The Significance of Piston/Cylinder Surface
Shaping on the Performance of Axial Piston
Machines
Ashley Wondergem
Dr. Monika Ivantysynova
Purdue University
October 16, 2015
Slide 2 Ashley Wondergem
Outline
• Introduction
• Axial Piston Machines
• Theory
• Previous Research
• Method
• Fluid Structure Interaction Model
• Simulation Study First Phase
• Simulation Study Second Phase
• Simulation Study Results
• Conclusion
• Next Steps
Slide 3 Ashley Wondergem
Introduction
Piston & Cylinder
Cylinder Block & Valve PlateSlipper & Swash Plate
Overview of Main Tribological Interfaces of Axial Piston Machines
ODC (Outer
Dead Center)
IDC (Inner
Dead Center)
Bearing Function Load Carrying
Sealing Function
Functions
Viscous Friction Leakage flows
DissipationsMain source of
energy
dissipation
Goal:Investigate how to reduce energy dissipation
between the piston and the cylinder through
surface shaping of the piston
Slide 4 Ashley Wondergem
Previous Work – Surface
Shaping
• Yamaguchi (1976)
• Numerical analysis: tapered piston increased efficiency
• Ivantysynova (1983)
• Proposed a barrel like piston
• Kleist (1997)
• Surface shaping reduces friction forces
• Lasaar (2003)
• Barrel piston (analytical and experimental)
• Volumetric losses reduced
• Friction forces reduced
Loss reductions strongly dependent on
operating condition
Study made with incomplete models
Slide 5 Ashley Wondergem
Fluid Structure Interaction Model
Pressure Deformations
Kinematics / Dynamics
Lubricating Fluid Film
Macro & Micro Motion
Heat Transfer
Thermal Deformations
Pressure Field
Surface Profile
Slide 6 Ashley Wondergem
Micro Surface Shaping-Geometries Under Investigation
Sine
MRCA
λ
Flat
MRCA
Barrel
MRC
R1
R2
R3LApex
Waved Barrel
R1
R2R3
LApex
MRC
A λ
•𝐴 [µ𝑚]
𝑅𝐾 [𝑚𝑚]=0.29‰
•λ [𝑚𝑚]
𝐿𝑝𝑖𝑠𝑡𝑜𝑛 𝑙𝑒𝑛𝑔𝑡ℎ [𝑚𝑚]= 0.4
• MRC = 0.96‰
•𝑅1[𝑚𝑚]
𝑅2[𝑚𝑚]= 0.9996
•𝑅3[𝑚𝑚]
𝑅2[𝑚𝑚]= 0.9984
•𝐿𝐴𝑝𝑒𝑥[𝑚𝑚]
𝐿𝑝𝑖𝑠𝑡𝑜𝑛 𝑙𝑒𝑛𝑔𝑡ℎ[𝑚𝑚]=0.4167
• MRC = 0.96‰
•𝐴 [µ𝑚]
𝑅𝐾 [𝑚𝑚]=0.29‰
• MRC = 0.96‰
MRC
CircSine
•𝐴 [µ𝑚]
𝑅𝐾 [𝑚𝑚]=0.29‰
•λ [𝑚𝑚]𝐶𝐾 [𝑚𝑚]
= 0.167
• MRC = 0.96‰
•𝐴 [µ𝑚]
𝑅𝐾 [𝑚𝑚]=0.29‰
•λ [𝑚𝑚]
𝐿𝑝𝑖𝑠𝑡𝑜𝑛 𝑙𝑒𝑛𝑔𝑡ℎ [𝑚𝑚]= 0.4
•𝑅1[𝑚𝑚]
𝑅2[𝑚𝑚]= 0.9993
𝑅3[𝑚𝑚]
𝑅2[𝑚𝑚]= 0.9989
•𝐿𝐴𝑝𝑒𝑥[𝑚𝑚]
𝐿𝑝𝑖𝑠𝑡𝑜𝑛 𝑙𝑒𝑛𝑔𝑡ℎ[𝑚𝑚]=0.4167
• MRC = 0.96‰
Baseline:
Standard wear-in piston-cylinder from
75 cc stock unit:
• Bushing wear: max 𝑤𝑒𝑎𝑟 [µ𝑚]
𝑅𝑍 [𝑚𝑚]=1.21
• Piston wear: max 𝑤𝑒𝑎𝑟 [µ𝑚]
𝑅𝐾 [𝑚𝑚]=0.1
• MRC = 1.64‰
MRC
max wear
max wear
Slide 7 Ashley Wondergem
Simulation Studies
First phase:4 different designs compared to baseline for moderate
operating conditions in pumping mode only
Results published in:
Wondergem, A, and M Ivantysynova. 2014. "The Impact of the
Surface Shape of the Piston on Power Losses." Proceedings of the
8th FPNI PhD Symposium. Lappeenranta, Finland.
Second phase:5 different designs compared to baseline for extreme operating
conditions in pumping and motoring mode
Slide 8 Ashley Wondergem
Simulation StudyPumping Mode - 1000 rpm, 400 bar
Baseline FlatBarrel
4
6
3
1
0
Fluid Film
Gap Height
(μm)7
1000
500
0
Pressure
(bar)2000
1500
HPLP
360
Lf
0.1
0.5
1
00.1
0.5
1
360
Lf
0
0.1
0.5
1
360
Lf
0
360
Lf
0
360
Lf
0
360
Lf
0
Slide 9 Ashley Wondergem
SineBarrel
Simulation StudyPumping Mode - 2800 rpm, 400 bar
4
6
3
1
0
Fluid Film
Gap Height
(μm)7
Baseline
HPLP
0.1
0.5
1
360
Lf
00.1
0.5
1
360
Lf
0
1000
500
0
Pressure
(bar)2000
1500
360
Lf
0360
Lf
0
360
Lf
0
DC
Case
0.1
0.5
1Lf
0 360
Slide 10 Ashley Wondergem
Simulation StudyPumping Mode – Energy Dissipation
Up to 40%
reduction (flat)Flat fails at high
speeds/pressures
Circ sine and waved barrel
outperform at LP
Barrel best,
especially at HP
Up to 30% decrease
for barrelSine also fails at high
speeds/pressures
Slide 11 Ashley Wondergem
Simulation StudyPumping Mode – Leakages
Up to 70% reduction
(flat); Based on 40%
reduction in clearance
BUT fails at some
operating conditions
Around 60%
reduction (barrel)
Around 40% reduction at
higher speed/pressures
Slide 12 Ashley Wondergem
Simulation StudyPumping Mode – Overall
ϕ𝐷:𝑏𝑎𝑠𝑒 − ϕ𝐷:𝑠ℎ𝑎𝑝𝑒 ϕ𝐷:𝑏𝑎𝑠𝑒
𝑥100** Simulation failure was
penalized 1.5*baseline
Slide 13 Ashley Wondergem
Simulation StudyMotoring Mode - 2000 rpm, 225 bar
Barrel
4
6
3
1
0
Fluid Film
Gap Height
(μm)7
Baseline
HPLP
DC
Case
1000
500
0
Pressure
(bar)2000
1500
360
Lf
0
360
Lf
0
360
Lf
0
0.1
0.5
1
360
Lf
0
0.1
0.5
1
360
Lf
00.1
0.5
1
360
Lf
0
Waved
Barrel
Slide 14 Ashley Wondergem
Simulation StudyMotoring Mode – Energy Dissipation
Waved barrel and circ sine
almost 30% decrease
Waved barrel and circ sine
outperforms barrel in
motoring mode
Slide 15 Ashley Wondergem
Simulation StudyMotoring Mode – Leakages
Flat and circ sine results in
almost 50% decrease
Waved barrel and circ sine
results in larger decrease
than barrel
Trend in energy dissipation relies
on reduction in leakages
-Based on reduction in
clearance
Slide 16 Ashley Wondergem
Simulation StudyMotoring Mode – Overall
ϕ𝐷:𝑏𝑎𝑠𝑒 − ϕ𝐷:𝑠ℎ𝑎𝑝𝑒 ϕ𝐷:𝑏𝑎𝑠𝑒
𝑥100** Simulation failure was
penalized 1.5*baseline
Slide 17 Ashley Wondergem
Simulation StudyOverall Pumping & Motoring Mode
ϕ𝐷:𝑏𝑎𝑠𝑒 − ϕ𝐷:𝑠ℎ𝑎𝑝𝑒 ϕ𝐷:𝑏𝑎𝑠𝑒
𝑥100** Simulation failure was
penalized 1.5*baseline
Slide 18 Ashley Wondergem
Conclusion
Piston Surface Shaping
– Better understanding of how piston shape effects machine operation
and fluid film generation under various conditions
– Increased load support allows for reduction in clearance between the
piston and the cylinder
• Improve/maintain reliability of machine
– Improvements in the efficiency of the machine are shown over a wide
range of operating conditions
• Largely due to decreased leakages based on decreased clearances
– Overall barrel surface profile performs best under conditions studied
Slide 19 Ashley Wondergem
Next Steps• Investigate at machine limits
• Manufacture prototype
• Test on Steady State test rig
• Measure overall losses
• Test on the Tribo test rig
• Measures the friction forces at the piston/cylinder interface
• Test on the EHD test rig
• Measure the pressure and temperature distribution as the swashplate rotates
EHD Test Rig
Case
Cylinder Block
Shaft
Swashplate
Main Pistons
Tribo Test Rig
Slide 20 Ashley Wondergem
Questions
Monika Ivantysynova - [email protected]
Ashley Wondergem – [email protected]
Contact Information