Application of a modified thermostatic control strategy to parallel mild HEV for improving fuel economy in urban driving conditions

A modified thermostatic control strategy is applied to the powertrain control of a parallel mild hybrid electric vehicle (HEV) to improve fuel economy. This strategy can improve the fuel economy of a parallel mild HEV by operating internal combustion engine (ICE) in a high-efficiency region. Thus, in this study, experiments of a parallel mild HEV were conducted to analyze the characteristics of the hybrid electric powertrain and a numerical model is developed for the vehicle. Based on the results, the thermostatic control strategy was modified and applied to the vehicle model. Also, battery protection logic by using electrochemical battery model is applied because the active usage of battery by thermostatic control strategy can damage the battery. The simulation results of the vehicle under urban driving conditions show that the thermostatic control strategy can improve the vehicle’s fuel economy by 3.7 % compared with that of the conventional strategy. The results also suggest that the trade-off between the fuel economy improvement by efficient ICE operation and the battery life reduction by active battery usage should be carefully investigated when a thermostatic control strategy is applied to a parallel mild HEV.     

Automobile aerodynamics influenced by airfoil-shaped rear wing

Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k-ε turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height.     

A Practical Model for Deformation Prediction of Highway Subgrade Soils

This paper reports a practical constitutive relation for highway subgrade soils. The proposed model is derived based on the laboratory repeated-load testing of four subgrade soils. Statistical parameters generally used in the power model of subgrade permanent strain are expanded into material constants with engineering significance. The constitutional relation reported in this paper can be used in the mechanistic-based pavement design of highway flexible pavements and railroad tracks.     

隧道三维激光扫描测算一体化技术方案与实践北大核心CSCD

三维激光扫描技术已在隧道工程中得到广泛应用,但其内外业脱节、人工操作过多、实时性不足等问题日益凸显。文章结合工程实践,提出三维激光隧道扫描测算一体化技术方案,通过隧道设计模型录入、坐标里程解算、点云自动过滤、点云降采样与地物分离等,对点云进行特征值提取,得到兼顾规模、精度、效率的点云数据模型;通过点云与设计、点云与点云的对比解算,得到隧道工程质量安全相关成果。该技术方案在某铁路隧道工程中进行实践,可将内外业工作总时间缩短至20 min以内,自动化程度高,成果精度好,具有很好的推广价值。     

Transport of radionuclides by sea-ice and dense-water formed in western Kara Sea flaw leads

A transport assessment of particle-bound and dissolved artificial radionuclides (¹³⁷Cs and ^239,240Pu) by sea-ice and dense-water formed in western Kara Sea flaw leads close to the Novaya Zemlya dumping sites is presented in this study. We both performed a “best estimate” based on available data, and a “maximum assessment” relying on simulated constant releases of 1 TBq ¹³⁷Cs and ^239,240Pu from individual dumping bays. The estimates are based on a combination of (i) the content of particulate matter in sea-ice; (ii) analytical data and numerical simulations of radionuclide concentrations in shelf surface deposits, suspended particulate matter (SPM), and the dissolved phase; and (iii) estimates of lead-ice and dense-water formation rates as well as modeling results of local ice drift pathways. In the “best estimate” case, 2.90 GBq ¹³⁷Cs and 0.51 GBq ^239,240Pu attached to sea-ice sediments can be exported from the lead areas toward the central Arctic basin. The radionuclide burden of the annually formed dense lead water in the “best estimate” amounts to 4.68 TBq ¹³⁷Cs and 0.014 TBq ^239,240Pu. In the “maximum assessment”, potential export-rates of ice-particle bound ¹³⁷Cs and ^239,240Pu toward the central Arctic would amount to 0.64 and 0.16 TBq, respectively. As much as ≈900 TBq ¹³⁷Cs and ≈6.75 TBq ^239,240Pu could be annually taken up by 34.75 dense-water rejected in the lead area. Assuming the (unlikely) instantaneous release of the total ¹³⁷Cs and ^239,240Pu inventories (≈1 PBq and 10 TBq, respectively) from the Novaya Zemlya dumping sites into the dissolved phase, the dense lead water locally formed during one winter season could take up ≈90% of the Cs and ≈68% of the Pu released.     

Overview of intelligent ship route optimization methods北大核心CSCD

智能船舶航线优化在学术界和工业界均受到越来越多的关注。针对智能船舶航线优化问题,从航线设计方法和航线优化算法这2个层面,分别阐述各种设计方法和优化算法的特点。结合近5年来的最新研究成果,在分析国内外智能船舶航线优化技术发展现状的基础上,将航线设计方法归纳为3种,即基于气象数据的航线优化、基于油耗模型的航线优化以及基于航线库或航路点库的航线优化,剖析其技术内涵及应用情况;深入分析改进的等时线法、动态规划法、图形搜索算法、智能算法、人工智能和机器学习算法的特性及不足,总结归纳将各类算法应用于智能船舶航线优化时存在的主要问题。最后,简要展望智能船舶航线优化的发展趋势,为未来在该领域的研究提供一定的思路。     

Windows CE操作系统在机车显示器上的应用研究

介绍Windows CE操作系统的特点,阐述了将嵌入式操作系统Windows CE应用在机车显示器上的整个开发过程,并对其应川结果进行了总结。     

20世纪美国应对机动性的交通构想及高速公路发展历程

为了阐述20世纪除汽车机动性外,交通发展经历的最重要的进程——城市高速公路的出现,考察了过去100年来美国城市交通规划的历史。通过回顾各种研究资料,认为资助州际公路发展所采用的方法使联邦和州公路工程师成为主管,这影响了公路的选线及设计。联邦公路工程师只关注机动车通过效率的最大化,而在很大程度上忽略了城市的其他利害关系。没有先进的规划理念指导、过度建设、稀疏、放射环状的道路网对于加强机动性取得了极大的效益,但通常要为此付出巨大的社会和环境成本。最后指出,在实践中要重新审视具有百年历史的协调交通与土地利用规划的观点,而且,公共财政权宜之计式的政治决策方式将对工程、出行和城市形态产生深远的影响。·     

Design and optimization of an LPG roller vane pump for suppressing cavitation

A roller vane type liquefied petroleum gas (LPG) pump was developed for a liquid phase LPG injection (LPLi) engine. Most of the LPG pumps used in the current LPLi engines are installed inside of the LPG tank, but this pump is intended to be installed outside of the LPG tank to overcome the difficulty of fixing an in-tank pump. Because LPG has a low boiling point and high vapor pressure, it usually causes cavitation in the pump and consequently deteriorates the flow rate of the pump. The purpose of this work is to optimize the design of the roller vane pump in order to suppress cavitation and increase the fuel flow rate by using a computational fluid dynamics (CFD) analysis. In order to achieve these goals, the intake port configuration and the rotor of the roller vane pump were redesigned and simulated using STAR-CD code. Computation was performed for six different models to obtain the optimized design of the roller vane pump at a constant speed of 2600 rpm and a constant pressure difference between the inlet and outlet of 5 bar. The computation results show that an increased intake port cross-section area can suppress cavitation, and the pump can achieve a higher flow rate when the rotor configuration is changed to increase its chamber volume. When the inlet pressure difference is 0.1 bar higher than the fluid saturation pressure, the pump reaches its maximum flow rate.     

Driver curve speed model and its application to ACC speed control in curved roads

A speed control algorithm for an ACC (Adaptive Cruise Control) system for curved roads is proposed based on driver behavior characteristics. As the foundation of this research, a driver speed model for curved roads is developed using a series of experimental data regarding driver behavior. To adapt the model to each driver’s individual curve speed behavior, the coefficients of the model are identified in real time from the data sequences collected during drivers’ manual operation stage by a self-learning algorithm based on a Recursive Least-Square (RLS) method with a forgetting factor. Using this algorithm, the parameters of the driver model can be identified from the data collected in the manual operation phase, and the identification results are applied during the ACC automatic control phase. Based on the developed model, the ACC speed control algorithm is modified to provide each individual driver with a customized speed profile for the scenario of a curved road with no car ahead. Tests verify the applicability of the modified system.