Abstract: Under actual working conditions,the shaft system of micro gas turbines is often affected by coupling loads due to various factors.The closed interference connected diaphragm coupling is a key flexible component for connecting double span rotors on gas turbines,and its coupling stiffness has become an important parameter affecting the static and dynamic performance of the system. Currently,there are many studies on the single load stiffness of diaphragm couplings,and the coupling stiffness characteristics are unclear,which is not conducive to the improvement of their design technology and shaft system stability.Based on this problem,by simplifying the solution model of the diaphragm coupling,the overall torsional stiffness characteristics of the coupling under the combined action of axial and torsional loads were studied through simulation analysis,and comparing the torsional stiffness characteristics under single torsional load.The results showed that under the action of axial torsional coupling,the overall torsional stiffness of the diaphragm coupling exhibits nonlinear characteristics. When the ratio of torsional load to axial load is less than 0.25,the axial torsional coupling effect is obvious,and the torsional stiffness of the diaphragm coupling decreases. When the ratio of torsional load to axial load is greater than or egual to 0.25,the coupling effect can be ignored and can be considered as a pure torsional state. The characteristic lays the foundation for further in-depth research on the influence of diaphragm coupling on the dynamic performance of the shaft system and its optimization design.

Key words: torsional stiffness, coupling of axial and torsional load, gas turbine, coupled stiffness