Failure Analysis of Rubbing of the Fan Tip and Case of an Engine

Abstract

Unexpected hard rubbing of the fan tip and case occurred during the reduced-scale high-bypass fan performance test which took place at a bypass compressor Test-Facility of an institute. A great deal of effort had been expended with regard to this event. Firstly, failure investigation was done by means of Fault Tree Analysis which was based on the on-site test failure records, test pieces dis-assembly check and Test-Facility check. Results indicate that the fault waspossibly caused by the combination effect of over-rated motor starting acceleration and insufficient value of the fan blade tip clearance and axial length of the case coatingin design. Then, failure reproduction,confirmation of reasons and mechanism analysis were done by simulating the spinner cone bolt deformation and simulating the rubbing of fan blades and case, in combination with the analysis of the characteristics of fan blade and the no-load test of motor starting.Finally, in order to solve the problem, several improvements were established, including modifying the motor speed limit parameters to reduce the starting acceleration, increasing the fan blade tip clearance and increasing the axial length of the case coating. These solutions were verified by test.