Research On Numerical Simulation Analysis Of Vehicle Underhood Thermal Management

The vehicle underhood thermal management directly influenced the performance of engine and components in underhood, and then influenced the power, safety, reliability, emission and fuel economy of the vehicle. The numerical simulation technique has been widely used in the process of vehicle development depends on its advantages of short cycle, low cost and can be researched in advance. This paper takes the upgrading of a certain microbus which has a good sale as the research background, using the numerical simulation analysis to the research on the vehicle underhood cooling air intake and its thermal protection.The vehicle underhood cooling air intake especially the radiator air intake has direct concern on the cooling performance of the radiator. Based on the vehicle CAD model and the cooling system test data supplied by the automobile enterprise, the 3D numerical simulation analysis model of underhood cooling air intake was established, and the 1D and the joint 1D/3D simulation model of cooling system were also built. In 3D analysis model, respectively using porous media model and Dual cell model to simulate the flow resistance and heat transfer characteristics of radiator, and the fan model is applied to simulate the cooling fan. Based on the radiator intake air mass flow got by 3D analysis, analyzed the cooling system respectively by 1D simulation and the joint of 1D/3D simulation,Validated the feasibility of the Dual cell model in analysis the radiator cooling liquid temperature by the comparison of the results get by the three analysis method. Judged the radiator air inflow whether meets the requirement according to the coolant temperature, thereby estimate the performance of the front-end intake grille, deflector and sealing strip. The purpose of underhood thermal protection is to ensure the components like the rubber and plastics which have high requirement for temperature are not overheated. Convection and radiation are main two ways of heat exchange in underhood, and exist mutual coupling between them. The traditional CFD analysis can accurately simulate the convection, but when considered the radiation will lead to difficulty in convergence, long period in calculation especially the transient calculation. For the mentioned problems, the paper has built a coupled transient analysis process by combined the existed CFD software and the thermal analysis software Rad Therm, and do the transient analysis of underhood thermal protection in accelerated climbing process. The results compared between simulation and test show the feasibility of the coupled transient analysis process in analyzing the underhood thermal protection, so as to provide the guidance for underhood thermal protection design.