The Thermal Simulation And Optimization Research On The Car Underhood

At present, car tends gradually to be designed to streamlined and low body. Thisleads the engine compartment space smaller. At the same time, as the high temperatureheat source of the heat exchanger group, engine body and exhaust all in a compact space,the air flow is blocked and heat dissipation is difficult. The performance of Enginecompartment temperature sensitive components, such as ECU, battery, cable tree,rubber component, will be affected by high temperature and the original will bedamaged if local temperature is too high.In this case, it is necessary to design reasonably the arrangement of cabin organizethe flow field in the early design stage, which can guarantee cooling airflow fullyeliminate the heat engine and other high temperature heat source and avoid a vortex inthe engine compartment area and the local high to ensure that various parts of theengine compartment in the best temperature range. Based on automobile aerodynamicsand computational fluid dynamics, a research is carried on in this thesis to study the flowfield and temperature field of the under hood with a economy car model. The concreteresearch and content are as follows:1. The theory study of the car external flow field is conducted to determine thephysical model, fluid state parameters, turbulence model and calculation method of thesimulation.2. The geometry models of CFD simulation schemes are established. Thecalculation domain and grid layout are also set up.3. Using the coupling method of external and internal flow field of under-hood, thenumerical simulation is conducted on two limit conditions of climbing and high-speed.The characteristics of flow field and temperature field and the surface temperaturedistribution of the temperature sensitive element are analyzed.4. The structure arrangement reasons is find out which cause the temperaturedistribution unreasonable based on the simulation results. At the same time, the surfacetemperature distribution of the temperature sensitive element is contrasted under the twokinds of condition5. The radiator porous media model is verified, and the contrast analysis of theexperimental and simulation calculation values is conducted. Then the reliability of the model and the simulation results are analysis.6. Based on the analysis results of flow field characteristics of under-hood, theeffects on flow field and temperature field of under-hood are conducted with the intakegrille on the top closed or not. The mass flow changes of heat exchange group is alsostudied after improving the structure of front bumper and the cabin interior front beam.7. The fan speed impacts on the mass flow proportion of air-inlet grille, the massflow of heat exchange group, the radiator out side temperature and the best distancebetween heat exchange group and fan are researched.