One-dimensional model on fuel penetration in diesel sprays with gas flow

In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions.     

Experimental study of EGR cooler regeneration aided by oxygen-fed NTP and air-fed NTP

Based on non-thermal plasma (NTP) technology fed by oxygen and air as the gas source respectively, the experimental system of exhaust gas recirculation (EGR) cooler regeneration was built to do a study at different regeneration temperatures. By measuring the concentration of main active substance and CO_x in regeneration process, the influence of temperature on regeneration aided by oxygen-fed NTP and air-fed NTP was investigated. The experimental results indicate that EGR cooler can be regenerated both by air-fed NTP and oxygen-fed NTP at a wide temperature range of 18 °C ～ 300 °C. By comparison of the regeneration with oxygen-fed NTP and air-fed NTP, it can be easily known that the regeneration effect is most remarkable at 150 °C with oxygen-fed NTP and at 120 °C with air-fed NTP. In addition, when the temperature is below 150 °C especially at 120 °C, the regeneration efficiency of air-fed NTP is lower than oxygen-fed NTP, nevertheless, when the temperature is above 150 °C, air-fed NTP has a superiority in regeneration and the higher the temperature is, the more obvious the superiority will be.     

基于Wilson熵分布假设的交通公平性量化评价模型

在对交通公平性的量化评价方法进行考察的基础上,从效益分配符合"W ilson熵分布"的假设出发,尝试建立了群体决策型的公平性量化评价模型,该模型综合考虑了区域公平性和不同群体效益归属公平性.对于模型的分析表明交通设施的群体决策型公平性量化评价模型具有最佳解.同时通过数学方法可以证明建立的基于"W ilson熵分布"假设的交通公平性量化评价模型能很好地体现对于弱势群体和不发达区域的效益"补偿"作用.分析结果表明该模型用于交通公平性评价是合理、可行的.     

地区公路项目兼顾效率与公平的优先级评价

政府投资的地区公路项目受到建设资金制约,在考虑项目建设效益的同时需兼顾地区的均衡发展.文中在总结前人研究成果的基础上,建立计量经济学的面板数据回归模型,采用GMM方法进行模型参数估计.模型采用年鉴数据,利用专业软件进行回归分析.并将回归分析的结果与前人的研究进行对比,对模型在中国部分省的适用性进行了评价.根据对实际案例的评价结果表明,评价模型具有很好的实用性.     

按使用工况改善重型柴油机经济性的研究

对重型柴油机运行工况进行了分区,并分析了 CA6DL 系列柴油机常用工况.以 CA6DL2-35型柴油机为例,探讨了按使用工况改善重型柴油机经济性的方法.试验结果表明,在高于1600r/min的中高转速区域内,改进后CA6DL2-35型柴油机较对比柴油机油耗降低0～2g/(kW.h);在1200～1600r/min的中低转速区域内,较对比柴油机油耗降低0～4g/(kW.h);在800-1000r/min的区域内,较对比柴油机油耗高0-5g/(kW.h).     

子午线轮胎硫化过程仿真

根据对轮胎硫化程度的分析,利用ABAQUS软件对全钢子午线轮胎11.00R22.5建立了硫化温度场仿真模型,在此基础上利用阿累尼乌斯方程计算了轮胎各试验测温点处的硫化程度.仿真与硫化试验对比结果表明,仿真分析的硫化温度和硫化程度随时间的变化与试验结果相吻合,证明了所建有限元模型和计算方法的正确性.     

汽车排气消声器的试验研究及频谱分析

采用声压级测量法测试出YC4W31柴油机排气消声器需要优化的频率范围.建立了原消声器计算模型,并验证了该模型的正确性.基于传递矩阵法提出两种改进方案,并依据试验结果对改进后排气消声器进行了频谱分析.结果表明,在频率低于400Hz时,按方案2改进的消声器比按方案1改进的消声器消声量提高3 dB(A)左右;比原消声器消声量平均提高7 dB(A)左右.     

CO2缸内喷射对直喷柴油机燃烧排放特性的影响

在一台单缸直喷柴油机上用CO2喷射来模拟EGR,研究了CO2缸内喷射始点和喷射量对直喷柴油机燃烧和排放的影响.结果表明:CO2喷射始点提前时,燃烧始点推迟,NOx排放降低.与外部EGR类似,增大缸内CO2喷射量,也可明显降低NOx排放;但是碳烟排放先增大后减小.     

边界元法在液力变矩器内流场中的应用

本文建立了适用于液力变拒器导轮叶栅内流场流动状态的边界元法计算 模型和计算程序,利用激光测速仪获取边界条件,从而得到了导轮叶松 内部二维速度场。此外,通过与实测值比较,检验了程序的精度。