Reliability Allocation of Adjusting Mechanism of Variable Geometry Turbine Based on Improved Agree Method

In the reliability allocation of the variable geometry turbine adjustment mechanism of an aero-engine, the importance and complexity of its subsystems obtained by the traditional AGREE method deviate from the actual importance and complexity of the subsystems, and affect the rationality of the reliability assignment results of each subsystem. To address this problem, the importance and complexity of the traditional AGREE method were revised, and an improved AGREE method was proposed. Firstly, the importance was modified by considering the degree of influence of different subsystem failures on the system, and the complexity was modified by considering the number of critical parts in the subsystem that will lead to mechanical failure, and the traditional AGREE method was improved. Then, the steps of reliability index allocation using the improved AGREE method were proposed. Finally, the allocation of the reliability index of the variable geometry turbine adjustment mechanism was completed using the improved AGREE method. The results of the study show that the improved AGREE method can be used to complete the reliability index allocation of the variable geometry turbine adjustment mechanism, and the allocation result achieves the allocation of lower reliability indexes for the subsystem with relatively small failure hazard and higher reliability indexes for the subsystem with more parts but fewer critical parts, and the allocation result is more reasonable compared with the allocation result of the traditional AGREE method.