Experimental comparison of the upstream head using the non-rotating model of the vertical ultra-low head hydro turbine with its prototype

Abstract

A vertical ultra-low head (VULH) turbine is a pico-scale hydro turbine applicable to open canal flow with or without head drop. This conceptualized turbine rotates at a lower speed. In the case of water flow on a canal without head drop condition, the prediction of the upstream head is challenging due to the change in the direction of the water flow path on this conceptualized system. Assuming the head at the primary level of design, an experimental study has been conducted to judge the upstream head of water flow using the two-dimensional non-rotating model (NRM) before the use of a prototype of the turbine. The runner was designed with a conventional method whereas the design of NRM was based on the diameters of the runner designed and the orifice openings on it. The experiments were conducted on a newly developed VULH Turbine test rig of size 10 m x 1.5 m x 2 m with a maximum flow rate capacity of 120 LPS and a maximum upstream head of 0.75 m. The tests were completed for upstream head variation using three different sets of NRM having an orifice cut angle of 15°, 18°, and 22.5° and a prototype of the runner at a constant speed for different flow rates. From the comparisons made, the closest NRM was selected that showed a similar upstream head at the maximum efficiency point of the runner. The research concluded with the finding that the NRM can be used to predict the upstream head of the VULH turbine instead of the rotating model.