Performance, emission, combustion and economics analysis of CI engine fueled with mixed oil biodiesel blends from waste cooking oil and pongamia oil

The increasing demand for fossil fuels, coupled with environmental concerns and fluctuating petroleum prices, has necessitated the search for sustainable alternative fuels. This study evaluates the performance, emissions, combustion characteristics, and economic feasibility of a CI engine running on mixed oil biodiesel. Waste cooking oil (50%) and Pongamia oil (50%) were blended before transesterification, reducing production costs and processing time. Various biodiesel blends (D95BWP5, D90BWP10, D85BWP15, D80BWP20, and D75BWP25) were tested under different load conditions. The results showed that brake thermal efficiency decreased by 17.32%, while brake specific energy consumption increased by 20.1% for D75BWP25 compared to diesel. All biodiesel blends exhibited lower carbon monoxide (CO), hydrocarbon (HC), and smoke emissions, though nitrogen oxide (NOx) emissions increased due to the higher oxygen content. Diesel recorded the highest rate of pressure rise at 6.28 bar/°CA and net heat release rate at 56.32 J/°CA. The economic analysis revealed that the production cost of mixed oil biodiesel was ₹83 per liter, which is lower than diesel, and engine operating costs were also reduced. Among the tested blends, B20 provided the best balance of performance, emissions reduction, and fuel efficiency while offering better engine compatibility and cold flow properties than higher blends. It met ASTM standards, ensuring reliability, and reduced greenhouse gas emissions by up to 30%. Overall, B20 remains a cost-effective and sustainable fuel alternative for diesel engine applications. For future work, study suggest the investigation of advanced combustion strategies to reduce NOx emissions in biodiesel blends.