Abstract
In this study, the effect of dielectric heating of microwave on polarized molecule liquid was used and the microwave was transported by a coaxial cable to the injector tip, to heat the fuel up locally just before it was injected. Microwave generator was controlled with an inverter and power source was AC100V, 60Hz. The output power of microwave generator could be altered from 20W to 120W and the fuel temperature on the tip was controlled from room temperature (20C-deg, 293K) to 80C-deg (353K). The temperature was measured with K-type thermocouple (sheath diameter of 1.0mm). The analyzed spray characteristics were 1) Sauter mean diameter (SMD), 2) spray cone angle, 3) spray width, and 4) wavelength. The SMD was measured with a laser diffraction method. The spray cone angle and the spray width were measured with color CMOS camera (150M pix). The wavelength was measured by using a high-speed camera (10,000 frames per sec.). The experimental results were compared with a Rayleigh analysis.
In the LMI, the injector body temperature was almost room temperature even though the fuel temperature at the injector tip was over 353K. The SMD of spray was almost 0.07mm and was decreased with the fuel temperature increase under the boiling point, and at the boiling point, the SMD was very small with the values about 0.02mm. On the other hand, the spray cone angle at 1mm from injection hole have a little increase, and the spray width that was measured at the point with a distance from the injector tip of 40mm were also increased during the variation of fuel temperature less than boiling point. The wavelength was less than 0.9mm and was decreased with the increasing fuel temperature, which was shown in the theoretical analysis result. It is concluded that and the increase of fuel temperature has the desire effects on the properties of spray and atomization, and the experimental results of spray wavelength have a similar pattern with the theoretical analysis results.
Keywords: Local-contact Microwave-heating Injector, Atomization, Spray, Alternative fuel, fuel heating.