CE 704 · Chapter 6
Hydropower Engineering past question
6.3 Penstocks and Pressure shaft: importance, conditions of their application, general arrangement, hydraulic transients (water hammer), Computation of hydrodynamic pressure, sizing of penstock/pressure shaft and estimation of thickness of steel in penstock/pressure shaft
Derive an expression for minimum upsurge without damping effect in the surge chamber using continuity and momentum equations. In a storage hydropower plant, water is delivered from upper impounding reservoir through low pressure headrace tunnel and three high pressure penstocks to three francis turbine units. The elevation of reservoir and tailwater level are 320 m and 200 m above datum respectively. It is decided to design a simple surge tank between headrace tunnel and penstocks for sudden rejection or demand of two units. If the maximum and minimum water level elevation in the surge tank is limited to 330 m and 310 m above datum respectively due to topography and construction difficulty, determine the minimum permissible length of low pressure headrace tunnel to fulfill the design objective. Given data: Discharge in tunnel=100 m³/s; Head race tunnel: diameter-7 m and head loss in tunnel=10% of gross head of system; Penstocks: each length 500 m, diameter 2.5 m, f=0.016. [3+7]