Development of a small DMFC bipolar plate stack for portable applications

The direct methanol fuel cell (DMFC) is regarded as a promising candidate in portable electronic power applications. Bipolar plate stacks were systematically studied by controlling the operating conditions, and by adjusting the stack structure design parameters, to develop more commercial DMFCs. The findings indicate that the peak power of the stack is influenced more strongly by the flow rate of air than by that of the methanol solution. Notably, the stack performance remains constant even as the channel depth is decreased from 1.0 to 0.6 mm, without loss of the performance in each cell. Furthermore, the specific power density of the stack was increased greatly from ∼60 to ∼100 W l⁻¹ for stacks of 10 and 18 cells, respectively. The current status of the work indicates that the power output of an 18-cell short stack reaches 33 W in air at 70 °C. The outer dimensions of this 18-cell short stack are only 80 mm × 80 mm × 51 mm, which are suitable for practical applications in 10–20 W DMFC portable systems.     

Bionic Design and Simulation Analysis of Energy-Efficient and Vibration-Damping Walking Mechanism

节能减振步行机构的仿生设计及仿真分析

张锐¹,庞浩¹,何远^1,2,韩佃雷¹,文立阁³,江磊⁴,李建桥¹

（1. 吉林大学 工程仿生教育部重点实验室,长春 130022;

2. 长春长光睿视光电技术有限责任公司,长春 130102;

3. 吉林大学 机械与航天工程学院,长春 130022;

4. 中国北方车辆研究所,北京 100072）

摘要：非洲鸵鸟能以60 km/h的速度持续奔跑30分钟,其后肢结构具有优良的节能、减振性能。为实现腿式机器人高效节能、缓冲减振的腿部机构的设计,根据鸵鸟跗骨间关节的被动回弹特性以及腿部的输出刚度可变特性,结合鸵鸟后肢结构的比例和尺寸,设计出了仿生刚-柔复合腿式机器人单腿结构。并且利用ADAMS软件模拟了仿生机械腿的运动。通过运动仿真分析,研究了内弹簧刚度系数在一定范围内的变化对机身质心垂直加速度以及电机功耗的影响,获得最佳的内弹簧刚度系数为200 N/mm,并进一步验证了内外弹簧机制能够有效地降低机械腿的能耗。仿真结果表明,采用内外弹簧机制能够有效降低电机约72.49%能耗。

关键词：工程仿生;仿生机械腿;被动回弹特性;刚-柔复合结构;节能减振

     

重型车辆双路制动液压系统性能仿真

对重型车辆电液伺服控制双路制动器系统进行了分析与设计。采用电液伺服控制的双联制动阀控制双腔制动油缸的双路制动方案,实现车辆的行车制动和紧急制动。通过分析制动器系统各组成模块和连接管路对制动性能的影响,建立了制动器系统的非线性数学模型。应用MATLAB/Simulink对系统的双路行车制动性能进行了仿真研究,验证了设计方案的合理性。台架试验表明:所设计的制动器液压系统的性能达到了设计要求。     

Corrosion mechanism and corrosion model of Mg-Y alloy in NaCl solution

Corrosion of Mg–Y alloy was studied using electrochemical evaluations, immersion tests and SEM observations. Corrosion mechanisms of Mg-(0.25 and 2.5) Y alloy and Mg-(5, 8, and 15) Y alloy were uniform corrosion and pitting corrosion respectively, and the content of Mg_(24)Y_5 phases determined its effect acting as cathode to accelerate the corrosion or corrosion barrier to inhibit the corrosion. Corrosion resistance of Mg-(0.25, 2.5, 5, 8, and 15) Y alloys was as follows: Rt(Mg-0.25Y) Rt(Mg-8Y) Rt(Mg-15Y) Rt(Mg-5Y) Rt(Mg-2.5Y). Y could significantly improve the corrosion resistance of the Mg-Y alloy, but the excess of Y deteriorated the corrosion resistance of the Mg-Y alloy. The optimum content of Y in the studied alloys was 2.5%.     

Analysis on the gear-shifting schedule of hydraulic automatic transmission

With an advanced foreign hydraulic automatic transmission as the objective, an analytical method for the gear-shifting schedule is proposed. First the demanded maximum gradient of test is estimated. Then a test scheme and analytical procedure is formulated by initial test and hypothetical shift parameters. Finally through gear-shifting tests under different road conditions, load, accelerator pedal position limitation, throttle opening and output shaft speed are found to be the gear-shifting parameters. Under a common road condition, the gear-shifting schedule is a double-parameter schedule. Based on the driver''s demands on braking and dynamic performance, different shift schedules are made under downhill, uphill and quick releasing acceleration pedal conditions. The operation criteria of down-shift schedule on abrupt grade are proposed.     

基于Maxwell的电磁阀仿真与分析

针对电磁阀传统设计方法中,产品设计周期长、试制实验费用高等问题,本文采用有限元方法在产品设计初期对电磁阀的性能进行预测。首先,运用Ansoft Maxwell软件分别建立了电磁阀的三维与二维有限元模型,进行了磁场分析与电磁力计算,通过比较发现三维模型与二维模型计算结果与测试结果均吻合较好。最后,在二维模型的基础上,运用Maxwell软件的参数化设计功能进一步分析了不同初始间隙、不同驱动电压对电磁力的影响。结果表明,基于Maxwell的电磁阀有限元仿真能够在产品的设计初期快速地预测电磁阀的性能,为电磁阀的设计与优化提供理论指导。     

车辆电子电气系统测试方法研究

随着车辆电子信息技术的飞速发展,车辆电子电气系统在整车的可靠性中起着至关重要的作用。对电子电气系统的测试传统的做法往往是在整个系统完成之后利用整车环境进行的,这种方法不利于发现早期问题,对系统可靠性带来隐患;为了提升车辆电子电气系统可靠性,主要从实际工程测试出发,从项目的前期以及后期两个方面对电子电气系统的测试进行了分析,在项目的前期主要进行快速原型以及HIL测试,在项目的后期主要进行功能、性能、接口测试,从而实现提升车辆电子电气系统高可靠性以及经济性的提升。     

低频电磁场对n-SiCp/2024复合材料组织与性能的影响

分别采用低频电磁铸造(LFEC)与传统半连续铸造(DC)制备n-SiC_p/2024复合材料铸锭,并对铸锭进行挤压以及T6热处理。通过金相组织观察(OM)、TEM、室温力学性能测试等手段,分别研究了低频电磁铸造与传统半连续铸造工艺对n-SiC_p/2024复合材料的微观组织、力学性能的影响情况。实验结果表明:DC制备的n-SiC_p/2024复合材料铸锭表面局部存在偏析瘤,大多数n-SiC_p团聚在晶界处,只有少数聚集在晶粒内部;LFEC制备的n-SiC_p/2024复合材料铸锭组织晶界清晰,n-SiC_p团聚现象基本消失,组织均匀,晶粒细化效果明显。LFEC制备工艺可以有效细化n-SiC_p/2024复合材料铸锭的晶粒尺寸,其电磁搅拌作用对消除n-SiC_p颗粒的团聚现象有显著作用;与DC工艺相比,LFEC可同时提高复合材料的强度与延伸率。     

基于并行工程的武器装备测试性工作模型分析

针对武器装备常规测试性工作中存在的主要问题,基于系统工程理论的并行工程方法,提出了一种新的测试性工作方法,并建立了基于并行工程的装备测试性工作模型,用以指导测试性工作。通过对模型适用性分析表明,基于并行工程的测试性工作模型各个项目间有主次之分,工作重点突出,模型较为合理。     

The influence of corrosion on the life of steel ropes and prediction of their decommissioning

Operation of steel wire ropes brings a number of risks that affect their lifetime. During operation of steel ropes the one of the most adverse effects is the effect of corrosion. Manufacturers are working hard to eliminate the effect of corrosion by lubricating cables, surface protection of wires and alike, but these methods are not able eliminate corrosion rise and propagation totally. To examine the process of degradation of the mechanical properties of the steel ropes in the corrosive environment, we conducted research on a rope sample as a whole and on the samples of individual wires. The samples were exposed to the saline solution for a period of total duration of 64 days. The monitoring of the degradation was carried out at 16-day intervals when the samples were subjected to mechanical tests. The rope sample as a whole was subjected to the tensile test. The individual wire samples were subjected to the tensile test, alternating bend test and torsion test. The criteria according to the standard EN 12927-6 and the Slovak Mining Office Regulation (SBU) No. 50/1989 Coll. were used to evaluate the results of the degradation of the mechanical properties. These were then confronted with the criteria used in maritime shipping. Based on the results of the mechanical tests, the trend of the degradation of the mechanical properties in the saline solution and marginal values for the rope decommissioning were determined. Gradually, with an increase of the impact of corrosion on the rope samples, the impact on rope rotation resistivity was also registered, besides the mechanical properties changes.