And same as in Fig. 7 (a), the combustion duration of BFO-A after the end of injection is much longer than of BFO-S. So, it can be concluded that BFO-A has the longer flame for a longer time at the stage of after-burning.
4. CONCLUSION
Considering the results of all the examinations for the two fuels, the cause of the heavy wear of the cylinder liners using BFO-A can be guessed in following order.
・The problems of BFO-A are long ignition delay and long after-burning. The latter would be the main problem for the low-speed marine engines.
・The longer flame of BFO-A at the stage of after-burning may be a cause of the heavy wear of the cylinder liners. In detail, as illustrated in Fig. 8, the flame near the cylinder liner will heat the liner surface and damage the thin lubricating oil film at the last stage of combustion duration, when the piston is going down and the upper part of the liner is exposed t o the flame.
References
[1] Shiode, K. et al. : Ignition properties for marine fuels established on the fuel ignition analyzer FIA 100/2. In 22nd CIMAC (1998), pp.369-380.
[2] Takasaki, K. et al. : Influences of fuel spray impingement on combustion in a marine diesel engine. In 21st CIMAC (1995), D-13.
Acknowledgment
We thank the students of the Laboratory of Engine & Combustion (ECO) of the Kyushu University. The experiment using the visual combustion chamber (3.3) is accomplished in collaboration with Japanese Marine Equipment Association under the subsidy of the Nippon Foundation, for which we express our appreciation.
