Contents. Diaphragm in pressure pipe: Steady state head loss evolution and transient phenomena. Nicolas J. Adam Giovanni De Cesare

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1 Diaphragm in pressure pipe: Steady state head loss evolution and transient phenomena Nicolas J. Adam Giovanni De Cesare Contents Introduction FMHL pumped-storage plant Experimental set-up Steady head losses Transient head losses Conclusion

Introduction ELECTRICITY MARKET CONTEXT Demand is still growing: expected to

of electricity in OCED Europe (GWh) IEA () + + % per year 99 IWR () Fossil

OECD Europe Evolution of electricity production in Germany Liberalization of

International exchange of electricity (Switzerland) Net import/export blance

2 Introduction ELECTRICITY MARKET CONTEXT Demand is still growing: expected to double by The part of renewable (wind + solar) is still increasing Production of electricity in OCED Europe (GWh) IEA () + + % per year 99 IWR () Fossil Nuclear Hydro electricity Solar Wind Others Total production of electricity in OECD Europe Evolution of electricity production in Germany Liberalization of European electricity market Introduction SWISS MARKET HYDROELECTRICITY International exchange of electricity (Switzerland) Net import/export blance in Switzerland () Total production of electricity in Switzerland distributed by category ()

Introduction HIGH HEAD POWER PLANT Role of surge tank Reducing the water hammer Improve the regulation of turbines Damping of the acceleration and deceleration of flow in the pressure tunnel Forces

3 Introduction HIGH HEAD POWER PLANT Role of surge tank Reducing the water hammer Improve the regulation of turbines Damping of the acceleration and deceleration of flow in the pressure tunnel Forces Motrices Hongrin-Léman Swissdam Lake Hongrin: Normal elevation: m.a.s.l Minimum elevation: m.a.s.l Water volume: ' m Catchment area: 9 km (natural: km + adduction: km ) (Hachem et al., ) Lake Geneva: Elevation: 7 m.a.s.l Water volume: 89 km

Forces Motrices Hongrin-Léman (Hachem et al.

capacity: x MW Flow capacity (generation): m /s Flow capacity (pumping): m /s

ch Veytaux I plant 7 , ) Photo perso de la visite New powerhouse Under construction

4 Forces Motrices Hongrin-Léman (Hachem et al., ) Existing powerhouse Commisionned in 97 Maximum head: 878 m Existing generation capacity: x MW Flow capacity (generation): m /s Flow capacity (pumping): m /s Annual generation: 7 GWh Natural generation: 88 GWh Pumped generation: GWh Veytaux I plant 7 Forces Motrices Hongrin-Léman (Hachem et al., ) Photo perso de la visite New powerhouse Under construction New generation capacity: MW + MW New flow generation: 7 m /s New flow pumping: m /s 8

5 Forces Motrices Hongrin-Léman (Hachem et al., ) (Hachem et al., ) (Hachem et al., ) 9 Experimental set-up EXPERIMENTAL CHARACTERISTICS Froude similarity Scale: /8. Set of discharges: 8 discharges from to l/s Determination of pressure: Linear relation between signal and piezometric value Data acquisition: Hz s

6 Experimental set-up PREVIOUS STUDY Determination of head losses to obtain the target head losses by varying β C: none C: β=.7 C: β=.77 D d C: β=.7 t GOAL OF THIS STUDY ) Evolution of the head losses by varying the position in the connecting tunnel for C and C ) Temporal evolution of head losses during an emptying of the surge tank Head loss coefficient DEFINITION H k v g where: H is the head losses, k the head loss coefficient, v the flow velocity and g the gravitational constant Z Up p Up g v Up g Z Dn p Dn g v Dn g H

7 Steady head losses RESULTS Head losses : ΔH [m] Head losses : ΔH [m] ΔH =.8 K R² =.9977 ΔH =.9 K R² = Kinetic energy: v /g [m] P a ΔH =.89 K R² = ΔH =.7 K R² = Kinetic energy: v /g [m] d =. m P c Head losses : ΔH [m] Head losses : ΔH [m] ΔH =. K R² =.998 ΔH =.9 K R² = Kinetic energy: v /g [m] P b ΔH =.88 K R² =.998 ΔH =.8 K R² = Kinetic energy: v /g [m] d=.8 m P d Steady head losses RESULTS Headloss coefficient : Position to the axis of the headrace tunnel: X [m] BC CB Headloss coefficient : Position to the axis of the headrace tunnel: X [m] BC CB Comments: For the flow coming from the surge tank B: More the orifice is close to the T-junction, higher is the head loss coefficient. These is no effect for the bigger internal diameter. For the flow going to the surge tank B: More the orifice is close to the T-junction, lower is the head loss coefficient. Idem: No effect on the bigger orifice. 7

8 Steady head losses Headloss coefficient : Position to the axis of the headrace tunnel: X [m] BC CB Blevins BC (98) Headloss coefficient : Position to the axis of the headrace tunnel: X [m] BC CB Blevins (98) Comments: Literature relation does not predict correctly the head loss coefficient. Influence of the flow conditions Transient head losses EXPERIMENTS STEPS. The surge tank is filled.. The downstream valve is opened as quick as possible.. The transient pressures and discharge are recorded. Duration of the experiments: s 8

9 Transient head losses RESULTS Discharge : Q [ - m /s] 8 Valve opening Time : t [s] Head : H [m] Head : H [m] Comments: First part of experiments are influenced by the valve opening Time Time : t : [s] t [s] S S Discharge drops linearly. 7 Transient head losses RESULTS Head loss coefficient: Time : t [s] Time Instantaneous coefficient Instantaneous coefficient Steady coefficient Time : t [s] Instantaneous coefficient Steady coefficient per. Mov. Avg. (Instantaneous coefficient) Head loss coefficient: Head loss coefficient. Head loss coefficient: Comments: For a decrease of discharge: Transient head losses is always under the steady one. There are or drop steps. 8 9

10 Conclusions STEADY HEAD LOSSES The upstream and downstream flow condition influence the head losses through an orifice. This induces more iterations to obtain the expected orifice. Literature value are only used for long and straight flow conditions. TRANSIENT HEAD LOSSES For a decrease of discharge, the head loss coefficient is always under the steady one. Next steps: Study a increase of head losses 9 Conclusions STEADY HEAD LOSSES The upstream and downstream flow condition influence the head losses through an orifice. This induces more iterations to obtain the expected orifice. Literature value are only used for long and straight flow conditions. TRANSIENT HEAD LOSSES For a decrease of discharge, the head loss coefficient is always under the steady one. Next steps: Study a increase of head losses

11 Outlooks for the thesis SCIENTIFIC Better understanding of flow through a throttle constriction, orifice, in pressurized pipe Influence of geometry of throttles in pressurized pipes on local head losses Interaction between flow behaviour and head losses through throttles in pressurized systems PRACTICAL Creation of a catalogue summarizing head losses as function of different orifices for a practical use. Establishment of correction factor as a function of flow conditions and junction geometries Thank you for your attention Diaphragm in pressure pipe: Steady state head loss evolution and transient phenomena Nicolas J. Adam nicolasjean.adam@epfl.ch Giovanni De Cesare

Head loss coefficient through sharp-edged orifices

Head loss coefficient through sharp-edged orifices Nicolas J. Adam, Giovanni De Cesare and Anton J. Schleiss Laboratory of Hydraulic Constructions, Ecole Polytechnique fédérale de Lausanne, Lausanne, Switzerland