Tip clearance

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

Propulsion health monitoring of a turbine engine disk using spin test data

Abstract: This paper considers data collected from an experimental study using high frequency capacitive sensor technology to capture blade tip clearance and tip timing measurements in a rotating turbine engine-like-disk-to predict the disk faults and assess its structural integrity. The experimental results collected at a range of rotational speeds from tests conducted at the NASA Glenn Research Center s Rotordynamics Laboratory are evaluated using multiple data-driven anomaly detection techniques to identify abnormalities in the disk. Further, this study presents a select evaluation of an online health monitoring scheme of a rotating disk using high caliber sensors and test the capability of the in-house spin system.

Influence of Casing Roughness on the Aerodynamic Structure of Tip Vortices in an Axial Flow Turbine

Abstract: The aerodynamic influence of casing surface roughness on over-tip-leakage flow was investigated in a large scale, rotating, axial turbine rig. Phase-locked measurements of the absolute total pressure in a cold flow turbine research facility were conducted at the turbine stage exit using a high-frequency-response total pressure probe. Time accurate measurements provided valuable aerodynamic information quantifying the near tip flow modifications imposed by artificially roughened casing inner surface. A partial segment of the turbine casing was roughened by using a roughness layer of two different mean roughness heights. A smooth wall as a baseline case was also investigated by attaching a smooth layer of equivalent thickness to the casing surface. Artificially roughening the casing surface significantly reduced the leakage mass flow rate and the momentum deficit in the core of the tip vortex. The reductions obtained in the tip vortex size and strength influenced the tip-side passage vortex and other typical core flow characteristics in the passage. The influence of casing roughness was studied in a range of tip clearance values.Copyright © 2006 by ASME

Analysis of Rotor Tip Clearance Loss in Axial-Flow Turbines

Abstract: Tip clearance flow is a major contributor to the losses in axial flow turbines. Tip shrouding reduces the extent of this loss at the expense of more structural complexity and increased centrifugal blade stresses. Recent technological advance in the area of active clearance control promises to minimize the tip clearance loss without the adverse tip shrouding effects. Due to complexity of rotor tip flows, a comprehensive tip clearance loss model that accounts for the tip shape, relative wall motion, tip loading, and stage characteristics has not yet been developed. In the present paper, the rotor tip clearance flow is aerothermodyn amically analyzed and a loss model is presented that includes the above-mentioned effects. Tip leakage discharge coefficient and the stage loading factor are taken as modeling parameters. Finally, earlier tip clearance loss models are reviewed and comparisons are drawn with the present work.

Aeroacoustic Prediction of the Tonal Noise Radiated by a Ring Fan in Uniform Inlet Flow

Abstract: Aeroacoustic simulation of a ring rotor in presence of a uniform inlet ow is presented. An unsteady RANS simulation with a compressible solver is used to compute the ow eld and identify the acoustic sources on the rotor. The tip clearance recirculation shows upstream vortices that appear to impact the rotor blades creating the main source of unsteadiness. Since those vortices rotate at a lower speed than the rotor, the impact frequency implied is shown to be di erent than the blade passing frequency. Besides the aerodynamic simulation, the acoustic signature of this rotor is computed by propagating the noise sources located on the rotor surfaces using two methods: a Ffowcs-Williams & Hawkings analogy in the time-domain, as well as an analytical model in the frequencydomain based on the compact rotating dipole formulation. A comparison with experimental results con rms the aeroacoustic phenomena are well captured and properly propagated by the acoustic codes.