2011 年 6 巻 4 号 p. 651-661
An attempt is made to clarify the flow instabilities downstream of inlet guide vanes by conducting experiments and performing a numerical simulation. The onset condition including the cell number and oscillating characteristics of the unsteady flow is discussed based on the measured pressure fluctuation. The propagating angular velocity ratio of the instability for various values of r3/r2 (ratio of the radius of the trailing edge of the vanes to the radius of the outlet of the device) is presented as a function of vane angle β2. The phenomenon taking place downstream of the inlet guide vanes is demonstrated to be of a different type from the rotating stall of the blades, where the amplitude of the flow oscillation depends on the number of cells and the chord length. In addition, applying the slope angle on the lower disc is found to be effective for controlling the flow instabilities.