Research On Equivalent Stiffness Of Shrunk-on Disc Rotor Of Large Turbine

With the rapid economic development, nuclear power plant has been to develop in our country in recent years because of the constraints of the energy and environment. However, with the increase of nuclear power unit capacity, the volume of the unit is also increasing, due to it has a relatively low steam temperature and pressure. To meet this requirement, especially the low-pressure rotor of the nuclear power plants are often designed to be very large, such as a low-pressure rotor of a 1000 MW nuclear power plant which the maximum radial diameter without considering blade is nearly three meters, and the weight reached 200 tons. There is no forging technology of such a large rotor in the world, the current solution is to employ shrunk-on disc rotor or welding rotor.In our country, the welding rotor design and manufacturing technology are more mature the shrunk-on disc rotor, especially in rotor dynamics analysis, the impact on bending stiffness and torsional stiffness of the shaft by impeller is no clear conclusion. This paper establishes the calculation method of the equivalent stiffness of shrunk-on disc rotor based on the finite element method. The stress and equivalent stiffness of the rotor in the design of interference have been acquired. The influence of impeller tightening force and equivalent stiffness was studied with different interference and speed. After establishing the dynamics model of shrunk-on disc rotor, the rotor static deflection, critical speed rigid, damped critical speed, each bearing journal vibration response amplitude of peak to peak under different balance, shafting stability and torsional frequencies of a nuclear power unit have been got. The results show:1)the effect of enhance of the shaft stiffness is different with the impeller and interference amount;2) The strengthening effect of the equivalent stiffness is more significant when the relative amount of interference from 0.5 ‰ to 2.5 ‰; 3) As the speed increases, the centrifugal tensile stress of hub applied by impeller is also correspondingly increase, weakening the stiffening by interference, and the speed is proportional to the square of the tensile stress;4) The effect of the bearing elevations by the interference is relatively large. The bearing #1 elevation have the biggest change. The biggest change in rates is LP1 which static deflection, rigid critical speed, logarithmic decay rate and Q-factor coefficient were 14.69%, 7.33%, 7.17% and 7.72%. The dynamic performance of bearing 2 have the biggest change.