Filtern
Dokumenttyp
- Zeitschriftenartikel (6)
- Beitrag zu einem Tagungsband (3)
- Buchkapitel (1)
- Forschungsbericht (1)
Sprache
- Englisch (8)
- Deutsch (2)
- Französisch (1)
Schlagworte
- Ester (11) (entfernen)
In order to reduce experimental effort, tribological tests are performed for coating selection, simulating the friction, wear and scuffing behaviour between the piston ring and cylinder liner, as well as lubricant evaluation. The creation of test standards in piston ring/cylinder liner simulation is discussed. PVD coatings, HVOF coatings and nitriding treatments have been applied to piston rings as alternative for chromium coatings. CrN/TiN coating seems very effective for increasing the wear and scuffing resistance. Biodegradable engine oils based on esters and polyglycols reduce friction and exceed the wear resistance of reference engine oils based on hydrocarbons for the new generation engines with high cylinder pressures.
The dilution of biogenic fuels into lubricating engine oils often leads to a shortening of the recommended oil drains (between 30% and 60%) and an increase in wear. The large number of overlapping and influencing factors, of which dilution and polymerization of fuel components in the engine oil are emphasised, makes it difficult to find a uniform solution to prevent failures in the various applications.
Insofar single solutions for the different types of biofuels are needed. The contribution of base oil chemistry and additives as well as triboactive materials is featured to deal with the adverse effects of biofuels. In the frame of the European Commission (EC)-funded project 'cleanengine', tentative engine oils based on esters with a content of renewables and polyglycols are formulated to increase the lubricant's tolerance in engines fuelled with biofuel-based blends, with the aim of ensuring required lubricating and wear protection performance while keeping oil drain intervals unchanged.
The present paper focuses on four-stroke diesel applications, fuelled by biodiesel (fatty acid methyl ester — FAME) as well as by rapeseed oil and Jatropha oil (pure vegetable oils, triglycerides), together with relevant blends of those biofuels and conventional diesel fuel.
This paper screens the functional profile (in particular rheological, toxicological, bio-compatibility, tribological and biofuels affinity) of lube families with respect to biofuel contamination. Moreover, this is followed by the contributions of piston ring and liner materials as well as thin film coatings.
Biolubrifiants
(2011)
Un point de départ pour la mise en route des lubrifiants « neutre à l'environnement » ont été les huiles perdues et les fuites accidentelles, les lubrifiants perdus rejoignant les sols et les eaux (voir lac de Constance).
Même en prenant en compte les voies du recyclage, la combustion dans les moteurs et les fuites connues, environ 30 % (entre 20 % et 40 %, selon les études) du volume de lubrifiants entre dans l'environnement par des voies non attribuables ou est probablement mis en décharge de manière illégale.
Avec de tels chiffres publics, les arguments des lobbyistes de l'industrie pétrochimique, affirmant que, dans la plupart des applications, les fluides sont enfermés dans des réservoirs clos et étanches, ne convainquent pas les politiques. C'est aussi peut-être parce que, en Allemagne, environ 60 % des particuliers changent leur huile eux-mêmes.
The research institution TEKNIKER has coordinated the EUROPEAN Project EREBIO, were different biodegradable lubricants have been formulated by FUCHS and BAM for heavy duty engines (GUASCOR), and passenger cars (RENAULT). In the frame of this article, it has been summarised the results obtained when developing biodegradable passenger car lubricants in combination with triboreactive materials.
Replacing hydrocarbon-based oils with biodegradable products is one of the ways to reduce adverse effects on the ecosystem caused by the use of lubricants. The application of low or no sulphur, ash and phosphorous (lowSAP) ester- or polyglycol-based oils, intended for passenger car engine lubricants as substitutes for hydrocarbon-based oils, required the preparation of a composition of lubricants with comparable tribological and functional properties.
The study is focussed on passenger car motor oils (PCMO) with reduced metal-organic additives. This is necessary in order to reduce the ash build-up in the after treatment system and therefore improve its efficiency and lifetime. High fuel efficiency and long drain intervals are requested, as well. To follow a line in a consequent way, these oils have to be biodegradable and non-toxic to the aqueous environment according to the directive EC/1999/45, coherent with other international standard. In a modern diesel or gasoline engine, the engine oils has to fulfil quite a number of different functions, such as lubricating and cooling the system, wear protection, soot and particle handling with less deposit tendency and so on.
In the paper a study of the biodegradability, toxicity and the tribological properties has been carried out for new developed prototype engine bio-oils. Also, some different plasma sprayed triboreactive coatings have been deposited on cast iron piston rings, being studied also their tribological properties. Finally, the behaviour of the new bio-oils selected and plasma sprayed triboreactive coatings on piston rings have been screened in a real engine.
The use of alternative base oils, like esters or polyglycols, with more intrinsic properties for the lubrication of automobile engines has a potential for ecological and technical advantages. Being in competition with hydrocarbon-based formulations, detailed knowledge of several thermophysical and viscometric properties as well as tribological properties over a large temperature range are required (mapping). The tested polymer-free polyglycols and ester-based formulations displayed no visible tribological weaknesses regarding wear resistance and EP-behavior as well as offering significant advantages in order to meet metal- and ash-free and bio-no-tox criteria. Especially the formulated polyglycols without friction modifiers also showed an intrinsic retention of low coefficients of friction and a hydrodynamic film forming behavior comparable to hydrocarbon-based factory-fill oils. The wear resistance and EP-behavior of low-additivated polyglycols, but also of esters, can be enhanced by means of triboactive materials. Lubricious oxides or triboactive materials and polar base oils, or a combination thereof, may substitute the EP and AW properties realized by the additives, thus enabling long drains and responding to eco-tox or bio-no-tox requirements as well as restrictions from the chemical box.