Condition monitoring of aircraft by quantitative filter debris analysis

Various condition monitoring techniques are used collectively to monitor the health of aircraft engines and transmission, a concept known as Integrated Health Monitoring (IHM). A well-established quantitative technique is Aircraft Oil Analysis (AOA), in which spectroscopic techniques such as Rotating Disk Electrode Atomic Emission Spectroscopy (RDE-AES) are employed to analyse periodic oil samples for wear debris. Usually, no sample preparation is undertaken, as the oil sample containing both dissolved and suspended metallic wear debris is analysed directly. AOA works well for oil-lubricated systems with relatively coarse filtration that allow circulation of the debris and its subsequent abrasive contact with moving components. To avoid this secondary wear, finer filtration is employed on both new and older aircraft. Less wear debris, and thus information, is available in the oil. A technique that quantitatively analyses the wear debris caught on the filter has been developed and is termed Quantitative Filter Debris Analysis (QFDA). Actual oil filters from CF88 Challenger ALF 502L-2C and Hornet F404 engines were obtained in sequence, when possible, prepared by the developed procedure, and analysed with AOA instrumentation. With sufficient results, both normal and abnormal levels of wear rates emerged, as has been recorded and used for AOA. Moreover, trending of the data for sequential samples has demonstrated the capability of GFDA for condition monitoring.     

Influence of temperature on cam-tappet lubrication in an internal combustion engine

The transient thermo-elastohydrodynamic (TEHL) lubrication simulation and isothermal elastohydrodynamic (EHL) simulation were performed on the exhausting camtappet friction pair of an internal combustion engine. Although by employing the two models the center pressure, the thickness of the lubricant film and friction coefficient obtained were similar in the changing trend during a rotating cycle, the parameters make a great difference, especially for the thickness of the lubricant film; the TEHL was four times thicker than the EHL. These results show that the temperature should not be neglected in the study of the lubrication of cam-tappet pairs. __________ Translated from Tribology, 2006, 26(4): 362–366 [译自: 摩擦学学报]     

内燃机活塞优化设计及分析

基于活塞的结构和工作原理,运用Pro Tools M-Powered软件建立了有限元模型。依托该模型,对活塞的负荷边界、应力和位移进行了分析,最终实现对活塞的优化设计。     

Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.     

基于案例的SL1126内燃机方案设计

通过深入研究SL1126内燃机结构特征,获得了该类产品结构设计知识,对产品的设计任务进行了抽象和分类。通过基于案例的设计(case-based design．CBD)与工程CAD中的模板技术相结合,提出了一套对产品整机参数化设计具有普遍指导意义的方案。     

Experimental methods for measuring the oil-film thickness between the piston-rings and cylinder-wall of internal combustion engines

Computer models of the lubrication of piston-rings in internal combustion engines normally present an estimate of the minimum oil-film thickness between ring and cylinder wall as a function of crank angle. As a consequence, experimental measurements of film thickness play a critical role in the verification of theoretical models of piston-ring lubrication. A review is presented of the wide range of techniques that have been used to measure this important variable. The strengths and weaknesses of particular techniques are identified and a number of ways in which the techniques could be developed further are proposed     

柴油机滑动轴承热流体动力润滑仿真研究

根据径向滑动轴承热流体动力润滑理论,基于JFO理论提出的质量守恒边界条件,建立同时包含油膜完整区和空 穴压力变化的单缸柴油机滑动轴承热流体动力润滑模型,采用有限差分法求解模型方程,仿真分析滑动轴承的油膜厚度、油膜压力、润滑油流量和温度等参数对润滑性能的影响,分析内燃机滑动轴承润滑特性,为轴承润滑可靠性设计提供一定的理论依据.     

内燃机气门间隙快速调整法的探究

重点介绍了内燃机在使用和维护过程中气门间隙的调整方法,通过对常用的气门间隙调整方法——＂逐缸调整法＂和＂双排不进＂法进行比较分析,并根据长期的实践实验证明,此方法是一种更为快速、简便、准确的调整方法。     

基于SolidWorks的内燃机构造与运动仿真

基于对内燃机构造和工作原理的研究,通过SolidWorks软件,利用其提供的零件建模、实体装配、工程图及动画制作的功能,将内燃机结构如气缸体、曲柄连杆机构、配气机构等结构进行三维参数化设计,完成内燃机基本机构的建模、装配和零件图的出图以及利用COSMOSMotion进行内燃机运动仿真。     

Surface anisotropy for monitoring the wear of IC engine cylinders

The present work proposes a methodology for monitoring the wear of internal combustion engine cylinders. This could be useful in calculating the time at which maintenance should be done on such a tribosystem or in determining its lifetime. On the basis of experimental data obtained using a friction—wear simulator, and through the determination of certain standardised and non‐standardised micro‐geometric parameters of the cylinder surface that change with respect to operating time, it is shown that the characteristic that exhibits the most variation is the cylinder surface anisotropy. This factor participates to a large degree in the partial hydrodynamic lubrication mechanism of the reciprocating piston ring system and, as it is associated with the stage of wear, better expresses the characteristics of the cylinder's worn surface. As a consequence, by prescribing a limit for the maximum acceptable anisotropy as a basic criterion, the ultimate tolerable stage of wear is controlled simultaneously and vice versa.     

Effects of lubricant viscosity on the mixed lubrication of a piston ring pack in an internal combustion engine

A theoretical analysis is presented of the mixed lubrication of a piston ring pack. The analysis comprises Patir and Cheng's average flow model and Greenwood and Tripp's asperity interaction model, and is developed to consider the shear thinning effect of a non‐Newtonian fluid, multigrade lubricant. The friction characteristics of the piston ring pack for both monograde and multigrade lubricants are investigated. It is found that a decrease in the lubricant viscosity is effective in reducing the friction loss, although this increases the boundary friction at the beginning of the expansion stroke. The friction characteristics are markedly affected by the shear thinning effect when multigrade lubricants are used.     

A comparative evaluation of RPD and ferrographic diagnostic methods for turbine engine lubricant samples

A rotary particle depositor (RPD) was evaluated and compared with analytical (AF) and direct reading (DR) ferrographs to ascertain if the RPD is better suited for analysis of wear debris in turbine engine lubricant samples than the AF and DR. Sieved iron particles were added to synthetic turbine engine lubricants at various concentrations and were analysed by RPD and ferrographic methods and compared. Lubricant samples containing a fine test dust were also analysed by RPD and AF to determine the effectiveness of the RPD's centripetal acceleration and the AF's gravity flow in eliminating non-ferrous contamination from the sample. Finally, comparisons were made between actual lubricant samples from a turbine engine simulator analysed by RPD and ferrographic methods. For lubricant samples with relatively small amounts of non-ferrous contamination or samples where non-ferrous particles are important in machine health condition assessment, the AF and DR ferrographs are equal or superior to RPD for lubricant analyses. For samples with high levels of non-ferrous contamination, the RPD is superior in eliminating unwanted non-magnetic particles and permitting a less obstructed view of the important ferrous wear debris particles.     

发动机状态实时监测系统的研制

发动机的转速、机油压力、机油温度、冷却水温度、油耗及振动是保证发动机安全、可靠运行的重要工况参数,介绍了以工业控制计算机为核心的发动机状态实时监测系统的构成及软、硬件设计技术。     

内燃机优化设计研究现状与展望

综述了内燃机优化设计理论的研究和应用现状、进展。着重讨论内燃机主要零部件、工作过程以及内燃机动力学、摩擦学等方面的优化设计研究工作，展望了内燃机优化设计理论和应用的发展动向及若干重要问题。     

Analytical approach to wear rate determination for internal combustion engine condition monitoring based on oil analysis

Wear has important, negative effects on the functioning of engine parts. Additionally, this situation is very difficult to evaluate accurately in oil analysis for engine condition monitoring. Original Equipment Manufacturers (OEM), lubricant suppliers and oil analysis laboratories provide specific guidelines for wear metal concentrations. These limits provide good general guidelines for interpreting oil analysis data, but do not take into account common factors that influence the concentration of wear debris and contaminants in an oil sample. These factors involve oil consumption, fresh oil additions, etc., and particular features such as engine age, type of service, environmental conditions, etc.In this paper, an analytical approach to enable a more accurate wear determination from engine oil samples is developed. The above factors are taken into account and an improved maintenance program for internal combustion engines based on oil analysis is developed.     

中、小型内燃机电站噪声频谱试验研究及降噪措施

通过试验研究确定内燃机电站噪声频谱,找出主要的噪声来源,采取相应降噪措施,有效的降低了内燃机电站的噪声。     

Henry's constants for ethanol,iso‐octane and gasoline absorption in engine lubricants

Henry's constants for hydrous ethanol, iso‐octane and gasoline absorption in engine lubricants were determined using gas chromatography. Samples of synthetic SAE 5 W30, synthetic SAE 5 W40, semi‐synthetic SAE 15 W40, mineral SAE 15 W40 and mineral SAE 25 W60 oil were used in the experiments. For all lubricants tested, typical molecular weights were considered, ranging from 500 to 5000 kg/kmol. The results show that, for any lubricant, Henry's constant for hydrous ethanol is about 2.2 times higher than that of gasoline, and about 4.3 times higher than that of iso‐octane. Decreasing Henry's constant was observed with increasing lubricant molecular weight, regardless of the fuel type. Copyright © 2014 John Wiley & Sons, Ltd.     

内燃机机械噪声与燃烧噪声识别

针对内燃机噪声识别问题,建立数学模型并编制相应的程序,实现燃烧噪声和机械噪声的频谱分离和A计权声功率级计算.以单缸四冲程汽油机为例,通过构造包含干扰噪声的理论算例仿真识别,验证了程序的准确性和实用性.识别结果表明,分离前/后的燃烧噪声和机械噪声的频谱吻合良好,声功率级误差很小.     

内燃机转速波动信号的测量方法及其应用研究

提出了两种测量内燃机转速波动信号的简单方法,探讨了提高测量精度的途径,介绍了用于内燃机故障诊断的一些测量和应用实例,给出了相应的特征提取和故障识别方法。     

边坡内部位移监测系统

随着我国对煤炭资源大力开采,矿山排土场的排弃量日渐增大,排土场边坡失稳问题频繁发生.实施边坡内部位移监测是保证矿山安全生产及运输的重要手段和措施.目前尚没有广泛应用的长期监测边坡内部岩土体位移的专用仪器.介绍了一种边坡内部位移监测系统,采用电磁信号发射及信号测距的思想进行设计,可以实现对矿山排土场边坡的内部岩土体动态运移情况进行监测.最终实现数字化、自动化、可靠性高,并能实施长期监测,具有预警功能的监测系统.