Axial Fan Performance With Blade-Base Clearance

1984 ◽  
Vol 106 (4) ◽  
pp. 901-905
Author(s):  
T. Wright
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Axial Fan ◽  
Fan Performance

A study to evaluate the influence of increasing the clearance between blade and hub on a controllable pitch axial fan (CPAF) is presented. Fan performance was measured over a range of increasing clearance for several settings of blade pitch angles. The resulting variations of pressure rise, flow rate, and efficiency have been correlated as functions of established clearance parameters with good results. The study shows that large base clearances may result in reductions in efficiency and flow rate of 5 percent or greater in a typical CPAF configuration.

Axial Fan Performance With Blade-Base Clearance

1983 ◽  
Author(s):  
T. Wright
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Axial Fan ◽  
Fan Performance

A study to evaluate the influence of increasing the clearance between blade and hub on a controllable pitch axial fan (CPAF) is presented. Fan performance was measured over a range of increasing clearance for several settings of blade pitch angles. The resulting variations of pressure rise, flow rate and efficiency have been correlated as functions of established clearance parameters with good results. The study shows that large base clearances may result in reductions in efficiency and flow rate of 5 percent or greater in a typical CPAF configuration.

scholarly journals Effect of Two- and Three-Dimensionally Designed Guide Vanes with Different Camber Length on Static Pressure Recovery of a Wall-Mounted Axial Fan

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1595
Author(s):  
Yong-In Kim ◽  
Yong-Uk Choi ◽  
Cherl-Young Jeong ◽  
Kyoung-Yong Lee ◽  
Young-Seok Choi
Keyword(s):  
Flow Rate ◽  
Guide Vane ◽  
Dynamic Pressure ◽  
Pressure Rise ◽  
Design Flow ◽  
Low Flow ◽  
Axial Fan ◽  
Flow Angle ◽  
Numerical Effort ◽  
Vane Angle

This study was based on a numerical effort to use the motor support (prop) as a guide vane when the motor of a wall-mounted axial fan was located at the fan outlet while maintaining the structural and spatial advantage. The design for the guide vane followed two- and three-dimensional methods. The inlet vane angle, meridional length (total), and meridional length with a vane angle of zero (0) degrees (linear) were considered as design variables. At the design and some low flow rate points, the 2D design offered the most favorable performance when the meridional length with a vane angle of zero (0) degrees (linear) was 30% based on total length, and was the worst for 70%. The 3D design method applied in this study did not outperform the 2D design. In the 2D design concept, averaging the flow angle for the entire span at the design flow rate could ensure a better pressure rise over a more comprehensive flow rate range than weighting the flow angle for a specific span. In addition, the numerical results were validated through an experimental test, with an important discussion of the swirl (dynamic pressure) component. The influence of the inlet motor and turbulence model are presented as a previous confirmation.

Effects of Rotating Stall on an Axial Fan Design

2011 ◽  
Author(s):  
K. R. Wilt ◽  
D. Story ◽  
Henry A. Scarton ◽  
A. I. C. Hunter ◽  
S. A. Salamah ◽  
...  
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Rensselaer Polytechnic Institute ◽  
Rotating Stall ◽  
Test Facility ◽  
Frequency Content ◽  
Axial Fan ◽  
Physical Measurements ◽  
Before And After ◽  
Fan Cooling

This paper presents the physical measurements and analysis of data pertaining to rotating stall observed during testing at the GE fan test facility located at Rensselaer Polytechnic Institute. Although never detected in actual GE applications, the rotating stall was encountered while testing fan cooling blade prototypes used in electrical generators. The effects of this phenomenon on the flow rate and pressure rise across the fan are considered, along with the frequency content of the adjacent flows on either side of the fan. Further, the effects of the addition of flow constrictions before and after the fan on the behavior of the rotating stall are investigated.

Study on P-Q Curves of Cooling Fans for Thermal Design of Electronic Equipment (Effects of Opening Position of Obstructions Near a Fan)

2011 ◽  
Author(s):  
Takashi Fukue ◽  
Masaru Ishizuka ◽  
Tomoyuki Hatakeyama ◽  
Shinji Nakagawa ◽  
Katsuhiro Koizumi
Keyword(s):  
Flow Rate ◽  
Perforated Plate ◽  
Pressure Rise ◽  
High Density ◽  
Thermal Design ◽  
Electronic Equipment ◽  
Flow Passage ◽  
Fan Performance ◽  
Cooling Fan ◽  
Cooling Fans

This study describes an operation pressure and supplies flow rate of an axial cooling fan installed in high-density packaging electronic equipment. Fan performance is generally defined by their P-Q curve, specifically, a relationship between fan pressure rise (ΔP) and flow rate (Q). A compact cooling fan often operates in a high-density mounting device, which may decrease the fan performance. In this study, we focus on an obstruction near a fan, which is electronic components such as PCBs, capacitors and heat sinks, as one of a factor which decreases fan performance. We installed a perforated plate which simulated the above components near a fan and measured the P-Q curve. To investigate a relationship between a fan performance decrease and an opening position near the fan, a part of the perforated plate was closed. Closed position was changed and explored an opening condition which caused the dominant fan performance decrease. From experiments, it was found that the fan performance was decreased when flow passage in front of a fan was blocked by an obstruction. Especially, when flow passage in front of a fan hub was blocked, a dominantly reduction of fan pressure was caused. An obstruction rear a fan has no effect on a fan performance curve itself. In addition, opening conditions in front of a fan tip had a little influence on a fan pressure characteristic when there was no obstruction in front of a hub.

CFD - Based Investigation of Effects of Obstruction in Front of Small Axial Cooling Fan and Deterioration of Supply Flow Rate

2021 ◽  
Author(s):  
Tetsushi Fukuda ◽  
Yukio Masuda ◽  
Takashi Fukue ◽  
Yasuhiro Sugimoto ◽  
Tomoyuki Hatakeyama ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Pressure Rise ◽  
Leading Edge ◽  
Rotating Stall ◽  
High Density ◽  
Electronic Equipment ◽  
Fan Performance ◽  
Cooling Fan ◽  
High Density Packaging

Abstract This study describes the deterioration of a small axial fan’s supply flow rate in high-density packaging electronic equipment. A cooling fan flow rate can be predicted by its P-Q curve, which shows a relationship between a pressure rise at a fan (ΔP) and a supply flow rate (Q). However, in high-density packaging electronic equipment, the fan performance is affected by the mounting components around the fans, and the accurate prediction of the supply flow rate becomes difficult. This paper tried to do flow visualization around a small axial cooling fan’s impellers when the obstruction was mounted in front of the fan through CFD analysis. A relationship between the supply flow rate by the fan and the flow pattern around the impellers was investigated while changing the distance between the test fan and the obstruction. Through this study, the following results can be obtained. The fan’s flow is stable in the rotating stall region and the higher flow rate operating points regardless of whether or without the obstruction. At the lower flow rate conditions, the formation of a complex unsteady flow is reproduced. As the flow rate decreases, the flow’s separation point becomes closer to the leading edge of the impeller. In the case of obstruction, the change of the flow pattern causes a larger attack angle. As a result, fan performance is degraded.

Axial fan tip clearance noise: Experiments, Lattice–Boltzmann simulation, and mitigation measures

2018 ◽  
Vol 17 (1-2) ◽  
pp. 159-183 ◽  
Author(s):  
Tao Zhu ◽  
Thomas H Carolus
Keyword(s):  
Flow Rate ◽  
Lattice Boltzmann ◽  
Pressure Rise ◽  
Flow Simulation ◽  
Simulation Method ◽  
Design Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Mitigation Measures ◽  
Axial Fan

The effect of tip clearance in an axial fan on its aerodynamic and aeroacoustic performance is investigated experimentally as well as via a Lattice–Boltzmann flow simulation method. An increase in tip clearance degrades fan pressure rise and efficiency, but also increases significantly the overall sound power emitted by the fan. A large tip clearance causes a clear structure of well distinguishable unsteady vortices which interact with neighboring blades and hence produce an increase in broadband sound. Moreover, if, compared to the design flow rate, there is a moderate flow rate reduction, the local tip vortex systems of all individual blade tips form a circumferentially coherent flow structure, resulting in distinct humps of sound pressure in the acoustic far field. By means of a rigid ring-type protrusion fixed to the inner casing wall, the generation of the tip clearance vortices and slowly rotating coherent flow structures could be suppressed. As a consequence, the sound emitted by the fan is substantially reduced.

Studies on Downstream Stator With Rotor Re-Staggering and Forward Sweeping in a Subsonic Axial Compressor Stage

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
Computational Model ◽  
Flow Rate ◽  
Total Pressure ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Distance ◽  
Compressor Stage ◽  
Numerical Work ◽  
Stagger Angle

The present numerical work studies the flow field in subsonic axial compressor stator passages for: (a) preceding rotor sweep (b) preceding rotor re-staggering (three stagger angle changes: 0°, +3° and +5°); and (c) stator sweeping (two 20° forward sweep schemes). The following are the motives for the study: at the off-design conditions, compressor rotors are re-staggered to alleviate the stage mismatching by adjusting the rows to the operating flow incidence. Fundamental to this is the understanding of the effects of rotor re-staggering on the downstream component. Secondly, sweeping the rotor stages alters the axial distance between the successive rotor-stator stages and necessitates that the stator vanes must also be swept. To the best of the author’s knowledge, stator sweeping to suit such scenarios has not been reported. The computational model for the study utilizes well resolved hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: (1) When the rotor passage is closed by re-staggering, with the same mass flow rate and the same stator passage area, stators were subjected to negative incidences. (2) Effect of stator sweeping on the upstream rotor flow field is insignificant. Comparison of total pressure rise carried by the downstream stators suggests that an appropriate redesign of stator is essential to match with the swept rotors. (3) While sweeping the stator is not recommended, axial sweeping is preferable over true sweeping when it is necessary.

Surge in a Low-Speed Radial Compressor

1998 ◽  
Author(s):  
Corine Meuleman ◽  
Frank Willems ◽  
Rick de Lange ◽  
Bram de Jager
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Lumped Parameter Model ◽  
Pressure Oscillations ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Radial Compressor ◽  
Low Speed ◽  
Lumped Parameter

Surge is measured in a low-speed radial compressor with a vaned diffuser. For this system, the flow coefficient at surge is determined. This coefficient is a measure for the inducer inlet flow angle and is found to increase with increasing rotational speed. Moreover, the frequency and amplitude of the pressure oscillations during fully-developed surge are compared with results obtained with the Greitzer lumped parameter model. The measured surge frequency increases when the compressor mass flow is throttled to a smaller flow rate. Simulations show that the Greitzer model describes this relation reasonably well except for low rotational speeds. The predicted amplitude of the pressure rise oscillations is approximately two times too small when deep surge is met in the simulations. For classic surge, the agreement is worse. The amplitude is found to depend strongly on the shape of the compressor and throttle characteristic, which are not accurately known.

Fan Performance Scaling With Inlet Distortions

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
J. J. Defoe ◽  
M. Etemadi ◽  
D. K. Hall
Keyword(s):  
Design Flow ◽  
Flow Coefficient ◽  
Axial Fan ◽  
Fan Performance ◽  
Physical Mechanisms ◽  
Viscous Losses ◽  
Performance Scaling ◽  
Large Distortion ◽  
Stator Blade ◽  
Primary Focus

Applications such as boundary-layer-ingesting (BLI) fans and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. The objectives are to (1) identify the physical mechanisms which govern the fan response to inflow distortions and (2) determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The model does not include viscous losses so that changes in diffusion factor are the primary focus. Distortions in stagnation pressure and temperature as well as swirl are considered. The key findings are that unless sharp pitchwise gradients in the diffusion response, strong radial flows, or very large distortion magnitudes are present, the response of the blade rows for strong distortions can be predicted by scaling up the response to a weaker distortion. In addition, the response to distortions which are composed of nonuniformities in several inlet quantities can be predicted by summing up the responses to the constituent distortions.

Effect of Blade Angle of Attack and Hub to Tip Ratio on Mass Flow Rate in an Axial Fan at a Fixed Rotational Speed

2008 ◽  
Author(s):  
Mohammad J. Izadi ◽  
Alireza Falahat
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Angle Of Attack ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Maximum Mass ◽  
Blade Angle ◽  
Axial Fan

In this investigation an attempt is made to find the best hub to tip ratio, the maximum number of blades, and the best angle of attack of an axial fan with flat blades at a fixed rotational speed for a maximum mass flow rate in a steady and turbulent conditions. In this study the blade angles are varied from 30 to 70 degrees, the hub to tip ratio is varied from 0.2 to 0.4 and the number of blades are varied from 2 to 6 at a fixed hub rotational speed. The results show that, the maximum flow rate is achieved at a blade angle of attack of about 45 degrees for when the number of blades is set equal to 4 at most rotational velocities. The numerical results show that as the hub to tip ratio is decreased, the mass flow rate is increased. For a hub to tip ratio of 0.2, and an angle of attack around 45 degrees with 4 blades, a maximum mass flow rate is achieved.

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