Abstract For applications involving very low specific speeds resulting from very low flow rates with medium to high heads, a special class of hydraulic turbine known as Positive displacement turbine (PDT) is most suited. These turbines are not very common, but they can effectively harness the micro and Pico hydropower. For the present work, the effect of inlet and outlet pipe’s cross-sectional shape on the fluid flow pulsations and overall performance of the developed PDT has been analyzed using Computational Fluid Dynamics (CFD) approach. Initially, the cross-sectional shape of the pipe used for transporting the working fluid to and from the turbine rotors was circular. Subsequently, the influence of square and rectangular cross-sectional shaped pipe designs was analyzed. Also, parametric studies were performed to find the dimensions of rectangular and variable cross-sectional shaped pipes. It was observed that the initial flow pulsations greatly reduced for specified variable cross-sectional pipe compared to the other shapes. Also, an increment of 0.824% in hydraulic efficiency was observed compared to the initial circular pipe. At the rated conditions, the PDT with twisted rotors having fully circular shaped pipe developed 7.15 kW of output power with a hydraulic efficiency of 66.2% from the experimental study.

中文翻译：

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进出水管形状对容积式水轮机流量脉动特性影响的参数研究

摘要 对于涉及由中至高扬程的非常低的流速导致的非常低的比速度的应用，一种称为正排量涡轮 (PDT) 的特殊类型的水轮机最适合。这些涡轮机不是很常见，但它们可以有效地利用微型和皮克水电。对于目前的工作，使用计算流体动力学 (CFD) 方法分析了入口和出口管道的横截面形状对开发的 PDT 的流体流动脉动和整体性能的影响。最初，用于输送工作流体进出涡轮转子的管道的横截面形状是圆形的。随后，分析了方形和矩形截面异型管设计的影响。还，进行了参数研究以找出矩形和可变截面形状管道的尺寸。据观察，与其他形状相比，指定的可变横截面管道的初始流动脉动大大减少。此外，与初始圆形管道相比，观察到水力效率增加了 0.824%。在额定条件下，具有全圆形管道的扭曲转子的 PDT 输出功率为 7.15 kW，水力效率为 66.2%。