| 摘要 |
PURPOSE:To easily prevent local howling produced by being excited by Karman vortex generated at the trailing edge of a propeller blade by making cuts at the trailing edge of the propeller blade projecting from a boss, thereby changing frequency of local vibration of the propeller blade. CONSTITUTION:At a trailing edge of a propeller blade 1, a cut 7 and a cut 8 are formed so that a local part 9 is interposed in between. When the blade is made of a flat plate, frequency (fv) of the local vibration of the local part 9 is approximately halved by forming a distance (a) a length (b) of the cuts 7 and 8 with a same value. Even when the blade is not a plane but is of a wing profile where the distance (a) and the length (b) is not equal, the local vibration frequency (fv) of the local part 9 can be sufficiently lowered. The distance (a) and the length (b) are determined based on the calculation results of vibration modes of the blade 1. Thus, local vibration frequency (fv) is lowered to be different from the vibration frequency (fk) of the Karman vortex generated at the local part 9 so that the howling can be securely prevented from being produced.
|
