JOHNSON

Centrifugal Fans

and Rotary Blowers

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Mechanical Engineering

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Centrifugal Fans and Rotary Blowers

... BY ...

CHARLES SUNDERLAND JOHNSON

THESIS

FOR THE DEGREE OF BACHELOR OF SCIENCE

IX MECHANICAL ENGINEERING

IX THE

COLLEGE OF ENGINEERING

OF THE

UNIVERSITY OF ILLINOIS

PRESENTED JUNE, 1 <)()()

UNIVERSITY OF ILLINOIS

May 31, 1000.

THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BT

Charles Sunder! and Johnson

entitled Centrifugal Fans and Rotary Blowers

IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE DEGREE

of Bachelor., of Science in... Mechanical Engineer in^ ,

head of department of Mechanical Engineering.

Digitized by the Internet Archive

in 2013

http://archive.org/details/centrifugalfansrOOjohn

2

CENTRIFUGAL FANS & ROTARY BLOWERS.

For the movement of large volumes of air there are five gen-

eral types of machines. These are the disk or propeller fan, the

centrifugal fan, the rotary blower, the piston blower and the

steam jet blower.

Each of these machines seems to have its own field of adapt-

ability to which it is best suited and in which it should always

be used if efficient service is desired. The disk or propeller

fan is best suited for moving almost any volume of air when prac-

tically no resistance is offered to its flow. When a resistance

corresponding to from three fourths of an ounce to sixteen ounces

per square inch is found then the centrifugal fan is used. The

rotary blower is probably best adapted for handling air at from

one to five pounds per square inch. If the pressure is higher

than this then the piston blower comes into use. The steam- jet

finds a field of its own not on account of any mechanical effi-

ciency but because of its simplicity und great adaptability in

producing the draft in locomotives and other boilers. In its use

the moisture which comes from the steam plays an important part

in bpeaking up the clinkers that are formed on the grates. This

makes the steam-jet very useful when hard coal is used.

The above machines may be classified according to their form

and construction or according to their use.

46838

3

A classification as to construction:

(risk Fan.)

Pans . (

)

(Centrifugal Fan.

(Piston Blower.)

Positive Blowers. (

)

(Rotary Blower.

Steam- jet

.

A classification as to use)

(Disk Fan.)i

Exhausters. (Centrifugal Fan.

)

( $team- j e t

.

(Piston Blowers.)

Blowers. (Rotary Blowers.)

(Centrifugal Fan or Blower.

These classifications serve to show the relation between the

centrifugal fan, rotary blower and other air propelling machines.

Constructive features of rotary blowers.

There are a number of makes of rotary blowers on the market

and it is interesting to study the different mechanisms that have

been devised to accomplish the sane results. Each of these has

its own features. They all depend, however, upon the one working

principle that tha air is confined between two surfaces, station-

ary or movable, compressed by a reduction of volume and then alio

allowed to escape at the pressure thus obtained. It is from this

principle that the name "positive blower" is probably derived.

4

Tliis prieiple is apparently perfect and would undoubtedly

yield good results if friction and leakage could be eliminated.

But these difficulties are so marked that they greatly reduce the

mechanical efficiency. Another objection found is the frequent

necessity for a renewal of working parts.

The Baker Rotary Blower.

The external case of this blower is made of boiler iron,

turned up truly and inserted into the heads of the machine. The

heads are made of cast iron and are securely bolted to the bed

plate. These heads are bolted together longitudinally by iron

rods on the outside of the case. The drum concentric with the

case as well as trie two lower drums are solid castings and are

turned as true as possible. The lower drums act as abutments for

the blades. The motion of the air is as indicated on the drawings.

Gearing on the exterior of the case serves to turn the drums and

keep them in their proper relative positions. The lower drums

are revolved in opposite direction from the upper drum. A wire

guard or screen is placed over the inlet to prevent anything from

entering that might injure the working of the blower. The driv-

ing pulley is keyed to the s af t of the upper drum.

This blower offers considerable chance for slip or leakage

back into the inlet chamber. Besides the air which can get by the

drums and blades the space between the two lower drums is filled

every revolution with air from the discharge side and this is

then allowed to escape into the inlet chamber.

Baker B/ower.

6

The Mackenzie Blower.

The casing of this blower is also made of boiler iron. The

blades are pivoted to a shaft concentric wit?i the casing and are

revolved by means of the drum. This drum has a diameter of about

two thirds that of the casing and is placed tangent to the casing

between the inlet and outlet openings. The driving pulley is

keyed to the shaft of the drum.

The Reichhelm Pressure Blower.

The casing of this blower is made of cast iron. A shaft

which carries the driving pulley extends through the casing some-

what below the center. On this shaft a cast iron drum is fastened.

This drum has four recesses into which the blades or vanes fit.

A guide ring is turned into each head of the blower and into these

rings are four blocks, whici* are pivoted to the four blades. The

blades are revolved by means of the drum and are forced in and out

by the guide rings and blocks. An air chamber is placed over the

discharge pipe with the intention of decreasing the pulsations of

the blast.

This blower is advertised in four sizes capable of discharg-

ing from sixty-five to five hundred and eighty-five feet of air

at a pressure of from one pound to four pounds per square inch.

The Disstons Pressure Blower.

Within the casing of this machine are two revolving bodies

working together as indicated and geared by a pair of equal gears

on the outside of the casing. One of these bodies is a drum turned

7

Plate H.

Mackenzie's Blower

3

Plate IK.

Reich helm Blower.

9

Plate IE

10

to fit the casing snugly and having two cavities for the piston to

work in. The piston is also made of cast iron. This piston does

nearly all of the work of the blower, only a small portion of the

air that enters the cavities of the drum being forced into the

discharge opening.

The Roots Blower.

This blower is made on entirely different plans from those

before described. Nearly the entire machine is made of cast iron,

the only other metal being t2ie two steel shafts. The casing is

oval in cross section, having the discharge and inlet openings

either in the top and bottom or in the two sides of the machine.

In the latter case the impellers are placed one above the other.

The impellers are made of cast iron and are turned up upon a

machine especially designed for the purpose. All the curves of

the external surfaces are true circles. Gearing is placed on the

end of the casing and the driving pulley is keyed to one of the

shafts. The largest sizes of this blower are capable of discharg-

ing nineteen thousand six hundred cubic feet of air per minute at

the pressures used in cupola practice.

The Green 1 s Rotary Blower.

The Green, as well as the Connersville blower, is almost exact-

ly like the Root blower. As is shown in the drawing the impellers

of the Green b.lowar are different in design and two rollers are

keyed to each s riaft to prevent the impeller from pounding, should

the bearings wear, the shell, gearing and other details are

almost identical with the Roots. Twelve sizes a*e made capable

Plate Y

\

Plate YL

/3

of discharging up to 15000 cubic fset per minute.

The Connersville Blower.

All other details of this blower besides the impellers are

the sane as the Roots blower. The impellers of this machine are

flatter at the ends and thicker at the middle. This blower is al-

so made in si7.es capable of discharging up to 15000 cubic feet of

air per minute.

In the records of the British patent office the rotary

blowers and rotary engines are described in the same volume.

The rotary blowers are divided into three classes, "cresent shaped

chamber types" such as the Mackenzie and Riechhelm blowers,

"annular chamber type" such as the Disstons and Baker blowers, and

the "Root blower type" such as the Roots, Green and Connersville

blowers. Some eight or ten hundred machines are patented as blow-

ers, rotary engines or both.

TESTS OP ROTARY BLOWERS.

Only one set of tests of this character was found. This was

a set of tests by Prof. H. M. Howe on trie "Coraparit ive efficiency

of fans and positive blowers" given in the transactions of the

Institutte of Mining Engineers, Vol. 10, pg. 482.

The experiments were undertaken with the idea of proving that

the Baker blower was more efficient than the fan blower. The

results, much to the suprise of the authors, proved that the fan

is more efficient than the Baker Blower for pressures as high as

twenty ounces per square inch. The air was measured by noting the

pressure of discharge through one, two or three six inch circular

Plate JZLL

C on tie rsvi lie Blower.

16

orifices and calculating the volume from these results. In com-

paring the results they are all reduced to the discharge through

one six inch circular orifice. A No. 4 1/2 and 5 1/2 Baker

blower, a No. 1/4 Root blower, a No. 10 Sturtevant fan and- a "G."

Hawkins fan were tested and the results plotted. The results have

been copied and are given on an accompaning sheet (see pg./jT ).

In his conclusion he says fans and positive blowers are more

efficient when working near their maximum capacity. Therefore,

when a great variation of quanity of air is required, a number of

small blowers would be more efficient than one large one. The cost

of positive blowers is about four times that of fans for the same

capacity. The Baker blower shows about ten per cent less effi-

ciency than the fan blowers.

This comparison is, however, severe as the pressure is some-

what lower than that for which the positive blower is designed to

work against.

Constructive Features of Centrifugal Pans.

The following types of centrifugal fansare advertised by

nearly every company that manufactures the centrifugal fan:

Steel pressure blowers,; Volume blowers; Volume exhausters; Steel

plate blowers and exhausters.

17

STEEL PRESSURE BLOWERS.

This is a form of fan designed to discharge a snail volume

of air at a high pressure. They are capable of producing a pressure

of as high as twenty ounces per square inch and are adapted for

use with cupolas, forger and some types of mechanical stokers.

In order to obtain a small volume and high pressure these fans

are made with wheels of small widths as compared to their diameter.

.

The blades are usually five, six or eight in number, are wider at

their inner edges than at the circumference of the wheel and are

curved backwards to decrease the noise of the blast. The Sturte?

vant blower is made with six full blades and eighteen small blades

of about half the length as the others placed in between the larger

ones. The blades are riveted to steel rt T" irons which are cast in

trie hub. Conical sideplates which extend from inlet to outlet are

riveted to trie sides of the blades. The casing is made of cast i

iron and is of a spiral form and usually has the discharge opening

horizontal. The shaft Is steel and is hung in two bearings one

on either side of the fan. These bearings are always large and

self-oiling, the chain, ring and wick type being used. The pedes-

tals are either cast solid to the casing or are cast separate and

bolted to the casing. - Both one and two driving pulleys are used.

These blowers can be obtained mounted on an adjustable bed plate

but are never directly connected to an engine as the relative

speed is too high.

VOLWIE BLOWERS.

This type of blower is designed to discharge a conside rable

volume of air at a moderate pressure (two to ten ounces per square

inch.). In appearance they are very similar to the pressure

blower. The casing, however, is wider and the outlet larger.

The fan blades are of an equal width the whole length and are bent

backwards the sa.:e as in thel pressure blower. Only one driving

pulley is used. The volume blower is also mounted on an adjustable

bed plate but is never direct connected to an engine. A table

of capacities of these blowers is given with this thesis..

(See pg.5"f ) •

Volume Exhausters.

The construction of a volume exhauster is similar to a volume

blower except that there is only one inlet and that 4s provided

with a flange for pipe connections. The bearings are both placed

on the opposite side from the inlet and the driving pulley placed

between them.

STEEL PLATE BLOWERS AND EXHAUSTERS.

These fans are designed to handle larger volumes of air at

lower pressures than the volume blowers and exhausters. The

casing is nade of steel plate and is ribbed with angle irons to

give rigidity. The fan wheels have one, two or sometimes three

spiders supporting eight or more blades, the number depending upon

trie size of the fan. The blades are usually made straight, but

in some cases where the fans must not . iake any noise they are

bent backwards. The discharge opening can be in any direction,

IS

top or bottom horizontal, up or down vertical, or at any desired

angle. Some fans are made with two or more discharge openings.

These fans are run at lower rotative speed, the speed depending

upon the size. In some of the larger sizes only three-quarters of

the fan is housed in steel plate, the remainder being xonstructed

of brick, wood or some cheap material to save expense. They can

be obtained with direct connected engines.

Tests of Centrifugal Fans.

"In the study of air propellers there is a great difficulty

in taking cofcrect measurements of the pressure and quantity of air

delivered if the velocity of the stream is at all great. From

this cause experiments apparently conducted with the greatest

accuracy have of ted shown a fan under test to give an efficiency of

over 100/? and therefore, general statements of the efficiency of

fans should be received with great caution."

In Vol. 123 (1895) of the Proceedingsof the Institute of

Civil Engineers a set of experiments are recorded by H. Heenan and

V/m. Gilbert. These experiments are teery unique and are the most

thorough of any that were found. They had for their object:

(1) "To determine the best shape of blade and fan case in order to

obtain a minimum expenditure of power when producing any given

output, i.e.- the best type of fan; (2) The standard type being

elected to obtain data whereby the proper diameter of the standard

fan and its most economical speed could be determined for any given

output of air af required pressure.

The arrangement of the apparatus was good, gpeat care being

taken to see that there would be no doubt as to the accuracy of

20

the results.

"The experiments proved that a fan with a few simple blades

gives the best results, provided the form of the blades and casing

are designed to suit the kind of work required. Fans of a more

complex design have too large an internal resistance to give a

high mechanical efficiency, although they may have to be used if

high pressures are essential."

Four different blades having different tip angles and differ-

ent angles at the inlet, were tested in a fan of the ordinary

design. A b n ade having a backward slope at the inlet and then

bending until it is perpendicular to trie circumference was found

to give the best results and to maintain a high pressure as the

volume increased but when the discharge approached close. to the

maximum it dropped rapidly to zero. A blade which sloped back-

ward the whole length gave considerably lower efficiency, and

allowed the compression to decrease rapidly as the volume increased.

In the transactions of the American Society of Mechanical

Engineers a set of experiments are given by H. I. Snell on a

Sturtevant blower 23" in diameter and 6 5/G inches wide, inlet

12 1/2 inches in diameter on both sides, and eight blades having

an area of 45.49 square inches.

The air was discharged through a conical tube with sides

tapered at an angle of 3 1/2 degrees. Vena contracta 80^.

2/

TABLE OP TESTS OP PANS BY H. I. SNELL.

TheoriticalV U X UiiltJ V U x UiiitJ volume that can

R. discharge Press

.

of air per be dischargedNo r . . . . In C\7 t, p >• m i n H P H P per rain. H.P. Eff

.

1X 1519X X %7 o 3 50 o . 80 1048 •

2*-* 1479 3 . 50 406 1 . 15 353 1048 .337

3 1480 10X w 3 . 50 676 1.30 520 1048 .496

4 20 3 5*0 1353 1 95 6 94 1048 .66

5 1485 28 3 . 50 1894 2.55 742 1048 .709

AW 1485 36 3 . 40 2400 3 . 10 774 1078 .718

7 1465 40 3.25 2605 3.30 790 1126 .70

8 1451 44 2.88 2686 3.50 767 1277 .601

9 1468 44 3.00 2752 3.55 7 75 1222 .665

10 1415 44 2.75 2636 3 . 30 799 1333 .60

11 1415 48 2.75 2873 3.45 833 1333 .613

12 1500 48 3.00 3002 3.80 7.-J0 1222 .646

13 1471 48 2.888 2938 3.70 794 1277 .626.

14 1426 89.5 2.38 3972 4.80 827 1544 .536

22

Exper iments to dertermine the effect of speed of Fan.

R Volume inp . 11

.

Pressure o£. cu.ft. per min. H. P. Ef f

.

600 .50 1336 .25 .72

800 .88 1787 .70 .61

1000 1.38 2245 1.35 .62

1200 2.00 2712 2.20 .67

1400 2.75 3177 3.45 .69

1600 3.80 3670 5.10 .74

1800 4.80 4172 8.00 .68

2000 5 . 95 4674 11.40 .66

In his remarks on the tests, he says, "The greatest efficiency

when the discharge is free and open and the area of inlet opens

equals the capacity of the fan wheel."

Prom experiments already given it will be seen that we may

expect to receive back 65 to 75/b of the power applied and no morel'

There is a great variation in the opinion of different author-

ities as to the efficiency a fan will give. In the experiments

before refered to be Heenan and Gilbert, mechanical efficiencies

as high as 90^f are shown. Prof. Carpenter says that any test that

shows over 50/S is probably in error while these experiments of H.

I. Snell show as high as 14%. Weisbach and other authorities

give only about 30^f.

23

Series of Tests on Centrifugal Fan in Mechanical

Engineering Laboratory, University of Illinois.

The objeet of this experiment was to obtain a complete set

of data which wo*ild show what the fan was doing under all possi-

ble conditions.

Description of fan: The fan was a Buffalo Forge Co's "No. 8

B. Volume Blower". It is advertised, for use with boilers, heating

furnaces, forges and etc. The principle dimensions are:-

(See drawing plate JQU ) .

Height--- 48"

Length 47 1/2"

Total Width. rr 40"

Diam. of pulley 8 1/2"

Width of " 7 1/2"

Diam. of wheel 28"

Width " " 11"

No. of blades 5", curve back 3"

Size " " 11 "x9"-- shape

Area of blades 88 sq. in.

Diam. of outlet (cutside pipe flange) 16 1/2"

" " (inside):

15"

Area of outlet 132.7 sq. in.

Diam. of inlet ( pulley side) 15 1/2"

Area of inlet ( pulley side ) 86.4 sq. in.

The area of pulley was subtracted as it obstructed

2 3/1

/

2i

the inlet.

Diam. of inlet (opposite side) 13 1/2O It

Area of inlet (opposite side) 119 sq. in.

The area of bearing being subtracted.

area of inlet.Ratio 1.56

area of outlet

Diam. of shaft

Length of bearings

1 3/4"

— 9" (ring feed type)

Distance between bearings 28"

Arrangement of apparatus:- This fan was at first belted to

the Ball engine. This engine is supposed to be run at about

320 R. P. M. and has a fly wheel of 36" diameter. It was thought

that the engine could be speeded up until a proper belt speed

was attained buttthis was found to be impracticable. The fan was

t en attached to the Myer engine. This engine has a 54" fly

wheil, and is designed to run at about 250 R. P. M. But by pro-

perly arranging the weights on the governor arm and changing the

ratio of the governor pulleys the engine was made to regulate to

any desired speed.

Fourteen feet of 16 1/2" galvanized iron pipe was attached

to the outlet of the fan. A Buffalo Forge Co., gate was placed

in this pipe four and one half feet from the fan. In this gate

were placed tin slides having different sized orifices. At firdt

this gate was placed about six inches from the fan but the

static pressure was found to vary considerable in different sec-

tions of the pipe and hence it was thought best to place the gate

some distance fro the fan.

1L

27

The static pressure was measured in the pipe about ten inches

behind the gate. The temperature was also taken inside the pipe.

As the dynamic pressure varies considerable in different sec-

tions of the pipe a special device was made whereby one reading

could be taken which would be approximately, if not exactly, an

average of all the pressure in the different sections. This device

shown on plate IX 5consisted of nine bent tubes 1/4" in diame-

ter which extended into the pipe and opened into the current.

The ends of these tubes were so placed as to obtain the velocities

for different but approximately equal areas of the cross-sections

of the pipe. A hollow ring extends around this pipe and into this

the tubes opened. This hollow ring acted as a chamber for aver-

aging the different pressures. The action of this arrangement

was supposed to be thus:- If the pressure in one of the nine tubes

was greater than in any other then a flow of air would result,

going in at the first tube and out the other until the pressure

in the ring was an average between the pressures in the two tubes.

The same action taking place between all the tubes would give a

pressure in the ring which would be an average of all the pressures.

A rubber tube was attached to this ring and to the pressure gauge.

At first an attempt was made to measure the pressure by an

ordinary ^itot tube ("U 11 tube) and water but this was found to fluc-

uate very rapidly, thus making it impossible to obtain a reading

closer than to 1/4 of an inch in water. A slanting tube was then

tried but it also showed the same difficulty. Two gauges were

then constructed on a plan given by Wm. Kent in Vol. 10, A.S.M.E.

The gauges were exactly alike except that the one used to

2.7/g.

g2&

Plate U

-16

Wafer-11.3

Sca le bed\ g^Bg

Detail^) of Gauges

and

Device for obtaining dynamic pressure.

loo

Scale '/&

f\<r-Spout for attaching Gauge tube.

£3

j

measure the static pressure was 24" high while the other was

only 10" high.

For each gauge two pans were made, one having a diameter of

about 16" and the other a diameter ( //. 5 ') such that its area

was 100 square inch. The height was 24" for one gauge and 10" for

the other. The 16" pan was half filled with water and placed on

the platform of a pair of scales. The other pan was inverted

inside this and fastened to a frame which in turn was fastened

rigidly to the floor or table on which the scales rested. Care

was taken to see that there was no contact between these pans.

A rubber tube led from a spout in the inverted pan to the blast

pipe. The pressure in the blast pipe passed through the rubber

tube into the inverted pan and thus exerted a downward pressure

on the water inside the pan. This total pressure was weighed on

the scales. This result after being divided by 100 gave the

pressure per square inch accurately to the second decimal place.

In taking readings one person took the speed of the engine

while another took that of the fan, hand speed counters being used

for both cases. Immediately after taking the speed one person

took the indicator cards while the other took the readings from

the gauges, thermometer and barometer. Seven readings were taken

for each speed, one for full discharge, one for no discharge and

five for intermediate discharges. Duplicate readings were taken

in each case.

The method of figuring the volume was as follows:

Let V a veloc. in feet per min. of the discharge .

V ~60[/2 gh where h-=. head in ft. air column.

29

T)

h a? .) when p =- pressure in ounces per sq. in. andd

d ssr density.

. . Vx= 60 x 3 x 802d

Let B zr barometer reading in inches of mercury.

T =z temperature in Pahr.

1.3253 (§ BDn- from Kent.

460 +• T:

Vrr 60 x 3 x 8.02(460 + T) P

1.3253 4- B

3 1254.12(460 + T) P

B

Q-zz volume in cu. ft. per rain.

Q.~ 1.39 X 1254.12(460 + T) P

B

- 1743.2(460 -t T ) P

B

1.39 z area of pipe when veloc. press, was taken.

The power used was determined from the indicator cards

taken from the engine. No attempt was made to separate the power

used by the fan from the engine friction, the engine and fan

being considered as a unit as they would occur when in use.

The results for each speed were plotted. The volume in cubic

feet per minute was layed off as abscissa and the compression in

ounces per square inch, the total pressure( static plus dynamic),

the engine H. P., the blast H. P. and the mechanical efficiency

as ordinates.

30

In each case the static pressure at first slightly increases

with the volume and then drops radidly as the volume increases

until the gate is wide open when it becomes zero.

The engine horse power gives almost a straight line.

The horse power represented by the bla&t ( which is the total

pressure into the volume) increases with the volume when the

pressure is high, but when the pressure becomes low and the volume

large it drops off suddenly. This drop is probably due to the

increased friction which the air encounters in passing through

the fan. The efficiency curves also shows a similar drop, which

also indicates that there is considerable lost power when a large

volume is discharged.

Another set of curves is given where the volume is plotted

against the speed. These show cleanly that the volume varies as

the speed.

DATA & RESULTS FOR TIP SPEED OP 14000 FT. PER MIN.

R. Vel. Stat,. Blast Eng.No. P.M. Head. Bead Volume Temr . Bar. H.P. H.P. Eff.

|0Z. PER iq, in.

1 1900 2.26 11145 72 2.93 6.84 38. .18»

1905 1.08 4.80 7704 72 " 12.35 29.6 .415

3 |905 .63 6.624 5884 72 " 11.64 25.6 .462

S }900 .05 9.25 1688 67 " 4.28 14.8 .282

5 1895 8.25 67 "0 8.8 .0

Blast MP

TolalPress

brat/c Press.

1000 2600 5000 WO 5000 6000 7000 BOW 9000 7000 //0\

Volume in cu.ft. per mm.

30

28

26

2f

22

20

18

16

li

12

10

6

2

SO

60

70

60

50

fO

30

20

10

6

6

5

/

t 4

33

DATA & RE oriT 70• j iv 'j J. o wn tiprun ji l j • Ji rj i ,1

)

OF 13000 FT. ppp *JTTTJ1 M i. a .

R Vel. Vol lima Blast Pin nf

No. P.M. Head Head Tenn . Bar. H.P. H.P. Eff

.

OZ PR. 5 a?. I ri<

1 1760 1.91 10340 73 29.0 5.37 29.8 .181

2 1773 1.94 10320 73 it 5.46 29.9 .186

3 1780 1.46 2.12 8957 74 it 8.75 28.3 .31

4 1778 1.47 2.13 8988 74 ii 8.82 27.7 .319

5 1780 .99 4.17 7392 73 n 10. 40 25.1 .41

6 1765 .94 4.16 7187 73 ii 9.996 24.4 .41

7 1778 .53 5.73 5385 71 ii 9.21 22.2 .415

8 1781 .54 5.76 3631 71 ii 9.25 22.3. .439

9 1769 .24 7.26 3555 71 ii 7. 49 17.8 .406

10 1768 .23 7.20 1284 68 ii 7.20 18. .40

11 1769 .03 7.84 1284 69 it 2.76 12.9 .213

12 1770 .03 7.82 69 it 2.75 12.8 .214

.13 1773 7.37 70 ii 9.

14 1778 7.39 70 ii 8.6

I l l llll l l l ll l l ll l llllliii i i mn i i i m ii ii i i

Character/ stic curves of a

Buffalo Forg e Co !s Vtilum e Bio wenftp spe ed of blades 15000 ft. per in in.

«En$. H.P

Blast H. P.

Total Press.

Efficiency

Static Press.

2000 3000 1000 5000 6000 7000 8000 9000 ICOH UOOO

volume in cu.fr. per min.

3D

26

26

21

22.

20

18

/6

If

t2

10

6

6

90

2

80

70

60

50

to

dO

20

10

to

O

8

JL

6

5

3

2

I

EUGENE DIETZGEN CO.. CHICAGO

DATA & RESULTS FOR TIP SPEED OF 12000 FT. PER MIN.

35

No.R.

P.M.Vel.Head Head Volume Temp. Bar.

Blas^H.P.

Eng.H.P. Eff.

1 1640 1.49 9150 84 29.3 3.71 25.2 .147

2 1635 1.49 9150 85 h 3.71 25.1 .148

5 1610 1.20 1.50 8210 84 M 6.04 21.7 .278

4 1628 1.20 1.52 8210 83 II 6.09 22.5 .27

f> 1640 .81 3.42 6740 85 II 7. 77 20.7 .3 75

6 1650 .82 3.45 6790 86 II 7.90 19.9 .397

7 1620 .45 4.86 5030 85 II 7.26 17.1 .425

8 1630 .46 4.82 5080 85 II 7.31 17.1 .428

9 1625 .19 6.08 3270 84 II 5.58 14.6 .383

10 1622 .20 6.12 3350 84 II 5.78 13. .445

11 1630 .03 6.64 1300 84 II 2.36 9.7 .244

12 1650 .03 6.64 1300 84 II 2.36 9.96 .237

13 1635 6.03 84 II 6.76

14 1648 6.16 85 II 6.34

Characteristic curves a/ aBuffalo For ge Co's Volume Blower.

Tip speed cf blades 12000 ft. pe r min.

Eng. H.P.

EUGENE DIETZGEN CO., CHICAGO. 'olume in cu.ft. per min

9

37

DATA & RESULTS FOR TIP SPEl'JD OF 11000 FT. PER MIN.

R. Vel. Stat. Blast -Eng. Eff

.

No. Head Head Volume Temn . Bar

.

H.P. H.P.1 1505 1.37 8753 84 29.3 3.35 17.7 .189

2 1502 1.37 8753 84 ft 3.35 18.3 .186

3 1500 .99 1 . 20 7445 83 w 3.53 17.6 .200

4 1430 .99 1.20 7445 83 rl 3.53 16.7 .211

5 1498 .65 3.09 6032 83 ri 6.15 15.0 .41

6 1495 .63 2.90 5926 84 it 5 . 70 14.1 .405

7 1500 .37 4.05 4551 82 it 5.49 13.7 .40

8 1500 .37 4.08 4551 82 ii 5.52 13.5 .409

9 1500 .16 5.17 29 96 80 it 4.36 11.7 .373

10 1500 .17 5.34 3085 80 ti 4.64 11.6 .4

11 1490 .02 5 . 23 1058 81 ii 1.51 8.2 .188

12 1504 .02 5.34 1058 81 n 1.55 8.0 .194

13 1490 4.86 77 n 5 .00

14 1498 5.02 78 ii 4.96

Crja rakteristic curves of aBuffalo Forge Co's Volume Blower.

Tip speed of blaes uooo ft per mm.

Eng. HP

_ Efficiency

\Biast HPTotal Pressure

- Static Pressure.

to

2*

22

20

18

[6

ti

12

to

8

tOQQ ZO00 dOOO fOOO J0O0 6000 7000 80OO\90OO /0O#O M600EUGENE DICTZGEN CO., CHICAGO

2

90

80

70

60

60

fO

30

20

/0

ol ume m cu. ft. per mm.

oCO.

<b

CO

<i)

9

8

7

6

5

1

3

2

XI

o

4

39

DATA & RESULTS FOR TIP SPEED OP lOOOO FT. PER MIN.

No.R.

P.M.Vel.Head

Stat.Head Volume Temp

.

Bar.BlastH.P.

Ens.H.P. Eff

.

1 1360 1 . 12 7919 79 29.3 2 . 43 15. .164

2 1368 1.13 7954 78 it 2.44 15.4 .158

3 1355 .82 .928 6776 80 „ 3 . 23 13.28 .244

4 1356 .82 .934 6776 78 3.23 13.5 .240

5 1365 .53 2.32 5447 80 4.23 13.0 .326

6 1363 .53 2.32 5447 80 ii 4 . 23 12.6 .336

7 1365 . 30 .5 . 296 4u y y oU 4.01 11.1 .360

8 1366 .30 3 . 248 4099 80 4.01 11.1 .360

9 1365 .12 4 .048 2592 82 2.94 8 .

6

.342

10 1360 .12 4.080 2592 83 2.97 8.5 .35

11 1368 .01 4.656 748 85 .95 2 7.4 .129

12 1372 .01 4.608 748 85 .921 7. .132

13 1370 4.288 85 4.6

14 1368 4.288 85 4.3

ume in cu.ft per mm

DATA & RESULTS FOR TIP SP'iEJ) OF 9000 FT. PER MIN.

No.R.

P.M.Vel

.

HeadStat

.

Head volume Temp

.

BarBlast

. H.P.Eng.H.P. Eff

.

1 1226 .90 7123 81 29.1 1.75 11.4 .153

2 1223 .96 7123 80 n 1.75 11.3 .155

5 1228 .64 .832 6007 81 it 2.41 9.88 .244

4 1228 .61 .800 5864 81 ti 2.25 9.68 .235

5 1230 .40 1.840 4749 81 it 2.90 9.24 .314

6 1230 .40 1.872 4749 81 N 2.90 9.16 .315

7 1227 .24 2 . 704 3678 81 II 2.95 7.6 .388

8 1230 .23 2.704 3601 80.5 il 2.88 7.76 .371

y 1220 .09 3.328 2252 81 II 2 . 10 6 .38 .33

10 3.225 .68 3.328 2124 81 II 1.97 6.9 .286

11 1230 ? 3.632 81 »l 4.8

12 1219 ? 3 .520 81 II 4.6

13 1237 3.568 81 II 3.46

14 1230 3.552 82 n 3.8

Lharacieristic curves of a

Buffalo Forge Co's Volume Bfower.

Tip ftpeeq of nJarfe f voqo ft.\per min-

im

m

Pressure.

Efficiency

K

v.

20

18

16

ft

12

10

8

3D

80

70

60

50

10

30

30

10

SO

CO

5s

9

8

7

6

5

f

3

2

olume in cuff, of air per rn i n.

43

DATA & RESULTS FOR TIP SPEED OF 8000 FT. PER MIN.

R. Vel.

.

Stat. Blast Eng.Jr . — * Head Head Volume Temp

.

l)tXT • H.P. H.P. JtliX 1 .

J. .73 6325 64 99 ^ 1.26 8.1 1 RA• JL O O

o 1 D 94. .72 6282 64 If 1.23 8.12 1 5 9

1 n 9 P .52 .688 5339 63 tt 1.61 7.3 99

A*± .54 .688 5441 63 II 1.82 7.4 246

1 H9 R .34 1.452 4307 63 II 2.10 7.2 999

f. 1100 .34 1.452 4307 62.5 II 2.10 6.7 314

7 1090 .20 2.24 2951 62 II 1.95 7.1 .275

1 097 90 9 90ft fj J \J J_ ATO JLII 1 94 4 304

9 1089 .08 2.752 2094 61.5 II 1.61 4.6 .35

10 1089 .08 2 . 864 2094 61 II 1.68 4.75 .354

11 1090 .02 2.992 1047 61 II .86 3.62 .238

12 1090 .02 2.992 1047 61 tl .86 3.6 .24

13 1086 2.784 61 II 2.5 6

14 1087 ii.768 61 II 2 .

5

Buffalo Forge Co's Volume Blower,

lip speed of bfades eoooft. per min.

v.

S 20

SO

CO

o

7000 3000 3000 10000 11000

30

70

60

50

to

30

20

/0

16

It

II

JO

8

6

7

f

2

S

f

3

2

/

fS

EUGENE DIETZGEN CO., CHICAGO.

46

Discussion of the principles involved in the working

of Centrifugal fans.

In operation a centrifugal fan sets the air between its

blades revolving about its axis. In consequence of this motion

the air has imparted to it a certain amount of energy. The air

leaves the blades approximately tangent.tally to the circumference

of the wheel and with a certain velocity which depends upon the

velocity of the tips of the blades. The air after leaving the

blades will retain the energy thus imparted to it, in a kinetic

form, if the discharge is free, but if the discharge is restricted

then part of this energy will be used in compressing the air and

thus assumes a potential form.

The action of the fan upon the air should be the same as a

centrifugal pump, that is:- the air should be drawn in without

shock and should leave the blades with a velocity equal to the

tip speed.

In order to accomplish this the air should have its velocity

gradually increased as it approaches the inlet. At the Inlet no

sudden change of volume or direction of flow should occur. The

blades should slope backwards so as to gradually impart the rotary

motion to the air, and the tips should be radical so as to give

the air the full centrifugal force due to their tip speed. The

casing should be of a spiral form.

Such a fan is never constructed, as too much expense would be

involved

.

The capacity of fans, expressed in cubic feet per minute, is

equal to the cube of the diameter of the fan-wheel in feet multi-

plied by the number of revolutions and by one of the following

constants

:

For a fan with single inlet and delivering the air without

pressure #<6, when delivering air with pressure of 1 inch of water

.5_. For fans with double in lets the constants should be in-

creased by 50 per cent. (Prof. R. C. Carpenter)

.

The horse power required is equal to the fifth power of

diameter in feet, multiplied by the number of revolutions per

second, divided by 1,000,000 and multiplied by one of the follow-

ing constants: free delivery- 30, delivery against one ounce

pressure 20, delivery against two ounces 10. (R. C. Carpenter.)

4&

The following references are thought to contain the best

information upon this subject.

621.623 Efficiency of fans and blowers.

A. S. C. E.

Vol. 7. Experiments by W. T. Trowbridge and Geo. A. Souter

also to determine the volume of air delivered under

E. N. various conditions and the power required.

Dec, 11, '96.

621.623

Lon., Eng. Testing of fans and blowers.

July 24, '85.Prof. R. . Smith.

To find (1) how much wo>-k is required to be done

by a proposed fan (2) how much mechanical work is

done by a fan in place.

621 .623

P. I. 0. E. Oh the conditions and limits which govern the

30:276 proportions of rotary blowers.

Robert Briggs.

Year • 70 . (63 >. 5 d)

Gives opinions of various authorities and conclu-

sions. Good explanation of working of fan.

49

621.623

*

P. I. C . E. The design and testing of various types of centri-

123:27:3 fugal fans.

H. Heenan 8c W f Gilbert.

Dec. » 95. (55p. 31)

Gives results of elaborate experiments on the

efficiency of fans and deduces characteristics

curves that nay be employed in the design of a fan

with maximum efficiency for a given duty.

621 .623 Centrifugal fans.

Amer. Inst. R. Van A. Norris

.

"in. Eng.

20 : 637

Year' 92. Twenty-nine tests of nine ventilating fans:

tabulated data and results: discussions.

621 . 623 Investigation of a blowing fan.

E. R. Prof. R. C. Carpenter.

39:310

Elaborate test conducted at Cornell University.

Numerous curves of working of fans with different

shaped blades.

621 .623

H . & V . Same as above

.

IX : 2 : 7

Feb., '99

Theory of centrifugal fans, or rotary blowers.

Prof. R. C. Carpenter.

Deduces a theory. (Hves theoretical formulae for

the volume and horse power required. A simpleJj

practical formulae for volume, also one for horse

power required.

Methods of testing blowing fans.

Prof. R. C. Carpenter.

Gives descriptions of numerous methods of measur-

ing pressures. Opinions of each method. Cuts of

different gauges.

Efficiency of fans and blowers.

An editorial in which a new formula for computing

the H. P. is given by Prof. Herschel. Discussion

by W. C. Nnwiji.

Experiments and experiences with blowers.

H. I . Snail.

57

Year '87. (22p. li, 5t)

lUves tables of experiments and aethods of taking

same. Metriod of piping. Two fans should never

discharge into same pipe.

621.623 .

P. I. C. E. Manometer and mechanical efficiency of fans.

66:271

Explains and discusses above. Gives formulae.

621.623

A. M. Power required to drive centrifugal fans.

19:1218

(2p. 2 i)

Dec. 31, '96. Results of tests by Interior Conduit & Insulation

Co., who furnished motor.

52

Size.

55fO_\

55_

S.PPM. 603 X f& 603&X5& 70_

4- X6 86

5X 7/2 /0d \

5/2x8/4 110'

6X9 1207 X/O/z/lOa x 12 /6Q9 xt/z/ox 512 x 6

30"

35"

ffl

-ML55"

SRP.M. 60"

3X1''A 6(L_

^Xb/f 70"

f X6 80i4/<lx6%9o"

SX7A /oo"

sJkxeft //o"

6*9 /Zo"

7X/0& /408X/2 /60"

Qjl4£/OXS/ZX6

C. S. Johi

52

Mechanical Engineering Dept. University of Illinois.

Steel Plate Fans.

Table of Speeds j Pressure in Ounces, Capacity in Cu. Ft of Air per Min. & Power Required.

Siz e.

WFeel Sg. inchesol Bid ST. 1 « fa Ounce 7r Ounce z

/8 Ounce Ounc e 5/e> Ounce % Ounce / Ounce i/f Ounces.

Diet. Width. nwRev. Cu Ft. HP Rev. Cu.Ft HP. Rev. Cu.Ft. HP Rev Cu.Ft HP

\

ReF Co Ft HP Fev\ Co. Ft. HP Rev\ Cu.Ft\

HP Rev. Cu. Ft. -d.RInlet WM In/el

wOutlet 3 2

30 /2k 16 8fr 6 36 54 17' 38 9 .0254 v / .000 O ' 7 7 Q * ICC. 777 2/5- 967 060 fO c. U A7 V5Z\ 1 /Zo .344 7700 12 90 .53 1 230 7440 7435 14 21 ?7z 67a 48 72.2 5-1' 359 610 0313 50 7 86 Z 088 6Z £ 7n AT *7/Oof ./Sc- 7/6 IZZO .25 800 7360 . 35 878 1490 .46 70/5

8Z2/7 Z 5

1

2Z60.705

927

1140 1 /920 9940I Is lb 24 1/ 7% 6 3 94 6 /)O.D Z9I r\ n .041 4/0 // J O .//35 50 3 / O ot 2.CJ O 5ro /60 .328 648 7790 95S 7/4 I960 .603 12% 2520 1-293

T~> 18 27 /zti 9/z Pi T V /pa 7-7' 258 108 5 .0556 364 75 30 .1560 4 7 6 /b°8 .288 517 Z/do 474 575 2430 .62 634 2660 .816 73 Z1

30 70 726 920 3420 7.76

TV? 21 30 ISjk 70/, lO 2 5 1^4/ *S ' 7 85 233 1 300 X>667 329 78 1~0 .188 403 2260 347 46 5\ 26IO .533 5ZO 2920 745 570 3/90 980 660 1 36 90 7.5/ 738 4/ZO 2-1/

OJ 22\

33 15% 71% lei 9 1 94 O.p 213 762 .08 4- 300 23 20 .23/ 368 2840 .437 424 3280 ,6 7Z 366O .948 521 40 2 1.23 60 z 46 40 /. 90 674 5/90 2-66

Q PP M An 24 36 /67s 727* 74 8 223 /i

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26603200

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367

285

326039Z05150

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389

389

333

3760 .772

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722

434

43f372

420050606650

1. 08

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3889646.1

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551!

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7760 3.74~z JA v £r// *73/^X5/4- VO4 X6 lid.

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5380 55~ 2 54 6600897070700

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/O/OOO

49867.3

80.5

706.

/4I.5

/88.0

207.

10109/e

2670036400

65.5

88-8

706.

73 9.

786

247Z7Z

7//0

985878807737

63/555

289004020046800^6/500

81500

/09000/20500

47?.x67*9o" 450 7843000 I1L_

^5L*7fz /od5/zX8% //o"

404369

2/40O28/00

<

572004-970055000

43 7

_398364

3IZ274

23/0030 3 OO

76S2/7

8/4 43300 50200 /64

74 Z 56800 658008730077700072 9

2/6

2883834ZI

6x9 /Zo" 338288254

40200 ,28.8

53800 \38.6

59400 42.4

68Z5/3454

7530O

7OO 300

7/1 000_7X/o7i 1408X/2 76o"

9X4%. 225 70200 43.3 243 75900O^Tnn

ft*68.5

77 6

JLAO^

231796

81loo 66.7 29/ 52/

2 88240

J)98POI26Z00178 000

IA30^

154.0

ZZO.o

537

Q

33Z278

11500074350O

moZ36.0

j414372

/28500

/63 500266.

334.

45440834Z

742000

179000254000

349440

623

49Z44Z370

/53000,

I93100_276000

±t—- m

442. 527 764000 540

10X5/2.X6

202/69

885QQI26OO0

515774

9 IS 702500/46 000

89.

7/9,0

261

218

7/400(5

762 00

556788

973 207000 680

7351 736000 207000 338.0 3/Z 2.32000 4 73. 396 29500L» 965

V. V. \7Vhee7

* ? Diarnefe/ 1

Inlet

8/4 i

o 9%7

2

4%7

/0/S 3

12/4 4

71% 33 8%f 70 77/z t

5 //h 20 ;

6 /t/z7 76 27 j

8 /S 37 7

9 2/ 40 A

70 2f 46 :

3 Ounce2/o 4200 2

5S607 3780 3~

2 2840 8

3 2360 //!

+ J980 7Si

5 7740 20

6 7475 367 1290 52

8 1120 77i

9 865- 77 7i

70 75~6 76/

c

80uncz/o 688

O

3.

5820 6

7 5220 St

2 4640 73*

3 3870 79i

4 3266 2/"t

5 2850 34'

6 2430 60i

7 2020 668 /860 1179 7420 19370 7240 265

Horse

C. S. John

Mechanical Engineering Dept University of IllinoisTable of Speedsj Pressure /n Ounces, Capacity in Cubic Feet per min. & Power Fiequi red.

1>

Whee/ S q

.

'n. of

st:DW+2

3=

<o >

^ Ounce. / Ounce. //z Ounces. 2 Ounces. 2 /2 Ounces.Diameter VV id. th

Inter Wfieei Jtt/et Oot/eT

B la

3 Rev. Cl/.Ft 7/.F Her-. Co*. Ft. 77.P. He 17. Co. Ft. H.F. Re v. Cu. Ft. H.P. Rev. Cu. Ft. H.P

7

T //Q u/4 2 //i7 fa./ '4 3-44 5.76 2./

6

7695 8 73 .0/7S 24002050

724234

.0504

.0955

2940 757 .707 3400

28802530

17533/475

/ 4 3

.2 71

.389

3800oliO

2880

79536 9

52 8

200

.37£

.593

5 //6O 3/.

At , 22 9/,,^ 7/6

6-5

9.329-75 2 '.55

2'.85

7435 76 5 0357 2490 286 J7/78 /U/S 3/t6 74.0 /285 237 ,0484 1820 336 13 7 2230 4/0 .29/

2 7/ I<z74

74%

4 77o7/2

5%O 7/6 13.5 20.3 320 //40 34 3 .0 70 1620 48 5 .199 7980 594 .422 2290 668 .564 2560 JL6 7 .787

54

.

567'

89

JO

TPS 19.0 2.8.

6

3-85

4'.57

950800

48 3 ^019^135

1350

1130

68 3

943.280

.586

7650

/3908 35

7/60595.8 2

/9/0

/60

96 7

/ 3 40

769029 90

7957-70

7-39

245

2/30

/790

1570

1550

/080 /•//

/O 77/z 6% f/2. 26.3 39 4 667 /490/88O33 30

/'53

/.9f

3.42.

7//f 20 7/z

d/8s7/29/4

33.25~8.7

So.o88.2

5-226'.74

700595

843.1490

.773

.305

994842

7/902//0

.490

.865

7 22

/220

/030

902

_7462.580__

3670

7 047 8 4

2.6

14/0

1/90/f/z 23/

76 27 //i 83.3 /2 5. 703 520 27 16 .432 736 2990 1040 4250 3.48 f/60 47 30 485/6 37 77 113.7 /70.5 8'/0 452

348ZR90 .590 640 4080 7.67 684 5000 3.54 907

700

58 10953

4- 757.78

JO/0

780

64 40/0 6OO

6 60

70.92/ 40 74 187. 280. /0.5 A750 .97 493 67 2o 2.74 _604_ 8230 5822f 46 20 76

5/4 257. 386. J2.0 305 6 540 7 35 432 92 50 3.78 530 // 300 8 03 612 /3/ OO 70. 7 684 74-60 75.

3 Ounces. 3^2 Ounces. 4 Ounces. 4/2. Ounces. 5Ounce s. 6 Ounces. 7 Oun ce s.

2/o 4200 215 .264 4480 23/ .3 5 482o 250 .407 5070 2 62 .454 5400 2 79 565 5930 50 6 .75 6440 332 .95

55S0 407 598 3790 437 .625 4080 470 .77 4300 495 .861 4530 52 7 7 08 5030 580 7 42 5450 626 1.79

/ 3/8o 3~8 3 .776 3590 627 .897 366 o 676 /./O 3840 7/0 1.2 4 4-/00 755 /55 4500 352 204 48 80 897 2.58

2

J4

2840 84 5 /.04 30 to 906 73 3260 977 7.6 3420 103O 1 78 3650 /0 95 2.24 4000 /200 2,96 4350 /300 3.74

2360 J/90 746 2,510 7230 783 2770 7375 2.Z6 2800 /450 253 3030 7540 516 3320 /6 9 4.77 3620 /8 30 5.45

1980 7640 2.02 2.110 /770 252 .2280

Zooo

79oo 3.11 2400 200O2530

348452.

2560 2/30 435 2800 2540 573 3O40 2530 7.25

56

/7fO 2080 2.56 7850 2250 3.2 Z4/o 3.94 2100 2240 2700 553 2450 2 970 7.28 2600 3200 9.20

7475 3670 4-5 /570 3940 5.65 1700 4250 6.95 1780 4470 780 J900 4760 9-75 2080 5220 12.8 2260 5650 7627 1290 5200 6.4 /380 56 OO 8.0 7490 603O 9.37 /560 6350 J/.C /66O 6750 138 1820 74 20 78.2 /980 8030 25.0

39

/<?

1120 77OO 8-73 72O0 7620 /0.9 l29o 625o 73 45 /350 8640 /5. 7460 9220 /8.8 16 00 JO/ 20 255 /740 /0 90O 3/4865 J7 700 /4.3 920 /2600 17.8 995 /55vo 22/0 (OfO 74200 24.8 ///o 75200 3/0 12Z0 76700 40.8 /520 78000 5/.S

75~6 76JOO /9.8 806 17300 24.7 870 7860O 33 5 9/2 /9600 341 875 20800 42.7 106 5 2290O 562 //60 24800 7/0

8 Ounces. 9 Ounces. 70 Ounces. 1/ Ounces. 72 Ounces /3 Ounces. /4 Ounces.z/o 63SO 355 1/6 7325 377 /. 39 7680 398 763 81oo

]

4 19 788 8470 437 2.15 8850 458 2.41 92ZO 475 2.73

/

5820 670 2/9 6200 7/3 2.62 6520 752 3.63 6870 79/ 3.56 7180 826 4.07 7500 865 4.60 7620 8 98 5.15

5220 960 3.15 5550

4950

/0 20 3.77 5530 /OdO 443 6/40 1130 512 6430 // 85 5.83 67/0 J 240 658 7000 /2 90 757

2 4640 /390 4.57 7460 545 5/80 /56 6 642 5470 /6 40 740 5720 1720 85 7 5970 J800 9.55 6ZZC /86O /0.7

3 3870 /960 6.45 4120 2080 770 43Z0 2200 9.04 4550 23/0 7043 4760 2420 J/9 4960 2350 J3.S 5170 2620 151

4 3260 2/70 8.88 3460 2880 70.6 3640 3050 12.45 3830 3200 74.4 4010 3340 /6.4 4/80 3500 16-6 4570 36 30 20.8

5 2850 3440 11.25 3030 3650 /3.4 5/80 3860 /58 3360 4050 78.25 3510 4230 20.8 3660 4430 23.6 38 ZO 4600 26.4

67

2430 6050 19.80 2560 6440 23.7 27/0 68 00 27.9 2860 7740 32.2 2990 7450 36.7 3/20 7800 4/.

6

3240 8/60 46.6

2020 660O 282. 2250 9/50 337 2360 96/0 39.5 2490 /0/3O 456 2600 70600 52.1 2726 1 / 1 /OO 59.0 283C 1 //500 658

8 /860 11720 38.4 1980 /Z5-00 46- 2050 /3/ 50 53.8 2/60 I380Q 62.2- 2260 74400 770 2360 J5J0O 80.2 2460 258 OO 898

9 /4Z0 I93O0 63.0 J'500 20500 75/9 /580 Z/600 88.5 /670 2280 /0 2.0 1740 23800 117.0 7820 2450 I32.C ' 18 90 256 748-0

to 12.40 26 50 87.0 1320 28 ZOO 7J4.0 7380 29800 /2Z-.0 1460 3/30 74/.0 1525 326QO 16/. /530 39ZOO /62.0 /660 35500 20AO

Ho r 5e Power Co IculatecL at ^-) w2. IOu.Fr. ca IculaTed at ^ fD- diameter of yvnee/ & W- wieft/t at ci rcum.J

_ _ ^ ec. m _ at 5~

C. S. Johnson (Thesis) T̂ Je <*s compiled b r 3.F. Sturtevaat for 'Monogram 0fo*erS

1 i mm * * iit*--'-* * 4 *

* * § | # m 44 * * 4 * 4

'

*m *'* i§i nil * * *

,

* *. i i

* 4 4 - 4 4-4,4,4^-***4 4 4-*'*- * 4'- 4 * * I * 1 1 1

i I f * 11 * * 1 1 1 1 * + * |I * §M * * * - * * * I tetel *

+ * + + *4* + * + * + 4* +

+ * * +t§|l m * * *AI////'7

Ufa

i i I I I i I I I * i 1 i * iI I * I n i * * i

* 4- 4 ,4 1 # *' *% * 4

§ ' § ' 4. 4 I§ * * * | I

~ W, ^ ^ '

~^ Hp it

ip i IlK^P^B * * * * * * 1 1III I ! * .4 I • I * 4 4 I I * * |i I n * i * i * * * * * * * il 4 ^ , i * 4 4 i | i

* -4 *S% Hill 4 * I * lit *

i i i i.4

-* 4 *

. t Ml* j§S 4 4 I ,4 #j 4 4 * I * * ****************%**4 4*4*^*** + * *

4 4 4 4 4 I • 4- 4 .4 * * * * * 4| | i 4 I | I .4 * * * - § -* 4

4'* 4 * * * 4 4 § * f f * * *

-4 If I I ;4-:4 4,4 4, *>".. 4 4 *|j* ' 4 . 4 * § 4

,

* 4 * * I * * * *

* * I 4 4 4 ' * * * * 4 * * * *. 4 -4 * : 4 -.-4-^;* - -4 -

. 4 I - I • I § + ;

.-+<-. *

& -; 4-

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^ * *

|| ||.

*

i § 1 |* |

^ Ik 4-

|| * I |*. * H

* H Iter?

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