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Tip clearance

About: Tip clearance is a research topic. Over the lifetime, 2637 publications have been published within this topic receiving 32671 citations.


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Journal ArticleDOI
Qianfeng Zhang1, Juan Du1, Zhihui Li1, Jichao Li1, Hongwu Zhang1 
TL;DR: In this paper, the axial slot casing treatment (ASCT) was applied to a highly loaded mixed-flow compressor with tip clearance of 0.4 mm to reveal the effects of axial slots on the loss mechanisms in the compressor.
Abstract: Casing treatments (CT) can effectively extend compressors flow ranges with the expense of efficiency penalty. Compressor efficiency is closely linked to loss. Only revealing the mechanisms of loss generation can design a CT with high aerodynamic performance. In the paper, a highly-loaded mixed-flow compressor with tip clearance of 0.4 mm was numerically studied at a rotational speed of 30,000 r/min to reveal the effects of axial slot casing treatment (ASCT) on the loss mechanisms in the compressor. The results showed that both isentropic efficiency and stall margin were improved significantly by the ASCT. The local entropy generation method was used to analyze the loss mechanisms and to quantify the loss distributions in the blade passage. Based on the axial distributions of entropy generation rate, for both the cases with and without ASCT, the peak entropy generation rate increased in the rotor domain and decreased in the stator domain during throttling the compressor. The peak entropy generation in rotor was mainly caused by the tip leakage flow and flow separations near the rotor leading edge for the mixed-flow compressor no matter which casing was applied. The radial distributions of entropy generation rate showed that the reduction of loss in the rotor domain from 0.4 span to the rotor casing was the major reason for the efficiency improved by ASCT. The addition of ASCT exerted two opposite effects on the losses generated in the compressor. On the one hand, the intensity of tip leakage flow was weakened by the suction effect of slots, which alleviated the mixing effect between the tip leakage flow and main flow, and thus reduced the flow losses; On the other hand, the extra losses upstream the rotor leading edge were produced due to the shear effect and to the heat transfer. The aforementioned shear effect was caused by the different velocity magnitudes and directions, and the heat transfer was caused by temperature gradient between the injected flow and the incoming flow. For case with smooth casing (SC), 61.61% of the overall loss arose from tip leakage flow and casing boundary layer. When the ASCT was applied, that decreased to 55.34%. The loss generated by tip leakage flow and casing boundary layer decreased 20.54%) relatively by ASCT.

15 citations

Journal ArticleDOI
TL;DR: In this article, the effects of rotor tip clearance on the inlet hot streak migration characteristics in high pressure stage of a Vaneless Counter-Rotating Turbine were investigated.
Abstract: In this paper, three-dimensional multiblade row unsteady Navier-Stokes simulations at a hot streak temperature ratio of 2.0 have been performed to reveal the effects of rotor tip clearance on the inlet hot streak migration characteristics in high pressure stage of a Vaneless Counter-Rotating Turbine. The hot streak is circular in shape with a diameter equal to 25% of the high pressure turbine stator span. The hot streak center is located at 50% of the span and the leading edge of the high pressure turbine stator. The tip clearance size studied in this paper is 2.0mm (2.594% high pressure turbine rotor height). The numerical results indicate that the hot streak mixes with the high pressure turbine stator wake and convects towards the high pressure turbine rotor blade surface. Most of hotter fluid migrates to the pressure surface of the high pressure turbine rotor. Only a few of hotter fluid rounds the leading edge of the high pressure turbine rotor and migrates to the suction surface. The migration characteristics of the hot streak in the high pressure turbine rotor are dominated by the combined effects of secondary flow, buoyancy and leakage flow in the rotor tip clearance. The leakage flow trends to drive the hotter fluid towards the blade tip on the pressure surface and to the hub on the suction surface. Under the effect of the leakage flow, even partial hotter fluid near the pressure surface is also driven to the rotor suction surface through the tip clearance. Compared with the case without rotor tip clearance, the heat load of the high pressure turbine rotor is intensified due to the effects of the leakage flow. And the results indicate that the leakage flow effects trend to increase the low pressure turbine rotor inlet temperature at the tip region. The air flow with higher temperature at the tip region of the low pressure turbine rotor inlet will affect the flow and heat transfer characteristics in the downstream low pressure turbine.Copyright © 2008 by ASME

15 citations

Journal ArticleDOI
TL;DR: In this article, an experimental investigation of the effect of tip clearance on the performance of a shrouded supersonic impulse turbine was performed in a single-staged axial flow impulse turbine designed to have a rotor inlet relative Mach number of 1.7.
Abstract: An experimental investigation of the effect of tip clearance on the performance of a shrouded supersonic impulse turbine was performed in this study. A single-staged axial flow impulse turbine designed to have a rotor inlet relative Mach number of 1.7 was used for the experiment. Turbine efficiency was measured at various settings of tip clearances, rotational speeds, and turbine pressure ratios to observe the characteristics of the efficiency gradient. The overall efficiency of the supersonic impulse turbine was largely affected by rotational speed. For a fixed rotational speed, local maximum efficiency was found near a turbine pressure ratio at which the turbine nozzle was fully expanded. At a reference test point, the linearly estimated efficiency gradient was 0.09. However, efficiency variation with respect to tip clearance was nonlinear, and relatively larger efficiency gradients were found at small tip clearances and high rotational speeds. It has been found that the efficiency gradient varies linearly with the cube of rotational speed and shows its minimum value near the reference turbine pressure ratio.

15 citations

Journal ArticleDOI
TL;DR: In this article, the rotor tip clearance was found to control the performance of the axial compressor by influencing the flow within the rotor blade passages, and the importance of the flow in the endwall regions in determining the overall compressor performance.
Abstract: Detailed measurements have been made within an axial compressor operating both at design point and near stall. Rotor tip clearance was found to control the performance of the machine by influencing the flow within the rotor blade passages. This was not found to be the case in the stator blade row, where hub clearance was introduced beneath the blade tips. Although the passage flow was observed to be altered dramatically, no significant changes were apparent in the overall pressure rise or stall point.Small tip clearances in the rotor blade row resulted in the formation of corner separations at the hub, where the blade loading was highest. More representative clearances resulted in blockage at the tip due to the increased tip clearance flow. The effects which have been observed emphasize both the three dimensional nature of the flow within compressor blade passages, and the importance of the flow in the endwall regions in determining the overall compressor performance.Copyright © 1989 by ASME

15 citations

Patent
24 Mar 2010
TL;DR: In this article, the active tip clearance control (ATCC) apparatus of an aircraft gas turbine engine is isolated from one another in order to improve both the ATCC performance and bypass air duct performance.
Abstract: An active tip clearance control (ATCC) apparatus (38) of an aircraft gas turbine engine is situated within a pressurized core case (13) of the engine. First and second portions (34,42) of bypass air flow passing through a compressed core compartment (30) and the ATCC apparatus (38), are isolated from one another in order to improve both the ATCC performance and bypass air duct performance.

15 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202354
2022149
202189
2020111
2019116
201897