连续悬臂梁动力吸振器的模型研究

针对吸振器动力参数固定不可变或仅能产生离散变化的局限性问题,在连续悬臂梁的基础上通过增加滑动质量块的方式,设计了一种新型的参数可连续变化的悬臂梁吸振装置,并对其进行了共振频率、效果试验分析.为提高主体振动控制的效果又对参数进行了优化分析.结果表明,该装置对受固定频率简谐激励的主体结构进行动力吸振可行有效,动力参数连续可调.     

动力总成动力吸振器特性研究

采用合适的动力吸振器对汽车动力总成的弯曲共振有较好的抑制作用,动力总成工况复杂,吸振器选择不合理反而可能适得其反。通过对动力总成吸振器进行试验研究,分析了动力总成吸振器的温度特性和激励特性,并应用于动力吸振器设计,成功解决了某车型由于动力总成弯曲共振导致的车内振动噪声大的问题。     

多维耦合双层隔振系统动态吸振器吸振特性

建立了针对多自由度动态吸振器作用于多维耦合双层隔振系统上的六自由度动力学模型,给出了系统的量纲为1参数控制方程和系统力传递率表达式.基于此,研究了吸振器固有频率比、耗散系数、安装距离、安装跨度、质量比和转动惯量比对吸振器吸振特性(系统力传递率)的影响;并结合对系统模态能量分布情况的分析,阐明了吸振器的吸振机理以及最优参数取得条件;最后,结合内燃动车动力包这一工程对象,给出了其散热器子系统充当双层隔振系统吸振器用于提高系统在发动机停机工况的隔振性能应用实例.研究结果对于双层隔振系统多自由度吸振器参数的设计具有指导意义.     

叉车前桥动力吸振器的有限元及试验分析

针对某型号叉车前桥的振动特性,设计了一种以橡胶为弹性阻尼元件的被动式动力吸振器,为便于预测吸振器力学特性,建立了以橡胶为弹性阻尼元件的该种吸振器的有限元模型,该有限元模型的分析结果与实际测试的频响曲线吻合,在该吸振器安装在某型叉车上之后,前桥处的振动幅值比未安装吸振器前的振动值明显减小.     

自由活塞式斯特林制冷机吸振器部件优化设计

对自由活塞式斯特林制冷机的吸振器部件进行理论仿真分析和结构优化设计。结构优化设计主要从吸振器的配重块布局、固定螺母配置、阻尼特性等3方面开展。通过调整配重块的非中心对称分布，改善吸振器部件的1、2阶模态偏差，避免吸振器部件的翻转运动对吸振性能产生影响；通过对吸振器表面喷涂阻尼材料，改善其阻尼特性，提升吸振效果。开展整机振动测试，测试结果表明优化后的整机振动幅值为优化前的1/5，优化设计效果明显。     

某柴油机曲轴扭振合成应力控制计算分析

针对某新型柴油机轴系扭振计算中曲轴扭振附加应力过大问题,对激励进行分析并开展扭转振动计算;尝试采取不同途径消减过大扭振合成应力。得到如下结论:当今柴油机强化指标不断提高,而CCS推荐的气体激励简谐分量幅值相对偏小,从安全角度出发,扭转振动计算时应按照柴油机厂提供的激励数据进行。共振区域的过大振动应力可通过确定主要贡献的谐次分量,调整节点位置部件参数的方法来消减;非共振区域的过大振动属正常的振动响应,可通过增强曲轴的抗扭振疲劳强度来适应,但其可行性应综合考虑柴油机设计因素。     

风力机叶片两点激励疲劳试验系统设计与特性分析

基于电驱惯性式激振装置,采用能量法计算能耗及动力参数,匹配叶片试验弯矩载荷,设计出一种两点激励共振型风力机叶片疲劳试验系统。建立两点激励加载试验系统的动力学模型,并结合三相永磁同步电机的在d-q坐标系下的状态方程,联合构建系统的机电耦合方程,利用Matlab软件建立仿真模型进行数值仿真分析,得到系统耦合振动过程基本规律。构建两点激振惯性加载系统进行兆瓦级风力机叶片加载试验,验证数学模型及仿真分析的结果,为叶片疲劳试验系统及控制算法设计提供指导。     

两个与柴油机轴系滚振问题有关的实例——兼与陈之炎同志商榷

读了陈之炎同志“论柴油机轴系的非主简谐滚振”一文后,获益甚多,尤其该文在谈到曲柄端面图非均匀排列的柴油机时指出,在这种情况下非主简谐的干扰力矩并不等于零,从而具备了激励非主简谐滚振的条件这一段论述,使笔者意识到自己在“商榷”一文中提出的“只要柴油机装置在其转速范围内出现滚振,几乎无例外地都是柴油机最低次主简谐的滚振,不会是非主简谐的滚振”这一看法存在局限性。事实上,笔者这种看法只是分析了常见的曲柄均匀排列(对单排多缸机则是发火均匀,下同)的发动机提出的,没有顾及到比较少见的曲柄非均匀排列(对单排多缸机则是发火不均匀,下同)的发动机。对提出这种看法时的疏漏笔者深表歉意。因此较为确切的说法应该是:对常见的曲柄均匀排列(不能满足单列式发火均匀者除外)的柴油机轴系,只要在其工作转速范围内出现滚振,几乎无例外地都是柴油机最低次主简谐的滚振,不会是非主简谐的滚振。对曲柄非均匀排列的柴油机轴系,笔者十分同意陈之     

拉索式小型风力发电机塔架结构吸振器的研发

风力发电机塔架结构的自然频率与风轮的工作频率(风叶的通过频率)相近时,将发生共振,导致风力发电机无法正常工作。文章基于动力吸振原理,建立了拉索式小型风力发电机塔架结构等效振动模型,再以6kW级拉索式小型风力发电机塔架结构的缩小模型为对象制作吸振器,用理论与试验验证吸振器的有效性。试验结果表明,吸振器能够有效减少塔架结构共振频域内的振动。     

簧片滑油型扭振减振器设计方法及验证

介绍了一种簧片滑油型扭振减振器设计方法。首先使用简化模型通过动力吸振理论的最佳定调比和最佳阻尼比针对轴系扭振最主要谐次进行控制,初步确定减振器的减振特性参数;再使用详细模型通过轴系扭振计算进一步调整特性参数,使扭振控制效果达到最优。然后根据参数设计结果开展结构设计,主要介绍了扭转刚度和阻尼系数两个特性参数相关的结构设计方法。最后进行设计检验。将该方法应用到HND 622V20CR柴油机的减振器设计中,显示:所设计的簧片滑油型扭振减振器与原扭振减振器相比减振效果优势明显。     

Numerically assisted analysis of flat and corrugated plate solar collectors thermal performances

The paper presents the results of experimentally supported numerical analysis performed in order to investigate the possibilities to improve the thermal efficiency of plate solar collectors. Different numerical models were developed in order to asses the influence of design and operating parameters such as bond conductance between absorber plate and tube, tube diameter, glass cover to absorber plate distance, optical properties of absorber and flow rate on thermal efficiency of collectors. Following the results, two designs of collector without tubes, with parallel flat and corrugated absorber plates of chevron type, is further considered and shown to be an effective way to increase the thermal efficiency of solar energy conversion beyond that of commercial glazed and unglazed solar water heaters. Based on the results, the guidelines for design of a new collector prototype consisting of chevron type corrugated plates normally used in plate heat exchangers are provided.     

利用结构动态特性修改及灵敏度分析减小机体振动

利用机体试验模态分析结果建立了用于机体结构动态特性分析的有限元模型，分析了机体振动模态及结构刚度的分布变化规律，将矩阵摄动理论及灵敏度分析方法应用于机体动态特性的修改之中，确定影响机体各阶动态特性的结构参数及其位置，优化结构动态特性，使得针对某一频率的减振降噪成为可能，文中对机体结构动态设计的几个主要步骤进行了探讨。     

太阳能集热组合墙系统的耦合传热与流动分析

针对太阳能集热组合墙系统，分析了太阳辐射及环境温度变化时，组合墙内传热与流动变化。太阳能集热组合墙系统中，多孔介质起半透明隔热体和蓄热体的作用。多孔介质的空隙率、粒径大小对系统的采暖效果影响较大。     

Computer modeling and experimental validation of a building-integrated photovoltaic and water heating system

A dynamic simulation model of a building-integrated photovoltaic and water heating system is introduced in this paper. The numerical model was developed based on the finite difference control volume approach. The integrated use of energy balance and fluid flow analysis allows the prediction of the system dynamic behavior under external excitations such as changes in weather, water consumption and make-up conditions. The validity of the modeling approach was demonstrated by comparing its predicted operating temperature changes and system daily efficiencies with the measured data acquired from an experimental rig at the City University of Hong Kong. The predictions from the model show good compliance with the experimental measurements.     

Parametric study of water vapor absorption into a constrained thin film of lithium bromide solution

This study presents a two-dimensional numerical simulation of a membrane-based absorber. A comprehensive parametric study is performed to quantify the influence of different operational and geometrical parameters such as solution film thickness, velocity, and concentration, cooling water temperature, and membrane thickness, pore size, and porosity on the absorption rate. In addition, the effect of membrane surface roughness on the absorption rate is investigated. The results indicate that the most critical parameters that affect the absorption rate are the solution film thickness and velocity. While it is impossible to control these parameters independently in a conventional absorber, they can be readily adjusted in the proposed membrane-based absorber to achieve the optimal performance. The simulation results suggest up to 3-fold enhancement in the absorption rate when a solution film thickness in the range of 50–100 μm is used.     

湿法烟气脱硫吸收塔烟气流场数值模拟研究

介绍了湿法烟气脱硫系统吸收塔的结构特点,并对某项目燃用设计煤种时不同负荷条件下吸收塔内烟气流场的分布进行了模拟研究和分析。验证了该项目吸收塔设计的合理性及实际运行时对负荷的适应性,为吸收塔的优化设计和稳定运行奠定了理论基础。     

Exergetic optimization of flat plate solar collectors

In this paper, an exergetic optimization of flat plate solar collectors is developed to determine the optimal performance and design parameters of these solar to thermal energy conversion systems. A detailed energy and exergy analysis is carried out for evaluating the thermal and optical performance, exergy flows and losses as well as exergetic efficiency for a typical flat plate solar collector under given operating conditions. In this analysis, the following geometric and operating parameters are considered as variables: the absorber plate area, dimensions of solar collector, pipes' diameter, mass flow rate, fluid inlet, outlet temperature, the overall loss coefficient, etc. A simulation program is developed for the thermal and exergetic calculations. The results of this computational program are in good agreement with the experimental measurements noted in the previous literature. Finally, the exergetic optimization has been carried out under given design and operating conditions and the optimum values of the mass flow rate, the absorber plate area and the maximum exergy efficiency have been found. Thus, more accurate results and beneficial applications of the exergy method in the design of solar collectors have been obtained.     

Performance and optimum design analysis of an absorber plate fin using recto-trapezoidal profile

This paper establishes a new profile, viz. recto-trapezoidal (RT) of an absorber plate fin on the basis of ease of fabrication as well as augmentation of heat transfer rate per unit fin volume. An analytical model has been developed for evaluating the thermal performance and optimum dimensions of an absorber plate fin using this typical profile. The present study is equally suitable for an absorber plate fin having a rectangular, trapezoidal or triangular profile also with consideration of their respective geometrical parameters. The optimization of the RT profile has been cast in a generalized form either by maximizing heat transfer rate for a given fin volume or by minimizing fin volume for a given heat transfer duty. From the optimum design analysis, significant results have been noticed when an additional constraint is imposed with the fin volume. Under this design condition, it may also be highlighted that for an optimal circumstance, the heat transfer rate through a RT profile absorber plate fin is greater than a trapezoidal or triangular profile for the same fin volume. However, this observation may be restricted to the limited values of fin volume only. The optimum design analysis for the RT profiled absorber plate fin has also been studied under the different design constants. Finally, for the variation of all the design variables, optimum design curves have been generated for a wide range of thermo-geometric parameters.     

Experimental and numerical study on the combustion limiting characteristics and design margin of a marine diesel engine

In this paper, a working-process simulation model was established, and the characteristics regarding the diesel engine maximum output power were analyzed under different limiting parameters. The design margin of the marine diesel engine is obtained through numerical and experimental study. Then, the simulation model and single cylinder diesel engine test were used to investigate the theoretical determination method of limiting characteristic lines and design margin area. It can be found that using least-square method to fit the calculation results can achieve quantitative analysis of limiting characteristics, and then the design margin area can be confirmed. The analysis results show that the maximum output power of the diesel engine is limited by in-cylinder pressure, turbine speed and exhaust temperature. The limiting parameters of maximum output power are different at different speeds, and the trend with speed of maximum output power are also different under different limiting parameters. Furthermore, the analysis of the operating area shows that the margin of the marine diesel engine at rated speed is about 27%, and there is a large design margin when operating at high speed.