project 16st1: ac hydraulic pump/motorac hydraulic pump use concept of interfering waves to create...
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Georgia Institute of Technology | Marquette University | Milwaukee School of Engineering | North Carolina A&T State University | Purdue University | University of California, Merced | University of Illinois, Urbana-Champaign | University of
Minnesota | Vanderbilt University
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Mengtang Li, Graduate Student, Vanderbilt UniversityRyan Foss, Graduate Student, University of Minnesota
Prof. Eric Barth, Prof. James Van de Ven, Prof. Kim Stelson
Project 16ST1: AC Hydraulic Pump/Motor
AC Hydraulic Pump
Use concept of interfering waves to create variable displacement pump.
2 pistons in mutual chamberwith one of the pistons being adjustable in real-time.
Piston 1
Piston 2 (phase adjusting)
Combined Waveform
Daniel A. Russell, PSU
Different Net Displacements Using Interfering Waves (0 to 180 deg)
Piston Stroke
𝑓 =1 + cos𝜑
2
Fractional Displacement:
AC Hydraulic Pump
Phase Shift = 𝟎°, Fractional Displacement = 1
Displacements from each piston is added (doubled).
AC Hydraulic Pump
Phase Shift = 𝟏𝟖𝟎°, Fractional Displacement = 0
Fluid is shuttled back and fourth (cancelled).
AC Hydraulic Pump
Phase Shift = 𝟗𝟎°, Fractional Displacement = 70.83%
The combined displacement is continuously variable.
AC Hydraulic Pump Benefits
• Mount Multiple Pumps on Common Shaft
– Axially Short
– Through Shaft
Source: http://http://www.boschrexroth.com/
Research Plan
Tasks:
1. Develop dynamic pump model
– Focus on AC hydraulics dynamics
2. Parameter study
3. Design prototype pump
– Utilize off-the-shelf components
4. Fabricate pump and characterize
– Efficiency map
5. Design for motoring
6. Demonstrate displacement control
– Single actuator
Time (months)
6 months
3 months
4 months
4 months
6 months
3 months
Dynamic Model of AC Pump
• Model captures• Compressibility
• function of entrained air and pressure• Viscous effects• Check valves dynamics• Slider-crank kinematics• Input motor dynamics
• Modeled Created in Simulink
Prototype I of AC Pump
Sprocket-chain
CAT 3CP1120
Pipes connecting cylinder chambers
Torque Sens.
Input, Output, and Cylinder Pressure Sens.
Output Flow Sens.
• 2 CAT 3CP1120 Pumps.• Drill holes and connect corresponding
cylinder chamber.• Connect crankshafts via sprocket and
chain transmission.
Prototype I of AC Pump
AC Hydraulic Pump Prototype
• Goals of First Prototype:
– Prove concept of wave interference for displacement control.
– Validate mathematical model for design purposes.
– Compare performance of pump against other variable displacement pumps.
– Do parameter optimization.
Experiment for AC Pump
• Goal is to calculate efficiency by measuring torque, flow, and pressure.
• Ran tests for every possible phase angle (dictated by teeth of sprocket):
phase = [2,21,45,69,93,117,141,165]
• 4 different speeds:
rpm = [250,500,750,1000]
Model Validation - Pressure
𝜙 = 2𝑜, 250 rpmPressure in cylinder vs Time
𝜙 = 2𝑜, 250 rpmPV Curve of cylinder
𝜙 = 165𝑜, 250 rpmPressure in cylinder vs Time
𝜙 = 165𝑜, 250 rpmPV Curve of cylinder
Model Validation - Pressure
Model Validation – Energy
*A constant 25 lbin torque is added to compensate the sprocket/chain torque.
Experiment Efficiency Result
• Efficiency curves role off due to constant friction (mechanical) and compressibility (volumetric). Fluid still compresses because pressure is maintained at high phase angles/low displacements.
Conclusion
1. Simulation model is built and is been validating now.
2. Prototype 1 is built and is been testing.
3. Baseline experiments are done for efficiency comparison.
4. Next step is to explore the parameter space and to optimize the design.
• Mengtang Li, [email protected]
• Ryan Foss, [email protected]
Calculating Efficiency• Total Efficiency:
𝜂𝑡𝑜𝑡 = 𝜂𝑇𝜂𝑉
• Volumetric Efficiency (compressibility, leakage):
𝜂𝑉 =2𝜋𝑄𝐷𝐷𝜔
𝑄𝐷 = Discharge/output flow, m^3/s𝐷 = Pump displacement per rev, m^3/rev𝜔 = Pump rotation speed, rad/sec
• Mechanical Efficiency (friction in fluid, joints, and seals):
𝜂𝑇 =𝐷Δ𝑃
2𝜋𝑇
Δ𝑃 = Difference between outlet and inlet pres, Pa𝐷 = Pump displacement per rev, m^3/rev𝑇 = Input torque, Nm
• Effective Displacement, 𝐷 :
𝑉1 =−𝑠𝐴
2cos 𝜃 +
𝑠𝐴
2
𝑉2 =−𝑠𝐴
2cos 𝜃 − 𝜑 +
𝑠𝐴
2
𝐷 = 𝑉1 + 𝑉2 =2𝑠𝐴
21 + cos(𝜑)
Note: pump’s for this test are crank-sliders that do not have perfect sinusoid motion, but pretty close.
𝜑