Lubrication Of Crankshaft Main Bearing Of Marine Low Speed Diesel Engine Characteristic Research

As the most critical part of diesel engine,crankshaft bearing failure will bring irreparable economic losses to diesel engine.The main reason of bearing failure is due to improper lubrication.Therefore,it is of great significance to study the lubrication characteristics of diesel engine,especially for marine low-speed diesel engine,because of its low-speed,heavy load and large size characteristics,lubricating oil film is very important Therefore,it is more urgent to study the lubrication characteristics of low-speed diesel engine.In this paper,the flexible multi-body dynamic model of a two-stroke low-speed marine diesel engine crankshaft is established.Combined with the theory of elastic fluid hydraulic lubrication,the multi-body dynamic model of low-speed diesel engine crankshaft system is established.After the model is verified,the lubrication characteristics and key lubrication parameters of low-speed engine crankshaft main bearing are studied under full working conditions,and the main bearing of low-speed diesel engine is obtained This paper presents practical suggestions and direction for improving the lubrication of marine two stroke low speed diesel engine.Firstly,the three-dimensional simplified model of the crankshaft and main bearing seat of the two-stroke marine low-speed diesel engine is established by using the three-dimensional modeling software.Considering the structural characteristics of the model and the requirements of continuity and accuracy of calculation,the hexahedral mesh of the model is divided.According to the Finite Element Substructure theory,the Finite Element Substructure of the model is reduced,and the crankshaft system is established by using the reduced results The node displacement of crankshaft system under rated working conditions and the stress results of connecting rod big end are calculated and analyzed.The results are compared with the traditional mechanical calculation results and experimental results to verify the multi-body dynamic model.Secondly,the whole model of the two-stroke marine low-speed diesel engine is established by using GT power software,and the cylinder pressure curves of the low-speed diesel engine under 25%,50% and 75% working conditions are calculated.As the main input condition,the lubrication characteristics of the diesel engine under all working conditions are analyzed.The calculation results show that the minimum oil film thickness decreases with the increase of load The results show that the peak pressure of oil film first increases and then decreases;the vertical force of main bearing increases with the increase of load,which makes the impact and vibration of crankshaft increase.Finally,the key parameters that affect the lubrication effect under rated conditions are compared and studied.The results are analyzed by changing the bearing relative clearance,lubricating oil supply pressure and oil hole center position.It is found that the relative clearance is too small,which is not conducive to the formation of lubricating oil film,and the friction power consumption is large.When the relative clearance is between 0.8 and 1,appropriately increasing the relative clearance can significantly improve the lubrication effect Increasing the minimum oil film thickness can reduce the friction power consumption.When the relative clearance is greater than 1,the excessive increase of relative clearance will reduce the minimum rear film thickness and increase the friction power consumption.Increasing the oil supply pressure can significantly improve the lubricating oil flow of the bearing and bearing bush clearance.It is better to arrange the oil holes in the range of 270deg-360 deg for lubrication.