NOx Emissions Reduction in a Biodiesel Engine by Means of EGR Technology

Biodiesel-fuelled engines produce less carbon monoxide, unburned hydrocarbon, and particulate emissions compared to conventional diesel fuel but higher NO_x emissions - the greatest threat to the ozone layer. This behaviour is attributed to the higher content of oxygen of the biodiesel. A recognized technique for attaining lower NO_x emission levels on Diesel engines is the exhaust gas recirculation (EGR). In order to evaluate if this technique is also valid for biodiesel blends, a review is made concerning the effect of EGR on emissions of diesel engines (one and two cylinders) running with different biodiesel blends and for different EGR rates. Data about conventional diesel are also shown for comparison purposes. Similar results were found in both cases (one and two cylinders) and conclusion can be drawn that NO_x emissions decrease with the increasing of EGR rate. The degree of reduction in NO_x at higher loads is also higher. The reasons for reduction in NO_x emissions using EGR in diesel engines are reduced oxygen concentration and decreased flame temperatures.