Investigation of tribological properties and engine performance of polyol ester–based bio-lubricant: Commercial motorbike engine oil blends

Abstract

This article explores the influence of blending polyol ester–based bio-lubricant with commercial lubricant on engine performance. Polyol esters trimethylolpropane ester and pentaerythritol ester were prepared from Calophyllum inophyllum seeds. Extreme care was taken to minimize deterioration of physicochemical properties when blending bio-lubricant with commercial oil. Blending of bio-lubricant with commercial oil was carried out in 10%, 15%, 20% and 25% volume. The test oils were first investigated for wear and friction properties on a four-ball wear tester. Optimum blending ratio was calculated from results of tribological properties, and the blend with optimum blend ratio was investigated for engine performance. The engine performance of the optimum blends was evaluated by conducting a 60-h endurance test on a motorbike. Significant improvement in tribological properties was observed up to a blending percentage of 15% when blending pentaerythritol ester with commercial oil. In the case of trimethylolpropane ester–based bio-lubricant, 10% blending with commercial oil gave optimum performance. The novel evaluation of engine performance of commercial oil and blends has shown a reduction in the wear of engine components with an encouraging decrease in fuel consumption. Metallographic studies conducted on worn piston rings reveal synergy between additives in the commercial oil and esters in the bio-lubricant in reducing wear and friction, thereby reducing fuel consumption.

Prospects of Plant-Based Trimethylolpropane Esters in the Biolubricant Formulation for Various Applications: A Review

“…The viscosity should be high enough to provide a thick film between moving components even at high temperature and pressure, yet low enough to keep the lubricant fluid around each component part (Sharma and Sachan, 2019). For an example, palm oil that is known as a biodegradable resource has a viscosity and viscosity index of 40.0 mm 2 /s (at 40 °C) and 191, respectively (Kotturu et al, 2020). A transesterification of methyl ester that is derived from palm oil with TMP to produce TMPE (Figure 2) has shown better lubricity properties, with a viscosity of 42.5 mm 2 /s (at 40 °C) and a viscosity index of 221 (Kotturu et al, 2020;Qiao et al, 2017).…”

“…For an example, palm oil that is known as a biodegradable resource has a viscosity and viscosity index of 40.0 mm 2 /s (at 40 °C) and 191, respectively (Kotturu et al, 2020). A transesterification of methyl ester that is derived from palm oil with TMP to produce TMPE (Figure 2) has shown better lubricity properties, with a viscosity of 42.5 mm 2 /s (at 40 °C) and a viscosity index of 221 (Kotturu et al, 2020;Qiao et al, 2017). In a different study, Kamarudin et al (2020) produced TMPEs from nonedible oils such as waste cooking oil and rubber seed oil via two-stage transesterifications and found that the viscosities of both TMPEs satisfied ISO VG46 lubricant standard.…”

“…Engine oil is critical for protecting parts from excessive heat formation and preventing corrosion (Kotturu et al, 2020). Engine oil consumed 48% of world market application (Mobarak et al, 2014).…”

“…One of the main attributes for an excellent lubrication is high affinity toward metal surfaces. A plant-based oil with a long chain fatty acid is normally required to increase lubrication and protection against friction and wear (Arumugam et al, 2014;Kotturu et al, 2020;Tulashie and Kotoka, 2020). The majority of research to date has looked at the friction and wear properties of vegetable oils alone or in the addition of particular additives.…”

“…In summary, the use of plant oils as lubricating oil is always associated with certain limitations such as poorer lowtemperature properties and poor oxidative stability during usage (Owuna, 2020;Yunus et al, 2004;Yunus et al, 2005). The alteration of plant oils' molecular structures or a blending with commercial oil, chemical additives, or nano-particles would further envisage the physicochemical properties of biolubricants, especially along boundary and hydrodynamic lubrication regimes (Chan et al, 2018;Hamdan et al, 2018;Gul et al, 2020;Kotturu et al, 2020;Srinivas et al, 2020). The chemical modifications of plant oil such as by epoxidation (Afifah et al, 2021;Bashiri et al, 2021), transesterification (Robiah et al, 2003;Aziz et al, 2014;Hamid et al, 2016;Zulkifli et al, 2016;Raof et al, 2019a), esterification (Fernandes et al, 2018;Kim et al, 2019;Rochmat et al, 2020), hydrogenation (Troncoso and Tonetto, 2022), and estolide formation (Salimon et al, 2011;Hoong et al, 2019) have been carried out to overcome the limitations by plant oils.…”