The Research On CFD Analysis And Heat Transfer Of A Gasoline Cylinder Head Considering Boiling Heat Transfer

Boiling heat transfer is an important heat transfer way in the water jacket of a water-cooled internal combustion engine cylinder head. By the research of boiling heat transfer factors of cylinder head cooling flow and the influence of heat transfer conditions, it can be more accurate prediction, evaluation and optimization of the structure of cooling water jacket in the internal combustion engine cylinder head.The main contents of this thesis include as follows:(1) Make use of the Eular multiphase flow model as the theoretical basis, combined with Rohsenow nucleate boiling heat transfer guideline, and established a new two-phase flow boiling heat transfer model, and verify the model through boiling heat transfer experiment in a cooling water channel.Compared the calculation accuracy of BDL boiling model and two-phase flow boiling model through the experiment, the results show that the proposed two-phase flow boiling heat transfer model has higher accuracy.(2) With a high speed marine gasoline engine as the research object, firstly, onduct an engine experiment on the water,to obtain the experimental data. To have CFD analysis of engine cooling system by the software of STAR-CCM+, then compared it with experimental data to determine the numerical simulation can correctly reflect the real flow of engine cooling water, to provide liquidity boundary conditions for the next boiling heat transfer simulation. Secondly, apply the software of GT-Power to simulate thermodynamic process, obtained thermal boundary conditions of the cylinder head fire-face and the surface of intake and exhaust port.(3) Applied with two-phase flow Rohsenow boiling heat transfer model and BDL boiling heat transfer model separately, have a heat transfer analysis to cylinder head. After the 3D model process of the cylinder head by the software of Hyper Mesh and STAR-CCM+,have a fluid-structure coupling calculation to the cylinder head,obtained the temperature distribution 、 heat transfer coefficient and the void franction of cylinder head,compared the calculation result of two different boiling heat model and experiment result,analyzed the influence of the flow of the cooling jacket and cylinder heat transfer under the case of boiling heat transfer.The results showed that the application of two-phase flow boiling heat transfer model than BDL boiling heat transfer model of temperature are generally lower in the most regions of cylinder head,two-phase flow boiling heat transfer model than the BDL boiling heat transfer model more enhanced heat transfer ability of the cooling water jacket,comparative analysis shows,the proposed two-phase flow boiling heat transfer model of this thesis is more suitable for the actual situation of flow and heat transfer within the cylinder head.(4) Use the method of FEA, make finite element analysis by the software of STAR-CCM+ and ABAQUS,to research the influence of thermal-mechanical coupling stress distribution of on the gasoline engine cylinder head after considered boiling heat transfer factors.The results showed that the application of two-phase flow boiling heat transfer model than BDL boiling heat transfer model of ther mal stress and coupling stress are generally lower in most regions of the cylinder head, all parameters satisfy the engine cylinder head material strength requirements.