The diesel engine is excellent in economic and thermal efficiency, and is widely used as a power source for industries and automobiles. However, the problem of environmental pollution caused by exhaust gas has recently become serious and the development of alternative energy resources is urgently required due to depletion of fossil fuel. Because biodiesel is similar in properties to light oil, it is being used as fuel for diesel engines by replacing or mixing conventional light oil. As the blending of biodiesel fuel in diesel increases, the emission of harmful substances is decreased as compared with the general diesel fuel, and the supply is increasing. In this study, the effects of biodiesel fuel on engine power and exhaust gas were investigated, and empirical formulas for various NOx and Smoke exhaust gases were derived based on biodiesel blending fuel.

An experimental study was conducted to investigate the atomization characteristics of spray from the effervescent atomizer, which has separated two aerator tubes. The atomization characteristics were examined through the influence of ALR and the changes of atomizer geometry such as nozzle orifice diameter, diffusion angle, mixing chamber volume. PDPA(Phase Doppler Particle Analyzer) was used to evaluate the atomization characteristics. During the experiments, the mass flow rate of liquid was kept constant at 2.8g/s and the mass flow rate of atomizing air was changed from 0.2 to 0.6g/s. Experimental results showed that SMD was not a linear function of ALR. While SMD is very sensitive to the changes of ALR, the changes of atomizer geometry had little effect on droplet mean diameter. As the effervescent atomizer with separated two aerator tubes is insensitive to the changes of atomizer geometry, it is expected that the effervescent atomizer with separated two aerator tubes is capable of requirements of many applications, without the drawbacks of atomization characteristics.