The data from the authors’ earlier investigations show that molecules of zinc dithiophosphate (ZDDP) added to a lubricant can absorb energy emitted by a solid surface, which is where triboreactions occur. If the lubricant contains structures able to conduct energy, the ZDDP reactions can occur even at a relatively large distance from the solid surface, which should increase the effectiveness of ZDDP as an antiwear additive. The purpose of this paper was to verify the thesis that the tribocatalytic effect depends on the ability of the solid surface to emit electrons/energy and the ability of ordered molecular structures, such as carbon nanotubes (CNTs), to conduct energy and, most likely, to enhance the energy transfer. The tribological tests were performed using a TRB3 tribotester for 100Cr6 steel balls and uncoated or a-C:H coated HS6-5-2C steel discs. Polyalphaolefin 8 (PAO8) and PAO8 mixed with ZDDP and CNTs were used as lubricants. The results of the tribological tests suggested that: (a) the effect of the interactions between ZDDP and CNTs was clearly visible; (b) the structure and properties of the solid surface layer had a significant influence on the antiwear action of the ZDDP additive.
This paper presents differences between fossil fuel (Jet A-1) and alcohol/Jet A-1 blend, during combustion process using laboratory test rig with miniature turbojet engine (MiniJETRig). The test rig has been created in Air Force Institute of Technology for research and development works aimed at alternative fuels for aviation. Fuel from different feedstock (non-fossil sources) is introduced into market due to ecological aspects, fuel price stability and energy security. Application of alcohol to propel aircraft has started form using a blend of aviation gasoline with ethanol in spark-ignited internal-combustion engines. Taking into account that large part of aviation fuels used by commercial aircraft is jet fuels, so in this area it has begun to look for possibilities to apply alcohol component. In 2016, international standard (ASTM) approved a synthetic blending component for aviation turbine fuels for use in civil aircraft and engines-alcohol-to-jet synthetic paraffinic kerosene (ATJ-SPK). According to standard, ATJ-SPK synthetic blending components shall be comprised hydro processed synthetic paraffinic kerosene wholly derived from isobutanol processed through dehydration, oligomerization, hydrogenation and fractionation. Two different fuel samples, a traditional fossil jet fuel (Jet A-1) and a blend of 10% butanol with Jet A-1 were tested. Laboratory tests of selected physicochemical properties and bench tests with the same profile of engine test were carry out for both fuel samples. The obtained results: engine parameters and exhaust gas emissions are compared and discussed.
Experimental studies reveal that the simultaneous addition of zinc dialkyl dithiophosphates (ZDDPs) and multi-wall carbon nanotubes (MWCNTs) to a poly-alpha-olefin base oil strongly reduces wear. In this paper, it is shown that MWCNTs promote the formation of an anti-wear (AW) layer on the metal surface that is much thicker than what ZDDPs can create as a sole additive. More importantly, the nanotubes’ action is indirect, i.e., MWCNTs neither mechanically nor structurally strengthen the AW film. A new mechanism for this effect is also proposed, which is supported by detailed tribometer results, friction track 3D-topography measurements, electron diffraction spectroscopy (EDS), and Raman spectroscopy. In this mechanism, MWCNTs mediate the transfer of both thermal and electric energy released on the metal surface in the friction process. As a result, this energy penetrates more deeply into the oil volume, thus extending the spatial range of tribochemical reactions involving ZDDPs.
If a lubricant contains structures capable of conducting energy, reactions involving zinc dialkyldithiophosphate (ZDDP) may take place both very close to and away from the solid surfaces, with this indicating that ZDDP can be a highly effective anti-wear (AW) additive. The central thesis of this article is that the tribocatalytic effect is observed only when the energy emitted by the solids is transmitted by ordered molecular structures present in the lubricant, e.g., graphene. The friction tests were carried out for 100Cr6 steel balls in a sliding contact with uncoated or W-DLC-coated HS6-5-2C steel discs in the presence of polyalphaolefin 8 (PAO 8) as the lubricant, which was enhanced with graphene and/or ZDDP. There is sufficient evidence of the interactions occurring between ZDDP and graphene and their effects on the tribological performance of the system. It was also found that the higher the concentration of zinc in the wear area, the lower the wear. This was probably due to the energy transfer resulting from the catalytic decomposition of ZDDP molecules. Graphene, playing the role of the catalyst, contributed to that energy transfer.
The paper covers the mechanism of lubrication layer formation by fuels containing synthetic hydrocarbons
and alcohols. Development of alternative fuels containing FAME, alcohols, and synthetic hydrocarbons has
increased the interest in the mechanism of lubrication of fuelling systems parts. Fuel lubricity tests have been
conducted using the HFRR and BOCLE testing rigs. Fuels under testing, both for CI engines and for aviation
turbine ones, contained synthetic components: saturated hydrocarbons both of even and odd number of carbon
atoms, and butanol, isomers. These components have been added to conventional fuels, such as diesel fuel and
Jet A-1 fuel at the concentration of 0–20% (V/V). All fuels under testing contained commercially available
lubricity improvers (carboxylic acid). Test results were analysed using model αi described in [L. 6, 7]. As
a result of the analysis, it has been found that the liquid phase, which is a lubricating film, should contain
agglomerates or molecular clusters responsible for the transport of energy introduced into lubricating film by
electrons emitted from metal surface. The mechanism enabling a description of the effect of base fuel without
lubricity improvers on efficiency of such additives has been suggested.
A worldwide trend to popularise gradually increasing use of biofuels in various applications was a motivation for gaining interest in FAME as a commonly available biocomponent to fuels combusted in turbine engines. These engines are mainly used in aeronautics, but many of them are also used in other, non-aeronautical areas, including marine navigation. Specific conditions in which fuels are combusted in turbine engines used in these applications are the reason why fuel mixtures of kerosene and FAME type should reveal relevant low temperature characteristics.
The article presents results of tests of low temperature properties of mixtures of the jet fuel Jet A-1 and methyl esters of higher fatty acids (FAME). The prepared mixtures contained different contents of FAME. The obtained results present changes of: viscosity, cloud point, pour point, crystallising point, and cold filter plugging point, dependingon the percentage by volume of FAME. They also prove that the course of changes of low temperature properties of these mixtures is affected by chemical structure of the biocomponent.
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