Fraer et al.[70] investigated the effect of biodiesel B20 on different engine parts through a comparative research. Eight trucks from the United States Postal Services (USPS) were investigated. Four 1993 Ford 9-tonne cargo vans each powered by a 6 cylinder 7.8 litre engine and four 1996 Mack
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articulated trucks each powered by a 6 cylinder 12 litre engine. Two of each group were operated on B20 and the others on PD. The study was a four year program between 2000~2004 during which the vehicles ran on B20 for 960,000 km accumulated distance. The engines and fuel systems were removed, disassembled, and inspected. They reported no discernible differences in engine part wear, except sludge build up on the valves deck around the rocker assemblies was seen. This was attributed to out-of- specification B20 fuel batches in one of the Mack trucks as biodiesels contain relatively high concentrations of sodium from the transesterification process. A PD fuelled Ford truck had big end and main bearings failure due to unidentified improper lubrication.
Chase et al.[71] ran durability and performance tests on two heavy duty Caterpillar engines with rated power output of 435 hp. They used hydrogenated soy ethyl ester (HySEE) 1:1 blends with type-2 PD. The first engine was conditioned and bench tested for pollution investigation, while the second was mounted on a Kenworth heavy duty truck. The test vehicle consumed 70,379 litres of HySEE and a total of 145,746 litres of fuel and ran for 326,235 km. Their results showed that using the arctic package and vehicle indoor parking allowed the vehicle to operate in all weather conditions. Engine teardown showed no accelerated engine degradation and the vehicle was expected to run for more than 1.6 million km.
Nishimura et al.[72] examined the impact of UCO-BD on engine lubricating oil performance in a fleet of seven cargo vehicles. They focused on engine wear and high temperature corrosion. The results were compared to those obtained from their bench tests. They concluded that engines fitted with a diesel particulate filter (DPF) exhibited higher oil viscosity reduction and more lubrication oil dilution by the fuel. This was attributed to the increase in back- pressure due to prolonged post injection period for DPF regeneration. The higher back-pressure enhances the blow-by process and as the UCO-BD possesses a higher boiling point than PD, it tends to remain for extended periods of time in the oil sump. They also observed a steady state lubrication oil level in the sump for the vehicles fuelled with UCO-BD. This was related to the equilibrium between the higher lubrication oil dilution and consumption. Laboratory tests for anti-wear characteristics using the four-ball machine revealed that a combination of UCO-BD with fresh lubrication oil showed minimum wear scar or the highest anti-wear performance. They concluded that UCO-BD has an anti-wear effect which counteracts oil degradation due to dilution with fuel. Copper and lead corrosion were higher in a mixture of
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20% UCO biodiesel and fresh lubrication oil compared to an analogous mixture with used lubrication oil. This was attributed to the formation of the carboxylic acids from the degradation of the UCO and the oil which was higher in the case of the mixture with used oil.
Fazal et al.[73] studied the effect of palm oil derived biodiesel on the degradation of metal parts of the engine and compared the results to those of PD. The study was conducted on four metals namely, copper, brass, aluminium, and cast iron. The metals were immersed in the fuels for 2880 hours at 25~27°C then examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS). They concluded that BD is more corrosive than the PD. The metals showed different responses to the BD. Their response from the most affected was Cu, BS, Al, and Fe respectively. Different metal compounds were found on the exposed surfaces and the biofuel degraded at different levels while embracing the metals. The response of BD from the worst to the less affected was Cu, BS, Al, and Fe respectively. Shahid and Jamal [74] concluded in their review the suitability of vegetable oils derived biodiesel as alternative fuels. They stated that more care and periodic services are required for the engines operated with BD’s due to the higher carbon deposits in the combustion chamber and particularly on nozzle tips. Fraer et al [70] found no differences in fuel injection pump wear and performance with the exception of Mack trucks fuelled with the B20. They were more susceptible to fuel injector and fuel filter replacements because of the out-of-specification fuel batches, the biological contamination of the fuel and the larger amounts of fuel circulation in the fuel system.
In the current research, a thorough investigation for the combustion chamber configuration, revealed that it is hard for the fuel to reach the cylinder walls or piston rings to result in any deposits or damage. Therefore engine deterioration and deposit accumulation was planned to be inspected periodically through fuel injector inspection. A couple of fuel injectors from different cylinders were removed for inspection to indicate the effect of deposit aging at different HGV mileages (as explained in Chapters 3 and 5).