Effect of water content on pollutant formation in a burning spray of water-in-diesel fuel emulsion

Abstract

The effect of varying the water content of a range of water-in-diesel fuel emulsions on the combustion process in a confined continuously burning spray, while keeping other parameters constant, is described. Experimental measurements of the concentrations of the products of combustion and of temperature have been made using a steady-state combustion installation. Results obtained close to the combustion chamber exit are presented for tests with diesel fuel and with water-in-diesel fuel emulsions of water content up to 15% by volume. The tests are at a combustion pressure of 653 kPa and at two input equivalence ratios (0.871 and 1.085) based on the air-diesel fuel component ratio. Under these operating conditions the soot emission appears to be minimised for the emulsion having a water content of 5% by volume. The magnitudes of temperature and of the concentrations of the various species measured along the axis of the chamber are presented, together with the spatial distributions of these parameters in the form of isotherms and iso-concentration contours within the combustion chamber, for diesel fuel and for the emulsion of optimum water content again at 653 kPa and at the higher input equivalence ratio. A marked reduction in soot formation is observed together with a more even distribution of the vapour equivalence ratio inside the chamber for the burning emulsion. Combustion appears to approach completion more rapidly than in the case of the diesel fuel.