Banki (cross-flow) türbini tasarım parametrelerinin incelenmesi

Abstract

SUMMARY In this thesis the effects of inlet nozzle geometry, run ner design parameters and the working conditions on the effi ciency of Banki turbines have been studied. Banki turbines, also called cross-flow turbines are well known examples for small water turbines. This type of turbines have such advantages as capacity control being possible, com paratively high efficiency, simple construction, the ability to be manufactured by local industry, the easiness of mainta- nance and repair. Banki turbine works on the impulse principle and consists of a runner and a inlet nozzle with a rectangular cross-section. The runner is simply made of a series of radi ally curved blades connected by two circular parallel discs. The thesis consist of two main parts. In the first part, in order to study the influence of design parameters on the efficiency of such turbines, an experimental rig which consists of a water recirculation system and a Banki turbine has been set up at the Mechanical Engineering Laboratories of Karadeniz Technical university. To study the effect of the geometry of the runner and the inlet nozzle, 5 different types of inlet nozzle and 4 types of runner were used in the first series of experiments. To determine the effects of inlet nozzle geometry, the pressure distribution along the walls of the nozzle were measu red in the second series of experiments. In the third, the effects of the ratio of the diameter, number of blades and the thickness of the jet at the exit of the nozzle were investigated by using 13 different runner geo metry. In addition, the influence of the number of blades and ratio of diameter on the variation of the ratio of peripheral velocity to absolute velocity were studied. A new type of nozzle with a guide vane which was located inside the flow was designed and some test results were obtained. In the theoretical part of thesis, the flow outside the nozzle was assumed to be potential. Boundary element method was used to calculate the path of the trajectory of the free jet. The flow fields around the guide vane and near the exit of the nozzle were also computed. The theoretical solutions were compared with that of experimental results. The main conclusion drawn from this study is that for Banki turbines, the number of blades, ratio of the diameter of runner and head can be varied within a wide range of values. Finally, both experimental and theoretical results were compared with the published results given in literature, and some proposals for future work were presented. Key words: Banki turbine, Cross-flow turbine, Mitchell turbine Ossberger turbine, Boundary Elements Method. VII