周转轮系的传动效率分析

周转轮系的传动比计算比较复杂,也常被设计者所忽略,然而,有些周转轮系却因效率太低而失去意义.在分析影响传动效率的众多因素的基础上,将周转轮系分为8种情形,分别推导出其效率计算公式.最后通过一系列的应用实例,验证了计算方法的有效性和核算轮系效率的丛要性,指出轮系的效率,不仅取决于单个齿轮副的效率,还与哪个轴被固定、哪根轴...     

Dynamic behavior of a two-stage gear train used in a fixed-speed wind turbine

The dynamic behavior of a two stage spur gear system used in a typical wind turbine is investigated in this paper. With the purpose of having an accurate simulation, for a given excitations, of the dynamic response of bearings, shafts and teeth in contact.In this study, we developed a lamped mass dynamic model with 12 DOFs. This model is excited by external and internal issues sources. The main factors of these excitations are the variability in the wind resource and the time varying mesh stiffness fluctuation.The aerodynamic torque is calculated from an empirical approach of the power coefficient. The incoming flow is modeled by an analytic equation test varies with time. The differential equations governing the system motion are solved by an implicit Newmark algorithm.     

增程式公交车动力系统设计及实例化研究

基于城市公交客车行驶特性的分析,对增程式城市公交客车动力系统进行了方案设计,并对动力总成零部件（增程器、驱动电机、动力电池组）进行了选型计算。结合增程式动力系统特点,开发了利用增程器延长续驶里程的增程式城市公交客车。在公交工况下对整车进行了组装试验,通过各项分析验证了增程式城市公交客车的节能与环保的特点,该动力系统可以满足整车预设的动力性和经济性要求。     

采用多目标进化算法的列车碰撞能量配置方案优化

为研究列车碰撞过程中车钩缓冲装置的阻抗力对列车碰撞能量吸收的影响,建立了列车纵向碰撞的动力学模型。以最大平均加速度、最大瞬时加速度、车体最大塑性变形量为优化目标,以车钩的阻抗力为优化参数,通过NSGA-Ⅱ算法得到了最优解集合,随后建立针对优化目标的综合评价体系并选取最优解。优化后列车的碰撞加速度相较优化前有所减小的原因是车辆两端界面力差值较小。     

Measurements of pollen grain dispersal in still air and stationary, near homogeneous, isotropic turbulence

The dispersal of ragweed, pine and corn pollen as well as polystyrene spheres in still air and stationary, near homogeneous, isotropic turbulence (HIT) was investigated using high-speed, digital inline holographic cinematography enabling Lagrangian tracking of the particles. Mean still air settling velocities were similar as reported literature values. Small discrepancies were most likely related to species/size differences and water content of the grains. Near-HIT was generated by loudspeakers mounted on the corners of a 40 cm³ chamber and the turbulent flow field at the center of the chamber was validated using stereoscopic Particle Image Velocimetry (PIV). Results showed near homogeneity and near isotropy with mean velocities 5–10 times smaller than the corresponding rms values of velocity fluctuations. The turbulent kinetic energy dissipation rate was determined from the PIV data sets and used to calculate the Kolmogorov scales and Taylor microscales. Experiments were carried out for two different loudspeaker amplifications corresponding to Taylor microscale Reynolds numbers, R_λ=144 and 162, respectively. The mean settling velocity in turbulent conditions was in all cases higher than the corresponding still air value, the difference becoming smaller as particle Stokes numbers increased. For the present conditions, the still air particle settling velocity was lower than the rms values of air fluctuating velocities. As a result, dispersion was dominated by inertia and for a given R_λ, particle fluctuating velocity autocorrelations fell more rapidly as the particle Stokes number decreased; corresponding particle diffusion coefficients also decreased. Transverse particle diffusion coefficients were lower than those in the direction of gravity in agreement with the continuity effect. Under the present range of experimental parameters, results showed that inertial particles (0.6<St<11) in highly turbulent conditions disperse more effectively than the air.     

零电压开关多谐振变换器在列车车载电网中的应用

介绍了一种应用于高速列车24 V车载电网的高效直流变换器,详述了其工作环境、设计原理、性能特点及结构组成,并对其核心电路半桥零电压开关多谐振( HB - ZVS - MRC)拓扑结构的工作原理进行了分析.并按要求制作产品,经调试后通过其专用测试台测试,现已在列车上正常运行.     

Halbach型空芯直线电动机绕组磁动势及牵引力计算

从电流产生的磁场出发,推导了三相绕组产生磁动势在空芯直线电动机中的分布,并对基波磁动势进行了具体分析,得到其行波表达式。又采用解析法对Halbach型直线电动机的牵引力进行了研究,得到牵引力计算简单有效的解析公式,并用ANSYS对解析公式进行了验证,证明了解析法的准确性。     

Chatter milling modeling of active magnetic bearing spindle in high-speed domain

A new dynamical modeling of Active Magnetic Bearing Spindle (AMBS) to identify machining stability of High Speed Milling (HSM) is presented. This original modeling includes all the minimum required parameters for stability analysis of AMBS machining. The stability diagram generated with this new model is compared to classical stability lobes theory. Thus, behavior's specificities are highlighted, especially the major importance of forced vibrations for AMBS. Then a sensitivity study shows impacts of several parameters of the controller. For example, gain adjustment shows improvements on stability. Side milling ramp test is used to quickly evaluate the stability. Finally, the simulation results are then validated by HSM cutting tests on a 5 axis machining center with AMBS.     

高速列车铝合金车体焊接可靠性

从焊接接头疲劳性、车体关键焊接残余应力入手,阐述了它们的测量方法、如何分析,最后提出提高接头疲劳性和降低焊接残余应力方法.     

基于高速铣削的铝合金6061表面粗糙度试验研究

采用正交试验法,在高速加工中心上对铝合金进行高速切削试验,研究机床的切削速度、进给速度、切削深度对加工表面粗糙度的影响规律,为企业生产提供可靠的依据.