Topic
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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01 Mar 2008TL;DR: In this paper, the authors reported a numerical investigation of stall inception in a transonic compressor rotor, NASA Rotor-67, by using the whole flow passages in the computations.
Abstract: The current paper reports a numerical investigation of stall inception in a transonic compressor rotor, NASA Rotor-67, by using the whole flow passages in the computations. Surface roughness is added to one of the blades in order to trigger rotating stall. During stall inception, the tip clearance vortex moved away from the suction surface of the roughened blade's upper neighbour, leading to vortex breakdown. The stall cell was found to propagate opposite the direction of the blade rotation at about 30 per cent of rotational speed. The effect of air bleeding on stabilizing the compressor is also studied in this work. The mean mass flowrate removed from the bleed valves was ∼1.2 per cent of the mainstream flowrate. This amount of bleeding was found to effectively suppress the stalling disturbances.
16 citations
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10 Oct 2010TL;DR: In this article, the leakage performance of various stepped labyrinth seal configurations with different numbers of steps and teeth was investigated for wide operating ranges in terms of pressure ratio and tip clearance, and their dependence on the land structure was investigated.
Abstract: This paper presents the leakage performance of various stepped labyrinth seals. A stationary seal test rig was set up and the leakage characteristics of three seal configurations with different numbers of steps and teeth were investigated for wide operating ranges in terms of pressure ratio and tip clearance. Both the solid and honeycomb land structures were tested. In the honeycomb case, two different sizes were used. The seal was shaped, typical of labyrinth seals for gas turbine applications. The influences of seal configuration, and clearance and honeycomb sizes on the leakage performance were investigated. The relative performances between different seal configurations were compared and their dependence on the land structure was investigated. The honeycomb structure was found to increase leakage for all test conditions. The leakage ratio (honeycomb/solid) was analyzed in terms of geometric variables.Copyright © 2010 by ASME
16 citations
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11 Jul 2004
TL;DR: In this article, a microwave-based sensor designed to operate in temperatures up to 2500°F with a resolution of 0.2 mils and bandwidth up to 25 MHz is presented.
Abstract: Active clearance control has been used to improve efficiency and performance in commercial aircraft engines. Technologies implemented to date rely on compressor bleed air to control clearances based on open loop control and the flight regime (takeoff, cruise, etc.). Open loop systems necessitate a wide safety margin to accommodate the uncertainty in system models that are used to drive such systems. Implementing a feedback control system to optimize clearance has been difficult due to the lack of survivability of clearance measurement technology. Current technologies such as eddy current, capacitive, and laser sensors have been effectively used in laboratory environments but lack the robustness and reliability necessary for long-term use at high engine temperatures. This paper describes a microwave-based sensor designed to operate in temperatures up to 2500°F with a resolution of 0.2 mils and bandwidth up to 25 MHz. The sensor can effectively operate in dirty environments and has the ability to see through oil, combustion products, and other common contaminants. Performance data on the sensor from spin pit testing at 1100°F will be presented to show the viability of the sensor for use in active clearance control.
16 citations
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TL;DR: In this paper, a series of aero-thermo-mechanical analyses were carried out to predict the running tip clearance and the effects of impeller deformation on the performance using two different centrifugal compressors (blade type A and B).
Abstract: A series of aero-thermo-mechanical analyses were carried out to predict the running tip clearance and the effects of impeller deformation on the performance using two different centrifugal compressors (blade type A and B). In operation, impeller deformation due to the combination of centrifugal force, aerodynamic pressure and thermal load results in non-uniform tip clearance profile. The results show that the maximum displacement occurs at the leading edge tip of the impeller blade but maximum stress takes place at the blade root of the impeller. A significant reduction of the tip clearance height has occurred at the leading edge and the trailing edge of the impeller. Due to the reduction of the tip clearance, the tip leakage flow has decreased by 19.4% and 16.2% in the blade type A and B, respectively. The polytropic efficiency of blade type A and B at operating condition has increased by 0.72% and 1.81%, respectively.
16 citations
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TL;DR: In this paper, a simple optical fiber sensor for active control is described, which is simple and thin in structure, with a data sampling rate of about 100 kHz and resolution ratio of better than 0.01mm.
16 citations