Investigations on premixed charge compression ignition engine with external mixture formation and exhaust gas recirculation technique

Journal of Mechanical Science and Technology - In present scenario it is need for automobile sector to develop clean technology which will result in less fuel consumption and green house gas. The...     

Relation between particulate emissions and exhaust smoke level in premixed charge compression ignition engine

For simplicity in measurement, the smoke level or opacity of the exhaust gas is often measured in diesel engine tests for the purpose of estimating the level of particulate emissions in the belief that smoke level is proportional to the particulate emissions. Existence of the correlation between these two has been well established in conventional diesel engines, but it is not clear yet whether the linear relationship stays in PCCI engines, which are known to emit significantly less NOx but more hydrocarbons than the conventional diesel engines. The objective of this study was to investigate the existence of the correlation between the smoke level and particulate mass in a directly fuel-injected PCCI engine with a DOC in the exhaust system. The smoke and PM are simultaneously measured before and after the DOC, while the single-cylinder diesel engine is operated in either diesel or PCCI combustion mode under various operation conditions. The study reveals that many more hydrocarbons and particulates are emitted in PCCI combustion than in the diesel combustion, and the strong correlation between the engine-out smoke level and particulate emissions in the diesel combustion does not exist in PCCI combustion. The correlation, however, comes back in the post-DOC measurements where most of SOF contained in PM is removed by the DOC.     

基于黑箱模型和RBF-PID的HCCI发动机燃烧正时控制

由于均质充气压缩点燃(HCCI)发动机缺少直接控制其燃烧的手段,导致HCCI发动机的燃烧正时控制成为HCCI发动机的研究热点。以HCCI发动机进气歧管的温度和压力、燃油当量比、转速以及进气门关闭正时为输入,利用BP神经网络建立用于估计HCCI发动机燃烧正时的黑箱模型。在此模型基础上,以进气门关闭正时为控制量设计了PID控制器,并利用径向基神经网络对其参数进行整定,以实现对燃烧正时的反馈控制。实验结果表明,BP神经网络估计模型对HCCI发动机燃烧正时的估计误差小于0.4(CAD),能实现准确的估计;此外,与传统的PID控制器相比,设计的RBF-PID控制器在超调量、调节时间以及抗干扰性等性能方面均有改善。     

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。     

A numerical analysis of the effects of a stratified pre-mixture on homogeneous charge compression ignition combustion

Journal of Mechanical Science and Technology - We investigated the efficacy of fuel stratification in a pre-mixture of dimethyl ether (DME) and n-butane, which have different autoignition...     

Analysis of compression ignition combustion in a schnurle-type gasoline engine comparison of performance between direct injection and port injection systems-

A two-stroke Schnurle-type gasoline engine was modified to enable compression-ignition in both the port fuel injection and the in-cylinder direct injection. Using the engine, examinations of compression-ignition operation and engine performance tests were carried out. The amount of the residual gas and the in-cylinder mixture conditions were controlled by varying the valve angle rate of the exhaust valve (VAR) and the injection timing for direct injection conditions. It was found that the direct injection system is superior to the port injection system in terms of exhaust gas emissions and thermal efficiency, and that almost the same operational region of compression-ignition at medium speeds and loads was attained. Some interesting combustion characteristics, such as a shorter combustion period in higher engine speed conditions, and factors for the onset of compression-ignition were also examined.     

Effects of various intake valve timings and spark timings on combustion,cyclic THC and NOX emissions during cold start phase with idle operation in CVVT engine

In a gasoline SI engine, valve events and spark timings put forth a major influence on overall efficiency, fuel economy, and exhaust emissions. Residual gases controlled by the valve overlap can be used to reduce NOx emissions and the spark retardation technique can be used to improve raw THC emissions and catalyst light-off performance during the cold start phase. This paper investigated the behaviors of the engine and its combustion characteristics with various intake valve timings and spark timings during the fast idle condition and cold start. And cyclic THC and NOx emissions were measured at the exhaust port and their formation mechanisms were examined with fast response gas analyzers. As a result, THCs and NOx were reduced by 35% and 23% with optimizing valve overlap and spark advance during the cold transient start phase. Consequently, the valve events and ignition timings were found to significantly affect combustion phenomena and cold-start emissions. This paper was recommended for publication in revised form by Associate Editor Kyoung Doug Min Simsoo Park received his B.S. and M.S. degrees from Seoul National University in 1977 and 1979, respectively, and a Ph.D. from the State University of New York at Stony Brook. He served as a Principle Research Engineer at Hyundai Motor Company, a Director for Publication of the KSME, a Technical Advisor of Hyundai-Kia Motor Company, and an Editing Director, Project Director, International Director, Accounting Director, and General Affair Director of KSAE. He is currently Vice President of Editing and International at KSAE and a professor of mechanical engineering at Korea University.     

基于 AMESim 的液粘调速离合器伺服阀建模仿真研究

为了建立液粘调速离合器完整的液压控制回路,以伺服阀为例对回路中非标准阀的建模仿真方法进行了探讨. 首先通过分析液粘调速离合器液压系统的工作原理,并结合伺服阀的结构,利用仿真软件AMESim建立了伺服阀块的物理结构模型. 结合仿真分析,对控制油压与出口油压的关系以及影响出口油压的因素进行了研究. 结果表明,弹簧预紧力决定了打开阀口时所需的控制油压,但却并不影响出口压力随控制油压的变化梯度. 在此基础上将伺服阀放入液压控制回路中进行仿真,研究控制电流与工作油压的关系并与试验数据进行比较. 结果表明,建立的伺服阀模型仿真结果与试验结果相吻合,为其他非标准阀块的建模仿真提供了参考依据.     

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.     

铁路货车滚动轴承在运行中的故障诊断方法分析

通过对滚动轴承故障的基本形式介绍,结合THDS、TADS、TFDS工作原理,分析了三个系统对铁路货车滚动轴承在运行中故障诊断的优缺点。     

Ni-Cr合金真空钎焊金刚石工具基体热损伤分析

为研究高温钎焊金刚石工具时基体所受的热损伤对同种材料不同热处理状态下的工具基体进行分析与检测。基体材料选择45钢制作试样,对原始试样、真空炉中干烧至钎焊温度的试样以及与金刚石钎焊后试样的显微结构和显微硬度进行检测与对比分析;对原始试件和真空干烧过的试件进行拉伸性能试验,并用扫描电镜(SEM)对断口形貌进行观察。结果表明:45钢基体经高温真空干烧和钎焊后,晶粒粗大,致使强度、硬度、塑性等力学性能大幅下降,基体材料出现严重的热损伤。研究成果可为钎焊金刚石工具基体材料的选择和钎焊工艺的制定提供试验和理论依据。