燃气涡轮工程手册 Gas Turbine Engineering Handbook 2(96)

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Foreign material within the seal results in increased shearing forces between the primary and matingrings， causing overheating of theseal components， leading to o-ring extrusion or some other mechanical form of seal failure. The major areas from which gas seals contamination occurs are:
.  Process gas leakages from the inboard or high-pressure side of the seal.

.  Bearing lubrication oil from the outboard or low-pressure side of the seal.

.  The seal gas injected into the seal being contaminated upstream of the injection.

Contamination from Process Gas. .ontamination from process gas can occurwhen there is insufficient supply of sealing gas into theseal， allowing process gas to come into direct contact with the seal ring faces.
.ontaminants existing within the process gas can then damage the seal.
Contamination from Bearing .ubrication .il. A barrier seal is required onthe outboard side of the dry gasseal， between the gas seal and the compressor bearing. The primary function of the barrierseal， typicallybuffered with air or nitrogen， is to prohibit the flow of bearing lubrication oil into the gas seal. .ontamination of the dry gas seal from lube oil can occur when the barrier seal fails to function as intended.
Contamination from Seal Gas Supply. .ontamination from the seal gas supply occurs when the sealing gas is not properly treated upstream of the dry gas seal. Gas seal manufacturers have stringent requirements forseal gas quality. Typically， the sealing gas must be dry and filtered of particles 3 micron and larger. Filters are normally provided in the gas seal system to meet this requirement.
.ry gas seals operate under extremely tight tolerances， which demand thatspecial care be taken in the design of the gas seal environment， and in the operation of the compressor and gas seal system. While the threat of seal degradation and reduced seal life due to outside influencesisreal， the detrimental effects of these factors can be minimized.
The replacement of mechanical seals by dry gas seals must be closely examined. There have been many cases where the replacement has caused the compressor to operate in an unstable manner. This is due to the fact that removal of the mechanical seal causes a change in the damping of the rotor and can cause the rotor to operate closer to its critical speed.
Bibliography
Abramovitz，S.， ""Fluid FilmBearings， Fundamentals and .esign.riteria， andPitfalls，'' Proceedings of the 6thTurbomachinerySymposium， .ecember1977， pp. 189.204.
.hilds，..W.， and.ance，J.M.， ""Annular Gas Seals and Rotordynamics of
.ompressors and Turbines'' Proceedings of the 26th Turbomachinery Sympo-sium， Texas A&MUniversity， p.201， 1997.""Effects of .ompressible AnnularSeals，'' Proceedings of the 24th Turbomachin-erySymposium， Texas A&MUniversity， p.175， 1995.Egli，T.， ""The Leakage of Steam Through LabyrinthSeals，'' Trans.ASME，1935， pp. 115.122.
Evenson，R.S.，Mason，B.，Frederick，....， St.Onge， andAlain， G. "".evelop-ment and Field Application of a Single Rotor .esign .ry GasSeal，''Proceedings of the 24th TurbomachinerySymposium， Texas A&M University; p. 107; 1995.
FA. ""Rolling Bearing.amage，'' Publication No. WL 82 102/2 Esi 1995.FA. ""RollingBearings，Fundamentals，Types，.esign，'' Publication No. WL 43 1190 EA 1996.Garner，..R.， andLeopard，A.J.， ""Temperature Measurements in Fluid FilmBearings，'' Proceedings of the 13th TurbomachinerySymposium， Texas A&M University; p. 133; 1984.
Herbage，B.S.， ""High Speed Journal and Thrust Bearing.esign，'' Proceedings ofthe 1st. TurbomachinerySymposium， Texas A&MUniversity， October1972， pp. 56.61.
Herbage，B.， ""High Efficiency Fluid Film Thrust Bearings forTurbomachinery，''6th Proceedings of the TurbomachinerySymposium， Texas A&MUniversity，.ecember1977， pp. 33.38.
　
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