Numerical Simulation Analysis Of Shaft Orbit For Hydraulic Generator Set

With the development of hydraulic generator set in the direction of large size, vibration issue becomes more and more important factor in influencing hydraulic generator set operation, even the power net operation. Vibration of hydraulic generator set often restrains its operation, which will affect it to give out maximum benefit in the system. The vibration of the shaft system of hydraulic generator set is induced by machine and electric and waterpower. The shaft stability of generating set and the power character play crucial role on the safe operation,it not only directly affects the safe operation,but also influences the life of set.Because the picture of shaft centre orbit contains abundant vibration fault information. We can use the picture of shaft orbit to carry out the operation state for large hydraulic generator set. From the picture of shaft orbit, judging the sign of early stage of vibration and preventing fault worsens of hydraulic generator set is feasible.The modeling strategy of the shaft system of large hydraulic generator set is discussed in this paper. A simple model of multi-degrees of freedom system is developed. Taking into account the gyroscopic effect, angular inertia, shear deformation, electric magnetic, oil-film force, the influences of the support of the bearing and inertia of the water in the runner etc., the various mechanical, electrical and hydraulic forces acting on rotor externally can be considered in the calculating model.Based on the actual structure of the shaft system of a 125MW Francis hydraulic generator set in Dajiang Plant of Gezhouba Power Station, a computer program for the calculation of the shaft orbit of the system is written on the basis of the Riccati transfer matrix method in conjunction with the Newmark-βintegration technique. The calculating results and discussion are given, which can provide the theoretical reference and support the research on the stability of large hydraulic generator set. The model presented in the paper will give a better understanding of the dynamic characteristics of the shaft system and a guidance in the design and fault diagnosis of the large hydraulic generator set. As an attempt, it is proved that the simulation model can be better applied in engineering.