增压器压气机密封性能模拟与试验研究

Numerical Simulation and Experiment for Turbocharger Compressor Sealing

采用Numeca数值分析软件建立了某汽油机增压器压气机端流场网格模型,并计算出增压器在低速近堵塞工况下进口压力为负压时压气机性能曲线,对压气机流场分析发现,轮背压力沿径向方向逐渐降低,在轴中心位置附近达到最小值,而在周向方向则变化较小。此外,在不同的转速下,随着进气口负压程度的加大,在轮背建立起来的压力逐渐降低,当进气负压增加到某一值时,若轮背临近密封环处的压力在大气压力附近波动,压气机发生漏油的风险提高。为了验证压气机负压能力预测的准确性,在现有压气机性能测试试验台架上开展了压气机密封性能测试,结果发现,在50 000r/min时,增压器压气机在-6kPa开始发生漏油,50 000r/min转速下则在-12kPa发生漏油,模拟分析结果与试验结果存在一些差异,而后就可能存在的原因进行了分析,以完善分析方法,提高增压器产品性能预测能力。

The compressor flow field grid model of a gasoline turbocharger was established with Numeca software and the compressor performance curve of negative inlet pressure was calculated under the low speed near choking condition. The com- pressor flow field showed that the pressure inside the back cavity decreased gradually along the radial direction, reached the min- imum in the vicinity of impeller shaft, but had little change in the circumferential direction. Under different rotation speeds, the built pressure in back cavity became lower with the increase of negative inlet pressure. When the negative pressure decreased to a certain value, the air pressure near the sealing ring fluctuated around the atmospheric pressure and the risk of compressor oil leakage increased. In order to verify the prediction accuracy of compressor negative pressure ability, the sealing performance testing was carried out on the existing compressor performance test bench. The results show that the lube oil of turbocharger compressor begins to leak under -6 kPa at 50 000 r/min. At 80 000 r/min,the lube oil begins to leak under -12 kPa. For the difference between test results and simulation results, the possible reasons were analyzed to improve the analysis method and enhance the performance prediction ability for new design turbocharger products.