| With the further improvement of social and economic level,automobile as a means of transportation and transport has become a necessity in people’s daily life.In the background of increasingly strict automobile emission regulations and people pay more and more attention to the comfort of the car,the lifting power of automobile engines is increasing,and the engine heat load is also increasing.Due to the small space of the engine compartment,the compact arrangement of the engine compartment,and the interaction of various components and systems,the airflow and heat transfer process in the engine compartment is very complicated and the heat dissipation is very difficult,which directly affects the fuel economy,power,emission,safety and comfort,and other important indicators.In this paper,a three-dimensional simulation platform for the whole vehicle and a one-dimensional matching calculation platform are built,and a series of researches are conducted around the rational organization of airflow in the engine compartment,improvement of heat return,and optimization of air inlet parameters at the front of the heat exchanger using simulation calculations,etc.The specific research contents and main conclusions are as follows.1.Using STAR-CCM+ to build a three-dimensional simulation calculation platform for the whole vehicle and carry out the calculation of engine compartment flow field;using KULI software to build a one-dimensional matching calculation platform to predict the heat balance capacity of the whole vehicle;using the whole vehicle heat balance test data to check the results of the three-dimensional calculation and one-dimensional calculation,verifying the accuracy and reliability of the threedimensional simulation calculation platform and one-dimensional matching calculation platform.2.Based on the typical working conditions of low speed and high torque,the 3D flow field calculation was carried out to analyze the airflow and heat exchange details in the engine compartment and optimize the design of the flow field.The study shows that: the design of the left,right and lower heat return baffle can effectively improve the heat return and reduce the heat exchanger air inlet temperature by more than 4℃;the optimized scheme of the frame beam can effectively reduce the airflow resistance in the engine compartment and improve the smoothness of airflow out of the engine compartment;the air inlet volume of the cooling module is significantly increased and the air inlet temperature is significantly reduced under each calculation condition by the comprehensive flow field optimization scheme.3.Based on the calculation of the 3D flow field of the engine compartment,the effects of fan installation distance,fan cover coverage ratio,and fan cover shape on four groups of air inlet parameters,such as air inlet volume,air inlet temperature,air inlet speed uniformity and temperature uniformity of cooling module,were studied.The improvement of air inlet temperature uniformity is greater;the coverage ratio of the fan cover relative to the fan is between 0.6 and 0.8 is a reasonable range,too large a coverage ratio is not conducive to the optimization of the heat exchanger air inlet parameters;the radial closing length of the fan cover outlet is greater than 5mm is conducive to improving the air inlet volume of the intercooler and radiator,reducing the air inlet temperature and improving the air inlet speed uniformity and temperature uniformity of the radiator.4.KULI is used to build a one-dimensional matching calculation platform for the whole vehicle thermal balance and evaluate the thermal balance capability of the vehicle under the comprehensive optimization scheme of the engine compartment flow field,and the results show that the comprehensive optimization scheme of the engine compartment meets the design requirements of the whole vehicle thermal balance capability.Also besides,based on the 1D matching calculation platform and its improved 1D platform describing the radiator partitioning model,the effects of air inlet volume,air inlet temperature,air inlet velocity uniformity,and temperature uniformity on radiator performance were investigated.The results show that increasing the inlet air volume and temperature uniformity,and decreasing the inlet air temperature can linearly improve the heat transfer performance of the radiator;increasing the inlet air speed uniformity leads to a sharp increase in radiator performance followed by a gentle increase;comparing the effects of four groups of inlet air parameters on radiator performance at the same level of variation,it can be seen that the inlet air volume and inlet air speed uniformity have a greater effect on radiator performance. |
