廃食油バイオディーゼル燃料の直噴式ディーゼル機関適用化研究

―第3報噴霧燃焼機構および火炎内すす生成機構の基礎解析

抄録

The combustion and emission characteristics for two waste cooking oils were investigated in detail. One fuel was the methyl esters in waste cooking oil. This fuel is in routine use in Kyoto City for a garbage collection vehicle with DI diesel engine (B100) and a city bus (B20; 80% by volume gas oil is mixed into B100) as an altemative fuel for gas oil. The other is fuel created by removing impurities from raw waste cooking oils. In order to improve the fuel properties, kerosene is mixed 70% by volume in this fuel. The mixed fuel (i-BDF) is used in several trucks in Wakayama City.
In the experiments, the soot formation process inside the flame was focused using an optical measurement method. A rapid compression and expansion machine (RCEM) was used to simulate the DI diesel engine combustion process. Flame characteristics were investigated by the two-color method, and details of the soot formation process were detected using laser-induced incandescence (LII) . Results showed that the high flame temperature region in the BDF case existed throughout the whole flame, but existed only in the central part of the flame in the gas oil case. The gas oil case showed a high level of LII signal intensity, but when the combustion process progressed, the LII signal intensity of biodiesel fuels noticeably decreased.