Journal movement behavior in main bearing of 2-stroke marine diesel engine (1st report a principal theoretical analysis method)

摘要

Journal movement theoretical analysis method is proposed which can be used to analyze journal movement behavior in main bearing of low speed 2-stroke marine diesel engine for practical usage. For proposing the method, crankshaft is idealized by a set of jointed structures consisting of simple round rods and simple beam blocks of rectangular cross section. The main bearings were idealized by linear spring support. Mobility method of short bearing theorem is used to calculate the journal bearing lubrication as an easy method. In order to solve by combining dynamical crankshaft behavior with journal bearing lubrication transfer matrix method is applied. Then the journal movement such as journal center locus and journal tilts is calculated. An application example of the method is carried out by a 7-cylinder diesel engine. Journal center loci and journal tilts are also measured with 4 main bearings in an actual 7-cylinder diesel engine. The analyzed results are good correspondence with measured 4 journal results under full loaded condition. The method is also confirmed to be able to simulate faithfully journal movement behavior under several engine loaded condition. Finally, the validity of the method for practical usage is confirmed.