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Diesel Engines |
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Engine Performance Biodiesel is safe and can be used in diesel engines with little or no modification needed. Although biodiesel can be used in its pure form, it is usually blended with standard diesel fuel. Blends are indicated by the abbreviation Bxx, where xx is the percentage of biodiesel in the mixture. For example, the most common blend is B20, or 20 percent biodiesel to 80 percent standard. So, B100 refers to pure biodiesel. The energy content of neat biodiesel fuel is about eleven percent (11%) lower than that of petroleum-based diesel fuel (on a per gallon basis), which results in a power loss in engine operation. The viscosity range of biodiesel fuel, however, is higher than that of petroleum-based diesel fuel (1.9 – 6.0 centistokes versus 1.3 – 5.8 centistokes), which tends to reduce barrel/plunger leakage and thereby slightly improve injector efficiency. The net effect of using B100, then, is a loss of approximately five to seven percent (5-7%) in maximum power output. The actual percentage power loss will vary depending on the percentage of biodiesel blended in the fuel. Neat biodiesel and higher percentage biodiesel blends can cause a variety of engine performance problems: - Corrosion of FIE components. - Elastomeric seal failures - Low pressure fuel system blockage - Fuel injector spray hole blockage - Increased dilution and polymerisation of engine sump oil - Pump seizures due to high fuel viscosity at low temperatures - Increased injection pressure At low ambient temperatures, biodiesel is thicker than conventional diesel fuel, which would limit its use in certain geographic areas. The incidence of these effects is likely to be increased when the engine is in irregular use, in applications such as stand-by generator units, automatic plant and seasonally used vehicles. When biodiesel fuels are used, the condition of seals, hoses, gaskets, and wire coatings should be monitored regularly. There is limited information on the effect of neat biodiesel and biodiesel blends on engine durability during various environmental conditions. More information is needed to assess the viability of using these fuels over the mileage and operating periods typical of heavy-duty engines.
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