Experimental investigation of characteristics of pressure modulation in a fuel injection system

A piezoelectric atomization device achieves fuel pressure modulation through vibration of a piezoelectric pressure modulator. As a consequence, the fast alternating and slow moving streams collide with each other and further break up the fuel drop. In this paper, an experimental investigation was carried out to study the fluid dynamic characteristics of the spray atomization process of automotive port fuel injectors with a piezoelectric pressure modulator. The investigation mainly focuses on: (a) the coupling characteristics between the piezoelectric stack and the hydraulic as well as the transfer characteristics of pressure modulation from the piezoelectric modulator to the point above the orifice; (b) the time history of the pressure dynamic response at the point above the orifice under a typical modulation frequency, which reflects the variation of pressure modulation while the fuel injector is working; and (c) the time-variation characteristics related to mechanical structure and fluid dynamics. The experimental results expose some important dynamic characteristics of pressure modulation, which will be very significant and lead us to greatly improve the fuel injection system, optimize the control parameters and implement spray atomization with a high quality performance in the near future.     

Investigation of the shear flows over a sunroof opening based on a linear inviscid instability analysis

The large-scale shear flows over the sunroof opening of a mid-sized SUV measured using a PIV system were investigated. The shear flows were measured for five different cases of deflector protrusion (one case was the baseline test without deflector) at two different free stream flow velocities below the critical velocity where the buffeting noise level reached a maximum. The structures of the shear flows were observed to differ, apparently depending on whether the radiated buffeting noise is relatively strong or not. For strongly buffeting experimental cases, the momentum thicknesses of the shear layers were observed to grow rapidly and saturated at a station near the downstream edge of the sunroof opening, where the saturation of the transverse velocity fluctuations was also observed, and where the vortex coalescence process was presumably completed. On the other hand, no discrete large-scale vortex structures were observed for none-buffeting or weakly buffeting cases. Streamwise growth of the velocity fluctuations was found to be well predicted by a linear hydrodynamic instability analysis for the strongly buffeting cases. Numerical results obtained from a linear inviscid instability analysis using a hyperbolic tangent mean velocity profile were used to calculate the amplification factors with the initial momentum thickness and the streamwise fluctuation wavenumber. The shear flows were found to form large-scale discrete vortices when the linear inviscid amplification factors exceeded a threshold amplification factor.     

Modeling gas dissolution in deepwater oil/gas spills

Gases in deepwater oil/gas spills can lose considerable amounts of the gas phase due to dissolution in water. Gas dissolution has a significant impact on the behavior of the oil/gas jet/plume because of its impact on the buoyancy. A method is presented in this paper for computing gas dissolution that covers a broad range of water depth, from shallow water where gases behave as ideal ones under low pressure to deepwater where gases behave as non-ideal ones under high pressures. The method presented also accounts for the spherical and non-spherical shapes of gas bubbles. The gas dissolution computations are validated by comparing the computed results with observed data from previously conducted laboratory experiments. The gas dissolution computation module is then integrated with a model for underwater oil/gas jets/plumes by Yapa and Zheng [J. Hydraul. Res. 35 (5) (1997) 673]. Scenario simulations are presented to show the impacts of gas dissolution on the behavior of jets/plumes. These scenarios show the impact of dissolution on the behavior of the jet/plume. The comparison of results using ideal gas conditions and non-ideal gas conditions is also shown.     

Geographic information system design for network equilibrium-based travel demand models

Travel demand analyses are useful for transportation planning and policy development in a study area. However, travel demand modeling faces two obstacles. First, standard practice solves the four travel components (trip generation, trip distribution, modal split and network assignment) in a sequential manner. This can result in inconsistencies and non-convergence. Second, the data required are often complex and difficult to manage. Recent advances in formal methods for network equilibrium-based travel demand modeling and computational platforms for spatial data handling can overcome these obstacles. In this paper we report on the development of a prototype geographic information system (GIS) design to support network equilibrium-based travel demand models. The GIS design has several key features, including: (i) realistic representation of the multimodal transportation network, (ii) increased likelihood of database integrity after updates, (iii) effective user interfaces, and (iv) efficient implementation of network equilibrium solution algorithms.     

Modelling dual carriageway lane changing using neural networks

Neural networks offer a potential alternative method of modelling driver behaviour within road traffic systems. This paper explores the application of neural networks to modelling the lane-changing decisions of drivers on dual carriageways. Two approaches are considered. The first, preliminary approach uses a prediction type of neural network with a single hidden layer and the back propagation learning algorithm to model the behaviour of an individual driver. A series of consecutive time-scan traffic patterns, which describe the driver's environment and changes over time as the selected vehicle travels along a link, are input to the neural network, which then predicts the new lane and position of the vehicle. Training data are collected from a human subject using an interactive driving simulation. The trained neural network successfully exhibited the rudiments of driving behaviour in terms of lane and speed changes. A major disadvantage of this approach was the difficulty in recording real-life data, which are required to train the neural network, for individual drivers. The second approach concentrates specifically on lane changing and makes use of a learning vector quantization classification type of neural network. Input to the neural network still consists primarily of time-scan traffic patterns, but the format is changed to facilitate the possibility of data acquisition using image processing. The neural network output classifies the input data by determining the new lane for the vehicle concerned. Performance in both testing and training was very good for data generated by the rule-based driver-decision model of a microscopic simulation. Performance in testing was less satisfactory for data taken directly from a road and highlighted the need for extensive data sets for successful training.     

Air itinerary shares estimation using multinomial logit models

ABSTRACT

The main goal of this study is the development of an aggregate air itinerary market share model. In order to achieve this, multinomial logit models are applied to distribute the city-pair passenger demand across the available itineraries. The models are developed at an aggregate level using open-source booking data for a large group of city-pairs within the US air transport system. Although there is a growing trend in the use of discrete choice models in the aviation industry, existing air itinerary share models are mostly focused on supporting carrier decision-making. Consequently, those studies define itineraries at a more disaggregate level using variables describing airlines and time preferences. In this study, we define itineraries at a more aggregate level, i.e. as a combination of flight segments between an origin and destination, without further insight into service preferences. Although results show some potential for this approach, there are challenges associated with prediction performance and computational intensity.     

Railway Vehicles with Perfect Curving Behaviour Which are Asymptotically Stable at Vanishing Speed

Paper deals with the linear behaviour of a railway vehicle with any arbitrary number of wheelsets, body parts and connecting elements. A vehicle which has both perfect curving properties and asymptotical stability at vanishing speed, has to satisfy a twofold condition, indicated by Wickens in 1978. In the present paper this condition is derived in reliance upon the dimension theorem for linear mappings. How the investigation can be executed in practice, is shown for the case of a two-axled vehicle. At last the behaviour in a transition curve is discussed.     

A Theoretical Analysis of the Ride Vibration of Agricultural Tractor and Trailer Combinations

A six degree of freedom model of an agricultural tractor and trailer combination has been developed. Results from eigenvalue and frequency response calculations indicated that tractor operator vibration levels will be higher when operating with a trailer than for the tractor alone, due mainly to increased tractor pitch motion.

Although minor improvements could be made to present tractor and trailer combinations by moving the hitch forward of the tractor rear axle or providing some damping at a sprung hitch, the scope for a significant improvement in ride lies in changing the configuration. If higher speed specialised transport vehicles prove economical for agriculture, there are some advantages in ride vibration to be gained by changing the layout of the tractor and trailer combination to resemble an off-road version of a commercial articulated lorry.     

Application of Chinese Characters in the Design and Construction of the Badaling Great Wall Station of the Beijing-Zhangjiakou High-Speed Railway北大核心CSCD

The new Badaling tunnel is the longest tunnel on the under-construction Beijing-Zhangjiakou highspeedrailway, with the Badaling Great Wall station to be built in the tunnel. This station, which is under the Badaling Great Wall historic site, is the world’s largest underground high-speed railway station with the most complicated structure and the largest overburden and excavation area. It is therefore a representative project for China’s highspeed railway development strategy, supporting infrastructure facilities for the Beijing Horticultural Expo 2019 and the 2022 Winter Olympics in Beijing, and it is important that it be of high quality and completed safely. In the de-sign and construction of the station, the glyphs of the Chinese characters of "中",”国”,”人”and”品”are used, re-spectively, along the station route, in the rescue and evacuation mode, auxiliary adit and partial excavation, which is a way to successfully integrate the art of Chinese characters into tunnel engineering. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

On-board aging estimation using half-cell voltage curves for LiFePO<Subscript>4</Subscript> cathode-based lithium-ion batteries for EV applications

The aim of this work is the design of an algorithm for on-board determination of the actual capacity of a lithium iron phosphate (LFP) cathode-based lithium-ion battery for electric vehicle applications. The presented approach is based on the detection of the predominant aging mechanisms (in terms of loss of lithium and loss of active material in both electrodes) by determining the single electrode voltage curves. The information related to the characteristic length and position of the voltage plateaus, which can be gathered during battery operation, can be used to obtain the actual aging state of the cells. The length of the plateaus depends on the respective position that the voltage curves of the single electrodes have in relation to each other. Relating the change of the plateau characteristics to the possible aging mechanisms allows the determination of the actual battery aging state in terms of total cell capacity. The work presents a possible implementation of an algorithm for capacity determination based on the described methodology. The algorithm is validated with various differently aged LFP cells. Furthermore, the work discusses the ability of the method to detect the actual battery capacity if the characteristics of only part of the quasi-OCV (open circuit voltage) curve are detected. Achieved accuracy and existing limitations are described and discussed in detail.