配水环作为冲击式水轮机的给水机构, 主要起着调节流量、诱导分流的作用, 其特殊的结合结构使流体在管内流动时会产生流动分离、Dean涡等不良现象, 从而诱发水力损失。针对这一问题, 该文研究了配水环管流道内部流动的水力损失特性, 采用SST k-ω湍流模型, 基于熵产理论, 得到了不同入口速度下流场的熵产分布, 重点分析了主流道和分岔口2内产生水力损失的原因。结果表明, 在整个配水环中, 管内总熵产随着入口速度增加而增加, 从210.999 W/K增加至4 614.980 W/K; 而流体流经弯折处所产生的内外侧流动分离, 在高速流动下更加明显。流场损失以脉动熵产占优, 占比超过50%;水力损失主要发生在环管主流区及分岔口2处, 约占总损失90%, 而分岔口1、3位置损失较小; 在分岔口2处, 高速流体分流后向外侧挤压导致内侧形成低压而产生涡流, 从而诱发了较为显著的水力损失; 在弯管位置, 因流动惯性而产生的流动分离是造成水力损失的主要原因。这些不良流动现象会在环管内外侧形成较大的压力梯度, 使得流场出现较大幅度的压力脉动, 进而影响流动稳定性。

Objective: The distributing pipe in a Pelton turbine serves as a crucial water supply component responsible for regulating flow and inducing diversion. Its special structure, however, can lead to adverse effects such as flow separation and Dean vortices causing hydraulic losses; these losses can vary with changes in the upstream head, further affecting the incoming flow conditions. Traditionally, the pressure drop method has been primarily utilized to assess these losses, yet it fails to pinpoint the exact locations where significant hydraulic losses occur. Methods: This study investigates the hydraulic and loss characteristics of the distributing pipe. Utilizing the SST(shear stress transport) k-ω turbulence model, we simulate the flow inside the distributing pipe and analyze entropy production distribution based on the entropy production theory. Then, according to the distribution of entropy production rate and flow pattern, the reasons for the hydraulic loss in the main channel and bifurcation 2 were analyzed detailly. Entropy production—indicative of irreversible dissipative effects during fluid flow—effectively highlights high hydraulic loss areas by converting lost mechanical energy into internal energy. Results: Results show a remarkable increase in total entropy production within the pipe, with values rising from 210.999 to 4 614.980. Specifically, entropy production in the main channel increases from 145.549 to 3 477.351, and in bifurcation 2 from 38.857 to 717.608. Under high-speed flow conditions, the separation between internal and external flows becomes distinct, particularly when fluid navigates bends. The hydraulic loss is dominated by fluctuation entropy production, accounting for >50%. The main flow zone and bifurcation 2 are the primary sites of hydraulic loss, accounting for approximately 90% of the total loss, whereas bifurcations 1 and 3 experience relatively small losses. Conclusions: Comparative analysis of entropy generation rate contours, streamline plots, and pressure fluctuation curves highlights that high entropy generation areas experience significant pressure pulsations, accompanied by adverse flow phenomena such as Dean vortices and flow separation. At bifurcation 2, high-speed fluid is diverted and squeezed outward, creating a low-pressure vortex on the inner side, inducing significant hydraulic loss. At the bend position, the fluid tends to flow outward, resulting in high external pressure and low internal pressure distribution at the ring pipe and further in high hydraulic loss on the inside. These phenomena create large pressure gradients and significant pressure fluctuations, affecting flow stability. Furthermore, optimization strategies are proposed for the distributing pipe design, including the addition of flow-diversion baffles at bifurcation points to stabilize flow patterns, reduce vortices, and alleviate flow separation by increasing the number of nozzles and reducing curvature. This study employs numerical computation to investigate the mechanisms of hydraulic loss generation within the distributing pipe and meticulously delineates areas of high hydraulic losses, offering hydro turbine developers optimization strategies.