Evaluation of Atomization Timing and Optimal Water Content for an Emulsified Fuel Droplet 2018-32-0059
The emulsified fuel means that it is mixed fuel with water and stabilized by surfactant. The difference of boiling points between fuel and water occur the secondary atomization during heating process. The water content strongly influence on the timing of secondary atomization(1). However, the water content is determined empirically. It means that it is the doubtful of compatibility fuel and a combustor. Then the emulsified fuel is needed the engineering evaluation (not empirically) to take advantage of sure secondary atomization.
This research focuses on the timing and behavior of secondary atomization with an emulsified fuel droplet and the proposal of engineering evaluation. Moreover, we propose novel test method without the suspending wire to avoid heat transfer from itself. Namely, the novel point is heating process by floating in the high temperature silicone oil. This method can reveal the atomization behavior of a fuel droplet similar to the spray combustion.
The measured data are waiting time of atomization and direct photos during heating process. The waiting time is fitted by Weibull plots which is a statistical treatment of reliability engineering. The inclination of Weibull plots means the timing of secondary atomization. This is the engineering evaluation on this research.
The experimental results show the optimal water content of n-Hexadecane is 23%. If the fuel droplets have different timing of the secondary atomization, it is hard to control the combustion, for example, ignition delay, rate of heat release and so on. The typical experimental results show the inclination of Weibull plots converge to a point. This is mean that even various sizes of fuel droplets occur secondary atomization in the similar timing during heating process. The optimal water content of Bio diesel fuel is wide range under 30%. We propose the statistical evaluation to determine the optimal water content for practical emulsified fuel use.
Junichi Aoki, Junya Tanaka
SAE/JSAE Small Engine Technology Conference