| Summary: | 碩士 === 崑山科技大學 === 機械工程研究所 === 104 === Heat behaviors of a single droplet of castor oil/diesel blends were examined using a suspended-droplet heating device. The castor oil used in the experiment was produced from the cold pressing process of castor seeds. Ethanol has a purity of 99.5%. Diesel employed was petroleum diesel. The heating temperature (environment temperature) and the mixing ratio of castor oil/diesel (or ethanol/diesel) blends were varied in the experiment. The vaporization, expansion, bubbling, ejecting, swelling and microexplosion were recorded by a high-speed video system. Meanwhile, the temperature history and variations of drop size were measured by two K-type thermocouples in the heating process. The results showed that the evaporation rate of the droplet identified by the slope of the d2-law increased with heating temperature. With an increase in heating temperature or blending ratio of castor oil (or ethanol), expansion occurred at a shorter time and the droplet evaporated faster corresponding a shorter droplet lifetime. Microexplosion did not occur for the castor oil/diesel blended fuel. However, when blending ratios of ethanol were 25% and 30%, microexplosion occurred at a heating temperature of 500 oC.
Engine test was conducted for 0% (pure diesel), 5% and 10% castor oil in the castor oil–diesel emulsion. The results showed that instability did not occur during the engine test. It was verified that the use of 5% and 10% castor oil in the castor oil-diesel blends showed similar maximum pressure in the combustion chamber and exhaust gas temperature as compared with petroleum diesel. BSEC (brake specific energy consumption) and BTE (brake thermal efficiency) were slightly decreased and increased, respectively. The addition of castor oil to petroleum diesel led to a slight increase in NOx emission and slight decrease in CO2 emission as well as smoke opacity. Furthermore, the 5% and 10% blending ratios of castor oil in the castor oil/diesel emulsions were found to reduce PM2.5 by 20 and 23%, respectively, compared to the petroleum diesel. Similar results were observed for diesel engine test using ethanol/diesel blends as fuels, except that the NOx emission slightly reduced due to the decreased gas temperature caused by higher latent heat of vaporization of ethanol.
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