Effect of Heavy-Duty Diesel Engine Operating Parameters on Particle Number and Size Distribution at Low Speed Condition

Experiments and simulations were used to investigate the effect of a range of engine operating parameters and fuel characteristics on the particle size and particle number (PN) concentration at low speed and idle speed condition. The occurrence, size, and concentration of particles were tested against a range of parameters including start of injection (SOI), common rail pressure, exhaust gas recirculation (EGR) ratio and load. The results showed that the homogeneity of the mixture had the greatest impact on particle size and number concentration. The performance of particle is different at different levels of load. The particle were of nucleation mode at idle condition, and the cold idle particles had a slightly larger diameter than those produced at hot idle. By using the diesel and under high load, at EGR ratios of less than 20 %, most particles were of nucleation mode. At EGR ratios exceeding 20 %, nucleation-mode particles were gradually replaced by accumulation-mode particles. At EGR ratios above 30 %, most particles were of the accumulation mode. Under the same load, gasoline compression ignition produced particles of smaller size and reduced particulate mass (PM). The use of gasoline extended ignition delay, as the high volatility and octane number of the fuel improved the homogeneity of the mixture. Finally, a linear relationship was found between PM and PN. The relative contribution of the different factors to the formation of nucleationor accumulation-mode particles was investigated.     

Effect of Charge Density on Spray Characteristics,Combustion Process,and Emissions of Heavy-Duty Diesel Engines

In-cylinder charge density at top dead center is an important parameter of diesel engines and is influenced by intake pressure, intake temperature, and compression ratio. The effects of charge density on fuel spray, combustion process, and emissions were investigated by using a constant volume bomb and a heavy-duty diesel engine. Spray development resistance increased with the increase of the charge density in the constant volume bomb. It was found that short spray penetration was accompanied by a large spray cone angle in the former stage with high charge density. However, the equivalence ratio was lowered and the degree of homogeneity of the mixture was increased in the later stage owing to the rapid interaction of fuel and gas at a high mixing rate. Combining the first law of thermodynamics and the second law of thermodynamics for analysis, as the charge density increased, the gross indicated thermal efficiency (ITEg) was improved. However, pumping loss had to be considered with higher charge density. Under this condition, the brake thermal efficiency (BTE) trend was increased initially and decreased subsequently. Under high-load operation (1200 r/min BMEP, 2.0 MPa), the minimum charge density value of 44.8 kg/m³ was found to be reasonable. This charge density was suitable for combustion and brought about minimum exhaust energy and trade-off emissions. Moreover, by analyzing two operation conditions in terms of the maximum BTE with the Miller and the conventional cycles, compression temperature and combustion temperature were reduced in the Miller cycle with the charge density 44.8 kg/m³. A high C_p/C_v could improve the cylinder exergy/power conversion process by its positive effect of increasing the specific heat ratio. Owing to the interaction between a high C_p/C_v and exergy loss to heat transfer, the condition with the minimal charge density could produce more piston work.     

30 000 DWT散货船货舱段结构强度有限元计算

利用MSC Patran/Nastran和英国劳氏船级杜(LR)的ShipRight SDA软件对30000DWT散货船进行货舱段结构强度直接计算,使其满足散货船共同结构规范直接强度分析的要求.利用整体舱段的粗网格模型计算结果,建立于模型划分精细网格进行结构细部疲劳评估.     

基于FCE-DEA-AHP的城市物流绿色度评价研究

针对城市物流的绿色化发展问题,运用层次分析法对城市物流绿色化体系进行划分,在此基础上构建模糊综合评判模型,利用数据包络分析法把多个城市物流在各单因素指标的绿色度表现量化,并结合相应各指标权重进行综合评价和排序,最后通过实例印证评价方法的直观性和高效性.     

集卡提箱预约配额与场桥配置的联合优化

在集卡提箱预约中,集装箱码头场桥配置和预约配额的联合优化是缩短集卡等待时间,提升资源利用率的关键. 针对提箱作业的实际特点,构建了双目标整数规划模型,设计了基于非支配排序遗传算法的求解方法. 当码头需求较少时,采取动态调整随机分配场桥最佳;当码头需求较高时,采取动态调整与按需配置相组合的方式最佳. 以国内某码头为原型,通过不同规模的算例实验,验证了模型和算法的有效性. 所提方法可快速生成高质量、多样化的前沿解,实现了场桥资源与集卡作业需求的匹配优化,为码头管理者在资源投入与集卡等待时间的权衡中,提供了决策支持.     

STUDIES ON THE RELATIONSHIP BETWEEN SUBSTANCE P AND ABNORMAL GASTROINTESTIANL TRANSIT

Substance P is a peptide which is composed of1 1 kinds of amino acid.This peptide is one of themembers of the tachykinin s family.It can be re-leased by intrinsic neurons of gastrointestine andexternal nerve,forexample,Vagus nerve.Some ofthese neurons are situated in nerve plexus which islocated under gastrointestinal mucosa and othersare situated in nerve plexus between longitudinalmuscle and circular muscle.SP can make gastroin-testinal smooth muscle contract and promote themovement of gas…     

发动机曲柄连杆机构活塞销卡滞现象机理分析

通过仿真计算分析了某发动机在开发过程中出现的曲柄连杆机构活塞销卡滞现象的机理和本质,并提出了"残余间隙"概念.在刚度一定条件下采用接触摩擦副变形图表明了装配间隙及其接触摩擦副的变形与"残余间隙"的关系,找到了曲柄连杆机构活塞销卡滞原因.在此基础上并结合工程实际提出了优化设计方案和摩擦副间隙的工程判据,通过试验验证了优化方案的可行性.     

基于迭代学习控制的道路模拟算法

研究了迭代学习控制在道路模拟试验台上的应用。将道路模拟控制系统所要实现的控制任务归结为有限时间区间上的完全跟踪问题,在不辨识系统模型的情况下,根据对象系统的先验知识,直接设计迭代学习律。使用了一种平滑滤波器型开环迭代学习控制,以提高系统的鲁棒性和控制品质。试验结果表明所设计的控制系统令人满意。     

SMA-10彩色沥青应用研究

通过对SMA彩色沥青混凝土的试验研究,简单介绍了彩色沥青混凝土的原材料的选择、配合比设计、拌和及施工要点。     

新工科背景下的高校节能与新能源汽车教学改革探索

新工科的重要意义是应对新时代国际形势的变化,基于未来国家的战略发展需要,培养能够支撑我国产业的创造性卓越工程人才.为了培养车辆工程的学生紧跟目前汽车产业电动化、智能化的趋势,本文对节能与新能源汽车的教育教学模式进行探讨,重点分析当前节能与新能源汽车课程存在的问题,并从教学模式、教学内容以及产教结合等多个方面提出解决问题...