汽车发动机曲轴纵向振动的研究

在发动机运转时,柔韧性和周期性的转矩对发动机轴的时刻有曲轴的作用扭转振动。轴系扭振能承受交变应力,但疲劳的积累就会造成曲轴的突然断裂。再加上较低的固有频率扭转振动,容易引起共鸣,进而引起大的噪音,它的其他部分磨损加剧,甚至可能发生再次断裂等严重损坏发动机曲轴事故。安装曲轴扭振减振器是曲轴扭振控制的主要措施,通过对发动机曲轴扭振分析,采用合理有效的方式来设计配套曲轴扭振减振器具有十分重要的意义。     

扭振减震器的压装方法

目前,汽车发动机曲轴皮带轮由刚性结构逐步改进为软性联接形式——曲轴扭振减震器,这样、既可以防止曲轴因额外负载(发电机、气泵)造成局部弯曲,又可克服发动机在输出力矩过程中造成的振动。所以扭振减震器是关系到整车车况性能的一个重要零件,对发动机寿命起着重要作用,扭振减震器的压装用量直接影响其性能,是扭振减震器加工过程中最关键工序。     

某航空发动机扭振减振器失效机理分析

为了探究某航空发动机曲轴扭振减振器的失效机理,采用有限元法对该发动机轴系进行了模态分析,并进行了试验验证;基于轴系扭纵耦合振动理论和谐响应分析计算了该轴系的轴向振动位移幅值;在此基础上对扭振减振器进行了失效分析。研究结果表明,因该航空发动机经常工作在过渡工况,引起轴系扭转共振和扭纵耦合振动,使得轴系轴向位移较大,轴系产生的轴向力是造成该扭振减振器失效的最主要原因。     

扭振对轴承受力及整机噪声影响的研究

针对曲轴扭转振动与整机辐射噪声问题,以某直列四缸发动机曲轴系统为研究对象,基于AVL Excite软件,在匹配扭振减振器(torsional vibration damper,TVD)与不匹配TVD两种情况下,采用弹性流体动力学模型轴承计算模型研究了曲轴扭振对机体所受激励与轴瓦表面压力分布的影响;并且在两种情况下,分别对曲轴扭振与车内噪声进行了试验测试,测试与主观评价表明,匹配TVD情况下曲轴扭振幅值降低,车内原有异响声明显改善。研究分析结果表明,扭振会使得曲轴模态频率附近范围内机体所受激励幅值增加,改变轴瓦表面载荷的幅值与分布规律,导致发动机乃至整车产生异响。     

曲轴平衡块配置对比应用研究

基于轻量化需求,通过对柴油发动机曲轴平衡率、扭振、结构强度、主轴承EHD计算,对比四平衡块和八平衡块两种配重方案曲轴的计算结果,结合台架试验对比,验证曲轴平衡块配置差异对发动机扭振、整机振动及可靠性的影响。验证结果表明,在同发动机配置下,四平衡块曲轴相对八平衡块曲轴,对应发动机扭振、整机振动差异不大,两种状态曲轴均通过可靠性试验考核。基于轻量化需求,可选择应用四平衡块配置曲轴。     

基于轴系动力学分析的全工况下减振器匹配优化设计

扭振是发动机正常工作时一种常见的振动形式,严重的扭振可能会引起发动机轴系的疲劳破坏.为了有效的降低发动机的扭振,提出了 一种基于柴油机轴系动力学分析的全工况下硅油减振器优化设计方法,以提高硅油减振器与发动机轴系的匹配效率.为了验证该方法的有效性,以某型六缸柴油发动机曲轴轴系为研究对象,建立考虑硅油减振器、皮带轮-正时齿...     

汽车发动机曲轴扭振减振器设计

随着我国经济的不断发展,汽车行业也逐渐兴起,不论是国家对于汽车设置的相关法律法规,还是人们对汽车舒适度的要求,都将更加严格。因此,对汽车发动机的噪声、振动频率和汽车行驶的平缓程度等都引起了人们的关注度,而汽车发动机的曲轴扭振是这些要求达到相应水平的不可缺少的一部分。本文将从对曲轴扭振减振器的概述、扭振减振器的发展现状以及汽车发动机曲轴扭振减振器的设计三个方面进行论述。     

汽油机曲轴系统扭振特性仿真与实验研究

为了研究汽油机曲轴系统扭振特性,以某新型1.8L汽油机为研究对象,首先应用多体动力学软件AVL-EXCITE Designer建立曲轴系统模型,利用三维制图软件得出系统的参数,分析曲轴系统的自由振动与强迫振动;应用CATIA软件和Spectra LAB软件得出减振器的转动惯量及固有频率,从而分析加装减振器后轴系的扭振特性。利用LMS Test.lab噪声振动测量系统进行扭振测试,并对试验测试结果与仿真结果进行对比分析,两者吻合得较好,证明本文提供的仿真方法能有效预测实际发动机轴系扭振情况。     

发动曲轴系统扭转振动建模与实测分析

建立了发动机曲轴系统扭转振动的集总参数模型,讨论集总参数模型中各个自由度转动惯量、刚度和阻尼系数的确定方法。利用集总参数模型计算分析曲轴系统的固有频率和在气缸压力的作用下曲轴前端的扭振。实验测试了一发动机曲轴系统的扭振,并与计算结果进行了对比分析。结果表明,曲轴系统的固有频率和曲轴前端扭振的计算结果与实测结果较为一致,证明了建立的模型和模型参数确定方法的正确性。曲轴扭振的建模方法和模型参数的确定方法可用于曲轴前端扭转减振器的设计。     

发动机变惯量曲轴系统1∶1∶1共振分岔分析

为了进一步对发动机实施节能抗振降噪优化处理,深入研究变惯量参数对内燃机曲轴系统扭振分岔特性的影响。利用描述发动机曲轴扭转振动的非线性动力学方程,针对转动频率、不平衡激励频率及固有频率之间关系为1:1:1时的情况,分别利用多尺度法得到并分析了描述系统稳态振动的平均方程。并以某型号发动机为例,得到了不同参数状态下,该发动机曲轴的扭振分岔情况,为其系统性优化设计提供理论依据。     

基于曲轴回转振动信号的多缸内燃机诊断研究

对机车柴油机的实测结果表明它与缸数少的内燃机有很大差别,本文针对多缸内燃机的特点提出了故障特征矢量的提取方法和基于子空间法模式识别的回转振动信号故障诊断方法。     

Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.     

Torsional system parameter identification of internal combustion engines under normal operation

For internal combustion engines, lumped-mass models of the crankshaft system are frequently used for torque estimation in control and diagnostic applications, such as cylinder balancing and misfire detection. Due to inherent model uncertainties and changing system dynamics it may be necessary to adapt the model parameters from time to time in order to preserve the required model accuracy. In this paper a frequency-domain method for on-line identification of the parameters describing the torsional dynamics of internal combustion engines is presented. In the proposed method, the engine is excited by adjusting the cylinder-wise injected fuel amounts, and the measured responses in torsional vibration frequency components are used for parameter estimation. As the fuel-injection adjustments can be determined in such a way that the net indicated torque is unaffected, the identification can be performed on-line without disturbing normal engine operation. The procedure can be applied to estimate the torsional stiffness and damping parameters of the flexible coupling connecting the engine and the load. In addition, the gains which describe how the cylinder-wise fuel injections affect the amplitudes of relevant torsional vibratory frequency components are obtained. The parameter identification method is successfully evaluated in full-scale engine tests on a 6.6 MW six-cylinder medium-speed common-rail diesel engine.     

Process analysis and test of manufacturing of sleeve spring-type torsional vibration damper

In diesel engines, engine torque fluctuation inevitably produces torsional vibration. A sleeve spring-type damper commonly is used to reduce this vibration. In this paper, closed form equations to predict the spring constant of a sleeve spring and the torsional characteristics of a torsional vibration damper are proposed for calculation of the stiffness of the damper. The equations were verified through finite element analysis (FEA) and experiments. In addition, the stability of the sleeve spring-type torsional vibration damper was verified in an analysis of the inner star and outer star (the core components of the damper). A two-roll bending process, proposed in this paper, was determined to be the most suitable for manufacture of the sleeve springs. A closed form equation to calculate the forming radius, taking account of the springback effect, was derived, and a FEA method used to analyze the elasto-plastic problem was verified through an analysis of a 90° bending process. The results of the analysis were in good agreement with the experiment. It is recommended that our proposed method, an advanced technique that can significantly reduce production costs, replace the conventional forming process.     

Effect of single and multi-channel electrodes application on EDM fast hole drilling performance

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. A sleeve spring damper is one such measure to reduce the torsional vibration. In this study, the closed form equations to predict the spring constant of a sleeve spring and the dynamic characteristics of the torsional vibration damper are proposed to calculate stiffness of the damper, and verified their availability through the finite element analysis. Our theoretical values are in good agreement with results obtained from finite element analysis and experiments. Results obtained from the derived equation enable designers to be more efficient.     

Application of novel polar representation method for monitoring minor engine condition variations

In an earlier study, a Noval Polar Presentation (NPP) method has been suggested to detect the engine combustion-related faults for medium-speed diesel engines. The earlier proposed NPP method basically used the signature of the crankshaft torsional vibration to identify the faulty cylinder accurately. However, the detection of only a large fault like the cylinder misfiring for the 2 typical engines (16-cylinder and 20-cylinder engines) has been demonstrated in the earlier study. Now the usefulness of the NPP method in detection of even a very small level of the engine combustion fault like an earlier or later opening of the fuel injection valve by just a few degrees has been presented here.     

内燃机轴系扭转振动综述

根据目前内燃机发展趋势,确定了内燃机振动在内燃机设计中的重要地位。然后总结出内燃机轴系振动的形式,同时评析了内燃机轴系振动的力学模型、分析计算方法及近年来的最新研究动态。     

某矿用车橡胶式扭振减振器的优化设计研究

针对某矿用车的传动轴断裂问题,通过对其发动机轴系扭振状况的研究,利用传统双扭摆模型求取了橡胶式扭振减振器基本参数,据此设计的减振器在理论上达到了减小轴系扭转振动的目的,可用于解决由发动机激励引起的传动轴扭振过大问题.     

Residual generation and statistical pattern recognition for engine misfire diagnostics

Methods for diagnosing misfire in internal combustion engines are presented in this paper. Crank-angle domain digital filters are used to extract features from the measured engine speed signal that are characteristic of misfire. Features for intermittent and continuous misfires are developed separately, since the engine speed responses for intermittent and continuous misfires are distinctly different. Also, the influence of crankshaft torsional vibration and repeatable measurement errors must be addressed differently in each case. The outputs from the digital filters serve as inputs to a pattern recognition network based on linear parametric classifiers. Experimental results from implementation on a Ford 4.6L V-8 engine are provided.     

硅油-橡胶复合阻尼式扭转减振器的设计方法及实验分析

降低发动机扭转振动的方法之一是加装曲轴扭转减振器。而传统的纯橡胶阻尼式曲轴扭转减振器由于其橡胶材料的滞后角普遍较小,因此不能在较宽的频域范围内提供适当的阻尼,导致其减振、隔振的效果较差。介绍了硅油-橡胶复合阻尼式扭转减振器的结构,建立了该扭转减振器的力学模型并提出了基于粒子群优化方法的设计参数优化方法。计算结果表明,优化后的系统中曲轴的扭转振动幅值降低,并通过实验验证了硅油-橡胶复合阻尼式扭转减振器控制发动机曲轴扭转振动的有效性。