汽车前风窗玻璃的除霜性能数值研究

NUMERICAL STUDY OF AUTOMOBILE FRONT-WINDSHIELD DEFROSTING

基于RNGk-ε湍流模型,对汽车前风窗玻璃的除霜性能进行研究。建立B柱前乘员舱模型和完整乘员舱模型,研究计算域对除霜仿真结果的影响。为保证分析结果的准确性,模型中将驾乘人员及座椅包含在内,且在仿真过程中考虑人体热源的影响。数值分析结果表明,完整乘员舱模型的计算收敛时间比B柱前乘员舱模型增加44%,而两种模型的出风口风量分配和前风窗稳态风速相差很小。两种模型的前风窗平均温度、霜层液态分数差距比较明显,完整乘员舱模型的瞬时除霜结果与实验值能较好吻合,且能准确反映驾驶员呼吸点的温度。因此,当以除霜风道的风量分配为分析目标时可采用B柱前乘员舱模型,但在研究瞬时除霜效果、评价除霜工况下的车内热环境时,必须采用完整乘员舱模型进行分析。

RNGk-ε turbulence model was chosen to analyze the defrosting of automobile front-windshield. To research the influences of computational domain on simulation results, the front B-pillar part of cabin and full-scale crew cabin models were established respectively. The both models contained the driver, passenger and seats to ensure accuracy. During the simulation, the driver and passenger were considered as heat sources. The results show that, simulation convergence time of full-scale crew cabin increases 44% than the front B-pillar cabin＇ s, but two models＇ differences in air flow distribution and steady wind speed are very small. Besides, there are obvious differences in average temperature of windshield and liquid fraction of frost layer. In transient simulation of defrosting, the full-scale crew cabin is better compared with the experiment. In addition, the simulation results of full-scale crew cabin can reflect the temperature of driver＇s breath point accurately. Therefore, the forward B-pillar of crew cabin can be used to study the air flow distribution of defrost duct. But when studying defrosting transient effect or evaluating automobile＇ s thermal environment, it is necessary to establish full-scale crew cabin model to get accurate results.