The purpose of this work is to investigate the spray-atomization, combustion and emissions characteristics of biodiesel-bioethanol (BE) and biodiesel-diesel (BD) blended fuels compared with an undiluted biodiesel fuel. For studying the overall spray characteristics, the spray tip penetration, spray cone angle were analyzed from the spray images, and droplet size and distribution were analyzed from the droplet measuring system. In addition, the combustion and exhaust emissions characteristics including the nano-size particle number and size distribution of particulate matter were studied using the direct injection diesel engine with a single cylinder. In this investigation, it revealed that BE and BD blended fuels have slightly higher spray tip penetration and wider spray cone angle due to the reduction of fuel properties such as fuel density and kinematic viscosity. Fuel droplet sizes of blended fuels were distributed in the region of the lower diameter size, compared to biodiesel fuel. It can be said that the reduced fuel viscosity and surface tension of blended fuels affect the atomization performance of biodiesel fuel. The experimental results of spray characteristics were compared with the predicted results through the numerical method by the KIVA-3V. On the other hand, BD blended fuel has a similar combustion and emission characteristics compared with an undiluted biodiesel fuel. In case of BE blended fuel, the ignition delay becomes longer and the rate of heat release becomes high. In the case of exhaust emission characteristics of BE blended fuel, it has lower soot emission, contrary to the almost same nitrogen oxides, hydrocarbon, and carbon monoxide. In the analysis of particle size and number distribution, the number and size distribution of B100 and BD20 fuels have a similar pattern and value. However, BE blended fuel has a lowest particle number in the region of nuclei mode. Moreover, the increase of the injection pressure affects the increase of the smaller size particle of BE blended fuel.

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