A study on the effect of blade inlet angle, attack angle and the diameter ratio on the efficiency of a Banki Mitchell turbine

In the present work, a theoretical investigation is presented on how the efficiency of a Banki Mitchell turbine is affected by its design parameters. With the help of general formulation of the control volume theory to the equation of the moment of momentum in the turbine’s runner and considering all assumption regarding the properties of the flow and the design geometry of the runner, a mathematical model has been developed. The water discharge through the turbine is considered incompressible, non-viscous, homogenous and steady flow; The loss due to shock on the inner and outer surface of the runner as well as leakage losses are neglected. As results of the present study, the behaviour of hydraulic efficiency was determined when varying the angle of attack, the blade entry angle as well as the runner diameter ratio, indicating their appropriate values in each different scenario. In this paper critical relationships between design parameters have been disclosed and therefore analysed and simulated using Simulink MATLAB. Furthermore, it was mentioned that for a better performance, the exit angle of the blade should be 90°. At length, an expression was given estimating the turbine’s efficiency at various operating conditions and for calculating the energy contribution per stage, respectively.

Keywords:

Banki Mitchell Turbine, Fluid Mechanics Analysis, Control Volume Theory Efficiency.,

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