Combustion performance and exhaust emissions from the non-pressurised combustion of palm oil biodiesel blends

In this work, levels of exhaust species from the combustion of palm oil methyl ester (POME) and its blends with No. 2 diesel in a non-pressurised, water-cooled combustion chamber are evaluated. The study explores the correlations between emission species and fuel pumping pressures over a range of equivalence ratios (ERs). This is followed by a similar evaluation of emissions variation with POME proportions across the ER at predetermined values of fuel pumping pressure. Carbon monoxide (CO) level was found to be minimal when ER is within the 0.75-0.85 range, indicating improved combustion quality. As pumping pressure increases, the minimum CO level is raised but the optimum ER region is extended. Maximum nitric oxide (NO) production is recorded over this optimum ER range, and pumping pressure is seen to decrease the NO level only marginally. Exhaust CO improved across the tested ER range with increasing POME proportion in the fuel blends. This observed combustion improvement was offset by the accompanying increase in NO level when the POME content is raised. The work indicated the potential use of palm oil biodiesels in small-scale liquid fuel burners, although further examination is required to establish the optimum operating parameters and POME content for best NO-CO trade-off.