设置阻塞后旋流洞内的增压特性分析

为解决高水头泄洪时旋流洞内出现较小压强和空化风险等问题,提出了新型的阻塞旋流泄洪洞,该文对设置不同阻塞时的洞内压强特性、增压特性和空化特性进行了模型试验和理论分析。结果表明:设置阻塞后洞内压强增大明显,一定阻塞时起旋器出口附近负压消失;竖井段壁面压强增大主要受起旋器喉口压强影响,旋流洞段主要受切向流速沿径向分布和水流流层厚度影响;随阻塞增大的压强-顶托压强沿程呈分段变化特征,但在竖井洞段和旋流洞段具有较好的保持性;推导了顶托压强的计算表达式并予以试验验证;阻塞大大降低了空化空蚀风险。旋流洞内设置阻塞可以较好地解决高流速时泄洪洞内的负压和空化风险问题。

ANALYSIS ON PRESSURIZING CHARACTERISTICS OF ROTARY FLOW IN SPILLWAY TUNNEL CAUSED BY BLOCKER

The rotary flow spillway tunnel with a blocker was proposed for meeting the requirements of the low pressure and cavitation erosion at high reservoir level. Then the characteristics of wall pressure, pressurization qualities and cavitations of flow with different blockers were analyzed by experimentation and theoretical methods. The results show that the wall pressures in whole tunnel are increased obviously because of the blocker, meanwhile, the negative pressures in the generator outlet are vanished. The increase reason of pressure in shaft is due to the pressure in its outlet, but in the spiral section it is associated with the radial distribution of tangential velocity and thickness of a flow layer. The increased pressures caused by a blocker vary along the tunnel, but keep constant in shaft and spiral section. Then the increased pressure expressions are put forward and verified by experiment. The cavitation erosion was also avoided by a blocker, by which, negative pressures and cavitations of flow with high velocity in the tunnel will be averted effectually.