Recent years have seen prodigious advances in marine Diesel performances. Mean effective pressures and piston areas have been doubled. Special care had to be devoted to all components subject to high mechanical and thermal loads, which on account of this could not be designed to simple similarity laws only. Despite of boosted outputs, it has proved possible to increase the safety margins of these components. By employing up-to-date computers, the stressing imposed on complicated parts like cylinder covers, pistons and liners can be ascertained (FE program). Where the geometry is to be optimized by variation, special computer procedures consuming less time are used (shell program). A surprising agreement between calculation and measurement was revealed by extensive stress measurements - some of them on engines in operation. On this basis the stresses, strains and deformations of new designs can be predicted with great reliability. More experience must be acquired to provide a better understanding of the thermal stresses arising in practical operation during transient and irregular operating conditions. Unfortunately, a knowledge of all stresses encountered will by no means solve all the problems, because the behavior of the material must be taken into account when judging these stresses. For example, relatively little is known as yet about the combined effect of high cycle fatigue caused by pulsating mechanical stresses and low-cycle fatigue due to thermal strains. And corrosion fatigue is another subject of importance to internal combustion engines on which the available data are still far from being complete. Manufacturing processes - in this case foundry techniques in particular - have got to be brought into line with the exacting requirements. Material quality must be guaranteed by adequate inspection procedures. The responsible designer will weigh the theoretically ascertained stresses against the practical experience gathered from engines in service. This will enable positive as well as negative experience to be comprehended much more accurately, so that theory can be applied purposefully to future designs, enhancing operational reliability in spite of the increased outputs.
Large diesel engines. Development of cylinder covers, pistons and liners
Die spezifischen Probleme bei der Entwicklung großer Dieselmotoren
1971
34 Seiten, 27 Bilder, 7 Quellen
Conference paper
Storage medium
English
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