Experimental Investigation of Neat Biodiesels’ Saturation Level on Combustion and Emission Characteristics in a CI Engine

Abstract

The fuel qualities of several biodiesels containing highly saturated, mono, and poly unsaturated fatty acids, as well as their combustion and exhaust emission characteristics, were studied. Six biodiesel samples were divided into two groups based on their fatty acid composition, including group 1 (coconut, castor, and jatropha) and group II (palm, karanja, and waste cooking oil biodiesel). All fuels (in both groups) were tested in a single-cylinder off-road diesel engine. Castor and karanja biodiesel, both rich in mono-unsaturation level, have a high viscosity of about 14.5 and 5.04 mm2/s, respectively. The coconut and palm biodiesels are rich in saturation level with cetane numbers of 62 and 60, respectively. In both groups, highly saturated and poly-unsaturated methyl esters presented better combustion efficiency and less formation of polluted emissions than mono-unsaturation. At full load, coconut and palm biodiesel displayed 38% and 10% advanced start of combustion, respectively, which reduced ignition delay by approximately 10% and 3%, respectively. Mono-unsaturated methyl esters exhibited a higher cylinder pressure and heat release rate, which results in higher NOx gas emissions. The group II biodiesels showed about 10–15% lower exhaust emissions owing to an optimum level of fatty acid composition. Our study concluded that highly saturated and poly-unsaturated fatty acid performed better than mono-unsaturated biodiesels for off-road engine application.

Study on Using Graphene and Graphite Nanoparticles as Fuel Additives in Waste Cooking Oil Biodiesel

“…7b & 7c). While increasing the engine torque increases the fuel injection quantity/ strokes, hence increasing the in-cylinder temperature [37]. This phenomenon also increases the fuel injection pressure, as shown in Figs.…”

“…Furthermore, at low loads, the in-cylinder temperature is relatively low. Combined effects of low in-cylinder temperature and higher ignition delay (due to low cetane number) caused more fuel to burn in the premixed combustion phase, which gave higher in-cylinder pressure [37]. Whereas in-cylinder pressure for NP blends increased with increased engine load at medium and full load conditions (Fig.…”

“…It is observed that the SoC was retarded for all the blends compared to W100 even though W100 has a higher viscosity. Neat biodiesel (W100) has a higher cetane number than diesel [37]. The higher the cetane number lower the delay [34].…”

“…The burn duration (BD) is defined as the interval between the SoC and EoC. The BD increases with increasing the engine load due to high fuel injection quantity per stroke [37]. Overall, blends with NcP and C additives showed shorter BD at almost all loads.…”

“…The fuel quantity/stroke is less at lower engine load, the pumping force used by the fuel pump is lower, but fuel quantity increases with engine load. Therefore, the fuel pump has to apply more force to inject the required quantity of fuel/stroke [37]. Hence, fuel injection pressure also increased with engine load (Fig.…”