Experimental Study Of Flow In Hydraulic Draft Tube Based On PIV Technology

Flow inside hydroturbine has great influences on its energy characteristics as well as unit stability. In particular, the vortex in the draft tube is an important factor which affects unit stability. Therfore, the research of flow in the hydraulic draft tube is continuouly receiving everbody's attention. Presently, experimental research and numerical simulation are main ways of investigating the inner flow field. Although with the development of computer technology, mathematics and mechanics, mathematical simulation is developed very fast and some experiments can be avoided, it could not substitute physical simulatation, and could not provide intact operating characteristics for new hydraulic machinery, so experiments are still the principal ways to obtain datum.PIV testing system is quickly developed with the development of computer and imagery processing softwares. It is an important technology for experimental research of the internal flow field of hydraulic machinery, and more and more experimental researches are developed to use PIV testing system. It applies to a large scope from low speed to supersonic velocity, from steady flow to unsteady flow, from gas to liquid and all kinds of fluid flow field testing. Its measuring accuracy basically satisfies the requirements of modern testing technology. It is a reliable modern flow field testing method.The author carried on entire flow field experimental research to the flow field of hydroturbine runner outlet (hydraulic draft tube taper tube) by PIV testing system (including PIV measuring method and data processing technology). Through flow field testing, the author obtained some realiable experimentalresults, such as pressure distribution, velocity distribution and other related datum of hydraulic draft tube interior flow. These results will be useful in improving design of flow passage in hydraulic turbine.