Abstract
Nowadays, low-speed two-stroke cycle diesel engines are used for marine transportation because of their high thermal efficiency, thus utilizing cheap fuel, of course good from the economical viewpoint. However, some marine diesel engines have been damaged when low grade bunker oil is used. Here, ignitability and combustibility of 107 samples of bunker fuel oil was evaluated. Visualization via a high-speed color video camera was conducted with signals of photo-sensors, rate of heat release and analysis of fuel properties. It was found that ignition delay and after-burning do differ, fuel to fuel. By changing the gas temperature at injection time, the degree of ignitability for the sample fuel could be clearly judged. Short or long after-burning was shown in spite of the same ignition delay. In some fuel oils, the combustion was promoted after ignition, even if the ignition delay was long. Some fuel oils, those with low sulfur content of less than 1.0%, and a higher nitrogen content with a CCAI value between 840 and 860, presented both worse ignitability and worse combustibility. However, on the other hand, some fuel oils showed good combustibility, even in these properties. Therefore, this equipment will be a strong tool to judge the fuel quality of combustion before bunkering fuel oil.
