scholarly journals Analytical and numerical investigation of the optimum pressure distribution along a low-pressure axial fan blade

2008 ◽  
Vol 223 (3) ◽  
pp. 643-657 ◽  
Author(s):  
M Pascu ◽  
M Miclea ◽  
P Epple ◽  
A Delgado ◽  
F Durst
Keyword(s):  
Total Pressure ◽  
Design Method ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Critical Parameters ◽  
Design Strategies ◽  
Axial Fan ◽  
Optimum Pressure ◽  
Absolute Increase ◽  
Fan Blade

In the field of axial flow turbomachines, the two-dimensional cascade model is often used experimentally or numerically to investigate fundamental flow characteristics and overall performance of the impeller. The core of the present work is a design method for axial fan cascades aiming to derive inversely the optimum blade shape based on the requirements of the impeller and not using any predefined aerofoil profiles. While most design strategies based on the aerofoil theory assume constant total pressure at all streamlines, i.e. free-vortex flow, this paper investigates the possibility of varying the total pressure along the blade and based on that, an analytical expression of the outlet blade angle is determined. When computing the blade profile at a specified radius, critical parameters reflecting on the flow characteristics are observed and adjusted (i.e. sufficient lift and controlled deceleration of the flow on the contour) so that the resulting profile is derived for minimum losses. The validation of this design strategy is given by the numerical results obtained when employed as an optimization tool for an industrial fan: 10–20 per cent absolute increase in the static efficiency of the optimized impeller.

Parmeterization of the Total Pressure Distribution Along a Low-Pressure Axial Fan Blade According to the Design Requirements

2008 ◽  
Author(s):  
Maria Pascu ◽  
Philipp Epple ◽  
Antonio Delgado ◽  
Franz Durst
Keyword(s):  
Total Pressure ◽  
Design Method ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Critical Parameters ◽  
Design Strategies ◽  
Axial Fan ◽  
Absolute Increase ◽  
Overall Performance ◽  
Fan Blade

In the field of axial flow turbomachines, the two–dimensional cascade model is often used experimentally or numerically to investigate fundamental flow characteristics and overall performance of the impeller. The core of the present work is a design method for axial fan cascades aiming to derive inversely the optimum blade shape based on the requirements of the impeller and not using any predefined airfoil profiles. While most design strategies based on the airfoil theory assume constant total pressure at all streamlines, i.e. free–vortex flow, this paper investigates the possibility of varying the total pressure along the blade and based on that, an analytical expression of the outlet blade angle is determined. When computing the blade profile at specified radius, critical parameters reflecting on the flow characteristics are observed and adjusted, i.e. sufficient lift and controlled deceleration of the flow on the contour so that the resulting profile is derived for minimum losses. The validation of this design strategy is given by the numerical results obtained when employed as an optimization tool for an industrial fan: 10–20% absolute increase in the efficiency of the optimized impeller.

A Simple Method for the Selection of Axial Fan Blade Profiles

1978 ◽  
Vol 192 (1) ◽  
pp. 269-275 ◽  
Author(s):  
N. Hay ◽  
R. Metcalfe ◽  
J. A. Reizes
Keyword(s):  
Design Method ◽  
Axial Flow ◽  
Operating Conditions ◽  
Angle Of Incidence ◽  
Axial Fan ◽  
Simple Method ◽  
Camber Angle ◽  
Fan Blade ◽  
Existing Data ◽  
Selection Of

Existing data on aerofoil sections suitable for axial flow fans are replotted on axes of angle of incidence against camber angle. The carpet plots so obtained permit the best operating conditions for each type of aerofoil to be immediately identified and thus the most suitable section can be easily selected for a given specification. A design method based on the use of these carpet plots is proposed and illustrated with a numerical example.

scholarly journals Preliminary Design Guidelines for Considering the Vibration and Noise of Low-Speed Axial Fans Due to Profile Vortex Shedding

2022 ◽  
Vol 7 (1) ◽  
pp. 2
Author(s):  
Gábor Daku ◽  
János Vad
Keyword(s):  
Vortex Shedding ◽  
Design Method ◽  
Axial Flow ◽  
Design Guidelines ◽  
Worst Case ◽  
Low Speed ◽  
Increased Risk ◽  
Axial Fans ◽  
Fan Blade ◽  
Set Up

This paper presents a critical overview on worst-case design scenarios for which low-speed axial flow fans may exhibit an increased risk of blade resonance due to profile vortex shedding. To set up a design example, a circular-arc-cambered plate of 8% relative curvature is investigated in twofold approaches of blade mechanics and aerodynamics. For these purposes, the frequency of the first bending mode of a plate of arbitrary circular camber is expressed by modeling the fan blade as a cantilever beam. Furthermore, an iterative blade design method is developed for checking the risky scenarios for which spanwise and spatially coherent shed vortices, stimulating pronounced vibration and noise, may occur. Coupling these two approaches, cases for vortex-induced blade resonance are set up. Opposing this basis, design guidelines are elaborated upon for avoiding such resonance. Based on the approach presented herein, guidelines are also developed for moderating the annoyance due to the vortex shedding noise.

Computation and Measurement of the Flow in Axial Flow Fans With Skewed Blades

1999 ◽  
Vol 121 (1) ◽  
pp. 59-66 ◽  
Author(s):  
M. G. Beiler ◽  
T. H. Carolus
Keyword(s):  
Total Pressure ◽  
Design Method ◽  
Power Level ◽  
Three Dimensional ◽  
Axial Flow ◽  
Pressure Rise ◽  
Fast Response ◽  
Test Facility ◽  
Navier Stokes ◽  
Pressure Probe

A numerical analysis of the flow in axial flow fans with skewed blades has been conducted to study the three-dimensional flow phenomena pertaining to this type of blade shape. The particular fans have a low pressure rise and are designed without stator. Initial studies focused on blades skewed in the circumferential direction, followed by investigations of blades swept in the direction of the blade chord. A Navier–Stokes code was used to investigate the flow. The simulation results of several fans were validated experimentally. The three-dimensional velocity field was measured in the fixed frame of reference with a triple sensor hot-film probe. Total pressure distribution measurements were performed with a fast response total pressure probe. The results were analyzed, leading to a design method for fans with swept blades. Forward swept fans designed accordingly exhibited good aerodynamic performance. The sound power level, measured on an acoustic fan test facility, improved.

Experimental Study of the Effect of Serrations on Axial Flow Fan Blade Trailing Edge

2016 ◽  
Author(s):  
Dhyanjyoti Deb Nath ◽  
K. Viswanath ◽  
Ankit Bhai Patel
Keyword(s):  
Axial Velocity ◽  
Pressure Sensors ◽  
Tangential Velocity ◽  
Axial Flow ◽  
Experimental Investigations ◽  
Spanwise Direction ◽  
Axial Fan ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Fan Blade

Rotor wakes shed from a compressor rotor impinge on downstream blades and is a major source of rotor-stator interaction noise and much research has been dedicated on wake attenuation. Serrated trailing edges is one such wake attenuation technique where the vortices produced at the serrated trailing edges enhance mixing and create a more uniform flow at stator inlet. The present paper investigates the effect of serrations on the trailing edge of a forced vortex axial fan blade. Experimental investigations were carried out at rotor outlet using pneumatic probes and fast response pressure sensors. It is found that total and static pressures reduce in serrated blades due to reduced turning and hence reduced work input. The absolute tangential velocity wake deficit decreases in serration valleys and improvement in axial velocity wake deficit is also found. Improvements as large as 19% and 18% decrease in absolute tangential velocity and axial velocity wake deficit are found at certain radii. The spanwise shape of the wake is altered by the serrations and a wake pattern undulating in the spanwise direction is observed. These are expected to bring down the circumferential variation of the velocity and its phase before entering the next row of blades and bring down the tonal noise.

scholarly journals Energy Efficiency Optimization Design of a Forward-Swept Axial Flow Fan for Heat Pump

2021 ◽  
Vol 9 ◽  
Author(s):  
Ke Yang ◽  
Shuiqing Zhou ◽  
Yinjie Hu ◽  
Huaxin Zhou ◽  
Weiya Jin
Keyword(s):  
Heat Pump ◽  
Flow Rate ◽  
Total Pressure ◽  
Optimization Design ◽  
Axial Flow ◽  
Kriging Model ◽  
Axial Fan ◽  
Nsga Ii ◽  
Pump System ◽  
Heat Pump System

As one of the key components of the heat pump system, compared to that of a conventional axial fan, the blade tip area of a forward-swept axial fan is much larger than its blade root, which is the main noise source of the fan and also has an important influence on the fan efficiency. Enhancement of the aerodynamic performance and efficiency of a forward-swept axial fan was addressed by utilizing the Bezier function to parameterize the forward-swept curve on blade tops. In order to quickly select an agent model suitable for the project, an ES model was established by integration of the radial basis function model and the Kriging model. When NSGA-II was combined, multi-objective optimization was carried out with the flow rate and total pressure efficiency as optimization goals. Analysis of optimization results revealed that the optimized axial flow fan’s flow rate and total pressure efficiency were improved to some degree. At the design working point, the fan’s flow rate increased by 1.78 m³/min, while the total pressure efficiency increased by 3.0%. These results lay solid foundation for energy saving of the heat pump system.

scholarly journals Influence of Chord Lengths of Splitter Blades on Performance of Small Axial Flow Fan

2015 ◽  
Vol 9 (1) ◽  
pp. 361-370
Author(s):  
Guoqi Li ◽  
Lifu Zhu ◽  
Yongjun Hu ◽  
Yingzi Jin ◽  
Toshiaki Setoguchi ◽  
...  
Keyword(s):  
Flow Characteristics ◽  
Axial Flow ◽  
Internal Flow ◽  
Leading Edge ◽  
Chord Length ◽  
Aerodynamic Noise ◽  
Axial Fan ◽  
Axial Flow Fan ◽  
Suction Surface ◽  
Small Axial Flow Fan

On the basis of small axial fan with five blades, 6 types of small axial flow fans with different chord lengths splitter blades were designed. Numerical simulation of 6 fan models with splitter blades and prototype fan were done by using Fluent. Based on the obtained simulation results, internal flow characteristics and aerodynamic noise were analyzed and compared. It indicates that: splitter blades with suitable chord length have improved significantly on internal flow characteristics, which inhibits backflow from pressure surface to the suction surface at blade tip and leading edge and restrains flow separation. The 6 model fans are better than prototype fan on aerodynamic noise improvement, but too long or too short chord lengths are both disadvantage to improve aerodynamic noise. The results reveal that 2/6, 3/6 and 4/6 chord length model have relatively better acoustic characteristics and internal flow characteristics. The research program will offer a reference for structural improvements and noise reduction on small axial flow fan.

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

2006 ◽  
Author(s):  
Nikhil M. Rao ◽  
Baris Gumusel ◽  
Levent Kavurmacioglu ◽  
Cengiz Camci
Keyword(s):  
Total Pressure ◽  
Large Scale ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Pressure Probe ◽  
Tip Leakage Flow ◽  
Equivalent Thickness ◽  
High Frequency Response

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.

Inlet Box Structure Optimization of a Large Axial-Flow Fan Using Response Surface Methodology

2020 ◽  
Author(s):  
Jin Xiong ◽  
Yinkun Zhang ◽  
Penghua Guo ◽  
Jingyin Li
Keyword(s):  
Total Pressure ◽  
Design Method ◽  
Orthogonal Design ◽  
Axial Flow ◽  
Pressure Rise ◽  
Aerodynamic Performance ◽  
Design System ◽  
Orthogonal Design Method ◽  
Box Structure ◽  
Inlet Box

Abstract Large axial-flow fans are widely used in many fields. The inlet box is an integral part of large axial-flow fans, and a well-designed inlet box could effectively improve fan efficiency. However, the inlet box structure is complicated, and the existing inlet box design method severely depends on the design experience. In this study, we propose a structure optimization design system based on a surrogate model technique for researching the critical structure parameters of the inlet box and accomplishing aerodynamic performance optimization. As for this expensive optimization problem, the design system contains twice optimization procedures by using the Response Surface Methodology (RSM) with the orthogonal design method. The optimization object is an existing large axial-flow fan. The optimization objective is the total pressure efficiency of the fan, and the total pressure rise is the restriction condition. We generate eighteen different inlet boxes connect with the same impeller and outlet pipe by the orthogonal design method and calculated fan aerodynamic performance by CFX software. After the first optimization, we find the key structural parameters by the sensitivity analysis and the reselect variables total of 25 cases are adopted in a further RSM optimal process. The ultimate surrogate model estimates the fan with the optimal inlet box has a better aerodynamic characteristic and a 6.7% total pressure efficiency rise. Finally, we compare the aerodynamic characteristics of the ultimate design fan and the initial fan by CFD simulation. The numerical results show that: the total pressure efficiency is 6.5% higher than that of the initial impeller, and the pressure rise is 3% higher than that of the initial impeller. The result demonstrates that some most critical parameters of the inlet box structure decide the aerodynamic performance, and the inlet box optimization effectively increases the fan efficiency in the meanwhile.

scholarly journals Experimental investigations of the turbulent swirl flow in straight conical diffusers with various angles

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 725-736 ◽  
Author(s):  
Dejan Ilic ◽  
Miroslav Benisek ◽  
Djordje Cantrak
Keyword(s):  
Flow Parameter ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Swirl Flow ◽  
Experimental Investigations ◽  
Axial Fan ◽  
Flow Loss ◽  
Inlet Swirl ◽  
Loss Coefficients ◽  
Total Divergence

Results of experimental investigations of the turbulent swirl flow in three straight conical diffusers with various diffuser total angles are presented in this paper. All three diffusers have the inlet diameter 0.4 m and total divergence angles 8.6?, 10.5?, and 12.6?. The incompressible swirl flow field is generated by the axial fan impeller, and for each diffuser several regimes were achieved by changing rotation number. Original classical probes were used for measurements. The distributions of the average main swirl flow characteristics along the diffuser are shown. Distributions of the inlet Boussinesq number, outlet Coriolis coefficient, ratio of the swirl and completely axial flow loss coefficients at conical diffuser on the inlet swirl flow parameter are also presented.

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