Actively translating a rear diffuser device for the aerodynamic drag reduction of a passenger car

This research aims to develop an actively translating rear diffuser device to reduce the aerodynamic drag experienced by passenger cars. One of the features of the device is that it is ordinarily hidden under the rear bumper but slips out backward only under high-speed driving conditions. In this study, a movable arc-shaped semi-diffuser device, round in form, is designed to maintain the streamlined automobile??s rear underbody configuration. The device is installed in the rear bumper section of a passenger car. Seven types of rear diffuser devices whose positions and protrusive lengths and widths are different (with the basic shape being identical) were installed, and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. The main purpose of this study is to explain the aerodynamic drag reduction mechanism of a passenger car cruising at high speed via an actively translating rear diffuser device. The base pressure of the passenger car is increased by deploying the rear diffuser device, which then prevents the low-pressure air coming through the underbody from directly soaring up to the rear surface of the trunk. At the same time, the device generates a diffusing process that lowers the velocity but raises the pressure of the underbody flow, bringing about aerodynamic drag reduction. Finally, the automobile??s aerodynamic drag is reduced by an average of more than 4%, which helps to improve the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h.     

PID plus fuzzy logic method for torque control in traction control system

A Traction Control System (TCS) is used to control the driving force of an engine to prevent excessive slip when a vehicle starts suddenly or accelerates. The torque control strategy determines the driving performance of the vehicle under various drive-slip conditions. This paper presents a new torque control method for various drive-slip conditions involving abrupt changes in the road friction. This method is based on a PID plus fuzzy logic controller for driving torque regulation, which consists of a PID controller and a fuzzy logic controller. The PID controller is the fundamental component that calculates the elementary torque for traction control. In addition, the fuzzy logic controller is the compensating component that compensates for the abrupt change in the road friction. The simulation results and the experimental vehicle tests have validated that the proposed controller is effective and robust. Compared with conventional PID controllers, the driving performance under the proposed controller is greatly improved.     

CFG桩复合地基褥垫层的设计机理

CFG桩复合地基是由桩、土和褥垫层三部分组成,其中褥垫层的设计是该复合地基的核心技术,它对复合地基的受力和变形具有重要的影响,而褥垫层的作用又与其厚度取值密切相关。利用Terzaghi极限承载力理论,简要介绍了CFG桩复合地基的作用机理,提出了合理的褥垫层厚度,最佳桩间距和桩土应力比的数学计算式,结合实际工程验证了计算结果的可行性,在褥垫层初始设计时能起到理论指导作用。     

空泡水洞中拖式吊舱推进器脉动压力测量及空泡观测

针对吊舱推进器的关键技术,开展拖式吊舱推进器空泡性能和脉动压力的试验研究。试验在海军工程大学空泡水洞实验室进行,观察吊舱推进器桨模在不同工况下空泡发展和变化情况,并用人工观察方式进行整理记录,同时通过螺旋桨正上方区域安装的脉动压力传感器测量脉动压力。对试验结果进行分析,探讨拖式吊舱推进器不同工况下脉动压力和空泡性能的特点和规律及其对水动力性能的影响,为吊舱推进器性能研究及设计提供参考。     

便携式水下声信标探测定位设备技术设计与实现

针对声基阵水下搜寻定位系统需要使用大型船只及直升机等大型操作平台的缺点,介绍了一种简单、便携、高效的水下声信标探测定位设备的设计与实现方法.利用指向性水听器及混频方法,将需要探测和定位的水下声信标信号通过音频形式输出,充分利用指向性水听器较普通水听器空间增益高以及人耳对信号识别能力强的特点,提高了复杂海况条件下对弱信号的检测能力.阐述了设备的组成、工作原理以及设备主要单元的设计方法,给出了设备样机在海上试验的结果,并对其适用的场合进行了说明.     

苯乙烯与3-(甲基丙烯酰氧基)丙基三甲氧基硅烷位置选择凝胶材料的制备与热性能研究

为了改善聚苯乙烯(PS)的耐热性能,开发兼具有机-无机特性的新型凝胶材料,采用位置选择分子设计与溶胶-凝胶技术,选择含有可水解形成SiO2的官能团的单体3-(甲基丙烯酰氧基)丙基三甲氧基硅烷(MSPMA)与苯乙烯(STY)共聚,利用硅烷的水解、缩聚以共价键的方式在大分子主链上引入纳米SiO2基团.通过改变单体配比合成了一系列SiO2导入位置和导入含量不同的凝胶材料.研究了共聚体的合成、水解过程和纳米SiO2基团在侧链上的分布情况以及对热性能的影响.结果表明:所得凝胶材料具有极好的光学透明性,两种单体在共聚物中几乎可以是交替进行或是按一定的比例进行聚合,形成交替“嵌段”共聚物,水解的SiO2在微纳米级且分散均匀,凝胶材料的热性能随着SiO2含量的增加而提高.     

Aerodynamic Drag Optimization for a Container Truck in Crosswind Based on Surrogate Model

为降低集装箱载货车在侧风作用下的燃油消耗量,对其导流罩进行优化.以最小化气动阻力为目标,导流罩的4个尺寸参数宽W、长L、高H和角度α为设计变量,采用最优拉丁方试验设计选取30个样本点,基于Kriging模型建立了代理模型进行优化.同时根据优化结果加工试验模型,通过风洞试验验证了优化方法的可行性,表明代理模型可很好地取代实际的仿真过程以进行优化,与初始导流罩相比,安装优化导流罩的集装箱载货车在侧风作用下的阻力系数最大可降低11.5％.     

摩托车发动机热负荷多点测试方法及应用

摩托车发动机台架测试时,通常以监控火花塞垫圈温度和机油温度来判定发动机的热负荷状况。通过增加测试排气温度,进、排气门挡油罩附近温度,空气燃油比和测试转矩等参数,来提高发动机热负荷状况判定的准确性。经试验表明,此方法能为热贞荷的判定对比提供有力依据,并为处理热负荷问题指明方向。     

岩溶区桥梁基桩极限承载力的突变求解方法

分析了岩溶区桥梁基桩极限承载力组成特性及桩端破坏模式,将其极限承载力分为桩侧土体极限侧阻力、嵌岩段极限侧阻力及端阻力3部分.其中,桩侧土体极限侧阻力由各土层极限摩阻力求和可得,嵌岩段极限承载力则引入Hoek -Brown岩石强度准则,采用岩体质量评价指标进行描述.而后,针对岩溶区基桩工程的特点,结合突变理论的基本概念,建立了岩溶区基桩的力学简化模型及其势能函数的表达形式,并导出岩溶区桥梁基桩桩端极限阻力的尖点突变模型的分叉集方程.在此基础上,根据下伏溶洞顶板失稳破坏条件,求解分叉集方程导得岩溶区桥梁基桩桩端极限荷载的表达式,由此提出了岩溶区桥梁基桩极限承载力的确定方法.工程实例对比分析表明该方法的可行性.