![Politecnico di Torino
Dipartimento Energia
Fluid Power Research Laboratory
http://www.fprl.polito.it
Lumped parameter model (LMS Amesim)
flow source
conical poppet
active surfaceclearancemass &
endstops
poppet lift signal
flow rate signal
Good results with CFD … but also need of fast a running model
Parametric model with loop-up table for flow force compensation
12 / 14
Poppet lift
[mm]
Flow rate
[L/min]
Force[N]
CFD model
• 3D map in Matlab
• 20x20 square matrix
• linear interpolation in Amesim](https://image.slidesharecdn.com/showimece16rundo-170105144258/85/3D-Dynamic-Simulation-of-a-Flow-Force-Compensated-Pressure-Relief-Valve-12-320.jpg)
3D Dynamic Simulation of a Flow Force Compensated Pressure Relief Valve
- 1. POLITECNICO DI TORINO - Italy Giorgio Altare and Massimo Rundo ASME 2016 International Mechanical Engineering Congress and Exposition Phoenix, November 16, 2016 3D Dynamic Simulation of a Flow Force Compensated Pressure Relief Valve Micaela Olivetti OMIQ s.r.l. - Italy
- 2. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Summary • Introduction: flow forces in poppet valves • CFD model in PumpLinx of a relief valve • Experimental facility • Analysis of the results • Tuning of a 0D model in LMS Amesim 2 / 14
- 3. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Flow forces in poppet valves set F p S Pressure setting (opening of flow area) Pressure relief valve Change of fluid momentum Flow force (closing force) cosflF Q v Density Flow rate Fluid velocity The regulated pressure increases with the flow rate (undesired behaviour) 3 / 14
- 4. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Flow force compensation Fluid deflector Radial outlet Ideally the flow force is null Backwards deviation Net opening force Compensation of the spring force increment 4 / 14 VALVE UNDER STUDY IN OUT deflector
- 5. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Mesh construction (PumpLinx ) Calculated poppet lift (moveable mesh) Types of grids: • Fixed • Sliding (integral with the poppet) • Deformable (3 types of surface) • Valve end: fixed surface locked nodes • Valve: mobile surface nodes anchored on the surface and sliding with it • Cylinder: fixed surface nodes slide along the cylinder generatrixes cylinder valve end valve 5 / 14 sliding fixed deformable Flow rate at inlet Atmospheric pressure at outlet Boundary conditions
- 6. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Main model features 6 / 14 • Finite volume method • Unstructured body-fitted Cartesian grids • Connection through mismatched grid interfaces (MGI) • identification of overlapped surfaces • area treated as internal interface and updated every time step Governing equations: • Turbulence model standard k-ε • Wall treatment: standard Wall Function • Cavitation and aeration modules (Equilibrium dissolved gas) • No dynamics in air solution/dissolution processes Numerics: • Spatial scheme: 1st order upwind • Temporal scheme: 1st order • Pressure-velocity coupling: Simple-S
- 7. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Mesh refinement 15Mesh density in the minimum flow area Pressure with imposed poppet lift Lift: 1 mm Flow: 50 L/min 7 / 14 coarse medium finevery fine A B Pressure with calculated poppet lift Configuration analysed 1: A & B coarse grid 2: A & B medium grid 3: A medium – B fine grid 4: A medium – B very fine 5: A & B very fine grid 6 2.8 10 1 2 3 4 5
- 8. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Experimental facility Valve with transducers FM F2 HE RQ2: two-port flow control valve FM: turbine flow meter P1 (100 bar) & P2 (20 bar): pressure transducers F1 & F2: oil filters HE: water-oil heat exchanger Determination of Flow (Q) - pressure (p) steady-state curve 8 / 14
- 9. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Steady-state curves 3 different pressure setting Ideal valve vertical line (regulated pressure not function of flow rate) Real valve without deflector Regulated pressure increases with flow rate Q (flow force effect) Real valve with deflector The flow force is compensated, above all at high pressure cosflF Q v 9 / 14
- 10. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Velocity and pressure fields Flow rate 40 L/min Setting 75 bar Gas volume fraction Cavitation model 10 / 14
- 11. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Influence of deflector angle 45° 0° Deflector force increases with: • The rim angle • The pressure setting (higher fluid velocity) p 11 / 14 Pset =
- 12. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Lumped parameter model (LMS Amesim) flow source conical poppet active surfaceclearancemass & endstops poppet lift signal flow rate signal Good results with CFD … but also need of fast a running model Parametric model with loop-up table for flow force compensation 12 / 14 Poppet lift [mm] Flow rate [L/min] Force[N] CFD model • 3D map in Matlab • 20x20 square matrix • linear interpolation in Amesim
- 13. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Validation of the tuned 0D model The Q-p curves are contrasted with the experimental data Acceptable behaviour for a 0D model Negligible CPU time Prediction of regulated pressure in a different operating condition: Pressure setting 30 bar – flow rate 30 L/min Difference between 0D – 3D model: 0.33 bar 13 / 14
- 14. Politecnico di Torino Dipartimento Energia Fluid Power Research Laboratory http://www.fprl.polito.it Conclusion A quite novel application of PumpLinx has been analyzed • The method for constructing the moveable mesh has been found • The correct evaluation of the deflector force requires a good cell refinement along the entire jet path • The cavitation model must be active to avoid negative pressures • Max error in pressure evaluation 2.5 bar at 70 bar (3.5 %) • The geometry of the deflector rim plays a fundamental role • In the 0D model the construction and the interpolation of the map force is crucial (force very sensitive to poppet position) 14 / 14
- 15. Fluid Power Research Laboratory www.fprl.polito.it Politecnico di Torino