Recently, the improvement of fuel economy and the reduction of exhaust smoke and NO have been successfully achieved by supplying diesel engines with emulsified diesel oil with water particles.
In the present paper, the difference between the combustion of injected emulsion and that of diesel oil spray is clarified by means of taking high-speed and color photographs of the flames in engine cylinder and in hot air stream. As the results, the two kinds of fuels show different combustion behaviour each other in the growth of initial flame and in the termination of overall combustion in the cylinder. Then, suitable combustion chamber design for the use of emulsified fuel is discussed on the basis of experimental data for various distributions of spray in various kinds of piston cavities. Some methods of clearing troubles caused by emulsified fuel are also discussed on the basis of performance data on a practical high-speed open-chamber diesel engine.