农村公路养护管理评价指标体系研究

农村公路养护管理评价体系是一个多维的系统,不仅要对道路养护技术水平进行评价,也需要对日常养护水平、安全畅通、路网质量等要素进行综合评价。文中综合考虑了影响农村公路养护管理的各要素,建立了包含目标层、准则层、指标层的三级农村公路养护管理评价指标体系,并提出了农村公路养护管理评价实施的逻辑过程,即养护管理要素评价-养护要素预测-养护决策。     

起重吊钩的计算方法探讨

比较起重吊钩计算中公式法与有限元分析方法的差异,结合实际使用情况,给出在不同工作级别下选取吊钩危险截面参数的方法。     

小型LNG船C型独立液舱结构设计与研究

作为小型LNG船的关键技术之一,C型独立液舱及其维护系统决定着整船的经济性能和安全性能。简要介绍了C型独立液舱的特点,详细阐述了其结构设计流程和相关计算方法。最后对某两种船型的液舱进行基本结构设计,并对设计结果进行了强度校核。     

UUV用锂二氧化锰电池

介绍了UUV用锂二氧化锰电池的工作原理,进行了放电性能试验及安全性试验。结果表明,锂二氧化锰电池具有高比能、长贮存寿命、免维护以及较好的安全性,是新一代UUV电源的理想选择。     

Cooling effect of methanol on an n-heptane HCCI engine using a dual fuel system

Homogeneous charge compression ignition (HCCI) engines have the potential to raise the efficiency of reciprocating engines during partial load operation. However, the performance of the HCCI engine at high loads is restricted by severe knocking, which can be observed by the excessive pressure rise rate. This is due to the rapid combustion process occurring inside the cylinder, which does not follow the flame propagation that is seen in conventional engines. In this study, a low compression ratio of 9.5:1 for a gasoline engine was converted to operate in HCCI mode with the goal being to expand the stable operating region at high loads. Initially, pure n-heptane was used as the fuel at equivalence ratios of 0.30 to 0.58 with elevated intake charge temperatures of 180 and 90 °C, respectively. The n-heptane HCCI engine could reach a maximum performance at an indicated mean effective pressure (IMEP) of 0.38 MPa, which was larger than the performance found in the literature. To reach an even higher performance, a dual-fuel system was exploited. Methanol, as an anti-detonant additive, was introduced into the intake stream with various amounts of n-heptane at fixed equivalence ratios in the range of 0.42 to 0.52. It was found that the methanol addition cooled the mixture down prior to combustion and resulted in an increased coefficient of variation (COV). In order to maintain stable combustion and keep the pressure rise rate below the limit, the intake charge temperature should be increased. Introduction of 90% and 95% (vol/vol) hydrous methanol showed a similar trend but a lower thermal conversion efficiency and IMEP value. Therefore, a dual fuel HCCI engine could maintain a high thermal conversion efficiency across a wide load and enhance a 5% larger load compared to a pure n-heptane-fuelled HCCI engine. The hydrocarbon (HC) and carbon monoxide (CO) emissions were lower than 800 ppm and 0.10%, respectively. They were less at higher loads. The nitrogen oxides (NO _x ) emissions were below 12 ppm and were found to increase sharply at higher loads to a maximum of 23 ppm.     

农村公路养护管理评价指标体系研究

农村公路养护管理评价体系是一个多维的系统,不仅要对道路养护技术水平进行评价,也需要对日常养护水平、安全畅通、路网质量等要素进行综合评价。文中综合考虑了影响农村公路养护管理的各要素,建立了包含目标层、准则层、指标层的三级农村公路养护管理评价指标体系,并提出了农村公路养护管理评价实施的逻辑过程,即养护管理要素评价-养护要素预测-养护决策。     

汽车排气系统动态响应特性及强度分析

摘要：汽车排气系统的振动是影响汽车振动噪声和舒适度的主要因素之一,掌握其动态特性对优化汽车的NVH性能十分重要。在某客车新型排气系统的开发过程中,采用有限元分析方法,对排气系统进行模态、频率响应和强度分析,考察排气系统的整体性能,为排气系统的结构设计提供依据。     

基于层次分析法的新能源汽车驱动技术评估

利用层次分析法,分析了影响汽车制造商批量生产新能源汽车的关键因素,提出了不同层次的评估指标,建立了制造商对各类新能源汽车驱动技术的评估模型.对3种有望未来引进中国量产的国外新能源汽车进行动态评估,预测出未来20年其量产的趋势.     

汽车动力总成悬置系统优化与试验研究

以某款国产汽车为研究对象,在ADAMS中建立动力总成悬置系统的动力学模型。利用参数化分析方法,讨论了悬置参数对系统隔振性能的影响。对悬置参数进行优化,并分析比较优化前后的结果,优化后的悬置系统的隔振效果得到明显改善,并进行实车试验验证。     

基于观测器的半主动悬架仿真和实车控制

基于Kalman滤波算法设计了一个状态观测器,利用测得的簧载和非簧载质量加速度信号估计半主动悬架的簧载质量绝对速度以及簧载和非簧载质量之间的相对速度,并且基于这两个速度构建了天棚控制策略.仿真和实车试验表明,该状态观测器能较准确地估计这两个速度信号;与被动悬架相比,天棚控制有效提高了悬架的平顺性.