부산대학교 도서관

The present research investigated effect of backflow prevention plate on unsteady characteristics of a swirling jet. The experimental facility was designed to control the swirl ratio adjusted by varying the angle of the guide vanes. For visualization, the swirling jet with a smoke was illuminated by a laser sheet. The circumferential velocities were measured by hot wire probes. The experimental results show that the swirling jet for the 0 degree of the guide vanes flows along the outside wall. When the angle of guide vanes is enlarged, the flow was emitted in the axial direction. When the guide vane angle is 30 degrees, backflow occurs toward the center of the jet outlet. In order to prevent the backflow, a cylinder and a disk are attached to the jet outlet. When the result was compared, the difference in the peak of the FFT analysis was seen by attaching the cylinder and the plate. By the FFT, one peak with the three rotating cells was observed with and without the cylinder. On the other hand, one peak with the four rotating cells was observed with cylinder and plate. Flow fluctuation occurs by backflow to the jet outlet at 30 degrees of the guide vane angle.