Simulation of casing vibration resulting from blade–casing rubbing and its verifications

In order to diagnose effectively the blade–casing rubbing fault, it is very much necessary to simulate the casing vibration correctively and study the casing signals׳ characteristics under blade–casing rubbing. In this paper, the casing vibrations in aero-engine resulting from the blade–casing rubbing are simulated. Firstly, an improved aero-engine blade–casing rubbing model is introduced, in which, the effects of the number of blades and changes in the rotor–stator clearance on rubbing forces are considered, the improved rubbing model can simulate rubbing faults for various rubbing conditions, including single-point, multi-point, local-part, and complete-cycle rubbing on the casing and rotor. Secondly, the rubbing model was applied to the rotor–support–casing coupling model, and the casing acceleration responses under rubbing faults are obtained using the time integration approach, which combines the Newmark-β method and an improved Newmark-β method that is a new explicit integral method named the Zhai method. Thirdly, an aero-engine rotor tester with the casings was used to carry out rubbing experiments for single-point rubbing on the casing and complete-cycle rubbing on the rotor, the simulation result was found to agree well with the experimental values, and the improved blade–casing rubbing model was fully verified. Finally, other rubbing faults were simulated for various rubbing conditions and their rubbing characteristics were analyzed.