Brush Seal Performance and Durability Issues Based on T-700 Engine Test Results

R C Hendricks

doi:10.1155/s1023621x95000029

Abstract

The integrity and performance of brush seals have been established. Severe bench and engine tests have shown high initial wear or rub-in rates, material smearing at the interface, and bristle and rub-runner wear, but the brush seals did not fail. Short-duration (46 hr) experimental T-700 engine testing of the compressor discharge seal established over 1-percent engine performance gain (brush versus labyrinth). Long-term gains were established only as leakage comparisons, with the brush at least 20 percent better at controlling leakage. Long-term materials issues, such as wear and ultimately seal life, remain to be resolved. Future laeeds are cited for materials and analysis tools that account for heat generation, thermomechanical behavior, and tribological pairing to enable original equipment manufacturers to design high-temperature, high-surface-speed seals with confidence.

Highlights

What is not understood is the nature of the interface
that has a rub model for bristle tip and rotor surface wear e. that has a knowledge base including the tribological pairing of the interface material
the secondary air systems associated with seal leakages

Summary

Printed in the United States of America

Brush Seal Performance and Durability Issues Based on 1"-700 Engine "rest Results. National Aeronautics and Space Administration, Lewis Research Center, Cleveland, OH 44135. Short-duration (46 hr) experimental T-700 engine testing of the compressor discharge seal established over 1-percent engine performance gain (brush versus labyrinth). In a rather harsh test at low surface speeds, brush seals were subjected to hard rubs by engaging the bristles into a 40-gear-tooth rotor (Fig. 1). HENDRICKS of the data and short engine hours (46 hr), experimental engine specific fuel consumption for the brush seal was reduced over percent relative to the labyrinth seal performance (Fig. 6) These high gains in performance may be partially lost as the brush wears line to line within the rotordynamic and static eccentricity envelope. It is important that the seal perform as predicted Both labyrinth and brush seals, through improper design or installation, have caused shaft failures through excessive rubbing contact at their respective interfaces. D’i.am,J,S,Tnk’Besntt’’li/’’i/-.-0l.0L=--12.833diam u.n iss,e brush forced off rotor past labyrinth tooth (no rotation) ed(]e iG.-;--I

Experimental testbed engine horsepower

SUMMARY AND FUTURE NEEDS

Upper wear band Lower wear band