Project Title:

HYBRID FLOATING BRUSH SEAL FEASIBILITY STUDY FOR THE HIGH TEMPERATURE ADVANCED GAS TURBINE APPLICATIONS

94-1	01.01	0051		

HYBRID FLOATING BRUSH SEAL FEASIBILITY STUDY FOR THE HIGH 
TEMPERATURE ADVANCED GAS TURBINE APPLICATIONS

Abstract:

The present proposal offers the possibility of a technological 
jump in the use of Brush Seals, which in themselves represent a 
novel technology presently being incorporated in the new 
generation of jet engines. Turbine efficiency is strongly 
associated with the blade tip clearance, and it can decrease 
significantly through the unloading of the blade due to leakage 
over its tip, and subsequent increase in the flow area over the 
tip. The most basic cause resides with the radial displacements 
of the rotor and the case when the clearance generally becomes 
larger than the desired operating conditions.
A significant contribution towards the solution of the problem 
has been the introduction of the brush seals. These types of 
seals provide a principally compliant buffer between the blades 
and the case, or at compressor and turbine interstages. While 
these seals work relatively well, the brush wear at the 
rotor/brush interface as well as its overheating seem to still be 
a major obstacle to long term reliability. As the problem stems 
in part from the large relative velocity and heat flux production 
at the interface, the solution proposed here, the hybrid Floating 
Brush Seal aims at reducing considerably (80%-90%) the relative 
velocity thus completely eliminating this class of problems. To 
further reduce overheating, be that from friction at the 
interface, or from the extremely hot gases coming from the 
combustor, a new procedure of combined film and transpiration 
cooling is also incorporated within this new type of floating 
brush.

Brush seal development is a specific technology that has been 
identified by Government organizations(Air Force, Army), as well 
as by private industry jet engine manufacturers (General 
Electric, Textron Lycoming, Allied Signals, Pratt & Whitney, 
Rolls-Royce) and seal manufacturers (Technetics, EG&G Sealol, 
Cross Mfg), as very promising in the area of enhanced engine 
primary and secondary stream management and SFC. Successful 
conclusion of the undertaking proposed here will offer a new 
class of brush seal devoid of the problems exhibited by the 
present generation of brush seal. Such a brush could be used with 
newly found reliability not only in the turbine and compressor 
interstages but also as very efficient and reliable blade tip 
seals. Its added transpiration cooling feature will possibly make 
this brush usable even in the first stage of the high pressure 
turbine.

Key Words

B&C Engineering Associates, Inc.
P.O. Box 2384
Akron, OH 44309