Blade Depth Investigation on Cross-flow Turbine by Numerical Method

Abstract

In 2016, more than 1060 million people in the world lived in areas that are difficult to access, causing insufficient access to electricity. To overcome the problem, a pico hydro cross-flow turbine is considered to be a proper solution because it has a simple design, has few civil works, is easy to maintain, and can operate at a medium head with high variation of discharge. To increase the turbine's performance, this study aims to find the effect of blade depth on performance and to investigate the possibility of a cross-flow turbine being a reaction turbine. The CFD method was selected because it can represent the flow pattern in a turbine with more detail than other methods. The blade depth variation in this study consists of 0 mm, 3 mm, 6 mm and 9 mm, and the pressure inlet boundary conditions are varied with heads of 2.7 m and 5 m. The model turbulence RNG k-є standard has been used to predict turbulent flow. From the 2.7 m head, the average efficiency with the ratio U/V 0.42-0.5 produced by blade depth are: 0 mm is 41.9%, 3 mm is 45.8%, 6 mm is 34.4% and 9 mm is 36.7%. Meanwhile, the variations from the 5 m head are: 0 mm is 49.8%, 3 mm is 57.3%, 6 mm is 53.7% and 9 mm is 49.6%. A two-factor ANOVA without replication was performed to determine the relationship of blade depth to performance, and the results showed there is an effect because the F-critical was higher than F. In addition, the blade does not entirely convert the water's kinetic energy to power. Thus, the reaction turbine concept cannot be used in cross-flow turbines because there is no lift force produced by any blade in the two conditions.