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Two analysis procedures of the crankshaft stress are introduced. One is the conventional method which is very efficient as a model of simple beam at initial design stage within short time. For this analysis bending and torsion are considered as loadcases that are subjected to cyclic variation. The other is the detail Finite Element Analysis which is taken into account of load conditions due to the complex crankshaft dynamic behaviors. From the analysis, the natural frequencies in torsion and bending of the crankshaft as well as with the associated mode shapes and the maximum moments are calculated. The maximum moments are used in FE analysis as loadcases. The model is completed using solid linear elements with some special elements. The application of the FE method for the crankshaft stress analysis has advantage as it directly supplies the locations and level of maximum stresses, even though this method reqiures exact boundary conditions and spending much time in calculation.

Recently, high speed direct injection (HSDI) diesel engines are rapidly expanding their application to passenger cars and light duty commercial vehicles in western European market and other countries such as Korea and Japan. These movements are strongly backed by the technological innovations in the area of air charging and high pressure fuel injection systems. Variable geometry turbine (VGT) turbocharger, which could overcome the typical weak point of the existing turbocharged engine, and the common rail fuel injection system, which extended the flexibility of fuel injection capability, became two of the most frequently referred keywords in recent HSDI technology. In this paper some aspects of VGT potential as a full load torque and power modulator will be discussed. Possibility to utilize the portion of full load potential in favor of part load emissions and fuel economy will be investigated.

This paper describes the development process and test results of the lean burn engine. LML (Lean Misfire Limit) extension and NOx emission reduction was realized in combination with the following factors. (1) Installing several types of SCV (Swirl Control Valve) with different section shapes and dividing wall in the intake port intensified the flow field inside combustion chamber, so optimized mixture formation and combustion improvement were obtained. (2) By precisely controlling injection timing, changing injection rate, thus obtaining locally stratified charging, LML was extended. (3) By intensifying ignition system, better combustion characteristics were achieved. (4) NOx emission was reduced by extending LML and adopting lean NOx catalyst (Cu-ZSM-5). By combining above factors, we extended LML to A/F 23. Therefore NOx emission was reduced 60.6%, fuel economy was improved 10.6% in engine dyno test. BY ECU mapping test, we fixed lean operating zone.