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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15 Nov 2006TL;DR: In this article, a gas turbine engine (10) includes a compressor (18), combustor (20), and turbine (22) having a row of blades mounted inside a surrounding turbine shroud (44).
Abstract: A gas turbine engine (10) includes a compressor (18), combustor (20), and turbine (22) having a row of blades (40) mounted inside a surrounding turbine shroud (44). A heat exchanger (56) is used for cooling pressurized air bled from the compressor (18). A distribution network (60-66) joins the heat exchanger (56) to the turbine (22) for selectively channeling air from the heat exchanger (56) below the blades (40) and above the shroud (44) for controlling blade tip clearance.
80 citations
TL;DR: In this article, a row-by-row heat-transfer analysis of cylinders in a crossflow of air in a flat rectangular duct has been performed, where the cylinders were attached perpendicular to one of the principle walls of the duct, with a clearance space between the free ends of the cylinders and the other principle wall.
80 citations
TL;DR: In this paper, a combined study of tip clearance and tip vortex cavitations in a pump-type rotating machine is presented, and cavitation inception is determined for various gap heights, clearance and blade geometries, and rotor operating conditions.
Abstract: A combined study of tip clearance and tip vortex cavitations in a pump-type rotating machine is presented. Cavitation patterns are observed and cavitation inception is determined for various gap heights, clearance and blade geometries, and rotor operating conditions. An optimum clearance geometry is seen to eliminate clearance cavitation when the clearance edge is rounded on the blade pressure side. The gap height has a strong effect on clearance cavitation inception, but the trends vary considerably when other parameters are also modified. The gap height and clearance geometry have less influence on tip vortex cavitation but forward and backward blade skew is observed to reduce and increase tip vortex cavitation, respectively, as compared to a blade with no skew.
79 citations
TL;DR: In this article, the authors presented a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37 and found that the casing treatments were an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability.
Abstract: The control of tip leakage flow (TLF) through the clearance gap between the moving and stationary components of rotating machines is still a high-leverage area for improvement of stability and performance of aircraft engines. Losses in the form of flow separation, stall, and reduced rotor work efficiency are results of the tip leakage vortex (TLV) generated by interaction of the main flow and the tip leakage jet induced by the blade pressure difference. The effects are more detrimental in transonic compressors due to the interaction of shock-TLV. It has been previously shown that the use of slots and grooves in the casing over tip of the compressor blades, known as casing treatment, can substantially increase the stable flow range and therefore the safety of the system but generally with some efficiency penalties. This paper presents a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37. Compressor characteristics have been compared to the experimental results for smooth casing with a 0.356 mm tip clearance and show fairly good agreement. Casing treatments were found to be an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability. The present work provides guidelines for improvement of steady-state performance of the transonic axial-flow compressors and improvement of the stable operating range of the system.Copyright © 2004 by ASME
79 citations
TL;DR: The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions.
Abstract: When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions.
79 citations