scholarly journals Numerical Investigation of Effects of Tip Clearance Height on Fan Performance and Tip Clearance Flow in an Axial Fan of the Cooling Tower

2012 ◽  
Vol 16 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Keon-Je Oh
Keyword(s):  
Numerical Investigation ◽  
Cooling Tower ◽  
Tip Clearance ◽  
Axial Fan ◽  
Tip Clearance Flow ◽  
Fan Performance ◽  
Clearance Flow

An Experimental and Numerical Investigation Into the Mechanisms of Rotating Instability

2001 ◽  
Author(s):  
Joachim März ◽  
Chunill Hah ◽  
Wolfgang Neise
Keyword(s):  
Experimental Study ◽  
Numerical Investigation ◽  
Axial Flow ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stable Mode ◽  
Tip Clearance Flow ◽  
Double Phase ◽  
Clearance Flow ◽  
Rotating Instability

This paper reports on an experimental and numerical investigation aimed at understanding the mechanisms of rotating instabilities in a low speed axial flow compressor. The phenomena of rotating instabilities in the current compressor were first identified with an experimental study. Then, an unsteady numerical method was applied to confirm the phenomena and to interrogate the physical mechanisms behind them. The experimental study was conducted with high-resolution pressure measurements at different clearances, employing a double phase-averaging technique. The numerical investigation was performed with an unsteady 3-D Navier-Stokes method that solves for the entire blade row. The current study reveals that a vortex structure forms near the leading edge plane. This vortex is the result of interactions among the classical tip-clearance flow, axially reversed endwall flow, and the incoming flow. The vortex travels from the suction side to the pressure side of the passage at roughly half of the rotor speed. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. Due to the nature of this vortex, the classical tip-clearance flow does not spill over into the following blade passage. This behavior of the tip-clearance flow is why the compressor operates in a stable mode even with the rotating instability, unlike traditional rotating stall phenomena.

An Experimental and Numerical Investigation into the Mechanisms of Rotating Instability

2002 ◽  
Vol 124 (3) ◽  
pp. 367-374 ◽  
Author(s):  
Joachim Ma¨rz ◽  
Chunill Hah ◽  
Wolfgang Neise
Keyword(s):  
Experimental Study ◽  
Numerical Investigation ◽  
Axial Flow ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stable Mode ◽  
Tip Clearance Flow ◽  
Double Phase ◽  
Clearance Flow ◽  
Rotating Instability

This paper reports on an experimental and numerical investigation aimed at understanding the mechanisms of rotating instabilities in a low speed axial flow compressor. The phenomena of rotating instabilities in the current compressor were first identified with an experimental study. Then, an unsteady numerical method was applied to confirm the phenomena and to interrogate the physical mechanisms behind them. The experimental study was conducted with high-resolution pressure measurements at different clearances, employing a double phase-averaging technique. The numerical investigation was performed with an unsteady 3-D Navier-Stokes method that solves for the entire blade row. The current study reveals that a vortex structure forms near the leading edge plane. This vortex is the result of interactions among the classical tip-clearance flow, axially reversed endwall flow, and the incoming flow. The vortex travels from the suction side to the pressure side of the passage at roughly half of the rotor speed. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. Due to the nature of this vortex, the classical tip clearance flow does not spill over into the following blade passage. This behavior of the tip clearance flow is why the compressor operates in a stable mode even with the rotating instability, unlike traditional rotating stall phenomena.

Experimental Investigation of Unsteady Tip Clearance Flow in a Counter-Rotating Fan

2015 ◽  
Author(s):  
Wang Yangang ◽  
Yue Shaoyuan ◽  
Chen Junxu ◽  
Wu Canghai
Keyword(s):  
Rotational Frequency ◽  
Tip Clearance ◽  
Axial Fan ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Dynamic Experiments ◽  
Clearance Flow ◽  
Stall Cells ◽  
The Time Domain ◽  
Frequency Controller

In this paper, both static and dynamic experiments were conducted on a low speed counter-rotating axial fan (CRAF) to investigate its stall process. The casing pressures adjacent to the rotor tip clearance were recorded using arrays of dynamic transducers along the chordwise and circumferential directions. Special chokes were installed at the input and output of the frequency controller to suppress the electromagnetism interference, and digital filters were designed to select the desired components. The frequency spectrum analysis shows that the frequencies of the stall inception and the fully developed stall cells are not exactly the same with the value of 46% and 50% of the rotor rotational frequency. Conclusions can be drawn from the wavelet analysis that the stall inception of the CRAF turns out to be modal inception, and the stall firstly occurs on the second rotor. The propagation of stall cells is shown in the time domain map which indicates that only one stall cell exists.

Investigation of a Tip Clearance Cascade in a Water Analogy Rig

1986 ◽  
Vol 108 (1) ◽  
pp. 38-46 ◽  
Author(s):  
J. A. H. Graham
Keyword(s):  
Turbine Blades ◽  
Flow Region ◽  
Tip Clearance ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Tip Clearance Flow ◽  
Pressure Profiles ◽  
Clearance Flow ◽  
Hot Film ◽  
Model Features

The tip clearance flow region of high-pressure axial turbine blades for small gas turbine engines has been investigated in a water flow cascade. The blade model features variable clearance and variable endwall speeds. The cascade is scaled for Reynolds number and sized to give velocities suitable for visualization. Pressure profiles were measured on one blade, and correlated with the visualization. Unloading is found to be a major feature of the pressure field at both tip and midspan, and is intimately connected with scraping effects and the behavior of the clearance vortex. Some initial hot-film velocity measurements are also presented.

Endwall Blockage in Axial Compressors

1999 ◽  
Vol 121 (3) ◽  
pp. 499-509 ◽  
Author(s):  
S. A. Khalid ◽  
A. S. Khalsa ◽  
I. A. Waitz ◽  
C. S. Tan ◽  
E. M. Greitzer ◽  
...  
Keyword(s):  
Tip Clearance ◽  
Design Parameters ◽  
Tip Clearance Flow ◽  
Axial Compressors ◽  
Clearance Flow ◽  
Flow Features ◽  
Physical Insight ◽  
Level Loading ◽  
Stagger Angle ◽  
Insight Into

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.

Sign in / Sign up

Export Citation Format

Share Document