MODIFICATION IN CROSS FLOW TURBINE FOR EFFICIENCY IMPROVEMENT

Abstract

The popularity of the turbines under micro hydro lies in the fact that they are less costly and can be fabricated locally. There are various types of turbines that can be used in micro hydro. Cross-Flow turbine has been considered techno-economically viable for such sites. A cross flow type runner has a drum shape consisting of two parallel discs connected together by a series of curved vanes or blades. The water from the nozzles strikes the vanes and convert 2/3rd part of the potential into the mechanical power. The water that comes out from the blade, strikes the diametrically opposite vane and the remaining conversion of 1/3`d part takes place. Cross flow type runner can be fabricated locally, which results in the poor efficiency. The vanes can be made even from the pipes cut along the length. Also this kind of runner is suitable for low discharge and high head conditions, which is a common case in the hills. The problem with the fabrication of cross flow turbine runner at the local level is that its efficiency decreases due to lack of proper design and fabrication. The low efficiency is the basic inspiration to improve the existing design of cross flow runner. There is a scope of efficiency improvement in cross flow turbine by guiding the water jet from first stage to second stage with the help of a guide tube. This study presents the design modifications in cross flow turbine. The runner was designed and fabricated by providing the guide tube. The guide tube is designed and fitted with the runner. The cross flow turbine has been tested before providing guide tube and after fitting guide tube. It has been observed that the efficiency of cross flow turbine is increased by introducing guide tube to guide the crossing flow towards the second stage of the runner. This study intends to design the cross flow turbine runner with guide tube to improve the efficiency. The modified runner can be used for further study in order to improve the performance of a cross flow runner considering other design parameters such as providing draft tube.