Optimization of the Runner for Extremely Low Head Bidirectional Tidal Bulb Turbine

Abstract

[...]the hydraulic characteristics for the prototype turbines with optimal runners were analyzed, and the pressure pulsations in the blade surface are predicted to ensure the stable operation of the tidal units. 2. The target of the optimization is to obtain the maximum of the overall efficiency for the ebb and flood turbine modes. [...]the objective function is defined in Equation (1): ηebb+ηflood=F({βj1},{βj2},{θj1},{θj2})=F(Xi);j=1,5; i=1,20 η=nπτ30ρgHQ where Q and H are the turbine discharge and head, n and τ are the rotational speed and moment acting on the runner, and ρ and g are water density and gravitational acceleration. There are no exact functions between the design parameters and the output targets for most engineering design problems. [...]response surface methodology (RSM) has been employed to describe the approximate functional relations of Equation (3) by using polynomials RSM, introduced by Box and Wilson in 1951, has been a well-known method for estimating the interaction effects among independent variables without implementing factorial design experiments for each level of every independent variable [12]. Frequencies that are multiples of fn are obvious in the pressure pulsations for point RS in the ebb turbine mode. [...]the frequency of 16fn, corresponding to 16 guide vanes (also known as rotor-stator interaction, RSI), commonly happens in a traditional turbine, and rarely has influence on this tidal turbine.