Experimental Study On Evaporation And Combustion Characteristics Of N-butanol-biodiesel Droplets

The boiling point of biodiesel is relatively high,which is not conducive to the gasification of fuel in the process of spray evaporation.The addition of butanol to the biodiesel can improve the gasification capacity of the biodiesel during the evaporation and combustion process by puffing and micro-explosion in the process of the evaporation.In order to study the intrinsic mechanism of the evaporation and combustion of butanol-biodiesel,the butanol and biodiesel were formulated with different proportions to find out pure evaporation,combustion and puffing characteristics.First,the test device of the single droplet is designed and the uncertainty of the butanol content and the square of the droplet diameter in the process of producing the droplet is studied to ensure the accuracy of the test data.Then,the original image is acquired by the high-speed camera and the image processing program based on the matlab software is prepared to process the original electronic image of the single droplet.The normalized square of the droplet diameter ?the similarity degree and deformation degree can be got.Finally,the pure evaporation?evaporation and combustion and puffing characteristics of butanol-biodiesel droplets are studied in low and high temperature environment under atmospheric pressure.The results of the pure vaporization show that the bubble formation,expansion and fragmentation can occur in the butanol-biodiesel droplet evaporation process.The evaporation rate of the droplets under the atmospheric pressure was found to be improved to some extent with the increase of the butanol content and the ambient temperature.With the increase of the initial diameter of the droplets,the evaporation rate decreased.At the temperature of the pure evaporation,the similarity of BUT25 and BUT50 showed a wavy shape,and the similarity of BUT75 showed a comb-like shape.The fluctuating evaporation stage contained multiple cycle process containing bubbles formation?growth?breakage and recovery.Then the similarity of the BUT25,BUT50 droplet could be wavy,but in regard to the BUT75 droplets the bubble expansion is not sufficient,resulting in droplets recovering quickly and each cycle process being easy to return to a stable stateAt the ambient temperature of 973 K,the results show that the ignition time of the butanol-biodiesel droplets is delayed with the increase of butanol content when the initial diameter of droplets is 1.17 mm.At the ambient temperature of 1073 K,the ignition delay period of the butanol-biodiesel droplets decreases with the increase of the butanol content when the initial diameter of the droplets is 1.17 mm,and the secondary ignition time increases with the increase of the butanol content.The larger the initial diameter of the droplets is,the longer the ignition time is.When the diameter increases to a certain extent,the ignition time remains the same.