scholarly journals Hot Wire Measurements During Rotating Stall in a Variable Pitch Axial Flow Fan

1996 ◽  
Author(s):  
Eduardo Blanco-Marigorta ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria
Keyword(s):  
Direct Method ◽  
Axial Flow ◽  
Rotating Stall ◽  
Hot Wire ◽  
Axial Flow Fan ◽  
Variable Pitch ◽  
Absolute Flow ◽  
Series Of Experiments ◽  
The Absolute ◽  
Absolute Frame

This work deals with a series of experiments on the influence of the blade pitch on the rotating stall phenomenon in an industrial variable pitch, low-speed axial flow fan with low hub-to-tip ratio. Two simple hot wires were used to detect the rotating stall. One in the absolute frame and the other in the relative frame rotating with the rotor. The rotating stall features were determined, ranging from the non-existence in the whole flow range with the lowest pitch tested to one and two flow cells with the greatest pitch. Then, a triple hot wire, calibrated by a direct method, was used to measure the absolute flow field upstream and downstream from the rotor, before and during rotating stall for five distinct blade pitches. These measurements allow us to characterize different rotating stall structures. To understand the phenomena better, some tests were carried out in the relative frame, with the probe rotating with the rotor. An intermediate blade pitch with a single rotating cell was selected and measurements were taken at three radial positions. Velocity maps for all these measurements are presented.

Improving Stall Margin by Using an Air-Separator for a Variable-Pitch Axial-Flow Fan

2004 ◽  
Author(s):  
Takahiro Nishioka ◽  
Shuuji Kuroda ◽  
Tadashi Kozu
Keyword(s):  
Axial Flow ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Axial Flow Fan ◽  
Clearance Ratio ◽  
Variable Pitch ◽  
Stall Margin ◽  
Operating Range ◽  
Exposure Ratio ◽  
Air Separator

An air-separator for extending the operating range of a variable-pitch axial-flow fan has been developed. It has a circular-are outer casing, a part of which forms the guide vane at the inlet of the air-separator. To obtain a wide operating range and to minimize penalties in terms of efficiency and noise, the influence of exposure and clearance ratios at various stagger-angle settings for rotor blades in low-speed and high-speed axial flow fans was experimentally investigated. Flow distributions and pressure fluctuations downstream of the rotor were also measured in order to investigate the influence of the air-separator on rotating stall. The distributions and fluctuations suggested that the air-separator decreased the blockage effect near the rotor tip and suppressed the rotating stall. Moreover, stall-margin and pressure-rise improvements were independent of the clearance ratio. These improvements depended on the exposure ratio and stagger-angle settings for the rotor blades. The fan efficiency for the air-separator also depended on the exposure ratio. In addition, the efficiency had the opposite tendency to the stall-margin and pressure-rise improvements. In contrast, the noise for the air-separator was independent of the exposure ratio and decreased as the clearance ratio increased. For the optimum combination of the exposure and clearance ratios, the stall-margin and pressure-rise were improved by over 20% with minimized penalties in terms of efficiency and noise. It is concluded from these results that the developed air-separator can provide a wide operating range for a variable-pitch axial-flow fan.

Application of casing treatment to an industrial axial-flow fan

1998 ◽  
Vol 212 (4) ◽  
pp. 225-233 ◽  
Author(s):  
S D Hill ◽  
R L Elder ◽  
A B McKenzie
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Strain Gauges ◽  
Axial Flow Fan ◽  
Fan Noise ◽  
Flow Measurements ◽  
Casing Treatment ◽  
Blade Tip ◽  
Fan Blade ◽  
Insight Into

This paper deals with an experimental investigation into the influence of a vaned recess casing treatment on the performance of an industrial-type axial-flow fan with a hub-tip ratio of 0.4. The treatment has been tested in a variety of configurations relative to the fan, with an emphasis on the amount of fan blade tip exposure to the treatment. Two sets of blading, one of which is of the fully reversible type, have been investigated. Detailed flow measurements have been carried out with a slanted hot wire probe to provide an insight into the operation of the device and into the nature of the rotating stall in the solid casing configuration. Strain gauges have been employed to enable blade stresses to be recorded and an in-duct microphone to enable comparative tests on fan noise has also been used.

scholarly journals Effects of Operating Conditions on the Flow in the Moving Blade Passage of a Single Stage Axial-Flow Fan

1997 ◽  
Vol 3 (4) ◽  
pp. 269-276 ◽  
Author(s):  
Tsutomu Adachi ◽  
Yutaka Yamashita ◽  
Kennichiro Yasuhara ◽  
Tatsuo Kawai
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Hot Wire ◽  
Axial Flow Fan ◽  
Blade Passage ◽  
Operational Conditions ◽  
Flow Phenomena ◽  
Steady Velocity

Three dimensional steady and unsteady velocity distributions in the axial flow fan were measured using a hot wire probe for various operational conditions, various rotational speeds and various measuring positions. For measuring the velocity distributions in the blade passage, a specially designed and manufactured hot wire traversing apparatus was used. Steady velocity distributions, turning angles, effects of incident to the cascade, flow leakage through the tip clearance and effects of the flow separation show the flow phenomena through the blade passages. Unsteady velocity distributions show time dependent procedures of the wake flowing through the moving blade passage. Considering these results of measurements, the effects of the upstream stationary blade and the effects of Reynolds number on the flow were considered.

Total Unsteadiness Downstream of an Axial Flow Fan With Variable Pitch Blades

2001 ◽  
Vol 124 (1) ◽  
pp. 280-283 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria-Morros ◽  
Eduardo Blanco-Marigorta
Keyword(s):  
Axial Flow ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Major Influence ◽  
Axial Flow Fan ◽  
Variable Pitch ◽  
Fan Performance ◽  
Performance Curves ◽  
Unsteady Operation ◽  
Variable Operating Conditions

Variable pitch axial flow fans are widely used in industrial applications to satisfy variable operating conditions. The change of the blade pitch leads to a different rotor geometry and has a major influence on the unsteady operation of the machine. In this work, an experimental research on an axial flow fan with variable pitch blades has been carried out. First of all, the fan performance curves has been obtained. Then the flow field has been measured at ten radial locations both at the inlet and exit rotor plane using hot wire anemometry. Velocity components and total unsteadiness were determined and analyzed in order to characterize the influence of pitch blade and operating conditions on the flow structure.

scholarly journals Investigation on Unsteady Flow Characteristics in an Axial-Flow Fan under Stall Conditions

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 958
Author(s):  
Chenlong Jiang ◽  
Mengjiao Li ◽  
Enda Li ◽  
Xingye Zhu
Keyword(s):  
Unsteady Flow ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Rotating Stall ◽  
Air Separation ◽  
Flow Coefficient ◽  
Tip Leakage Flow ◽  
Axial Flow Fan ◽  
Time Frequency ◽  
Flow Capacity

Based on Shear Stress Transport (SST) turbulence model for unsteady simulation of an axial-flow fan, this paper studies the time-frequency information in the hump region, and investigates the disturbance information of spike and modal wave under different flow coefficients based on continuous wavelet transform (CWT). The results show that before the hump point, the low-frequency modal wave occupies the main disturbance form and circularly propagates at 1/10 of the rotor speed, and the axial-flow fan does not enter the stall stage; while after the flow coefficient reduces to the hump point, the spike wave with higher frequency replaces the modal wave as the main disturbance mode while the axial-flow fan enters the stall stage. Through in-depth investigation of unsteady flow characteristics under the hump point, it is found that after experiencing the emerging spike, with the sharp increase of incidence angle, some flow distortions appear on the intake surface, and further induce some flow paths to form stall vortices. When a path goes into stall stage, the airflow state is greatly affected, the inverse flow and air separation phenomenon in the rim region increase significantly, and the flow capacity decreases significantly, so the flow capacity in the hub region increases correspondingly. The flow path distortion of tip leakage flow (TLF) and leading edge (LE) spillage caused by the stall vortices are the main inducements of rotating stall.

Spike and Modal Stall Inception Patterns in a Variable-pitch Axial-flow Fan

2003 ◽  
Vol 2003.2 (0) ◽  
pp. 27-28
Author(s):  
Takahiro NISHIOKA ◽  
Shuuji KURODA ◽  
Tadashi KOZU
Keyword(s):  
Axial Flow ◽  
Axial Flow Fan ◽  
Variable Pitch ◽  
Stall Inception

Improvement of Unstable Characteristics of an Axial Flow Fan by Air-Separator Equipment

1987 ◽  
Vol 109 (1) ◽  
pp. 36-40 ◽  
Author(s):  
Y. Miyake ◽  
T. Inaba ◽  
T. Kato
Keyword(s):  
Pressure Distribution ◽  
Axial Flow ◽  
Rotating Stall ◽  
Axial Flow Fan ◽  
Blade Passage ◽  
Geometric Conditions ◽  
Different Types ◽  
Blade Tip ◽  
Discharge Distribution ◽  
Air Separator

The authors’ previous papers demonstrated that an air-separator is the most effective equipment among various different types for the improvement of unstable characteristics of an axial-flow rotor. Further experiments revealed that this equipment could eliminate the unstable characteristics thoroughly even for a build which originally accompanied a heavy rotating stall. This paper describes the geometric conditions to realize this and discusses its performance mechanism on the basis of the experiments showing the discharge distribution of the bleeding flow from the blade tip to separator passage as well as the pressure distribution in a blade passage at the tip section of the rotor. It is suggested that the equipment is equally useful at any stage of a multistage rotor.

Visualisation of rotating stall in an axial flow fan

2014 ◽  
Vol 53 ◽  
pp. 269-276 ◽  
Author(s):  
Matej Fike ◽  
Gorazd Bombek ◽  
Matjaž Hriberšek ◽  
Aleš Hribernik
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Axial Flow Fan

Influence of Rotating Instability on Stall Inception Patterns in a Variable-Pitch Axial-Flow Fan

2006 ◽  
Author(s):  
Takahiro Nishioka ◽  
Shuuji Kuroda ◽  
Tsukasa Nagano ◽  
Hiroshi Hayami
Keyword(s):  
Rotor Blade ◽  
Axial Flow ◽  
Pressure Rise ◽  
Leading Edge ◽  
Rotating Stall ◽  
Axial Flow Fan ◽  
Tip Leakage Vortex ◽  
Stall Inception ◽  
Tip Leakage ◽  
Stagger Angle

An experimental study was conducted to investigate the inception patterns of rotating stall at different rotor blade stagger-angle settings with the aim of extending the stable operating range for a variable-pitch axial-flow fan. Pressure and velocity fluctuations were measured for a low-speed axial-flow fan with a relatively large tip clearance. Two stagger-angle settings were tested, the design setting, and a high setting which was 10 degrees greater than the design setting. Rotating instability (RI) was first observed near the peak pressure-rise point at both settings. It propagated in the rotation direction at about 40 to 50% of the rotor rotation speed, and its wavelength was about one rotor-blade pitch. However, the stall-inception patterns differed between the two settings. At the design stagger-angle setting, leading edge separation occurred near the stall-inception point, and this separation induced a strong tip leakage vortex that moved upstream of the rotor. This leakage vortex simultaneously induced a spike and a RI. The conditions for stall inception were consistent with the simple model of the spike-type proposed by Camp and Day. At the high stagger-angle setting, leading edge separation did not occur, and the tip leakage vortex did not move upstream of the rotor. Therefore, a spike did not appear although RI developed at the maximum pressure-rise point. This RI induced a large end-wall blockage that extended into the entire blade passage downstream of the rotor. This large blockage rapidly increased the rotor blade loading and directly induced a long length-scale stall cell before a spike or modal disturbance appeared. The conditions for stall inception were not consistent with the simple models of the spike or modal-type. These findings indicate that the movement of the tip leakage vortex associated with the rotor blade loading affects the development of a spike and RI and that the inception pattern of a rotating stall depends on the stagger-angle setting of the rotor blades.

Sign in / Sign up

Export Citation Format

Share Document