Energy contributes significantly in almost all aspects of human life as well as economic activities and plays a crucial role in the infrastructural development of a county to alleviate poverty. Generating energy from a renewable source such as small hydropower through the application of pump operating as a turbine mode called Pump as Turbine is one of the best alternatives to provide clean and inexpensive energy. Using Pump as Turbine helps in generating reasonably priced hydroelectric power for communities in underdeveloped counties. This study investigates the effects of internal flow behaviour and performance of Pump as Turbine under different rotational speed and flow rate. The rotational speed is an essential physical parameter as it affects the Pump as Turbine operation. A model-specific speed centrifugal pump model with head 32 (m), flow rate of 12.5 (m³/h) and the rotational speed of 2900 rpm, has been selected for the study. Numerical simulations have been conducted using the k-ω turbulence model to solve three-dimensional (3D) equations. The pump mode experimental data were used to confirm the results for better analysis. The results predicted that vortex and turbulent kinetic energy increase per rotational speed increase. Also, at the higher rotational speed, very high recirculation of flow is detected at the blade suction chamber, although the pressure side has a smooth flow. This study provides beneficial information which will serve as a reference to help improve PAT performance along with selecting PAT for a small hydropower site. Future works will consider the impact of blade thickness and cavitation in Pump as Turbine.

中文翻译：

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可再生能源发电中水轮机内部流动物理数值模拟的计算分析

能源在人类生活的几乎所有方面以及经济活动中都起着重要作用，并且在减轻贫困的县的基础设施发展中起着至关重要的作用。通过应用称为涡轮泵的涡轮机模式的泵来从可再生资源（例如小水电）中产生能量是提供清洁和廉价能源的最佳替代方法之一。使用泵作为涡轮机有助于为欠发达县的社区提供价格合理的水力发电。本研究探讨了在不同转速和流量下内部流动行为和作为涡轮的水泵性能的影响。转速是必不可少的物理参数，因为它会影响水轮机的运行。特定型号的转速离心泵型号，扬程为32（m），³ / h）和2900 rpm的转速已被选择用于研究。已经使用k- ω湍流模型进行了数值模拟，以求解三维（3D）方程。使用泵模式实验数据来确认结果，以进行更好的分析。结果预测，涡旋和湍动能随转速的增加而增加。同样，在较高的转速下，尽管压力侧的流量平稳，但在叶片吸气腔中仍可检测到非常高的流量再循环。这项研究提供了有益的信息，这些信息将有助于提高PAT性能，并为小型水电站选择PAT。未来的工作将把叶片厚度和气穴的影响视为涡轮机。