A New Method for Dynamic Analysis of Pelton Runners Using CFD/FEM Interaction Available to Purchase

The description of the dynamic behavior of a Pelton runner during normal operation is getting more and more of interest in the design of such kind of turbines. In fact, the aim to increase the performance imposes runner designs that can become critical from a structural point of view. Each bucket is subjected to a certain number of impulses per revolution corresponding to the number of nozzles. This high frequency load could lead to a great dynamic response of the runner if some kind of resonance takes place. For these reasons, a complex harmonic analysis is to be performed during the runner project, in order to avoid any crack arising during operation. This paper describes a new method to obtain the dynamic response due to the impulse load. A Pelton runner was modeled and simulated by using a FEM code (ANSYS) and a CFD (CFX) code in order to obtain its complete dynamic behavior. By using the CFD code the complete pressure profile was derived at any point of the bucket and at any time. Whilst by using the FEM code a complex harmonic analysis was computed. Combining the information of these two simulations the behavior of the stress versus time can be derived, theoretically at any point of the runner. The results of these analysis were compared with some experimental data giving a pretty good matching.