Experimental investigation of the effect of Al2O3 nanoparticles as additives to B20 blended biodiesel fuel: Flame characteristics, thermal performance and pollutant emissions

Palm oil biodiesel has been identified as a renewable energy source with a huge potential to replace liquid fossil fuels in the future. The current experimental work investigates the effect of using Al2O3 nanofuel produced by adding Al2O3 nanoparticles to 20 % blend of palm oil biodiesel with diesel fuel on the flame characteristics, radiation, temperature and pollutant emissions in an oil burner. A homogeneous suspension was prepared from Al2O3 nanoparticles, of the concentration of 500 ppm, in B20 blended biodiesel fuel. The Infrared Radiation (IR) of the flame, the flame temperature, luminosity, radiative heat flux and CO and NOx pollutant emissions were measured and compared with those of B20 fuel. The results indicate that Al2O3 nanoparticles enhance the evaporation rate of nanofuel droplets and shift the maximum flame temperature to the upstream region. Al2O3 nanoparticles favor scattering of heat over heat absorption, which accelerates flame heat transfer and decreases its temperature. Nevertheless, Al2O3 nanoparticles improve soot particles nucleation and surface growth and increase the highly emissive intermediate soot particles in the flame reaction zone. These intermediate soot particles enhance the luminosity and IR and total radiation heat transfer of the flame. The enhancement rate for average flame radiation of B20 blend fuel was as much as 10 % and higher concentrations of nanoparticles led to a substantial increase in the radiation heat flux. However, they cause an increase in the CO emission from 48 to 62 ppm which is in the standard level. Finally, the use of the nanofuel instead of B20 fuel decreases the NOx emission by 11 %