中的PCB设计,探讨了EDA(电子设计自动化)工具在优化自动化设计流程中的应用。首先,分析了嵌入式系统中PCB设计的特点及其在自动化设计流程中面临的挑战。然后,着重讨论了利用EDA工具进行设计流程优化的方法,包括设计自动化、流程简化、错误检测与修正机制。还提出了一种基于EDA工具的集成化设计环境,旨在提高设计效率和准确性,减少人为错误。

在PCB制造中降低机械钻孔成本的策略

主要探讨印制电路板(PCB)钻孔流程的设计成本和生产效率优化策略,重点从钻孔机参数设定、叠板设计及工程资料设计的细节方面进行深入分析。对钻孔机的主轴行程进行合理化设置,对叠板结构中的板厚区间进行细化区分,简化钻孔工程资料的板边标识孔设计,从而达到节省钻孔成本的目的。

TMS320F开发板的PCB设计与实现

阐述了TMS320F开发板的印制电路板(PCB)设计情况,分析了TMS320F开发板的整体布局布线及其子模块的详细布局布线。研究结果有助于对整个PCB设计进行优化,可为类似的PCB设计提供有借鉴意义的参考。

OPTIMUM DESIGN OF HIGH-SPEED RAILWAY LOCOMOTIVE TRACTION GEAR

On the basis of deep investigation of locomotive traction gears manufactured at home and abroad , a variety of measures are putted forward to improve the driving load-bearing capacity and working life of our country's high-speed locomotive traction gears. The measures include the fol- lowing five aspects : optimally selecting the material and heat treatment process , optimally designing the tooth profile . reasonably choosing the manufacture accuracy and technique , optimally choosing the lubricant and the way of lubrication and seal , improving the dynamic feature of the gearing. In the respect of the tooth profile , a hob with optimal cutter angles is designed to make root thickness on the dangerous section as large as possible and the stress concentration as small as possible. Ad- dendum modification coefficient is optimized to minimize the maximum flash temperature in the course of meshing. Finally . finite element analysis method is used to calculate the deformation and the stress of teeth accurately. And on this basis , optimal profile correction and axial modification have been designed with regard to the start , continuious running and high speed travel of the loco- motive .

Altium Designer 10 PCB设计过程优化探讨

电子设计自动化EDA是现在电子信息类设计人员必用软件,Altium Designer又是其中一款功能强大的应用软件。要通过它设计出真正性能稳定的印制电路板PCB,需要不断地练习和累积。文中通过实例描述了Altium Designer10绘制原理图和生成PCB的详细过程,并给出一些设计PCB过程中容易出错的地方和器件布局中会遇到的问题,总结具体经验供相关人员参考。

基于Altium Designer的数码管显示电路的PCB板设计

根据数码管现实电路的原理,并结合实例,介绍了在Altium Designer 6中进行数码管显示电路的PCB板设计的具体方法,从而使工程技术人员在实践中能够快速地提高设计效率。

Altium Designer技术在PCB板设计中的应用研究

随着科学技术的快速发展,计算机技术的开发与应用已涉及到了人类工作和生活的各个领域,尤其是在PBC板的设计方面,计算机技术已完全渗透进了相关设计的各个环节。该文以Altium Designer技术为基础,对Altium Designer技术的定义及功能进行了介绍,并对其在PBC板设计中的应用进行了分析。

Design methodology,synthesis,and control strategy of the high-speed planetary rover

The planned missions to explore the surfaces of the Moon and Mars require high exploration efficiency,thus imposing new demands on the mobility system of planetary rovers.In this paper,a design method for a high-speed planetary rover(HPR)is proposed,and the representative configurations are modeled and simulated.First,the influence of the planetary surface environment on the design of HPRs is analyzed,and the design factors for HPRs are determined by studying a single-wheel suspension.Second,a design methodology for HPRs is proposed.The adaptive suspension mechanisms of a four-wheeled rover are synthesized using the all-wheel-attachment condition and position and orientation characteristics theory,which are expressed in the form of a graph theory for the increase in elastic components and active joints.Finally,a dynamic model is built,and a simulation is carried out for the proposed rover.The validity of the proposed method and rover is verified,thus highlighting their potential application in future planetary exploration.