流体可压性对轮式装载机中冷器的影响

Influence of fluid compressibility on charge air cooler of wheel loader

为提高换热器换热量的计算精度,以某型号轮式装载机水冷中冷器为研究对象,通过截面变化率、换热量、表面摩擦因数等变量建立其增压空气侧可压缩流模型.采用计算流体力学(CFD)软件对模型进行了仿真验证,结果表明可压缩流模型与不可压模型的偏差随流量增加而增大.与试验结果对比发现:在流量较低时,宜使用不可压缩模型简化计算;当流量较大时,则宜使用可压缩模型提高计算精度.试验条件下,可压缩模型的换热量与试验值最大偏差为6.5%,压力损失最大偏差为7.5%.所提方法改善了高流速区间由于忽略可压缩性带来的偏差过大的问题,为换热器的优化设计提供了指导.

To improve the calculation accuracy for the heat exchanger,this paper establishes a compressible flow model for the pressurized air side of the exchanger. Considering the heat exchanger in wheel type loader,the present model employs the change rate of cross-section,heat transfer amount and surface friction coefficient as variables. CFD（computational fluid dynamics） is used to validate the model and simulation results have shown that the deviation between the present compressible flow model and the traditional incompressible model increases with the increasing flow rate. Compared with experimental tests, the incompressible model predictions are only acceptable when the flow rate is low; whereas the present compressible model provides more accurate predictions for high flow rate zone. Results reveal that the maximum deviations between the present model and test on pressure and temperature are merely 6. 5% and 7. 5%, respectively. Therefore, the present model solves the problem of simulating the high flow rate zone due to the neglect of the compressibility. This model would further guide the optimal design of heat exchanger.