Bearing-rotor Dynamic Research On MS6001B Gas Turbine-Generator Set

Presently, we are short of systemic statistics about bearing-rotor dynamicresearch on MS6001B gas turbine-generator set, as is one of the crucialfactors for the unit to operate safely, so it is essential to carry out scientificresearch in this field. Bearing-rotor dynamic research on6B gasturbine-generator set has been carried out systematically in ANSYS, such asmodeling for dynamic research, critical speed, unbalance response andstability analysis, torsional analysis, as well as the influence of temperaturefield on the critical speeds of gas turbine rotor.Dynamic modeling for bearing-rotor system are as follows:(1) Modaltest has been taken on the gas turbine rotor in the free-free supportingcondition, and then we established two models of the rotor in ANSYS: thetie-bolt rotor considered as a whole in the first one, while contact stiffnessconsidered in the second one. By comparing the results of the first threenatural frequencies calculated in FEM with the values measured in modal test,it is reasonable to study dynamic characteristics based on the contact-stiffnessmodel.(2) Lack of relevant information,4stiffness factors and4dampingfactors of journal-bearings are provided by linear interpolation fromexperimental data.(3) Because of gear driving, vibration between gas turbinerotor and generator rotor are coupling, so4stiffness factors are brought in tosimulate the coupling induction according to API rotordynamic standard, andresults of modal analysis told us that coupling stiffness had a great influenceon dynamic characteristics of the gearbox.Achievements in dynamic calculation are as follows:(1) Referring to the theoryof heat transfer, steady-state temperature field of gas turbine rotor is calculated inFEM. Taking steady-state temperature field into account, the results of the first threecritical speeds calculated coincide with the values measured well.(2) Unbalanceresponse is studied with the method of harmonic in two extreme distributions ofunbalance: the phase is the same or opposite, and the amount of unbalance is residual after balancing. Complex modal analysis on critical speed and stability are carried outin the QRDAMP eigensolver, taking coriolis into account. The results of the firstthree critical speeds and the response to unbalance calculated inosculate with thevibration data measured in field balancing, moreover, logarithmic decrementrepresenting stability, amplitude of unbalance response and natural frequency oftorsional vibration meet the requirements of API rotordynamic standard. So themethod and the results in bearing-rotor dynamic research are accurate.(3) Torsionalstiffness of generator rotor are worked out according to empirical formula, and thentorsional analysis is carried out through a three-dimensional model.