基于声发射和小波分析的活塞环—缸套摩擦行为的试验研究

发布时间：2018-03-03 08:05

本文选题：活塞环—缸套　切入点：声发射　出处：《太原理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：活塞环—缸套系统是整个内燃机中最重要的部件,其效率和稳定性直接影响内燃机的动力性、经济性以及排放特性,因此,实现在线监测活塞环—缸套系统摩擦润滑状态对于降低燃油消耗,提高能源利用率,增加内燃机使用寿命等方面具有重要意义。声发射检测技术是一种先进的无损检测技术,已广泛应用于机构完整性的评估,构件的疲劳及裂纹检测,不同材料之间的摩擦润滑检测等。目前虽然已将声发射检测技术运用于内燃机状态监测的研究中,但是还缺少有效的试验研究方法在线测量和分析活塞环—缸套的摩擦行为,实现在发动机运行环境下对发动机润滑状态进行评估。本文以活塞环—缸套系统为研究对象,采用某公司1110II型和1125型立式单缸柴油机进行了一系列试验研究,对比分析不同转速和载荷下缸体表面的声发射信号特征,并通过在基础油中添加纳米级炭黑颗粒探究在多相润滑条件下活塞环—缸套系统的润滑特点。由于发动机表面具有众多激励源,为了从声发射信号中提取表征活塞环—缸体系统摩擦磨损过程的信号,采用小波降噪方法抑制由燃烧和阀门开关引起的强声发射干扰信号。由于冲程中部声发射信号和活塞速度密切相关,提出一种速度廓形约束自适应阈值降噪方法,同时提出用冲程中部的声发射信号包络平均值来表征活塞环—缸套系统的摩擦润滑状态。分析结果表明:采用小波多分辨率分析和自适应阈值降噪方法可以有效抑制大幅值的燃烧和阀门开关对信号的影响,从而得到活塞冲程中部主要由摩擦引起的声发射信号。摩擦引起的声发射信号随着发动机转速的增大而明显增大,在低转速下,声发射均值随着载荷的增大而降低,而在高转速下,载荷对声发射信号均值的影响较小。并且声发射信号可以有效的区分不同润滑油的摩擦特点,试验表明在添加了纳米级炭黑颗粒后使活塞冲程中部黏滞摩擦力下降,该研究方法和研究结果将有助于对新型纳米润滑过程的研发。使用改进的速度廓形约束阈值自适应选择降噪方法的计算结果明显优于传统硬阈值降噪方法。通过特征值分析,得到最优阈值和冲程中部声发射信号均值可以有效表征活塞环—缸套系统的润滑状态。
[Abstract]:The piston ring cylinder liner system is the most important component in the whole internal combustion engine. Its efficiency and stability directly affect the power, economy and emission characteristics of the internal combustion engine. The on-line monitoring of friction lubrication status of piston ring cylinder liner system is of great significance in reducing fuel consumption, improving energy utilization ratio, increasing the service life of internal combustion engine, etc. Acoustic emission testing technology is an advanced nondestructive testing technology. It has been widely used in mechanism integrity assessment, fatigue and crack detection of components, friction lubrication between different materials and so on. Although acoustic emission detection technology has been applied to the research of internal combustion engine condition monitoring, However, there is still a lack of effective experimental research method to measure and analyze the friction behavior of piston ring and cylinder liner on line, so as to evaluate the lubrication status of the engine in the engine running environment. In this paper, the piston ring cylinder liner system is taken as the research object. A series of experiments were carried out on 1110II and 1125 vertical single-cylinder diesel engines in a certain company. The characteristics of acoustic emission signals on the surface of cylinder body under different rotational speeds and loads were compared and analyzed. The lubrication characteristics of piston ring cylinder liner system under multiphase lubrication are investigated by adding nano-sized carbon black particles to the base oil. In order to extract signals from acoustic emission signals to characterize the friction and wear process of piston ring-cylinder system, Wavelet denoising method is used to suppress the strong acoustic emission (EAE) interference signal caused by combustion and valve switch. Because the AE signal in the middle stroke is closely related to the piston velocity, a speed profile constrained adaptive threshold de-noising method is proposed. At the same time, the envelope average of acoustic emission signal in the middle stroke is proposed to represent the friction lubrication state of piston ring cylinder liner system. The results show that wavelet multi-resolution analysis and adaptive threshold denoising method can be used to reduce noise effectively. Suppression of the effects of large value combustion and valve switches on the signal, The acoustic emission signal caused by friction in the middle of piston stroke is obtained. The acoustic emission signal caused by friction increases obviously with the increase of engine speed, and decreases with the increase of load at low speed. At high rotational speed, the load has little effect on the mean value of acoustic emission signal, and the acoustic emission signal can effectively distinguish the friction characteristics of different lubricating oil. The experimental results show that the viscous friction force in the middle of the piston stroke decreases with the addition of nano-sized carbon black particles. This research method and results will be helpful to the research and development of new nano lubricating process. The calculated results of adaptive selection noise reduction method using improved velocity profile constraint threshold are obviously better than those of traditional hard threshold noise reduction method. The optimal threshold and the mean value of the acoustic emission signal in the middle of stroke can effectively characterize the lubrication state of the piston ring cylinder liner system.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK403

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