Abstract: As required in CCAR33.27 airworthiness regulation, the determination of rotor burst rotating speeds using tests and analysis methods should consider the most adverse combination of temperature and temperature gradients. Therefore, to meet the requirements of CCAR 33.27, the impacts of temperature fields to rotor over-speed strength have to be evaluated accurately in aircraft engine design. As an example, this paper analyzes a low pressure turbine rotor with six stages of disks using the ultimate strain method. The results of temperature distribution related to the redline speed and room temperature conditions are compared in terms of deformation patterns and stain growth characters in the most critical disk, as well as predicted burst rotating speed and failure initiation location. Based on these comparisons, the validity criteria are proposed for rotor over-speed analysis methods applied to high temperature applications, which are validated by room temperature tests. The analyses show that at high temperature conditions related to the redline speed, the burst speed of the rotor is significantly lower than that under room temperature, and the lower burst speed at high temperature is mainly due to the substantially reduced yield strength of the materials.

Key words: aircraft engine rotor, over-speed, burst, temperature, dimension