A Study of Some Combustion Characteristics of Gas Oil/Water Emulsions in a Swirl Chamber Diesel Engine 892056

A study was conducted on a Ricardo E6 variable compression swirl chamber diesel engine on the influence of water-in-gas oil emulsions on the combustion process. Various percentages of water were considered ranging from 2% to 10% by volume. The effect of increasing the water percentage on the ignition delay, maximum rate of pressure rise, maximum combustion pressure and heat release characteristics was experimentally investigated. Various design and operational parameters were considered viz: equivalence ratio, rotational speed, injection timing and compression ratio. The results were compared with those obtained with pure gas oil. For water percentages up to 6%, the ignition delay and rate of pressure rise were found to increase significantly. However, greater water percentages reduced the delay and rate of pressure rise. The equivalence ratio, speed, injection timing and compression ratio were found to be influential factors regarding the delay and rate of pressure rise when operating with emulsified fuel. The rate of heat release increases with higher equivalence ratios and greater water percentage in the emulsion.

Correlations were developed to predict the ignition delay, peak rate of pressure rise and maximum combustion pressure; they were in the form:

The pressure rise pattern with emulsified fuel exhibited a three-stage combustion. The first is premixed whilst the latter two are diffusive combustion.