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This paper aims to investigate the effects of low-viscosity and ultralow-viscosity engine oils on the comprehensive friction and fuel economy of turbocharged gasoline direct injection (TGDI) through simulation analysis and experiments.

Numerical analysis models of friction loss for reciprocating, crankshaft and valve train are established. Based on the FAST, the friction loss of 24 specific parts of a TGDI engine was analyzed. Finally, the engine test bench was built, which was used to test the mechanical loss, external characteristics and universal characteristics.

Compared with the baseline oil, lower viscosity lubricating oil can reduce the friction loss of nine components to varying degrees. When the viscosity decreases, the friction distribution ratio of reciprocating, crankshaft and balance shaft will gradually decrease. The proportion of reciprocating when using 0W12 is reduced by 4%. Tests have shown that ultralow viscosity engine oil reduces torque loss by up to 15.74% (2,000 rpm, full throttle), but its fuel consumption rate becomes higher in low-speed and high-torque conditions.

This work helps to understand the effect of lubricating oil characteristics on the comprehensive friction performance of the engine.

This paper aims to present a comprehensive perspective on how tribology and sustainability are related and intertwined and are linked to CO₂ emissions. This paper emphasizes on how tribological aspects affect everybody’s life and how tribological research and progress can improve energy efficiency, sustainability and quality of life.

Based upon available data and predictions for the next 50 years, the potential of tribological research and development is addressed.

The effects of tribological design can significantly increase energy savings and reduce CO₂ emissions. Taking advantage of tribological technologies and applying them to current infrastructure would have the largest energy savings coming from the transportation and power generation at 25% and 20%, respectively. Implementing these technologies can also cut down global CO₂ emissions by about 1,460 megatons of CO₂ per year in the immediate future and 3,140 megatons of CO₂ per year in the long term. The extraction and processing of resources inevitably generates CO₂. Doubling the lifetime of machine components and the use of circular economy reduces the material footprint with associated reductions in CO₂.

This perspective summarizes concisely the interrelation of tribology and sustainability with CO₂.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2020-0356/

As a high-performance engineering plastic, polyimide (PI) is widely used in the aerospace, electronics and automotive industries. This paper aims to review the latest progress in the tribological properties of PI-based composites, especially the effects of nanofiller selection, composite structure design and material modification on the tribological and mechanical properties of PI-matrix composites.

The preparation technology of PI and its composites is introduced and the effects of carbon nanotubes (CNTs), carbon fibers (CFs), graphene and its derivatives on the mechanical and tribological properties of PI-based composites are discussed. The effects of different nanofillers on tensile strength, tensile modulus, coefficient of friction and wear rate of PI-based composites are compared.

CNTs can serve as the strengthening and lubricating phase of PI, whereas CFs can significantly enhance the mechanical properties of the matrix. Two-dimensional graphene and its derivatives have a high modulus of elasticity and self-lubricating properties, making them ideal nanofillers to improve the lubrication performance of PI. In addition, copolymerization can improve the fracture toughness and impact resistance of PI, thereby enhancing its mechanical properties.

The mechanical and tribological properties of PI matrix composites vary depending on the nanofiller. Compared with nanofibers and nanoparticles, layered reinforcements can better improve the friction properties of PI composites. The synergistic effect of different composite fillers will become an important research system in the field of tribology in the future.