Thermal and chemical exhaust gas recirculation potential of punnai oil biodiesel-fuelled diesel engine for environmental sustainability

Major energy production all over the world depends on fossil fuels. Recent research on alternative energy sources has raised major concerns about environmental impacts, future availability, and cost. Pollution from diesel engines also affects the environment negatively. As a result, there is a worldwide concern about reducing the pollutants emitted by diesel engines. In comparison to diesel fuel, biodiesel combustion produces reduced carbon monoxide (CO2) and unburned hydrocarbon (UHC) emissions but higher nitrogen oxide (NOx) emissions. The current study aims to investigate the thermal and chemical effects of exhaust gas recirculation (EGR) on the features of a diesel engine for environmental sustainability. The punnai oil was produced from kernels of punnai seeds and transesterified in two phases using alcohol with the existence of a catalyst. The higher viscosity of punnai oil biodiesel is diluted by mixing it with diesel fuel. Our previous investigation indicated that neat punnai oil biodiesel is a potential fuel; however, the findings showed that the addition of diesel is necessary to obtain acceptable engine performance. In this study, punnai oil biodiesel was mixed at a rate of 20% with diesel (B20) and run in a diesel engine with varied EGR rates under five different engine loads. This combined impact enhanced the maximum heat release rate (HRR) and maximum combustion pressure, according to the findings. The premixed burning fractions were commonly higher at all engine loads, whereas the diffusion combustion fractions were lower. When the centre of the HRR changed toward the top dead centre (TDC), combustion durations remained rather constant. The experimental results revealed the B20 blend at a 10% EGR flow rate produced 6.57% lower BTE, 37.04% higher BSEC, 2.47% higher EGT, 5.13% lower CO, 31.11% higher CO2, 3.13% higher UHC, 8.36% lower NOx, and 4% higher smoke opacity when compared with diesel in a standard diesel engine.

Automated summary

The study investigates the effects of exhaust gas recirculation (EGR) on a diesel engine fueled with punnai oil biodiesel mixed with diesel (B20). The combination of punnai oil biodiesel with EGR enhances the maximum heat release rate and combustion pressure in the engine. The findings show that the premixed burning fractions are higher and diffusion combustion fractions are lower at all engine loads. The B20 blend with 10% EGR flow rate reduces CO and UHC emissions, increases CO2 emissions, decreases NOx emissions, and slightly increases smoke opacity compared to standard diesel fuel.