Prediction and measurement of soot particulate formation in a confined diesel fuel spray-flame at 2.1 MPa

A high-pressure combustion system able to provide stable continuous combustion of a liquid fuel spray under closely controlled reproducible steady conditions at pressures approaching those of diesel engine operation is described. The system provides ready access and time for gaseous and particulate samples to be taken for analysis from the exhaust and selected locations inside the flame. Measurements provide data for comparison with available mathematical models. A relatively fast and efficient spray combustion model, including soot formation and oxidation, has been used to compare the predicted values with the results of the experimental tests at a gauge pressure of 2 MPa. The computer programme qualitatively predicted the influence of pressure and input equivalence ratio on the formation and distribution of soot inside the combustion chamber. Increasing peak soot concentration at higher pressure and higher input equivalence ratio was measured and predicted, with off-axis maximum values in an annulus around the axial peak value. Measurements of primary-particle diameters in soot agglomerates sampled at different operating conditions and locations in the spray flame gave number-mean primary-particle diameters in the range 20 to 50 nm. Larger values were measured at the highest chamber pressures and input equivalence ratios. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.