ROTOR SEALS FOR GAS-TURBINE ENGINES FABRICATED
– BN HIGH-TEMPERATURE COMPOSITE MATERIALS
I. Yu. Kelina,
N. I. Ershova,
A. V. Arakcheev,
and E. N. Chasovskoi
Translated from Novye Ogneupory, No. 2, pp. 38 – 43, February, 2004.
The development of rotor seals for gas-turbine engines is reported using Si
– BN-based composite materi
als molded by hot-pressing technology. The mechanical and thermophysical properties of the newly-deve
loped materials are determined and compared with results of a thermal stress analysis by numerical simulation
method. Potential use of rotor seals of different design, in particular, multilayer components, for practical ap
plications is discussed.
To prevent rotor seizure in gas-turbine engines (GTE),
thermal gaps are provided between rotating and stationary
parts; when appropriate, the gap can be narrowed to increase
the engine efficiency. However, decreasing the gap width in-
curs the risk of damaging the rotor blading because of acci-
dental contact between the turbine rotor and the rim. To pre-
vent this, various seal assemblies have been proposed.
In practice, seal assemblies are in service that admit con-
tact between the rotor and the static shroud using cellular ele-
ments and easily wearable materials that are mounted in the
form of sectors, coatings, or two-layer metal-ceramic inserts
. The first layer in these inserts provides strength, and the
second, soft layer provides the property of wearability; how
ever, their operating temperature should not exceed the melt
ing point of the metal and the temperature of the onset of oxi
dation (about 1000°C). Rather stringent demands are placed
on the rotor seals (RS) such as thermal stability (up to
1300°C), erosion resistance to the gas stream, resistance to
temperature fluctuations, easy wear on contact with the rotor
blade, and stability of material strength characteristics.
The Kyocera Corporation (Japan) has developed ceramic
silicon nitride materials SN281 and SN282 exhibiting high
temperature strength and resistance to oxidation that can be
used in GTE parts and assemblies, including rotor seals .
The ceramic shroud for CGT302-type engine made from
SN282 material can be equipped with a wearable insert made
of soft, porous silicon carbide (Table 1, Fig. 1). This appli
ance makes it possible to narrow the thermal gap width to
0.1 mm and thus to improve the efficiency of operation.
With this in mind, promising for that purpose are materi
als in the Si
– BN system that combine advantageous
properties, viz. high strength, thermal stability, and good
machinability [3, 4].
In , a ceramic material was described specifically in-
tended for use in GTE rotor seals. The Si
– BN-based ce-
ramic was prepared by reaction sintering; it exhibits a high
resistance to oxidation. Because of rather high porosity, me-
chanical properties of this material are modest: the bending
strength does not exceed 195 MPa. Still, the material can
find good use as a wearable insert in structures operating un-
der moderate stress conditions.
Our goal in this study was to develop a material capable
of operating at high mechanical and thermal loadings. In de
signing a multilayer ceramic in the Si
– BN system, the
complex built-up construction for rotor seal can be replaced
by a one-piece ceramic component of variable composition.
Refractories and Industrial Ceramics Vol. 45, No. 3, 2004
1083-4877/04/4503-0185 © 2004 Plenum Publishing Corporation
Tekhnologiya Research and Production Enterprise, Obninsk,
Kaluga Region, Russia.
TABLE 1. Typical Characteristics of the Wearable Material
Bending strength, MPa,
at the temperarure, °C:
25 96 738
1000 101 635
Temperature linear expansion
temperarure, °C (about):
400 2.0 2.5
800 2.5 2.9
1000 2.7 2.9
1200 2.9 3.0