Numerical Investigations Of Two Phase Flow And Conjugate Heat Transfer In Oscillation Cooling Piston For A Marine Diesel Engine

Thermal load of heavy duty marine diesel engine pistons has increased intensely due to the trend of high power density and high efficiency in recent years,most engines use oil gallery cooling system with cocktail shaking to deal with increasing heat loads from piston.Therefore,this paper mainly studies the oscillation cooling.If the design of the piston oil cavity is reasonable,it is necessary to discuss and study the oil cavity in many aspects.In this paper,the piston cooling oil chamber of a diesel engine is studied.Firstly,the heat transfer characteristics of the piston oil cavity and its circumferential heat transfer characteristics are studied by using Fluent.Then some parameters affecting the heat transfer coefficient of the oil cavity,such as speed,injection speed,turbulence model and angle of tilt,are studied.Finally,the fluid solid coupling heat transfer analysis is carried out on the piston and the oil cavity,and the stress analysis of the piston is carried out respectively.The main contents are as follows:(1)The flow pattern of oil is simulated by the method of dynamic grid and momentum source,and the correctness of the method of applying the momentum source is verified.The heat transfer characteristics of the four regions of the piston oil cavity wall and its circumferential 18 regions are studied by applying the momentum source method.The change trend and characteristics of the heat transfer characteristics of the oil cavity along the circumferential direction are obtained.The heat change in one cycle of the oscillating cooling oil chamber is studied,and the ratio of the oil to the inlet and outlet of the oil is obtained.(2)Based on the method of loading momentum source,the influence of different turbulence models,speed,injection speed and piston inclination angle on the heat transfer coefficient and the influence of heat transfer coefficient on the four regions of the piston wall are analyzed.The change law of oil filling rate and heat transfer coefficient of oil cavity are also discussed.(3)The distribution of the piston temperature field at the key position of the crankshaft and the steady temperature distribution of the piston are obtained.The monitoring points temperature value at the key position of the crankshaft is compared with the test value.(4)The transient maximum temperature of the piston is applied to the piston,and the mechanical load at the TBC is applied.The stress field of the piston is analyzed.Finally,the deformations of three directions are analyzed.