Integrated Effects Of Exposure To Disc Rod Rotor Axial Vibration And Dynamics Characteristics Of Torsional Vibration

As the capacity and speed of gas turbine generating units are improved, the working performance of rotor systems depends increasingly on its dynamic characteristics. Therefore, it is very necessary to make a study on the dynamic characteristics of disc-type rod fastening rotors for gas turbines. Being supported by the project of "Fundamental Research on Large Power Equipment Manufacture" listed in National Key Fundamental Research Development Programme (No. 973 Programme), we made the relevant study on dynamic characteristics of disc-type rod fastening rotors for large gas turbine and first established a dynamic model for axial vibration and torsional vibration for disc-type rod fastening rotor systems by utilizing bond graph method. We have also revealed the essential differences between rod fastening rotor and continuous rotor.With regard to the non-continuous feature of disc-type rod fastening rotor, in this paper, we firstly take full account of contact effect between disc and disc, and then make relevant mechanical assumptions for rod fastening rotors and first establish a bond graph model for axial vibration and torsional vibration of rod fastening rotors by utilizing bond graph method. And then, with regard to the contact effect between discs of disc-type rod fastening rotors, in this paper, we have described the geometric properties of rough disc surface on the basis of Hertz theory and GW model and utilizing random distribution model. The contact stiffness and equivalent torsional stiffness between rough surfaces have been analyzed and studied. And formulas to calculate contact stiffness and equivalent torsional stiffness have been given. The factors influencing contact stiffness and equivalent torsional stiffness have been analyzed. Analysis shows that contact stiffness and equivalent torsional stiffness are influenced by pre-tightening force and machining precision on the rough surface. They are increasing along with the increase of pre-tightening force and machining precision. At last, in order to verify the validity of the model, and compare the difference between rod fastening rotor and continuous rotor we have calculated and tested vibration characteristics of an experimental rod fastening rotor and drawn comparison between theoretical calculation result, test result and theoretical calculation result for a continuous integral rotor. The result shows that the model established by this paper is valid, and there is a big difference between disc-type rod fastening rotor and continuous rotor. The nature frequency of disc-type rod fastening rotor is lower than the continuous rotor, but the nature frequency of rod fastening rotor will increase along with the pre-tightening force increasing, and the rod fastening rotor will tend to continuous integral rotor. Moreover, we have found that, due to the non-continuous and combined feature, the nature frequency of disc-type rod fastening rotor is sensitive to the change of pre-tightening force. So, change the pre-tightening force is a positive way to adjust the nature frequency of rod fastening rotor. This will give a reference for the rod fastening rotor to avoid some fault frequency of gas turbine.