PERFORMANCE ANALYSIS OF CROSS-FLOW TURBINE

Abstract

A promising corner of the future hydropower market remains the economical and ecologically acceptable exploitation with micro hydro range sites, where conventional turbines are neither economical nor ecologically undisputed. In hilly region micro hydro up to 100 kW have momentous role in utilization of mechanical power and electricity generation. The capacity of micro hydro power plant up to 5.0 kW is considered under development of water mill program by Ministry of New and Renewable Energy (MNRE), Govt. of India. The popularity of the turbines under micro hydro lies in the fact that they should be 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. 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. A cross flow turbine has a drum shape runner consisting of two parallel discs connected together by a series of curved vanes or blades. 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. Number of attempts has been made to improve the efficiency of cross flow turbine by adapting certain fluid machines related concepts. Many studies have been done for different parameters in cross flow turbine. Efficiency of turbine was found to be greater for shaft-less turbine. But there was scope lying to research the efficiency parameter with variation of shaft diameter. In present study, CFD analysis is done for efficiency parameter. Diameters taken for study are 50, 40,30,20,10 mm and shaft-less diameter. From the results, it is found on decreasing the diameter of shaft pressure is found to be decreasing at the nozzle inlet. But there is a slight increment in the pressure when the shaft diameter approaches to zero. And maximum output power is obtained when the shaft diameter approaches to zero value. Hydraulic efficiency of cross flow turbine is found to be inversely proportional to shaft diameter. The increase in the value of hydraulic efficiency is about 5% when there is no shaft present as compared to the case when there is shaft of diameter 50 mm inside the runner.