4. Results and discussion
4.1. Effect of COCO blends on engine performance
Fig. 1 shows the engine performance at constant 50% throttle position with varying speed, such as from 800 to 3200 rpm. It was observed that all the COCO blends developed similar brake power as conventional diesel, even at higher engine speed 10–30% COCO blends produced higher brake power than conventional diesel. This is can be expected due to the slightly larger fuel droplets and oxygen content in COCO which contribute to better atomisation. Maximum brake power for each fuel was obtained at 1600 rpm and the value was within 9 to 9.5 kW. However, at 50% throttle position, the engine uses higher air fuel ratio, and as a result complete combustion occurs. Fig. 2 shows that the specific fuel consumption increases with increasing COCO in blends. This is mainly due to the relationship among volumetric fuel injection system