Ternary or binary blend? A case study using papaya seed oil biodiesel

This study investigates the effects of binary and ternary blends of papaya seed oil (PSO) biodiesel with diesel in a fully instrumented diesel engine. The PSO binary blend was prepared as a 5% volumetric mix of PSO biodiesel with 95% diesel denoted as PSO5. Two ternary blends were made, one with a 5% volumetric mix of diglyme, 20% PSO biodiesel and 75% diesel, denoted as P20DG5, and the other with 5% n-butanol, 20% PSO biodiesel with 75% diesel denoted as P20B5. All fuels were tested under full load condition with the variation of engine speeds from 1200 rpm to 2400 rpm. The engine performance results showed that the average brake power (BP) value increased by only 1.2% for the P20DG5 blend and torque value differences in binary and ternary blends were found to be insignificant. An average decrease in the brake specific fuel consumption (BSFC) value for the P20DG5 was recorded as only 0.48%, whereas PSO5 and P20B5 increased by 3.36% and 3.1% respectively. The brake thermal efficiency (BTE) of P20DG5 showed as 6.15% higher than PSO5, while that value for P20B5 was found to be insignificant. The P20DG5 ternary blend was the only blend that produced lower NOx emissions than diesel, that being 0.64%. The ternary blends of P20DG5 and P20B5 exhibited lower emissions of CO (100% and 63% respectively), PM (59.5% and 41.2%) and HC (33.3% and 29.4%) than the binary blend of PSO5. The overall results showed that PSO biodiesel with diglyme additive performed better than both the n-butanol blend and the PSO5 binary blend. It is therefore worth incurring extra cost for adding diglyme additive (5%) and compensate for that by using more biodiesel (20%) in the biodiesel-diesel blend.