Drafttube modellingfor predictionof pressure fluctuations on prototype

Size: px

Start display at page:

Download "Drafttube modellingfor predictionof pressure fluctuations on prototype"

Lizbeth Sharp
5 years ago
Views:

1 Drafttube modellingfor predictionof pressure fluctuations on prototype S. Alligné, C. Landry, C. Nicolet, F. Avellan 3-4 juin 2015 SHF Machines hydrauliques et cavitation Cetim Nantes 74 route de la Jonelière France

2 Contents Problematic Methodology 1D modelling System Cavitation flow in draft tube Experimental investigations at reduced scale model Identification of DT parameters Dimensionless numbers Prediction on prototype Eigenmodes Forced response 2

3 Problematic Reduced scale model Prototype Direct transposition of pressure fluctuations 1D simulation model 3

4 Methodology 4

5 Methodology 5

6 SIMSEN SIMSEN software: Hydraulic circuit Electrica installations Rotating inertias Control system 6 Modeling from water to wire

7 1D Modelling Piping system modelling: Mass and momentum equation: H i Q 1 Q 2 D, a, λ H 1 H 2 dx Electrical analogy: (Bergeron, 1950; Paynter, 1953 ) L h /2 R/2 R/2 L h /2 H ci C Q i Q i H i+1 R h Datum. 2 H a Q + = 0 t ga x H x U t U x 1 + ga 1 + Ce + L e Q t I x I t λ Q + 2gDA = 0 + R e I = 0 Q = 2 0 Storage Losses Inertia 7

8 Turbine characteristic: Dimensionless factors: Unit speed factor: 1D Modelling Unit discharge factor: Unit torque factor: 8

9 1D Modelling Cavitation draft tube flow S.Alligné, C. Nicolet, Y. Tsujimoto, F. Avellan, Cavitation Surge Modellingin Francis Turbine Draft Tube, In Publication process for Journal of Hydraulic Research, 2014 Vc = (,, ) f Q h Q 1 2 dq Q Q = χ + C dt c dh dt C V h c c = = V χ c 1 = Q 1 gadx 2 a Q Q Q Q h τ 0π D µ '' Q + K x S 2 h = ga t ga x ga x ρga ρga x Convective terms (New) Divergent geometry (Tsujimoto et al.) A K x = x Dilatation viscosity (Pezzinga et al.) 9

10 1D Modelling Cavitation draft tube flow: Lumped model Distributed model Nb=1 Nb=32 10

11 1D Modelling Draft tube model parameters: Wave speed a Second viscosity µ '' : dissipation induced by the phase change during cavitation volume fluctuations Excitation source S h : induced by the vortex rope Mass flow gain factor χ 1 : not considered Effect of parameters: a µ '' and influence damping α ( a, µ '') and frequency f ( a, µ '') of eigenmodes The excitation source is external to the system S h 11

12 Methodology 12

Landry, A. Favrel, A. Müller, C. Nicolet, F.

13 Σ Q ɶ in physical ( A, f ) s s ( a, µ '') Identification of & f p fs Resonance identification Eigenfrequency & amplitude response Forced Response Q ɶ in ( As, fs = f p ) Eigenmodes h ɶ Σ Simsen ΣSimsen (, '') f a µ p a ( p ) hɶ f f p hɶ ( f p ) f p '' µ C.Landry, A. Favrel, A. Müller, C. Nicolet, F. Avellan, Experimentalidentification of the local wave speed and the second viscosity in cavitating drafttube flow, In Publication process for Journal of Hydraulic Research, 2015 Comparison New set of parameters ( a, µ '') 13

14 Identification of S h C.Landry, EPFL Thesis N 6547, 2015 Σ h ɶ ( f rope ) physical e S h f rope ( S, e, x ) h f rope s Σ Simsen Forced Response hɶ ( f rope ) Comparison New set of parameters ( S, e, x ) h s x s 14

15 Methodology 15

16 Dimensionless Numbers Wave speed a and µ '' second viscosity C.Landry, A. Favrel, A. Müller, C. Nicolet, F. Avellan, Experimentalidentification of the local wave speed and the second viscosity in cavitating drafttube flow, In Publication process for Journal of Hydraulic Research, 2015 ρ a p p 2 w Π = = out v g ( β ) M µ '' f ρc = = Π ( 1 β ) p p ρ '' natural 2 2 out v w 16

17 Cavitation Mapping C. Landry, EPFL Doctoral Thesis N 6547, 2015 β σ ( ),, n Q Fr ED ED Transposition Law P M β = β Froude similitude respected! 17

18 Excitation Source Mapping S ( ) h σ n, Q, Fr ED ED S e x H = P P M ref h Sh M H ref P C.Landry, EPFL Thesis N 6547, 2015 Transposition Laws D P M ref = e M D ref P D P M ref h = xh M D ref Froude similitude fulfilled! 18

19 Methodology 19

20 Prototype - 1D Modelling SIMSEN System model n ED, Q Fr σ ED β ρ a p p 2 w Π = = M out v g ( β ) µ '' f ρc = = Π ( 1 β ) p p ρ '' natural 2 2 out v w a( t) µ ''( t) 20

21 Prediction of eigenmodes DT parameters and predicted eigenmodes Unstable eigenmodes with lumped model 21

22 Prediction of eigenmodes Shape of pressure and discharge 1st eigenmode Distributed Constant Parameters Distributed Variable Parameters Small changes on eigenmodes shapes 22

23 Prediction of pressure fluctuations 2 investigated OP Eigenmodes Excitation source 23

24 Prediction of pressure fluctuations System response 8.2% H turb 1.2% H turb 24

25 Conclusions Methodology applied for transposition of pressure fluctuations on reduced scale model to prototype: Prediction of different amplitudes as function of the OP Froude similitude should be respected Mass flow gain factor neglected Second campaign planned Could change predicted amplitudes Measurements on prototype scheduled for validation β P = β M 25

26 HYPERBOLE HYdropower plants PERformance and flexible Operation towards Lean integration of new renewable Energies LMH Laboratory for Hydraulic Machines 26

27 Merci pour votreattention! Power Vision Engineering Sàrl 1, ch. Des Champs-Courbes CH-1024 Ecublens Switzerland 27

Reduced scale model testing for prediction of eigenfrequencies and hydro-acoustic resonances in hydropower plants operating in off-design conditions

Reduced scale model testing for prediction of eigenfrequencies and hydro-acoustic resonances in hydropower plants operating in off-design conditions A Favrel 1, J Gomes Pereira Junior 1, C Landry 2, S