The Research On Level Swirling Internal Energy Dissipation In Discharge Tunnel Within Differient Contraction Ratio Of Generator

There is a problem of high dam and large discharge and narrow river valley and difficulty in disposing discharge & energy dissipation in the course of development of hydraulic engineering in west china. But the traditional used energy dissipation scheme often causes a series of insurmountable difficulties, such as fogging, cavitations demolition, and bank scouring .It will cost a great deal of money in order to build a division tunnel ,but it's only a temporarily built .It will be a new energy dissipation way that using division tunnel as a discharge tunnel——level swirling internal energy dissipation discharge tunnel with shaft inlet, now more and more researcher give attention to it.This article have a research on its hydraulic characteristic during high head above the weir,huge discharge in its different contraction ratio of generator through theory analysis and experimental comparison. The writer refer to literature and theory study, by model test, acquire much innovative and engineering valuable result, no matter what extent and deepness, this study possess explore and auspicate. At the base of problems of discharge & energy dissipation and disadvantages of silo dissipation in the course of development of water and electricity in china, putting forward the tentative idea of level swirling internal energy dissipation sluice tunnel with shaft inlet, comparing this novel type with traditional ones, expatiating it's characteristics. This article mainly analysis its hydraulic character in different contraction ratio0.25,0.35,0.45,0.55 through hydraulics model test.The primary work and key result of this model test as follows:(1) In the experiment process, by observing the flow condition in different contraction ratio ,comparing with original basic flow condition, considering the sluice tunnel long factor, we deem that it has a transition condition between the free flow condition and suck up flow condition. In little contraction ration(0.25,0.35) the flow condition is complication ,and in larger contraction ration(0.45,0.55),the flow condition vary opposite simply, and it does not appear drown flow condition.(2) The dissipation number increased with the increase of contraction ration, the dissipation number have increased 39.8% between contraction ratio 0.35 and 0.45 ,but only 8.38% between 0.45 and 0.55.Byanalyzing the experiment data ,get the empirical formula about the dissipation coefficientμ,Froud number Fr and the water head between upstream and downstream.(3)Analyzed air cavity diameter,air cavity pressure,the surface pressure of sluice tunnel and the change regulation of flow angle with the discharge tunnel axis in transition site when the contraction ratio varies .(4)By calculating the surface pressure in the junction of generator and sluice tunnel that is easy subject to cavitation destroy, it finds that the possibility of affection of cavitation in 2 27 l 3l . we should attach importance to the matter in application.(5) Through rough estimate of system ratio of damping, It can gets a good result in system ratio of damping to 71%～89%.The research gets the subsidy of national natural funds...