淹没射流与水平旋流梯级内消能工的水力特性

Hydraulic characteristics of two-stage internal energy dissipators with submerged jet and horizontal swirl flow

为解决导流洞改建为单一内消能泄洪洞出现的空蚀问题,作用水头难以提高,运行方式和灵活性有限等工程实际问题,提出了一种新型"淹没射流与旋流梯级内消能工"。通过模型试验对其基本流态与水力特性进行量测和分析,结果表明:竖井水位是保证稳定运行的关键条件,当其高于射流尾水洞洞径的1.2倍后,各部分流态均趋于稳定;上游水位与下游水位均会影响竖井水位,其中上游水位影响更为显著;射流孔口和起旋器孔口的无量纲泄流量与其相对净作用水头均为线性增大关系;在射流段、水平旋流洞段与旋流阻塞扩散段,壁面压强沿程呈现出明显的分三段降低、各段稳定变化的特征。本文试验条件下,各段的最大压强水头差与总水头的比值分别为0.12、0.47和0.2,射流和旋流两级消能最大净作用水头占总水头的比例分别为0.13～0.15和0.59～0.80,最大孔口流速26.2 m/s,射流尾水和旋流扩散段的最大断面平均流速10.5 m/s,14.5 m/s,表明其具有良好的分级分段的消能特性,体型基本合理,但总作用水头尚有较大的提高余地,分级消能的比例尚需进一步优化。

This paper describes a new type of two-stage internal energy dissipators with submerged jet and horizontal swirl flow, aiming at cavitation erosion of the discharge tunnel with internal energy dissipators reconstructed from a diversion tunnel, practical engineering difficulties in increasing effective hydraulic head, and limitation on operation modes and flexibility. Basic flow patterns and hydraulic characteristics are measured and analyzed using scale model tests of tunnel dissipators of this type. The results show that the water level in the shaft is a decisive factor to ensure stable operation, and that the entire flow tends to be stable when this level is above 1.2 times the diameter of submerged-jet tunnel. It is affected by the water levels of the tunnel’s inflow and tail flow, with a more significant effect of the former. In the sections of jet orifice and pipe cyclone orifice, the dimensionless flow rates are increased linearly with the increase in relative net effective heads; in the three sections of submerged jet, horizontal swirl flow and vortex diffusion, wall pressure shows a distinct three-stage drops and a stable variation along each section. Under the experimental conditions in this study, the ratios of pressure head drops in the three sections to the tunnel’s working head are 0.12, 0.47 and 0.2 respectively, and the ratios of net effective heads of the two dissipators, i.e. the submerged-jet section and swirl flow section, are in the ranges of 0.13 to 0.15 and 0.59 to 0.80 respectively. And flow velocity around the two orifices is no higher than 26.2 m/s, and average flow velocities at the outlets of the jet section and vortex diffusion section are 10.5 m/s and 14.5 m/s respectively. All this shows that our design of the tunnel is good and reasonable in its two-stage energy dissipation and basic shapes, but much room is still left to improve the tunnel’s working head and further optimize the allocation of dissipated energy to different stages.