ME 4232: FLUID POWER CONTROLS LAB. Class #5 Valve Modeling

Transcription

1 ME 4232: FLUID POWER CONTROLS LAB Class #5 Valve Modeling

2 Notes No Office Hours Today Upcoming Labs: Lab 9: Flow Divider Lab 10: Sequencing Circuits 2

3 Agenda Wrap-up: Leakage Calculations Fluid Compressibility Fluid Inertia Valve Modeling Pressure Reducing Valve Directional Control Valve Research: High-Speed 3-way valve 3

4 Flow Combiner/Divider Valve 4

5 5

6 Review: Fluid Compressibility Bulk Modulus dv V 1 dp Change in pressure required to change volume of a given volume l 1 l 2 L n 1 2 keq A l l m ll m 12 if l l, then 2 n 1 2 A Lm 6

7 Fluid Inertia 7

8 Power Calculations 8

9 Pressure Reducing Valve What equations can you write to describe the valve function? 9

10 Directional Control Valve 10

11 Directional Control Valve 11

12 Valve Sizing / Lapping 12

13 Research Topic: Control of Hydraulic Circuits Throttling Valves Fast response Fluid throttled to desired output pressure Excess power converted to waste heat Variable Displacement Pumps More efficient Large, heavy, and expensive Switch-Mode Control Rapidly switch between efficient on and off states Pulse-width modulated output Applicable to pumps, motors, or actuators 13

14 Switch-Mode Hydraulics Power Electronics Hydraulics Boost Converter 14

15 Disc Style Valve Architecture Advantages: Axial Flow (no pumping) Clearance Not Dependent on Manufacturing Tolerance Duty Cycle and Frequency Are Independent Low Switched-Volume Balanced Pressure Forces 16

16 Modeling Flow and Pressure in the Circuit Modeling Sources of Energy Loss Throttling Losses (fully open and transitioning) Leakage Losses Compressibility Losses Viscous Friction Losses Optimization 17

17 Throttling Loss P valve _ full P Tier1 P Tier ATier1 ATier C d ATier1 ATier 2 Q Q 2 Q Cd ATier Cd ATier 2 2 Large throttling losses during transitions Check valves used to maintain flow 18

18 Leakage Losses Leakage flow assumed to follow parallel plate leakage and orifice flow Q leak Perimeter c 12 L 3 P Q orifice C d 2 A P 19

19 Compressibility Losses e 1 1 R P oil R high V P P V high tank inlet e E comp P high P tan k V 20

20 Viscous Friction Losses Viscous friction between face of valve plate and Tier 1 & Tier 2 sections T Viscous friction along valve circumference (Petroff s Eqn) T plate, f, o journal Fr 2 rr 0 rr Au c b o 2 t R f c r dr d r 4 4 r R R bore r vp c f 3 bore 2c f bore o 21

21 Optimization Maximize Efficiency Optimization parameters: Port inner radius Port outer radius Port span angle Clearances Outer radius of valve plate 22 Variable Symbol Value Inner Radius R i 5mm Outer Radius R o 17.6mm Port Span VP δ π/8 Port Span γ 7π/8 Tiers Axial Clearance c 25.4μm Bore Clearance c bore 1mm Bore Radius R bore 24.7mm Flow Rate Q 36 liters/min System Pressure P high 16MPa

22 Optimized Overall Efficiency Power Loss Summary Throttling 38.7% 399 Watts Leakage 34.4% 354 Watts Compress 11.9% 121 Watts Viscous 15.3% 158 Watts Total 1032 Watts 23

23 Alpha Prototype 24

24 Alpha Prototype: Experimental Results 2 Output Pressure vs. Time for Duty Ratio Pressure(MPa) Time(s) Pressure(MPa) Output Pressure vs. Time for 0.5 Duty Ratio Time(s) 64 Hz Switching Frequency 38% Efficiency due to Leakage Alignment Challenges Pressure(MPa) Output Pressure vs. Time for Duty Ratio Time(s) 25

25 Prototype Redesign Enable Four Quadrant Control 4-way valve Improve Alignment Improve Phase Shift Actuation Reduce External Fluid Conductors Investigate Bearing Alternatives Hydrodynamic Magnetic 26

26 Integrated Directional Valve 27

27 Beta Prototype 28 Energy Loss (J) per Rev Percentage Losses (%) Compressibility Viscous Friction Leakage Throttling

28 Current/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 switching 29

29 Research Topic: Fluid Compressibility in Digital Hydraulics Major Form of Energy Loss Widely Varying Bulk Modulus Models Goal: Understand the Role of Fluid Compressibility on the Performance and Efficiency of Switch-Mode Circuits 30

30 Bulk Modulus Models dp V dv Bulk Modulus: Many Models Available in Literature Basic: Akers et al. 1 VT Va 1 Va 1 1 Va 1 V V V e T T a T a Merritt P e R P Hayward P R P R P P Po o e Cho et al. Bulk Modulus (GPa) P e P Po R1 c1 P P o P Pressure (MPa) 31 Bulk Modulus vs. Pressure for R = Yu et al. Cho et al. Hayward Merritt

31 Experimental Validation Vary: Entrained Air, Pressure, V switched Measure: Density, Bulk Modulus, Efficiency 32

32 Bulk Modulus Calculation Based on Sonic Velocity: 2 2 L e c Cross-correlation of Pressure Waves T 33

33 2 Minute Writing No Student Names What is going well in your lab group? Any issues I should be aware of? TA name if appropriate 34