Reliability design method for steam turbine blades

Abstract

Based on theories of probability and statistics, and taking static stresses, dynamic stresses, endurance strength, safety ratios, vibration frequencies and exciting force frequencies of blades as random variables, a reliability design method for steam turbine blades is presented. The purport and calculation method for blade reliability are expounded. The distribution parameters of random variables are determined after analysis and numerical calculation of test data. The fatigue strength and the vibration design reliability of turbine blades are determined with the aid of a probabilistic design method and by interference models for stress distribution and strength distribution. Some blade reliability design calculation formulas for a dynamic stress design method, a safety ratio design method for fatigue strength, and a vibration reliability design method for the first and second types of tuned blades and a packet of blades on a disk connected closely, are given together with some practical examples. With these methods, the design reliability of steam turbine blades can be guaranteed in the design stage. This research may provide some scientific basis for reliability design of steam turbine blades.

References

1. Shi Jinyuan, Yang Jing, Chen Mingqiang . Statistical analysis of the reliability for steam turbineblades. Mechanical Strength, 1989, (11): 18–20 (in Chinese)
2. Kapar K C, Lamberson L R . Reliability in EngineeringDesign. New York: John Wiley and Sons, 1977
3. Shi Jinyuan . Study on reliability design for fatigue strength of steam turbineblades. In: Proceedings of the 5th Notional Conference on Fatigue. Guangzhou: South China University of Technology Press, 1991 (in Chinese)
4. Shi Jinyuan . Statistical analysis for test frequencies of steam turbine blades. Turbine Technology, 1987, (2): 27–33 (in Chinese)
5. Shi Jinyuan, Yang Yu, Sun Qing, et al.. Study on design criteria of strength and vibrationas well as life for subcritical and supercritical steam turbines. Chinese Journal of Mechanical Engineering, 2005, 41(1): 189–192 (in Chinese)