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

Generic Presentation Template for CCEFP

Update this text in the Slide Master

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 - Torque

𝜙 = 2𝑜

250rpm1000psi

𝜙 = 165𝑜

250rpm1000psi

Model Validation – Flow Rate

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.

Experiment Efficiency Result

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, Mengtang.li@Vanderbilt.edu

• Ryan Foss, fossx231@umn.edu

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