Spline couplings which have simple structure, high reliability and can compensate torque transmission error are widely used in rotating machineries, such as aeroengine and gasturbine, etc. Recent efforts show that it is potential to make the rotor system losing its stability. Nevertheless, the experimental study of rotor system with spline coupling is rare and inadequate. This indicates a need to study the factors that affect the stability of rotor system with spline coupling experimentally. In this paper, a specially designed spline connection rotor test rig has been built and used to simulate a multi rotor system of turboshaft engine. The experimental instability characteristics of spline connected rotor system are presented. The instability speed and critical speed under different conditions such as lubrication conditions, external damping, load torque, spline tooth error and fit type of internal and external spline are measured. Based on the above-mentioned results, the effect rules of the influence factors on spline connected rotor system stability are studied. Results show that lubrication can effectively weaken the vibration of the system. The increased external damping makes the stability better when the spline coupling is unlubricated. With the increasing of load, the subharmonic vibration decreases after the system loses its stability, the system stability becomes better. The stability of spline coupled system with larger tooth error is better than that with normal one. Normal fit-up spline coupling improves the system stability under the conditions of lubrication and small external damping. This study may be helpful to get the favorable parameter setting of spline connected rotor system for avoiding instability and reducing vibration.

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