Validation of heatup effect on ethanol spray with local-contact microwave-heating injector by using image analysis

Abstract

Spray method is used for liquid vaporization. Especially in the internal combustion engine, ICE, the spray specifications are important to improve the efficiency and to reduce the emission amount. The main purpose of spray is vaporization but the necessary heat transfer amount is not enough at the cold-start of ICE. In the use of ethanol, an important alternative and sustainable fuel from biomass, this cold-start problem is much more serious because of the high latent heat and low heating value. The Local-contact Microwave-heating Injector, LMI, was designed and tested in this paper to solve the ethanol cold-start problem. The evaluation parameters of the LMI spray were droplet diameter distribution, Sauter Mean Diameter, SMD, and droplet velocity distribution. As a laser diffraction method (approximately 4mm spot-diameter He-Ne laser) was used to measure the droplet diameter distribution but could not measure other parameters, direct photographs with a high speed camera (512pix x 512pix, color, 12bit for each three colors, 30kfps, 87.7μm in spatial resolution) was used to measure the spray structure change and droplet velocity distribution. A threshold evaluation was important to distinguish the droplets in spray. A watershed method was used to divide exceptionally large droplets. As a result, the microwave heating can improve the atomization.