Results and Discussion: Preheated Biodiesel Blends Run Engine
6.3 Result and Discussion
6.3.1 Characterization of Preheated POME Biodiesel Blends
gas. Sufficient mixing of incoming air and recirculated exhaust gas is ensured inside the mixing chamber before it gets induced into the combustion chamber.
results reveals that the kinematic viscosity of each blends of fuel significantly decreased with heating of biodiesel at elevated temperature. However, the blended fuel viscosity still meets the blended fuel standard requirements ASTM D7467 for up to 60% biodiesel blending ratio (PPBD60). The viscosity of the blended fuel PPBD60 is 4.08 mm2/s, which is higher than that of diesel fuel (3.23 mm2/s) by about 1.26 times. However, the blended fuel viscosity for up to 100%
(5.37 mm2/s) satisfies the limits given in the specification of biodiesel standard requirements of ASTM D6751, EN14214 and IS15607, which is 6.0 mm2/s and it is about 1.66 times higher than the fossil diesel at room temperature.
6.3.1.2 Effect of Fuel Preheating and Blending on Density
Figure 6.2(b) shows the variation of density with volumetric percentage of preheated POME biodiesel-diesel blend. It is observed that the density increases linearly with an increase in the blending ratio due to an increase in the volumetric percentage of biodiesel in the blend ratios as the density of POME biodiesel is higher than diesel. Accordingly, the density of the blended fuel PPBD60 is 1.5% lower than that of PPBD100 due to the effect of preheating biodiesel and blending with diesel. It was observed in Figure 6.2(b) that, the density of the preheated blends decreased marginally for all the tested fuels. The density of PPBD20 and PPBD40 were within the blended fuel standard requirements ASTM D7467 and BIS, in ranges of 851−859 kg/m3, while the blends PPBD60, PPBD80 and PPBD100 are out of the blended fuel standard requirements, but only conformed to the ASTMD 6751, EN14214 AND IS15607 standard specification when heated to temperatures of 114°C to lower the density to the specified maximum of 900 kg/m3.
6.3.1.3 Effect of Fuel Preheating and Blending on Calorific Value
Calorific value is an important parameter in the selection of a fuel. It is the amount of heat released during the complete combustion of one gram of fuel. This value determines the chemical energy of the fuel which specify the combustion efficiency. Table 6.1shows that the heating value of the preheated POME biodiesel-diesel blend decreased with a higher volumetric percentage of the biodiesel. The minimum heating value measured was 40.12 MJ/kg for PPBD100, which satisfies the requirements of the EN 14213 Standard. The heating value for POME biodiesel is approximately 14.32% lower than the heating value of mineral diesel (44.69 MJ/kg). Figure 6.3 shows variation of calorific value with preheated POME biodiesel/diesel blending ratio. In contrast to density and kinematic viscosity, it shows a decrease in calorific value of PPBD20, PPBD40,
PPBD60, PPBD80 and PPBD100 with increasing biodiesel ratios in blended fuel (44.12, 43.32, 42.67, 41.78 and 40.12 MJ/kg). The decrease in calorific value is due to the increase in biodiesel in the mixture of biodiesel-diesel blend as the calorific value of biodiesel is lower than diesel.
Increase in calorific value is expected to improve the engine combustion efficiency, thus reduce the BSFC of the engine.
(a) (b)
Figure 6.2: Variation of fuel property with percentage of preheated biodiesel blends: (a) kinematic viscosity; (b) density.
6.3.1.4 Effect of Fuel Preheating and Blending on Flash Point
The flash point is the minimum temperature at which a fuel emits enough vapour to get ignited.
The higher the flash point, the higher the temperature required to ignite the fuel. On the one hand, it is better to lower the flash point for combustion purposes. However, the higher flash point means the fuel is safer to transport. Generally, higher flash point is preferred. Table 6.1 presents the variation of flash point with preheated biodiesel blending ratio. It varies from one blend to another.
Like pour point, it also shows an increasing tendency with increase in blending ratio as the flash point is higher for POME biodiesel.
Figure 6.3: Variation of calorific value with percentage of preheated POME biodiesel blends.
6.3.1.5 Optimum Preheated Blending Ratios
When preheated biodiesel is blended with diesel the characteristics of the new fuel changes as per the volumetric percentage of biodiesel in a mixture of biodiesel and diesel. The blending ratio will be optimum when the blended fuel will satisfy the different standards as specified by the different countries.Accordingly, an optimum blending ratio was recommended for the POME at the ratios of 20% to 60% according to the properties of the POME−diesel blends. The optimal blends (PPBD20−PPBD60) would have the kinematic viscosity of 3.38 mm2/s to 4.08 mm2/s and density of 851 kg/m3 to 863 kg/m3 which comply with the limits of the blended biodiesel standard specifications. The calorific value (43.12 MJ/kg −41.67 MJ/kg), flash point (103 °C−181°C) and pour point (-1°C to 4 °C) are above the lower limit (35 MJ/kg, 52 °C and 3 max.), respectively. So an optimum blending ratio of up to 60% blending (up to PPBD60) has been recommended by compliance of the preheated biodiesel-diesel blend specification to the specified standards, which can be used in diesel engines without modification and without sacrificing much power loss.