Modeling And Fault Simulation Analysis Of Dual-rotor System With Marine Gas Turbine

Dual-rotor system is the very important component of marine gas turbine. Studying its faults, analyzing the characteristic of its common faults can provide some bases for dual-rotor fault diagnosis. This paper mainly established the model of dual-rotor system and its fault, and studied the rub-impact fault, unbalance and the initial bending fault simulation calculation.This paper used the finite element method to establish dual-rotor motion model, introduced the fault characteristics of dual-rotor system’s common faults and established mechanics models of faults. On this basis, the simulation calculation program of dual-rotor system was written.Secondly, we did the simulation calculation analysis for two kinds of dual-rotor systems: with interrotor bearing and without interrotor bearing but casing under two forms of rub-impact faults: circular partial rub-impact and fixed-point rub-impact. The results show that: under circular partial rub-impact, the shaft center plot is generally mixed and disorderly circle, under fixed-point rub-impact, the shaft center plot is generally distorted oval; some different spectrum characteristics can be seen from the comparison and analysis of two dual-rotor models and two rub-impact faults, but the overall dual-rotor vibration frequency spectrum characteristic can be summarized as the emergence of high harmonic frequencies and combined frequencies. These can be used as dual-rotor system with rub-impact fault characteristics; by changing the key parameters of rub-impact, it can be seen that as the rub-impact fault is more serious, the shaft center plot gets more cluttered and distorted, frequency amplitude decreases, high harmonic frequency and combined frequency amplitudes increase.Finally, we compared and analyzed the unbalance fault the initial bending fault. From the amplitude-frequency response, when only the initial bending fault or with unbalance fault, the "concave valley" phenomenon appears, but the relative position could be different, and when only unbalance fault, this phenomenon doesn’t appears; From the phase-frequency response, when only unbalance fault, phase angle deflects in the four critical speeds, and when the system has initial bending fault (acts separately, and acts with unbalance fault), in the "concave valley", phase angle deflection also appears, but the direction of the deflection is different.