A Laboratory Combustion Study of Diesel Particulates Containing Metal Additives

Diesel soot samples, containing Cu, Pb, or mixed Mn-Cu additives, were generated in 4.3 and 5.7 L engines under idle and 65 km/h road-load conditions. The soot was collected on ceramic fiber filters, samples of which were subsequently transferred to a controlled atmosphere laboratory flow reactor for analysis of soot oxidation characteristics. Ignition temperatures and propagation speed of the combustion zone were measured by infrared pyrometry and photography, respectively, as a function of additive type, O₂ concentration, and gas flow rate. Soot containing Cu additive showed the lowest ignition temperature in room air (ca 300 C). A mathematical analysis is presented which predicts the effects of O₂ concentration and superficial velocity on ignition temperature. The model demonstrates that the most important heat transfer terms affecting the ignition temperature are those of convection and heat of reaction (as controlled by the rate of O₂ supply).