DESIGN AND FABRICATION OF CENTRIFUGAL AIR BLOWER TEST RIG

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International Journal of Thermal Engineering (IJTE)
Volume 10, Issue 1, January – December 2022, pp. 11–18, Article ID: IJTE_10_01_002
Available online at https://iaeme.com/Home/issue/IJTE?Volume=10&Issue=1
Journal ID: 2121-0305
© IAEME Publication
DESIGN AND FABRICATION OF
CENTRIFUGAL AIR BLOWER TEST RIG
Mohammed Asif Kattimani1, Md Nabeel Ahmed2, Adnan Akram3
1
Assistant Professors, Department of Mechanical Engineering,
Lords Institute of Engineering and Technology, Hyderabad, India
2,3
Research Scholar, Department of Mechanical Engineering,
Lords Institute of Engineering and Technology, Hyderabad, India
ABSTRACT
A centrifugal blower is an air moving device that uses an impeller to pull air into a
tube-like structure and release it at a 90o
angle. The impeller is a set of blades inside
the blower that rotates at a high rate to pressurize and move the air. The Project aims
to describe the basic design principles of Centrifugal Air Blower including the
fabrication method of an experimental set up. The Objective of this project is to conduct
a performance test on an Air Blower & to determine the efficiency of the blower and to
check the behavior of the Performance characteristics curve.The construction of Air
Blower involves different specific issues that have to be taken into consideration when
developing in detailed design. Various technical details and differences in the design
and equipment used for Air Blower have been well presented and discussed.
Key words: Forward Type Centrifugal Blower, Delivery Flow, Discharge, Speed,
Impeller, Volute Casing, and Temperature
Cite this Article: Mohammed Asif Kattimani, Md Nabeel Ahmed, Adnan Akram,
Design and Fabrication of Centrifugal Air Blower Test RIG, International Journal of
Thermal Engineering (IJTE),10(1), 2022, pp. 11–18.
https://iaeme.com/Home/issue/IJTE?Volume=10&Issue=1
1. INTRODUCTION
The Blower is a single stage centrifugal type. The air is sucked from atmosphere from suction
side. The slightly compressed air passes through the spiral case, before it comes out through the
outlet. Blowers are used to discharge higher volumes of air at low pressures. These are used in
blast furnaces, cupolas, mines, air conditioning plants, etc. The three types of impellers namely:
a) Backward curved, b) Radial c) Forward curved [1].
Centrifugal blowers have been researched, analyzed and evaluated by different angles by
various researchers, recommendation bodies, and projects using finite element analysis. A
thorough study has been done on initial level to analyze and evaluate the centrifugal blowers.
Lin C. C. et al. [2] here, authors carried out a stress calculation for a fiber reinforced composite
thruster blade. The composite blade is constructed using multiple layers of braided fiber in a
thick shell skin layer. The core is filled with foam type material and uses shear webs for internal

Design and Fabrication of Centrifugal Air Blower Test RIG
supports. The objective of this work is to explore the rotating blade hydrodynamic design
constraints of a typical composite blade by performing a 3-D element- stress analysis. Two
salient features are exhibited in the numerical result for composite blade stress calculations.
First deflection at the tip of a composite blade can be quite large compared to that of an isotropic
metal blade using the same blade form. Second maximum through the thickness tensile stress
in the skin layer thickness direction could become critical for higher loadings. Composite blade
can provide not only a means of weight savings but is also can have excellent structural stiffness
and strength properties through proper geometric and material design. Wan-Ho J. et al. [3] in
this paper, authors described Discrete-frequency axial-flow fan noise reduction using active
noise control. The unique aspect of this research is the use of the fan itself as the anti-noise
source in the active noise control scheme. This is achieved by driving the entire fan unit axially
with an electrodynamics shaker which mechanically couples the solid surfaces of the fan to the
acoustic medium. Banks C. L., et.al [4] Authors in this article present the results of an
investigation of centrifugal blower noises. Experiments on three different types of blowers were
conducted to determine the major noise generation mechanisms. The information thus gained
has led to an innovative noise reduction method utilizing a stationary, non-contacting transition
mesh. In this Experiment an overall noise reduction of 3 to 5 dB was achieved for all the blowers
running at impeller speeds in the range of 10 to 30 m/s. In addition, a semi analytical model
was developed to predict noise spectra from dimensionally similar centrifugal blowers. Brian
Cao R. et al. [5] the objective of his paper is to establish a sound technical basis for the large-
scale use of fiber composites in naval vessels. It includes in-depth studies of material
performance and characterization, structural performance under both static and extreme
dynamic loads, non-destructive inspection and evaluation, damage repair, fire performance, and
effectiveness of various electro-magnetic shielding methods. Chen-Kang H. et al. [6] A
backpack blower powered by a small utility engine requires high operating performance, while
at the same time, the demand by society for cleaner exhaust gas and lower noise is ever more
intensifying. Buhei Kobayashi et.al have successfully solved this problem by developing a new
blower which satisfies the requirements like higher operating performance with low noise.
Srinath Y. et al [7] in this paper the tonal noise radiated by a subsonic blower fan of an HVAC
system was studied. Numerical simulations have been performed and compared to
measurements. The numerical simulation is based on the aero-acoustic analogy where the
unsteady flow is first computed using STAR-CD and then passed to LMS SYSNOISE to
compute the acoustic radiation. The measurements have been performed in the semi-anechoic
room of Denso Thermal System Italia. Good correlation has been found between the numerical
simulation both in terms of level and spatial distribution.
2. CENTRIFUGAL BLOWER
Centrifugal Blowers are also known as Centrifugal Fans. The kinetic energy produced by the
impellers of the Centrifugal Blower Fan on rotation is used to increase the pressure of the air
stream, which in turn moves them against the resistance caused, by ducts, dampers and other
components.

Mohammed Asif Kattimani, Md Nabeel Ahmed, Adnan Akram
Figure 1 Centrifugal Air Blower
3. DESIGN SPECIFICATION
This blower is expected to have the following ratings:
Q = 5.84m3 /min
Where Q= volumetric flow rate
P= pressure developed
i. Blades Diameters
From the optimum performance specification, it is stated that the ratio of the internal diameter
to the external diameter is to fall between 0.4 to 0.7 as stated in the ASME code.
That is 0 .4 < 𝐷1 / D2 < 0.7, for this design
The ratio D1 / D2 = 0.65 is taken;
If D1 = 300mm
D2 =
𝐷1
0.65
=
300
0.65
= 500mm (i)
Therefore, D1 = 300mm and D2 = 500mm
ii. Number of Blades
From ASME code, for optimum performance the number of blades is given by
C =
8.5 𝑆𝑖𝑛 β2
1−𝐷1/𝐷2
(ii)
Where β2 is the outlet vane angle which has a range of 200
<β2 <900
For this design β2 = 810
and D1 / D2 = 0.65
C =
8.5 𝑆𝑖𝑛 β2
1−𝐷1/𝐷2
C =
8.5 𝑆𝑖𝑛 81
1−0.65
C = 24 Blades
iii. Blade Width
It is given from ASME code specification that, the blade width is given by the formula.
[Adejuyigbe, S.B. (2006).]
W =
6(
D1
2
)
C+1
(iii)

Where C is the number of blades
W =
6(
300
2
)
24+1
= 36mm
iv. Number of revolutions per minute
For a centrifugal blower to deliver an air, the centrifugal head must be equal to the total head
[10].
Thus,
U22− U12
2g
= Hman (iv)
Where U1 and U2 are he respective impeller velocities at inlet and outlet.
U1 =
 D1 N
60
and U2 =
 D2 N
60
So,
U22
− U12
= 2gHman
Where, Hman is the manometric head
[
 D1 N
60
]
2
- [
 D2 N
60
]
2
= 2 x 9.81 x 5
[
 x 500 x N
60
]
2
- [
 x 300 x N
60
]
2
= 2 x 9.81 x 5
N = 1500 r.p.m
v. Analysis of the various velocities of the blades
From the velocity diagram
From the continuity equation
Q = D2β2 Vf1 = 5.84 m3 / s (v)
Vf2 =
𝑄
D2 β2
=
0.0973
 x 0.5 x 0.022
Vf2 = 2.8 m / s
Vf1 =
𝑄
D1 β2
=
0.0973
 x 0.3 x 0.022
Vf1 = 4.69 m / s
These are the velocities of flow at outlet and inlet.
For the absolute velocities of the flow V1 and V2 from the velocity diagram.
V2 =
𝑉𝑓2
𝑆𝑖𝑛 
and V1 = Vf1 (from initial assumption)
The whirl velocities at inlet and outlet are estimated from
𝑉𝑊1 = w V1 From initial assumption
𝑉𝑊2 = √5.62 − 4.692
𝑽𝑾𝟐 = 3.1 m/s
Also in this design  =300
, β1 = 100
and β2 = 810
.
These are taken from the range of optimum performance from ASME code.
V2 =
𝑉𝑓2
𝑆𝑖𝑛 30
=
2.8
𝑆𝑖𝑛 30
= 5.6 m/s
The relative velocities Vr1 and Vr2 at inlet and outlet are given from velocity triangle.
Vr2 =
𝑉𝑓2
𝑆𝑖𝑛 β2
=
2.8
𝑆𝑖𝑛 80
= 2.84 m/s

Vr1 =
𝑉1
𝑆𝑖𝑛 β1
=
4.69
𝑆𝑖𝑛 10
= 27 m/s
vi. The pressure through the impeller
By applying the energy, equation from the entrance to exit of the impeller including the energy
head.
P2−P1
r
= Hman -
V22− V12
2g
(vi)
P2 - P1 = r[Hman −
V22− V12
2g
]
P2 - P1 = 9.81 x 1.29 [5 −
5.62− 4.692
2 x 9.81
]
P2 – P1 = 626 Pa
vii. Efficiency of the blower
The efficiency of the blower is given by
m =
𝑚𝑎𝑛𝑜𝑚𝑒𝑡𝑟𝑖𝑐 ℎ𝑒𝑎𝑑
𝐻𝑒𝑎𝑑 𝑖𝑚𝑝𝑎𝑟𝑡𝑒𝑑 𝑏𝑦 𝑖𝑚𝑝𝑒𝑙𝑙𝑒𝑟 𝑡𝑜 𝑙𝑖𝑞𝑢𝑖𝑑
(vii)
Hman = 50 m
Head imparted by impeller =
VW2 x U2
g
=
3.1 x 39.2
9.81
= 12.3m
ŋm =
5
12.3
= 40.6%
4. CAD MODELING OF CENTRIFUGAL BLOWER
Figure 2 Impeller 3d
design
Figure 3 Impeller Drafting Figure 4 Impeller Drafting

Figure 5 Casing Drafting
5. RESULTS AND DISCUSSIONS
Table 1 Observation
5.1. Calculation
5.1.1. ¼ opening
i. Input to blower:
IP =
𝑁×1000×3600
𝑡×𝐸𝑀𝐶×736
×0.8 (viii)
Where, N = no. of Blinks of Energy meter.
t= time taken in seconds, for n no. of blinks of the Energy meter
EMC = Energy meter constant 1600 IMP/kW hr
IP =
20×1000×3600
15.01×1600×736
×0.8
IP = 3.25 hp (ix)
ii. Flow across Pitot tube:
Ha =
ℎ1
100
(
𝛿𝑤
𝛿𝑎
− 1)
Ha =
6.7
100
(
1000
1.293
− 1) = 51.75 m (x)
Sl.
No.
Position of valve Velocity head
(mm)
Static Head
(mm)
Time Taken for
n=20 billings ( t )
1 1/4open 6.7 7 15.01
2 1/2open 4.6 4.7 13.59
3 3/4open 1.2 1.8 13.1
4 full open 0.5 0.7 12.5

iii. Static Head:
Hstat =
ℎ2
100
(
𝛿𝑤
𝛿𝑎
− 1)
Hstat =
7
100
(
1000
1.293
− 1)
Hstat = 54.06 m (xi)
iv. Velocity of air:
V = √2𝑔ℎ𝑎
V = √2 × 9.81 × 51.75
V = 31.86 m/s (xii)
v. Actual Volume of Discharge:
Q = AV
Q = 0.2×0.35×31.86
Q = 2.23 m3/s (xiii)
vi. Output Power (OP):
Output of blower =
𝛿𝑎×Q×ℎ𝑠𝑡𝑎𝑡
75
OP =
1.293×2.23×54.06
75
OP = 2.078 hp (xiv)
vii. Overall Efficiency:
Overall =
output of the blower
Input to blower
× 100
Overall =
2.078
3.25
× 100
Overall = 64% (xv)
Table 2 Result
Sl.
No.
Position of
valve
Input Power
(hp)
Output Power
(hp)
Discharge
M3
/s
Efficiency
(%)
1 1/4open 3.25 2.075 2.23 64
2 1/2open 3.59 1.155 1.847 32
3 3/4open 3.73 0.2262 0.944 6
4 full open 3.91 0.0179 0.1926 0.45

6. CONCLUSION
The performance of centrifugal blower mainly depends upon the design parameters of the
impeller blades. Air blower has been done according to the design criteria or depending upon
the actual discharge of air flow through the blower. The parameters used for the fabrication of
Air the Blower with final dimensions are inlet & outlet diameter of the impeller (300mm &
500mm), no of blades (24), blade width (36mm), max. Speed of the impeller (1800r.p.m)
respectively. The Design of all parts of the Air Blower is done by using SOLID WORK
software and the Fabrication of Centrifugal. After completion of the Fabrication part of the Test
Rig. , testing has been done on the Air Blower. By taking all the parameter’s reading calculation
has been done and the performance curve has been drawn. The efficiency of the blower is 45%.
The blower performance has been checked through all readings from the Test Rig and is
perfectly correct.
REFERENCES
[1] Electrical Energy Equipment: Fans and Blowers. UNEP. 2006. P. 21
[2] Lin C. C. and Lee Y. 1991. Study on the Performance of a Sirocco Fan (Optimum Design of
Blade Shape). International Journal of Rotating Machinery.7(6):405-414
[3] Wan-Ho J. and Duck-Joo L 1997. Centrifugal Pumps and Blowers, John Wiley & Sons, UK.
[4] Banks C. L. and Wu S. F 1998. Pesticide application equipment and techniques. FAO, Argil v.
Service Bull. No. 38 FAO Pub., Rome, Italy.
[5] Cao R. and HU J 2001.Fans, Pergomon Press, USA.
[6] Chen-Kang H. and Mu-En H. 2002.Design and Performance evaluation of Centrifugal blower
for mistblower. Unpublished M.Tech Thesis, IIT, Khargpur.
[7] Srinath Y. and Reddy K. M2003. Unified design and comparative performance evaluation of
forward and backward curved radial tipped Centrifugal Fan.Proc. of the Int.Con.on Mechanical
Eng. (ICME03-FL-11) 26-28 Dec.2001.
0
0.5
1
1.5
2
2.5
0 10 20 30 40 50 60
Discharge
(m3/s)
Velocity Head (m)
Figure 6 Discharge vs Velocity Head
0
0.5
1
1.5
2
2.5
0 20 40 60 80
Discharge
(m
3
/s)
Efficiency (%)
Figure 6 Discharge vs Efficiency

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