DesignClinic

Design of an Adjustable Impeller Eye Labyrinth Seal

Dresser-Rand

Dresser-Rand

2013-2014: In collaboration with Dresser-Rand this team designed an impeller eye labyrinth seal that allows clearance to be adjusted without disassembling the centrifugal compressor that houses the seal.

Leakage across the impeller eye seal is a critical factor influencing the performance of a centrifugal compressor. Performance is maximized if the labyrinth seal clearance is minimized, but the clearance must be large enough to ensure that no rubbing occurs due to vibrations in the rotor system, particularly during startup. To accomplish both purposes it is desirable to expand the inner diameter of the seal as the impeller goes through critical speed and decrease the inner diameter of the seal when running at nominal speed. After extensive research the team developed fourteen potential adjustable mechanisms and nine control strategies. A weighted matrix was created to rank the ideas with respect to sensitivity to incrementing, ease of assembly, compatibility with current compressor design, complexity, ease of fabrication, and cost.

The final design, based on controlled thermal expansion, was analyzed for feasibility and then fabricated and tested under conditions that mimicked the actual implementation. In addition to a comprehensive final report, the team delivered to Dresser-Rand drawings and specifications for the final design, a physical prototype, and a list of additional recommended tests.