Effect of Spray and EGR Rate on the Combustion and Emission Characteristics of Biodiesel Fuel in a Compression Ignition Engine

Abstract

An experimental investigation was performed to analyze the effects of undiluted biodiesel fuel (100% methyl ester of soybean oil) on spray, combustion, and exhaust emissions characteristics in a direct injection (DI) common-rail diesel engine with a cooled-EGR system. The macroscopic and microscopic injection characteristics for test fuels such as injection mass, injection rate, droplet diameter, and spray tip penetration were measured by using an injection rate meter, a spray visualization system, and a droplet measuring system. The study of combustion and exhaust emission characteristics was carried out under various engine operating conditions for biodiesel fuel, and the results were compared to those of ultra low sulfur diesel (ULSD). In this work, the injection characteristics of test fuels such as injection rate and mass results are very similar for diesel and biodiesel fuel derived from soybean oil. However, when comparing the start of injection, biodiesel resulted in short injection delay. The Sauter mean diameter (SMD) of biodiesel fuel is higher than that of diesel fuel, and biodiesel showed longer spray tip penetration as compared to that of diesel fuel. Combustion of diesel and biodiesel fuels indicated similar patterns of combustion pressure and rate of heat release. However, the combustion of biodiesel showed lower peak combustion pressures and peak heat release rates than those of diesel fuel becase of its LHV (lower heating value). The comparison of emission characteristics of biodiesel and diesel fuel shows that the biodiesel fuel emitted higher indicated specific NO x and a remarkably low level of soot emissions.

Performance and emission characteristics of compression ignition engine using methyl ester blends of jatropha and fish oil

“…Biodiesel has low sulphur content, low aromatic content and oxygen containing compounds due to which the emissions of SO2, CO2, HC and PM are reduced. Besides, it has good ignition ability in engine owing to its high cetane number compared to that of conventional diesel fuel [10,[18][19][20][21][22][23].…”

Biodiesel as Diesel Engine Fuel

“…As the pressure is increased, less space between molecules is available, and the resistance of compression increases. Thus, the bulk modulus increases with the increase of injection pressure (Yoon et al 2009). A higher bulk modulus leads to a more rapid pressure wave propagation from the pump to the needle nozzle and an earlier needle lift.…”

Effects of Biodiesel Usage on Injection Process Characteristics

“…In general, an increase of the injection pressure results in an increase in NO x emission and a decrease in soot emissions (Song et al 2012). Biodiesel influences significantly the fuel injection pressure; however, this influence is more exposed in MCFIS and less in ECFIS (Boudy and Seers 2009;Kegl 2006a;Kegl and Hribernik 2006;Luján et al 2009a, b;Payri et al 2012;Postrioti et al 2004;Tziourtzioumis and Stamatelos 2012;Zhang and Boehman 2007;Ye and Boehman 2012;Yoon et al 2009). …”

“…In spite of that, they are measurable and have to be taken into account (Song et al 2012). For example, at the same operating conditions and at the same injection fuelling, soybean biodiesel (SoBIO) usage results in a slightly shorter injection delay and consequently in slightly advanced injection timing, compared to mineral diesel (Yoon et al 2009). The reason for advanced injection timing is mainly due to the higher bulk modulus of biodiesel.…”

“…However, biodiesel fuels have higher density than mineral diesel, which implies that the mass of the injected fuel remains rather constant. These two counteracting effects can explain why there are no significant differences between both fuel injection rates in a high pressure common rail system (Luján et al 2009a, b;Yoon et al 2009). …”