多用途水工隧洞水力特性及运行方式研究

水利水电工程中的过水隧洞有导流洞、泄洪洞、放空洞以及发电引水洞等,它们各自具有一定的水流适用条件,对单一用途的水工隧洞,其洞内水流特性较容易把握。当由于技术、经济条件让一条隧洞具备多种用途时,隧洞将面临着不同运行阶段显著的水力差异性考验。结合某水利工程多用途水工隧洞水力模型试验,研究了集导流、泄洪、放空及发电引水等功能于一体的陡坡隧洞在不同运行阶段的相关水力特性。结果表明当作为泄洪隧洞在正常工况下运用时,隧洞进口前和洞内流态均较正常,洞内最小压力满足水工隧洞设计规程要求;当作为导流隧洞和放空洞运用时,隧洞进口在一定水流条件下会形成吸气型立轴漩涡,并在洞内形成形态不断变化且不断溃灭的气囊,在较长的洞段及较大的流量区间内,洞内还会出现明满交替流以及发电支洞岔管引起的明流冲击波、水流折冲等不良流态,上述水流现象会引发洞壁的有害振动或空蚀破坏。通过试验优化,并结合隧洞末端工作闸门的合理调度,提出了多用途水工隧洞的安全运行方式。

Hydraulic Characteristics and Operation Mode of Multipurpose Hydraulic Tunnel

In water conservancy and hydropower projects , hydraulic tunnel can be divided into diversion tunnel, spillway tunnel, emptying tunnel and water diversion tunnel for power generation, etc. Each of them has a certain flow condition, and it’s easy to control the hydraulic characteristics for a single-purpose tunnel. But when a tunnel has a variety of uses due to technical and economic conditions, the tunnel will be faced with significant hydraulic differences in various operation stages. In this paper, we researched the hydraulic characteristics of slope tunnel which integrates functions of diversion, flood discharge, emptying, and diversion for power generation in different operation stages by hydraulic model test of a water conservancy project. Results reveal that when the tunnel is used as spillway tunnel under normal operation, the flow pattern is normal at the tunnel inlet and in the tunnel, and the minimum pressure in the tunnel meets the requirements of specifications; when it’s used as diversion and emptying tunnel, vertical suction vortex is formed at inlet under certain flow conditions, and air bag whose shape changes and collapses constantly is formed in the tunnel. In long tunnel section and large flow range, mixed free-surface-pressure flow as well as free flow shockwave and deflected flow caused by the bifurcated pipe for power tunnel will also occur. Such flow patterns could induce harmful vibration of tunnel wall and cavitation. Furthermore, through experimental optimization and associated with reasonable dispatch of terminal working gate, the safe operation mode for multipurpose hydraulic tunnel is put forward.