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Mechanical behavior of tribofilms formed from MoDTC and ZDDP additives in ethanol engines

Grant number: 17/19147-2
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): March 01, 2018
Effective date (End): January 31, 2020
Field of knowledge:Engineering - Mechanical Engineering
Principal Investigator:Roberto Martins de Souza
Grantee:Roberto Balarini Junior
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated scholarship(s):18/25962-3 - Mechanical behavior of tribofilms formed from MoDTC and ZDDP additives in ethanol engines, BE.EP.DR

Abstract

The expansion of the use of ethanol as fuel has generated many investigations regarding its impact on the performance of Internal Combustion Engines (ICM). In general, due to high latent heat of evaporation of ethanol, lubricant contamination can be significant and often damaging to lubrication efficiency of ICM parts (for example, the ring-liner system). More specifically, this lubricating oil contamination can influence the kinetics of tribochemical reactions, which may affect the steps of formation of the tribofilms that would normally be generated from oil additives activation. In addition, the presence of ethanol in lubricant tends to reduce tribofilm thickness to values that decrease tribofilm effectiveness. For example, in the case of "friction modifier" and "anti-wear" additives, this effectiveness loss may be responsible for excessive fuel consumption, higher environmental pollution generation and premature failures. Therefore, there is a need for studies focused on characterization of tribofilms formed under daily operating conditions - also considering lubricant contamination by ethanol. At this point, it is important to point out that literature is limited in terms of tribofilm analysis in ethanol engines and, nowadays, there are no studies about tribofilms mechanical properties measurement in these engines. Therefore, the present PhD project is related to investigate tribofilms mechanical properties in ethanol engines. The additives to be investigated are MoDTC (classified as "friction modifier") and ZDDP ("anti-wear" type). The methodology involves a set of tribological tests conducted on SRV4 tribometer, with ring-liner system configuration, whose function is to evaluate engine operating conditions with different fully formulated lubricating oils, varying the proportion of additives (MoDTC and ZDDP), under new and aged conditions (without and with contamination, respectively). The oil contamination will be made by diluting anhydrous ethanol (AE) in oil by an artificial method developed in laboratory. Once the friction tests are conducted, this work predicts the use of nanoindentation technique (including tests at high temperature) to mechanically characterize the tribofilms generated and to correlate with engine tribological performance. Moreover, wear rates, surface topography and microscopy analysis (optical and scanning electron) will be also conducted in order to improve results correlations. In general, the idea is to investigate how detrimental is ethanol dilution to engines that operate with ethanol or with any mix fraction of ethanol and gasoline (usually known as flex engines). In this context, there is still the possibility of comparing the properties of tribofilms in ethanol engines (this work) with engines that run exclusively on gasoline (literature). Finally, in order to increase efficiency (reduction of friction), optimize life (minimize wear rate) and reduce pollutants emission (less fuel consumption), it is expected that this work will contribute on technological advances in relation to the technologies of ICM lubricant additives. (AU)