柴油机排气消声器的设计选型

柴油机运转过程中的噪声会严重污染人类的生存环境 ,其中排气噪声是柴油机的主要噪声源。因此 ,控制排气噪声是降低柴油机整机噪声、改善环境的重要措施。1　排气噪声产生机理柴油机排气噪声是指当排气门打开出现缝隙时 ,废气以脉冲形式从缝隙中冲出而形成 ,其能量大、频谱复杂、频率可达上万Ｈｚ。排气噪声主要有基频噪声、涡流噪声、气柱共振噪声等。(1)基频噪声在柴油机排气门刚开启时 ,仍具有较高压力的气体从气缸内高速喷出 ,气流冲击到排气道内气门附近的气体上 ,使其产生压力剧变而形成压力波 ,压力波动随排气门的周期性开闭而呈周期…     

ESCS在摩托车消声器设计中的应用

借助新开发的排气系统计算模拟程序(简称ESCS）的分析功能．确定催化转化器在消声器中的最佳布置并分析了加装排气净化消声器后，压力波对原机性能的影响，使新研制出的排气净化消声器具备良好的排气动力效应。试验结果表明，在加装了排气净化消声器后，对摩托车的动力经济性及噪声没有明显的影响，对CO、HC、NOx的净化率都在50％以上。     

一种非对称异步排气涡旋压缩机的数值模拟研究

传统非对称涡旋压缩机的2组工作腔内容积比不相等,会导致压缩时的压力不对称现象严重,同时使得排气损失和排气脉动增加。为此,针对一种等内容积比的非对称异步排气涡旋压缩机进行了数值模拟研究。首先,建立了非对称涡旋压缩机的几何模型,对非对称异步排气涡旋结构的构造原理进行了公式推导,分析了其工作腔的容积变化状况;然后,对该结构的流体域进行了结构化网格划分,并进行了瞬态数值模拟,研究了腔内压力场、温度场、速度场的分布特性;最后,在相同条件下,将该非对称异步排气涡旋压缩机与传统非对称涡旋压缩机进行了性能对比分析。研究结果表明：该非对称异步排气结构的腔内流场均呈非对称分布,同一工作腔的压力场较为均匀,2组工作腔的排气压差在2%以内,但同一工作腔的温度场和速度场受径向间隙影响,其不均匀程度较大;经性能对比,该结构的排气压力损失仅为6.6%,排气温度降低了8.1 K,排气时的脉动强度降低了34.9%,涡旋压缩机排气过程更加稳定。     

采用无凸轮式排气型线的发动机排气性能研究

为探究无凸轮式排气型线对某发动机排气性能的影响，建立某发动机一维仿真模型，在转速1200r/min，进气压力137kPa的工况条件下，对中低转速、中低负荷工况点下采用无凸轮式排气型线后发动机的排气性能进行了数值模拟。仿真结果表明：与原机相比，采用无凸轮式排气型线，排气时面值增大，总排气损失最小时所对应的排气早开角度减小；当缸内残余废气系数最低时，充量系数最大，正向排气量与循环进气量达到最大；采用无凸轮式排气型线，气门开启持续期缩短，排气性能得到改善。     

压缩机性能试验装置排气压力自动调节系统的设计与研究

压缩机性能检测过程中,其排气压力的控制精度直接影响测量数据的准确性.国家标准试验方法中对其排气压力控制最大波动范围在±0.5%以内,本文根据压缩机性能试验装置的要求,针对被控量的特性和实际运行情况,利用飞升曲线法、临界比例法得出排气压力控制系统的模型算式、模型参数.从控制理论上对排气压力控制系统的性能进行了分析,并通过Matlab仿真和试验拟合对其控制性能进行改进.     

单齿转子压缩机排气过程中压力变化规律的测试

测试了单台转子压缩机的P-θ图，分析了排气过程中的压力变化规律，重点讨论了与排气孔口设计密切相关的排气初期阶段的压力变化规律。     

SA-250W空气压缩机运行故障分析

SA-250W水冷喷油式双螺杆空气压缩机的冷却润滑系统、油气分离系统、气量调节系统是保证机器正常运行的关键系统,现对压缩机排气超温、含油超标、排气压力偏低等故障原因进行分析,并提出解决方法和改进措施。     

气源净化技术问答

17．什么是空压机的排气压力？取决于什么？ 答：空压机的排气压力是指最终排出空压机的空气压力,它在末级工作腔的排气口处测出,单位为Pa或MPa。在某些场合,排气压力又称为“背压力”。     

气动阀用消声器的研究与设计

带有气动装置的机器正常工作时,气动阀产生的间歇性排气噪声的A声级高达110 dB。应用Lighthill的小振幅波在无限介质中的波动方程,分析了气动阀的排气噪声产生机理。某型电气比例压力阀间歇性排气噪声具有中高频特性,因而对人耳及其身心健康危害大。基于自由射流具有自模性特性和拟有序运动结构特点,提出了在射流过渡段与射流发展主段的“中心”区域,嵌入不锈钢纤维吸声材料,通过破坏等效四极子源产生噪声并在该声源产生声音前消声的降噪原理,进而利用多孔扩散材料和不锈钢纤维材料,设计了一种混合式结构消声器,对该消声器进行了实验测试分析并发现:在压力为0.33 MPa时,该消声器排气噪声A声级为81 dB(A),降噪量为28.8 dB(A),达到符合国家标准规定85 dB(A)及其以下的要求,表明了混合式消声器具有较好地降低气动阀间歇性排气噪声的性能。     

容积式压缩机排气流动的数值计算

建立了通用于容积式压缩机排气过程中描述排气口气速和工作腔内气体压力变化的数学模型，以往复压缩机为例，应用龙格一库塔法对其进行数值求解，得到了排气口气速和工作腔内气体压力随主轴转角的变化规律。研究内容有助于排气口开启面积的优化设计，以减小排气流动损失，适用于往复、螺杆、涡旋和转子等其它类型的容积式压缩机。     

通用小型汽油机188F尾气排放现状分析

本文选取四台典型的通用小型汽油机进行了尾气排放系统分析,找出了国内外同类产品的排放差异,以及与美国EPAⅢ阶段尾气排放限值的差距.通过贡献率分析找出了影响NOx、THC的主要工况,同时利用统计分析手段系统分析了65台国产188F发动机排放水平,得出了当前国产188F的排放现状.这对指导国内通用小型汽油机企业找出自身产品差异和排放现状,选择竞争机型和机内净化技术路线提供了有力的依据.     

高强化柴油机排气门锁夹处断裂分析

某强化柴油机在部件考核试验中排气门锁夹槽部位发生断裂。采用宏观、微观断口分析及金相检验等,对排气门锁夹槽断裂处进行了失效分析,结果表明,该排气门锁夹槽断裂为疲劳断裂,并提出了有效的防范措施。     

EGR和催化转化净化汽油车排气的试验研究

在发动机排气再循环和催化转化机理与车用汽油机排气特性研究的基础上，本文通过对车用汽油机装上EGR的催化转化装置后，在发动机台架上进行中低转速下的发动机负荷特性试验，探讨在有无EGR时对催化转化净化效果的影响。     

发动机尾气余热蒸发换热器的设计研究

简要介绍了余热回收理论和热管原理及工作特性,并在此基础上进行了热管传热过程计算、热阻分析、热管设计和选型、材料选择和热管换热器结构计算等,设计了一台尾气余热回收甲醇蒸发器,并根据设计参数进行三维建模。最后对该设计进行校核计算,结果表明,本文设计的发动机尾气余热甲醇蒸发器不仅能满足换热需求,而且具有较小的压力损失,能满足实际需求,对指导生产具有一定意义。     

A study on characteristics and control strategies of cold start operation for improvement of harmful exhaust emissions in SI engines

Emission regulations for automobiles have become more stringent and the improvement of emission during cold start has been a major key issue to meet these regulations. Among many kinds of factors that affect cold start operation, ignition timing is crucial to improve emission characteristics due to the influence on exhaust gas temperature. Recent progress in variable valve timing allows optimized valve event strategies under various ranges of engine operating conditions including cold start. This study investigates effects of ignition and exhaust valve timing on exhaust gas temperature, combustion stability and emission characteristics through cold start bench tests of an SI engine. Experimental results show that exhaust valve timings and ignition timings significantly affect exhaust gas temperature and stability of engine operation under cold start condition. Exhaust valve timing also affects CO and NO_x emission due to changes in residual gas fraction of the combustion chamber. Ignition timing mainly affects exhaust gas temperature and HC emission. A control strategy, advanced exhaust valve timing and retarded ignition, is plausible in order to achieve reduction of exhaust emission while maintaining stability under cold start operation of SI engines.     

Dynamic analysis of a PDP exhaust hole processing equipment considering glass substrate interaction

Exhaust hole drilling is one of the PDP (Plasma Display Panel) manufacturing processes to make about 1mm diameter holes for sucking out air in order to generate vacuum between two PDP glass substrates. In the drilling process, bigsized glasses about the size of a queen size bed are loaded, aligned, drilled, and unloaded, during which the dynamic interactions between glass and the handling equipment are very significant. To analyze exhaust hole drilling equipment dynamics, interaction with glass substrates that have somewhat different material properties from general glasses should be considered. The Young’s modulus and Poisson ratios of the substrates have been determined experimentally and verified via computation that simulates a well-known three-point bending test. Dynamic interaction of the glass with the handling equipment is modeled using a flexible glass and rigid body handling equipment models. The velocity profile by which the glasses are driven and the material properties of the handling equipment components contacting with the glasses are evaluated in view of the structural integrity of the glass and the operational efficiency of the equipment. The dynamic model is demonstrated to be an effective design tool for an exhaust hole drilling machine. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Tae Oh Tak received his B.S. and M.S degree in Mechanical Design and Production Engineering from the Seoul National University in Korea in 1982 and 1984, respectively. He obtained his Ph.D. degree from the University of Iowa, USA in 1990. He is currently a professor at the Department of Mechanical and Biomedical Engineering at the Kangwon National University in Chuncheon, Korea. His research interests are multibody dynamics and sensitivity analysis.     

活塞排气式气动发动机排气损失分析

对一款新型活塞排气式气动发动机曲轴处于恒转速工作状态和变转速工作状态的排气损失进行了分析,总结了排气损失原因,提出了活塞排气阀的改进措施。结果表明,限制发动机曲轴最低转速,同时采取改进的活塞排气阀结构可以较好地消除排气损失。     

基于变精度粗糙集的柴油发电机排气阀故障诊断方法研究

提出一种基于变精度粗糙集算法的阀门故障诊断方法。该方法具有一定的容错能力,同时能够在确保故障规则具有较高准确度和覆盖度的前提下得到尽可能简洁的规则集。将该方法用于柴油机排气阀典型故障的诊断,研究表明该方法具有良好的故障诊断性能。     

Combustion and emission characteristics of HCNG in a constant volume chamber

Finding an alternative fuel and reducing environmental pollution are the main goals for future internal combustion engines. Hydrogenmethane (HCNG) is now considered an alternative fuel due to its low emission and high burning rate. An experimental study was carried out to obtain fundamental data for the combustion and emission characteristics of pre-mixed hydrogen and methane in a constant volume chamber (CVC) with various fractions of hydrogen-methane blends. A pre-mixed chamber was used to obtain a good mixture of these gases. Exhaust emissions were measured using a Horiba exhaust gas analyzer for various fractions of hydrogen-methane blends. The results showed that the rapid combustion duration was shortened, and the rate of heat release elevated as the hydrogen fraction in the fuel blend was increased. Moreover, the maximum mean gas temperature and the maximum rate of pressure rise also increased. These phenomena were attributed to the burning velocity, which increased exponentially with the increased hydrogen fraction in the fuel blend. Exhaust HC and CO₂ concentrations decreased, while NO_X emission increased with an increase in the hydrogen fraction in the fuel blend. Our results could facilitate the application of hydrogen and methane as a fuel in the current fossil hydrocarbon-based economy and the strict emission regulations in internal combustion engines.     

阳极焙烧排烟架的模糊PID复合控制

阳极焙烧系统是一个具有耦合、大时滞、非线性的控制系统,其中排烟架是阳极焙烧系统的重要组成部分。针对系统存在的滞后及时变问题,该文采用稳态、动态性能较好的复合模糊控制器对其进行控制。通过仿真及运行的结果可以表明,复合模糊控制效果明显优于传统的PID控制,提高了控制系统的稳定性和鲁棒性。