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Efficiency of tribological contacts and energy efficiency are two sides of the same coin

22 April 2021
Article by Pedro Marques, INEGI researcher, specialist in mechanical gear transmission tribology


Mechanical systems are present in all fields of modern life, namely in the fundamental industrial activities characteristic of contemporary society. From transportation, to energy generation and manufacturing, these activities depend on machines and machinery, whose constituent organs have surfaces that interact by contact, such as bearings, gears, alternative elements, among many others.

The duration, reliability and efficiency of these mechanical systems is closely linked to the phenomena of lubrication, friction and wear that occur between the surfaces in contact. The branch of science responsible for the study of these same phenomena is Tribology.

Recent studies show that approximately 23% of all energy produced worldwide is spent on the phenomena of interaction between contact surfaces in mechanical systems (tribological contacts). Of this slice, 20% is needed to supply the friction inherent in the operation of mechanical systems and 3% is used for the repair, manufacture and replacement of worn / damaged components due to faults in the tribological contacts [1].

Advances made at INEGI reduce energy waste

This data indicates that the impact of the friction and wear phenomena is not negligible, either at the economic level or at the environmental level. This, coupled with its transversal use in all branches of industry and transport, led INEGI to invest in the development of efficiency and reliability studies in bearing gears and mechanical transmissions.

Through this work, it was possible, for example, to create the fundamental geometry of gears capable of reducing the power dissipated by friction by 65% ​​(with reference to a helical gear) [2].

Also noteworthy is the study of the role of lubricants in the efficiency and reliability of mechanical transmission of wind turbines. In addition to concluding that the nature of the lubricant affects the reliability of the entire system, we obtained decreases of up to 45% in friction between the flanges of the gear teeth [2], in addition to decreases of friction up to 40% with bearing tests [3].

In the scope of this work, in addition to the practical and objective results, we established and validated the physical models necessary for the development of reliable and highly efficient mechanical transmissions.

Greater efficiency translates into economic and environmental gains

Efficiency and reliability often go hand in hand, since greater mechanical efficiency means less energy dissipated in tribological contacts. This, in turn, translates into a reduction in temperatures on the contact surfaces and, therefore, a decrease in the probability of failure of those same surfaces.

Greater efficiency also decreases the lubricant's operating temperatures, decreasing its oxidation rate over time and enhancing longer maintenance intervals. Because there is less energy dissipated, less power is required from thermal management systems.

In this way, the gains associated with mechanical systems with efficient tribological contacts go far beyond a reduction in the energy bill.

The accumulation of these efficiency gains means that tribology has, and will have in the coming years, a preponderant role in what concerns the reduction of carbon dioxide (CO2) emissions. In concrete terms, it is estimated that the optimization of tribological phenomena will translate, in the long term (about 15 years), into a potential decrease in CO2 emissions of around 3140 million tons per year [1].

A relevant impact, which leads me to affirm that Tribology is an important science for our future.



References

[1] - K. Holmberg, A. Erdemir, Influence of tribology on global energy consumption, costs and emissions. Friction 5, 263–284 (2017). https://doi.org/10.1007/s40544-017-0183-5

[2] - Carlos M.C.G. Fernandes, Pedro M.T. Marques, Ramiro C. Martins, Jorge H.O. Seabra, Gearbox power loss. Part II: Friction losses in gears, Tribology International, Volume 88, 2015, Pages 309-316, ISSN 0301-679X. https://doi.org/10.1016/j.triboint.2014.12.004

[3] - Carlos M.C.G. Fernandes, Pedro M.T. Marques, Ramiro C. Martins, Jorge H.O. Seabra, Gearbox power loss. Part I: Losses in rolling bearings, Tribology International, Volume 88, 2015, Pages 298-308, ISSN 0301-679X. https://doi.org/10.1016/j.triboint.2014.11.017