3D Dynamic Simulation of a Flow Force Compensated Pressure Relief Valve

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 OlivettiOMIQ s.r.l. - Italy

Politecnico di TorinoDipartimento Energia

Fluid Power Research Laboratoryhttp://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

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Flow forces in poppet valves

setFpS

Pressure setting(opening of flow area)

Pressure relief valve

Change of fluid momentum Flow force(closing force)

cosflF Q v

DensityFlow rate Fluid velocity

The regulated pressure increases with the flow rate(undesired behaviour)

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Flow force compensation

Fluid deflector

Radial outlet

Ideally the flow force is null

Backwards deviation

Net opening force Compensation of the

spring force increment

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VALVE UNDER STUDY

IN

OUTdeflector



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

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sliding

fixed deformable

Flow rate at inletAtmospheric pressure at outlet

Boundaryconditions



Main model features

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• 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



Mesh refinement

15Mesh density in the minimum flow area

Pressure with imposed poppet lift

Lift: 1 mmFlow: 50 L/min

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coarse

medium

finevery fine

A

B

Pressure with calculated poppet lift

Configuration analysed1: A & B coarse grid2: A & B medium grid 3: A medium – B fine grid4: A medium – B very fine5: A & B very fine grid

62.8 101

2

34 5



Experimental facility

Valve with transducers

FMF2

HE

RQ2: two-port flow control valveFM: turbine flow meterP1 (100 bar) & P2 (20 bar): pressure transducersF1 & F2: oil filtersHE: water-oil heat exchanger

Determination of Flow (Q) - pressure (p)steady-state curve

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Steady-state curves

3 different pressure setting

Ideal valve vertical line(regulated pressure not function of flow rate)

Real valve without deflectorRegulated pressure increaseswith flow rate Q (flow force effect)

Real valve with deflectorThe flow force is compensated,above all at high pressure

cosflF Q v

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Velocity and pressure fields

Flow rate 40 L/minSetting 75 bar

Gas volume fraction

Cavitation model

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Influence of deflector angle

45° 0°

Deflector force increases with:• The rim angle• The pressure setting

(higher fluid velocity)p

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Pset =



Lumped parameter model (LMS Amesim)

flow sourceconical 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

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Poppet lift [mm]

Flow rate [L/min]

Forc

e [N

]

CFD model

• 3D map in Matlab• 20x20 square matrix• linear interpolation in Amesim



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

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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)

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Fluid Power Research Laboratorywww.fprl.polito.it

Politecnico di Torino

3D Dynamic Simulation of a Flow Force Compensated Pressure Relief Valve

Engineering

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