DDeessiiggnn ooff aa CCeennttrriiffuuggaall BBlloowweerr ffoorr aa 440000kkgg RRoottaarryy FFuurrnnaaccee..

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

_man

g 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

^tthh

e 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

ed. The Bath Press, Bath, UK.

[5]. Oyelami, A.T.; and Adejuyigbe, S.B. (2006). The design of a radiation-recuperative heat exchanger for a 200kg capacity rotary furnace. AU J.T. 10(2): 101-8.

[6 [ 6] ]. . Tu T ut to on n, , R R. .K K. . ( (1 19 98 84 4) ). . P Pr ri in nc ci ip pl le es s o of f T Tu ur rb bo o- -m ma ac ch hi in ne er ry y. . S S & & F FN N S Sp po on n, , L Lo on nd do on n, , E En ng gl la an nd d