The use of renewable fuels in fueling of IC engines grows rapidly in all over the world, as reaction to attempts to reduce the green house gas emissions. The biodiesel fuels are made from plant or animal feed-stock trough on esterification process; fatty acid methyl ester resulting as we called generic “biodiesel’. There are some major differences between the biodiesel and diesel fuel physico-chemically characteristics, with immediate influence on diesel engine’s energetic efficiency, fuel consumption, pollutant emissions, reliability etc. New researches show that it is possible to eliminate those differences (partially or totally) using an external energy conditioning process. Besides of the advantages of this process, a major concern regarding about the biodiesel oxidation stability is occurring. The biodiesel is very sensitive to oxidation and thermal degradation. Oxidation of biodiesel can lead to formation of corrosive acids and gum deposits that reduce diesel engine reliability. The paper presents the experimental results about the influences of ultrasonic irradiation on biodiesel blends oxidation stability. An experimental apparatus was developed and the ultrasonic irradiation process was realized using low-power ultrasonic emitters. To create the cavitation phenomenon in the ultrasonic irradiation of biodiesel blends for the present experiment, we used a small volume of biofuel for conditioning (V BD =300 ml) and an ultrasonic horn that produces 35 W/L,PZT type, at 35 kHz frequency emissions, which was applied continuously. The equipment was manufactured from an ultrasonic bath Sonorex Bandelin RK 11 type. Measurements of physical properties considered in the experiments were carried out after duration of 600 seconds ultrasonic irradiation. The Rancimat Oxidation Stability and the Filter Blocking Tendency methods and procedures were use. The biodiesel blends ultrasonic irradiation has as secondary effect the formation of oxidation products, whose quantity in mixtures rises with increasing volume of methyl ester in blends. If the induction period (IP) value of non-irradiated blends ranged between 25.1 and 8.8 hours (for B25 respectively B100) and for ultrasound irradiation these values ​​are 24.8 and 7.8 hours (for B25Us_irr and B100Us_irr respectively). The biodiesel blends ultrasonic irradiation process has as effect a decrease of the induction period, indicating worsening the storage properties of biodiesel. An increasing of 13.04 % in insoluble polymers and as result, a reducing in long-term storage properties was measured for B100 RME blends. The obtained results show that the external energy conditioning process is feasible only for locally and in real time application in fueling of diesel engines.

ultrasonic; irradiation; biodiesel; oxidation stability; storage properties.

Presentation: oral