Abstract
Similarities in the structure of spray flames suggest that higher fuel injection speeds would reduce NOx emission as the fuel residence time in the reaction zone would shorter. However, in diesel combustion it is commonly known that NOx emissions increase when the fuel injection velocity is increased. The authors have suggested from experimental and numerical analysis that the mixing time scale is significantly large at the spray tip region and existence of this unsteady structure is the major difference of the two flames. The purpose of this paper is to examine the effect of pre-injection of inert gas and air for the reduction of NOx : the aim was to eliminate the weak mixing zone at the tip and to create a fuel flow similar to a well developed jet structure. Experimental results showed NOx emissions decreased with his method, and the results provide clues to ways of reducing NOx in diesel spray flames.
