This research was aimed to examine the diesel engine’s performance and emission of secondary fuels (SFs), comprising waste plastic oil (WPO) and palm oil biodiesel (POB), and to analyze their tribological properties. Their compositions were analyzed by gas chromatography–mass spectrometry (GC–MS). Five SFs (10–50% POB in WPO) were prepared by mechanical stirring. The results were compared to blank WPO (WPO100) and Malaysian commercial diesel (B10). WPO90 showed the maximum brake power (BP) and brake torque (BT) among the SFs, and their values were 0.52 and 0.59% higher compared to B10, respectively. The increase in POB ratio (20–50%) showed a negligible difference in BP and BT. WPO70 showed the lowest brake-specific fuel consumption among the SFs. The brake thermal efficiency (BTE) increased with POB composition. The maximum reductions in emission of hydrocarbon (HC, 37.21%) and carbon monoxide (CO, 27.10%) were achieved by WPO50 among the SFs. WPO90 showed the maximum reduction in CO 2 emission (6.78%). Increasing the POB composition reduced the CO emissions and increased the CO 2 emissions. All SFs showed a higher coefficient of friction (COF) than WPO100. WPO50 showed the minimal increase in COF of 2.45%. WPO90 showed the maximum reduction in wear scar diameter (WSD), by 10.34%, compared to B10. Among the secondary contaminated samples, SAE40-WPO90 showed the lowest COF, with 5.98% reduction compared to SAE40-WPO100. However, with increasing POB content in the secondary contaminated samples, the COF increased. The same trend was also observed in their WSD. Overall, WPO90 is the optimal SF with excellent potential for diesel engines.

The constant utilization of petroleum-based products has prompted concerns about the environment, hence a replacement for these products must be explored. Biolubricants are a suitable replacement for petroleum-based lubricants as they provide better lubricity. Biolubricant performance can be improved by the addition of graphene. However, there are reports that graphene is unable to form a stable suspension for a long period. This study used a graphene-ionic liquid additive combination to stabilize the dispersion in a biolubricant. Graphene and ionic liquid were dispersed into the biolubricant via a magnetic stirrer. The samples were tested using a high frequency reciprocating rig. The cast iron sample was then further observed using various techniques to determine the lubricating mechanism of the lubricant. Different dispersion stability of graphene was observed for different biolubricants, which can be improved with ionic liquids. All ionic liquid samples maintained an absorbance value of three for one month. The utilization of ionic liquid was also able to decrease the frictional performance by 33%. Further study showed that by using the ionic liquid alone, the frictional could only reduce the friction coefficient by 13% and graphene could only reduce the friction by 7%. A smooth worn surface scar can be seen on the graphene-IL sample compared to the prominent corrosive spot on the IL samples and abrasive scars on graphene samples. This indicates synergistic behavior between the two additives. It was found that the ionic liquid does not only improve the dispersion stability, but also plays a role in forming the tribolayer.

No abstract

This paper investigates the importance of tribology towards the global economy. The current world energy crisis, the depletion of fossil fuel reserves and the increasing of environmental hazards over the years have urged academicians and scientists to continuously seek for methods to overcome these problems while improving the quality of life in the same time. Energy saving can be achieved through the implementation of tribological improvements in various sectors such as transportation, manufacturing, power generation and residential sectors. The friction reductions eventually lead to wear reduction, energy loss reduction and CO2 emission reduction due to the lesser energy consumption. Therefore, it can be concluded that advanced tribological technologies benefits the entire world in the economical aspect through energy saving and emission reductions.

The main purposes of this research were to study the diesel engines' performance and emission characteristics of quaternary fuels, as well as to analyze their tribological properties. The quaternary comprised waste plastic pyrolysis oil, waste cooking oil biodiesel, palm oil biodiesel, and commercial diesel. Their compositions were analyzed by gas chromatography and mass spectrometry. By using mechanical stirring, four quaternary fuels with different compositions were prepared. Because Malaysia is expected to implement B30 (30% palm oil biodiesel content in diesel) in 2025, B30a (30% palm oil biodiesel and 70% commercial diesel) mixture was prepared as a reference fuel. In total, 5%, 10%, and 15% of each waste plastic pyrolysis oil and waste cooking oil biodiesel were mixed with palm oil biodiesel –commercial diesel mixture to improve fuel characteristics, engine performance, and emission parameters. The palm oil biodiesel of the quaternary fuel mixture was kept constant at 10%. The results were compared with B30a fuel and B10 (10% for palm oil biodiesel and 90% for diesel; commercial diesel). The findings indicated that compared with B30a fuel, the brake power and brake thermal efficiency of all quaternary fuel mixtures were increased by up to 2.78% and 9.81%, respectively. Compared with B30a, all quaternary fuels also showed up to a 6.31% reduction in brake-specific fuel consumption. Compared with B30a, the maximum carbon monoxide and carbon dioxide emissions of B40 (60% commercial diesel, 10% palm oil biodiesel, 15% waste plastic pyrolysis oil and 15% waste cooking oil biodiesel) quaternary fuel were reduced by 19.66% and 4.16%, respectively. The B20 (80% commercial diesel, 10% palm oil biodiesel, 5% waste plastic pyrolysis oil and 5% waste cooking oil biodiesel) quaternary blend showed a maximum reduction of 41.86% in hydrocarbon emissions collated to B30a. Compared with B10, the average coefficient of friction of the quaternary fuel mixture of B40, B30b (70% commercial diesel, 10% palm oil biodiesel, 10% waste plastic pyrolysis oil and 10% waste cooking oil biodiesel), and B20 were reduced by 3.01%, 1.20%, and 0.23%, respectively. Therefore, the quaternary blends show excellent utilization potential in diesel engine performance.