A A me m er r ic i ca an n J Jo ou ur rn na al l o of f E En ng gi in ne ee e ri r in ng g R Re e se s ea ar rc c h h ( (A AJ JE ER R) ) e e- -I IS SS SN N: : 2 23 32 20 0- -0 08 84 47 7 p p- -I IS SS SN N : : 2 23 32 20 0- -0 09 93 36 6
V
Vo ol lu um me e- -5 5, , Is I ss su ue e- -1 10 0, , p pp p- -1 18 81 1- -1 18 86 6 ww w ww w. .a aj je er r. .o or rg g R Re es se e ar a rc ch h P Pa ap pe er r O Op pe en n A Ac c ce c es s s s
De D es si ig gn n o of f a a C Ce en nt tr ri if fu ug g al a l B Bl lo o w w er e r f fo or r a a 4 40 00 0k kg g R Ro ot ta ar ry y F F ur u rn n ac a ce e. . Sa S an ni i M Ma al la am mi i S Su ul le ei im ma an n, , K Ka an nt ti io ok k O Ob ba ad di ia ah h, , a an nd d L La a wa w al l I Ib br ra ah hi im m A At ti ik ku u
D
De ep pa ar rt tm me en nt t o of f M Me ec ch ha an n ic i ca al l E En ng gi in n ee e er ri in ng g, , C Co ol ll le eg ge e o of f E En ng gi in ne ee er ri in ng g, , K Ka ad du un na a p po ol ly yt te ec ch hn n ic i c, , K Ka ad du un na a. .
AB A BS ST TR RA AC CT T: : Po P oo or r pe p er rf fo or rm ma an nc ce e of o f a a ro r ot ta ar ry y f fu ur rn na ac ce e ca c an nn no ot t be b e u un nc co on nn ne ec ct te ed d to t o fa f ai il lu ur re e in i n t th he e d de es si ig gn n of o f t th he e bl b lo ow we er r a am mo on ng g o ot th h er e rs s, , T Th h is i s p pa ap pe er r d di is sc cu us ss s t th he e d de es si ig gn n o of f a a c ce en nt tr ri if fu ug ga al l b bl lo ow we er r f fo o r r a a r ro ot ta ar ry y f fu ur rn n ac a ce e w wh hi ic ch h w wi il ll l g gi iv ve e t
th he e r re eq qu ui ir re ed d m ma a no n om me et tr ri ic c e ef ff fi ic ci ie en nc cy y t th h at a t w wi il ll l a ai id d a ad de eq qu ua at te e c co om mb bu us st ti io on n a as s r re eq qu ui ir re ed d. . T Th he e b bl lo ow we er r w wa as s d de es si ig g ne n ed d t to o c
co on nv ve er rt t ‘ ‘d dr ri iv ve er r’ ’ en e ne er rg gy y t to o ki k in ne et ti ic c e en n er e rg g y y i in n t th he e f fl lu ui id d by b y a ac cc ce el le er ra at ti in ng g i it t t to o th t he e o ou ut te er r r ri im m of o f t th he e r re ev vo ol lv vi in ng g de d ev vi ic ce e kn k no ow wn n as a s th t he e im i mp pe el ll le er r. . T Th he e i im mp pe el ll le er r, , d dr ri iv ve en n b by y t th he e b bl lo o we w er r sh s ha a ft f t ad a dd ds s th t he e ve v el lo oc ci it ty y c co o mp m po on ne en nt t t to o th t he e fl f lu u id i d by b y ce c en nt tr ri if fu ug ga al ll ly y c ca as st ti in ng g th t he e f fl lu ui id d aw a wa ay y f fr ro om m th t he e im i mp p el e ll le er r va v an ne e ti t ip ps s. . Th T he e a am mo ou un nt t of o f e en ne er rg gy y g g iv i ve en n to t o t th he e fl f lu u id i d c
co or rr re es sp po on nd ds s t to o t th he e v ve el lo oc ci it ty y a at t t th he e e ed dg g e e o or r v va an ne e t ti ip p o of f t th he e i im mp p el e ll le er r. .
Significance: Centrifugal blowers are applicable in furnaces such as Rotary and cupola furnace, the efficiency of these furnaces depend on the blast rate and air delivery from a well design blower. This paper will guide to achieve this aims.
Keywords: Impeller, Blower, Manometric efficiency, Rotary furnace
I. INTRODUCTION
Blowers is a contrivance which provides energy to the air, system, to assists to increase the pressure flow takes place from the low pressure side to high pressure side.
The blowers can either be classified as a rotor dynamics machines or under displacement machines [
[A Al la an n, , M M. .( ( 1 19 97 79 9) )] ]. .. In this design a rotor dynamic (BLOWER) is taken because of its higher efficiency and less cost.
On the basis of transfer of mechanical energy, the blowers can be broadly classified as follows:
1.1 Rotor Dynamic Blowers
In rotor dynamic blowers, increase in energy level is due to a combination of centrifugal energy pressure energy and kinetic energy.
1. The energy transfer, in radial flow blowers, occurs mainly when the flow is in its radial path.
2. In axial flow blowers, the energy transfer occurs when the flow is in its axial direction.
3. The every transfer in a mixed flow blowers takes place when the flow comprises of radial as well as a axial components.
1.2 Positive Displacement Blowers
This type of blowers uses the principle of piston displacement in a cylinder, which controls the volume and pressure rise and drop of the incoming air. It works efficiently with higher pressure drops and less flow rate.
1.3 Classification Of Centrifugal Blowers
On the basis of characteristic features, the centrifugal blowers are classified as:
1. Type of casing 2. working heads 3. liquid handled
4. Number of impellers per shaft 5. Number of entrance to the impeller
6. Relative direction of flow through impeller 1.4 Components Of The Centrifugal Blower
1. Impeller: an impeller is a wheel (or rotor) with a series of backward curved varies or blades. It is mounted
on a shaft which is usually coupled to an electric motor. And there are three types of impellers.
a. Closed Impellers: In this type of impeller, vanes are provided with metal cover plates en shrouds on both the sides. It provides better guidance for the fluid. This type of impellers is chosen in this design.
b. Semi-open impellers: in this type, the vanes have only the base plate and no crown plate. It can be used with fluids that contain debris.
c. Open-impeller: this type of impellers has neither the crown plate nor the bottom, plate. They are employed to blow the air that contains suspended solids.
2. Casing:
The casing is an air tight-chamber surrounding the blower impeller. It contains suction and discharge arrangements, supporting bearings and facilitates to house the rotor assembly also protects leakages. There are also three types of casing.
a. Volute Casing: In this casing type, the area of flow gradually increases from impeller outlet to the delivery pipe so as to reduce the velocity of flow. Thus the increase in pressure occurs in volute casing.
b. Vortex Casing: If a circular chamber is provided between the impeller and the volute chamber, the casing is known as vortex casing. The circular chamber is known as vortex or whirl pool chamber. The vortex chamber converts some of the kinetic energy to pressure energy. So it has more efficiency than simple involutes casing.
3. Suction Pipe:
This is the pipe or opening that connects the centre of the impeller to sump from which fluid is to be lifted.
4. Delivery Pipe (Nozzle)
This is the outlet of the blower; its main function is to help in giving higher velocity to the air at the expense of pressure drop in it.
II. METHODODLOGY Design Analysis
This design is made based on the following assumptions for maximum efficiency
i. Air enters the impeller eye in radial direction which makes the whirls component at inlet zero.
ii. No loss due to shock at entry base on the above mentioned assumptions the design parameters are fairly estimated, these are:
Blade inlet and outlet diameter
Blade width
Number of blades
Number of blade revolutions per minute
Manometric head
Analysis of the various velocities during he blades operation
The Motor horse power required
The pressure rise across the impeller
The overall efficiency and power developed by the blower.
2.1 Design Specification
This blower is expected to have the following ratings:
Q = 6.77m 3 /min P = 2 – 10Kpa
Where Q= volumetric flow rate P= pressure developed a) 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 0 . 7
2
1
D
D , for this design
The ratio
2 1
D
D = 0.65 is taken;
If D 1 = 182mm
D mm
D 280
65 . 0
182 65
. 0
1
2
Therefore, D 1 = 182mm, D 2 = 280mm b) Number of Blades
From ASME code, for optimum performance the number of blades is given by
2 1
2
1 5 . 8
D D Sin C
Where β 2 is the outlet vane angle which has a range of 20 0 <β 2 <90 0 For this design β 2 = 81 0 and
2 1
D
D = 0.65
Blades 24
65 . 0 1
81 5
. 8
1 5 . 8
0 2 1
2
Sin D D
Sin
C
c) Blade Width
It is given from ASME code specification that, the blade width is given by the formula. [A Ad de ej ju uy yi ig gb be e, , S. S .B B. . (
(2 20 00 06 6) ). .] ]
1 ) 2 (
6 1
C
D W
Where C is the number of blades
mm
W 22
1 24
2 182 . 0 6
d) Number of revolution per minute
For a centrifugal blower to deliver an air, the centrifugal head must be equal to the total head [ [E Ed dw wa ar rd d, , H H. .S S. . (1 ( 19 99 95 5) )] ].
Thus, H
mang U
U
2
2 1 2 2
Where U 1 and U 2 are he respective impeller velocities at inlet and outlet.
60 U
and
60
2 2
1 1
N D N
U D
So,
gH man
U
U 2 2 1 2 2
Where, H man is the manometric head
min / 1247
196 10
0 . 9 10
1 . 2
196 60
182 . 0 60
280 . 0
10 81 . 9 2 60
60
2 5 2
4
2 2
2 1 2
2
rev N
N N
N N
N D N
D
e) The Manometric Head
This is head which the blower needs to overcome before it delivers and it is given as
m H
Theref ore
mls N
D U
N mls U D
g U H U
man man
10 8
. 9 2
12 18
,
18 60
1247 280
. 0 60
12 60
1247 182
. 0 60
2
2 2 2 2
1 1
2 1 2 2
Analysis of the various velocities of the blades From the velocity diagram
V 2 = absolute velocity of the fluid at outlet V r2 = relative velocity of the fluid at outlet Vf 2 = velocity of flow at outlet
Vw 2 = whirl velocity at outlet U 2 = Velocity of the blades at outlet β 2 = Outlet Vane angle
The corresponding inlet parameters are:
V 1 , V r , Vf 1 , V w1 , U 1 and β 1
From the continuity equation
s m D
Q Vf
s m
D Q Vf
s m Vf
D Vf
D Q
/ 9 022 . 0 182 . 0
1128 . 0 /
8 . 5
022 . 0 280 . 0
1128 . 0
/ 1128 . 0
1 1 1
2 2 2
3 1
1 1 1 2 2
These are the velocities of flow at outlet and inlet.
For the absolute velocities of the flow V1 and V2 from the velocity diagram.
) assumption initial
(from V
and
1 1
2
2 Vf
Sin Vf
V
Also in this design =30 0 , β 1 = 10 0 and β 2 = 81 0 .
These are taken from the range of optimum performance from ASME code.
s m Sin
Sin
V Vf 11 . 6 /
30 8 . 5
30 0 0
2
2
V 1 = Vf 1 by assuming radial flow at inlet.
The whirl velocities at inlet and outlet are estimated from 0
1 w
V From initial assumption s m V w 11 . 6 2 9 2 7 , 3 /
2
The relative velocities Vr 1 and Vr 2 at inlet and outlet are given from velocity triangle.
s m Sin
Sin Vr V
s m Sin
Sin Vr Vf
/ 52 10
9
/ 9 . 5 81
8 . 5
0 1
1 1
0 2
2 2
f) Horse power required by the motor This is given by the formula
550 H man
Q
Where, Q = volumetric flow rate m 3 /s
= ρg
ρ= density of air Kg/m 3
hp P
P
2 . 1
550
10 8 . 9 002 . 1 77 . 6
g) The pressure through the impeller
By applying the energy, equation from the entrance to exit of the impeller including the energy head.
8 . 9 2
9 6 . 10 11 002 . 1 8 . 9
2 2
2 2
1 2
2 2
1 2 2 1
2
2 1 2 2 1
2
P P
g V V H r P P
g V H V
r P P
man man
P 2 – P 2 = 71Pa
(h) Efficiency of the blower
The efficiency of the blower is given by
% 6 . 74 4 . 13
10
4 . 13 8 . 9
18 3 . V 7
impeller by imparted Head
10
liquid o imepller t by imparted Head
head manometric
2 w2
m man m
g U
m H
This is the manometric efficiency developed by impeller
III. DICUSSIONS AND CONCLUSION
For optimum performance the ratio of internal diameter to external diameter falls between 0.4 to 0.7(ASME).The diameter of the blade is a design parameter which others depend opon. I If f t th he e s sp pe ee ed d ( (r rp pm m) ) o of f t th he e im i mp pe el ll le er r r re em ma ai in ns s t th he e s sa am me e t th he en n t th he e l la ar rg ge er r t th he e i im mp pe el ll le er r d di ia am me et te er r t th he e h hi ig gh he er r t th he e ge g en ne er ra at te ed d he h ea ad d. . A As s t th he e d di ia am me et te er r of o f t th he e i im mp pe el ll le er r i is s i in nc cr re ea as se ed d, , t th he e t ti ip p s sp pe ee ed d a at t t th he e o ou ut te er r e ed dg ge e o of f t th he e i im mp pe el ll le er r i in nc cr re ea as se es s c co om mm me en ns su ur ra at te el ly y. . H Ho o we w ev ve er r, , t
th he e t to ot ta al l e en ne er rg gy y i im mp pa ar rt te ed d to t o t th he e f fl lu ui id d a as s t th he e di d ia am me et te er r i in nc cr re ea as se es s go g oe es s up u p b by y t th he e s sq qu ua ar re e o of f th t he e di d ia am me et te er r i in nc cr re ea as se e. . Th T hi is s c ca an n b be e u un nd de er rs st to oo od d b by y t th he e f fa ac ct t t th ha at t t th he e f fl lu ui id d’ ’s s e en ne er rg gy y i is s a a f fu un nc ct ti io on n o of f i it ts s v ve el lo oc ci it ty y a an nd d t th he e v ve el lo o ci c it ty y a ac cc ce el le er ra at te es s as a s th t he e f fl lu ui id d p pa as ss se es s th t hr ro ou ug gh h t th he e im i mp pe el ll le er r . . T Th he e bl b lo ow we er r w wa as s sp s pe ec ci if fi ic ca al ll ly y de d es si ig gn ne ed d f fo or r r ro ot ta ar ry y f fu ur rn na ac ce e o op pe er ra at ti io o n n (5 ( 50 00 0k kg g c ca ap pa ac ci it ty y) ) b b ut u t i it t c ca an n e eq qu ua al ll ly y b be e a ad da ap pt te ed d f fo or r u us se e i in n o op pe er ra at ti io on ns s t th ha at t n ne ee ed de ed d a ai ir r s su up pp pl ly y s sy ys st te em m f fo or r i it ts s s sm mo oo ot th h r
ru un n ni n in ng g, , m mo os st t e es sp pe ec ci ia al ll ly y i in n c co om mb bu us st ti io on n- -r re el la at te ed d o op pe er ra at ti io on ns s. . RE R EF FE ER RE EN NC CE ES S
[1 [ 1] ]. . Al A la an n, , M M. .( ( 1 19 97 79 9) ). . E En ng gi in ne ee er ri in ng g F Fl lu ui id d M Me ec ch ha an ni ic cs s M Mc cG Gr ra aw w- -H Hi il ll l I In nt t. . B Bo oo ok k C Co o. ., , A Au uc ck kl la an nd d, , N Ne ew w Z Ze ea al la an nd d. .
[2 [ 2] ]. . Dr D r C. C .O O. .N Nw wa aj ja ag gu u( ( 19 1 99 94 4) ) , , F Fo ou un nd dr ry y Th T he eo or ry y an a nd d P Pr ra ac ct ti ic ce e P Pu ub bl li is sh he ed d by b y B B. . C. C . Pu P ub bl li is sh he er r Lt L td d N Ni ig ge er ri ia a Me M et ta al ll lu ur rg gi ic ca al l E En ng gi in ne ee er ri in ng g De D ep pa ar rt tm me en nt t E En nu ug gu u s st ta at te e U Un ni iv ve er rs si it ty y. .
[
[3 3] ]. . D. D .T Ta ay yl lo or r L Ly ym ma an n, ,( (1 19 99 96 6) ), , M Me et ta al l h ha an nd d b bo oo ok k 8 8
tthhe ed di it ti io on n v vo ol l. .1 15 5 p pu ub bl li is sh he ed d b by y A Am me er ri ic ca an n S So oc ci ie et ty y o of f m me et ta al l O Oh hi io o. . [4]. Edward, H.S. (1995). Mechanical Engineers Reference Book, 12
th