Experimental Investigation of the Effects of Biodiesel Composition and Structure on Tailpipe Oxides of Nitrogen (Nox) and Other Emissions

Biodiesel chain length and degree of unsaturation impacts the NOx emissions in engines. This work presents experimental investigation of the effects of biodiesel chemical composition and molecular structure (numbers of double bonds and chain length) and other physical properties on NOx emissions. A methodology to decouple the effects of degree of unsaturation and chain length is presented. Results shows that biodiesels of linseed, hazelnut, rapeseed, soyabean, corn, sunflower, walnut and algae oils produce different exhaust temperatures- algae based biodiesel gives the lowest exhaust temperature while sunflower biodiesel has the highest. Biodiesel from sunflower oil produces the highest tailpipe NOx emissions both at transient and steady tailpipe conditions and at varying BSFC and algae based biodiesel lowest NOx emissions. However, algae biodiesel found to give highest CO, HC and CO 2 emissions. NOx emissions found to increase as the degree of unsaturation increases, peaking at an average degree of unsaturation of 1.5. Shorter chain length esters found to produce lower NOx emissions which were found to decrease until the chain length factor of 0.765 was reached. Finally, NOx emissions with biodiesel acid number, pA value, PV value, TOTOX value, CD value, OSI, Viscosity, iodine value, BAPE and density is presented