Cross Flow Turbine usually for micro hydro-electrical power plant application especially for isolated areas. Increasing power efficiency still the most interesting topic for researches. One of the method to increase it was to control the inflow of water from the first stage to the second stage of banki blades to be a good flow trajectory and did not strike the shaft using a draft tube. This research aimed to investigate the draft tube length variations against the flow from the first stage to the second stage of Banki turbine, so that good flow trajectory, uniform color velocity contour and avoid shaft struck could be obtained. There were 2 variants runner casing and 3 variants length of draft tube, 140 mm, 240 mm, and 340 mm. The 2D and 3D geometry were drawn in CAD software, while Flow Simulation test using Solidwork Flow Simulation with a discharge of water 2 m3/min and head 5.5 m. From simulation results, shown that the second variant C2-2 was the highest efficiency and the best flow trajectory.

The draft tube is a component in the Kaplan turbine to create positive suction pressure using kinetic energy that is not used when leaving the turbine runner and increasing turbine power efficiency. This research aimed to find out the highest efficiency of variant geometries of a conical draft tube with spiral liner and without the spiral liner. The design geometry was processed using 2D software and 3D using Inventor and simulated in CFD software. The inlet water discharge was 0.1 m³s−1 with head 5 m and theoretical turbine power 4.9 kW. Based on the simulation results showed that the spiral liner draft tube variant was the best power and efficiency.