发动机正时带传动系统动态特性建模与分析

建立了适用于任意布局形式的发动机正时带传动系统模型,通过数值方法求解出系统的动态响应,得到各轮的角位移波动、张紧臂的摆角波动和各带段张力等参数.考虑带与轮的啮合作用和张紧器的迟滞特性,分析了不同温度工况、不同加速度激励下系统的动态响应.结果表明:正时带将曲轴的角位移波动同步传动至从动轮,张紧臂摆角、各带段张力的波动与凸轮轴负载相关;同时,激励加速度与工况温度直接影响张紧臂的摆角.给出一个实例,验证提出的模型和计算方法的有效性.     

发动机前端附件驱动系统布局分析与计算

发动机前端附件驱动系统布局对其性能有重要的影响,探讨了发动机前端附件驱动系统布局设计的要点,给出了自动张紧器的张紧臂支点位置和张紧臂角度确定的原则和计算方法,分析了自动张紧器弹簧刚度、臂长等参数对多楔带张力的影响.提出了发动机前端附件驱动系统多楔带张力的计算方法,讨论了附件轮布置次序对发动机前端附件驱动系统稳态特性的影响,并提出了改善附件驱动系统性能的方法.最后,给出了一个实例,验证了提出的计算方法的有效性.     

OAD对发动机皮带传动系统动态特性及整车油耗的影响

介绍了0AD产生的背景、主要结构和工作原理,并利用simdrive软件对应用0AD带轮和普通钢轮两种状态的发动机前端轮系皮带传动系统进行动态模拟仿真计算,分析结果表明,有OAD的轮系张紧器角度波动、曲轴动态打滑率、最大皮带张力、压缩机最大径向载荷和皮带传动系统的功率损失都有明显降低。最后以吉利某款量产整车为例,研究使用0AD后的整车油耗表现。试验结果表明,使用OAD的整车在NEDC循环中油耗降低1.58%。     

基于转动振动控制的发动机前端附件带传动系统优化

针对由单根多楔带驱动的发动机前端附件皮带传动系统的转动振动问题,阐述了多带轮传动系统的转动振动模型及其求解方法.为了控制系统的转动振动,以自动张紧器关键参数为设计变量,以张力波动幅值、初始张力与张紧臂摆振幅度等指标最小为目标建立了3种优化模型.选用并实现了一种改进的坐标轮换方法以寻求最优解.对一个6缸发动机前端附件带传动系统进行了优化,通过对比不同优化方案的结果,指出了多目标优化的有效性.     

增压器放气阀物理模型建模方法研究

为了改善因排气波动造成放气阀不正常开启引起的天然气发动机在标定功率工况时出现严重的转矩波动情况,建立了增压器放气阀的瞬态模拟模型,对增压器放气阀受力情况进行理论分析,并利用GT-Power软件中的力学模块建立了增压器放气阀的压力-弹簧力平衡模型,应用模型对影响转矩波动的放气阀弹簧预紧力、刚度和系统阻尼进行分析,确定弹簧刚度是主要影响因素,并应用模型对弹簧刚度进行优化,给出具体的改进方案。应用改进后的放气阀在发动机台架上进行了验证试验,转矩波动由原来的70N.m降为19N.m,解决了发动机转矩波动问题。研究结果表明:增压器放气阀的瞬态模拟很好地预测出改进方案及效果,证明了瞬态模拟方法是可行的。     

摩擦式自动张紧器的设计与优化

以某型柴油机附件传动系统作为研究对象,分析附件传动系统主要零部件张紧器卡滞现象的产生机理。建立该摩擦式自动张紧器在静态激励下加载和卸载时库伦摩擦扭矩曲线的计算模型,分析张紧器摩擦力矩和弹簧力矩在卡滞现象中的作用。开展张紧器对照试验,通过张紧器在衰减弹簧刚度、较大弹簧刚度和高摩擦力矩情况下的运动表现,研究卡滞现象的原因。通过建立摩擦式自动张紧器的参数化模型,提供了优化张紧器弹簧刚度和摩擦力矩的设计途径,对防止摩擦式自动张紧器卡滞具有参考价值。     

柴油机前端附件驱动系统的优化设计

结合某新型发动机前端附件驱动系统的开发,介绍了OAD的结构、功能原理,并对该前端附件驱动系统进行了动态模拟仿真分析(分别进行了应用OAD带轮和普通发电机带轮两种状态的对比仿真),并最终在该发动机前端附件驱动系统上采用了OAD带轮来进行系统优化设计,从而提高系统性能。     

双馈异步风电机组机侧转速控制器的设计与仿真研究

双馈异步风力发电机组(DFIG)机侧(即转子侧)变流器作为其电控系统的核心控制部件,主要负责双馈感应电机的转速控制和发电机无功调节任务,但由于其具有非线性、强耦合等复杂特性,导致变流器的控制器设计十分困难。针对上述情况,提供一种DFIG转子侧变流器控制策略设计方法和控制参数优化方法,可通过调节转子侧电流大小实现双馈感应电机转速、无功的无静差调节;并以1.5 MW DFIG实际参数为模型,利用Simulink仿真软件对该控制策略进行仿真验证。研究结果表明：利用PI控制器可实现DFIG转速-转矩控制,发电机转子侧电流理论上可实现无静差跟踪。     

新型并网风电机组的动力学建模与仿真

为研究差动调速风电机组的动态特性,用弹簧-阻尼-质量系统建立了三轴动力学模型,采用Simulink软件进行仿真.以阶跃风载荷作为模型输入,得到了差动轮系的轮架轴、齿圈轴、太阳轮轴的转速、转矩以及功率,并进一步获得了转矩信号的频率分布.结果表明:新型机组能通过调速电机和差动轮系对风轮吸收的功率进行有效调节,其固有频率避开了转矩频率分量,不会发生共振.     

动铁式电磁调速执行器动态特性影响因素分析

为提高柴油机电磁式调速器的性能,揭示调速执行器动态特性参数的影响规律,采用数值模拟与试验相结合的方法,建立了动铁式电磁调速执行器的数值仿真模型,并通过试验验证了模型的精度,其最大误差为7%。通过数值模拟研究分析了电磁调速执行器的动态工作特性及脉冲宽度调制(pulse width modulation,PWM)频率、弹簧预紧力、弹簧刚度、负载大小、线圈匝数及导磁材料等参数对执行器动态特性的影响。结果表明:初始阶段适宜采用大占空比或满占空比来加快执行器的动态输出速度,以较小的占空比来维持满行程的输出以提高执行器的动态回位速度;提升执行器的位移-力的水平特性有助于提高执行器行程输出的线性度;此外,发现PWM频率、弹簧预紧力、弹簧刚度、负载大小、线圈匝数及导磁材料等参数对执行器动态特性均具有重要影响。     

柴油机前端附件驱动系统动态模拟仿真分析

以SIMDRIVE作为动态模拟软件,通过对某型柴油机前端附件驱动系统(FEAD系统)进行动态模拟仿真,详细计算了该柴油机附件驱动系统在各种极限工况下的打滑率、皮带的抖动、张紧轮的摆幅及各个附件带轮上的径向载荷,通过对计算结果分析,得出该附件驱动系统完全满足设计要求.     

某发动机前端轮系张紧器异响分析及改进

针对某发动机前端轮系张紧器在特定转速下的异响问题,通过仿真与试验,分析异响产生原因并进行结构优化.对张紧器进行模态仿真分析,发现张紧器螺旋弹簧的一阶轴向伸缩变形模态频率为347 Hz,与理论计算的异响转速相关频率(344 Hz)非常接近.拆解发生异响的张紧器,发现张紧器第二圈弹簧与壳体底部卡槽凸台发生干涉,产生摩擦噪声...     

汽轮发电机组轴系扭转振动对机械参数的敏感性分析

针对某300MW汽轮发电机组模型,分析了扭振固有频率和振型对汽轮发电机组轴系转动惯量和刚度的敏感性。计算结果表明:无论是轴系整体转动惯量或刚度、还是局部转动惯量或刚度的变化,都会对扭振特性产生明显的影响;局部转动惯量或刚度的改变对特定阶的扭振的影响虽然不及整体转动惯量和刚度变化的影响大,但也十分显著;对特定振型贡献较大的轴段对此阶轴系扭振影响较大,在振型图上表示为此阶振型在这一轴段处的斜率较大;在实际中可以通过改变轴系局部结构,使某阶扭振固有频率避开特定的值,从而达到调频的目的,而在对汽轮发电机组轴系扭振研究的建模过程中,要精确确定扭振特性敏感性较高的那些部位的机械参数。图4表2参8     

Sensitivity analysis of torsional vibration behavior of the shafting of a turbo generator set to changes of its mechanical parameters

Aiming at a 300 MW turbo-generator model, the sensitivity of natural torsional frequencies and modes of torsional vibration (TV) to the rotational inertia and stiffness of the turbo-generator were analyzed. Calculation results show that the variation of the rotational inertia or stiffness either of the rotor system as a whole (namely shafting) or only locally may both remarkably influence the TV characteristics of the rotor. The influence of localized variation is still notable although it is not as great as that of the rotor as a whole. The segments on the shafting, which contribute more to a certain mode of vibration, have a greater influence on the pertaining order of TV. Compared with the modal shape, a larger slope can be observed at these sections of the rotor for the particular mode. Thus, frequencies can be modulated by modifying the local construction of the rotor to make the natural TV frequency of a certain order avoid some specific value, herewith arriving at the objective of tuning. Therefore, it is very important, in the course of modeling for the purpose of studying the TV of the shafting of a turbo-set, to accurately determine the structural parameters of parts that have a relatively sensitive effect on the TV behavior. __________ Translated from Journal of Power Engineering, 2005, 25(4): 462–465, 482 [译自: 动力工程]     

Maximum Permissible Slip for Synchronizing Salient-Pole Synchronous Motors

The paper presents a method for determining the maximum permissible slip for synchronization of a salient-pole synchronous motor using machine, load and system parameters. An exact differential equation of motion of the salient-pole rotor during the synchronizing period is derived and then solved by means of a digital computer program using a fourth-order Runge-Kutta method. The synchronizing criterion involves two factors: the displacement angle must decrease, and this angle must not exceed 540 electrical degrees. Curves showing the relationship between load torque and maximum permissible slip with load inertia as a parameter are shown for a given motor. These results are compared with test data on the actual machine.     

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

In this study, an innovative concept for load reduction on the two‐bladed Skywind 3.4 MW prototype is presented. The load reduction system consists of a flexible coupling between the hub mount, carrying the drive train components including the hub assembly, and a nacelle carrier supported by the yaw bearing. This paper intends to assess the impact of introducing a flexible hub connection on the system dynamics and the aero‐elastic response to aerodynamic load imbalances. In order to limit the rotational joint motion, a cardanic spring‐damper element is introduced between the hub mount and the nacelle carrier flange, which affects the system response and the loads. A parameter variation of the stiffness and damping of the connecting spring‐damper element has been performed in the multi‐body simulation solver Simpack. A deterministic, vertically sheared wind field is applied to induce a periodic aerodynamic imbalance on the rotor. The aero‐structural load reduction mechanisms of the coupled system are thereby identified. It is shown that the fatigue loads on the blades and the turbine support structure are reduced significantly. For a very low structural coupling, however, the corresponding rotational deflections of the hub mount exceed the design limit of operation. The analysis of the interaction between the hub mount motion and the blade aerodynamics in a transient inflow environment indicates a reduction of the angle of attack amplitudes and the corresponding fluctuations of the blade loading. Hence, it can be concluded that load reduction is achieved by a combination of reduced structural coupling and a mitigation of aerodynamic load imbalances. Copyright © 2016 John Wiley & Sons, Ltd.     

Dynamic behavior and transient stability analysis of fixed speed wind turbines

This paper analytically investigates the dynamic behavior of fixed speed wind turbines (FSWTs) under wind speed fluctuations and system disturbances, and identifies the nature of transient instability and system variables involved in the instability. The nature of transient instability in FSWT is not similar to synchronous generators in which the cause of instability is rotor angle instability. In this paper, the study of dynamic behavior includes modal and sensitivity analysis, dynamic behavior analysis under wind speed fluctuation, eigenvalue tracking, and using it to characterize the instability mode, and investigating possible outcomes of instability. The results of theoretical studies are verified by time domain simulations. It is found that the instability occurs due to the mechanical dynamics and the instability is closely related to increasing of generator slip.