Air lift. Diseño. ubc_2004-0178[1].pdf

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A I R A C T U A T E D PUMPING T E C H N O L O G Y INURBA N DRA INAGE

b y

D . A a r o n Bohnen

B . A S c , Th e Univers i ty o f B r i t i s h C o l u m b i a , 1996

A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T O FT H E R E Q U I R E M E N T S F O R T H ED E G R E E O F

M A S T E R O F A P P L I E D S C I E N C E

i n' T H EF A C U L T YOF G R A D U A T E S T U D I E S

C I V I L E N G I N E E R I N G

W e accept this thesis as conforming

to the required standard

T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A

A p r i l 2004

D .A a r o n Bohnen , 2004


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Library Authorization

In presenting this thesis in partial fulfillment of the requirements for an advanceddegree at the University of British Columbia, I agreethatthe Library shall make itfreely available for reference and study. I further agree thatpermission forextensive copying of this thesis for scholarly purposes may be granted by thehead of my department or by his or her representatives. It is understoodthatcopyingor publication of this thesis for financial gain shall not be allowed withoutmywrittenpermission.

Name of Author (please print Date ~(dd/mm/yyyy)

Title ofT h e s i s : 4'/g^/}fU/tT h PUH4PAJ6r TS^ /rJiFLO fry

Degree: Year:

Department of CWlL- KT K I S . ^ :fZ ?r4 ^The University of British ColumbiaVancouver, BC Canada


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A B S T R A C TA i r l i f t Pump technology is briefly sum mar ized and the potential application of a i r l i f ttechnology to l o w - l i f t , low-submergence, high-flow applications such as open channelf l o w in urban storm drainage, is explored. Fou r experimenta l setups are described,i nc lud ing one proto type urban sto rm drainage in stal lat ion . Three descri ptiv e mo del s for

a i r l i f t pu mp operati on are devel oped and one adopted for appli cati on in l o w - l i f t , l o w -

submergence, high-flow applica tio ns. The mo del all ows a sim ple design procedur e fora i r l i f t pum ps in this regi me. A si mpl e design hand-calcul ati ons procedure is develo ped,and two perso nal compute r-ba sed i mplem ent ati ons are describ ed. A si mpl e design

example ispresented and recom menda tio ns for further research and deve lo pmen t

direct ion s are made .


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T A B L E O F C O N T E N T SAbstract i i

Table o f Contents i i i

L i s t o f Figu res v

L i s t o f Tables v i

Acknowledgements v i i

C H A P T E R 1 Ov er vi ew & Sum ma ry

1.1 Int ro duct ion to A i r l i f t Pum ps 1

1.2 Des cri pti on o f an A i r l i f t Pu mp 61.3 Appl ica ti on s o f A i r l i f t Pum ps 9

1.4 Proj ect Sco pe and Rat io na le 11

1.5 Two-Phase F l o w Reg im es 141.6 Operational E f f i c i e n c y o f A i r l i f t Pu mp s 171.7 Su mm ar y 20

C H A P T E R 2 Literature Rev ie w

2.1 Int rod uct ion 22

2.2 Devel opme nt of A i r l i f t Pump Theory, 1797 to Present 22

2.3 Su mm ar y 30

C H A P T E R 3 Experim ent al Prog ram

3.1 Ove rv ie w o f the Experim ent al Prog ram 32

3.2 The Experim enta l Setups 36

3.2 Resul ts o f the Exper im ent al Pro gra m 56

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T A B L E OF CONTE NTS(cont'd)

C H A P T E R 4 Three A i r l i f t Pump Theoretical Models

4.1 A i r l i f t Pump M o d e l fo r F i x e d Bub ble Velo citi es 57

4.2 A i r l i f t Pump M o d e l for Variable Bubble S l i p Velo citi es 654.3 A i r l i f t Pump M o d e l for Turbulent M i x i n g 724.4 Sum mar izi ng the Three Mo de ls 79

C H A P T E R 5 Prel imi nar y Desi gn of A i r l i f t Pumps

5.1 Preli min ary Desi gn Procedure Cal cula tio ns 81

5.2 Des ig n Cal cula tio ns for Personal Com pute r 86

5.3 Pract ical Consi deratio ns for Prel imi na ry A i r l i f t Pu mp Desi gn. 91

C H A P T E R 6 Con clu si ons and Research Recomme ndat ion s

6.1 Con clu si ons 94

6.2 Resea rch Reco mme nda ti on s 95

R E F E R E N C E S 96

A P P E N D L X 1 99


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L I STO F I G U R E S

Figu re 1 - Schema tic A i r l i f t Pump Layou t and Termi nol ogy 7 (also 57)

Figure 2 - Two-Phase Ai r- Wat er F l o w Regi me s 15

Figure 3 - Two-Phase F l o w Regime s characterized by Gas F l u x and Mi xt ur e 16V o i d Fraction

Figure 4 - First Laboratory A i r l i f t Pu mpi ng Syst em 37

Figure 5 - First Laboratory A i r l i f t Pum pin g Sys tem Results 38

Figu re 6 - Prot otype Scale Labor ator y A i r l i f t Pum pi ng Sys tem 39

Figure 7 - Gilbert Road Prototype A i r l i f t Sys tem Lay ou t 42

Figu re 8 - G il ber t Ro ad Prototy pe A i r l i f t Sys tem Compo nent s 43

Figu re 9 - Gil ber t Roa d Com press ed A i r Suppl y Subsys tem 45

Figu re 10 - Gil ber t Roa d Prototype A i r l i f t Sys te m in Operat ion 46

Figu re 11 - Slo t-con figur ed A i r l i f t Pu mp Syst em in Operation 51

Figure 12 - R ic hm on d Publ ic Wor ks Experimental Setup 54

Figu re 13 - B ub bl e Ris e Vel oci ti es in S t i l l Wa te r 61

Figu re 14 - M ix tu re and Gas F l u x Rates 65

Figu re 15 - Co mpa ri so n of Experi ment al and Cal cula ted Performan ce 78

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L I S T O F F I G U R E S (cont'd)

Figu re 16 - Si mp le Des ig n Exa mp le Lay ou t 82

Fig ur e 17 - A i r l i f t Pump Churn F l o w Work shee t 87

Figure 18 - V B ACo de for Chu rn F l o w A i r l i f t Pu mp Desi gn 89

Figure 19 - V B ACod e for Chu rn F l o w A i r l i f t Pu mp Des ign 90

L I S T O F T A B L E S

Tab le 1 - A i r l i f t Pu mp Nomenclatu re and Vari able s 8

Tabl e 2 - Prot otype Sca le Labor ato ry A i r l i f t Pum pin g Syst em Results 40

Table 3 - Gilb ert Roa d Prototype A i r l i f t System Sample Experimen tal Data 48

Tabl e 4 - G il be rt Ro ad Prototype A i r l i f t Syst em Sample Experime nta l 48

Results

Tabl e 5 - Gil ber t Ro ad Prototype A i r l i f t System Leakage Tests 49

Tabl e 6 - Gi lb er t Ro ad Protot ype A i r l i f t System Sample Experime nta l 50

Results 2

Table 7 - Ri ch mo nd Pub li c Wo rk s Sample Experiment al Data 55

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A C K N O W L E D G E M E N T S

I w o u l d l i k e to gratefully ackno wledge m y research supervisor, Den is S. O. Russel l ,Professor Emeri t us o f the Un ive rsi ty of B r i t i s h C olu mb ia Depar tmen t o f C i v i l

Engineer ing, for his cont inu ous su pport throughou t this project. Than ks also to Profes sor

J i m At wate r and Professor A l a n Russel l , also of the Uni ver si t y of B r i t i s h C o l u m b i aDepartment o f C i v i l Engineer in g. Theirassistance and encouragement was particu lar ly

val uab le. Tha nks also to the Eng in eer in g Depart men t at the C i t y o f R i chm o n d , and M r .

Arthur Louie whos e interest in the appl ica tio n o f a i r l i f t pumps to urba n drainage made

this study possible. F i n a l l y , thanks also to the National Science and Research C o u n c i l o fCanada for their contribution during the earlyphases of this project .


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C H A P T E R 1

1.1 - I n t ro duc t io n to A i r l i f t P um ps

A i r l i f t pumps are comm on ly considered to be part o f a uni que class o f altern ate

pu m pi n g technologies. These alternate pum pin g technologies are required when co mm o n

rot odyn ami c pumps are unsuitable for a given project or applicatio n. So me applications

that comm on ly benefit from alternate pumping technologies involvef l u i d / s o l i d mixtures,very viscous fluids, hazardous fluids, l i v e organisms suspended in fluids, low-head or

low-submergence situations, scenarios with va ria ble inlet water surface l evel s, etc. A i r l i f tand other alternate pumping technologies provide a means for engineer s to appro ach

these scenarios.

Des pit e the success o f the a i r l i f t pump in several other areas, the a i r l i f t pump has notgai ned acceptance in c i v i l engineering applications. Specifically it has not been use d for

man ageme nt of sto rm waters, pu mp in g flui ds in open channels, no r in any other hig h

discharge, low l i f t , low head applications despite the fact that in some cases it may

promise some advantages inthese settings. In fact, an extensive literature search on a i r l i f tpu mp research an d devel opme nt fo un d no references at al l to a i r l i f t pum ps used in high -discharge, low-head, l o w - l i f t capacities in c i v i l engineering applications or otherwise.

Nevertheless, there are potential applications for low head, high capacity pumping ofwater in open channel s, and specifically o f sto rm ru no ff in draina ge condu its . Thi s

research progra m is focused on investigatin g thosepossibil i t ies .

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The main feature of an a i r l i f t pump is avertical tube with the lowe r end subm erge d inwater a nd a suppl y of compr essed air pro vi ded to the l owe r end. A s the compr esse d air

f lows into the lowe r end o f this tube bubbles are formed and a mixture of water and air

bub bles results. Sin ce this mixtu re of air and water is less dense and thus lighter than

water, the level of the air and water mixture in the vertical tube rises above that o f the

surrounding water surface. W i t h a suitable physical arrangement, this results incont inuous l i f t i n g of the water to a higher level than the original wat er surface - i n

effect creating an a i r l i f t pump .

C a r l Loescher , a Germ anm i n i n g engineer, reportedly developed the original a i r l i f t pumpcon cept in 1797 an d the tec hno lo gy began to gai n wide spr ead acceptance i n the mi dd le

1800's (Ward 1924). B y the ear ly 1900's sever al patents had been issued for various

arrangements of a i r l i f t pumps and they were widely used for pumping water, often fromquite deep wells, unti l being superceded by reliableelectrically-driven submersible

ro todynamic pu mps. There was a consi derabl e amou nt o f early research into the a i r l i f tconcept, but broad interest on the topic waned as a i r l i f t pumps were superceded in the

ear ly 1900's. Despit e hav in g been replaced in co mm o n use, a i r l i f t pumps have continuedto be used in several speci al ized applicati ons,which are described in more detail later in

this chapter.

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The city o f R i chm o n d in B r i t i s h C o l u m b i a , C an ad a is situat ed in the mo ut h o f the Fra ser

River and experiences an average 1 1 0 0 m m ofrainfall per year1 . The average eleva tio n ofthe city is approximate ly one metre above mean sea l e v e l . Because of this very lowelevat ion, much of the city would be submerged under tidal or river water duri ng var iou s

parts o f the year were it not for the exten sive sys tem o f levees prot ecti ng Ric hm on d from

the Fraser River and the ocean waters ofGeorgia Strait. Recent ini tiat ives to further

i m pr o v e the city 's protection from r iver and sea flood waters have been to plan for the

insta l la t ion of a so-calledmid-island di ke to help prevent Fra ser River waters from

inundating centralR i c h m o n d in the event o f a leve e br each in the East ern re gio n o f themunicipal i ty.

The average ground slope inR i chm o n d is zero and thus the munic ipa l stormwater

man agemen t syst em is constra ined to very l ow slopes in its ' ma in conduits. The pr ob le m

o f l o w slope s is co mp ou nd ed by the necessary l eve e syst em used to protect the city. The

levees create a need to pum p stormwater out o fR i chm o n d when tides are unfavorable,

part icular ly in the winter when the tides are relativelyhigh and constant. The sto rmwate r

management system inR i chm o n d relies on low tides to a l low the outfall flapgates to

open. In the wint er mo nt hs the tides tend to be high and constant, with th e dai ly second

l o w tide s t i l l very high. This is unfortunate t iming sin ce the win ter mo nth s are often ver y

ra iny in the Lower Main l and . Thes e factors result in a real and ong oi ng dange r o f win ter

f looding in the city o f Richmond.

1 Ci t yofRichmondEngineeringstaffgraciouslyprovided the background information on their stormwaterdrainage system as presented in thisbriefsection during various sitevisits, meetings and conversationsthattook placefrom 1997 to 1999 throughout the development of this research project.

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Du r i n g hea vy rains, pum pin g stations at the perimet er outfa lls of the syst em can p u l l thel o c a l water levels down to shutoff but there ca n s t i l l be f looding in central Ri chm on dbecause of the inabi l i ty to move storm water quickly enough to the outfalls. Recent

experience has shown that Ric hm on d experiences unacceptable storm water levels a nd

f looding in some areas as frequently as once every two or three years.

Because of these concern s and incr easi ng high-den sity developme nt i n the ur ba ni zed core

o f R i chm o n d , the city has been consi deri ng option s for im pr ov in g the capaci ty of their

stor mwater ma nage ment system. Con cent rat io n times are short so either faster re mo va l ofrunoff or detention and storage is required. Detention and storage is problematic given

the high water table i n Ri ch m o n d, so the approach has been to con side r options focus ed

on increasing the rate of runoff removal.

The first opt io n presented was to int roduce more and larger condui ts. Unfor tu na tel y this

strategy w o u l d be extremely expensive and very proble matic in pub li c inco nven ience

since man y of the ma in stormwat er condu its are ins tal led in bui lt-u p areas and under

main city roads. Addi t iona l ly , in stal lat ion of large concrete bo x culver ts has beco me ver y

unattractive since B r i t i s h C o l u m b i a work er' s protection legisla tion conce rni ng the

condit ions requ ire d for their main tena nce is so strict that it ma kes the upke ep o f su ch

conduits impra ctica l and very expensive.

The second alternative was to investigate means of increasing the effective slope of the

system by increasing the water surface grade within the conduits by pumping. This

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second approach w o u l d accelerate the mean flow velocit ies and thus remo ve s to rmwaterfrom the city core at an increased rate.

A n eed for high capacity, low head pumps that could be ins tal led i n sto rm drainage

conduits to l i f t s to rm water between 1 and three feet (0.3 to 1.0 m) had developed. Such

pumps w o u l d in crease the effective slope and hence the discharge capac ity of the exi st in g

storm drainage infrastructure. These pumps would only be required for short durations

under the comb ina tio n of heavy rainfalls and high tides.

C o m m o n ro to dyn am ic pumps do not con for m to this high-flow, low-head requirement

a n d i f pum p units could be found to satisfy these requirements they w o u l d s t i l l be

expensive to instal l and house in the R i chm o n d system. This isbecause of their need for

m i n i m u m subme rgence l evels at their inlets, necessitatin g substantial excavat io n and

placem ent o f infrastructure i n an area with sandy soils and a high watertable.

T h e difficulties and impracticalities i n both of the propos ed solut ionstrategies have

effectively st opped Ri ch mo nd 's progress towards an im pro ve d storm water man agemen t

system. Despi te the impasse howev er, the danger o f flooding in central R i c h m o n d is real

a n d incr easi ng as urba n devel opmen t contin ues.

Real iz ing the need for a way forwa rd, ah alternative pump in g techn olo gy was sought and

this requirement spurred R i chm o n d into sponsor ing the applied research prog ram that is

described in this thesis.

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1.2 -Descriptionof an Airlift PumpA n a i r l i f t pum p itself is compr ised of five ma jor compone nts, na mel y the air suppl yapparatus, the air in ject io n or aeration s yste m, the water inta ke, the riser pipe and the

pu mp outlet. Figu re 1 shows the ma in elements o f an a i r l i f t pump. Nomencl atu re used inthat figur e and other vari ab les of interest are defin ed in Tab le 1.

A n a i r l i f t pu mp ma y also feature a so -ca ll ed foot piece , a len gthen ed sectio n o f the

main riser pipe located below the aeration point and in which only single-phase water

flows. A foot piece al lo ws an a i r l i f t pump to entrain water from a depth greate r than it s'aeration depth. This a ll ows a means for pum p units with lo w head air-su pplyapparatus to

successfully pum p l i q u i d from m u ch deeper leve ls than they w o u l d othe rwise be capab leof. Si nc e foot pieces are requi red on ly in scenarios in which the water to be pumped is to

rise f rom a great depth not all a i r l i f t pumps feature foot pieces. In fact, most short a i r l i f tpu mp s su ch as thos e in this study, do not use foot piece s.

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F I G U R E 1 - Sch em at ic A i r l i f t P u m p L a y o u t


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T A B L E 1 - A i r l i f t P u m p No m e n c l a t u r e a n d V a r i a b l e s

Area = cro ss-sect iona l area of airlift pump tubeb = tuni ng parameter in a ir phase vel oci ty /mixtu re veloci ty rela t ionshipA a i r = area off low mix tu re cross section occupi ed by airA w = area of f low mix tu re cross section occupi ed by waterc = tuni ng parameter i n a ir phase ve loci t y/mi xture veloci ty rela t ionshipd = t uni ng parameter in head loss equationDiam = diameter of airlift pump tubeDens = relati ve densit y of the air-water mixtu re in the airlift pump tubee = tun ing parameter in head loss equationg = acceleration due to gravityHdrive = dr iv ing hea d appli ed to airlift pumpHlift = l i f t height of air-water mixture in airlift pump tubeHioss = head loss in airlift pump tubeHtota = hei ght o f pum p l i f t above aeration pointHfoot = height of pum p tube footpiece be lo w aeration poin tH s u b = height of stan ding water surface above aeration poi ntKent = pump tube entrance loss factorKexit = pump tube exit loss factorKpipe = pump tube pipe loss factorKtotal = tot al pu mp loss factorQair = v o l u m e f low rate of air in airlift pump tubeQmix = v o l u m e f low rate of the air-water mixture in airlift pump tubeQwater = v o l u m e f low rate of water in the airlift pump tubeV a i r = veloci ty of the air fraction in the air-water mixture in airlift pum p tubeV

v mix = veloci ty of the air-water mixture in airlift pump tubeV r e l = rela t ive veloci ty o f the air phas e to the water phas e i n the airlift pum p tubeVwater = veloci ty o f the water fraction in the air-water mix tur e in airlift pump tubeTlsystem = airlift pump system efficiencyTlairdelivery = airlift pum p air del iver y subsystem efficiencyTlriser = airlift pu mp riser tube subsys tem efficiencyPair = den sit y o f gas pha sePwater = densi ty of l i q u i d phase

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A s ment ion ed previo usl y, in this study onl y a i r l i f t pumps with zero- leng th footpieces are

considered, so H f0 0 t = 0 and the total length of the pump riser tube is equal to the sum of

the sub mer ged and un sub mer ged lengths, H S U b and Hi j ft .

1.3 -Applicationsof AirliftPumpsDespite hav in g been superceded by submersi ble roto dynam ic pumps i n most co mm on

applicat ions, a i r l i f t pumps are s t i l l used in several speci al ize d settings. T y p i c a l modernapplications of existing a i r l i f t pu mp technolo gy inclu de use of these pumps i n deep water

wells , where a related system kno wn as a geyser pum p is also bec om in g incr easi nglyc o m m o n where small-diameter pump tubes are feasible. A i r l i f t pumps also s t i l l

frequently serve deep shaft and w e l l d r i l l i n g applications.

A i r l i f t pu mps are also used in mode rn windmil l -driven pneumat ically-o perated water-

w e l l pumping applications, such as those available as turnkey systems from A i r l i f tTechno logies of Redlands, C A .

Despite the fact that min in g technol ogy has developed dramat ically , a i r l i f t pumps are s t i l la staple in mi ne dewaterin g, and moder n examples are remarkab ly s imi l a r to the original

system developed by Loescher in 1797. A i r l i f t pumps are also often used in process

applications inwhich cor ro siv e or vis cous liqu ids such as sand-water slur ries, salt

solut ion, oi ls and var iou s other waste products make tradi tio nal ro to dyn am ic pum ps less

suitable. (Giot, 1982) The o i l indus try uses a i r l i f t pum ps in ret rie vin g crude oi l fr om deadwells . The nuclear industry uses carefully calibrated small diameter a i r l i f t units to pumpfluids i n nuclear fuel retreatment (Clark & Dabolt 1986).

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Wastewater treatment plants are curren tly the most co mm on appli cati on for a i r l i f t pumps,

where excellent aeration and subsequent o xygenati on of the pumped mixtu rethat is

derived from the injected air is a strong benefit. The Sanitai re com pan y ofB r o w n Deer,

W I bu il ds stainless steel a i r l i f t pumps for this applica tio n.

A i r l i f t pum ps are often used in aquacu ltu re and f i s h fa rmi ng operation s where their lacko f m o v i n g parts provi des necessa ry safety for f i s h and the air in tr odu ced in to the waterc o l u m n improves oxygenation (Wurts , M c N e i l l & Overhu lts , 1994). The Aqu aca re

company o fBe l l i n gha m , W A manufactures a i r l i f t pumps for f i s h farm ing applications.T h e compe tin g technologies used in f i s h fa rmi ng, na mel y geyser pum ps and prope lle rpum ps, have the respective disadvantages of nois e and possi ble damage to f i s h safety inaquaculture applications.

Offshore miner a l excavat ion and d iamo ndm i n i n g is an emerging applicat ion for a i r l i f tpumps, where the lack o fm o v i n g parts and abil i ty to handle particulates make them

part icular ly suitable. A i r l i f t p um ps are also somet ime s use d in as imi l a r manner for

underwat er re cover y and salvage operations, where an a i r l i f t tube may be rigged andpowered from the surface, a l lowing divers to place smal l i tems at the intake o f the p um p

a n d have the items carr ie d to the surface. A i r l i f t p um ps for use in deepwater sal vage o ften

feature tapered riser pipes, presumably so that as air bu bb les incr ease in size du ri ng theirrise from the aeratio n poin t towar ds the surface the v o i d ra tio o f the mixt ur e in the pu mp

tube does not increase too much and reduce efficiency. Th e a i r l i f t pu mp is ver y w e l lsuit ed to un derwat er re cov ery purposes s ince com pres sed air is a staple aboa rd sa lva ge

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vessels and the turbulent nature of the f l o w in the a i r l i f t pump tube as w e l l as theupwards-opening shape of the commonly-used a i r l i f t pum p barrels in this appl ica tio n aredoubtless helpfu l in av oidi ng any potential ja mm in g irregul arly shaped items ma y

experie nce i n the pu mp risers.

The f i n a l co mm on applicat ion of a i r l i f t pum ps is in lake turnover, where these pu mp s areus ed to cou nte r the effects o f lak e str ati fica tio n (Park er & Sutt le 1987). In lake

destratification applications a i r l i f t pum ps often float on sm al l buo ys wi th their outlets at

the water surface an d compr ess ed a ir deli ver ed by floati ng supp ly line s (Wur ts, M c N e i l l& Overhults 1994).

1.4 - Pro ject Scope and Rat io na leThis research project aim s to investiga te the sui tab ili ty and beha vio ur of a i r l i f t pumps in anew class o f applica tion s - na mel y l o w - l i f t , high- flo w, low-sub mergence scenarios su chas pu mp in g in open channels and management of urban s torm drainage. Des pit e the

unorthodox concept, a i r l i f t pumps promise many advantages in such applications.Insta l led costs are lo w since the pumps are simpl e, compo sed pri ma ri ly of com mo nl y

avail able P V C or steel pipe fittings. A i r l i f t pumps are very robust and nearly

maint enance-free since they have no underwater m ov in gparts (de Cachard & Delhaye

1996). Addi t iona l ly , their air sup ply systems can be locat ed con ven ien tl y abo ve gro un d to

m i n i m i z e insta l la t ion costs and facilitate ins pectio n and main tenan ce.

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Thefollowing discussion ofairliftpumpefficiency suggeststhat the low-head, low-submergence, high-flow, necessarily large diameter airlift pumps that would berequiredinopen-channelandurbanstorm drainage applications would be energy inefficient units.Despite this inefficiency, the authorbelievesthat airlift pumps may offer enough othercostandservice advantages tooffsetthe operational inefficiency of the airlift pumps thatwould be applied inthesesettings.

Some of the advantages airlift pumps may offer tourbandrainage applications include

low installationcostandmaintenancecost,very low supporting infrastructurecost,and apossibly huge placement benefit in the potential option for portablepumpunits and/orportable power units, thus potentially eliminating entirely the need for apumphouseorsimilarinfrastructure.

Theaeration of storm runoff mayalsobe a reason to consider the application of airliftpumps tourbandrainage applications.Urbanstorm runoff often contain highlevelsofheavy metals, petrocarbons, chemicals from spills,andother roadwash pollutants andtend to create potentially significant environmental impacts to the bodies of water intowhich they discharge.(Turer,Maynard&Sansalone, 1996).Airliftpumps are usedroutinely in aquacultureandwastewatertreatmentbecauseof their significant benefit inaerating thepumpedliquid.Using airlift pumps forurbandrainage could provide theadditionalbenefit of aerating the storm runoff, therebymimickingthe aeration processused in manymunicipalmixed-sewagetreatment plants, potentially accelerating

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oxidat ion o f the roadwash and other stormwater polluta nts, and a l lowing for a decrease in

resul t ing environmental impacts .

This compel l ing array o f advantages, par ticu lar ly the very lo w cost of instal lat ion and

maintenance of a i r l i f t pumps, the lack o f a need for perman ently i nsta lled powe r andcontrol systems with theirattendant housing infrastructure, and the potential benefit of

aerating the runoff waters make the investi gati on of a i r l i f t pumps fortheseapplicatio nsvery attractive.

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1.5 -Two-PhaseFlow RegimesA i r l i f t pumps are two-phase f l u i d f l o w devices. Gas and l i q u i d (in most cases air andwater) f l o w upwards together in a vertical pipe. This two-phase f l u i d mixt ur e can takeseveral different forms, and the various f l o w patterns of the two phases i n these formshave si gnifi cant ly differin g hydrau lic behaviou rs. Thi s is significant to the science and

design of a i r l i f t pumping systems since any ofthese forms o f air-water mi xtur es arepossible , an d the for m fou nd in the system o f interest is a ver y impor tan t va ria ble since

physical relat ion ships and deri ved mat hema tica l relati onshi ps are un ique for each for m.

The exact descriptions of the f l o w patterns vary somewhat by author, terminology is notalways common, and some flows are described as combinations ofpatterns (Shelton &

Stewart, 2002).

A sum mar y of the five ba sic forms o bser ved in the two-phase f l o w o f water a nd air in

vertical pipes, along with their most common names are sho wn in Fig ur e 2. (mo dif ie d

from Tai tel , Bornea & Buckler , 1980). Figure 3 shows the same f l o w regimescharacterized by gas f l u x and mixtu re velo city.

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FI GUR E 2 - Two-PhaseAir-Water Flow Regimes

Bubbly Churn Slug Dispersed AnnularF l o w Froth Flow Annular F i l mF l o w Ripple FlowF l o w

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F I G U R E 3 - Two PhaseFlowRegimescharacterizedby Gas Fluxand Mixture VoidFraction,adaptedfrom Wallis(1969)

P E R F O R A T E D P L A T E S

3 0 U ox

NO. OF ORIFICES' DIAMETER(cm) SQUARE ARRAY SPACINGfcm^I

4 9100

2 8 9

4 . 0 6 X 104 . 0 6 X 101.52 X 10

0. 41 X 10

ll

6.25 X9. 50 X6. 25 X

101010

-II

-I

2 5

Eo

o

2 0

XID

COXo

XXX X XXX X

x xX X X *X X X x

XXXX

x AXXX XX XXX XXX

IDEAL BUBBLINGREGIME

0.1 0.2 0.3VOID FRACTION - oc

.4

UJZoucczoz


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1.6 - OperationalE f f i c i e n c y of A i r l i f t PumpsA i r l i f t pum p efficiency can be defined as the rat io of ene rgy del iv er ed to the pu mp uni t to

the unit energy o utput i n the form o f veloci ty an d head of the pu mp ed l i q u i d . The overal lsystem efficiency can be consi der ed a produ ct of the airdel ivery and a i r l i f t risersubsys tem efficiencies. Th eefficiency o f the air delivery subsystem depends on the type

and co nfig ura tio n of the air supply equipment, piping, conduits and controls. Efficient

delivery o f air through in sta lled conduits at desired pressures and f l o w rates is a w e l l -explored an d matur e bra nch of mech an ica l engin eerin g.

C o m m o n w i s do m i n the design and use of a i r l i f t pumps suggests the efficiency of ana i r l i f t pu mp riser subs ystem is maximized when deep subm ergence is avai lab le, the l i f theight is low, and l i q u i d and air f l o w rates are lo w. De Ca cha rd & Delh ay e (1995) andDe Ca cha rd (1989) also suggest a very strong contr ibu tin g effect in the length-to-

diameter ratio, namely that slender pumps with high length-to-diameter ratios are greatly

mo re efficient than their lo w length-to-diameter r atio counterparts.

The most efficient a i r l i f t pum ps feature a situ ati on inwhich the air and water phases have

very s imi l a r velocities, air bub ble s are either spher ical and very smal l or are large, dart-

shaped T a y l o r bubbles with a cross section near the entire pipe diameter. In both of these

m a x i m a l l y efficient cases, the slip veloci ty bet ween the air bub ble s and wate r is

minimized .

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A i r l i f t p u m p efficiency is further enhan ced by use o f the smalle st pos si bl e stable v o i dfraction - thus pum pi ng the m a xi m u m amou nt o f water per amount o f air injected.

Aerat ion eff iciency is also an importan t factor in deter min ing the efficiency of short

a i r l i f t pumps although itmatters less inl o n g pumps (Wal l is 1968). This phenomenon

appears to occu r becau se the long a i r l i f t pumps tend to operate i nslug f l o w . S lug f l o woccurs in pumps l o n g enough that smal l bubbles can accrete together to form

homogeneously spaced large Taylor bubbles close in cross section to the pipe diameter

(Taitel & al. 1980). In this f l o w regime the f l u i d flows conti nuo usly in contact with the

pipe wal l s cre at ing losse s direct ly dependent on the f l u i d velocity.

A t the entrance of l o n g pumps (and in shorter a i r l i f t pumps in which smal l bubbles do nothave the oppo rt un it y to accrete into Taylor bubbles before exi t ing the pump riser) the air

and water mixture f l o w is turbulent and recircu lato ry.Taitel & al (1980) characterize thisf l o w regime as froth or chur n f l o w and identify it b y the osci l la tory nature of thel iqu id ' s u pwar d and downwa rd mot ion between and around bubbles . A n aerator assemb ly

that diffuses many smal l even ly distrib uted bubb les into the f l o w f i e l d helps reduce thisturbulence and recirculat ion, redu cing losses and incre asin gefficiency. M o r r i s o n & al.

(1987) suggest that this is also true for the bubbly f l o w regime where mul tipor t injection

is more efficient .

Despite ear ly and contr adicto ry observa tions such as those by W a r d (1924) and Bauer &

Pol l a rd (1945) on large diameter a i r l i f t pump systems, riser diameter also plays a role in

a i r l i f t pum p efficiency for a given l i f t height since larger diameter a i r l i f t pumps tend to be

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less efficient than their smal ler counterparts. Thi s isbecause the larger diameter pum ps

must b e very lon g before the efficient Taylor bubble-induced s lug f l o w regime can

stabi l ize (De Cachard & Delhaye 1995). In fact, as the pipe diameter increases the cross

sect ional area increases even more rapidly,thus dimi nis hing the abi l i ty of surface tens ion

forces to ho ld large bubbles intact against the influence of a complex turbulent shear f i e l d

i n the air/water mixt ur e co lu mn . De Cacha rd & Del ha ye (1995) also suggest that surface

tens ion forces in bub ble s reduce slip vel ocit ies between the air water phases. In that case

since bu bb le surface tensi on forces are increased in sm al l diameter pi pes, the redu ced

efficiency of large diameter pu mps m ay be due to greater slip velocit ies, themselves dueto the re duce d rel ati ve effect of surface te nsi on forces.

Observa t ion suggests that as the pipe diameter i ncreases ab ove a m a xi m u m feasible

bu bb le diamet er the thickness of the f i l m in the annular region surro undin g the Taylor

bubbl es i n the slug f l o w mixtu re may begin to thicken rapidly. Thi s rapi dly thi ckeni ngf i l m co u l d then provide a dramatically increased f l o w path area for l i q u i d from the regionahead of any Taylor bubble to slip downwards through the annular-shaped region, past

the T a y l o r bu bb le and into the regio n beh in d the bub ble . As the f l o w rate of thedownward- t rave l ing f l u i d i n the annul us regions increases, the ov era llfrictional shear on

the pipe tube may become downwar d (Wal l is 1968). In such cases the overall l i f t

efficiency falls rapi dly . Thu s, incr easi ng pipe diameter a bove the stable bu bb le diame ter

fo r a given f l o w f i e l d may reduce efficiencies for long a i r l i f t pumps o perat ing in the slu gf l o w regime.

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1.7 - SummaryT h e mo tiv ati on for this wor k is Ca n apply a i r l i f t pump technology be practically appliedto c i v i l engi neer ing wor ks such as open channel drainage of urba n sto rmwa ter ?

A n a i r l i f t pu mp is a deceptive ly sim ple two-phase f l o w de vic e than can operate in severalf l o w regimes, depending on several geometric and f l o w parameters. A i r l i f t pumps havebee n the subject o f a smal l amoun t o f research since their inv ent ion in 1797 by C a r l

Loescher . Si nc e then they have been a pplie d exten sive ly in a smal l num ber o f special ized

applications but not to high-flow, l o w - l i f t , low-submergence c i v i l engineeringapplications such as open-channel drainage and storm water management. A i r l i f t pump

efficiency is maximized in scenarios in which submergence is high, gas and l i q u i d f l o wrates are low and aeration efficiency ishigh. Despite the fact that low-head high-flow

applications do not promise very efficient operation of a i r l i f t pumps there are significantreasons such as lo w inst all ed cost, ease of maintenance, reduction of envir onm enta l

impact o frunoff water, etc. to investigate them for these uses.

This thesis cons iders the appli cati on of a i r l i f t pumps to these c i v i l engineering

applications an d outlines a four-stage experim enta l prog ra m underta ken at the Univers i ty

o f B r i t i s h C o l u m b i a and the C i t y o f Richmond , B r i t i s h Columbia . Thi s study had several

objectives. These were namely: to first evaluate the potential for a i r l i f t pumps in urban

drainage and other low-sl ope open-chan nel applica tio ns, to create a mathematical

descriptive model of low-head,high discharge a i r l i f t pump systems, to develop a

practical des ign metho d for such pumps us in g the math emat ical mo del above, and to

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illustrate the use of that method. Totheseends, small-scale and full-scale models werebuiltand tested.Waterand air flows andlevelswererecorded.Abroadliterature studywasundertaken.Fromthis theoreticalbackgroundand experimental observations, threemathematical models forpredictingairliftpump behaviour inthesesettingsaredeveloped. One issuggestedas representative. A simplehand-calculatordesignprocedureis explained and two personal computer-based solutions are suggested. Apracticaldesign example is presented, and conclusions and recommendations for furtherdevelopment are made.

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C H A P T E R 2

2.1 -Introduction- Literature ReviewThis chapter describes a brief history of the open literature on a i r l i f t pumps, prov idi ng anoverv iew o f the develo pmen t and theory behin d their oper ati on as w e l l as an over vi ew o f

a i r l i f t theory development to the present day. This literatu re search first inv est igat ed thehistorical use of a i r l i f t pumps in c i v i l en gineer ing applicatio ns. N o men tio n was foun d.Broaden ing the scope of the search revealed a niche body of literature concerning a i r l i f t

pum ps in the process engineer ing f i e l d , documen ted ma in ly in the disci plin es o fAquacu l tu re and C he m i ca l Engineering.

2.2 -Developmentof AirliftPumpTheory, 1797 to PresentA s no ted in Cha pter 1, C a r l Loescher, a German m i n i n g enginee r, is thought to have been

first invented the a i r l i f t pump in 1797 (Giot 1982). Loe scher 's inv ent ion was an attemptto simplify the pum pin g tasks indeep mines. Submersib le rotom achinery was not

avai lable in the late 1700's and the benefits o f a pneu ma tica lly -ope rat ed sys tem are

immedia te ly evident inthat context.

A i r l i f t pumps became popular several decades after Loescher's first models, during the

middle 1800's ( Wa r d 1924). A t this tim e direct pneu mat ic powe r was widely availa ble in

the form of boiler s team which was eas il y generated at hig h pressure. Pn eu ma ti c powe r

was also availablefrom ste am-powered compressors. Far aday 's discover y of

electrom agneti c in ducti on in 1831 led the way to the inven tio n of the electric moto r. This

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and theappearance o f theinternal comb usti on engine pioneeredb yR u d o l f Dieselan d

others at the en d o f thesame century made compr essed air aviab le source o fpower .

Sh a w (1920) first suggested avo lume ra t iofor the gas an dl i q u i d phases i n al o n g a i r l i f tpump riser tube operating at 100% efficiency:

Volumeair = QWMerg-H,\7~1 f rtVolumewaler

discharge In(P

aerationdepth(1)

aeratiP

discharge J

Sh aw 's is thefirst attempt found i n theopen literature toquantify a i r l i f t pump behaviouron aphysical basis .Eviden t ly hisrelationshipw a ssuccessfully used i ndesign with anefficiency multiplier added, o n theorder o f50 % (Zen z 1993).

W a r d at theUnivers i ty o fWiscons in di dt hefirst serious experi men tal study o f a i r l i f tpumps found i n1924.This study focused o n thebehaviouro flong a i r l i f t pumpsand

attempted tocreate functional relationships between the air an dwater phase f l o w rates,

efficiency a n dpu mp riser geometry such aspum p length a nddiameter. W a r d developed

an elaborate curve-fit t ing algo rithmfor use indesignbu t wason ly moderately satisfied

with theresults a n dqualified thetechnique's applicati onto thel o n g pump risers in his

study.

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W a r d presented sixtee n sum ma ry conclu sio ns in his study. M a n y o f Wa rd 's results and

suggestions form the on goi ng co mm o n basis for subsequent use and under stan ding of

a i r l i f t pum pin g systems. Here is a summa ry of Wa rd 's eight most sal ient conclu sio ns:

1. The efficiency o f long a i r l i f t pumps depends pr imar i ly on f l o w condi tio ns in the riserpipe, and thus great refinement in aeration and foot piece design beyond ensuring

m i n i m u m f l o w rest rict ion at the entran ce are not necessa ry i n mo st cases.

2. There is a ma xi mu mefficiency for every comb ina tio n of pum p geometry a nd

submergence that depends on water f l o w rate.3. M a x i m u m efficiency occur s at sub mer gence ra tios of greater than 70 % in mo st cases,

(ie: when over 70% of the total length of the riser tube is submer ged) alt hou gh ver y

smal l diameter pumps can operate with rela t ivelyhigh efficiency at lo wer

submergence ratios.

4. H i g h efficiency is poss ib le at lo wer sub mer gence ratio s if the aeratio n depth is deep.5. The com bi ne dfriction and slip losses due to the f l o w i n a i r l i f t r iser pipes f o l l o w a

different l aw than those that govern the f l o w of water or air in a pipe.

6. There is a rela tiv ely sim ple relat ion between frictional losses and veloci ty o f f l o w i n

an a i r l i f t riser pipe for any par ticu lar mi xtu re o f air and water.

7. Sm oo th joint s in a i r l i f t riser pipes are necessar y to avo id unnecessary losses. Sudden

expansion or contraction is very detrimental to efficient operation.

8. A i rl i f t p um ps o f less than forty feet i n len gth are l i k e l y to gi ve results mu ch differen t

to those encountered in long pumps. Lossesthat are relativelyinsignificant in large

pum ps becom e importan t in short a i r l i f t pumps.

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Eight years later i n 1932,Pickert publis hed The Theor yo f the A i r l i f t P u m p in an

attempt toelaborate on themechanics o f the f l o w i nthese units. His study didno t present

results greatly contributoryto thebehaviouro f thelarge diameter, l o w l i f t ,lo w

submergence high f l o w pumps o finterest i nthis study .

M o r e than 25 years passed unt i l Govier , Radford &Dun n 's The Upwar ds V e r t i c a l F l o wo f Ai r - W a t e r M i x t u r e s appeared i n 1957. Their experimental s tudy wasbased o n a1.025 diameter pu mp riser 3 0 ' long (ie: length-to-diameter ratio approximately 350:1).

They were able toaccurately predict f l o w pattern, head loss an dslip veloci ty butrestricted theappl ica t iono ftheir resu ltsto thebehaviouro fpum p units o fs imilar riser

tube diameters when pumpi ng mixtures o fs imilar gas an dl i q u i d properties.

D J N i c k l i n ' s The A i r l i f t Pump: TheoryandOpt imiza t ion o f1963 presented the firstsatisfactory explanationo f thebehaviouro fsmall-diameter a i r l i f t pumps in thebubb lyand more importantly ,thes lug-f low regimes. N i c k l i n ' s m omen tum balance, 2-phase driftf l u x mode l based o nmass f l o w forms th ebasis o f thebu lk o fsubsequen t re sear ch intoa i r l i f t pumps an dslug f l o w theory an dbehaviour .T h emost b roadl y used o f N i c k l i n ' sconclus ions (recast here i nconsistent term inol ogyf o rthis study) isused to characterize

the veloci ty o fTaylor bubbles in theslug f l o w reg ime i n s t i l l water:

(2)

Vtaylorbuhble~ 0.35 gDiam

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N i c k l i n also observed (l ike Ward) that although many aerators have been designed to

m i n i m i z e bub ble size and maxi mi ze bubb le distribu tion , none were successful in long

a i r l i f t pumps. He also first clarified the one-to-on e relat ion ship bet ween the sub mer gence

rati o and the average pressure gradient i n the pu mp riser tu be.

Mult iphase f l o w wa s s t i l l a nascent f i e l d i n the 1960's and develo pmen ts i n this area werehappeni ng ra pidly . In 1964, Duckler , W i c k s & C l e ve l a n d pub lis hed a two-part study

Frict ional pressure drop in two-phase f l o w . Thei r results are illustr ative o f the s t i l l -

deve loping nature of two-phase f l o w theory at that time. They found the existingcorr ela tio ns for pressure l oss in two-phase pipe f l o w to be inadequate and asserted that

There is not even a phen ome no log ical understanding o f this type of f l o w .

A s two-phase f l o w theor y was further dev elo ped, and due poss ib ly to the expl ici tsolut ion

fo r s lug f l o w operation as suggested by N i c k l i n , the study of a i r l i f t pumps continued tofocus increa sin gly on the mechani cs ofTaylor bub bles i n the slug f l o w regime, and to an

increasingly lesser degree on the bubbly f l o w , churning f l o w and annular f l o w regimes.

W a l l i s ' definit ive work,One Dimensional Two-Phase Flow, a ppear ed in 1969. W a l l i s '

text is s t i l l one of the best sources for a bro adly-fo cused col lect ion o f mos t o f the o pen

theory of one-dimensional two-phase f l o w . W a l l i s ' wo rk exposes the trem endou scomplexi ty in multiphase f l o w behav iou r and provides muc h of the foundati on for two-

phase f l o w as used today. Many frictional and veloci ty relationships developed by W a l l i s

are s t i l l state of the art in modern two-phase f l o w theory.

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Todorosk i , Sato and Hon da fol l owed N i c k l i n te n years later in 1973 wi th Perf orm anc e

o f A i r l i f t P um ps , whic h elaborated slig htly on N i c k l i n ' s approach to the slug-flowregime f l o w o fthese devices. Todor oski , Sato and Hond a modified N i c k l i n ' sexperime ntal basis for determination of the slip velocities in slug f l o w .

The interpretat ion of the various regimes of vert ical two-phase f l o w was mainlydescriptive innature unt i l 1980 when Taitel , Bar nea & Duckle r publ ished Model ing

F l o w Pattern Transitions for Steady Upward G a s - L i q u i d F l o w in V e r t i c a l Tubes . Their

study undertook mathe mati cally predicti ng the transitions between thesepatterns. Theywere able to predict whichpattern or regime of two-phase f l o w wo ul d occur under agiven set of conditions, and their approach is s t i l l used today. Tai tel , Barnea & Duckler

also provide the best of the vis ua l descriptio ns o f two-phase f l o w regimes (whichsupplied the basis for Fig ur e 2 in chapter 1). Th ei r mos t usefu l fi nd in g for this curr ent

study suggests that (i ncases i n which slug f l o w can deve lo p) the len gth o f the tur bul ententrance or transition zone region from the aeration point to the point where slug f l o wcan develop depends on the mi xtu re velo cit y and pipe diameter:

France= 40.6 Diam yjg Diam + 0.22 (3)J

In 1982, Mar kat os & Singha l produced a numerica l analysis process for two-phase f l o w .

This study was focused on bubbly and slug f l o w , much the same as those that had

prec eded it. It appears that in the bu bb ly and partic ula rly the slug f l o w regimes the

mathematical formulation for the friction and loss terms is easier to accomplish since the

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rela t ively f i x e d ge omet ry o f the ro un d or Taylor bubbles a l l o w a solution that requiresless experimenta l data for correla tion. Mar kat os & Sin ghal 's technique was devel oped for

use in deep water wells and depends on the bre akdo wn of long vertical risers into sm all er

contigu ous segments, i n effect creating a gradua lly va ryi ng f l o w formulation. It issuitable only to long riser pipes.

L o n g , s ma ll diameter a i r l i f t pumps are widely used in nuclear fuel reprocessing. V e r yaccurate estimates o f f l o w rates are required in those settings. In 1986 C l a r k & Dabolt

deve lo ped a genera l set o f design equations for a i r l i f t pum ps in slug f l o w for use in thenuclear indust ry. They focused prim ar il y on accurately predictin g the f l o w rate behaviouri n their applications. Despite their admitted inabi l i ty to accurately calculate the overall

frictional losses i n pipes of 38 m m diameter they di d pro vide an accurate de sign mo del

f o r such pum ps in the slu g f l o w regime. Interestingly they also attempted to applyN i c k l i n ' s model to a short pump and found that N i c k l i n ' s mode l ove rpre dicte d the pu mpefficiency, unl ike i ts ' better agreement when applied to longer units. C l a r k & Dabolt 's

general design equation for long, small-diameter pumps does no t address pump efficiency

i n great detail but does provide an accurate and practical means of design for very long

slender a i r l i f t pumps.

I n 1993 Ze nz produced Expl or e Potential of A i r l i f t Pumps and Mult iphase Systems

pr imar i ly ex p lo r ing a i r l i f t pumps inthree-phase scenario s. Ze nz ' study was co ncer ned

main ly with s lug f l o w a nd particulate entra inment, again in lo ng pipes. A i r l i f t pump riser

pipes are general ly consider ed lo ng when len gth to diameter ra tios are 50:1 or mo re.

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W u r t s , M c N e i l l an d Overh ult s (1994) pro vi ded a si mpl e curve- fitt ing approach to a i r l i f t

pum p perform ance fo r near -100% submergence in aquaculture and destrati fication

applications.

In 1995 Tram ba, Topal ido u, Kastr inaki s, Nyca s, Francois & Scriven er comple ted their

V i s u a l Study of an A i r l i f t Pu mp Operating at L o w Submergence Rati os whi ch is not

particularly helpful for this present study since it is ma in ly conce rne d wi th bub ble

for mat ion at a jet inle t and includes no performan ce data for non-slug flows.

F o l l o w i n g C l a r k & Dab ol t in the nuclear fuel reprocess ing industry , De Ca cha rd &Ca lh ay e created a steady-state mo del for very sma ll diameter, l on g l i f t pumps in 1995. De

Ca cha rd & Ca lh ay e's is certai nly the most extensive study found. It is co ncer ned

pr imar i ly with creating an accurate mo del for gravi tatio nal and frict iona l compon ents of

the a i r l i f t pump riser pressure gradient. L i k e C l a r k & Dabolt's work, it is focused on veryl o n g slender a i r l i f t pump s i n the slu g f l o w regime. De Cachard & Delhaye are notconce rned w it h opt im iza ti on of energy effi ciency since energy in puts are very sm al l in

their cases o f interest. De Cachard & Delhaye observed churning f l o w i n the lo wersections of their study pum p units and conc ur wit h previ ous researchers that churn f l o w is

a development phase for the slug f l o w pattern. However, they also found that churn f l o wcould exist as a stable f l o w pattern at high gas f l o w rates. De Cachar d & Del hay edeveloped the most detailed and accurate analysis framework av ailable for a i r l i f t pumpso f under 40 m m diameter and wit h length-to-diameter ratios above 250 :1.

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M o s t recently Nenes, Assim acopu los , Markat os , & Mi t sou l i s completed Sim ul ati on of

A i r l i f t Pumps for Deep Water W e l l s in 1998. Thei r anal ytical fram ework inv ol ves aninterspersed continua model and solves a system of differential equations per Markatos

(1982). Results from their system are very accurate but unfortunately suitable only for

very t a l l pipe units inwhich the pump riser tube may be broken into tens of internallycont igu ous discrete elements.

2 .3 - Su m m a r y of Li t er a t ur e Revi ew

A i r l i f t pu mps ha ve been a niche interest area in process, chem ica l and mech an ica lengineering as w e l l as aquacultur e. Pu bl ica ti on on the topic has been sparse and the

literature has tended towards attempts to explain the behaviour of these devices in two

distinct f l o w regimes. N i c k l i n ' s model (1963) continues as the base for almost alltheore tical develo pmen t whereas the nu mer ica l techniques o f Ma rk at os , Nene s et al .

(1992) promise a powerful toolset for evaluating the behaviour of long a i r l i f t units.

There has been lit tle reason to evaluate the high-f lo w, lo w-hea d, lo w-su bm erg ence a i r l i f t

systems and subsequently those applications are s t i l l unexplored from theoretical and

design standpoint s. Thi s has not stopped such pumps f ro m bei ng use d spora dica ll y and

often unintentionally since in a practical sense, s impl ici ty in f i e l d use has ten ded towa rds

ins tal l ing a pipe at an appropriate depth, adding air in an appropriate volume and at an

appropriate depth to produce the desired results i f possi ble . In a research sense, the

inabi l i ty to accurately measure the relative velocities of the air and water phases except in

the bubbly and slug f l o w r egimes have tended towar ds tuni ng a theory focu sed on those

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regimes alone. H i g h submergence, smal l diameter, short lifts have been traditionallyinvestigated since low-submergence, high-lift units provi de decreasing efficiencies.

A s W a r d (1924) concluded,there remai n inherent gaps in our understan ding o f theory

that mainly arise from the fact that the sizes, speeds and dist rib ut ion o f the air bub ble s are

not k n o wn , yet the siz e and the rate of ascent o f the bub bles th rou gh the air-wate r mi xtu re

are crit ical variables.

Recen t resea rch wo rk on air entra inmen t i n fast flowing water us in g laser optica l probetechnology with the abi l i ty to measur e the beha vio ur of the air fracti on in a two-pha se

air-water f l o w mixture as distinct from the overal l air-water f l u i d mi xtu re has recentlybecome available.This technique was employed first by Cartel l ier (1992) and later

refined by Ser dul a & Loe we n (1998), whose techniques might seem to pro mis e a mor e

rigorous approach to air l i f t pu mp design by the direct measu remen t of gas and l i q u i d

phase velocit ies and v o i d rat io. Unfor tun ately , invest igatio n of the experimen talequipment and personal conversations with L oe we n suggest that since the laser system

employed is a'poi nt measu reme nt syst em it is not suitabl e for air -water mixtu res with

recircula tory movement. It cannot resolve differences between upward-moving and

recircula t ing air bu bbl es and does not functi on w e l l witho ut distinct boun daries between

the air and water phases at the bu bb le bounda ries such as are fou nd in bu bb ly and slu gf l o w . Unfortunately this means that at least curr ent ly the laser measur emen t te chno lo gy isinapplicable to the study of a i r l i f t pu mps i n the chur n f l o w regime.

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C H A P T E R 3

3.1-Overviewof the experimental programFo r a i r l i f t pumps to be used effectively in short l i f t , high f l o w applicat ion s such as sto rmdrainage conduits, the a i r l i f t pump must be able to l i f t large volumes of water through aheight o f abo ut 0.3 to 0.6 m. Fo r exa mpl e, such an increase i n head ov er a run of 50 00

feet i n re la ti ve ly flat terr ain su ch as exists in Richmond , B . C in the 5' by 9' concre te b ox

culver t leadingfrom Granvi l l e Street to the Gilbert Road outfall could e asil y result in a

doubled water surface slope and subsequent dra mati c impr ovem ent s in water f l o wveloci ty, and subsequent reductio n of l o c a l flooding durin g extreme rainfall events.

A pu mp syst em for occas io nal use in emer gency situation s such as mig ht be experi ence d

by R i c h m o n d du ri ng the 10-year desi gn f l o w should ideally be inexpensive and

maintenance-fr iendly. Sin ce the pum p units w o u l d run on ly duri ng extreme conditi ons ,

and since operat ing costs i n extreme con ditio ns are often accoun ted for differently than

ongo ing costs, efficiency is on ly important in so much as it affects the first cost of the

insta l la t ion. Running costs are less important as the pumps are o n l y used during extreme

storm even ts - in the order o f once eve ry two or three years. Howe ve r, ins tal led cost is

important - of course less expensive is preferred. A i r l i f t pu mps prom ise a ver y attractive

match to these crite ria . The com pre sse d air su pply can be dry and out o f the way , in fact

there is no need for the supplyapparatus to be perman ent ly lo cate d sin ce air can be

supplied through a flexible pipe.This means that a permanent pu mpho use need n ot

necessarily be used with an a i r l i f t system. The pumps themselves can be bui l t quite

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inexpensively as they only consist ofsets o ftubes and aerators with an air supply.

Because a i r l i f t pum ps are not orio usly inefficient compar ed with their rotodynamiccounterparts and air compressors are expensive, it is very desirable to have the ratio of

water l i f t e d to compre sse d air used be as hig h as poss ibl e.

These design considerations and potential benefits were investigated, motivating the

current study. Preli mi na ry calculati ons were made and two series of pre li mi na ry

qualitati ve experiments were run at the Univ ers it y of B r i t i s h C o l u m b i a C i v i l Engineer ing

Hydraul ics Laboratory to check the concept. C l a s s i c a l a i r l i f t pump component s andlayo uts were con side red and adapted for use in a l o w - l i f t s itua tion . Si nce the desire wasto determ ine whethe r a vi ab le a i r l i f t pump could be developed for these applications itwas reasonable to start with a system that was configured s i m i l a r l y to what a wo rk in gunit might be.

First a small-scale a i r l i f t u nit was buil t us in g the f u l l width of a 6 inch wideundergraduate student hydrau lics lab flume, explo rin g the conceptual layou t for a f u l l -

width b ox culve rt instal latio n.

Subsequently a s imi l a r larger-scale a i r l i f t u nit was buil t us in g the f u l l20-inch width of a

large hydr au li cs lab flum e to check if the system w o u l d be functional on a larger scale.

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The labor ator y experimen ts pro vi ded some va lua ble insights into the nature o f a i r l i f tperformance at low l i f t s , l ow submer gence and lo w v o i d ratios. They also showed thata i r l i f t pu mp s of this type could be practical.

Next a sequen ce offull-scale pro tot ype experim ent s was car rie d out at the Gilbert Road

s torm drainage outfall i n Richmond. Severa l full-scale experimental prototype layou ts

and systems were planned and tried.Var ious combi nati ons of upstream and downs trea m

water levels were investi gated with va ry ing rates of air injection. Riser pipe diameter was

investigated, as was aerator geometry.

Since evalua t ing and m a x i m i z i n g water f l o w fo r these pump systems was the end goal ofthis study, in allcases it was attempted to determ ine the water flo wrat e pos si bl e for a

given upstream and downstream depth, rate of air injection, pu mp riser diamet er an d

aerator geometry.

There were many practicaldifficulties such as unus ually lo wflows an d water lev els in

the drainage conduit that was used as the site. However,these experime nts pro duced

several very useful results. They demonstrated that low-head,high-flow, l o w -

submergence a i r l i f t systems d id pro vide a via ble and practi cal alternative i n an ins tal led

s torm draina ge system. Ho wev er , they also sho wed that there was considerable

circulat ion i n the pu mp tubes and as a result, the water was being lifted sever al times with

resul t ing l o w overall efficiency. They also showed that there was never a steady state

si tuat ion such as is usu all y assum ed inder iving theory and formulae. The air-water

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mi xtu re was ver y turbu lent and the air bub bles were in crea sin g and decreasi ng in size by

shear ing an d coale scence as they rose, in effect al ways in a transient co ndi ti on .

Ha vi n g i dentifi ed the major pro ble m ofcirculat ion and re-cycl ing, a f i n a l set ofexperiments were set up at the RichmondPubl ic W o r k s Y a r d , usi ng banks o ftubes 75 to

200 m m in diam eter , as oppos ed to the 250 an d 300 m m tubes used in the Gi lber t Road

prototype experiments. Theory suggested that smaller diameter pipes would al low less

circulat ion due to a mor e eve nl y distri but ed air phase. A l s o , the riser pipe walls would

have a much greater influence over a larger cross-sectional f l o w area. Trials were alsomade with the tubes incl ined i nstead o f ver tica l, as incl ined tubes w o u l d be easier to

instal l and co u l d be potentially less costly due to a reduced number of fittings required

fo r construction.

The results from the fourth experimental setup were successful an d sho wed littl e

circulat ion, although there was s t i l l consider abl e uncert aint y as a result of the transient

nature of the under lyi ng phenomen on of the air bubbles rising, expanding, shearing and

coalescing. Sin ce the experimenta l pumps were s imilar to the proposed f i n a l design the

results were considered acceptably accurate. The design concept was thus considered

proven and the relationships developed sufficient for design of a practical operating a i r l i f t

pump.

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3.2 - The Expe r i me nt a l Setups

The first experimental laboratory setup is sho wn in Figu re 4. The purpo se o f this first

setup was to b u i l d a visual model of the a i r l i f t pump as a full-width ele men t in a storm

drain scenario. Because o f kn own l imitatio ns in width, discharge rate, f l o w ratemeasuremen t equipment and theoretical knowledg e, this first setup was intended to serve

as abase for experimentation to aid in understanding a i r l i f t pu mp behavio ur, rather thanas an instrumented data col lect ion experiment. This system was designed to simulate on a

very smal l scale the original proposed layout of an in-culvert a i r l i f t pumping system.

Upstream water flowed int o the system under a baffle. A n aerator i nst al led on the base o fthe channel s uppli ed bubbl es to the water co lu mn . The air-water mixtu re then flowed

betwee n the upstre am ba ffle and a down str eam baffle, exit in g the pu mp uni t at the hi gher

downs tream l e v e l .

The sma ll-sca le system was in stall ed in a six-inch wid e student hydr au li cs lab flum e to

test the concept of a full-width a i r l i f t system in a rectangular channel. Various

combinat ions o f upstream and downstream water levels and air vo lu me inputs were trie d

i n order to ma xi mi ze the water flowrate give n any combi nat ion of upstream and

downst rea m lev els. Sever al geometries were tried since all of the variou s s ystem

elem ents were modu la r. The mos t effective lay out found is sho wn in Fi gu re 4.

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F I G U R E 4- F i r s t L a b o r a t o r y A i r l i f t P u m p i n g S y s t e m

Preliminary Lab AirliftPumpingSystem1 n ,oto

al ldimensions in mm

Several aerator designs were also tried, with little improvement inefficiency. Ci rcul ati on

was evident as a ver y impor tan t (and pre vi ou sl y mu ch under-esti mated) effect in these

high-flow, low-submergence scenarios.

T h e best performing setup in the prel imi nar y experiment was measure d for performa nce

and pr ov id ed the first clues to the shapes of pu mp dischar ge curves for systems of this

nature. Fig ure5 shows the sample data set and resulting discharge curve for this system.

T h e second experimental setup was a simpletest intended to determine the poss ibi l i ty o f

a larger-scale system based on the same conceptual layout as the first small-scale system.

T h e lar ger scale sys tem bu il t in a large 20-in ch wid e hydr au li cs flu me at the Univers i ty o f

B r i t i s h C o l u m b i a Department of C i v i l Engineer ing .This system was designed todetermine the feasibil i ty o f a i r l i f t pump technology at prototype scale for very shallow

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F I G U R E 5 - First Laboratory Airlift PumpingSystem ResultsPreliminaryAirliftPump Curve

0.8000.7000.6000.500

$5 0.400sx

0.3000.2000.100.000-0.000

4

y - O.O003xJ+ 0.O


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ai rf low were not coll ecte d. Thi s was not cons ider ed a drawb ack because the larger scale

laboratory a i r l i f t uni t di d pro ve the con cept at the prot oty pe scale despit e seri ous

submergence limi tati ons and limitat ions in the air f l o w rate possible fro m the inst alled

screw compressor-b ased air deliv ery system. Figu re6shows the second exper ime nta l

setup and Table2 shows numerical results of this phase of the stu dy.

F I G U R E 6 - Prototype ScaleLaboratory Airlift Pumping System

liftchamber length 18"

V

Qwater i ^ H u/sH d / s

If QairSe c o n d Phase A i r l i f t Pump Test SetupU B C C i v i l Engine er in g Hydrau l ics Labora t oryflume width20three-tined 3/4 brass aerator,3 x 30 ea. orifices 1 mm dia.

lift chamber planview with aeratorT18"_L

2 0

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T A B L E 2 - Prototype ScaleLaboratory Airlift Pumping System ResultsAirliftFlowTest2AaronBohnenUBC Civil Engineering Hydraulics Lab

Flowbaffle height HdsWeircrest height PweirWeircrestwidth WweirCoefficientofDischarge= 0.63forthistest.Q=Cd*(2/3)*L*HA(3/2)*SQRT(2*g)

25.5 in23in

19.5in0.65m0.59m0.50m

Head d/s Headu/s(Hds, in) (Hus,in)

Weir head(Hweir,in)

lift(deltaH,in)

Flow(m A3/s)

Flow(l/s)

Flow(cfs)

25.525.525.525.525.525.525.525.525.525.525.525.525.525.5

26.024.524.023.022.522.021.520.318.517.016.015.014.514.0

5.55.35.04.54.34.34.03.52.82.01.51.00.50.3

-0.51.0I. 52.53.03.54.05.37.08.59.510.5II .011.5

0.0500.0460.0430.0370.0340.0340.0310.0250.0180.0110.0070.0040.0010.000

49.546.242.936.633.633.630.725.117.510.97.13.81.40.5

Notes:Pressureat 100 psidelivered, approx.4 psi ataerator20"widein 39" tallflumefour-tined3/4"diamaerator-1mmholes

1.751.631.521.291.191.191.090.890.620.380.250.140.050.02

The limited airflow avai lablefrom thescrew-based compressor sl owe d devel opmen t untila four horsepower gasoline engine-powered centrifugal blower was obtained from theuniversi ty equipment salvage program. The blower was overhauled, performance wasevaluated and fittings were designed toadapt it to theexperimen tal setup. The centri fugal

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F I G U R E 7- Gilb ert Road Prototype A i r l i f t System Lay ou t


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F I G U R E 8 - Gilbert Road Prototype AirliftSystem Components


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Co mpr es se d air was su ppli ed to diffusers located beneath each pump unit by a 28

horsepower Co ma ir -Ro tr on positi ve displacement blo wer unit and pipe distr ibu tio n

syste m. Thi s uni t was ins tal led i n a sou ndproo fed shed and equipped wi th intake and

discharge filters and silencers. Since positi ve displacement b lower s provi de a constant

rate o f ai rf low, in dividual va lve s were ins tal led at each pump un it and a bypa ss added. In

this way each pump unit could be tested individual ly. Ven turi-s ty le air velo citymeters

were al so insta lle d to a l l o w air f l o w to each pump unit to be ind ividua l ly monitored.Figure 9 shows the air supply system at the Gilbert Ro a d site. Figu re 10 sho ws the

prototype system i n operation . Large-scale site drawings in Ap pe nd ix 2 show theinsta l la t ion o f the air suppl y subsyst em at the Gilbert R oa d location.

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F I G U R E 9 - Gilbert Road Compressed A ir Supply Subsystem

2 > LONG RADIUS90 ELBOW (TYP.)

3 0 AIR FLOW METER

AIR FLOW

3 0 AIR PIPE

3 0 3 -WA Y WYE4 x3 REDUCER

4 LONG RADIUS90' ELBOW

STEEL LADDER

2 x3 REDUCER

2 0 CONTROL VALVE

4 0 AIR SUPPLY

DETAIL Y

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F I G U R E 10 - G i l b e r t R o a d P r o t o t y pe A i r l i f t Sys tem in Oper a t io n

Th e or iginal system as tested was moderately successful at pumping water and provided

tremendou s insi ght into the operation o f the pump units, part icul arl y by the abil i ty toobserve the mixture flow pattern i n the acryl ic ten-inch diameter unit (the centre unitshown in Figures 9 and 10). The or iginal prototype setup identifi ed several weaknesses i n

the phy si ca l layo ut and const ructi on of the layout at the prototype site. Leak age between

upstr eam an d downs tre am chambers was found to be part icul arl y prob lem ati c.

Addi t iona l ly , the ab nor ma lly lo w level s o f water in the drainage con duit leadi ng to the

site over the win te r o f 1997/1998 made t estin g at onl y one level of upstream f l o wposs ible. A portable pump was introduced to increase the level in the upstre am condu it

but this had onlyl imi ted success.

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These difficult ies le d to dela y i n this phase o f the pro gr am as several rev is io ns to the site

system la yout and air distr ibu tio n layo ut were developed, drafted and implem ent ed. This

work progr esse d ove r m u ch of the Spr in g o f 1998.

The results from th e tests o ftheseproto type units were mo re scattered than expected but

clear ly sh owe d the import ance o f design details. Al t ho u gh reduced, leakage between

chambers cont inu ed to be problem ati c despite the system revisi ons , and a br ea kdo wn of

the compr ess ed air del iv er y syst em created further difficulties.

Som e of the data and calculat ionsfrom the third experim enta l setup are shown in Table 3.

Table 4 shows sample veloci ty an d loss calcul ati on s for the data sho wn in Tab le 3. Tab le

5 shows the leakage test data coll ect ed at this site. Tab le 6 sho ws a sample o f later data

and also cal cul ati on s for the loss coefficients o f the three original prototype pu mp

systems at the Gilbert Road site.

W h e n ana lyze d, the results o f this phase o f testing indicate d system ic prob lem s wi th the

alternatives b ein g investiga ted. The large diameters pipes had ver y l o w pa cki ng density

i n the space-constra ined storm drai n scenario. A l s o no aerator geometry was found to be

highly su ccessful in sharply ma xim izi ng efficiency. This wa s l i k e l y due to several

factors, p r i m a r i l y the practical issue of leakage and the prevalent reci rcul ati ng f l o wpatterns in the pum p riser s.

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T A B L E 3- Gilbert Road Prototype Airlift System Sample Experimental DataResults march9,1998Outsidew l= 33 Vee notch =34 inches

Pump U/wl d/swl aircfm Flow pipe dia area qmix vmix headless Mi xdensityvwat vair vrel2.5 8

35.000 40.25 250 0 676762 0 833 0 54498 4.843429 8.887344 35.7942 0.391054 0.485614 12.55535 12.0697434.500 39.75 250 0 578271 0 833 0 54498 4.744937 8.70662 35.313 0.395151 0.419289 12.64>t 12.2211134.500 39 250 0 450973 0 833 0 54498 4.617639 8.473037 33.44365 0.411212 0.340279 12.98521 12.6449339.000 41.5 . 250 0 974318 0 833 0 54498 5.140985 9.433339 41.45398 0.413587 0.739413 13.0378 12.2983938.750 41.25 200 0 908704 0 833 0 54498 4.242037 7.783834 28.22426 0.500209 0.834052 12.23798 11.4039335.250 40.75 200 0 786746 0 833 0 54498 4.120079 7.56005 26.6247 0.45895 0.66255 11.30473 10.6421835.000 40.5 200 0 730287 0 833 0 54498 4.06362 7.456452 25.9 0.462329 0.619532 11.37578 10.7562435.000 40.5 150 0 730287 0 833 0 54498 3.230287 5.927345 16.3665 0.552526 0.740398 10.25159 9.51118935.000 40.75 150 0 786746 0 833 0 54498 3.286746 6.030943 16.94361 0.543329 0.784363 10.04514 9.2607837.750 41.62 150 1 006934 0 833 0 54498 3.506934 6.434972 19.28984 0.562277 1.038892 10.47997 9.44107638.000 41.5 100 0 974318 0 833 0 54498 2.640985 4.846018 10.9397 0.675072 1.206897 9.411976 6.20507934.500 40 100 0 626111 0 833 0 54498 2.292777 4.207082 8.245128 0.658465 0.756489 8.954315 8.19782640.250 41 250 0 846199 0 833 0 54498 5.012866 9.198249 39.41356 0.406102 0.63056 12.87348 12.2429233.500 38 250 0 316525 0 833 0 54498 4.483191 8.226335 31.5245 0.356521 0.207068 11.88156 11.674535.000 38 200 0 316525 0 833 0 54498 3.649858 6.697228 20.89419 0.443392 0.257522 10.98875 10.7312339.750 41 200 0 846199 0 833 0 54498 4.179532 7.669142 27.39864 0.471078 0.731449 11.56395 10.832537.000 40 150 0 626111 0 833 0 54498 3.126111 5.736189 15.32789 0.524148 0.602177 9.640225 9.03804835.500 39 150 0 450973 0 833 0 54498 2.950973 5.414823 13.65853 0.5125 0.424095 9.40989 8.985795

T A B L E 4 - GilbertRoad PrototypeAirlift System SampleExperimental ResultsResults M a r c h 9,1998

1 2 3 4 5 6 7 8 9 10 11 12 13Pump U s / w l d/s wl Air Water V m i x Dens V w Head loss t Wm A 2 V m A 2 * D e n U V w A 2 -exit/vwA2

ins. ins. cfs cfs ft/sec ft/sec feet2 35.00 57.75 4.17 0.68 8.96 0.23 5.53 1.44 1.16 5.12 3.03 2.44

34.50 57.75 4.17 0.58 8.78 0.21 5.05 1.46 1.22 5.78 3.69 3.0534.50 57.75 4.17 0.45 8.54 0.19 4.34 1.55 1.36 7.10 5.29 4.5539.00 57.75 4.17 0.97 9.51 0.27 6.76 1.60 1.14 4.28 2.26 1.73

1.002 38.75 57.75 3.33 0.91 7.83 0.30 5.54 1.42 1.49 4.92 2.98 2.38

35.25 57.75 3.33 0.79 7.61 0.29 5.10 1.21 1.34 4.71 2.99 2.3635.00 57.75 3.33 0.73 7.51 0.28i nn. 4.89 1.23 1.40 5.07 3.31 2.65

2 35.00 57.75 2.5 0.73 5.97 1.UU0.34 4.00 0.96 1.74 5.16 3.87 3.1235.00 57.75 2.5 0.79 6.08 0.35 4.19 0.92 1.61 4.63 3.37 2.6537.75 57.75 2.5 1.01 6.48 0.38 4.87 1.00 1.53 3.99 2.71 2.03

1.002 38.00 57.75 1.67 0.97 4.89 0.48 3.79 0.62 1.66 3.49 2.76 1.97

34.50 57.75 1.67 0.63 4.24 0.41 2.81 0.60 2.15 5.22 4.89 3.951.00

1 40.25 54.5 4.17 0.85 9.27 0.25 6.27 1.85 1.38 5.54 3.03 2.4833.50 54.5 4.17 0.32 8.29 0.17 3.43 1.60 1.50 8.80 8.77 7.7735.00 54.5 3.33 0.32 6.74 0.20 2.86 1.59 2.25 11.00 12.54 11.4039.75 54.5 3.33 0.85 7.72 0.29 5.32 1.62 1.76 5.97 3.70 3.0837.00 54.5 2.5 0.63 5.78 0.32 3.64 1.30 2.50 7.86 6.32 5.5135.50 54.5 2.5 0.45 5.45 0.28 2.93 1.31 2.84 9.98 9.80 8.82

Outside wl=33 V e e notch=34 Average#2 1.48 4.96 3.43 2.74A v .#1 2.04 8.19 7.36 6.51Sdev#2 0.28 0.91 0.89 0.82Sdev#1 0.58 2.17 3.69 3.46CV#2 0.19 0.18 0.26 0.30C V # 1 0.29 0.26 0.50 0.53

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T A B L E 5 - Gilber t Road Prototype A i r l i f t System Leakage TestsP u m p Da t afromM ay1 testsN o 3 p u m p - 1 2A ir U / s W , L D / S W . L W e i r W e i rflow L e a k s Tota l

250 46.5 50.5 41.75 1.127673 0.33775 1.465423250 44.5 50 41.75 0.974561 0.334608 1.309169250 37.5 48 41.75 0.489537 0.321734 0.811271250 38 48.75 41.25 0.769405 0.326621 1.096026250 46 50 41.25 1.127673 0.334608 1.462281250 42.5 49.5 41,25 0.974561 0.331436 1.305998200 4 5 50 41.75 0.974561 0.334608 1.309169200 38.25 48 41.75 0.489537 0.321734 0.811271150 47 50 41.75 0.974561 0.334608 1.309169150 44.5 50 41.75 0.974561 0.334608 1.309169150 38 48 41.75 0.489537 0.321734 0.811271100 45.5 49 41.75 0.707362 0.328234 1.035596

N o 2 pump250 48 49 41.75 0.707362 0 .328234 1.035596250 4 5 48 41.75 0.489537 0.321734 0.811271250 37.5 47 41.75 0.317686 0.315099 0.632785220 39 48 41.25 0.592484 0.321734 0.914218200 45.5 48.5 41.75 0.592484 0.325 0.917484150 48.5 49 41.75 0 .707362 0 .328234 1.035596150 45.5 48.5 41.75 0.592484 0.325 0.917484150 39 47 41.75 0.317686 0.315099 0 .632785100 45.5 48 41.75 0.489537 0.321734 0.811271

N o 1 pump250 48 49 41.75 0.707362 0.328234 1.035596250 4 5 48 41.75 0.489537 0 .321734 0.811271250 38.5 4 7 41.75 0.317686 0.315099 0 .632785200 46 48.5 41.75 0.592484 0 .325 0.917484200 38 47 41.75 0.317686 0.315099 0 .632785150 49 49 41.75 0.707362 0.328234 1.035596150 4 6 49 41.75 0.707362 0.328234 1.035596150 39.5 47 41.75 0.317686 0 .315099 0 .632785100 46.5 48.5 41.75 0.592484 0.325 0.917484

4 9


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T A B L E 6 - GilbertRoadPrototypeAirliftSystem SampleExperimentalResults2Tests May1,19981 2 3 4 5 6 7 8 9 10 11 12 13Pump U/Swl d/swl Air Water Pipearea V mix Dens Vw Headloss UVm*2 Ud vmA2 UVw2ins. ins. cfs cfs sq.ft. ft/sec ft/sec feet3 46.50 53.50 4.17 1,80 0.79 7.60 0.38 5.99 1.86 2.07 5.42 3.34

3 44.50 53.50 4.17 1,31 0.79 6.97 0.33 4.98 1.88 2.50 7.46 4.893 37.50 53.50 4.17 0.81 0.79 6.34 0.28 3.73 1.53 2.45 8.84 7.083 38.00 53.50 4.17 1.10 0.79 6.70 0.31 4.49 1.44 2.06 6.62 4.593 46.00 53.50 4.17 1.46 0.79 7.17 0,35 5.31 1.95 2.44 6.96 4.443 42.50 53.50 4.17 1.31 0.79 6.97 0.33 4.98 1.72 2.28 6.82 4.473 45.00 53.50 3.33 1.70 0.79 6.41 0.43 5.07 1.56 2.44 5.72 3.913 38.25 53.50 3.33 1.20 0.79 5.77 0.37 . 4.09 1.21 2.34 6.27 4.653 47.00 53.50 2.50 1.31 0.79 4.85 0.46 3.66 1.61 4.41 9.68 7.773 44.50 53.50 2.50 1.31 0.79 4.85. 0.46 3.66 1.40 3.84 8.43 6.763 38.00 53.50 2.50 0.81 0.79 4.22 0.39- .2.65 1.12 4.07 10.45 10.303 45.50 53.50 1.67 1.04 0.79 3.44 0.52 2.53 1.22 6.66 12.76 12.372 48.00 57.75 4.17 1.04 0.55 9.55 0.28 6:91- 2.31 1.64 5.95 3.122 45.00 57.75 4.17 0.81 0.55 9.13 0.2S 6.06 2.19 1.69 6.89 3.842 37.50 57.75 4.17 0.63 0.55 8.81 0.22 S.27, 1.67 1.39 6.31 3,892 39.00 57.75 3.67 0.91 0.55 8.41 0.28 5.89 1.52 1.39 4.87 2.822 45.50 57.75 3.33 0.92 0.55 7.80 0.30 5.52 1.98 2.09 6.86 4.182 48.50 57.75 2.50 1.04 0.55 6.49 0.39 4.91 1.87 2.86 7.39 5.012 45.50 57.75 2.50 0.92 0.55 6.27 0.37 4.56 1.70 2.78 7.54 5.262 39.00 57.75 2.50 0.83 0.55 5.75 0,32 3.63 1.37 2.67 8.33 6.712 45.50 57.75 1.67 0.81 0.55 4.55 0.45 3.32 1.36 4.23 9.42 7.94

48.00 54.50 4,17' 1.04 0.55 9.55 0.28 6.91 2.39 1.69 6.14 3.221 45.00 54.50 4.17 0.81 0.55 9.13 0.25 6.06 2.26 1.74 7.10 3.961 38.50 54.50 4.17 0.63 0.55 8.81 0.22 5.27 1.82 1.51 6.85 4.221 46.00 54.50 3.33 0.92 0.55 7.80 0.30 5.52 2.10 2.22 7.29 4.441 38.00 54.50 3.33 0.63 0.55 7.28 0.26 4.45 1.61 1.96 7.51 5.251 49.00 54.50 2.50 1.04 0.55 6.49 0.39 4.91 2.02 3.09 7.97 5.401 46.00 54.50 2.50 1.04 0.55 1 6.49 0.39 4.91 1.77 2.71 6.98 4.731 39.50 54.50 2.50 0.63 0.55 5.75 0.32 3.63 1.50 2.92 9.11 7.341 46.50 54.50 1,67 0.92 0.55 4.74 0.47 3.60 1,49 4.26 9.11 7.38

Average #3 3.13 7.95 6,21Stdsv#3 1.38 2.17 2.77CV#3 0.44 0.27 0.45

: Average#2 2.30 7.06 4.75Std#2 0.93 1.33 1.68CV#2 0.40 0:19 0.35

Average#1 2.45 7.56 5.10Std#1 0.88 1.01 1.44CV#1 0.36 0.13 0.28

A second prototype concept was then designed andb u i l tatthe G i l b e r t R o a d l o c a t i o n .T h i s systemwasconceived in an attempttomaximize theuse o fthe availablep l a n area inthe constrained spaceo fa drainagec o n d u i t . Theconceptwasbased on the o r i g i n a llabm o d e lthat used the f u l l w i d t h o fa s m a l l flume.A f u l l - w i d t h b u i l t - i npump assemblywasd e s i g n e d . Itformedac o n t i n u o u sside to side element in thebaseo fthe drainage conduit.

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Such a unit w o u l d have superio r aeratio n density and ma ke ma xim al ly -ef fic ien t use of the

l im i ted pl an area in the base of the condu it. The resul t was a later al slot-b ased pu mp and

aerator. This unit was built in the form o f a slot four feet long by one foot wide for the

air-water mixtur e. A ho rizo nta lly orientedcyl indr ical aerator was designed and installed

at the base o f the uni t. If this pro ve d succes sful the int ent io n was to adopt the des ign

concept and b u i l d a i r l i f t pump units that could s pan across the entire widt h o f rectangu larb o x culvert. Large-scale drawings of the slot-configured a i r l i f t pump system can be foundi n Ap p e n d i x 2. Figure 11 shows the slot-configured a i r l i f t pump in operation.

Figure 11- Slot-Configured A i r l i f t Pum p in Operati on

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Thissystem wastestedunderadverse conditions with very little upstream depthavailable. Nevertheless,itidentifiedanunanticipatedand major problemwith the "slot"design.Watertended to "slosh"fromside to sideinthepumpunit body, but very littlewas effectively lifted. It was observed that when the water was high at one end ofthe slotitgavea large enoughbackpressure to the orifices there to createanincreased flow ofairfromthe orifices at the otherend.In this way theairtended toescapefromthe system.Whenthe water sloshedbackto the other endofthe system theairescapedfromthe firstend.Thus,although a considerable amount of spray was created very little water was

pumped.Theimmediate failure ofthisdesign showed convincingly that large capacityairliftpumpsystemsmust be designed to prevent this sloshing behaviour, effectively aone-dimensionalrecirculationeffectanalogous to that whichhadbeen observedinthecylindricalunits.Thistestconfirmedthefindingsofthe firsttest,namely thatcirculationcouldeasily develop within thepump riserpipes, greatlyreducingpumpefficiency.

Thethirdexperimental phase was successful inpointing the wayforward. Thedesignconcept was revised to minimize the two mostsevereproblems encountered at theGilbertRoadsite,namelycirculationwithintheriserpipesandleakagebetweenthetestchambers.Thelarge tenandtwelve-inch diameterpumpbarrelswere replaced with eight,six, four,andthree-inch units.Thiswas considered a useful means ofreducingcirculationandturnedout to be very effective. It was also decided totesttheeffectofincliningthepumptubes.Wallis(1969)assertsthatinclinationuptoapproximately40degreesfromthe verticaldoesnot adversely affect bubble velocity,and incliningthepump risertubesinthis way promised reduced constructioncostsbyrequiringfewer pipe fittings.

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FIGURE 2- Richmond Public Works Experimental Setup

fm+->C O(DH

O H > HH COao3

4H

5bP H 1 *S ' 5

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T A B L E 7- R i c h m o n d Pu b l i c W o r k s Sa m pl e E x pe r i m e n t a l Da t a

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A t this poin t the head loss relati ons hips described i n equat ion s (35) and (36) i n chapter 3

were created and used to characterize the system behaviour. A f i n a l set o ftests weremade wi th a bundl e o f ni ne, fou r-i nch diameter plast ic pipes at an in cli na ti on o f 0 to 40

degrees from the ver ti cal . Co mpr ess ed air was suppl ied thro ugh a ma ni fo ld o f pipes with

a one inch jet at the centre of each pump riser pipe.

A l t h o u g h so me practical probl ems remai ned, the performance o f this experime nta l setup

confirmed that the relati onshi ps develo ped in the mode l for turb ulent m i x i n g formed a

reasonable basis for a i r l i f t pum p design i n the chur n turbu lent re gime . Thi s successfulphase o f the progr am resulted i n a reliabledata set, pro vi din g the basis for calibr ati on o f

the theoretical model and pointed the way towards a viable a i r l i f t pump design for thesi tuat ion in Richmo nd.

3.3 - Results of the Experimental Program

The lessons from the first two laboratory-based phases of the experimen tal pro gra m

indicated the v i a b i l i t y o f the concept o f l o w - l i f t high-fl ow low-submergence a i r l i f t pumpsfo r urban storm drainage. The Gilbert Roa d proto type syste m suggested sev eral pra cti cal

consi derat ion s for full-s cale applica tio

Documents

Air lift. Diseño. ubc_2004-0178[1].pdf