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Oljetemperaturens inverkan på motoroljans degradering i lastbil
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2007 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
The oil temperature’s effects on engine oil degradation in trucks (English)
Abstract [en]

The market for heavy duty engines is constantly requiring engines that should be more and

more powerful, while still maintaining low fuel consumption. As a result of increasing engine

power, the engine and coolant temperature increases as well due to insufficient cooling

performance (because of design issues, cost etc.).

Also, emission legislations, both current and future, require more and more measures to be

taken by engine manufacturers. One way of meeting the legislations is the use of cooled EGR

(Exhaust Gas Recirculation), which also lead to increased coolant temperatures.

Both these factors also naturally lead to increased engine oil temperatures, the consequences

of which are not thoroughly investigated.

This thesis project aims to investigate effects of high temperatures on engine oil degradation,

with focus on the greatest degradation process: oxidation. To do this several engine runs have

been performed on a 310 hp engine with EGR to see what happens to the engine oil in a real

engine when exposed to high temperatures. During the tests oil samples have been taken and

analysed for important parameters.

As a complement to these engine tests some laboratory oxidation testing have also been

performed, to be able to compare engine test data with laboratory tests.

One goal of the project was to try to formulate an empirical oxidation model, which would be

able to predict oil oxidation levels in an engine, given any running parameters. This model

was to be based on the results of the engine tests and oil analysis. This goal was not achieved

though, as it showed that the engine tests were too short to show any good tendencies in oil

oxidation. It was therefore decided that further and longer engine tests were to be made, but

these did not fit into the timeframe of this project. However, an embryo of an oxidation model

has been presented, and suggestions for further development have been made.

Another goal was to clarify where and to what extent the engine oil is exposed to high

temperatures in an engine, and to discuss what can be done to improve the situation. Whether

or not a dedicated oil temperature gauge in production engines is needed, and where that

would be mounted, is discussed. This has been done based on the results of the engine and

laboratory testing. One interesting finding is that increasing the flow to the piston cooling

system does not seem to improve anything for the oil; instead the oil consumption as well as

oil oxidation seems to be able to increase. Another conclusion is that using a sump oil

temperature gauge as a standard part of the new engine generation might be a good idea, since

it has been shown that high engine oil temperatures in the sump have great negative effects on

engine oil oxidation, and that the oil temperature in the sump is behaving quite irregularly in

relation to other oil temperatures.

To support the work in this project a thorough literature survey was undertaken including

various SAE and other technical papers, books and Scania reports. Based on these facts the

procedures behind engine oil oxidation on a chemical level have been investigated, among

other things.

For confidentiality reasons this report has been edited in such a way that absolute values of

measured parameters have been removed. Where possible, these values have been replaced by

percentages of normal values.

Abstract [sv]

Marknaden för tunga motorer kräver ständigt motorer som är starkare och starkare, men som

ändå behåller en låg bränsleförbrukning. Ett resultat av att göra motorer starkare är att motoroch

kylvattentemperaturer ökar, på grund av otillräcklig kylning (på grund av

konstruktionsmässiga skäl, kostnader och dylikt).

Dessutom kräver nuvarande och framtida emmissionslagstiftning att fler och fler åtgärder

vidtas av motortillverkare världen över. Ett sätt att tillmötesgå lagkraven är användandet av

kyld EGR (Exhaust Gas Recirculation), vilket också leder till ökade kylvattentemperaturer.

Båda dessa faktorer leder också till ökade motoroljetemperaturer, med följder som ej är

grundligt utredda.

Detta examensarbete syftar till att utreda följderna av höga temperaturer på

motoroljedegradering, med inriktning mot den grövsta degraderingsprocessen: oxidation. För

att göra detta har ett antal motortest utförts på en 310 hk motor med EGR för att se vad som

händer med motoroljan när den utsätts för höga temperaturer. Under dessa tester har

oljeprover tagits för analys av viktiga oxidationsparametrar.

Som ett komplement till dessa motorprover har även oxidationstester utförts i

oljelaboratorium, för att kunna jämföra motortestdata med laboratorietestdata.

Ett mål med detta projekt har varit att försöka formulera en empirisk oxidationsmodell, som

skulle kunna förutsäga oljeoxidationsnivåer i en motor, givet godtyckliga driftsparametrar.

Denna modell skulle baseras på resultaten från motor- och labbtesterna. Detta mål uppnåddes

inte dock, då det visade sig att motorproverna var för korta för att visa några tydliga tendenser

i oljeoxidation. Det beslutades därför att ytterliggare och längre motorprov skulle köras, men

dessa rymdes tyvärr inte inom tidsramen för detta examensarbete. Ett embryo till en

oxidationsmodell har ändå föreslagits, och förslag för vidareutveckling av denna har

presenterats.

Ett annat mål med projektet var att klargöra var och i vilken utsträckning motoroljan utsätts

för höga temperaturer i en motor, samt att diskutera vad som kan göras för att förbättra

situationen. Huruvida en dedikerad temperaturgivare för motoroljetemperatur går att motivera

i produktionsmotorer, och vart denna i så fall skulle sitta, diskuteras. Detta har gjorts med

grund i resultaten från motor- och labbproverna. En intressant slutsats är att ökat flöde till

Place, publisher, year, edition, pages
2007.
Series
MMK 2007:48 MFM110
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-100848OAI: oai:DiVA.org:kth-100848DiVA: diva2:545351
External cooperation
Scania CV AB,Magnus Grafström
Uppsok
Technology
Supervisors
Examiners
Available from: 2012-08-20 Created: 2012-08-20 Last updated: 2012-08-20Bibliographically approved

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