Flow induced vibration within centrifugal gas compressors

The purpose of this study is to determine the effects of aerodynamically forced disturbances occurring in the impeller channels of centrifugal gas compressors. These disturbances are induced at the diffuser inlet when the tips of the impeller blades pass in front of the tips of the diffuser vanes, thereafter propagating into the impeller channels. In these channels, the disturbance waves can be amplified enough to cause severe structural damage to the walls.

Theory was developed and coded into a Fortran program that gave the steady and unsteady (disturbance) properties at all points within the impeller channel above the inducer region and in the region between the impeller and the diffuser.

The results revealed that keeping all design variables constant and changing only the ratio of diffuser vanes to impeller blades, greatly influenced the amplitude of the disturbances within the impeller channels. Consequently, with the program developed here, the optimum ratio of diffuser vanes to impeller blades can be determined without testing. This is one major finding, but it is obvious that the program will give valuable insight into many compressor design changes.