Migration pathways of oxygen and the formation of oxygenated intermediates in oxygenated fuel combustion

The combustion of oxygenated fuel produces more non-regulated pollutants which usually contain oxygen such as aldehydes than the combustion of hydrocarbon fuel. The formation of these oxygenated intermediates may be associated with the release of oxygen from the oxygenated fuel. In this paper, migration pathways of oxygen from several oxygenated fuels were investigated to obtain the formation characteristics of oxygenated intermediates. Major oxygenated intermediates and other intermediates were identified using synchrotron vacuum ultraviolet photoionization mass spectrometry in a dimethyl ether flame, an ethanol flame, and a propane flame. Their mole fractions were also evaluated. The results indicate that the oxygen from oxygenated fuel leads to an easier production of oxygenated intermediates, compared with oxygen from the oxidizer. The major oxygenated intermediate depends on the structure of the oxygenated fuel and was found to be formaldehyde in the dimethyl ether flame, and acetaldehyde in the ethanol flame. However, formaldehyde and acetaldehyde are present in low concentrations while hydrocarbon intermediates, such as ethene, ethyne, and propene, are present in high concentrations in the propane flame.