Conference on Modelling Fluid Flow (CMFF’06)
The 13th International Conference on Fluid Flow Technologies
Budapest, Hungary, September 6-9, 2006
DEVELOPMENT OF IMPROVED BLADE TIP END-PLATE CONCEPTS FOR
LOW-NOISE OPERATION IN INDUSTRIAL FANS
Alessandro CORSINI1, Franco RISPOLI2, A. Geoff SHEARD3
Corresponding Author. Dipartimento di Meccanica e Aeronautica, University of Rome “La Sapienza”. Via Eudossiana 18, I00184
Rome, Italy. Tel.: +39 06 44585231, Fax: +39 06 4881759, E-mail: alessandro.corsini@uniroma1.it
2
Dipartimento di Meccanica e Aeronautica, University of Rome “La Sapienza”. E-mail: franco.rispoli@uniroma1.it
3
Fläkt Woods Ltd. E-mail: geoff.sheard@Fläktwoods.com
1
ABSTRACT
The use of improved blade tip geometries is
addressed as an effective design concept for passive
noise control in industrial fans. These concepts,
based on geometrical modifications of datum blade
by means of profiled end-plates at the tip, are
shown to reduce fan noise in its tonal and
broadband components by changing the tip leakage
flow behaviour. The three dimensional structures of
tip vortical flow fields are discussed for a family of
axial fans in fully-ducted configuration, to
investigate on the aerodynamics of the proposed
blade tip concepts. The study has been carried-out
using an accurate in-house developed parallel finite
element RANS solver, with the adoption of nonisotropic two-equation turbulence closure. The
nature of the flow mechanisms in the fan tip region
is correlated to the specific blade design features
that promote reduced aerodynamic noise. It was
found that the tip geometrical modifications
markedly affect the multiple vortex leakage flow
behaviours, by altering the turbulence and velocity
fluctuations in the near-wall region as well along
the blade span. The tip end-plates were
demonstrated to influence also the rotor loss
behaviour, in the blade tip region. The improvement
of rotor efficiency curves were assessed and
correlated to the control of tip leakage flows
exploited by the tip end-plates.
Keywords: industrial
leakage flow, noise
fans,
end-plates,
NOMENCLATURE
Latin letters
k
[m2/s2] turbulent kinetic energy
l.e.
leading edge
PS
pressure side
P
[Pa]
static pressure
r
[mm] radius
SS
suction side
tip
t.e.
Uc
[m/s]
v, w [m/s]
x, y, z
Greek letters

[deg]

[m2/s3]

[-]

[-]

[-]
i
[s-1]
s
[-]
trailing edge
casing relative peripheral velocity
absolute and relative velocities
Cartesian coordinates


[-]
[-]


[-]
[-]
blade solidity
global flow coefficient (annulus
area-averaged
axial
velocity
normalised by Uc)
rotor tipclearance
pressure rise coefficient (p/(0.5
stagger angle
turbulent dissipation rate
2
total loss coefficient, p0in  p0 0.5  win
efficiency
hub-to-casing diameter ratio
absolute vorticity vector
absolute
streamwise
vorticity,
s  (i  wi ) /(2 w ) 
2
U c ))

[rad/s] rotor angular velocity
Subscripts and superscripts
a, p, r
axial, peripheral and radial
c
casing wall
h
hub wall
i
Cartesian component index
in
inlet section
s
streamwise component
pitch-averaged value
1. INTRODUCTION
Often in axial flow fans the design
specifications demand large tip gap according to the
requirements of operating with variable stagger or
pitch angles, e.g. cooling fans, or in some cases for
emergency operation at up to 400°C for two hours
to extract smoke in the event of a fire, e.g.
ventilating fans. As well known, the tip clearance
plays a detrimental role affecting the rotor aerodynamics (Fukano and Takamatsu, 1986), (Storer
and Cumpsty, 1991), (Furukawa et al., 1999), and,
as a number of studies pointed out, significantly
contributing to the aero-acoustic signature of
impeller in low speed ventilating equipments. In
this pictures the tip clearance flow is recognized to
inflence the rotor noise spectra by discrete
frequency noise due to periodic velocity fluctuation
and a broadband or high-frequency noise due to
velocity fluctuation in the blade passage (Fukano
and Jang, 2004) (Jang et al., 2003) (Quinlan and
Bent, 1998). To this end there is a strong motivation
to look for deliberate aerodynamic design in order
to minimize the negative effects of tip gap and to
manage the fan or compressor tip clearance flow to
minimize its impact on performance. Thus
techniques and concepts that help to reduce tip
clearance noise without sacrificing aerodynamic
efficiency are highly desired and needed.
By surveying the techniques to control the noise
of fans and compressors, it was found that the
proposed solutions could be grouped into active and
passive noise control techniques, conceptually
designed to accomplish this goal by reducing the
leakage flow rate or by enhancing the primarysecondary flow momentum transfer.
In the ambit of active control techniques for fans
and compressors, recently a number of experimental
studies reconsider the tip clearance flow control by
means of fluid injection on the casing wall in axial
compressor (Bae et al., 2005), and low-speed axial
flow fan (Roy, et al., 2005).
As far as the passive control techniques are
concerned, the literature review puts in evidence the
role of three approaches respectively focused on
three-dimensional blade design and on geometrical
modifications of the equipments in the gap region.
The first concept makes use of sweep technique in
blade design, recognized as a remedial strategy to
improve the aerodynamic limits in compressor and
low-speed axial fan rotors owing to the capability of
affecting the rotor stall margin by reducing
secondary flows effects and the flow leakage over
the blade tip (Wadia et al., 1997), (Corsini and
Rispoli, 2004), (Corsini et al., 2004). A second
family of control technique based on gap
geometrical manipulation, the use of casing
treatments in the shroud portion over the blade tip
which is reported since the early 70s to improve the
stable flow range by weakening the tip leakage
vortex. Noticeable contributions deal with the use
of grooves and slots (Takata and Tsukuda, 1977)
(Smith and Cumpsty, 1984), or stepped tip gaps
(Thompson et al., 1998). Furthermore, in the ambit
of fan technologies recirculating vanes, and annular
rings have been proposed as anti-stall devices
(Jensen, 1986). As a final tip treatment solution,
during the last decade, has been proposed the blade
tip modifications by means of anti-vortex
appendices such as the end-plates investigated by
Quinlan and Bent (1998), or the solutions recently
proposed by industrial patents for small ventilating
fans (pat. ???) (pat. ???) (pat. ???).
In this respect, the present paper aims to
investigate on the use of profiled end-plates at the
blade tip (Corsini et al., 2006). The study focuses
on a family of commercially available fans and
compares the aerodynamic and aeroacoustic
performance of the datum blade against two
improved tip geometries, respectively with constant
(rep. FW) or variable thickness end-plate (Corsini,
2006)
The objective of the paper is to report on the
experimental and numerical assessment of the payoff derived from the blade tip concept developed at
Fläkt Woods Ltd with respect to the aerodynamic
performance of a class of low noise level industrial
fans. The single rotor investigations are carried out
at design and off-design conditions for two
configurations of the six-blade axial flow fan under
investigation, namely: the datum fan, code AC90/6;
the fan modified with the tip feature, code
AC90/6/TF. The studies have been carried in ducted
configuration, adopting a high tip pitch angle
configuration, i.e. 28 degrees, where the fan
provides the higher static pressure and flow rate of
its operational range.
The comparative aerodynamic performance
experiments have been carried out according to ISO
5801 for type D fully ducted configuration set-up.
The noise performance test have been carried out in
accordance with the British Standard BS484, Part 2
for outlet noise hemispeherical measurement. The
fans have been tested employing a type A
configuration, in the Fläkt Woods Ltd anechoic
chamber at the design operating conditions.
The tip flow characteristics are analysed by
using a three-dimensional (3D) steady ReynoldsAveraged Navier-Stokes (RANS) formulation, with
use of first order non-isotropic turbulence closure
successfully validated for fan rotor flows (Corsini et
al, 2003), (Corsini and Rispoli, 2005). Despite the
steady-state condition, the RANS is considered an
effective investigation tool for vortical structure
detection (Inoue and Furukawa, 2002). The authors
adopt a parallel multi-grid (MG) scheme developed
for the in-house finite element method (FEM) code
(Borello et al., 2002). The FEM formulation is
based on a highly accurate stabilized PetrovGalerkin (PG) scheme, modified for application to
3D with equal-order spaces of approximation.
By means of such a numerical investigation, the
tip leakage flow structures of the fans are analysed
in terms of vortical structures detection, leakage
flow energy and loss behaviours. Emphasis is laid
on the assessment of the benefits related to the
improved tip geometry in terms of efficiency and
operating margin gains. The overall objective is to
investigate, via steady computational simulations,
the technical merits of a passive control strategy for
controlling the leakage flow and reducing tip
clearance vortex/stator interaction noise and rotortip self noise.
scale, the thickness distributions of the developed
improved tip concepts against the datum base-line.
2. TEST APPARATUS AND PROCEDURES
2.1. Test fans
The present study was performed on a family of
commercially available highly efficient cooling
fans. The in service experiences indicated that this
family of fans gives good acoustic performance
with respect to the state-of-the-art configurations.
The investigated fans have six-blade unswept rotor,
with blade profiles of modified ARA-D geometry
type originally designed for propeller applications.
The blade profiles geometry is given in Table 1, for
the datum fan AC90/6 at the hub, and tip sections
respectively.
Table 1 AC90/6 fan family specifications. Blade
profile geometry and rotor specifications.
AC90/6 fans
blade geometry
hub
tip
/t
1.32
0.31
(deg)
36
28
camber angle (deg)
46
41
pitch angle
fan rotor
blade number
6
blade tip pitch angle (deg)
28
hub-to-

tip diameter (mm)
0.22
900.0
 (% span)
rated rotational frequency (rpm)
1.0
900 – 935
The studied blade configurations, for datum
and modified rotors, feature a high tip stagger
angle, i.e. 28 degrees, measured, as is customary in
industrial fan practice, from the peripheral
direction.
This rotor angular setting has been chosen in
order to exploit operating points where the vortical
flow near the rotor tip dramatically affects the
aerodynamic performance and noise characteristics
of the investigated fans.
The fan blades are drawn in Figure 1, together
with a detailed view of blade tip for the datum rotor,
and the improved rotors developed for low noise
emission labeled: AC90/6/TF and AC90/6/TFvte.
Figure 1 compares, in a qualitative view not to
datum
AC90/6/TF
AC90/6/TFvte
Fig. 1 Test fans and rotor blades (not to scale)
The improved blade tip geometry, for
AC90/6/TF fans, was originally inspired by the
technique developed for tip vortex control and
induced drag reduction by preventing 3D flows in
aircraft wings, also used as anti-vortex devices for
catamaran hulls. The tip blade section was modified
by adding an end-plate along the blade pressure
surface that ends on the blade trailing edge with a
square tail. By means of the introduction of the endplate, the blade section is locally thickened of a
factor 3:1 with respect to the maximum thickness at
the tip of datum blade. According to the theory
behind the end-plate design, this dimension was
chosen as the reference radial dimension of leakage
vortex to be controlled that could be estimated in
the range 0.2  0.1 blade span, as shown by former
studies on rotors of axial compressor (Inoue et al.,
1986) and fan (Corsini et al., 2004). A recent
investigation, carried out by Corsini and co-workers
(2006),
assessed
the
aerodynamics
and
aeroacoustics gains of rotor AC90/6/TF with
respect to the datum one. Nonetheless, the
numerical simulation also founded the evidences of
a tip leakage vortex breakdown affecting rotor
AC90/6/TF at the design operating condition. To
this end the AC90/6/TFvte blade tip geometry has
been proposed that exploits a variable thickness
distribution of the end-plate according to safe
rotation number chord-wise gradient concept
(Corsini, 2006).
2.2. Numerical procedure and axial fan
modeling
The Reynolds-averaged Navier-Stokes equations
are solved by an original parallel Multi-Grid Finite
Element flow solver [13]. The physics involved in
the fluid dynamics of incompressible 3D turbulent
flows in rotating frame of reference, was modelled
with a non-linear k- model [14], here used in its
topology-free
low-Reynolds
variant.
This
turbulence closure has been successfully validated
on transitional compressor cascade flows, as well as
high-pressure industrial fan rotors [15 - 16].
The numerical integration of PDEs is based on
a consistent stabilised Petrov-Galerkin formulation
developed and applied to control the instability
origins that affect the advective-diffusive
incompressible flow limits, and the reaction of
momentum and turbulent scale determining
equations. The latter ones, respectively, related to
the
Coriolis
acceleration
or
to
the
dissipation/destruction terms in the turbulent scale
determining equations [17]. Equal-order linear
interpolation spaces (Q1-Q1) are used for primaryturbulent and constrained variables, implicitly
eliminating
the
undesirable
pressurecheckerboarding effects. Concerning the solution
strategy, a hybrid full linear MG accelerator was
built-in the in-house made overlapping parallel
solver.
The
Krylov
iterations
in
the
smoothing/solving MG phases are parallelized
using an original additive domain decomposition
algorithm. The message passing operations were
managed using the MPI libraries. By that way, the
fully coupled solution of sub-domain problem
involves an efficient non-conventional use of
Krylov sub-space methods. The preconditioned
GMRes(5) and GMRes(50) algorithms were
respectively used as smoother and core solver.
l.e.
t.e.
rotor hub
Fig. 2 Computational grid of fan rotor, mesh
details in the tip gap region
The mesh has been built according to a nonorthogonal body fitted coordinate system, by
merging two structured H-type grid systems. The
mesh in the main flow region, surrounding the
blade, and an embedded mesh in the tip gap region.
The mesh has 1546858 nodes, respectively in the
axial, pitch, and span wise directions. In the axial
direction the node distribution consists of 20%,
50% and 30% of nodes respectively upstream the
leading edge, in the blade passage and downstream
of it. Moreover, there are 14 grid nodes to model
the tip-clearance along the span. The computational
grid is illustrated, in Figure 2, providing detailed
view at the tip of the mesh in meridional and bladeto-blade surfaces.
The mesh has an adequate stretch toward solid
boundaries, with the ratio of minimum grid spacing
on solid walls to mid-span blade chord set as 2 103
on the blade tip, casing wall, and blade surfaces.
The adopted grid refinement towards the solid
surfaces controls the dimensionless distance +
value about 1 on the first nodes row.
2.3. Boundary conditions and investigated
flow conditions
Standard boundary condition set has been adopted,
already used in recent numerical studies on high
performance fans (Corsini and Rispoli, 2004)
(Corsini et al., 2004).
The Dirichlet conditions for the relative velocity
components are imposed at the inflow section half a
mid-span chord far upstream the leading edge. The
velocity profile has been obtained from flow
simulation in an annular passage of identical hubto-casing diameter ratio that includes an upstream
spinner cone. The inlet distribution of the turbulent
kinetic energy k is obtained from axi-symmetric
turbulence intensity (TI) profile derived on the basis
of former studies on ducted industrial fans (Corsini
and Rispoli, 2004). The TI profile features a nearly
uniform value in the core region (about 6 percent)
and it grows markedly approaching the endwalls
(about 10 percent). The inlet profile of turbulence
energy dissipation rate is basedon the characteristic
length scale l set to 0.01 of rotor pitch at mid-span.
Flow periodicity upstream and downstream the
blading, and Neumann outflow conditions
(homogeneous for k and  and non-homogeneous
for the static pressure) complete the set of boundary
data.
The numerical investigation compares fan
leakage flow patterns for datum, AC90/6/TF and
AC90/6/TFvte fan rotors operated in near-design
condition (D) with volume flow rate 7 m3/s and
global flow coefficient  = 0.278. The Reynolds
number based on tip diameter and rotor tip speed is
8.3 105, for normal air condition.
3. PERFORMANCE EXPERIMENTS
The aerodynamic and noise performance tests
were carried out at Fläkt Woods Ltd laboratory in
Colchester.
3.1. Aerodynamic tests
The aerodynamic tests were conducted
according to ISO 5801 set up, for fully ducted
configuration and installation type D. This
installation features ducted inlet and outlet regions
and the fan is supplied with a properly-shaped inlet
bell mouth. The primary performance parameters
measured were the fan static pressure and the
efficiency. Fig. 3 compares the static pressure and
efficiency characteristic curves for datum and
AC90/6/TF rotors.
The analysis of static pressure curves of Figure
3, gives the evidence of a small performance
reduction in rotor AC90/6/TF with improved tip
concept, e.g. about 2% at 6m3/s ADD
interpretation of performance reduction TE06.
On the other hand, rotor AC90/6/TF shows an
efficiency improvement in the range of volume flow
rate higher than the design one. In terms of peak
value, the AC90/6/TF rotor features a 72.9%
efficiency with a 1.25% of improvement. Moreover
the efficiency curve comparison gives evidence that
the adoption of the improved tip concept results in
the appearance of an efficiency plateau that shift the
peak  volume flow rate towards the rotor stall
margin.
angle, where the blades of this fan are the most
loaded and more readily prone to flow separation.
Table 2 Predicted and measured fan overall
performance
Measurements
pstat
datum
AC90/6/TF
AC90/6/TFvte
(Pa)
134.8
126.2
133.3
Predictions

pstat

0.490
0.510
0.486
(Pa)
133.3
126.1
126.1
0.510
0.504
0.504
It is also worth noting that the prediction of
performance parameters have been referred to axial
sections respectively located at the inlet of the
domain, and 1.2 midspan chord downstream the
blade trailing edge. The comparison confirms the
validity of the predicted performance.
3.2. Noise tests
The noise performance test have been carried
out in accordance with the British Standard BS484,
employing a type A testing configuration.
100
dB
datum
datum
AC90/6/TF
AC90/6/TF
AC90/6/TFvte
AC/90/6/TFvte
95
250
p(Pa)
90
85
200
80
75
150
250
70
65
100
200
60
55
150
50
80
50
a)
D

100
0
704
5
6
7
10
2
10
3
10
frequency (Hz)
4
100
8
95
datum
datum
AC90/6/TF
AC90/6/TF
AC90/6/TFvte
AC/90/6/TFvte
dB(A)
90
85
50
80
60
75
0
4
50
70
5
6
7
8
volume flow (m3/s)
65
Fig. 3 Static pressure and efficiency characteristic
curves (dashed lines: datum fan; solid lines:
60
40
AC90/6/TF fan; line-symbols: AC90/6/TFvte fan)
50
The rotor performance were assessed along the
operating
line. The predicted overall performance
30
8
for4 900 rpm5rotational6 frequency7 are compared
in
Table 2 to the experimental data measured at Fläkt
Woods Ltd measurements according to the fan
performance test standards ISO5801:1997 for
installations type D with inlet bell-mouth.
Efficiency  is computed in terms of static
pressure rise. The comparison confirms the validity
of the predicted performance at the chosen setting
45
55
40
35
30
b)
10
2
10
3
frequency (Hz)
10
4
Fig. 3 Sound power level spectra in one-thirdoctave band. a) un-weighted spectra and b) Aweighted spectra
(dashed lines: datum fan; solid lines: AC90/6/TF fan;
line-symbols: AC90/6/TFvte fan)
In this method the fan is placed downstream of
a plenum chamber with a free outlet, in an
arrangement similar to that used for compact
cooling fans.
Figure 4 compares the measured power spectra
in one-third-octave band. Fig. 4.a and Fig. 4.b
respectively show the measured sound power level
and the A-weighted sound power level spectra for
the frequency-dependent human audition. The noise
tests have been done in order to compare the rotors
aeroacoustic signature for identical static pressure
rise, e.g. 190 Pa close to the peak pressure
operation. As shown in Fig. 4, the effectiveness of
the improved tip concept is demonstrated by the
reduction of the rotor aeroacoustic signature both in
terms of tonal noise and broad-band noise. These
noise components are related to the main
recognized tip noise generation mechanisms in axial
decelerating turbomachinery. The convection of the
primary tip vortex and its interaction with the
statoric structures produces mainly tonal noise,
while the oscillating tip vortex behaviour could be
linked to the production of broadband selfgenerated noise (Khourrami and Choudari, 2001).
ADD
coments
on
the
compaative
performance
Finally, Table 3 compares the overall soud
power levels for the family of fans under
investigation, for
4.1. Helicity distributions and vortex cores
The tip leakage vortical structures are now
investigated by using the normalized helicity Hn
(Furukawa et al. 1998) (Inoue and Furukawa, 2002)
as the detection tool. Hn is defined and normalized
as: H n  i  wi  /   w  with i = 1, 3, where i
and wi are the Cartesian components of the absolute
vorticity and relative velocity vectors,  and w
their norms. The absolute vorticity is used because
the secondary flows in the rotor frame of reference
are dominated by the advection of its components
along the local relative flow directions. Figure 8
shows the normalized helicity distribution in the
blade tip region by comparing the contours on cross
flow planes in near-design operating condition. The
probing planes are located, respectively, at 0.25,
0.43, 0.65, 0.89 and 1.2 blade chord  from the tip
section leading edge. The normalized helicity
distribution is plotted with the vortex cores colored
by the its local magnitude.
For both the investigated fan rotors, a clear
vortex cores identification is only observed for the
leakage flow structures emerging in the front
portion of the tip blade sections. In the multiple
vortex behaviour of datum fan rotor, Fig. 8.a, the
helicity field shows that the main vortical structure
TLV1 develops as a clock-wise vortex with a high
skewing angle with respect to the blade surface.
Table 3 Overall sound power levels @ 190 Pa
datum
AC90/6/TF
AC90/6/TFvte
un-weighted SWL
dB
A-weighted SWL
dB(A)
94.6
93.0
91.5
88.7
86.3
88.1
ADD
coments
performance
on
the
Fig. 4 Normalized helicity Hn contours on cross
sections and vortex cores at the tip, D operating
point: a) datum rotor, b) AC90/6/TF rotor, and
c) AC90/6/TFvte
compaative
4. INNER WORKINGS OF END-PLATES
In axial decelerating turbomachines, the
distinctive feature of the tip clearance flow structure
is classically the occurrence of a roll-up into a tip
leakage vortex (Inoue and Furukawa, 2002). This
prompted a comparative investigation onto the
presence and structure of the tip leakage vortex and
other systems of secondary vorticities for the datum
fan and the fan with blade tip feature. The
effectiveness of the passive tip device is analysed
by comparing the static pressure fields within the
gap, the normalized stream wise vorticity map
chordwise evolution, and the tip vortex core paths.
These analyses are complemented with the
evalutaion of tip leakage flow energy contents,
affecting the rotor aeroacoustic signatures, and with
the presentation of loss coefficient map evolution
within the blade passage to assess the influence of
the geometrical modification at the blade tip and the
rotor aerodynamic efficiency along in operating
range of the fans. ADD
Fig. 5 Comparison of tip vortex trajectories
4.2. Leakage flow energy
Fig. 6 Rotational kinetic energy isolines in the
rotor tip gap @ R = 0.998, D operating point: a)
datum rotor, b) AC90/6/TF rotor, and c)
AC90/6/TFvte
Fig. 7 Turbulence intensity TI contours on cross
sections and tip vortex streamlines, D operating
point: a) datum rotor, b) AC90/6/TF rotor, and
c) AC90/6/TFvte
4.3. Loss at the rotor tip
Fig. 8 Evolution of total pressure loss coefficient
 inside the blade passage: a) datum rotor, b)
AC90/6/TF rotor, and c) AC90/6/TFvte
5. CONCLUSIONS
It is compulsory to summarise the results
discussed in the paper.
6. SUMMARY
It is compulsory to summarise the results
discussed in the paper.
ACKNOWLEDGEMENTS
The present research was done in the context of
the contract FW-DMA03, between Flakt Woods Ltd
and Dipartimento di Meccanica e Aeronautica
University of Rome “La Sapienza”. The authors
gratefully acknowledge Mr. I. Kinghorn and Mr. B.
Perugini for their contribution to the experiments.
REFERENCES
No numbering in the title (of Style “Heading
1”) is applied.
References must be included at the end of the
paper, in the order to which they have been referred
in the text. Examples for the format of references in
the body of the paper: [1] or [1, 2] or [1-9]. (The
latter is to be used when simultaneously more than
two references are referred to.) Names of the
authors of a reference can be emphasized in the
body of the text if necessary. For example:
“Recently, Corsini et al. [12]…”.
Examples for format of references in the
reference list, using the basic format of the Style
“References”, are as follows.
[1] Beiler, M. G., and Carolus, T.H., 1999,
“Computation and Measurement of the Flow in
Axial Flow Fans with Skewed Blades”, ASME J
Turbomachinery, Vol. 121, pp. 59-66.
[2] Yamaguchi, N., Tominaga, T., Hattori, S., and
Mitsuhashi, T., 1991, “Secondary-Loss
Reduction by Forward-Skewing of Axial
Compressor Rotor Blading”, Proc. Yokohama
International
Gas
Turbine
Congress,
Yokohama, Japan, pp. II.61 - II.68.
[3] Kuhn, K., 2000, “Experimentelle Untersuchung
einer Axialpumpe und Rohrturbine mit
gepfeilten Schaufeln”, Dissertation Technische
Universität Graz, Institut für Hydraulische
Strömungsmaschinen.
[4] Lakshminarayana, B., 1996, Fluid Dynamics
and Heat Transfer of Turbomachinery, John
Wiley & Sons, Inc.
[5] Spalart, P., and Allmaras, S., 1992, “A OneEquation Turbulence Model for Aerodynamic
Flows”, Technical Report AIAA-92-0439.
[6] Vad, J., and Bencze, F., 1998, “ThreeDimensional Flow in Axial Flow Fans of NonFree Vortex Design”, Int J Heat Fluid Flow,
Vol. 19, pp. 601-607.
REFERENCES
1 Wright, T., Simmons, W. E. Blade Sweep for
Low-Speed Axial Fans. J. of Turbomachinery,
1990, 112, 151-158.
2 Fukano, T., Takamatsu, Y. The effects of tip
clearance on the noise of low-pressure axial
and mixed flow fans. J. of Sound and
Vibration, 1986, 105, 291-308.
3 Furukawa, M, Inoue, M., Saiki, K.,
Yamada, K. The role of the tip leakage vortex
breakdown in compressor rotor aerodynamics.
J. of Turbomachinery, 1999, 121, 469-480.
4 Storer J.A., Cumpsty N.A. Tip leakage flow
in axial compressor. J. of Turbomachinery,
1991, 252-259.
5 Suder, K. L., and Celestina, M. L.
Experimental and computational investigation
of the tip clearance flow in a transonic axial
compressor rotor. J. of Turbomachinery, 1996,
118, 218-229.
6 Lakshminarayana, B., Zaccaria, M., and
Marathe, B. The structure of tip clearance
flow in axial flow compressors. J. of
Turbomachinery, 1995, 117, 336-347.
7 Inoue, M., Furukawa, M. Physics of tip
clearance flow in turbomachinery. ASME
paper FEDSM2002-31184, 2002.
8 Jang, C., Furukawa, M., Inoue, M. Analysis
of vortical flow field in a propeller fan by
LDV measurements and LES - Part I&Part II.
J. Fluids Eng., 2001, 123, 748-761.
9 Jang, C., Fukano, T.,Furukawa, M. Effects
of the tip clearance on vortical flow and its
relation to noise in an axial flow fan. JSME
Transaction Series B, 2003, 46, 356-365.
10 Brown N. A. The use of skewed blades for
ship propellers and truck fans. Noise and
Fluids Engineering, Atlanta, USA, 1977.
11 Longet, C., Battistoni, F. Design of low noise
fan. In Proc. 2nd International CETIAT and
CETIM Symposium on Fan Noise, Senlis,
France, 23-25th September, 2003.
12 Beiler, M.G., Carolus, T.H. Computation and
measurement of the flow in axial flow fans
with skewed blades. J. of Turbomachinery,
1999, 121, 59-66.
13 Borello, D., Corsini, A., Rispoli, F. A finite
element
overlapping
scheme
for
turbomachinery flows on parallel platforms.
Computers and Fluids, 2003, 32/7, 1017-1047.
14 Craft, T.J., Launder, B.E., Suga, K.
Development and application of a cubic eddyviscosity model of turbulence. Int. J. of Heat
and Fluid Flow, 1996, 17, 108-155.
15 Corsini A., Rispoli F. Flow analyses in a
high-pressure axial ventilation fan with a nonlinear eddy-viscosity closure. Int. J. of Heat
and Fluid Flow, 2005, 26-3, 349-361.
16 Corsini, A., Rispoli, F. Using sweep to extend
stall-free operational range in axial fan rotors.
J. of Power and Energy, 2004, 218, 129-139.
17 Corsini, A., Rispoli, F., Santoriello A. A
New Stabilized Finite Element Method for
Advection-Diffusion-Reaction
Equations
using Quadratic Elements. In: Modelling Fluid
Flow. The state of the art, Ed. by J. Vad, T.
Lajos and R. Schilling et al., Springer, 2004,
IX, 434 p.
18 Corsini A., Rispoli F. Numerical simulation
of three-dimensional viscous flow in an
isolated axial rotor. The Archive of
Mechanical Engineering (Archiwum budowy
maszyn), Polska Akademia Nauk, 1999,
XLVI-4, 369-392.
19 Mohammed, K. P., Prithvi Raj, D.
Investigations on axial flow fan impellers with
forward swept blades. J. of Fluids
Engineering, 1977, 543-547.
20 Kang S., Hirsch C. Numerical simulation of
three-dimensional viscous flow in a linear
compressor cascade with tip clearance. J. of
Turbomachinery, 1996, 118, 492-505.
REFERENCES
Bae, J.W., Breuer, K.S., Tan, C.S., (2005),
Active control of tip clearance flow in axial
compressors, J. Turbomachinery, 127, pp. 352-362.
Corsini, A., Rispoli, F., (2004), Using sweep to
extend stall-free operational range in sub-sonic
axial fan rotors, J. of Power and Energy, 218, pp.
129-139.
Corsini, A., Rispoli, F., (2005), Flow analyses in a
high-pressure axial ventilation fan with a nonlinear eddy-viscosity closure, Int. J. of Heat and
Fluid Flow, 26, pp. 349-361.
Corsini, A., Rispoli, F., Santoriello, A., (2003), A
new stabilized finite element method for advectiondiffusion-reaction equations using quadratic
elements, Modelling Fluid Flow, Ed. by T. Lajos et
al., Springer Verlag.
Corsini, A., Rispoli, F., Kinghorn I., Sheard G.,
(2004), The aerodynamic interaction of tip leakage
and mainstream flows in a fully-ducted axial fan,
ASME Paper GT2004 -53408.
Craft, T.J., Launder, B.E., Suga, K. (1996),
Development and application of a cubic eddyviscosity model of turbulence, Int. J. of Heat and
Fluid Flow, 17, pp. 108-155.
Fukano, T., Takamatsu, Y., (1986), The effects of
tip clearance on the noise of low-pressure axial and
mixed flow fans, J. of Sound and Vibration, 105, pp.
291-308.
Furukawa, M., Inoue, M., Kuroumaru, M., Saiki,
K., Yamada, K., (1999). The role of tip leakage
vortex
breakdown
in
compressor
rotor
aerodynamics, J. of Turbomachinery, 121, pp. 469480.
Ganz U.,W., Joppa P.,D., and Scharpf D.,F.,
(1998), Boeing 18-inch fan rig broadband noise
test, NASA CR-1998-208704.
Inoue, M., Furukawa, M., (2002), Physics of tip
clearance flow in turbomachinery. ASME paper
FEDSM2002-31184.
Inoue, M., Kuroumaru, M., Furukawa, M, (1986),
Behavior of tip leakage flow behind an axial
compressor rotor, J. of Gas Turbine and Power,
108, pp. 7-14.
Jang, C., Furukawa, M., Inoue, M., (2001). Analysis
of vortical flow field in a propeller fan by LDV
measurements and LES - Part I&Part II, J. Fluids
Eng., 123, pp. 748-761.
Jang, C., Fukano, T.,Furukawa, M., (2003), Effects
of the tip clearance on vortical flow and its relation
to noise in an axial flow fan, JSME Transaction
Series B, 46, pp. 356-365.
Jensen, Carl E., (1986), Axial-flow fan, US
Patent No. 4,630,993.
Kang, S., and Hirsch, C., (1993a), Experimental
study on three dimensional flow within a
compressor cascade with tip clearance: Part I:
velocity and pressure fields, J. of Turbomachinery,
115, pp. 435-443
Kang, S., and Hirsch, C., (1993b), Experimental
study on three dimensional flow within a
compressor cascade with tip clearance: Part II: the
tip leakage vortex, J. of Turbomachinery, 115, pp.
444-452
Kang S., Hirsch C., (1996), Numerical simulation of
three-dimensional viscous flow in a linear
compressor cascade with tip clearance, J. of
Turbomachinery, 118, pp. 492-505.
Khourrami, M., R., Choudari, M., (2001), A
novel approach for reducing rotor tip-clearance
induced noise in turbofan engines, AIAA paper
2001-2148.
Roy, B., Chouhan, M., Kaundinya, K.V.,
(2005), Experimental study of boundary layer
control through tip injection on straight and swept
compressor blades, ASME paper GT2005-68304.
Smith, G..D.J., Cumpsty N.A., (1984), Flow
phenomena in compressor casing treatment. J. Eng.
Gas Turbines Power, 106, pp. 532-541.
Storer, J.A., Cumpsty N.A., (1991), Tip leakage
flow in axial compressors. J. of Turbomachinery,
113, pp. 252-259.