Investigation on the impact of papaya biodiesel-diesel blends on combustion of an agricultural CI engine

In this study, an overview of combustion characteristics of an agricultural diesel engine fuelled with papaya seed oil (PSO) biodiesel and diesel is presented. A naturally aspirated four-cylinder four-stroke tractor engine was used for all experiments. Various PSO blends (5%, 10%, and 20%) were tested and compared with diesel at speeds of 1400 rpm and 2400 rpm at full load condition. The combustion characteristics such as in-cylinder pressure, heat release rate, ignition delay, mass fraction burned, ignition duration and cylinder temperature were tested. The results show that PSO blends have some excellent attributes as fuel in regard to combustion characteristics. All PSO biodiesel blends have higher in-cylinder pressure; for example, PSO20 has 2.4% more than diesel. Heat release rate values of all PSO biodiesel blends were found to be lower than diesel due to the shorter ignition delay and lower calorific values of biodiesel. PSO20 biodiesel shows faster combustion than diesel by about 11.92% at 1400 rpm and 7.93% at 2400 rpm. The maximum cylinder temperature of all PSO biodiesel blends are also higher than that of diesel, such as PSO20 at 1400 rpm by 3.17% and at 2400 rpm by 3.73%.