Duration of Combustion in a Commercial Diesel Engine 390137
NOT only does a high-cetane diesel fuel start to burn earlier in the cycle due to its shorter ignition-lag period, but it continues to burn longer during the expansion stroke than does a low-cetane fuel, the authors announce. This and other findings, they explain, are the results of an investigation of the effect of fuel quality and injection advance angle on ignition lag and combustion duration in a 4-cycle high-turbulence diesel engine. The same photo-electric combustion indicator, developed at the University of Wisconsin, was used, they point out, as was described previously before the Society, with the exception of several improvements. Combustion characteristics of 27 different fuels were determined by studying the oscillograms for more than 5000 engine cycles obtained at a film speed of 60 fps.
From dynamometer tests run both on 1-cyl and 6-cyl 4-cycle diesel engines, fuel rates were obtained from six different fuels varying in cetane number from 25 to 87.
A comparison of the test data from an open-head engine with that obtained from the separate-chamber type shows that the high turbulence in the latter engine had no direct effect on ignition lag, they report, although it is noted that greater heat losses due to turbulence caused slight changes in the shape of the ignition-lag curves.