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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TL;DR: In this paper, the authors present a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for use possible in structural health monitoring applications.
Abstract: The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA) has taken a lead role in the investigation of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. As part of this effort, microwave sensor technology has been investigated as a means of making high temperature non-contact blade tip clearance, blade tip timing, and blade vibration measurements for use in gas turbine engines. This paper presents a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for use possible in structural health monitoring applications. The first is a microwave blade tip clearance sensor that has been evaluated on a large scale Axial Vane Fan, a subscale Turbofan, and more recently on sub-scale turbine engine like disks. The second is a novel microwave based blade vibration sensor that was also used in parallel with the microwave blade tip clearance sensors on the experiments with the sub-scale turbine engine disks.
14 citations
Patent•
11 May 1988
TL;DR: In a turbojet engine of the kind having a fan, the face of the radially outer tip of each rotor blade of the fan has a radiussed profile centered at a point R situated in a position displaced on the concavely curved side of the blade relative to its radial axis and beyond the rotational axis of the engine relative to the blade as discussed by the authors.
Abstract: In a turbojet engine of the kind having a fan, the face of the radially outer tip of each rotor blade of the fan has a radiussed profile centered at a point R situated in a position displaced on the concavely curved side of the blade relative to its radial axis and beyond the rotational axis of the engine relative to the blade
14 citations
01 Jan 2008
TL;DR: In this article, the effect of rotor blade profile on the performance of Wells turbine was investigated by model testing under steady flow condition, and the effects of blade profile and non-uniform tip clearance on turbine performance under unsteady flow condition have been investigated numerically by using a quasi-steady analysis.
Abstract: Several of wave energy devices being studied under many wave energy programs in the United Kingdom, Japan, Portugal, India and other countries make use of the principle of an oscillating water column (OWC). In such wave energy devices, a water column which oscillates due to wave motion is used to drive an oscillating air column which is converted into mechanical energy. The energy conversion from the oscillating air column can be achieved by using a self-rectifying air turbine. Wells turbine is a self-rectifying air turbine which is expected to be widely used in wave energy devices with OWC. There are many reports which describe the performance of Wells turbine both at starting and running characteristics. According to these results, Wells turbine has inherent disadvantages: lower efficiency, poorer starting and higher noise level in comparison with conventional turbines. In order to enhance the performance of Wells turbine, some rotor blade profiles have been recommended by various researchers. The aim of this study is to investigate the effect of rotor blade profile on the performance of Wells turbine. In the study, four kinds of blade profile were selected and tested by model testing under steady flow condition. The types of blade profile are as follows: NACA0020; NACA0015; modified NACA0015; and modified Eppler472. The experimental investigations have been performed by use of test section with a casing diameter of 300 mm. Further, the effect of non-uniform tip clearance on the turbine performance was tested and the result was compared with that of the case of Wells turbine with uniform tip clearance. As an additional experiment, the effects of blade profile and non-uniform tip clearance on the performance under unsteady flow condition have been investigated numerically by using a quasi-steady analysis.Copyright © 2008 by ASME
14 citations
10 Jun 1996
TL;DR: In this paper, a simple model was developed to simulate axial flow compressor performance deterioration due to blade erosion, which was based on a mean line row-by-row model, which incorporated the effects of blade roughness and tip clearance.
Abstract: A simple model was developed to simulate axial flow compressor performance deterioration due to blade erosion. The simulation at both design and off-design conditions is based on a mean line row by row model, which incorporates the effects of blade roughness and tip clearance. The results indicate that the increased roughness reduces the pressure ratio as well as the adiabatic efficiency of the compressor at all speeds with the largest influence at 100% speed. Increased tip clearance has a more pronounced effect on the compressor adiabatic efficiency and a lesser effect on the pressure ratio. According to the obtained results the loss in compressor performance due to erosion increases with increased blade loading.Copyright © 1996 by ASME
14 citations
TL;DR: In this article, the effect of axial sweeping on tip leakage flow-related phenomena was investigated with axial compressor rotor blades with different tip clearance levels and axial chordline sweeping.
Abstract: This article presents the study of Tip Chordline Sweeping (TCS) and Axial Sweeping (AXS) of low-speed axial compressor rotor blades against the performance of baseline unswept rotor (UNS) for different tip clearance levels. The first part of the paper discusses the changes in design parameters when the blades are swept, while the second part throws light on the effect of sweep on tip leakage flow-related phenomena. 15 domains are studied with 5 sweep configurations (0∘, 20∘ TCS, 30∘ TCS, 20∘ AXS, and 30∘ AXS) and for 3 tip clearances (0.0%, 0.7%, and 2.7% of the blade chord). A commercial CFD package is employed for the flow simulations and analysis. Results are well validated with experimental data. Forward sweep reduced the flow incidences. This is true all over the span with axial sweeping while little higher incidences below the mid span are observed with tip chordline sweeping. Sweeping is observed to lessen the flow turning. AXS rotors demonstrated more efficient energy transfer among the rotors. Tip chordline sweep deflected the flow towards the hub while effective positive dihedral induced with axial sweeping resulted in outward deflection of flow streamlines. These deflections are more at lower mass flow rates.
14 citations