Neural-network simulation of diesel operation under a nonsteady load

The operation of diesel engines with nonsteady loads is considered. Numerical experiments are based on a model, a neural network, and test-bench data.     

浅孔钻"非稳态"加工应力应变分析

以安装两片硬质合金刀片的可转位浅孔钻为例,在采用有限元方法建立浅孔钻"非稳态"加工时的力学模型的基础上,利用优化后的几何参数用数值仿真技术对各阶段的应力应变进行了研究,得出了最大应变发生的加工阶段、最大应力发生的刀具部位,还得出了加工孔的理论扩大量,为浅孔钻结构设计和使用提供了理论依据.     

某燃气轮机涡轮叶片的模态和疲劳分析

燃气轮机作为大型舰船动力装置,是影响舰船上各种设备正常运行的重要原玉,转子叶片的疲劳损坏一直影响燃气轮机的正常工作.首先利用UG软件对某型燃气轮机涡轮叶片建立了三维实体模型,通过IGES交件载入HyperMesh软件中划分网格和施加约束,最后导入ANSYS软件中,对叶片进行了约束模态分析.分析了叶片的应力分布情况,并在此基础上完成了叶片的疲劳强度计算,为叶片的设计以及改进提供了参考.     

Turbine vibration with a pulsed kinematic perturbation

A basic algorithm for calculation the rotor and bearing vibrations in a turbine due to a kinematic shock is outlined. Some results are discussed for linear vibrations of a rotor on three bearings with a determinate pulsed perturbation.     

Analysis and experiments of iterative learning-control system with uncertain dynamics

An iterative error compensation approach is proposed in this article to improve the accuracies of high speed, computer-controlled machining processes. It is well known that the high-speed computer-numerically-controlled (CNC) machines are extremely useful in terms of manufacturing mass-produced parts. The proposed method uses an iterative learning technique that adopts the servo commands and cutting error experienced in previous maneuvers as references to current compensative actions. Moreover, non-repetitive disturbances and nonlinear dynamics of the cutting processes, and servo systems of the CNC machine that greatly affect the convergence of the learning-control systems were also studied in this research. State feedback and output feedback techniques were adopted in the proposed controller design. In addition to the stability analysis, a 1 degree-of-freedom servo positioning system is constructed to evaluate the performance of our proposed learning control approach. Both the simulation and experimental results verify the effectiveness of our approach.     

基于传递矩阵法的风力发电机组整机模态分析

在风力发电机组的结构动力学设计中,整机自振频率和振型是重要的设计参数。作者根据风力发电机组结构特点将其简化为带扭转变形的无质量梁单元和集中质量惯量单元的有序组合,并根据单元受力特点建立了梁单元和集中质量惯量单元的传递矩阵。以叶尖为输入,塔架底部为输出,根据多体系统传递矩阵模型构建原理,建立了风力发电机组整机传递矩阵模型,并使用该模型对NREL 5MW风力发电机组模型进行了模态分析。结果表明:传递矩阵法所得分析结果准确可靠,相对于有限元法,传递矩阵还具有建模灵活、计算效率高、无需建立系统总体运动方程等优点,非常适合风力发电机组的设计和优化。     

MAN主机涡轮增压器排气叶片损伤故障原因分析

MAN 16V32/40型双燃料柴油机运行中,一台主机增压器出现了剧烈震动,在主机报警关停后,现场人员对主机增压器做了一系列的检查,确认故障原因.通过对主机滑油压力、温度等参数的分析,并拆检增压器,发现故障原因主要为排气端叶片损伤,而增压器喷嘴环的坚硬积碳是废气端叶片损坏的主要因素,同时叶片长时间运行后,其强度性能下降,有疲劳损伤的可能性.通过故障现象分析,提出了改进措施,控制住造成主机叶片损伤的关键因素,保证设备稳定和人员安全.     

电火花堆焊修复电厂蒸汽轮机壳体

采用电火花堆焊工艺成功修复了山东某电厂蒸汽轮机壳体密封面，取得了较好的经济效益。     

MAN主机涡轮增压器排气叶片损伤故障原因分析

MAN 16V32/40型双燃料柴油机运行中,一台主机增压器出现了剧烈震动,在主机报警关停后,现场人员对主机增压器做了一系列的检查,确认故障原因.通过对主机滑油压力、温度等参数的分析,并拆检增压器,发现故障原因主要为排气端叶片损伤,而增压器喷嘴环的坚硬积碳是废气端叶片损坏的主要因素,同时叶片长时间运行后,其强度性能下降,有疲劳损伤的可能性.通过故障现象分析,提出了改进措施,控制住造成主机叶片损伤的关键因素,保证设备稳定和人员安全.     

Wilson法对旋风力机气动设计与数值模拟

提出了Wilson法设计上游风轮,利用尾流模型得到下游风轮处轴向风速,代入Wilson法设计下游风轮的设计思路,完成3kW同半径同尖速比的对旋风力机设计。通过数值模拟与基于动量叶素理论及Glauert修正方法的理论程序,对风力机上游风轮进行变转速性能验证,两者均显示在设计点风力机功率系数达到较高值,CFD结果0.455略低于程序结果0.563。对旋风力机数值模拟显示功率系数可达到0.501,较单级功率提高10.11%,设计点处两级风轮转速达到最佳匹配。     

柔塔式风力机组载荷测试与仿真分析

柔塔式机组是低风速高剪切地区首选风力机组,由于机组的高塔架特点,其载荷特性是结构设计的重点.基于新版载荷测试标准,对140 m塔高机组开展载荷测试,重点关注机组的频谱特性以及叶片与塔架主要部件的载荷,并与仿真结果进行对比分析.结果表明,机组仿真结果模态与载荷输出结果与测试数据相近,验证了仿真模型的正确性,研究结果对风力...     

双叶片立轴风力机及其性能分析

提出了一种新型的双叶片风力机,建立了该风力机的计算模型,基于对叶片的运动学和空气动力的分析,导出了其性能参数的计算方法。结合设计实例,对该风力机的性能进行了仿真分析,结果表明:双叶片风力机在一定的风速和负载下能稳定地运行,最大风能利用率随输出转速呈抛物线规律变化,存在使风能利用率最大的最佳输出转速。     

Photon emission experiments with the scanning tunnelling microscope

We have detected the light emitted from an STM at both ultraviolet (9·5 eV) and optical (1–4 eV) energies. We show that this light contains spectroscopic information on the sample surface comparable to conventional inverse photoelectric spectroscopy, but with nearly atomic spatial resolution. At optical energies we found sufficiently high intensities to allow spatial imaging of the emission probability. We propose that the high quantum efficiency is due to resonance phenomena, and present fluorescence spectra of the emitted light that support this view. We believe that atomic resolution inverse photoemission microscopy and spectroscopy will provide an important new dimension to surface studies.     

Active collimators in experiments with exotic nuclear beams

The active collimator method for experiments with exotic nuclear beams at energies near the Coulomb barrier of nuclear reactions is described. The technique is based on the use of detectors composed of microchannel plates (MCPs) and thin strips of metal foils (Au, Ag, Al) with a thickness of 200–300 μg/cm² or less, which are oriented along axes X and Y (axis Z is collinear to the beam axis). Exotic nuclei passing through the foils are detected by the MCPs by electron emission from these foils, which provides a means for obtaining spatial information on the particle trajectory and the time mark of an event. The proposed setup is characterized by the smallest (of the available techniques) material budget on the particle path (≤8.0 × 10¹⁷ atoms/cm²) in the zone of detected particles, the high efficiency (ɛ ∼ 90% for every MCP), and the time resolution sufficient for performing additional identification of radioactive nuclei using the time-of-flight method.     

Sagnac-loop phase shifter with polarization-independent operation

A bulk-optics, polarization-independent phase shifter for photonic quantum information applications is demonstrated. The device is based on a transverse electro-optic modulator in a Sagnac-type loop containing Faraday rotators. This direction-dependent polarization rotation in the loop is combined with a Mach-Zehnder interferometer to form an optical switch with an on/off contrast of 96% and a switching time of 1.6 ns. We demonstrate that the device's operation maintains any arbitrary polarization state.     

车架静力试验与有限元静力分析

进行车架的静力试验和有限元法静力分析，对比试验结果与有限元计算结果，分析两者误差原因，改进有限元模型，使得两种结果的误差在一定范围内，有限元法静力分析能够代替车架静力物理试验。     

三维激光切割隔板围带工艺分析

制定了一种新的汽轮机隔板围带叶栅型孔加工方法,对工艺方案进行了分析及改进,充分利用三维激光切割优势,保证了型孔精度及叶栅焊接质量.     

面向交互操作的虚拟工具建模与操作技术

为解决虚拟装配中的工具建模以及交互式工具操作仿真问题,在分析交互式虚拟装配对工具功能需求的基础上,提出适合各类装配工具信息表达和操作的统一建模方法,并给出适用于不同类型工具的一般操作方法。以典型工具的实现方法为例,说明了工具的建模与驱动实现过程。将该工具应用于某型汽车发动机的装配操作仿真中,验证了所提建模与操作方法的有效性。     

一种带浮动转子的涡轮节新结构

针对涡轮钻具轴承组受定转子限制,允许磨损量小,寿命短的问题,设计了一种转子可沿轴滑动的浮动转子涡轮节。它采用上下轴承组结构,利用其不等载荷。上轴承组磨损慢,弹簧力推动转子使转子靠在上轴承上,定位转子和定子,从而加大下轴承组的允许磨损量来提高涡轮钻具的整体寿命。