The Performance Research Of Flow And Heat Transfer On Engine Cooling System

Cooling system is an important part of the diesel engine,it is critical to the normal operation of the engine.The flow and heat transfer of the cooling liquid have crucial impact on the cooling efficiency,the heat load of the cylinder block and cylinder head parts,emissions,cooling uniformity of each cylinder etc.And it is related to the power performance,fuel economy,reliability and durability of diesel.With the increase of specific power in development of modern engines,it is certain to generate a higher temperature in cylinder,so improve the cooling efficiency of cooling system is becoming more and more important.cooling jacket structure optimization is an important way to improve the efficiency of the cooling system.At present,more and more researchers using the method of fluid-solid coupled simulation to study the engine cooling system.This paper takes a fluid-solid coupling numerical simulation research about flow and heat transfer on a 8-cylinder diesel engine cooling water jacket by using CFD software STAR-CCM+.A whole model include cylinder body,cylinder head and cooling water jacket is built by UG software.The numerical calculation on pure water flow and heat transfer in original diesel engineer cooling system is conducted with CFD analysis software.make a detail analysis about the velocity,pressure gradient,heat transfer coefficient of water jacket wall surface and temperature distribution of high temperature parts to judge the cooling performance.Two structure optimization methods are proposed to improve the flow and uniformity among each cylinders,included the distribution adjustment for inlet holes connect cylinders and size optimization about the hole connecting the cylinder head.Considering that the surface temperature of some high temperature parts exceeds the saturation temperature of cooling liquid,so a two phase flow boiling model is built during the calculation,compare the result with no boiling model,analyze the effects of boiling factors on flow and heat transfer of the cooling system,and come to a conclusion that in the numerical simulation analysis of heat transfer for high strengthen diesel engine to determine whether consideration the boiling effects is necessary.Research work about improving the flow and heat transfer for diesel engine cooling system will provide reference for practical problems related to engineering,so it has certain practical value.