Rubbing dynamics between multiple blisks and abradable coatings: Experimental and simulation study

Abstract

Blisks-coatings rubbing are one of common faults in rotating machinery since the blade tip clearance is getting increasingly small for higher efficiency. As the rubbing-induced external load propagates from the rubbing blisk to the whole rotor, the rubbing margin elsewhere would get smaller to involve more blisks in rubbing. Yet the mechanism and development of single blisk rubbing to multiple blisks rubbings are not clear. In this paper, the finite element model and the experimental rig of a “0–2-1” supported multiple blisks rotor system are developed to study the multiple blisks rubbing dynamics. A novel rubbing force model is proposed, considering energy dissipation and plastic deformation based on contact theory, adapted to the characteristics of coating materials. Results show that a single blisk rubbing fault can develop to double, triple and multiple rubbing faults all around the rotor system. The frequency components can be used as characteristics that indicate the number of rubbing blisks or the location of rubbing but depend on the structure and rotating speed of rotor system. For the “0–2-1” rotor system in this paper, when double blisks rub the coatings at lower speeds, the 2 × frequency component becomes prominent if a compressor blisk is involved in rubbing. For multiple blisks-coatings rubbings, the 3 × harmonic helps in identifying the turbine blisk involvement, and fractional frequencies of 1/2 × and 1/3 × sometimes serve as important indicators. It is also found the rubbing force at the compressor blisk has obvious influence on the turbine rotor vibration, while the rubbing at the turbine blisk has minimal impact on the compressor blisk.