Numerical Analysis of Cooling Effects of a Cylinder Head Water Jacket

The aim of this study is to discover the characteristics of the cooling water in the cylinder head of a high-power diesel engine by using the Computational Fluid Dynamics (CFD). A 3-D geometric model of a cylinder head water jacket was previously constructed using Unigraphics software. A mesh was then imposed on the model using the preprocessor of Fluent software, GAMBIT. Three types of thermal boundaries are defined and the standard ε − k model is utilized to carry out numerical simulations with the CFD software Fluent. The pressure distribution, velocity field distribution, heat transfer coefficient distribution, and temperature distribution of the cylinder head water jacket are presented and analyzed. In addition, the impact flow rates have on the cooling system of a cylinder head is studied. The relevant figures show that enhancement in flow rate will increase the velocity and heat transfer coefficient of the coolant flow but in the meanwhile bring in higher pressure loss. The design of the cylinder head water jacket is evaluated to be satisfactory in terms of cooling effects. Simulation results are compared with the work done by others and limited experimental data, and it is pointed out that the disparity of heat transfer coefficients is mainly due to over simplification of the model and inappropriate use of the turbulence model or wall function heat transfer coefficient. Some suggestions on the types of boundary conditions and appropriate turbulence models are proposed, which include the definition of boundary conditions on different locations and the use of coupled simulation.