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New findings about friction in combustion engines and new test
device for measurement of piston
ring – cylinder liner friction
Markus Söderfjäll Supervisors:
Roland Larsson Andreas Almqvist
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Power cylinder unit
2
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Components in the PCU
• Piston assembly – Piston – Piston rings
• Compression ring • Scraper ring • Oil control ring
• Cylinder liner
3
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Losses in the PCU
Distribution of mechanical friction
Distribution of piston ring and connecting rod friction
Distribution of piston ring assembly friction
PCU is responsible for 1.1-6.8% of the total losses in a heavy
duty diesel engine
Distribution of total energy
Richardson, 2000, Review of power cylinder friction for diesel
engines 4
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Possible ways of reducing friction
Reduced ring tension – Rings will conform less to liner
• Increased oil consumption • Increased blow by
– Combined with reduced out of roundness
𝐹𝑓 = µ ∙ 𝐹𝑛
2nd 3rd 4th
Δr
5
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Simulation model
• FEM • Twin land oil control ring
– Not allowed to rotate
• Reynolds equation – Fully flooded inlet
• Luleå Mixed Lubrication Model (LMLM) – Contact model – Flow
factors
• 3D structural mechanics model
6
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Simulation model
Ph= Hydrodynamic pressure
Pc= Contact pressure
Fh = Hydrodynamic friction
Fc = Contact friction
Rt = Ring tension
Pa = Contact pressure from piston groove
Pah = Axial damping
Ph+Pc
Rt
Ph+Pc
Fh + Fc
Pa+Pah
U
Fh + Fc
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Simulation parameters
• Parabolic ring profile • Measured cylinder liner surface •
Stationary cases at mid-stroke • Out of round cylinder liners •
Varied parameters:
– Tangential load – Scaled out of roundness
AVL Glide User’s Manual 2000
Order of OOR 2 3 4 5 6 8 Max amplitude [µm] 32.5 20.8 15.6 7.8
5.2 3.9
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Results
25 30 35 40 45 50 55 606
6.5
7
7.5
8
8.5
9
9.5
10
10.5
Tangential load (N)
Fric
tion
forc
e (N
)
100%77%55%33%11%0%
25 30 35 40 45 50 55 601.5
2
2.5
3
3.5
4
4.5 x 10-6
Tangential load (N)
Aver
age
min
imum
sep
arat
ion
(m)
100%77%55%33%11%0%
9
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Test rig specification
• Validation of simulation model • Component test rig • Higher
speeds than earlier rigs • Variable parameters
– Speed – Temperature – Out of roundness
• Measure friction
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Test rig
• Low vibration – First two orders cancels
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Test rig
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Test rig
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Tack till
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Contact
Markus Söderfjäll
Avdelningen för maskinelement
Luleå tekniska universitet
[email protected]
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Results
Scaling 100% 80% 60% 40% 20% 0% Required tangential force (N) 56
47.7 40.7 35.3 32 31
Total friction force (N) 16.4 13.9 11.9 10.4 9.4 9.2 Friction
reduction (%) - 15 27 37 43 44
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Results
Min separation for lower land on TLOCR against OOR bore
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Ring land twist against out of round bore
Upper land Lower land
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Internal twist between ring lands
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Test rig
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Test rig
New findings about friction in combustion engines and new test
device for measurement of piston ring – cylinder liner
frictionPower cylinder unitComponents in the PCULosses in the
PCUPossible ways of reducing frictionSimulation modelSimulation
modelSimulation parametersResultsTest rig specificationTest rigTest
rigSlide Number 13Test rigTack tillContactResultsResultsRing land
twist against out of round boreInternal twist between ring
landsSlide Number 21Test rig
