teem in asia ore and fred erryfield y: 7331 usa ! ies are...

teem in Asia

ore and Fred erryfield

Y: State University

7331 USA !

Paper co ies are $ 1.00 plus postage to your CO try e

eriment Station

ission of Oregon State

microfiche document in any e same restrictions as those

document.

Y

ORE rofckor of Civil Engineering

and

ED MERRYFIELD ’ cssor of Civil Engineering

cries a 25

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,

,

I ,

1 ,

ngineering Experiment Station on State System of Higher Education

regon State College ’ Corvallis ‘_ .

BY C. A. MOCKM~~RE

Professor of Civil Engineering

and

FRED MERRYFIELIJ

Professor of Civil Engineering

Btilletin Series so. 25

February 1919

Engineering Experiment Station Oregon State S\.stem of Higher Education

Oregon State College Corvallis

TABLEOFCONTENTS

I. Intr(~~luctl~bfl . . . . . ..__.._...__. __......___.________...._.__._ _._...._.._..__ ___. __.. _._. .__._ __.____ .i 1. Introcluctor!- Statwlent . .._........._............_._..._._................._____._.._....._.... .;

II. Tl~cory of the Hanki Turhinc ........ ..____ ......................................................... 5 1. L)eccription of Turbine ..................................................................... 5 ’ -. Path of Jet through Turbine ....................................................... 1) 3. Eficienc~ ..................... .._...._........_..........~...._....._.............._._...._.....- .......... i

4. Ccnl5truction Prolbbrtions .......................... ........... ............... ...... In

( A) Rlatle Angle ............................................................................. I!)

(B) Radial R’ Im M’idth ........................................... . ............... 10 ( C- ) M’heel Diameter and Axial M’kel 11rraclth .................. 1-l (I.?) (.‘ur\-aturc of tile 13l;dc ........ .._ ............................................. 1 I ( E) (‘cntral -Angle- ...................................................... 1.;

111. lk+~gn c&i LalMrratc,r>, Turl,inv ...................................................... l(l 1 .~-~un~cd I )c~Gpn 1 jata ..................... __.,_ ................................ 11, 2. i~rcaclth and IIiameter oi \!‘l~ccl ..................... .................. 17 3. sl'ecd Of \i’heel .............................................................................. 1;

4. Thicknew of jet _____ _ ...... __ _____________.___ _ .............................. ................ 17 .;. Sparing of Blacks in \~‘lleel ...... ___._ ._................._ .. .._ _ .............. _ ............ 17 6. Radial Rim \Vidth .... .._._. _ ____________ _______ .... _ ..... _ _ .................... .._ .... ___ :S 7. Radius of Blade Curvatures ._.__ _ ____ _ .__......_ ... __ ____._______._ _ ... _____ ...... .._ ... 1,‘:

8. Distance d jet from Center oi Shaft ... ..__...._ ................ _. .. .._ ... _ .- ... lr: 9. Distance of Jet from Inner Periphery of M‘heel __.___. ... . _. ............. 18

10. Construction of the \I*heel _________ __ .__._._.____._...._.._ .............. _ .... .._.._. __ ... It;: 11. Laborator\ Tests _____ _ ._.__...._ ......................... ____ ._ ... .._ ......... .._ ..... _. .... 1s

I\‘. I )iscucGon ............ .._......._ ...... _ _ ........................ _ . ........ _ ._._ ....... _ ................. .._ ......... 1’) 1. Limitatirln> of Tests ........... .._........__......__..._._ ..................................... I” 3. PO\\ er __. ..... __ .._ __......._................._..........._ ... ._ .............................. 1’) ...... 3. Quan:it! .._..._.....-__._._......................~.~.~--..~~~~....~~ .................... _ ... ..- _ ..... 1’)

4. S;pcecl _ __.___............_.___....___. _ __._._._.....__...................__.__ ..... _. . .._....._ ............. 1” c EtiiSenc>--Slwctl __ _.... .._.__..........._..___._._.._......_.._.__ ............ ............ .._ _ 1” - 6. Efhcicncy-I'c twcr '; .._..._.._....~__.__...__..___...........................~ .... .._. .... ... -1

7. i;~lecliic Spwl 1; ....... ................. ..- .................. ..-._ .............. ... -.

1’. Tile Tnrltinc Srti/zll, ........................ ._ ............... _.._. ..................... 2.; 1 7-c-1 So/.zlc ..................................................... _. ............. 2.; 2. ( ;cn11an SCl/%k?

>r ........................... .._ ........................... ....... ..... - .)

1-J. I;w;talJatiwb .............................. .._ ....................................................... _. ........ 20

1. Euro~~can 'i'urhc- .... _ ......................... .._...._ ......................................... 31

2 .Au-,erican lnctallaticw6 .. . ............... _ .._ ............................... .._ ... .._. 211

\‘I I. C’rtnclusic 11~ 6 ... ..~._............._..._................__ ............................................. ... 2; _______._

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

Figure 16.

Figure 17.

ILLUSTRATIONS

Page

Typical Small Water Turbine Installation . . . . . . . . . . . . . . . . . . __ .___. 2

Path of Water through Turbine ._......... . ..___....... ___.. . 6

Interference of Filaments of Flow through Wheel . ..__........._.._._._ H

l’elocity Diagram . ..--_...........___~-----....-.........--....-.~--........ . . . . . . . .._........... 8

Blade Spacing _.........____.___ _ _........__...___._.._ _ . .._..._.. _ _... _ __.~......_....____..__. 9

Composite Velocity Diagram ._______________..._.._....._ _ _____.._........._...___ _ ___.__._. 11

Velocity Diagrams . . . ..___. .-___. ._.... .__. ._ .-- . . _..._.__. . ..__ __ . . . . . ._.. . __ . _. . . 11

Path of Jet inside Wheel .-_.___...._...__._...---. _ .__........._..._____...._.__.__.._........ 1.3

Curvature of Blades . . .._..._____..___._..~...._....__...__.....__.... _ _.._ _ __..._._....._ 16

Power Curves for Banki Turbine under 16-ft Head .__.___.__ __ . . . . . . 20

Efficiency Curves for Banki Turbine under 16-ft Head e . .._.__ _ .___... 21

Characteristic Curves for Banki Turbine under 16-ft Head . . .._. 22

Banki Water Turbine Built in Oregon State College , Hydraulics Laboratory .-...........__--___-----.........------~--.-.-.-..-.....~---- 23

German Design of Banki Turbine and Nozzle ._.___-____ _ ____.___....-.__ 24

Alternate German Design of Banki Turbine axed Nozzle ____.__.._ 2;

Banki Turbine Runner and Nozzle _.____..__________. _.___._ _...___..___._____________ 26

Inside of Powerhouse, Showing Jackshaft and Generator Driven by Banki Turbine .._-__- _________.______.__. __ _____..________.__.________ 27

The Banki Water Turbine 13y

C. A. MOCK~IORE I’fof~ss~r of C’ivil Engineering

and

FRED MERRYFIELD Professor of Civil Engineering

I. INTRODUCTION

1. Introductory statement. The object of this Bulletin is to present a free translation of Donat Banki’s paper “Neue Wasser- turbine,” and to show the results of a series of tests on a laboratory turbine built according to the specifications of Banki.

The Banki turbine is an atmospheric radial flow wheel which derives its power from the kinetic energy of the water jet. The characteristic speed of the turbine places it between the so-called Pelton tangential water turbine and the Francis mixed-flow wheel. There are some unusual characteristics not found in most water wheels which are displayed by the Banki turbine and should be of interest to most engineers, especially those of the Mountain States.

Included in this bulletin are diagrams of two Banki turbine nozzles as patented and used in Europe.

IX. THEORY OF THE BANK1 TURBINE

1. Description of turbine. The Banki turbine consists of two parts, a nozzle and a turbine runner. The runner is built up of two parallel circular disks joined together at the rim with a series of curved blades. The nozzle, whose cross-sectional area is rectangular, discharges the jet the full width of the wheel and enters the wheel at an angle of 16 degrees to the tangent of the periphery of the wheel I The shape of the jet is rectangular, wide, and not very deep. The water strikes the blades on the rim of the wheel ( Figure 21, flows over the blade, leaving it, passing through ihe empty space betweeu the inner rims, enters a blzle on the inner side of the rim. and discharges at the outer rim. The wheel is therefore an inward jet wheel and because the flow is essentially radial, the diameter of the wheel is practically independent of the amount of water impact, and the desired wheel breadth can be given independent of the quantity of water.

3

6 EICGISEERING EXPERJMEKT STATIOE; BITLLYTIK 25

2. Path of jet through turbine. Assuming that the cewer of the jet emers the runner at point ,-I (Figure 2) at an angle of a, with the tangent to the periphery, the velocity of the water before entering would be

V I==C(2gH)e (1) V 1 = Absolute \-elocity of water H = Head at the point C = Coefficient dependeut upon the nozzle

The re1atii.e velocity of the water at entrance, z,, can be found if ul, the peripheral velocity of the wheel at that point, is known. PI would be the angle between the forward directions of the two latter

Figure 2. Path of water through turbine.

vcldcitie5. For maxi~~~um cfficicncy, the ;tngk of thv blatle dltrultl equal p,. If .,I!1 reprcsvn’ts the blade, the relati1.e VchJcity at exit, CL’Z’, forms /Ip’ lvith the peripheral velc:city of the \vhrel at that poillt. The absolute velcjcity of the water atsexit to the blade, 1,‘2’, can be tk- tcrmined by mems of z2’, /3?‘, ad 21;. The mgle bet\l,ecn this aback lute velocity and the velocity of the wheel at this point is Q~‘. ‘The absolute path of the water while flowing over the blade AJ!? can be determined as well a~ the actual point at which the water leaves the blade. Assuming no change in absolute velocity V2’, the point C, where the water again enters the rim, can be found. V2’ at this point becomes VI’, an d the absolute path of the water over the blade CD from point C to point D at discharge can be ascertained.

Accordingly al’ = a2’

81’ = P*’ I& =P*

since they are corresponding angles of the same blade.

It is apparent that the whole jet cannot foliow these paths, since the paths of some particles of water tend to cross inside the wheel. as shown in -Figure 3. The deflection angles 0 and 8, will br a maximum at the guter edge of each jet. Figure 3 shows the approximate condition.

3. EBkiency. The following equation for brake horsepower is true:

HP = (wQ/g) ( VI COS a1 + V2 COS a~) tf~ (2)

Part of the formula (2) can be reduced by plotting all the velocit! triangles as shown in Figure 3.

V* cos a2 = v2 cos p2 - Ul w Neglecting the increase in velocity of water due to the fall 112 (Fig- ure 2) which is small in most cases,

where 4 is an empirical coeffkient less than unity (about 0.98). From the velocity diagram Figure 4,

v,= (v~COSar-zZl,)/(COSp~) t-;) Substituting equations (3 j, (4), and (5) in the horsepower equation (2)

HP output = ( WQuJg) ( V, cos al - u,) X ( 1 -I- + cos &,‘cos p11

.

8 ENGINEERING EXPERIMENT STATJOK BVI.LEI*J.J 3 25 ---

Figure 3. Interference of filaments of flow through wheel.

_---- u, Figure 4. Velocity diagram

The theoretical horsepower input due to the head HI

HP = wQH/g = wQ VJCp2g (7) The efficiency, P, is equal to the ratio of the output and input horsepower,

when

e = (2c%/K) ( 1+ $ cos p2/cos 81) x ( cos lzl - WV1 1 (8)

& = j%, then efficiency f = GC’U,/Vl) (1 + $) (cos Q1- u1/V*) (9)

I . .

THE EXNKI WATER TVRBINE s; _-- -_-_-

Considering all variables as constant except &icierK)~ :kn(l z1l/1/y, awl tliffercntiatin~ ntitl (vpating tcl m-0, then

Ur b’l . (‘0% a,/2 t w

21~1 for rnaxinwtll eftbenc)

e-2 == $C2( 1 + $)coS’ a1 cllj

It is noticeable (see Figure 4) that the direction of I’* when 211 = 3 VI cos al, does not become radial. The outflow would be radial with

u1= \Ci(l +~)](vIcosaI) (12)

only when # and C are unity, that is, assuming no loss of head due to friction in nozzle or on the blades. To obtain the highest mechani- cal efficiency, +,he entrance angle a1 should be as small as possible, and an angle of 1P can be obtained for ul without difficulty. For this value cos al = 0.96, cos2 al = 0.92.

Substituting in equation ( 11 ), C = 0.98 and 4 = 0.98, the maximum efficiency would be 87.8 per cent. Since the efficiency of the

Fig-we 5. Blade spacing.

nozzle varies as the square of the coefficient, the greatest care should be taken to avoid loss here. There are hydraulic losses due to water striking tihe outer and inner periphery. The latter loss is small, for according to computations to be made later, the original thickness of the jet so. Figure 5, increases to 1.90., which means that about 72 per cent of the whole energy was givt-u-1 up by the water striking the blade from the outside and 28 per cent was left in the water prior to striking the inside periphery. If the number of blades is correct and they are as thin and smooth as possible the coefficient $ may be obtained as high as 0.98.

4. Construction proportions. ( X j Blade angle : The blade angle /3,, can be determined from

ai, I,‘,, and u1 in Figures 2 and 4.

If 21 1=3v1 cos Ql (10) then tan P1 = 2 tan al (13) assuming dl = 16O then PI = 29O 5(Y or 30’ approx.

The angle between the blade on the inner periphery and the tangent to the inner periphery p2 can be determined by means of the following as shown in Figure 6. Draw the two inner velocity tii- angles together by moving both blades together so that point C falls on point B and the tangents coincide. Assuming that the inner absolute exit and entrance velocities are equal and because a?’ = aIf the triangles are congruent and vu2’ andvl’ fall in the same direction.

Assuming no shock loss at entrance at point C then p2’= 90c, that is, the mner tip of the blade must be radial. On account of the difference in elevation between points B and C (exit and entrance to the inner periphery) VI’ might differ from V2’ if there were no losses between these points.

V,‘= [2gh, + ( zq2]/ i 14)

Assuming &’ = 90c (Figure 7a) 27,’ would not coincide with the blade angle and therefore a shock loss would be experienced. In order to avoid this p2 must be greater than 90°. The difference in V2’ and VI’ however is usually small because h, is small, so p2 might be 90’ in all cases.

( B j Radial rim width : Neglecting the blade thickness, the thickness Is,) Figure 5, of the jet entrance, measured at right angles to the relative velocity, i 5 given by the blade spacing (t).

Sl = t sin & (15)

Figure 6. Composite velocity diagram.

Figure 7. Velocity diagrams.

,4swming /3* = W the inner exit blade spacing is knows for ever! rim width. (a ).

S? = f(r&,) (16)

A?; long as (a) is small the space between the blades will not be filled by the jet. As (a) increases .r2 decreases so (aI will be limited t>

-c2 = P’,S,;‘$ (17)

--b-P __-._ -__- -_.-. .-I_ -----.----_ -_-. _--._ I-

It is not atlvisahlc to increase the rim \vic!th (a) ovc’r this limit because the amount of water striking it could not l-low through I;O small 3 cross-section and back presswe would rewlt. Moreo\w, a rim width wh,ich would be under this limit would be inef?icient since sey- arated jets would flow out of the spacing between the blades at the inner periphery.

In order to determine the width (a) it is necessary to know the velocity ; I?‘. which is affected by the centrifugal force (see Figure 5 j,

’ 2 @l 1 -- (g)2 = ( zt1)2 -- (?I/) zz (IFI

0t (~1 j2 z- (2~~‘)~ - ( ~1~)~ = (72, j2

but Z’2 ’ = v, f .rl,/s21 = vl ( rl/r2) sin /I1 (19)

and zt:! ’ == er, ( r*,h* )

Calling x= (rJr,V

x2 -- [ 1 - (v1;‘2f1)2]x - (,v1/z~1)2 sin’ PI = 0 (20)

Tf the ideal 1.elocity of wheel u1 = ;tV, cos (Y~

then q(‘zt:L = 1 ,kos p1 (21)

.4ssuming aI = 16’. PI = 30”

then 7~1 ,:u 1 = 1 i9.866 = 1.15

fV1iZf, I2 = 1.33, approx.

1 - (EfJzf,)* = - 0.33 ; sin2 p1 = 1.!4

Then equation (20) becomes

x2 -L 0.33x - 0.332 = 0

x = 0.335

3-a = Y&/Y, = 0.66

zr, = D,

Therefore II = 0.1713, = radial rim width. (22)

n , = the outside diameter of the wheel.

This value of (a ), the radial rim width, was graphically ascertained from the intersection of the two curves (Figure 5).

(z*z’ j* = I r&)*(zf1)* + (v,)” - I %t1)* (18)

and q$ = zeL f rljr2) sin PI (19)

THE CAXKI WATER TVHBIXE 13

The central angle bOC, Figure 8, can be determined from equation ( 18) and

(LB? = bOC/2 . VI = u,,‘cos B, = u1/0.&66

r*/r1 a.66

V2) =z4 (0.66)” + 1.33 - 114

= 0.8754,

tan a2’ = q/u2

= 0.875&/0.66~~

= 1.326

a2’ =530

angle bOC = 106’

(2.7’)

(24)

(25)

5 Fiattrc 8. Path of jet inside wheel.

14 EWGISEERISG ExPEnRrnlErr STATION BVLLETIK 25

The thickness of the jet (y) in the inner part of the wheel can be computed from the continuity equation of ffow (Figure 8))

IQ-’ = v/y (26)

vg cos a*’ = 242’ = ( Q/Y* > Ul

therefore,

2= (r2/r1) VI/~ COS a1

3 ‘= 2 COS up’&/ (TJr,-) COS al

= (3.03) (0.6 js,/O.%l

= 1.89&l

(27)

(28)

The distance between the inside edge of the inside jet as it passes through the wheel and the shaft of the wheel, y1 (Figure 8))

y, = r2 sin (90 - CZ~‘) - 1.89.r,/2 - da/2 (29) since s1- -kD,

then yl = (0.1986 - 0.945k) D, - da/2 (30)

In a similar manner the distance y2, the distance between the outer edge of the jet and the inner periphery, can be determined.

y2= (c).1314-0.945k)D, (31)

For the case where the shaft does not extend through the wheel, the only limit will be y2.

For most cases k --- 0.075 to 0.10

then yl + de/2 =O.l28D, to O.l04D,

y2 = 0.06060, to 0.0369D1

(C j Wheel diameter and axial wheel breadth : The wheel diameter can be determined from the following equation,

u,=rrD,N/‘(12)(60) (32) (1/2)V, COS al =nD,N/( 12) (60)

(1/2)C(2gH)+ cosal =rDxN/@O) (12) D 1 = 36OC( 2gH)a cos al/TN (33)

Whrlre D, in the diameter of the wheel in inches and = 16O, C = 0.98

D 1 -= 862H+/N (33)

The thickness so of the jet in the nozzle is dependent upon a compro- mise of two conditions. A large value for so would be advantageous because the loss caused by the filling and emptying of the wheel would be small. However, it would not be satisfactory because the

angle of ;itt;lck of the outer filaments of the jet wc~.~ld vary c.on&l- eddy from al -- 16”, thereby increasing these losses as the thickness increased. The thickness should be determined by experiment.

In finding the breadth of the dvhvel (I,), the following equations are true :

Q = (Cs,L/l44)(2gH)f (35) =C(kD,L/144) (2gH)*

D 1 = l#Q/CkL(2gH)+

= (862/N)H+ (34) 144Q/CkL (2gH ) 4 = (862/N) HA

L = 144QN/862HKk(2gH)i

= 0.283QN/H to 0.212QN/H (36)

where k = 0.075 and 0.10 respectively.

(D) Curvature of the blade : The curve of the blade can be chosen from a circle whose center lies at the intersection of two perpendiculars, one to the direction of relative velocity zfl at (--I) and tie other to the tangent to the inner periphery intersecting at (B) (Figure 9).

From triangles AOC and BOC, CO is,common,

then (OB)2+ (BC)2=(A0).2+ (AC)“-2zACcos/3,

but AO-?-I

OB -12 -- AC=BC=p

p- [ (r1j2- (r2)2]/2rl CQS& When y2 = (O&r,) ; and cos PI = CQS 30° =0.866,

p = 0.326r, (37)

( E ) Central angle :

G/G =sin (MOO-@)/sin (90°- (4s +fll\)

=sin *S/cos (4s + /31)

tan +S = cos &/( sin & + Y2/YI)

S- 73O 28’

16 ENGINEERING EXPEIUMENT STATION BULLETIN 25 - -- _.-.-.- -_

t Figure 9. C rvature of blades.

III. DESIGN OF LABORATORY TURBINE

1. Assumed design data From the foregoing discussion by Dr. Banki, a small turbine was design&l, constructed, and tested at the Oregon State College hydraulics laboratory. The following assumptions were made subject to the conditions &sting in the laboratory. All computations are made for the operation of the turbine at maximum efficiency. Given NJ = 14.0

-H = 16.0 ft

Q = 3.0 cfs

THE BANKI WATER TUREINE 17

Assume P = 55 per cent for a small wheel

Then HP = QHc/8.8 = (3.0) ( 16) (0.55) /8.8 = 3.0

2. Breadth and diameter of wheel. If Cd.98 and k- 0.087, the latter being the mean of the values given by Dr. Banki,

L = 144 QNj(862) (0.98) (0.087) (2g)aH = 0.244 QN/H (36)

but N = (862/D,)H4 (34) then L =144 Q/(0.98) (0.087) (2g)iD,Hi- 210.6 Q/DJ/e

LD, =(210.6) (3.0)/( 16)*= 158 - ~~ ~~~

L D, (inches) (Inches)

10 15.8 11 14.4 12 13.1 13 12.1 14 11.3

Let L= 12’ be selected, then D, = 13.1”. If any other breadth be chosen, N, D1, so, and t would be affected accordingly.

3. Speed of wheel.

N- (862/Dx)H~ =(862/13.1)(16)~=263rpm.

(34)

4. Thickness of jet. Area of jet=Q/V===3.0,/( .98) (8.02) (4)= 0.094 sq ft

s,=A/L= (0.094)(144)/12= 1.13”

5. Spacing of blades in wheel.

$1 - -kD, = (0.087) (13.1) = 1.14” t = $:/sin fl , = 1.14/O-5 = 2.L8’ (1%

If only one blade at a time be assumed as cutting the jet, so that the blade spacing, t, be as shown in Figure 5, then the number of blades, n, is

n = nDJt =,~13.1~),/2.28

= 18.1 (20 were used for this experiment)

6. Radial rim width. a-O.17 D,

=(0.17)(13.1) -2.22 inches

7. Radius of blade curvatures.

p = 0.326~~ Figure 9

=2.14 inches

(22)

(37)

8. Distance of jet from center of shaft.

3'1 =(0.1986-O.MSK)D,

= 1.5 inches (30)

9. Distance of jet from inner periphery of wheel.

y2 = (0.1314 - 0.945K)D, (31? = 0.64 inches

10. Construction of the wheel, The wheel was constructed al’ the College by senior students under the direction of the authors. The side disks of the wheel were cut out of l/4 inch steel plate. The blades were made of 7/64 inch steel, bent on an arc of a curve whose radius was 2.14 inches. The blades were placed between the disks in grooves spaced 2.08 inches apart around the outer. periphery and brazed to the disks. The wheel was mounted on a one-inch steel shaft and keyed. The shaft was set in three ball bearing rings mounted in a housing of angle irons set on a heavy wooden frame- work. The nozzle was built up of sheet iron with a slide valve operating parallel to the rotor axis on a ratchet. This valve was manually controlled so that the width of. the jet could be controlled at will, while the jet thickness and the angle a1 remained constant.

11. Laboratory tests. Thorough tests were made on the wheel in the hydraulics laboratory at Oregon State College. The nozzle was attached to a large pressure tank and the head regulated on the nozzle by means of eight, four, and one inch gate valves. All the water was

TIIE BANKI WGTEW T~‘WBIIVE 19 - “.__p._ _-._ ._-__-._ -.

furniBhttd by two centrifugal pumps. The head on the nozzle was

measured by direct piezometer readings. The brake load was obtained by a Prony brake, with a two-foot lever arm on tested weighing scales. The water used by the turbine was weighed in tanks con- nected to Toledo scales. The tests were made on about five different occasions by the authors and students, and in e&h case evtry measuring device was thoroughly calibrated before being used. The following heads, measured to the center of the rotor, were used : 9, 10, 12, 14, 16, and 18 feet. The velocity of approach in the nozzle for the gate openings of full, three-quarter, one-half, one-quarter, and one- eighth varied from a maximum to a minimum, In order to bring the resu!ts to a common basis for discussion the total head, pressure plus veiocity head, was reduced to a common base of 9, 10, 12, 14. 16, and 18-feet. Data were taken at speed from 0 to maximum.

increments of 25 rpm

IV. DISCUSSION

1. Limitations of tests. The curves figures 10, 11, and 12, are limited to the test sixteen foot head for various gate openings. _ _ __

shown in this paper on the turbine under a The results of the tests

at the heads mentioned previously are discussed.

2. i’ower. The maximum power developed was 2.75 at 280 r-pm at full gate, Figure 10. The power is slightly lower than the anticipated power, while the speed 1s slightly in excess of the optimum speed. The amount of water used is only 2.22 cfs in place of 3.0 cfs as assumed. The maximum power obtained with the smaller gate openings was practically in proportion to the gate openings. Power developed under the other heads at the optimum speeds is in direct proportion to the three halves power of the heads involved.

Head in ft 9 10 12 14 16 18 -_

Actual bhp 1.17 1.40 1.80 2.25 2.75 3.30 ---

Computed by head ratio 1.19 1.39 1.82 2.30 3.31

3. Quantity. The quantity of water used under a 16 foot head was only 2.22 cfs in place of the assumed 3.0 cfs. A slight decrease in the size of the jet thickness would cause a corresponding decrease in the quantity. The jet thickness actually measured after the nozzle was built was 1.05 inches. Lack of jigs and proper equipment made the work of building the nozzle to very accurate dimensions rather

-,,/,

20 ESGIP~EEK~NC EXPERINENT STATION BVLLETIN 25

difficult, and probably increased nozzle losses with a resultant lower nozzk coefficient than that assumed.’

.Bh slight decrease in quantity occurred with an increase in speed.

100 200 300 400 REvowrmNs m MIWTE

Figure 10. Power curvets for Banki turbine under 16-ft head.

I 1 I loo 200 300 400 500

REVOLUTIONS PER MINUTE

Figure 11. Efficiency curves for Banki turbine under 160ft head.

4. Speed. According to the power-speed, Figure 10, and efficiency-speed, Figure 11, curves, the speed for maximum power for all gate openings from one-eighth to full under 16-foot head was practically constant. The computed speed was 263 rpm and the actual speed determined by experiment was 270 rpm. The optimum speed for maximum power at the other heads is shown below.

Head in ft 9 10 12 14 16 18

Actual rpm 197 212 232 260 270 200

Computed 202 - ‘1’ - 233 253 287

.

22 E~~G~~EENIXG EXPERIMENT STATION BULLETIN 25

5. Efficiency-sped. The highest efficiency attained was 68 per cent at optimum speed of 270 rpm, Figure 11. The cfYicienc~ decreased with the decrease in gate opening. Maximum efficiency for one-eighth gate opening was SO per cent. The efficiency of the

-

tlftt-t- ii, \

n I lit-+

Figure 12. Characteristic curves for Banki turbine under 160ft head.

1. est nozzle. .-I laboratory test nozzle \vas built ;jnd in+.t;llltxl as; shobcn in I-igure 13. This nozzle was so arranged that the width of the jet remained cC+nstant. This had the same effect as rcciucing the effective length of the turbine runner as the demand for po\f*er became less. This necessitated the use of a pinion gear to actuate the mechanism to reduce or increase the width of the jet, and this of necessit!. re(luced the speed \vith which such action could ta!;e place.

re 13. Banki water turbine built in Oregon State College Hydraulics Laboratory.

. .

24 EE;CIKEERIXGG ESPERIMEKT STATION BVLLETIN 25

2. German nozzles. instead of increasing or reducing thy Mitlth of the jet for change in power requiremc*nts, the thickness of the jet c(dd \JC changed. This method has bwn used with (krnxill patents, a~ shi ..II in Figures 14 and IS. In I-igure 13, a lever is attached to the gate A and actuated by the turbine governor. At C the water is forced to enter the turbine blades at the required angle for best operating efficiency, regardless of the flow of water. II1

Figure IS, the thickness of the jet may be changed by a slightly different patented device. The effect is the same as before.

Figure 14. German design of Banki turbine and nozzle.

-

I

I I

I

Figure 15. Alternate German derign of Eanki turbine and nozzle.

25

VI. INSTALLATIONS

2. American installations. ?%ny B;mki turl)iw3 ha\.e been inctalled in Oregon since the laborator>* tests5 described in this bulletin vvere made. At. least two different rnanufac’iurers have been building these water turbines, and many have been made in local shops.

The Installation is simple, as shovvn in Figures 16, 17, and in 1:igure 1. A small wooden dam may be built acrobs a small stream. the \I-ater diverted into a wooden flume where a head of 10 to LO feet ma? be obtained. Near the end of the flume a \.ertical box. or penr;tock, ma! be constructed so that the turbine nozzle may be bolted to it. 11’hen the turbine is not in use, the water simply discharges over the end of the flume as shown. A small shed houses the electric generator and any necessary belting or other miscellaneous equipment.

Figure 16. 3anki turbine runner and nozzle.

Figure 17. Inside of powerhoult, ahowing jackshaft and generator driven by Banki turbine.

VII. CONCLUSIONS

The test on the laboratory Banki turbine indicates that : I. This turbine can be operated efficiently on a wider range of open-

ings than most turbines. 2. Brake-horsepower varies almost directly with the three-halves

power of the head. 3. Maximum efficiency occurs at practically a constant speed for all

gate? openings at constant head. 4. The Banki turbine characteristic speed occupies a position between

those for the tangential and reaction turbines. 5. The effective width of the &heel can be changed at will without

changing the angle of attack, ( a1 ) .

It is felt that considerably more efficiency could be obtained b> experimenting with different numbers of blades and different nozzles. An efficiency of 68 per cent is not extraordinary and one should not expect to have attained the maximum efficiency with one test, especially on a turbine of such small horsepower. Losses of water to the turbine were known ; it is estimated that some 8 per cent of the total water never touched the wheel. Slight changes in design would reduce this loss considerably and thereby increase its efficiency.

It is obvious that there is a distinct place for the Banki turbine in the small turbine field. The advantages are simplicity and economy of construction.

OREGON STATE COLLEGE

ENGINEERING EXPERIMENT STATION CORVALLIS, OREGON

LIST OF PUBLICATIONS Bulletins-

So. 1. Prehmmary Report on the Control of Stream Pollution In Oregon, by c‘. \‘. Langtou and H. S. Rogers. 1929. Fifteen rents.

so. 2. A Sanitary Surve * of the Willamettr Valley, by H. S Rogers, C. A. hl~h more, and C. iI. Adams. 1930. Forty ceuts.

So. 3. The Properties of Cement-Sawdust Mortars, Plam, and with Varloos .4r’mlr tures. by S. H. Graf and R. H. Johnson. 1930. Twenty cents.

Y l o. 4. Interpretation of Exhaust Gas Analyses, by S. H. Craf, C. IV. Glceson. and IV. H. Paul. 1934. Twenty-five cents.

so. 5. Boiler-N’atcr Troubles and Treatments with Spec:al Reference to Problems in \Vestem Oregon, by R. E. Summers. 1935. Sane available.

‘* 6 A sr?%%a by C!. \V. Glceson. Survt of the \\‘illa;b;tF River from Sellwood Bridge 10 111~

Twmty-ive cents. .

$0. :. Inductrlal and Domestic N’astes of the Willomcttc Valley. by C. IV. GIrtson and F. Merryfield. 1936. F&y cents.

so. 8. An Investigation of Some Oregon Sands with a Stntlstical Study of the Prr- dlctive Values of Tests, by C. E. Thomas and S. H. Graf. lQ3;. Fifty cents.

So. 9. Pre*rvative Treatments of Fence PGStS. 1938 Progress Report on the Post Farm, by T. J. Starker. 193s. Twenty-five cents. Searly progress reports, 9-A. Q-B, Q-C, Q-D, 9-E. 9-F. 9-G. Flfteen cena each.

so. 10.

so. 11.

so. 12.

so. 13.

so. 14.

So. 15.

So. 16.

So. 17.

So. 18.

Precl I!

Itation-Static Radio Interference Phenomena Originating on AIrcraft. by C. Starr. 1939.

.%vcnty-five cents. Electric Fence Controllers with Special Reference to Equipme~~3QDeveloped

for Measuring Their Characteristics, by F. A. Everest. . Forty cents.

Mathematics of Alignment Chart Construction without the Use of Deter- minants, by J. R. Griffith. 1940. Twenty-five cents.

Oil Tar Creosote for Wood Preservation, by Glenn Voorhies, 1940. Twenty-five cents.

Optimum Power and Econom ;c-

Air-Fuel Ratios for Liquefied Petroleum Cases. by IV. H. Paul and M. - . Popovich. 1941. Twenty-five cents.

Rating and Care of Domestic Sawdust Burners, by E. C. Willey. 1941. Twenty-five cents.

The lmprovemmt of Reversible Dry Kiln Fans, by A. D. Hughes. 1941. Twenty-five cents.

An Invent0 of Sawmill Waste ia Oregon, by Glmn Voorhies. 1942. Twenty- vc cents. a

The Use o:gqFqWtier Series in the Solution of Beam Problems, by B. F. Ruff- ner. Fifty cent;.

Xa 19. 1945 Progress Report on Pollution of Oregon Streams, by Fred Merryfield and !V. C. Wilmot. 1945. Forty cents.

So. 20. The Fishes of the Willamette River System in Relation to Pollutmn. by R. E. Dlmick and Fred Merryfield. 1945. Forty cents.

No. 21. The L?se of the Fourier Series on the Solution of Beam-Column Problems. b B. F. Ruffner. 1945. ?) wenty-five cents.

THE BANKI WATER TURBIN! 29 -

No. 22. Induetrial and City Wantea. by Fred Merryfield, W. B. Bollen, and F. Z. Kacklhoifer. 1947. Forty cents.

No. 23. Ten-Year Mortar Strength Test, of Some Orcgan Sands, by C. E. Thomas and S. H, Graf. 194% Twmtr4re cents.

No. 24. Space H&ingt hy Electric Radiant Panels and by Reverse Cycle, Iiy I&ins Sled. July I948. Fitiy c&w.-

No. 25. The ,%X Water Turbine, by C. A. Mockmore and Fred Merryfield. February

Forty cents.

Cirqdare- No. 1. A Discussion of the Properties and Economics of Fuels Used in Oregon. by

C. E. Thomas and G. D. Krerins. 1929.

No. 2.

No. 3.

Nc. 4.

No. 5.

No. 6.

No. 7.

No. 8.

No. 9.

No. 10.

No. 11.

Twenty-five cents. Adjus;eas&.of A;;miotivc Carburetors for Economy, by S. H. Graf and G. W.

None available. Elernly3t;. of Refrigeration for Small Commercial Plants, by W. H. Nartin.

None available. Some Engineering Aspects of Locker and Home Cold-Storage Plants, by W. H.

Martin. 1938. Twenty cents.

Rcfr;E;tion Applications to Certain Oregon Industries, by W. H. Martin.

Tw&ty-five cents. The U= of a Technical Library, by \V. E. Jorgensen. 1942.

Twenty-five cents. Saving Fuel in Oregon Homer, by E. C. Willcy. 1942.

Twenty-five cents. Tcchni4nf Approach to the Utilization of Wartime Motor Fuels, by IV. H. Paul.

Twenty-five cents. Electric and Other Types of House Heating Systems, by Louis Siegel. 1946.

Twenty-five cents. Economics of Personal Airplane Operation, by W. J. Skinner. 1947.

Twenty-five cents. Digest of Otepon LPnd Surve i&anws,

B. B. Irving, and E. A. If by C. A. Mockmore, N. P. Coopey’.

. 1940. Twenty-five cents.

Rtprint 2- No. 1. Metbodr of Live Line Insulator Testin and Results of Tests with Different

Instruments, by F. 0. McMillan. I cprinted from 1927 Proc. N. W. Elcc. 1.t. and Power Assa. Twenty cents.

No. 2. Sony Anomalies of Siliceous Matter in Boiler Water Chemistry. by R: E. Summers. Reprinted from Jan. 1935, Combustion. Ten cents.

No. 3. Asphalt Emulsion Treatmcnt Prevents Radio Interference, by F. 0. McMillan. Reprinted from Jan. 1935, Electrical West. None available.

No. 4. Some Characteristics of A-C Conductor Corona, by F. 0. McMillan. Reprinted from Mar. 1935, Electrical Engineering. None available.

No. 5. A Radio lnttrfercnce Neasuring Instrument, by F. 0. McMillan and H. G. Barnett. Reprinted from Aug. 1935, Electrical Engineering. Ten cents.

No. 6. Water-Gas Reaction Ap rent1 Controls Engine Exhaust Gas Composition. by G. W. Glreson an80W.. k. Paul. Petroleum News.

Reprinted from Feb. 1936, Natronal

Ten cents. No. 7. Steam Generation by Burnin

April 1936. Heating and 6 Wood, by R. E. Summers. Reprinted frcm

Ten cents. cntilothg.

No. 8. The Piczo Electric Engine Indicator, bv W. H. Paul and K. R. Eldredge. Reprinted from Nov. 1935. Oregon State Technical Record. Ten cents.

teem in asia ore and fred erryfield y: 7331 usa ! ies are...

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