Showing papers on "Tip clearance published in 1979"

Blade tip clearance control

Abstract: A turbine blade tip seal assembly for controlling the blade tip clearance between a flexible outer shroud and the tips of a thermally expansible row of turbine blades on a turbine rotor includes a fixed outer shroud with a pressure deflectable wall portion thereon located in surrounding, radially outwardly relationship with blade tips on the blades of a turbine rotor and wherein an excessive blade tip to shroud wall spacing is maintained when the engine is at cold start conditions; said turbine blades of the turbine rotor expanding in response to increases in operating temperature within the engine during turbine engine operation to partially close the excessive blade tip to shroud clearance and further including pressurizable means responsive to turbine operation to produce pressure bias on the deflectable wall to cause it to be deflected raidally inwardly to further reduce the excessive blade tip clearance so as to produce a resultant operative clearance between the tip of the turbine rotor and the shroud to prevent excessive gas bypass between the wall and the blade tips; said pressurizable means including a secondary pressurizable chamber responsive to engine operating conditions to apply a secondary pressure on the wall to produce a fine-tuned adjustment of the blade tip clearances between leading and trailing edges of the blades when the engine has reached an elevated equilibrium temperature of operation.

Air-cooled turbine rotor shroud with restraints

Abstract: A stationary air-cooled shroud or cylinder forming a portion of a turbine asembly includes an inner ring having a matrix of grooves formed therein, and an outer restraining ring covering the matrix so as to form a labyrinth of passageways for the flow of cooling air therethrough A suspension ring cooperates with the inner ring and the restraint ring to define an entry flow path for the cooling air, and also a plenum chamber having an auxiliary outlet to provide film cooling air to the clearance spacing between the inner ring and the rotor blade tips The fow of cool air through the labyrinth is operative to reduce the level and gradient of the metal tempertures in the shroud in order to obtain improved turbine blade tip clearance control

Laser-optical blade tip clearance measurement system

Abstract: A laser-optical measurement system was developed to measure single blade tip clearances and average blade tip clearances between a rotor and its gas path seal in rotating component rigs and complete engines. The system is applicable to fan, compressor and turbine blade tip clearance measurements. The engine mounted probe is particularly suitable for operation in the extreme turbine environment. The measurement system consists of an optical subsystem, an electronic subsystem and a computing and graphic terminal. Bench tests and environmental tests were conducted to confirm operation at temperatures, pressures, and vibration levels typically encountered in an operating gas turbine engine.

Effects of Fluid Leakage on Performance of a Centrifugal Compressor

Abstract: Fluid loss caused by leaks through the impeller tip clearance was investigated for a centrifugal compressor. Operating conditions, Reynolds number, and clearance were varied independently during the experiment. It was found that the average compressor performance would be reduced by about 4 percent when the relative clearance was increased from 0.0125 to 0.125 and the resulting leakage loss was dependent on the Reynolds number, the tendency of which was just opposite in case of wall friction loss, as was well-known. Moreover, a determination of the leakage loss coefficient was made as a function of the relative clearance, relative leak level and the Reynolds number as the result of this experiment.

An Application of 3-D Viscous Flow Analysis to the Design of a Low-Aspect-Ratio Turbine

Abstract: Previously reported cascade test results verified and provided a calibration of the 3-D viscous flow analysis. This paper describes the subsequent AFAPL-sponsored technology program in which the 3-D viscous flow computer program was used to optimize the low-aspect-ratio stator of a high-work turbine stage. The optimization procedure, in conjunction with the radial distribution of energy extraction, led to innovative-but-realistic blading for advanced gas generator turbines. A turbine stage was tested with this stator, in conjunction with an appropriate rotor design. The total-to-total design-point efficiency — 92 percent at 1-percent tip clearance — was achieved at 31.83 Btu/lbm specific work. In addition to stage tests, separate stator tests were conducted including a measurement of total pressure loss and stator reaction torque, which provided baseline data to assess interaction effects during stage testing with stator reaction measurements “in vivo.”Copyright © 1979 by ASME

Effect of Rotor Tip Clearance and Configuration on Overall Performance of a 12.77-Centimeter Tip Diameter Axial-Flow Turbine

Abstract: An extensive experimental investigation was made to determine the effect of varying the rotor tip clearance of a 12.77-cm-tip diameter, single-stage, axial-flow reaction turbine. In this investigation, the rotor tip clearance was obtained by use of a recess in the casing above the rotor blades and also by use of a reduced blade height. For the recessed casing configuration, the optimum rotor blade height was found to be the one where the rotor tip diameter was equal to the stator tip diameter. The tip clearance loss associated with this optimum recessed casing configuration was less than that for the reduced blade height configuration.Copyright © 1979 by ASME

Noise generated from non-uniform clearance of turbo-compressors and fans of aircraft

Abstract: Attainment of high turbo-compressor aerothermodynamic performance requires very small rotor tip clearance which also helps keep low noise levels. Non-uniform rotor-stator tip clearance in a turbocompressor is a source of acoustic annoyance to pilots. Depending on the degree of nonuniformity of the tip clearance, a characteristic noise known as "grinding" arises from the blade tips forming nearly 60 to 75 percent of the total compressor noise. Besides, periodic longitudinal play of the compressor gives rise to resonance. A physical model has been proposed in this paper for explaining both grinding and resonance from the blade tips of rotor blades with excessive tip clearance. The paper highlights the importance of maintaining uniformity of compressor and fan blade tip clearance within narrow limits to eliminate the distracting noise which causes annoyance and pilot fatigue. An equation has been derived for the intensity of the grinding noise and the noise due to compressor tip clearance.

JT9D-70/59 Improved High Pressure Turbine Active Clearance Control System

Abstract: The JT9D-70/59 high pressure turbine active clearance control system was modified to provide reduction of blade tip clearance when the system is activated during cruise operation. The modification increased the flow capacity and air impingement effectiveness of the cooling air manifold to augment turbine case shrinkage capability, and increased responsiveness of the airseal clearance to case shrinkage. The simulated altitude engine testing indicated a significant improvement in specific fuel consumption with the modified system. A 1000 cycle engine endurance test showed no unusual wear or performance deterioration effects on the engine or the clearance control system. Rig tests indicated that the air impingement and seal support configurations used in the engine tests are near optimum.