轿车制动性能的控制方法

针对目前轿车开发以逆向开发为主体,对整车制动性能控制能力较弱的实际问题,文章提出了一套制动性能控制方法,即以整车设计参数、制动强制性法规适应性及制动系统零部件尺寸系列化等为制动性能控制的输入约束条件,在设计初期预测新开发轿车的9项主要制动性能,经过多辆轿车制动系统的开发实践验证,此性能控制方法不仅可保证制动系统设计质量,而且缩短了轿车制动系统的设计周期。     

Effects of mixture stratification on HCCI combustion of DME in a rapid compression and expansion machine

Compression ignition of homogeneous charges in internal combustion (IC) engines is expected to offer high efficiency of DI diesel engines without high levels of NOx and particulate emissions. This study is intended to find ways of extending the rich limit of HCCI operation, one of the problems yet to be overcome. Exhaust emissions characteristics are also explored through analyses of the combustion products. DME fuel, either mixed with air before induction or directly injected into the combustion chamber of a rapid compression and expansion machine, is compressed to ignite under various conditions of compression ratio, equivalence ratio, and injection timing. The characteristics of the resulting combustion and exhaust emissions are discussed in terms of the rate of heat release computed from the measured pressure, and the concentrations of THC, CO, and NOx are measured by FT-IR and CLD. The experimental data to date show that operation without knock is possible with mixtures of higher equivalence ratio when DME is directly injected rather than when it is inducted in the form of a perfectly homogeneous fuel-air mixture. Although fuel injected early in the compression stroke promotes homogeneity of the DME-air mixture in the cylinder, it causes the mixture to ignite too early to secure good thermal efficiency and knock-free operation at high loads. Low temperature reactions occur at about 660K regardless of the fueling methods, fuel injection timing and equivalence ratio. The main components of hydrocarbon emissions turned out to be unburned fuel (DME), formaldehyde and methane.     

城轨车辆车控制动系统和架控制动系统防滑控制对比分析

为比较城轨车辆车控制动系统和架控制动系统在防滑控制方面的差异,详细分析车控制动系统和架控制动系统的防滑控制原理.从系统构成、控制软件、参考速度准确性和安全完整性等级等4方面,比较车控制动系统和架控制动系统的防滑控制功能,分析车控制动系统防滑安全功能安全完整性等级比架控制动系统高的原因.     

摩托车制动器拖滞力矩的研究

拖滞力矩主要是摩擦力矩,不但损坏零件,还容易造成盘式制动器抱死,发生意外事故,增加燃油消耗。当拖滞力矩为2Nm时,燃油消耗将增加3.1%-5。7%;当拖滞力矩为3Nm时,燃油消耗将增加4.6%-8.5%。通过实际测试,摩托车制动器的拖滞力矩在调试时应控制在0.5Nm以下为好。     

HS125GY越野摩托车中低速加速性能的改进

原HS125GY车所配化油器为柱塞式PZ26,与普通两气门125 mL发动机相当,采用四气门设计的目的是要提高进气填充效率,但PZ26化油器实际上却限制了发动机的进气效率.应匹配大口径化油器、进气管、空滤器来提高进气效率空间,按RX125进气口等效直径匹配化油器、进气管和低阻力系数空滤器.     

排气系统的数值模拟及优化设计

建立了汽车排气系统的三维计算流体力学模型,并采用并行计算方法对某排气系统的5款设计方案进行了模拟计算。以排气背压为评判准则,方案3背压最大,方案2背压最小,方案1、4和5的背压基本接近。通过对5种设计方案的催化转化器、消声器等部件进行详细的流场分析,找到了各款排气系统背压产生的主要原因,并提出了进一步的改进措施,确定了排气系统的最佳方案。     

某车型制动踏板感性能改进及试验验证

文章从客观评价角度对制动踏板感的改进进行了阐述,针对某车型制动信心不足问题,对制动踏板感客观数据结果与行业标准校核后,发现踏板感性能各指标普遍较差。后结合整改方案,通过对真空助力器、制动主缸等结构及参数的变更分析,制定对比验证方案,以验证制动系统优化方案可行性,并给出试验结论及建议。     

电动汽车真空助力制动系统的计算研究

分析了电动汽车安装电动真空助力制动系统的必要性。对真空助力制动系统的性能进行了分析计算,设计了电动真空泵最小真空度的计算流程。以改装的某型电-电混合动力轻型客车为例,给出了完整的制动系统的计算参数。计算结果表明,当电动真空泵最小真空度为37.5 kPa时,可为制动系统提供满足设计要求的制动助力。整车初步试验表明,所匹配的电动真空泵参数合理。     

Statistical model for gas turbine engines exhaust emissions

A statistical analysis has been developed from the ICAO databank to predict aero-engines exhaust emissions during a landing and take-off cycle (LTO). The ICAO databank contains updated emission indices for a vast number of turbojet and turbofan engines only, with thrust ratings greater than 26.7 kN. Correlations are developed and proposed for turboprop and turboshaft engines to overcome the difficulty of assessing exhaust emissions from these engines in absence of industry data. LTO emissions are predicted for a turbofan-powered commuter airplane (Embraer E195) using the surrogate model. It is demonstrated that the predictions are closer to the values extracted from the flight data recorder than to the emissions calculated with the ICAO method. Thus, approximate emissions indices applied to actual flight procedures are a better choice than a standard ICAO LTO emission estimate from the databank. The correlations are then applied to the prediction of LTO emissions of a turboprop airplane (Bombardier Q400).     

MSEMD排气系统扩压长支管定常流动研究

本文用数值方法研究了ＭＳＥＭＤ系统轴对称扩压长支管的定常流动特性。在贴体坐标系中用与时间相关的二维流动计算方法对湍流流动的控制方程进行了数值求解，用二阶ＭａｃＣｏｒｍａｃｋ差分方法处理内部节点，用二阶参考平面上的特征线法处理进、出口边界条件，并把计算结果与实测结果进行了比较，它们之间吻合得相当好。