Load Capacity of Interference Fit Between High-speed Coupling and Shaft Used in Micro Gas Turbine

Micro gas turbine is composed of compressor, turbine and generator which are coaxial connected by couplings and have the same rotational speed, so the high-speed coupling is important to the micro gas turbine. Interference fit, which is widely used in flexible coupling, have large torque capacity while avoiding the influence of unbalance. Thus, the aim of this paper is to analyze the load capacity of the interference fit for various structure and working conditions to ensure stable and reliable operation of the micro gas turbine. Firstly, based on the plane stress condition, the equilibrium differential equations are rewritten under the high-speed condition and the boundary conditions are rewritten under the torque transfer condition. Then the stresses and displacements area are given, including the radial stresses, hoop stresses and shear stresses. Secondly, the limit state of the interference fit is modeled with the stresses and displacements of the coupling and the shaft above. The maximum torques and angular velocities of the interference fit area are derived, and the influences of the working parameters on them are discussed, including the ratio of inside to outside diameter, friction coefficient, torque and rotational speed. Then the differences between the load capacities of the coupling and the shaft are compared under the same working condition. Finally, the numerical calculation results show: decreasing both the ratios of inside to outside diameter of the coupling and the shaft can increase the load capacity of the interference fit; The friction coefficient of the contact surface has a significant effect on the maximum torque of the interference fit while an insignificant effect on the limit angular velocity of that. The coupling’s maximum load capacity is lower than that of the shaft under the same condition.