Oscillating Heat Transfer Characteristics And Field Synergy Analysis Of Highly-intensified Piston

Piston is one of the most important parts in diesel engine,which directly affects the reliability,durability and economy of diesel engine.In recent years,with the continuous improvement of diesel engine power,the thermal load of the piston in direct contact with the gas has increased rapidly.So it must be effectively cooled.There are many ways to cool a piston.And the most common one is to use an oscillating cooling method with the cooling galleries.At present,great progress has been made in the research on the influencing factors and laws of piston oscillating cooling.But its enhanced heat transfer mechanism is not yet clear.This project will use the field synergy principle to study the oscillating heat transfer characteristics of pistons for the first time.The heat transfer characteristics of cooling galleries with different shapes and working conditions are analyzed.And the field synergy analysis is carried out.The effects of rotational speed,amount of cooling oil and stroke on oscillating heat transfer are analyzedFirst,the Fluent software is used to numerically simulate the oscillating flow and heat transfer process of the closed elliptical and drop-shaped cooling galleries.And the field synergy principle is used to analyze the heat transfer characteristics under different crankshaft angles,different rotational speeds,and different strokes.The results show that the heat transfer effect of the drop-shaped cooling galleries is better than that of the elliptical cooling galleries.The speed field and the temperature gradient field in the drop-shaped cooling galleries have relatively good synergy.With the increase of rotational speed and stroke,the average heat transfer coefficient of the cooling galleries wall is continuously improved.The field synergy performance near the wall of the cooling oil cavity is also improved.and the stroke is obtained.Secondly,numerical simulation of the oscillating flow and heat transfer process in the open water droplet cooling galleries is carried out.The influence of the rotational speed,the amount of cooling oil and the stroke on the oscillating heat transfer effect is analyzed.And the variation law of the wall heat transfer coefficient increases with the increase of the speed,the amount of cooling oil and the stroke is obtained.Finally,the field synergy analysis of the cooling galleries chamber is carried out.The results show that the synergy of velocity field and temperature gradient field near the upper wall is the best in the open cooling galleries.At the same time,the change law of synergy degree of velocity field,temperature gradient field and heat flow field under different rotational speed,cooling oil quantity and stroke is obtained.It is believed that the heat transfer effect and field synergy of the slender drop-shaped oil cavity are better.