2-Stroke Low Speed Engine Cylinder Oil Stress and Shell ... · Title: PRESENTATION TITLE: FUTURA...

Copyright of Shell Global Solutions (Deutschland) GmbH

1 January 2012

2-Stroke Low Speed Engine Cylinder Oil Stress and Shell Alexia S4 development

CIMAC NMA Meeting

25th January 2012

Oslo, Norway

Luis García, Shell Global Solutions (Deutschland) GmbH


2 January 2012

The Oil Stress Concept

Shell developed the concept in 4-Stroke Medium Speed Engines (CIMAC Congress - 1998 & 2001)

An oil degrades in service as a result of its exposure to power.

Cumulative degrading processes of oil charge over service time (oil mean residence time).

Related to amount of power (and the way it is generated).

Oil Stress Factor (OSF)

Relation between:

Oil Consumption Rate, R [g/kWh]

Oil per kW of Power generated or Specific Sump Size, V [kg/kW]

Time of the oil in service, t [h]


3 January 2012

The Oil Stress Concept Oil Stress Factor vs. Specific Oil Consumption

Oil Stress Factor vs. Oil Consumption in a 4-Stroke Medium Speed Diesel Engine

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

16,00

18,00

0,00 0,20 0,40 0,60 0,80 1,00

OS

F [

kW

h/g

]

Oil Consumption R [g/kWh]

OSF kWh/g

Normal

Operation

Low Oil Consumption Shorter ODI

High Oil Consumption Longer ODI


4 January 2012

Factors Influencing Oil Stress – CIMAC Paper, June 2010


5 January 2012

Oil Stress in the 2-Stroke Low Speed Engine

Mini-sump -> thin oil film

Oil Film Thickness

Piston Rings Design

Loading and Speed

Liner Surface

Lubricant Viscosity

(Mean) Residence Time

Feed Rate (Effective Lube Refreshment Rate) -> g/kWh

Oil Film Thickness

Lubricant injection/distribution system (lube mass flow)

Evaporation or burned oil losses

Oil Film viewed as a “Mini Sump” for OSF calculations

Oil film thickness 1-8 µm Human hair


6 January 2012


Copyright © Wärtsilä Corporation Copyright © Wärtsilä Corporation


7 January 2012


Acid Stress

Thermal Stress

Insolubles Stress

Humidity Stress

Oil Stress

R

D

B

G

“RS”


8 January 2012

Oil Stress & Cylinder Lubricant Properties

Effect of fuel sulphur and air humidity on BN depletion

50%

60%

70%

80%

90%

100%

110%

0 5 10 15 20 25 30 35

BN

De

ple

tio

n [

%]

Absolute Scavenging Intake Air Humidity (g/m3)Dry Air Humid Air

1,7 % Sulphur

2,2 % Sulphur

2,7 % Sulphur


9 January 2012

Oil Stress & Cylinder Lubricant Properties Comparing samples

Higher OSF‟s lead to lubricant limits of desirable dispersancy performance.

Residual Total Base Number is not the only property describing oil performance. Lower quality spots correspond to those samples with higher residual TBN„s.

Heated Blotter Spots of “Ring Spray” oil samples from different configurations and ambient conditions

Humid Conditions OSF= 2,54 kWh/g

Cylinder A Dry Conditions OSF= 2,42 kWh/g

Cylinder B Dry Conditions OSF= 2,18 kWh/g

Humid Conditions OSF= 2,28 kWh/g


10 January 2012

How Oil Stress – defines lubricant performance

Influence on performance + Low ++ Medium +++ High

Oil Stress Factor

Thermal Stress ++ + +++ +++

Insolubles Stress +++ ++ ++

Acid Stress +++ +

Humidity Stress ++ ++ + ++

Influence of Oil Stress Factor on Lubricant

Neutralisation

Capability

Cleanliness

Performance

Abrasive Wear

ProtectionThermostability

Viscosity

Control


11 January 2012

Oil Performance Factors

Neutralisation Capability +++ ++ +Cleanliness (Detergency & Dispersancy) + +++ +++

Abrasive Wear Protection +++ +Thermostability ++ +++ +++Viscosity Control + ++ +++

Liner and

Piston Ring

Wear

Ring Land

and

Groove

Deposits

Engine

Cleanliness

Engine Performance Factors

How Oil Stress – defines lubrication performance

Relevance + Low ++ Medium +++ High


12 January 2012

0%

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100%

0 20 40 60 80 100 120 140

Engi

ne L

oad

Residence Time in the Lubricating Film [seconds]

0,95 g/kWh

longer

Slow steaming

12

Factors Influencing Oil Stress Slow steaming conditions


13 January 2012

Summary Conclusions

Cylinder Oil “Ring spray” sampling combined with the quantification of ring spray oil loss increased understanding of the lubrication complexity in a 2-stroke engine.

Low engine load operation (Slow & “Flexible” Steaming) represent real challenges to existing cylinder lubricants

Understanding lubricant exposure is critical to designing new cylinder lubricants capable to withstand higher levels of Oil Stress – future cylinder lubricants must have a wider range of operational flexibility

2-Stroke Low Speed Engine Cylinder Oil Stress and Shell ... · Title: PRESENTATION TITLE: FUTURA...

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