An investigation of the ignition delay time for oil-water emulsion with different additional more volatile liquid fuels as single droplets is conducted. The measurement is made by the suspended droplets. In the experiments, the ratio of n-dodecane, water and n-heptane (more volatile fuel) is as follows: 6:4:0, 5:4:1, 4:4:2, 3:4:3. The experimental and calculated results show that the ignition delay time decreases with the amount of the more volatile component increasing, and the trend will be smooth for high amount of more volatile component. This result is a very useful method to solve the normal ignition for emulsified oil mixed with a large amount of water in oil in diesel engines. (C) 2001 Elsevier Science Ltd. All rights reserved.