Composite seal for turbomachinery

A gas path seal suitable for use with a turbine engine or compressor is provided. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor protects the rotor blades. A compliant backing surrounds the shroud. The backing may be made of corrugated sheets or the like with adjacent layers having off-set corrugations, with axes of the folds parallel to the rotor axis. The sheets may be bonded together at points of contact by brazing, welding or the like. In another embodiment a compliant material is covered with a thin ductile layer. A mounting fixture surrounds the backing

Sealing technology for aircraft gas turbine engines

Experimental evaluation under simulated engine conditions revealed that conventional mainshaft seals have disadvantages of high gas leakage rates and wear. An advanced seal concept, the self-acting face seal, has a much lower gas leakage rate and greater pressure and speed capability. In endurance tests (150 hr) to 43 200 rpm the self-acting seal wear was not measurable, indicating noncontact sealing operation was maintained even at this high rotative speed. A review of published data revealed that the leakage through gas path seals has a significant effect on TSFC, stall margin and engine maintenance. Reducing leakages by reducing seal clearances results in rubbing contact, and then the seal thermal response and wear determines the final seal clearances. The control of clearances requires a material with the proper combination of rub tolerance (abradability) and erosion resistance. Increased rub tolerance is usually gained at the expense of reduced erosion resistance and vice versa

Shaft face seal with self-acting lift augmentation for advanced gas turbine engines

Shaft face seal with self acting lift augmentation for advanced gas turbine engine

High speed, self-acting, face-contact shaft seal has low leakage and very low wear

Design adds gas thrust bearing to face of conventional face seal. Bearing lifts seal's carbon face out of contact after startup and establishes thin gas film between sealing surfaces. Operating pressure and speed capabilities are greater than those of conventional face seals

Wear of seal materials used in aircraft propulsion systems

The various types of seal locations in a gas turbine engine are described, and the significance of wear to each type is reviewed. Starting with positive contact shaft seals, existing material selection guidelines are reviewed, and the existing PV (contact pressure X sliding velocity) criteria for selecting seal materials are discussed, along with the theoretical background for these criteria. Examples of wear mechanisms observed to operate in positive contact seals are shown. Design features that can extend the operating capabilities of positive contact seals, including pressure balancing and incorporation of hydrodynamic lift are briefly discussed. It is concluded that, despite the benefits arising from these design features, improved positive contact seal materials from the standpoint of wear, erosion and oxidation resistance will be necessary for further improvements in seal performance and durability, and to meet stringent future challenges

Design study of shaft face seal with self-acting lift augmentation. 4: Force balance

A method for predicting the operating film thickness of self-acting seals is described. The analysis considers a 16.76-cm mean diameter seal that is typical of large gas turbines for aircraft. Four design points were selected to cover a wide range of operation for advanced engines. This operating range covered sliding speeds of 61 to 153 m/sec, sealed pressures of 45 to 217 N/sq cm abs, and gas temperatures of 311 to 977 K. The force balance analysis revealed that the seal operated without contact over the operating range with gas film thicknesses ranging between 0.00046 to 0.00119 cm, and with gas leakage rates between 0.01 to 0.39 scmm

Friction and wear in cryogenic liquids for composites of phenolic and of polytetrafluoroethylene of various particle sizes and concentrations

Friction and wear in cryogenic liquids for phenolic and polytetrafluoroethylene composites of various particle sizes and concentration

Spiral-grooved shaft seals substantially reduce leakage and wear

Rotating shaft seals used in space power systems have spiral grooves in one or both of the opposing seal faces. These grooves induce a pumping action which displaces the intervening fluid radially inward toward the shaft and counters the centrifugal forces which tend to displace the fluid outward

Strong [O III] Objects Among SDSS Broad-Line Active Galaxies

We present the results of a spectral principal component analysis on 9046 broad-line AGN from the Sloan Digital Sky Survey. We examine correlations between spectral regions within various eigenspectra (e.g., between Fe II strength and H$\beta$ width) and confirm that the same trends are apparent in spectral measurements, as validation of our technique. Because we found that our sample had a large range in the equivalent width of [O III] $\lambda$5007, we divided the data into three subsets based on [O III] strength. Of these, only in the sample with the weakest equivalent width of [O III] were we able to recover the known correlation between [O III] strength and full width at half maximum of H$\beta$ and their anticorrelation with Fe II strength. At the low luminosities considered here ($L_{5100 \AA}$ of $10^{42}-10^{46}$ erg s$^{-1}$), interpretation of the principal components is considerably complicated particularly because of the wide range in [O III] equivalent width. We speculate that variations in covering factor are responsible for this wide range in [O III] strength.Comment: 26 pages, 11 figures, published in Ap

Gas turbine ceramic-coated-vane concept with convection-cooled porous metal core

Analysis and flow experiments on a ceramic-coated-porous-metal vane concept indicated the feasibility, from a heat transfer standpoint, of operating in a high-temperature (2500 F) gas turbine cascade facility. The heat transfer and pressure drop calculations provided a basis for selecting the ceramic layer thickness (to 0.08 in.), which was found to be the dominant factor in the overall heat transfer coefficient. Also an approximate analysis of the heat transfer in the vane trailing edge revealed that with trailing-edge ejection the ceramic thickness could be reduced to (0.01 in.) in this portion of the vane