Reduction of NO_x, smoke and brake specific fuel consumption with optimal injection timing and emulsion ratio of water-emulsified diesel

This paper reports the test results of a diesel engine at different engine speeds, injection timings and emulsion ratios with water-emulsified fuel. Results show that both NO_x and smoke may be reduced significantly at the same brake specific fuel consumption (b.s.f.c.) at high engine speeds above 1400 r/min. At low engine speeds below 1000 r/min NO_x may be reduced slightly with minor penalty in the b.s.f.c. with no overall gain in use of emulsion fuel. In the tested range of water-oil ratio by volume of 0-40 there was no significant deterioration in the HC and CO emissions and the combustion stability in terms of cyclic variations of the peak cylinder pressure. It may be necessary to employ accurate electronic control of the injection timing as a function of load and speed to maintain the optimum operating condition with emulsion fuel.