Research On The Key Technology Of Marine Main Engine Crankshaft Deflection Difference Adjustment

With the increasing trend of ship size,the marine main diesel engine power is getting higher and higher,size and weight of crankshaft are also growing.The axis state of crankshaft that reflected by crankshaft deflection difference play a key role in the normal operation of crankshaft.Therefore,judging if crankshaft deflection difference is within reasonable range is very important to ensure the smooth operation of ship.Usually make crankshaft deflection difference within reasonable range by adjusting main engine base height based on worker's experience.So the research in this paper,which is about the key technology of crankshaft deflection difference adjustment,have a certain industry application value.This paper takes the crankshaft deflection difference of a ship as research object,firstly creating the 3D model of every part with Pro/E software,and assembling parts to obtain assemblies with crank pins at top dead center,bottom dead center,fuel pump side and exhaust side respectively.Then importing assemblies into ANSYS Workbench.After setting material,dividing grid,setting connections,adding load and boundary conditions and so on,outputting main engine crankshaft deflection measurement points' displacement along axis direction,main engine bearing load and middle bearing load.This paper adopts finite element method to study the influence of main engine base height adjustment on each crank deflection difference and bearing load by adjusting the height of main engine base aft side and left side.It is found that the heights of main engine base aft and left side are proportional to each crank deflection difference in vertical plane and horizontal plane.However,the proportional coefficients are different.By using the proportional coefficients,each crank deflection difference in vertical plane and horizontal plane after main engine base height adjustment can be calculated.As the crankshaft deflection difference is adjusted by main engine base height,and the heights of main engine base aft and left side are proportional to each bearing load,the variation value of each bearing load after crankshaft deflection difference adjustment can be calculated.This paper designs the forecasting software of crankshaft deflection difference under main engine base height adjustment by VB.NET and EXCEL software,according to the influence law of main engine base height adjustment on each crank deflection difference.As long as inputting the height adjustment value of main engine base aft and left side,the adjusted crankshaft deflection difference in the vertical plane and horizontal plane can be calculated.By adjusting main engine base height several times,the suitable adjustment scheme can be obtained,which makes each crankshaft deflection difference within reasonable range.