timing and the fuel injection timing so that the optimum performance can be obtained for each load and application through an electronic control mechanism. MHI has started development of an electronic system for the engine at an early stage and completed a camshaft-less engine with an electronic exhaust valve system and fuel injection system in December 1989. Since then, MHI has sought effective test methods and accumulated expertise in electronic control. Fig.7 summarizes the key concepts of the electronic engine.
3.4 Technology for reliability improvement
1) Analysis of main bearing characteristics
After failures and damage occurring in the main bearing of large UE engines, 2 years were devoted to resolving this problem. The causes were identified as movement of the problem. The causes were identified as movement of the crankshaft in the super-long stroke engine during operation, deformation of the bed plate that supports the bearing, and deformation of the bearing including the bearing cap. When the problem first occurred, these areas had not been fully clarified. To prevent such problems in the future, MHI has accumulated data and engineering know-how through measurements from the actual engines. In addition, MHI has also developed many analysis technologies for use in the review of improved bearings and the design of new bearings.
The development of these analysis technologies started from an accurate estimation of crankshaft movement, which was achieved by means of highly accurate analysis of shaft center movement. Considering the movement of the crankshaft and the bearing rigidity, oil film pressure and oil film thickness were calculated using the newly developed EHL analysis method for 3D offset contact variable load bearing. Figs.8 and 9 show the calculations of the shaft center locus with this analysis and the calculations of the locus with the conventional analysis. Fig.10 shows the calculations of the bearing oil film pressure.
*EHL (Elastic Hydrodynamic Lubricating)
4. New UEC series engine
Currently 3 series of UE engines are available: the LA series with short stroke, the LS series with long stroke, and the LSII series with super-long stroke. LA series engines are mainly used for car carriers, refrigerated cargo carriers, and container ships requiring high engine revolution. LSII series engines are mainly used for VLCC requiring low engine revolution. Engines are selected to meet the needs of each type of ship. Fig.11 shows the relationship between the output range and the revolution of the engine for each series.
1) UE C37 LSII and UEC 43LSII engines
These models were developed after the UEC37 LA and the 45 LA engines, which are widely used for various types of vessels including small cargo ships. Development of these models has completed the series of UEC LSII engines. The output range of the UEC-LSII series is from 1670 PS to 63,000 PS. Table 1 shows the main engine particulars. Fig.12 shows the structural features of each engine.
