Effects of intake flow on the spray structure of a multi-hole injector in a DISI engine

The spray characteristics of a 6-hole injector were examined in a single cylinder optical direct injection spark ignition engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure, and coolant temperature were investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played a major role in the fuel spray distribution during the induction stroke while injection timing had to be carefully considered at high injection pressures during the compression stroke to prevent spray impingement on the piston.     

Strategies for improving the mode transition in a sequential parallel turbocharged automotive diesel engine

Parallel sequential turbocharging systems are able to operate in different modes, which are defined according to the turbochargers that simultaneously boost the engine, and are controlled by means of specific valves. In order to cover the full engine operating range, a smooth transition between turbocharging operating modes must be ensured. However, important disturbances affect both boost and exhaust pressure when shifting the operation mode, thus causing non-negligible torque oscillations. This paper presents different methods for smoothing such undesirable effects during mode transition. Strategies covering optimal synchronization of the control valves, control of the valves’ position, and correction of the injected fuel during the transition are analysed. A fully instrumented passenger car engine is used for illustrating the different torque smoothing methods, and experimental results for transitions during both steady operation and engine accelerations are shown.     

Development of a knowledge-based hybrid failure diagnosis system for urban transit

Urban transit is a complex system that contains both electrical and mechanical entities; therefore, it is necessary to construct a maintenance system for ensuring safety during high-speed driving. Expert systems are computer programs that use numerical or non-numerical domain-specific knowledge to solve problems. This research aims to develop an expert system that diagnoses the causes of failures quickly and displays measures to correct them. For the development of this expert system, the standardization of a failure code classification and the creation of a Bill of Materials (BOM) were first performed. Through the analysis of both failure history and maintenance manuals, a knowledge base has been constructed. Also, for retrieving the procedure of failure diagnosis and repair linking with the knowledge base, we have built a Rule-Based Reasoning (RRB) engine with a pattern matching technique and a Case-Based Reasoning (CBR) engine with a similar search method. Finally, this system has been developed as web based in order to maximize accessibility.     

北美铁路经历的车轴故障

对北美铁路重载货车的车轴故障、车轴疲劳试验和车轴应力进行了研究,并介绍了几种解决车轴故障的措施.     

Nature of influence of out‐of‐vehicle time‐related attributes on transit attractiveness: a random parameters logit model analysis

This paper describes the nature of the impacts of walking distances and waiting time on transit use. The relative trade‐offs of walking and transfer components with other transit service attributes are also discussed. A total of 449 completed stated‐preference interviews were collected; with six observations from each respondent, the total number of observations was 2694. This data set was used to estimate the coefficients in different utility functions using a random parameters logit model. The results demonstrated that walking distances to and from transit stops have important and significant nonlinear negative influences on the attractiveness of transit. Transfer waiting time was also shown to have a significant nonlinear negative impact on transit attractiveness. The random parameters logit model had a better model fit than the standard logit model. Some of the findings obtained here are novel, while others are consistent with previous works. These findings have implications for both theory and practice. Copyright © 2014 John Wiley & Sons, Ltd.     

Bayesian committee of neural networks to predict travel times with confidence intervals

Short-term prediction of travel time is one of the central topics in current transportation research and practice. Among the more successful travel time prediction approaches are neural networks and combined prediction models (a ‘committee’). However, both approaches have disadvantages. Usually many candidate neural networks are trained and the best performing one is selected. However, it is difficult and arbitrary to select the optimal network. In committee approaches a principled and mathematically sound framework to combine travel time predictions is lacking. This paper overcomes the drawbacks of both approaches by combining neural networks in a committee using Bayesian inference theory. An ‘evidence’ factor can be calculated for each model, which can be used as a stopping criterion during training, and as a tool to select and combine different neural networks. Along with higher prediction accuracy, this approach allows for accurate estimation of confidence intervals for the predictions. When comparing the committee predictions to single neural network predictions on the A12 motorway in the Netherlands it is concluded that the approach indeed leads to improved travel time prediction accuracy.     

Hybridation of generation propagation models and SPH model to study severe sea states in Galician Coast

The Atlantic and Cantabrian coasts of the Iberian Peninsula suffer the periodic passage of storms which give rise to severe sea states. Standard generation- propagation models (WAM, WAVEWATCH, SWAN) are commonly used for operational oceanography purposes with satisfactory results both in the open ocean and in near shore areas but they do not provide information about the possibility of flooding in coastal areas. A 2D HV version of SPH (Smoothed Particle Hydrodynamics) model is considered to propagate the signal provided by generation- propagation models to the coast and to analyze the nature of coastal structures overtopping as a tool to create maps of risk. SPH is shown to provide valuable information about overtopping (maximum water height and water velocity) under the stormy conditions suffered by the Galician coast on February 17, 2006.     

交通方式可达性差距——衡量交通可持续发展的指数

交通因其消耗大量能源而在可持续发展中扮演着重要角色,为了规划交通可持续发展,有必要提出能够评估和衡量交通可持续发展的指数。利用可达性概念和地理信息系统提出交通方式可达性差距指数。该指数由人口数量、就业岗位数、商店数以及学校数等决定,根据公共交通方式和私人交通方式间可达性指数差异计算。就能源效率而言,公共交通方式比私人交通方式更能实现可持续。可达性差距指数越高意味着可持续能力越强。通过比较香港1991年和1996年的可达性差距指数,来检验交通发展的可持续性是否有所提升。最后,讨论了如何运用可达性差距指数来检验土地利用以及交通发展政策和方案,以便确定更可持续的政策和方案。     

Low temperature premixed combustion within a small bore high speed direct injection (HSDI) optically accessible diesel engine using a retarded single injection

An optically accessible single-cylinder high speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail injection system was used to study low temperature Modulated Kinetics (MK) combustion with a retarded single main injection. High-speed liquid fuel Mie-scattering was employed to investigate the liquid distribution and evolution. By carefully setting up the optics, three-dimensional images of fuel spray were obtained from both the bottom of the piston and the side window. The NOx emissions were measured in the exhaust pipe. The influence of injection pressure and injection timing on liquid fuel evolution and combustion characteristics was studied under similar fuel quantities. Interesting spray development was seen from the side window images. Liquid impingement was found for all of the cases due to the small diameter of the piston bowl. The liquid fuel tip hits the bowl wall obliquely and spreads as a wall jet in the radial direction of the spray. Due to the bowl geometry, the fuel film moves back into the central part of the bowl, which enhances the air-fuel mixing process and prepares a more homogeneous air-fuel mixture. Stronger impingement was seen for high injection pressures. Injection timing had little effect on fuel impingement. No liquid fuel was seen before ignition, indicating premixed combustion for all the cases. High-speed combustion video was taken using the same frame rate. Ignition was seen to occur on or near the bowl wall in the vicinity of the spray tip, with the ignition delay being noticeably longer for lower injection pressure and later injection timing. The majority of the flame was confined to the bowl region throughout the combustion event. A more homogeneous and weaker flame was observed for higher injection pressures and later injection timing. The combustion structure also proves the mixing enhancement effect of the liquid fuel impingement. The results show that ultra-low sooting combustion is feasible in an HSDI diesel engine with a higher injection pressure, a higher EGR rate, or later injection timing, with little penalty on power output. It was also found that injection timing has more influence on HCCI-like combustion using a single main injection than the other two factors studied. Compared with the base cases, simultaneous reductions of soot and NOx were obtained by increasing EGR rate and retarding injection timing. By increasing injection pressure, NOx emissions were increased due to leaner and faster combustion with better air-fuel mixing. However, smoke emissions were significantly reduced with increased injection pressure.     

Assessing the impacts of driving environment on driving behavior patterns

Transportation - Considering the role of behavioral and environmental factors on road accidents and traffic intensities, the characterization of vehicle use and driver behavior opens new...