Class #5Valve ModelingME 4232:FLUID POWER CONTROLS LAB2Notes• No Office Hours Today• Upcoming Labs:– Lab 9: Flow Divider– Lab 10: Sequencing Circuits3Agenda• Wrap-up: – Leakage Calculations– Fluid Compressibility– Fluid Inertia• Valve Modeling– Pressure Reducing Valve– Directional Control Valve– Research: High-Speed 3-way valve4Flow Combiner/Divider Valve56Review: Fluid Compressibility• Bulk Modulus– Change in pressure required to change volume of a given volume1dVdPV121212if , then 2eqnnkAllmllmAllLml1l2L7Fluid Inertia8Power Calculations9Pressure Reducing ValveWhat equations can you write to describe the valve function?10Directional Control Valve11Directional Control Valve12Valve Sizing / Lapping13Research Topic:Control of Hydraulic CircuitsThrottling Valves• Fast response• Fluid throttled to desired output pressure• Excess power converted to waste heatVariable Displacement Pumps• More efficient• Large, heavy, and expensiveSwitch-Mode Control• Rapidly switch between efficient on and off states• Pulse-width modulated output• Applicable to pumps, motors, or actuators14Switch-Mode HydraulicsPower Electronics  HydraulicsBoost Converter16Disc Style Valve ArchitectureAdvantages:• Axial Flow (no pumping)• Clearance Not Dependent on Manufacturing Tolerance• Duty Cycle and Frequency Are Independent• Low Switched-Volume• Balanced Pressure Forces17Modeling• Flow and Pressure in the Circuit• Modeling Sources of Energy Loss– Throttling Losses (fully open and transitioning)– Leakage Losses– Compressibility Losses– Viscous Friction Losses• Optimization18Throttling Loss Large throttling losses during transitions Check valves used to maintain flowfullvalveP_22212122TierdTierdTierTierACQACQPP22212222122TierTierdTierTierAACAAQ 19Leakage Losses• Leakage flow assumed to follow parallel plate leakage and orifice flowLPcPerimeterQleak123PACQdorifice220Compressibility Losses11eoil highRRPhigh tank inletePPVVVPPEkhighcomptan21Viscous Friction Losses• Viscous friction between face of valve plate and Tier 1 & Tier 2 sections• Viscous friction along valve circumference (Petroff’s Eqn)boreborevpjournalcRtT32 4420,,2oborefRrRrffofplateRRcrcrddrrrcuAFrTbo22OptimizationVariableSymbol ValueInner RadiusRi5mmOuter RadiusRo17.6mmPort Span – VPδπ/8Port Span –Tiersγ 7π/8Axial Clearancec 25.4μmBore Clearancecbore1mmBore RadiusRbore24.7mmFlow RateQ 36 liters/minSystemPressurePhigh16MPa• Maximize Efficiency• Optimization parameters:– Port inner radius– Port outer radius– Port span angle– Clearances– Outer radius of valve plate23Optimized Overall EfficiencyPower Loss SummaryThrottling 38.7% 399 WattsLeakage 34.4% 354 WattsCompress 11.9% 121 WattsViscous 15.3% 158 WattsTotal 1032 Watts24Alpha Prototype25Alpha Prototype:Experimental Results• 64 Hz Switching Frequency• 38% Efficiency due to Leakage• Alignment ChallengesOutput Pressure vs. Time for 0.167 Duty Ratio00.511.520 0.02 0.04 0.06 0.08 0.1 0.12Time(s)Pressure(MPa)Output Pressure vs. Time for 0.5 Duty Ratio00.511.520 0.02 0.04 0.06 0.08 0.1 0.12Time(s)Pressure(MPa)Output Pressure vs. Time for 0.833 Duty Ratio00.20.40.60.811.21.41.60 0.02 0.04 0.06 0.08 0.1 0.12Time(s)Pressure(MPa)26Prototype Redesign• Enable Four Quadrant Control– 4-way valve• Improve Alignment• Improve Phase Shift Actuation• Reduce External Fluid Conductors• Investigate Bearing Alternatives– Hydrodynamic– Magnetic27Integrated Directional Valve28Beta PrototypeEnergy Loss (J)per RevPercentage Losses (%)Compressibility 5.27 33.0Viscous Friction 4.76 29.8Leakage 3.65 22.8Throttling 2.32 14.529Current/Future Work• Experimental Testing of Beta Prototype Underway• Future work:– Multi-actuator circuits– Investigate bearing alternatives– Integrated hydraulic accumulator – Vibration analysis– Efficiency improvements (viscous friction, compressibility)– Soft switching30Research Topic:Fluid Compressibility in Digital Hydraulics• Major Form of Energy Loss• Widely Varying Bulk Modulus ModelsGoal: Understand the Role of Fluid Compressibility on the Performance and Efficiency of Switch-Mode Circuits31Bulk Modulus ModelsBulk Modulus: • Many Models Available in LiteraturedPVdVBasic: Akers et al.11111Ta a aeT Ta TaVV V VVV VePRPoeoPRPRPPP1111111eooPPPRcPP P MerrittHaywardCho et al.0 5 10 15 20 25 30 3500.20.40.60.811.21.41.61.82Pressure (MPa)Bulk Modulus (GPa)Bulk Modulus vs. Pressure for R = 0.020 Yu et al.Cho et al.HaywardMerritt32ExperimentalValidation• Vary: Entrained Air, Pressure, Vswitched • Measure: Density, Bulk Modulus, Efficiency33Bulk Modulus CalculationBased on Sonic Velocity:• Cross-correlation of Pressure Waves22eLcT 342 Minute Writing• No Student Names• What is going well in your lab group?• Any issues I should be aware of?• TA name if