چكيده به لاتين
Heavy fuel oil are one of the most widely used fossil fuels. The researchers are looking for new ways to increase the combustion efficiency and reduce the pollution using this kind of fuel. One way to solve these two basic problems is replacing the heavy fuel oil with the emulsion fuels. The micro explosion phenomenon in the combustion process of this type of fuel leads to a significant increase in the spray quality and subsequently increases the combustion efficiency, decreases the fuel consumption, and reduces the emission of pollutants such as nitrogen oxide and particulate matter. In this study, the water in heavy fuel oil emulsion fuels containing 5, 10, and 15 percent by volume of water were prepared without using surfactants under ultrasound irradiation. After producing the fuels, the stability of the fuels and the distribution of water droplets as dispersed phase in the heavy fuel oil as the continuous phase were investigated. Some physico-chemical properties of the fuels including viscosity, density, heating value, and the water content in the fuel structure were examined. Then, the microscopic structure of the fuel oil and the emulsion fuels were compared with 500x and 1000x magnification. Finally, the output spray from the pressure-swirl injector for the heavy fuel oil and the micro explosion phenomenon for the emulsion fuels were recorded using high speed imaging method at different pressures of 10, 15, 20, and 25 bar and different temperatures of 60, 70, 80, 90, 100, and 110 °C. By comparing these images, the breakup length of the fuel spray at each temperature and pressure was obtained by image processing using Matlab R2015a software. The results showed that the water droplet diameter in 5% water in heavy fuel oil emulsion is smaller in comparison with 10% and 15% water in heavy fuel oil emulsions. Besides, more uniform distribution of water droplets was observed for 5% water in heavy fuel oil emulsion which results in better stability of the emulsion fuel with 5% comparing the other emulsion fuels. It was found that in the majority of the working points of the combustion system, the best atomization quality and the shortest separation length belong to 5% water in the heavy fuel oil emulsion fuel, 10% water in the heavy fuel oil emulsion fuel, 15% water in the heavy fuel oil emulsion fuel, and the heavy fuel oil, respectively. Based on the results, it was also found that the difference in the breakup length is high at low temperatures. This difference also decreases by increasing the temperature.
