"This thesis work investigates the applicability of literature recommendations regarding specific speed and Zweifel coefficient for low head axial hydraulic turbines with constant blade thickness circular arc blade profiles, and no inlet guide vane. Highest efficiency was observed in Computational Fluid Dynamics (CFD) investigations for the designs running at speeds 12-33% that of the speed recommended by the Cordier line. Designs that followed the Zweifel coefficient recommendations of the literature in range of 0.8-1.1 demonstrated highest efficiency in CFD investigations. To test the applicability of the Cordier line recommendations for machines of this type, designs at differing specifications were tested at six different rotational speeds. Peak efficiency was measured at specific speeds between 1.4 and 1.9, compared to the Cordier-recommended value of 5.5 to 6.1. Next designs with differing values of Zweifel coefficient were simulated at the rotational speed at which highest efficiency was measured for each set of specifications. Zweifel coefficient was altered by changing the axial blade length. It was found that highest efficiency was measured at Zweifel coefficients between 0.8 and 1.1. The designs with higher axial blade lengths had lower Zweifel coefficient, and experienced greater friction losses. Decreasing blade length and increased Zweifel coefficients were correlated with more severe velocity gradients at the leading edge, increased flow deviation and areas of low pressure where cavitation could occur. Designs with the shortest blades (Zwefiel coefficient above 1.2) experienced greater velocity gradients and turbulence at the trailing edge and decreased efficiency."--Page ii.
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