Zexia H., Qin S., Feng L., Yonghua T.

Turbine disk is a very key component in rocket engine operating in high temperature and rotating speed, as well as experiencing great aerodynamic loads. Its failure will lead to unsteady operation of rocket engine, and sometime cause catastrophic consequence. Fatigue cracking failure of turbine disk was found in hot fires tests of XX rocket engine. A series of calculation and analysis were present to determine failure causes. Structural dynamic characteristics in high temperature and high rotating speed environments were emphasized. The dynamic characteristics analyses results provided exact input data for the dynamical response calculation. By comparing the calculated results with the test data of turbo pump in hot fires, it is found that one of modal frequencies of the original structure coincides with the six-times of rotating speed frequency. For one operation condition, coupling modal frequency appears at 550? and 9078rpm of disk; For another one, a coupling modal frequency appears at 480? and 9282rpm of disk. The dynamic response calculation results show that high stress level exists in the turbine disk when high amplitude resonance occurring. Sometime, it may cause cracking damage of turbine disk. After structural redesign, this kind of coupled modal has been avoided in the improved structure. Also, the improvement design can effectively decrease stress concentration and increase the fatigue strength of the area. The succeeding hot fire tests demonstrated the success of the improved design.