Effects of stack array orientation on fuel cell efficiency for auxiliary power unit applications

The commercial fuel cell products currently appearing on the market are self-contained fuel cell engines. These engines can be used for many applications that are presently dominated by internal combustion engines or batteries. Vehicle mounted fuel cell auxiliary power units have been attracting attention lately. Additionally, there is a market based incentive to use multiple small fuel cell arrays in place of a single large fuel cell for some applications. Typically, fuel cells are designed to operate as stand-alone units. This paper investigates the ability of small commercial stacks to operate in common array arrangements. Although an individual Nexa is able to produce 1500 W, Dual Nexas do not maintain that capability while in array configurations. With an overall load share ratio of 1.02:1 the series array reliably produced 2900 W of power, while with an overall load share ratio of 1.09:1 the parallel array reliably produced only 2800 W of power. This study shows that array orientation affects both system stack net efficiency and individual stack net efficiency. The information gained from this study may be helpful for fuel cell design and integration.     

Optimizing the transportation of international container cargoes in Korea

This paper considers a multimodal transportation problem, which is the problem of determining the transportation flow, i.e. volume of container cargoes, and the transportation mode in each trade route, for the objective of minimizing the sum of shipping and inland transportation costs. The problem takes account of two restrictions: maximum cargo volumes capacitated at each seaport and maximum number of vehicles available at each transportation mode. To solve optimally the problem, this paper employs a mixed integer programming, which is an operations research technique. A case study is performed on the container cargo data in Korea and we draw several implications to improve efficiency in the transportation of international trade cargoes in Korea.     

Objective evaluation of the sound quality of the warning sound of electric vehicles with a consideration of the masking effect: Annoyance and detectability

This study developed a method to evaluate the sound quality of the warning sound masked by background noise considering the masking effect. The warning sound of an electric vehicle is required by law for the safety of pedestrians. Therefore, the warning sound becomes an additional noise pollution source if it is designed as an annoyance. On the other hand, if the sound is designed with a low sound pressure level, pedestrians will not recognize the approach of vehicle due to background noise. To avoid nose pollution and permit the detectability of an approaching vehicle, a method for evaluating the annoyance and detectability of an electric vehicle is required. In this paper, the whine index evaluating the whine sound masked by the background was developed and used as a sound metric. This metric was employed for the development of an annoyance index and detectability index for electric vehicles.     

Impact of electric vehicles on existing car usage: A mixed multiple discrete–continuous extreme value model approach

This study investigates how the introduction of electric vehicles may influence the usage of existing cars. A survey of 250 households in South Korea is used to analyze a future automobile market that includes electric vehicles taking into account the heterogeneity of consumer preferences and usage patterns. Based on consumer preferences, the future market share of various vehicles is estimated and the impact of promoting the usage of electric vehicles by government subsidization and tax incentives is analyzed.     

Assessment of an engine cylinder head-block joint using finite element analysis

An engine cylinder head-block joint is a gasketed, bolted joint. Assessment of sealing performance and fatigue durability of the joint during engine development relies entirely on the engine dynamometer test because the rig test cannot mimic the engine run condition and finite element analysis employs gasket and bolt models that are too simple to provide the stress data for fatigue assessment. This paper introduces finite element-based assessment of the gasket and the bolt and a model that improves the analysis accuracy without increasing computation time. Experimental data for the deformation of joint members under thermo-mehanical load are presented to demonstrate the accuracy of the model.     

Special provisions for left turns at signalized intersections to increase capacity and safety

Heavy left-turns at intersections are not only difficult to accommodate but also often cause traffic accidents. Such problem can be reduced by adopting an exclusive left-turn signal phase, but in this case the cycle length needs to be extended and the overall intersection capacity reduced. This problem is particularly important in such countries as Korea where unprotected left turns are rarely used. Innovative intersection designs and operational methods for avoiding these problems are presented and their effects of increasing capacity and reducing vehicle delay are analyzed. They rule out the requirement for exclusive left-turn phase while accommodating a large volume of left-turns quite safely.     

Hydro- and aerodynamic analysis for the design of a sailing yacht

The results of the design analysis for a sailing yacht’s hull and sails are reported. The results were used to confirm the design of a 30 ft long sloop, which was planned, designed, and built in Korea for the first time in history. Flows around a sailing yacht above and under the free surface were analyzed separately using both computational and experimental methods. For the underwater flow analysis, turbulent flow simulations with and without free surface wave effects were carried out for the canoe hull with keel/rudder. The computed drag and side forces on the hull model were compared with the measurement data obtained from the towing tank experiments. In order to assess the sail performance, another set of computations was carried out for the flow around a sail system composed of main and jib sails with a mast. The present study demonstrates that, for the design analysis of a sailing yacht, computational fluid dynamics techniques can be utilized with a reasonable level of confidence.