Turbofan Engine Performance Deterioration Due To Fan Erosion

摘要

In this paper, the performance deterioration for the fan due to geometry changes by erosion is investigated and discussed. Furthermore, the fan life time is predicted. The fan in concern is installed in General Electric CF6-50 high bypass turbofan engine. It is large in diameter and has highly twisted blades. Moreover, the overall engine performance degradation due to fan performance deterioration is predicted. The studied aircraft mission lasts on the average for 3.5 hours. 7.5% of the mission time is near the ground and the remaining 92.5% is for the cruising condition. The life time of the fan is divided into 2000 cycles intervals. After each interval the fan geometry is updated and the flow field is solved to predict the fan performance. The fan performance is predicted after 2000, 4000, 6000, and 8000 cycles. Finally the fan performance characteristics are used to determine the performance deterioration in the CF6 turbofan engine. It is found that, fan erosion causes a remarkable degradation on both the fan and the engine performances. After 8000 operating cycles it was found that, the surge margin is reduced from 10.5% and 9.77% to 2.5% and 1.5% at cruise and takeoff, respectively. Furthermore, there is a decrease of 2.35% and 3.55% in the fan pressure ratio and fan efficiency for both cruise and takeoff, respectively. The fan life time based on the blend limits provided by the engine manufacturer is found to be after nearly 5000 operating cycles.