Showing papers on "Tip clearance published in 1977"
01 Jun 1977
TL;DR: In this paper, a vaned diffuser and a vaneless diffuser were used to test the impeller axial tip clearance at design speed to determine effect on stage and impeller performance.
Abstract: A backswept impeller with design mass flow rate of 1.033 kg/sec was tested with both a vaned diffuser and a vaneless diffuser to establish stage and impeller characteristics. Design stage pressure ratio of 5.9:1 was attained at a flow slightly lower than the design value. Flow range at design speed was 6 percent of choking flow. Impeller axial tip clearance at design speed was varied to determine effect on stage and impeller performance.
16 citations
01 Feb 1977
TL;DR: In this article, the overall performance of a transonic fan stage for various tip clearances, with and without casing treatment, was evaluated with a solid casing and with open skewed slots and closed skewed slots over the rotor blade tips.
Abstract: The overall performance of a transonic fan stage is presented for various tip clearances, with and without casing treatment. The stage was tested with a solid casing, and with open skewed slots and closed skewed slots in the casing over the rotor blade tips. Four nominal nonrotating rotor blade tip clearances from 0.061 to 0.178 centimeter were used. For all three casings, the pressure ratio and efficiency decreased with increasing tip clearance. The stall margin for a given casing also decreased with increasing clearance. At design speed and a given tip clearance, the highest stall margin was obtained with the open-slot casing, and the lowest stall margin was obtained with the solid casing.
7 citations
01 Sep 1977
TL;DR: In this article, two tip clearance configurations, one with a recess in the casing and the other with a reduced rotor blade height, were investigated at design equivalent speed over a range of tip clearance from about 2.0 to 5.0 percent of the stator blade height.
Abstract: Two tip clearance configurations, one with a recess in the casing and the other with a reduced rotor blade height, were investigated at design equivalent speed over a range of tip clearance from about 2.0 to 5.0 percent of the stator blade height. The optimum configuration with a recess in the casing was the one where the rotor tip diameter was equal to the stator tip diameter (zero blade extension). For this configuration there was an approximate 1.5 percent decrease in total efficiency for an increase in tip clearance of 1 percent of stator blade height. For the reduced blade height configurations there was an approximate 2.0 percent decrease in total efficiency for an increase in tip clearance of 1 percent of stator blade height.
3 citations
01 Dec 1977
TL;DR: In this paper, the first-stage turbine of the Lycoming advanced gas generator was used as the test vehicle for analytic and experimental evaluation Tip-clearance response of the stage was analyzed for steady-state and transient operating conditions through the use of a one-dimensional tip-clearing calculation technique.
Abstract: : This report describes the analysis and measurement of turbine tip clearance over the full range of operation of an advanced gas turbine engine The first-stage turbine of the Lycoming advanced gas generator was used as the test vehicle for analytic and experimental evaluation Tip-clearance response of the stage was analyzed for steady-state and transient operating conditions through the use of a one-dimensional tip-clearance calculation technique Measurement was accomplished with three laser tip-clearance measurement probes that operate on an optical beam triangulation principle Comparison of analytic and measured tip-clearance results showed measured clearance to be tighter than predicted over the entire power spectrum This differential was attributed primarily to a two-dimensional thermal strain distribution in the shroud which had not been accounted for by the analytic technique Excellent correlation was obtained between the transient tip-clearance response characteristics resulting from analysis and measurement Comparison of measured and predicted component temperatures under steady-state and transient operating conditions verified the accuracy of the thermal analysis procedure Component distortion, as well as response to transient engine operation, was found to have significant impact on minimum operating tip clearance (Author)
2 citations
01 Nov 1977
TL;DR: In this article, the effects of scaling, tip clearance, and IGV reset on the performance of a low aspect ratio compressor stage were evaluated by a linear factor of 0.304.
Abstract: A program was conducted to evaluate the effects of scaling, tip clearance, and IGV reset on the performance of a low aspect ratio compressor stage. Stage design was obtained by scaling an existing single stage compressor by a linear factor of 0.304. The design objective was to maintain the meanline velocity field of the base machine in the smaller size. Adjustments were made to account for predicted blockage differences and to chord lengths and airfoil edge radii to obtain reasonable blade geometries. Meanline velocity diagrams of the base stage were not maintained at the scaled size. At design speed and flowrate the scaled stage achieved a pressure ratio of 1.423, adiabatic efficiency of 0.822, and surge margin of 18.5%. The corresponding performance parameters for the base stage were 1.480, 0.872, and 25.2%, respectively. The base stage demonstrated a peak efficiency at design speed of 0.872; the scaled stage achieved a level of 0.838. When the scaled stage rotor and stator tip clearances were doubled, the stage achieved a pressure ratio of 1.413, efficiency of 0.799, and surge margin of 16.0% at the design flowrate. The peak stage efficiency at design speed was 0.825 with the increased clearance. Increased prewhirl lowered the stage pressure ratio as expected. Stage efficiency was maintained with ten degrees of increased prewhirl and then decreased substantially with ten additional degrees of reset.