Surface Effects on Engine Materials of Mineral Oil Dilution With Methyl Esters and Biodiesels

Surface Effects on Engine Materials of Mineral Oil Dilution With Methyl Esters and Biodiesels

Gustavo J. Molina, Emeka F. Onyejizu, John L. Morrison, Valentin Soloiu
Copyright: © 2020 |Pages: 18
DOI: 10.4018/IJSEIMS.2020070101
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Abstract

During ordinary internal-combustion engine operation, biodiesels partially mix in the engine-oil, leading to increased surface degradation, as premature wear. Biodiesels are blends of methyl esters as main components, which are dependent on the source feedstock and may lead to different surface effects on engine materials. In this preliminary study of surface change of SAE 1018 steel when adding pure methyl-esters to engine oil, a SAE 15W40 mineral oil was diluted with methyl-palmitate, -oleate, -stearate, -linoleate, -laurate and -myristate, and with two typical biodiesels, soybean oil and peanut oil biodiesel, each at six different dilutions, and tested in two different instruments. Biodiesel at just 5% in oil led to enhanced wear, but some larger fractions of methyl-oleate and -laurate produced negligible surface change enhancements. Addition of methyl-linoleate and -palmitate enhanced surface degradation. Methyl ester compositions of the two tested biodiesels and their wear trends, which are found in good agreement with previous studies, are used to explain the wear differences
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Background

First published studies on the surface effects of oil diluted with biodiesel were presented by Fang et al. (2007) using a high frequency reciprocating rig (HFRR) tribometer, with contact surfaces of ANSI E-52100 steel, with HRC 58-66 hardness for upper ball, and 30 Vickers hardness for flat specimen. They found that biodiesel dilution of engine oil may increase wear even for a low 5% dilution rate; they hypothesized that such loss of lubricity could be enhanced by the action of aged partially oxidized biodiesels and by their likely interactions with the typical oil anti-wear ZDDP additives. Jech et al. (2008) investigated the effects of dilution by biodiesel in a nanoscale-wear-volume coherence tribometer. They found that biodiesel dilutions of up to 10% in diesel oil would lead to negligible wear increases, but dilutions of 30% and higher would induce significantly enhanced wear.

Early work by the authors (Shanta, 2011) showed that important wear effects result from oil-lubricant dilution with biodiesels. In their work, biodiesels from four types of feedstock (canola oil, peanut oil, soybean oil, and chicken fat oil) were mixed in a typical diesel oil (SAE 15W40) and tested in a T-11 pin on disk tribometer. The tested material pair was an AISI 316 stainless-steel ball on an AISI 1018 steel disk specimen; friction force was recorded during tests, and wear and Ra roughness changes were obtained from pre- and post-test measurements. They tested oil-dilution by 5%, 10%, 20%, and 30% of each biodiesel as compared to the same dilution percentages by a mineral diesel fuel. Shanta et al. results, which are presented in Figure 1, strongly suggested that increasing degrees of oil dilution by the tested biodiesels led to enhanced wear, as compared to those from the same dilutions when using a diluting mineral diesel. But they also observed significant differences when compared wear from different biodiesels for same dilution percentages.

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