Transient Start-Up Characteristics of an In-Pipe Spherical Hydraulic Turbine

Abstract

The purpose of this study is to analyze the rotational speed characteristics of a spherical turbine start-up process, and the rotational speed characteristic of the spherical turbine is studied by numerical simulation. In order to ensure the reliability of the numerical simulation, the numerical simulation results at different flow rates are compared with the experimental results, and the results show that it is feasible to investigate the rotational speed characteristics of the spherical turbine using numerical simulation. The numerical results demonstrate that the start-up process of the spherical turbine can be separated into two stages: the start-up acceleration stage and the transition stage, which are followed by periodic fluctuations of the rotational speed. In addition, when the flow rate is 8 m3/h, the spherical turbine can self-start under the load coefficient (Bg) if less than 3×10−5. If the Bg is larger than 3×10−5, the turbine fails to start-up. The failed start-up shares characteristics: the turbine only moves forward and backward alternately in a small angular range. However, eventually, the applied load torque dominates, and the turbine starts to reverse. It is found that the flow rate and the turbine rotational speed present a linear relationship under the no-load operating condition.