Influence Study On The Hydraulic Transients Of The Equivalent Diversion Tunnel Length

Hydraulic transients is a common hydraulic phenomenon during the operation of the hydropower station。the waterhammer pressure and the surge waves in the adjuster brought about by the hydraulic transients will challenge the safety of the water diversion systerm, especially the pressure piping system, so the study of hydraulic transient, especially about its influence factors will has very important practical significance,in not just avoiding the unsteady flow accidents but also ensuring the safety and stable operation of hydropower station. In this paper the impact on hydraulic transients by the hydraulic equivalent length of diversion tunnel will be studied take the example of the Shi Touxia hydropower station.Firstly ,based on the theory of pipe flow transients and adopting the method of characteristics, This paper developed the mathematical model for the hydraulic transient process which happened in the normal operation of the hydropower station , and the mathematical model are used to compute the hydraulic transient process in some certain working conditions. And its compute result provides reference basis for the following study about the change of the diversion tunnel length. Then the length of the diversion tunnel will de changed in different proportion with equivalent treatment, the so-called "equivalent" means that some proportional local head losses will be introduced to make sure the total head losses during the diversion tunnel can not be changed.so is the hydraulic equivalent. Then do some adjustment in the program structure according to the above operating . Compute the hydraulic transients process in the same working conditions and compare its result with the initial reference results, get the impact on hydraulic transients by such change of the diversion tunnel length. It is that some hydraulic character parameters of the transient process,mainly refers to the waterhammer pressure and the surge waves in the adjuster,will reduce in varying degrees with the shortening length of the diversion tunnel under the precondition of hydraclic equivalent.According to this topic, in order to verify numerical calculation results above mentioned, we have design the whole physical model of the water system, after the the normal hydraulic transient model test, execute the so-called equivalent change in the diversion tunnel of physical model and do the same hydraulic transient experiment research again under the same working condition. The experimental results show that it agree with the numerical calculation results.Based on the conclusion and combined with the curve reflecting the relationship between the tunnel length variation and the hydraulic parameters variation, give the curve fitting and get the function equation which provide modify reference for equivalent model test results.This method improve the flexibility of the selection because of the shortening of the tunnel length when we design the physical model test , so it has very practical reference value and important research significance.