大型拖拉机驾驶室热舒适性评价

Cab Thermal Comfort Assessment of High-power Tractor

针对国内大型拖拉机驾驶室热舒适性差的问题,在对热舒适性影响因素分析的基础上,选取进风风速、风温和出风角为研究因素,采用ANSYS 18. 1-Fluent软件进行正交仿真,并基于仿真结果进行了人体热舒适性评价。仿真结果表明,整个驾驶室降温过程平稳有效,驾驶室内温度可调节范围为18~22℃,驾驶员周围风速为0. 2 m/s,耗时21 min后驾驶室温度达到人体最适温度且人体各热舒适性指标均处于人体热舒适性区间内。正交仿真结果表明,空调风速和风温对降温效果影响显著,出风角对降温效果影响不显著。人体局部温度的仿真结果表明,在第41秒时人体脸部温度开始下降,头部首先进入舒适区,10 min时人体各部分进入舒适区并在第21分钟人体各主要部分达到最舒适点,满足人体对降温速度的要求。若持续降温,在50 min后驾驶室平均温度进入人体不舒适过冷区。人体热舒适性评价曲线表明,平均投票数评价曲线成直线下降趋势,说明所设计驾驶室的温度场能以较快速度达到人体舒适区;不满意百分数评价曲线呈现先下降后升高的趋势,表明整个降温过程人体首先从过热区进入舒适区,若继续降温则又会进入寒冷区,再次对人体产生不舒适。综上,仿真结果符合驾驶室内的实际降温情况和人体生理反应过程,为温度智能控制系统和驾驶室空气净化系统的设计提供了一定参考依据。

With the dramatically growing use of agricultural high-power tractors,comfort of cab is an important problem in China. Because of the indirect impact with low comfort of the cab,the productivity is restricted. Health of tractor drivers was also undermined by low comfort of the cab. According to the least energy principle,the factors of comfort cab were defined. One of them was the thermal comfort. The simulation and dynamic assessment of comfort tractor cab were studied. The results showed that during the whole period of cooling process,the wind speed was 0. 2 m/s which was accorded with the comfort demands and the minimum of temperature in the cab was 18℃. Firstly,the governing equations that contained CFD and thermal comfort assessment equations were deduced. The equation temperature and the monitor temperature were less different so that comfort zone theory could be used in cab thermal comfort design. In order to get the best value of parameters,the orthogonal simulation test was used. The speed and temperature of wind were significant to the cooling effects and the angel was not significant to the cooling effects according to the simulation results. The temperature of head zone began to decline at41 s initially and went into the comfort zone firstly. At 10 min during the cooling period,each limb of tractor driver felt comfort and the most comfortable was at 21 min. This cooling result could be set default value in intelligent control system. After 50 min,the temperature of tractor cab would be into the uncomfortable cold zone if cooling was continued. Then the dynamic comfort process was calculated by predicted mean vote and predicted percentage dissatisfied. Because the predicted mean vote was declinedrapidly,the feeling of drivers became better rapidly. Predicted percentage dissatisfied declined firstly and ascended after 50 min. It was showed that the comfort feeling was in a time segment if cooling was continued. The assessment results also confirmed the correctness of the simulation results. The simulation results also provided certain reference basis for intelligent temperature control and air cleaning design of high-power tractor cab.