Power Station Long Diversion Pipe Transition Process

The water-carriage system, consisting of derivation works, head conduit and tail conduit, is a necessary part of hydropower station and for pressure derivation power plant, it also includes derivation tunnel and surge chamber. The problem of non-steady flow in pressure water-carriage system, due to the change of operation state of hydropower station, is of two types: one is fluctuation of pressure phenomenon, which rapidly disseminates and suddenly change, called water hammer; and the other is water level change of surge chamber follows the water body movement, called oscillation of surge chamber. The non-steady flow in pressure water-carriage system have quite influence on the stability and safety of operation of hydropower station, so it is paid more attention. And there are studies on the water hammer of hydropower station and surging wave of the surge chamber for the study on the pressure non-steady flow. This paper is mainly on the water hammer of hydropower station:i. Construction of the equation of coefficient of water hammer passing through the surge chamber.Assuming that the intersection of the surge chamber, lower pressure derivation tunnel and higher pressure conduit is equivalently a node (where the pressure is constant and the discharge satisfies the equation of continuity) , the equation of coefficient of water hammer passing through the surge chamber is derivation based on the basic equation of water hammer, considering characteristics of throttled surge chamber.ii. Calculating method of water hammer in derivation system of hydropower station with a throttled surge chamber.When calculating water hammer force in derivation conduit with a surge chamber, the ordinary method usually thinks that the surge chamber can completely reflect the water hammer wave. But in practically, there are kinds of factors quite influence the reflection, so if being without these factors, the result maximum force of water hammer has a negative deviation and it isn't safe for the design of derivation tunnel. This paper provides a new reasonable method to calculate the force of water hammer in conduit with a throttled surge chamber.iii. Analyzing the effects of factors on coefficient of water hammer passing through the bottom of surge chamber.According to the characteristics of throttled surge chamber, this paper analyzes the effects of surge chamber, the relations between the area of throttled hole and of derivation tunnel, the length of throttled hole and of the derivation conduit on water hammer passing through the surge chamber.iiii. Calculation of transient process of Da Huashui hydropower station.The transient process of derivation system is calculated and it is used to test and verify the effects of factors on the coefficient of water hammer passing through the surge chamber and eventually, the optimal design is obtained.