Influence of contact stresses in impellers joints on the marine gas turbine rotor stress-strain state

Abstract The problem of the modern gas turbine impellers contact problem has been studied. When designing the gas turbine rotors, the contact between the impeller parts is consisted absolutely hard with the hard clamping boundary conditions in the contact zones. It is caused by the influence of contact pressure, formed during the process of impeller mounting. But due to the influence of the gas flow, that causes forced vibration of the blades and intensive heat exchange between the blades and disk, the contact pressure decreases and as the result decreases the whole impeller stiffness. The structural damping is also present in the contact zones. Thus to find out the influence of these factors on the contact pressure value the refined mathematical model, based on the usage of specially developed contact finite elements was developed. All calculations have been done in the ANSYS finite elements program using the Lagrange variational principle and Kholetski numerical algorithm. The influence of contact pressure on the value of contact heat transfer in the impeller contact zone has also been studied. It was determined that the contact heat transfer of the joint increases with increasing of contact pressure both in the contact zone of the blades with the disk and in the contact zone of the of the adjacent blades bandages. Taking into account the presence of structural damping in the blades bandages and the insignificant roughness of the contacting surfaces in accordance with the technological documentation of the blades mechanical processing, the dependence of the contact pressure on the frequency of the most loaded first impeller forced vibration was determined. The influence of the bandages geometric parameters on the value of the contact pressure was established. The obtained results should be used for solving the problems of the gas turbine rotor fatigue strength and durability.