ERC C&E Fluid Power 1 ROTARY SELF-SPINNING HIGH SPEED ON-OFF VALVE Center for Compact and Efficient Fluid Power Department of Mechanical Engineering University of Minnesota Dr. Perry Li Dr. Tom Chase Dr. Jim Van de Ven Haink Tu Rachel Wang Mike Rannow

ERC C&E Fluid Power 2 Throttle-less Control Valve control wastes energy Heat loss through throttle valve Generate excess flow Direct pump control Produces energy only when needed

ERC C&E Fluid Power 3 Drawbacks of Direct Pump Control Currently available variable displacement pumps tend to be ~3 times heavier than a fixed displacement pump Variable displacement pumps are more expensive than fixed displacement pumps A valve controls a piston which controls a swash plate which controls the flow Complex control Slow response times Goal: Design a compact, efficient, and responsive method of control

ERC C&E Fluid Power 4 Concept Use switching to eliminate throttling losses Create the hydraulic analog of a DC-DC Boost Converter Controlled using Pulse-Width-Modulation (PWM) Same concept can be applied to motor, hydrostats, hydraulic transformer

ERC C&E Fluid Power 5 Operation of a PWM Pump 2 States of Operation Open State Pump flow is diverted through the On/Off valve to tank Energy is stored in the flywheel The load is driven by the accumulator Closed State Energy is pumped into the accumulator Energy is withdrawn from the flywheel Low PQ loss through the valve in both states Switching leads to a ripple on the output to the load

ERC C&E Fluid Power 6 Ideal Model u(t)=1 when the valve is closed u(t)=0 when the valve is open Controlled using PWM s(t) is the duty ratio Adiabatic accumulator operation Use state-space averaging u(t) becomes s(t) In steady-state:

ERC C&E Fluid Power 7 Experimental Results: Power Loss Results show significant improvement over valve control Switching effects cause energy loss to increase with frequency Compressibility Valve transition Slight increase in power loss as more flow is diverted Full open throttling Experimental Apparatus: 5.7 l/m flow rate, 4.8 MPa load pressure, 10 Hz max frequency, 40 ml inlet volume, 0.4 MPa drop across the valve

ERC C&E Fluid Power 8 s=0 (Flow fully diverted) s=.25 s=.5 (50% flow to application) s=.75 s=1 (100% flow to application) To Tank To Application Decrease s (more flow to tank) Increase s (more flow to application) Tangential rhombus inlet nozzle Helical barriers/ inlet turbine blades Outlet turbine blades Spool Functionality No spool acceleration /deceleration Rotary actuation power  PWM frequency^2 Linear actuation power  PWM frequency^3 Use helical profile to apportion flow between application (on) or tank (off) as the spool rotates Move the spool axially to determine duty ratio Utilize fluid to spin spool Transition time scales with spool speed

ERC C&E Fluid Power 9 Valve Packaging Integrated Design Mounts directly onto existing fixed displacement pumps Reduces inlet volume and losses due to fluid compressibility

ERC C&E Fluid Power 10 Prototype Parts

ERC C&E Fluid Power 11 x y A in R in ω Inlet turbine stageOutlet turbine stage c out R out ω Control Volumes (for 1 of N sections) V out =Q/A axial k V in =Q/(N·A in ) j V in =Q/A axial k V out =-Q/(N·c out ·L e ) j ω Spool Velocity Analysis Inlet Turbine: Outlet Turbine: Friction (Petroff’s Law): Design Consideration: Minimize bearing area while maximizing momentum capture

ERC C&E Fluid Power 12 Throttling Loss Analysis Conclusions Majority of losses occur during valve transition Relief valve contributes significantly to losses  Replace relief valve with check valve parallel to load branch 4 Transition Events per Cycle: 1.Closing to Tank 2.Opening to Load 3.Closing to Load 4.Opening to Tank

ERC C&E Fluid Power 13 Throttling Loss Analysis Fully open throttling loss Full Open Transition

ERC C&E Fluid Power 14 Fluid Compressibility β(P): Yu Model Definition of Bulk Modulus:

ERC C&E Fluid Power 15 Linear Actuation Actuation and Sensing Linear position actuated hydraulically Sensing achieved using non-contact optical method

ERC C&E Fluid Power 16 System Simulation Simulation Results Predict 28Hz spool/84Hz PWM frequency Transition time from full on to full off in 3.2ms Step change in pressure from 200psi-800psi achieved in.19sec Average Pressure Ripple = 6.7%

ERC C&E Fluid Power 17 System setup

ERC C&E Fluid Power 18 Experimental Results Motor Driven Spool Actuated with electric motor Achieve PWM frequency of 500Hz 1 st Generation Self-spinning Spool Achieve maximum 27Hz Spool /54Hz PWM frequency

ERC C&E Fluid Power 19 Current System Work Pload Ps Use a conventional (linear spool) valve to study the effect of on/off control in typical applications Experiment 1: Use a throttling valve to cancel the output ripple  Load sensing approach  Achieve precise position control  Use minimal throttling to eliminate the ripple Experiment 2: Simulate regenerative braking with an on/off valve  Use an accumulator to spin a flywheel  Slow the flywheel by pumping to high pressure  Demonstrate an on/off pump motor

ERC C&E Fluid Power 20 Future Work Test and Improve Rotary Self-Spinning valve Investigate efficiency of a high speed system Develop control algorithms for PWM hydraulic systems Apply switching strategy to other applications (variable motor, regeneration, etc.) Perform CFD analysis to determine interaction between spool and sleeve, and to improve turbine design