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摘要
Microexplosion and ignition characteristics of biodiesel/ethanol blends were studied by suspending single droplets on fibers in a tubular oven at different ambient conditions. The range of ethanol content in initial fuel, as an important parameter, was changed from 0% to 100%.Heating temperature and gas flow were also reference variables, which were respectively changed from 300 degrees C to 500 degrees C and from 0 L/min to 10 L/min. Behaviors of droplet microexplosion and ignition were recorded by high speed camera. Temporal variation of droplet size, time to microexplosion and ignition delay time were all analyzed for every cases. The results showed that microexplosion could be found in most cases due to high volatility distinction of biodiesel and ethanol and be expedited and intensified at fuel for nearly equivalent volume mixing, or at enough high temperature and in a certain gas flow. However, ignition was achieved only in some situations which biodiesel content in initial fuel and temperature was relatively high and gas flow rate was moderate. Further, under the condition that the temperature and flow rate remain unchanged, when the ethanol content reached 50%, the micro-explosion intensity which was named the normalized diameter reaches the maximum (1.3). At the same time, the delay time of micro explosion is also reduced to the minimum (0.23 s). Under the condition that the ratio and flow rate remained the same, when the ambient temperature rose to 400 degrees C, the micro-explosion intensity reached the maximum. At this time, the normalized diameter of the mixed droplets approached 1.5. Under the condition that the temperature and ratio remained the same, when the flow rate was 5 L/min, the ignition delay time was the lowest (about 2.8 s), when the flow rate was 10 L/min, the micro explosion intensity was the largest, and the normalized diameter reached 1.8. Beyond this, it was found that raising the ratio of ethanol in the blended fuel could increase the burning rate but lower the ignitability, and the ignition delay time could be shortened when the droplet exhibited microexplosion and fuel of near equi-volume blends, experiencing the most violent microexplosion, optimized the improvement, which could be found more obviously at high temperature and high speed airflow.
- 出版日期2019-10
- 单位中国科学技术大学
