A Comprehensive Reliability Evaluation Model of Turbine Runner Blades under Complex Conditions
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TECHNICAL ARTICLE—PEER-REVIEWED
A Comprehensive Reliability Evaluation Model of Turbine Runner Blades under Complex Conditions Zhaojun Li Xing Heng
. Xijun Mao . Fuxiu Liu . Yuyu Huang .
Submitted: 16 March 2020 / in revised form: 23 July 2020 / Accepted: 12 September 2020 Ó ASM International 2020
Abstract In this paper, a comprehensive method to evaluate the reliability of turbine runner blades under complex conditions has been proposed. The method takes into consideration the flow excitation parameters acting on the blades under different conditions, which present different uncertain information characteristics. The structural performance function of both vibration failure and fatigue failure of runner blades has been established, according to their vibration and fatigue characteristics. A probabilistic reliability model of the multi-failure modes of runner blades under their rated conditions has been established through application of random reliability theory, and a probabilistic non-probabilistic reliability model of the multi-failure modes of runner blades under non-rated conditions has been established by applying random reliability theory and non-probabilistic reliability theory, based on the structural performance function of both vibration failure and fatigue failure, taking into consideration the uncertain information characteristics of the flow excitation parameters that act on the runner blades under different conditions. On the basis of the two reliability models, a comprehensive model to evaluate the reliability of runner blades under complex conditions has been constructed. The reliability of the turbine runner blades under complex conditions has been analyzed through the use of examples, and the accuracy of the models has been proved using the Monte Carlo simulation (MCS). Keywords Runner blades Complex conditions Vibration failure Fatigue failure Reliability Z. Li (&) X. Mao F. Liu Y. Huang X. Heng College of Mechanical Engineering, Guangxi University, Nanning 530004, China e-mail: [email protected]
Introduction As the main load bearing, a load transferring part of a hydraulic turbine generator unit, the runner blades work in a hostile environment and bear a very complicated flow excitation [1–3]. Under the excitation of complex flow, the runner blades will violently vibrate, and fatigue cracks in the runner blades will be generated after gone through a long-term process of vibration. When the crack growth exceeds a certain size, the shape of the runner blades will be significantly changed. This situation will result in an imbalance in the hydraulic power, which will lead to a significant decline in the dynamic performance of the unit or even seriously affect the unit’s safety [4]. Therefore, it is necessary to consider not only the mode of the vibration failure of runner blades, but also the mode of the fatigue failure of runner blades, when evaluating the reliability safety of a runner blade. In their operating process, a runner blade not only goes through the startup and
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