| Scope of study. The purpose of the study was to design, construct and test a small low-cost crossflow water turbine with the possibility of introducing a similar design to rural villages in the tropics. The turbine was constructed out of discarded aluminum plates. It was designed with an interchangeable runner. Four 6-inch runners with 10, 15, 20 and 30 blades each were constructed. The study sought to evaluate the performance of the turbine using each of the 4 runners. A fifth runner was added later to the tests by cutting down the number of blades in the 30-blade runner to 6. The turbine and the runners were subjected to various levels of flow rates. Further, each runner was tested over a wide range of rotational speeds.;Optimum power or efficiency and rotational speed were determined for each runner. An output power and efficiency prediction equation was developed using dimensional analysis. This equation was compared with theoretical efficiency equations derived by other authors.;Findings and conclusions. The aluminum-constructed turbine performed most efficiently with the 20-blade runner. A maximum efficiency of about 47 percent was attained at a rotational speed of 330 rpm. The derived prediction equation for power and efficiency yielded values that were only half of the values from theoretical efficiency equations developed by previous authors. The derived equation is limited only to the same turbine size as the one tested. However, it can be used as a model to design other sizes of crossflow water turbines. |
