Study Of Underhood Thermal Management Of A New Vehicle

Now, the competition of car market in the world is becoming fiercer and fiercer. The new vehicle is produced by all famous automobile companies. And these companies do their best to reduce the development cost and shorten the development cycle. The computer simulation technique can make the development cost reduce. This technology has played an important role in the development process.On the background of a certain new passenger vehicle of a famous automobile company, three-dimensional geometry model was built and modified. According to the requirement of precision, high quality grid was gained based on grid generation software Hypermesh and Tgrid. The thermal performance of underhood was analyzed at the idling and cruising (90Km/h) conditions. Three-dimensional velocity field and temperature distribution in the underhood were given. The main reason leading to high temperature and spontaneous combustion in underhood was found out. According to the computational results, four optimization proposals were brought out. After the preliminary analysis on economy and validity, the proposal of adding choke plate was adopted. The new geometry model was built, and its thermal performance was analyzed at the idling and cruising (90Km/h) conditions. Then, the dynamic thermal equilibrium performance of the cooling system in the underhood was investigated using the Flowmaster software.The above computational results show that: (1) The reason of high temperature in the underhood of the original car is the unreasonable arrangement of components in the engine compartment, so that the heated cooling air at the back of the engine cabin returns to the front of the heat exchanger, and reenter the cooling cycle by the suction of the fan; (2) By adding choke plates circumfluence of heated air can be alleviated effectively, then the cold surrounding air can enter the engine cabin smoothly from the air-inlet grille. The thermal performance of underhood can be significantly improved; (3) By one-dimensional dynamic thermal equilibrium analysis, it can be found out that the temperature values of all components of underhood cooling system at the critical positions are within reasonable ranges. This demonstrates that optimization proposal can improve the thermal performance of underhood, but not reduce the performance of all components in the underhood.Using one-dimensional dynamic simulation and three-dimensional steady simulation, the level of underhood thermal management can be significantly improved.The research in this thesis was funded by a famous automobile company in Shanghai.