Thermal Displacement of Crankshaft Axis of Slow-Speed Marine Engine

Abstract

UDC 629.5(05):621. 436 Original scientific paper SummaryThe paper presents analysis of displacement of a crankshaft axis caused by temperature of marine, slow-speed main engine. Information of thermal displacement of a power transmission system axis is significant during a shaft line alignment and a crankshaft springing analysis. Warmed-up main engine is a source of deformations of an engine body as well as a ship hull in the area of an engine room and hence axis of a crankshaft and a shaftline. Engines' producers recommend the model of parallel displacement of the crankshaft axis under the influence of an engine heat. The model gives us the value (one number!) of the crankshaft axis displacement in the hot propulsion system's condition. This model may be too simple in some cases. Presented numerical analyses are based on temperature measurements of the main engine body and the ship hull during a sea voyage. The paper presents computations of MAN B&W K98MC type engine (power: 40000 kW, revolutions: 94 rpm) mounted on 4500 TEU container ship (length: 290 m). Propulsion system is working in nominal, steady-state conditions; it is the basic assumption during the analyses. Numerical analyses were preformed with usage of Nastran software based on Finite Element Method. The FEM model of the engine body comprised over 800 thousand degree of freedom. Stiffness of the ship hull (mainly double bottom) with the foundation was modelled by a simple cuboid. Material properties of that cuboid were determined on the base of separately performed calculations.

Marine Propulsion System Failures—A Review

“…Engine crankshafts are subjected to bending, stretch-compression, and torsional dynamic loads. Thermal displacement (caused by normal engine working conditions) of the crankshaft [44] and thermal interaction between main engine body and ship hull [45] are other sources of variable loads acting on power transmission system. Therefore, the crankshafts are prone to fatigue failures under multiaxial loading.…”

Common failures of ship propulsion shafts

“…Proper shaft line alignment is very important in order to avoid vibration load generation. Thermal loads gener-ated in the main engine can produce misalignments in the engine shaft [16,17] what, in turn, produces vibrational load to the propeller shaft. Existing engines producers' thermal deformation models may be too simple to cover the entire temperature span an engine experiences during exploitation, so the need for specialized software arises [18].…”

Analysis of the Possibility of Using Acoustic Emission for Monitoring Technical Condition of the Fuel Injector in 3AL25/30 Engine

“…Fuel injectors are exposed to destruction processes during their operation (Bejger & Drzewieniecki, 2015). Monitoring the technical condition of machines and devices is very important especially for marine applications (Murawski, 2017). One of the methods used for monitoring fuel injection process is the acoustic emission (AE) method (Dykas & Harris, 2017).…”