Atomization and combustion of vegetable and mineral oil blends

The increase of the energy consumption for the next years leads to look for alternative fuels having a low environmental impact with particular regard to particulate emissions. Vegetable oils are particularly interesting as fuels that can be used in energy production and cogeneration systems. The combustion performances of a typical vegetable oil such as the rapeseed oil and its blend with heavy oil were investigated in a 100 kW pilot combustion plant. Physical characteristics such as miscibility, thermal stability and viscosity of the fuels and of the blend were preliminary measured. The sprays characteristics of rapeseed oil, heavy fuel oil and diesel oil were investigated by means of laser-based optical techniques according to the Lorenz-Mie theory in order to get information on the mean size of the droplets in the spray and on the spray configurations. Moreover, the flame structure of the different fuel and blends were studied in regard to particulate production. Both optical and sampling analyses were used as diagnostic tools. The rapeseed oil showed to be a very effective substitute or additive of mineral oils given its lower tendency to produce particulate.