Flame Structure and Combustion Characteristics in Diesel Combustion Fueled with Bio-diesel 2004-01-0084

The Flame structure and combustion characteristics for two waste-cooking oils were investigated in detail. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is the fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City.

In the experiments, the used fuels were gas oil, i-BDF, B100 and B20. Spray characteristics and basic combustion properties were measured inside a rapid compression and an expansion machine (RCEM). And, the combustion performance including the exhaust-gas emissions were revealed in a single-cylinder, direct injection diesel engine with toroidal type chamber, 4-hole nozzle and bosch type injection system.

The spray characteristics were measured by shadow-photography. It is found that the spray tip penetration increases and the spray angle decreases for waste-cooking oils. The flame structure was measured by direct-photography. As a result, flame luminosities in waste-cooking oils are relatively low; in particular, soot formation in the combustion flame is derived to be decreased in the case of B100. The engine performance and exhaust emissions were investigated at 3600rpm in a wide range of loads. Then the following results were obtained. The ignition delay of the waste-cooking oil is shorter. NOx emissions are similar for all fuels. PM emissions are lower with B100 compared to another fuels in the whole engine operating range.