Sensitive analysis of the inlet boundary conditions on the turbine 99 draft tube

Abstract

This work focuses on establishing the response of the global coeffcient performance when the inlet boundary conditions are drastically changed. For this, a systematic objective and qualitative method called Fractional Factorial Design has been used, which evaluates the main and joint effects on the draft tube performance parameters. This method is applied to numerical models in the limits of the grid convergence curve. The results obtained showed that after the change of the inlet boundary conditions, even though a numerical difference exists among the global performance parameters of the numerical models, they have the same tendency and behavior. In addition, the energy loss coeffcient showed an important sensitivity to the inlet boundary conditions change, compared to the average pressure coefficient which is usually used as objective function in a draft tube optimization process. Thus, a numerical model with a coarse grid density could be used when the process requires a large number of analyses, changing drastically the inlet velocity condition and knowing that the results obtained will be acceptable and computationally economical.