Showing papers on "Tip clearance published in 1974"

Turbine blade tip seal

Abstract: In a gas turbine engine a seal which minimizes blade tip clearance at a design operating condition is disclosed. In the cold engine condition the radius of curvature of the sealing surface is less than the radius of the turbine wheel at the blade tips. At the design operating condition the radius of curvature of the sealing surface is substantially equal to the wheel radius. The seal is supported by arcuate hooks which are sufficiently flexible to accommodate the changes in the radius of curvature of the sealing surface over the indicated range.

Some Results From Tests on a High Work Axial Gas Generator Turbine

Abstract: Aerodynamic test results are presented for a single-stage, axial gas generator turbine of 3.9:1 design pressure ratio. Test results are also shown for a number of variants on this design, indicating the effect on aerodynamic performance of degree of reaction, nozzle and rotor aspect ratio, rotor blade channel design, rotor tip clearance, radial work distribution and effect of nozzle endwall contouring. Detailed aerodynamic observations are compared with analytical predictions. Of the design parameters examined, rotor blade aspect ratio, tip clearance and channel diffusion were found to have the greatest influence on losses. Operation at pressure ratios above the design was found to be improved with “open” rotor stagger, yielding a reduced design point degree of reaction.Copyright © 1974 by ASME

Research turbine for high-temperature core engine application. 2: Effect of rotor tip clearance on overall performance

Abstract: A 25.4-cm (10-in) tip diameter turbine was tested to determine the effect of rotor radial tip clearance on turbine overall performance. The test turbine was a half-scale model of a 50.8-cm-(20-in.-) diameter research turbine designed for high-temperature core engine application. The test turbine was fabricated with solid vanes and blades with no provision for cooling air and tested at much reduced inlet conditions. The tests were run at design speed over a range of pressure ratios for three different rotor clearances ranging from 2.3 to 6.7 percent of the annular blade passage height. The results obtained are compared to the results obtained with three other turbines of varying amounts of reaction.

Theoretical Studies of Tip Clearance and Radial Variation of Blade Loading on the Operation of Ducted Fans and Propellers

Abstract: Actuator disc theory and surface singularity techniques are applied to the performance of ducted fans and propellers, with particular reference to the radial clearance between rotor tips and duct inner surface and the radial distribution of rotor-blade loading. Many accounts have been written on ducted propellers but none includes the effects of clearance in any other than an approximate manner, that is, one-dimensional theory. The few studies that have been made of the radial variation in blade loading have been inconclusive and vague, mainly because of the inadequate duct model employed.Here an accurate nonlinear theory is used to represent the duct and centrebody which has already been used successfully in the prediction of ducted propeller performance. Actuator disc theory, which is particularly suitable for combination with blade-element theory, is used to represent the variable-load propeller. Computed performance characteristics compare favourably with experimental results and the present studies e...

Design, Fabrication, and Demonstration of a Miniaturized Tip Clearance Measuring Device

Abstract: : This report describes the design, fabrication, and demonstration of a miniaturized turbine blade tip clearance measurement system for use with small gas turbine engines during engine operation. This system was originated by Pratt and Whitney Aircraft and uses laser light that is focused on the blade tips. The light reflected from the blade tips is imaged onto an output device. The relationship between the change in tip clearance and the change in position of the output light spot provides a direct indication of tip clearance. (Modified author abstract)