Analysis On The Thermal Load Of Key Components Of The Combustion Chamber Of A Low-speed Two-stroke Marine Engine

The improvement of power performance of large 2-stroke marine engines results in increasingly high thermal load of combustion components, which is a great challenge on the engine reliability. In order to ensure reliability, the structure optimization based on thermal load analysis is necessary. The accurate temperature field analysis on combustion chamber components is prerequisite for precise thermal load. This thesis introduces the CFD-FEA coupled analysis of temperature field of cylinder head and liner.Firstly, the cooling water system of a low-speed two-stroke marine engine was simulated by using a 3D CFD software. The cooling performance was evaluated through the pressure losses, flow velocity distribution and heat transfer coefficient distribution of cooling water. Meanwhile, the working process of the engine was simulated to analyze the temperature field in the combustion chamber and the heat transfer coefficient distribution in the gas side of the combustion chamber. The CFD simulation also provided the thermal boundary conditions of main surface in the gas side and cooling water side.Secondly, the geometric models of combustion chamber components were created and the three-dimensional finite element model of the assembly was established. Based on the fluid-solid coupling method, the thermal boundary conditions of the main surface provided by the CFD simulation were mapped to the surface unit of the elements in the Finite Element Analysis (FEA) model of the assembly. Then the temperature field of the coupled combustion chamber components was analyzed. The simulation results include the steady temperature field and heat flux distribution under the rated operating condition. The results show that the temperature field is inhomogeneous along the circumferential direction and two high-temperature zones concentrate on the wall surface of the cylinder cover. The thin-walled structure or cooling boreholes will increase the local heat flux, which improves cooling performance and reduces thermal load.Finally, based on the temperature field of combustion chamber components, with the consideration of the mechanical load, the thermo-mechanical coupled stress field was analyzed. The simulation results include the stress field and deformation distribution at the moment of peak pressure. The results show that the stress field is closely related to the thermal load and the combustion chamber has a uniform deformation.Through the above work, the temperature field and stress filed of the key components of combustion chamber were acquired; the potential causes of the possible failure of combustion chamber components were analyzed. The work provides database for the structure optimization of the combustion chamber components.