Numerical analysis of homogeneous mixture formation for a direct injection liquid LPG engine

A method to form a homogeneous mixture using low pressure direct injection of liquid phase LPG, pent-roof combustion chamber, flat-top piston and center-located injector layout is presented. To validate the method, the mixture formation processes in the cylinder were investigated using the CFD code. The effect of different injection timing and engine loads on the mixture formation processes were researched. The simulated results showed that, the intake tumble for high load conditions or the inclined intake swirl for part load conditions would break into small-scale vortex (turbulence) near the end of compression stroke, which enhanced the homogeneous mixture formation. The results also showed that if the liquid phase LPG was injected at 60–80°CA ATDC in intake stroke even at different loads, the homogeneous mixture would be formed under any engine load conditions.     

Review on characterization of nano-particle emissions and PM morphology from internal combustion engines: Part 2

This paper presents a review of the characterization of physical properties, morphology, and nanostructure of particulate emissions from internal combustion engines. Because of their convenience and readiness of measurement, various on-line commercial instruments have been used to measure the mass, number, and size distribution of nano-particles from different engines. However, these on-line commercial instruments have inherent limitations in detailed analysis of chemical and physical properties, morphology, and nanostructure of engine soot agglomerates, information that is necessary to understand the soot formation process in engine combustion, soot particle behavior in after-treatment systems, and health impacts of the nano-particles. For these reasons, several measurement techniques used in the carbon research field, i.e., highresolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy, were used for analysis of engine particulate matter (PM). This review covers a brief introduction of several measurement techniques and previous results from engine nano-particle characterization studies using those techniques.     

Research on the sound metric of door-slamming sound based on leaky integration and wavelet decomposition

The evaluation of the sound quality of door-slamming has become one of the important issues in vehicle noise, vibration and harshness (NVH) analysis. For the sound quality evaluation of door-slamming, a new sound metric, named as sound metric based on critical band wavelet decomposition (SMCBWD), is developed. In the new sound metric, the sound signals of door-slamming are sampled and the signal component of the door-slamming sound which has the great influence on the quality of door-slamming is extracted by using the leaky integration method. The extracted signal component is then decomposed by wavelets based on the critical bands and the coefficients of wavelet decomposition are calculated. Based on the energy of the frequency weighted wavelet decomposition coefficients, the new sound metric, SMCBWD, is calculated. In order to verify the effectiveness of SMCBWD, the correlation coefficients between the new sound metric and the subjective sound quality performance value of door-slamming, as well as between the traditional sound metrics (loudness, sharpness) and the subjective sound quality performance value of door-slamming have been calculated, respectively. The results show that the new sound metric developed in this paper has the higher correlations with the subjective sound quality performance value when compared with the traditional sound metric of loudness and sharpness. Thus, SMCBWD can be used to evaluate the sound quality of door-slamming more accurately.     

顶湖—仙渡345 kV地下输电线路工程设计与施工

因都会区用电量增加,且为减低输电线路对市区景观及环境冲击,台电公司于台北市北投区大度路旁兴建地下电缆洞道,由顶湖超高压变电所引入345 kV二回线至仙渡超高压变电所。采用潜盾工法以降低交通及环境冲击的问题,因施工遭遇软硬不同土层及高水压影响,且穿越捷运淡水线关渡隧道下方,紧邻大度陆桥,因此在设计上采用大洞道方案、2道止水条、发进井调整位置及角度等方案,以降低施工对于附近结构物之冲击。     

Extension of Newell's dispatching policy to the case of sensitive demand

This paper has extended Newell's dispatching policy to the case of sensitive demand which is characterized by a linear mode split model with two major factors, wait time and transit fare. Three objective functions both with and without vehicle capacity constraint are analyzed, including profit maximization, maximization of a combination of net user benefit and operator profit, and maximization of net user benefit subject to a deficit constraint. Closed-form solutions associated with various system parameters are obtained. It is shown that under sensitive demand conditions the optimal dispatching rate is approximately proportional to the square root of the total demand rate, if vehicle size is not binding and it is strictly proportional to the total demand rate, if vehicle size is binding.     

Containerization in Nigeria: trends and patterns

Containerization was introduced into Nigeria in the late 1960s, not through a delibrate policy but through the unilateral action of shipping companies.In spite of this,the percentage of the country's external trade cargo that is containerized grew from only about 0.03 in 1968-69 to about 8.6 in 1981.

Containerization of cargo is more significant in the import than in the export trade. Perhaps because of the capital-intensive nature of this technology, there is a concentration of containerization facilities in the ports of Lagos and Port Harcourt. Whereas this is a cost-efficient development, there are various inefficient aspects in the inland distribution of containers.     

适用于重载的滚动轴承

介绍了为增加货车轴重而开发的短轴承以及将短轴承进行标准化而遇到的问题。     

Vertical Vibration Analysis of Vehicle/Imperfect Track Systems

Summary This paper studies the vertical vibration of a vehicle traveling on an imperfect track system. The car body and sleepers are modeled as Timoshenko beams with finite length, and the rail is assumed as an infinite Timoshenko beam with discrete supports. Imperfection of the track system comes from a sleeper lost partial support by the ballast. Since deflection of the rail is limited within a certain interval where the vehicle is passing over, the infinite domain problem can be transformed into a finite domain problem with moving boundary. In this work, the equations of motion of the car body, rail and sleepers are discretized first by the finite element method. The discretized equations of motion for the vehicle and track systems are then assembled, respectively. Finally, the Newmark method is applied to obtain the response of the vehicle and track systems at each time step. The effect of the vehicle speed on the response of the vehicle and track systems is investigated.