CA2141455A1 - Pair of conveyor worms for rotary positive-displacement pumps - Google Patents

Abstract

The invention relates to a pair of conveyor worms for rotary positive-displacement pumps, the conveyor worms of which, which are formed as a rotor and counter-rotor, rotate contactlessly in the drilling and the sides at the same speed (worm-drive pump), form loss gaps between them and have the same throat depth and pitch symmetrical flank profiles on each side, made up with respect to their land height of a tooth base beneath the flank profile reversal point (q) and a tooth head thereabove. To provide an improvement it is proposed that the height of the loss gap (c) determined by the profile in the axial section on the pitch circle can be kept constant for a given rotor diameter (DK) by shifting the flank profile reversal point (q) as a function of a technically attainable rotor rise (H).

Description

lf~

Do~cription PAIR OF CONVEYOR WO~S FOR ~OTARY PosITIvE-DIspLAcE~NT
PUMPS

Tho invontio~ rol~te~ to H palr of convcyor ~cre~s for rotsting po-~itive-dieplaceme~t pump~, tho conveyor ~cre~e of which, in tho form of rotor and co~tr~-rotor, rotate co~t~ctl~3 i~ th~ bore ~nd in the fl~ka at the ~mo npeed (Jcr~ opindle pu~pa), form lonJ gapc bot~ecn thom ~nd b~ve the ~sm~ throad dopth~, the ~me number of threads ~nd flcn~ profiloJ ~ich ar~ sy~atrical on both ~ide~ and which ~ith ro~rd to their pitch each conci~t of 8 tooth ~o po~i~ioned bolow thu fl~nk p~ofil~ ro~orcinq point ~d A tooth ~ud po~itionod ~bove thic fl~k profil~ rever~ing po~nt.

With ccro~ ~pi~dl- pu~p~ it i~ kno~n to provide the rot~tin~ conveying elem~ec, c~ rotor8, ~ith ccrow-4haped profil~ which sre ~ubjec~
to tho laws of a goar tooth ayotom, b~t are not used in the firat pl~co to tr~numi~ forco but to seal off the couveyiu~ chamber b~ween tho ouctlon a~d precaure chambors. With the ~o-callod ext~rn~l beqri~g ~cr~ Jpindl~ pump~ th~ rotor~ rot~te cont~ctleffff in the ~ore and iLI
tho flHnkH and aro, thorofore, suitable for pumping non-lubricating, viscou~ madis, whic~ ofte~ co~tai~ P~r~iclos o~ dirt ~nd ~olid~.

Tho volum~tric and the overall efficiency are in~luencod m~i~ly b~ th~
vi~co~lty of thH ConvHying medium snd dotrimontal gapc, whoro~s tho 21 ~1~S5 .~

presaure hoad i~ lnfluorlc~d b~ thc di~t~c- bet~een beari~ga, the la~gth o~ the rotor, the pitch of the rotor, it~ diumetor ~rld tho hub r~t~o NU ~ taoth bQ~e diamet~r ; tooth he~d di~eter).

I~ pri~ciple, ~ith th~ rotoro a d1ffer~tiat1o~ i~ ~ade bat~-o~ the circumfero~tial gap ( thi~ i~ rho gap bet~ffn the rot~r ond the sur-rou~ding rotor boro~, thc ba~o gap ~ t~iJ io the gap betweon tho out-~ld~ di~otor of the on~ rotor ~nd the root circle di~ter of thq oth~r roto~) and th~ gap~ betwe~ th~ flunk profile~ of the rotors ~han tho rotorff ~sh. With rc~ard to the flank gap ~ dif f~rcntiation ln m~do bet~oen a gap that mu~t b~ pre-~et f~r the r~quirod coutac~-froo runni~g And a profil- dope~dont g~p th~t occur~ du~ to th~ l~w.q o~ ~ ~eQr tooth uy~tem. T~is prof ilc d-pe~dent lo~ g~p formb the ~ubj~ct of th~ pre~c~t i~vention.

lf ~t~ non-lubrlcatlng m~iA to be conveyed COIIt~ Y~ p~rt1cleY.

tho ref lux th~t OCCUrD due to tho counter-pre~ure c~u~e~ t wo~r th~ough ~11 pl~ys; a~ a rcrult thoreof the pluys bec~e greater ~o th~t ~lr~dy nftor ~ briof opersti~g period the cffective conveying f10w ie rcducod. In pr~cticc thia pro~lcm i8 counter~cted either by sa~r~l cloced ch~bero of th~ rotor ~rr~ng~d bohin~ o~o anothor, l.o~
by i~crea~ng ~ho ~u~bcr of ch~ber~, or by ~ ~if~erent ~pe~d o the contr~-rotar The fir-t oolution cau~e~ ~ le~th~i~y of th~ rocor ~nd ccordingl~ a Lar~o al~tance bet~een b~rlng~ ~nd a limit~ion of cho convoying pr~snure due to th~ groa~cr d~1ection. Wlth t~e ~econd ~o-1ution ltor~iY~ t~c rotors hsvc ~ d1ffcrer~t numb~r of thre~da ~d ~ccordingly diffcr~nt ou~cdo, duo to which ohortenod filli~g tlme~ and

2 i ~l~5~
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oopoci~lly ~ith hiqh~r vlscooitieo 8 comploto filling of tho ch~mber aro provonted. A furthcr dio~dv~t~g~ ia th~t when tho onc rotor h~
mor~ threads th~ 8m~1108t po~ible rotor pitch i~ alw~y~ gre~ter th~
wieh rotor pair~ ~ith the a~e nu~ber of thro~ds, a~ other~ise tho ~ooth thickne~ or thrcad thick~ess would ~ecom~ too small . Thi~ dic-~dv~n~a~e ~l~o cauJ~ ~ li~it~tlon of tho ~uction hoad.

It i~ tho objoct of the i~vo~tion to de~olop ~ p~ir of convoyor ~crewc of tho type d~cribad ~t the out~ot with a shor~ roter lan~th nr~d ~ corroopondin~ly cm~ll di~t~nce batweon boarirlg oupports, wi~h a low number of stag~s, a large tooth head width, emull rotor pitch and a ~mH11 circumfersnti~1 ~ap leugth, to chus cronto a ocr~ ~pin~La pump wit~ a rel~tivoly l~r~ co~v~ylng flow a~d a high con~eying pre~ur~, uBing a limitod ~ount of ~teri~l. .

~cc~rding co tho invantion thi~ obj~ct io ~chio~od in ch~c thc prof ile~-r~lat~d loc~ qQp h~ight in the axir ~ction o~ the ~itch clrcle 1~ kept conot~nt for n ~pociflc ro~or ~l~ocor by ohifting th~ flank profile revor~ing point ~ a functio~ of a tochnically cxocu~ble rotor pt~ch.

I~ this co~rl~ction it i~ exPcdio~t whc~ the fLank profil~ rc~Ar~ing point climbs ir~ the raeio of rotor diameter to rotor pitch, ~n~ wt~en c~
fl~nk profile rever~ poi~t ~it~i~ the eeries, which i~ ch~ractoriz~d by the rQtiO ba~e dia~ctcr : ho~d diametsr = N~ the rotor pitch d~cres~s climb~ to ~bovn t~e pitch circle radiu~ up to a value of m~xi~u~ r=l.

2141~55 .

....

It i~ fur~hcrmora ndva~tageou~ ~hen the clim~ o ~he fl~nk profile r~vorHi~g poiut comm~c~ from ~ ~inimum value which iu gr~c~r th~n tha pitch circle radiuJ, and ~h~n the profil~-relatod lo~ ~ap h~i~ht in ~h~ ~xi~ ~ection on the pitch circle, which mu~t b~ kept con~t~nt, lie~ i~ the ra~o 0,1% to 1,5~, pre~erAbly 0,1~ to 0,8% of tho rotor diamot0r.

When co~voying liquid~ ~ith ~ high gac cont~t, aftor a ~hort oper~t-ing poriod oft~ ~ hi~h loc~l co~pre~o~ he~t occur~, in p~rticular ou the rotor cooth no~rest the pre~cure gid~. This may cau~o a local circumforential g~p r-duction ~d fi~ally ~ ero~io~ by ~at~ri~l con-t~ct (~rictional o~g~ nt). Accordinq to the invantion ~hi3 problem 1- to be oliminatod 1~ that with multi-otag~ rOtOrH o~ly th~ ~t8~e9 n~ront tho ~uction ~ide have ~ optimum loo~ ~p distrihutior, ~c-cor~i~g to thc in~e~tion ~ ~xplain~d ln tho foregoing. A~ ~ reault theroof, in thc ~xi~1 diraction of the rotor ~l~o g~s i8 compre~ffed i~ido the enl~rgod 108~ g~p volums~; tho occurring co~pro~ion hsa~
i~ ~iatributod over 8 lar~r nurf~c~ of the rotor ~nd can be elimi-~ted mor- favour~bly. Bec~o of ~ a loca~ ov~rh~ting of the tooth ~cnd ia excluded. With theoo ~eaauroo tho pump for co~v~yi~ a liquid ~i~h high q~e co~ten~s of more than 95% C8p for ~h~ ~irst time bo dooigned rcli~bly ~it~ ~n optimum efficioncy. ~ccording to the in-vontiou thie ie ~chiev~d in th~t with tho ~ul tl-~cage rotor ~he fla~k p~ofilc reversing poi~t, up to the ~tage no~re~t the ~uctiou ~ide, ch~n~a continuou~ly, step-by-~t~p or with multiple di~contlnu~i.on~
i~ ~he dircction o~ it~ opti~m po~itio~.

~ 5 5 Thc minimum ~l~nk profil~ rovercinSI point i~ approximataly ~10 of tho pitch circle pluff O, 2 . rhe ex~lct c~lculation takes plHc6 using the formula q.. i n = 0, 6258 x O

According to the inv~r~tion tho di~advh~tago~ ~on~io~od /It thel oueffO~
~ith re~g~rd to the ~tato o~ the ar~ are, thor~fore, i~ pri~cipl~ ~ou~-t~red by tho f ace that ~ h t~c dri~ring an~ drivon rotor, at th~ ~e circ-J~f~re~ti~ p~d, ~he~ profilc~r~lated detrimental gap is split up, ~h~oir~ b~ ~suitablo mo~uro~ ~ho bat~c lc~s~ P, dep~rlding on ~ho pitch, i~ mado up ~o 24 ti~ gr~atbr th~n tho ho~d lo~ g~p. A~ a ros-~lt th~r~of a lo~er l~Q1cage flow flo~s e.locl~ tho tooth hoad, ~o t~at th~
tooth hoad i~ sl~o ~ub~octed to a leso woar. In ~dditior~, ar~ improved volu~ctric efoce io obt~i~od, ~hich improvoJ ~he o~er~ll officie~cy ~nd onouroo 8 lo~qer lifo of tho ~cro~ ~pindle pump.

Wit~ the ~olutio~ ~ccordin~ to ~he i~Vontio~ deccribod abovo ~or ~ul~ a~o rotoro tho poJ~ibi1ity i0 cr~Htod to lot inco~pr~J~ible modia flow b~ck th~ough ~ap~, b~t to compre~ compresnibl~ ~edi~ ovor e lo~qer poch in th~ axi~l diroctlon. Irro~p~ctive of wheth~r ths profile roVOrJing point cli~b~ to ~bovo th~ rotor lo~h, ~ho profilo rovcr~ing point muot ~ y~ havo ite optimu~ at the rotor ~nd o~ tho ~ucti~ sidH

~nd ~u~t climb to~srdo tho rotor o~d on the preosuro ~ide i~ the direc-tio~ of th~ ro~or rndiu~. An ~ ro~ult ther~of the loc~l h~at formatio~
o~ tho prQ~ur~ -oi~e will b~ eli~l~atod ~hrough t~e profilo-r~L~t~d gap ovor the le~t~l of tho rotor. Tho profile-rol~ted gop will, ~hereforo, beco~e am~llor to~rdH ths ouction ~id~. Thi~ m~a~ure, nlso ~ith high ~ 2141~5~

qa~ ratos reoultc in ~ ~hi~ting of the point of ~pplication of the tran~vcru~ forco; it ic 8hif te~ from the preoauro oide middlo to tho Hupporeing beoringo arra~god on tho ruction Pide, duo to which the d~floction o~ tho ah~f~ io r~ducad. Such pu~p~ are suitabl~ ln p~r-ticul~r for convoying crudo oil dir-ctly ~t the boreholo ~horo me~ia l~tcrap~r~od with gn~ C8~ bo ~xpocted (~ulti-ph~se co~veying).

The inventio~ o sxpl~i~od in gr~tor detsil with r feronc~ ~o ~iagrams. With rog~rd to tho aymbols ~d terms which are uoed rof~-r~nc~ do to the ~ovor~iew table".

Figuro 1~ - ~ho~o ~ pl~ne of ~ctio~ i~ face ooction for q_L~;
~iguro 1~ an illu~tr~tion ~ccordinq ~o Figure 1~ for q. . ~;
Figur~ 2 - ~ho~a ~n axial aoction profilo;
Flqur~ 3 - oho~a ~ axial oqction profilo gqp ~ith a compdrisoo for q = 1, q ~ m, ~ = q~n ~t the ~e pitch ~d ~he ~amo dia~ot~r;
Fig~rc 4 - oho~o An axl~ ccion profil~ g~p for q.~ n ~ud q~
F$~uro 5 - illuotra~e~ tho looo ~rea~ 1~ the meHhing zono in foce section o~o~n dim~n~ionloo~ (R~/~K = 1 = r) at th~
tooth h~Qd and tooth b~e over tho profila r~verainq point ~ ith foot/h~ad ratio N~ = 0,4 a~d N~ = 0,65;
Figur~ 6 - io an 8xi81 ~o~tion profile ~ith continuouoly ch~nqin~
profllo production circle;
Figur~ 7 - Jho~ ~c st~to o~ th~ urt in lou~itudinal; soction ~ ffcr~
~pi~dl~ pUmp With ext~r~al bearing~ ~nd , ~ ` 2111455 i~ure ~ - ~ho~ on ~ sm~llor ~c~lo tho Jcreu spindlo pump ~ccor-ding to Figuro 7 in cro~s cactio~.

The ~crew ~piudle pump illu~t~atod in Figur~ 7 a~d 8 h~o ~o co~vey-in~ ~lemonso two contactl~o m~hlng conv~yor screu poirc rot~ti~g in oppo~ito dir~ctions, oach of uhlch compriaeo ~ ri~ht-hs~d thr~ad convoyor ~cre~ ell ~ ft-ha~d thread conveyor ~cre~ 2 . Ac ronule of thic t~o-flo~ arr~ngcment the axial thrust i8 co~peu~at~d.
The ~o~hin~ conveyor scrowc to~ther wlth the euclosi~ houoing 3 for~ i~dividual clo~ed-off convoying ch~mbers. Wh~n roc~ted by drive ~haf~ 4 tho~o ch~m~er~ mov~ co~Si~uou~ly snd p~rall~l to th~
sh~ft~ from the ~uction to th~ prcs~ure side . The diroction of roto-tion of th~ drive ~haft determi~cu the moveme~t arran~s~e~t of the c~v~yi~g chs~berc. Thc pro~Jurc build-up take~ place practically linoarly ovor the length of tho conveyi~g olo~ent~. Tho ~odium th~t fl~a i~ or i8 su~kod up ~hrou~h chc ~uctlon connocclo~ 5 of ~ho pu~p i~ fed i~ the pump houa~ng 6 i~ t~o partial f lows to the two ~uccio~
chamboro.

The torque trencmiooion from the drivin~ ~o thc drivon ~h~ft t~kc~
plac~ ~y ~ toothed-whHHl g~sring 7, the ~etting nf uhic~ e~ures rhe co~t~ct-free runninq of tho conv-ying element~. The r~ference nu~er~l ~ indicatoo ~ otuffing box.

The ~irec~ion of rot~tion of the drive ~h~ft 4 i8 i~dicated ln Figure 7 by ~ha arrow 9. Figure 8 ahows disgr~m~tic~lly the preooure conn~c-tion 10.

21414S~

Wlth ro~ard to the oth~r rQforo~o numerQl~, ploase ro~er to tha ~Overview t~ble~.

According to tho inva~tio~ the conveyor screw flankM ar~ made a~
~traight ~u pos~ibl~, ~volding co~v~x or co~c~vo sh~po~. The aim i~
an ~ ~mall ~ po~siblo proflle d-pe~de~t 10B~ ~ap. The optimum mu~t bo fo~nd bet~eon the t~o extro~o ~aluea q=m ~nd q~l, wherein tho eooth hod r~lated to tho tooth hei~ht muot b~ ~m~ll, tha toath head ~i~th gro~t and tho diot~nce bet~e~n tha me~hing too~h flanks small.
T~o~o requirement~ ~u~ bo mot unl~ormly ov~r a pitch range of the rotor.

At q=l tha tooth hoad hoight ic zero; the tooth h~d ~idth i~ great-e~t with H/2, but tho diAtanco bot~o~n fl~nk~ ell ~9 th~ tooth b~oo lo~ are~ are groat~t~ Wlth a required mi~imal pitch at H
co~ant tooth ~hickneas thl~ is not practic~le. Alroady with ~ Rm~ll cou~tor-preue~re, duo to tho large ba~o gap the roflux lo~e~ ~re very qrest; the of~-ctivo co~veyln~ flow ~ reduced.

At the othor oxtre~e q=m tho tooth heQd iJ gro~te~t wlt~ half tho tooth h~ight, tho tooth head ~idth s~allest; only ~ proflle depeudont ho~d g~p i8 proeent. Up to tho middle of the ~aoth thc di~ance be-t~een fl~nk~ i8 zoro and thon incro~se to ths m~ximum on th~ rotor di~meter. Tho reaction forceu ~r~ greate~t, ~o ~hat o~ muut ~im ~t Qrranglng q a~ ~ar away from this point a~ pos~lbls.

By th~ r.ing up accordinq ~o th~ invention of he~d ~hd hA~e ~ap3, ~141455 t~ g i~to ~ccount the surf~co ~riction ~gt~cn the conv0~0r ~cro~
flankc ~t tho ~e diff~ro~ti~l pro~uro, ospocially with low vi~-co~ity convoying ~edi~ ~n~ tho~ ~ith ~ high ga~ conto~t, tha reflux looa c~n bc ~iqnificarl~ly roduced. ThiJ re~ult~ in an improvomo~t in th- afficioncy 88 ~11 ac ~ lffsser ~et ~e~r.

Iu tha cn~e of ~8 cont~i~ing ~odic, b~ tho moasura according to tha inv~ntion tho occurring comprocsion ho~t i~ ~iotribut~d 1~ a ~peclfic m~nner, thus count-r-acti~g a r~duction of tho circumforen~ial gap qt the tooth h~d ~nd ru~nin~ noie~.

Claims (7)

Claims

1. Pair of conveyor screws for rotating positive-displacement pumps, the conveyor screws of which, in the form of rotor and contrarotor, rotate contactless in the bore and in the flanks at the same speed (screw spindle pumps), form loss gaps between them and have the same thread depths, the same number of threads and flank profiles which are symmetrical on both sides and which with regard to their pitch each consist of a tooth base positioned below the flank profile reversing point (q) and a tooth head positioned above this flank profile reversing point (q), characterized in that the profile-related loss gap height (c) in the axis section on the pitch circle is kept constant for a specific rotor diameter (Dk) by selecting the flank profile reversing point (q) to be a function of a technically executable rotor pitch (H).

2. Pair of conveyor screws according to claim 1, characterized in that the flankprofile reversing point (q) increases in the ratio diameter (Dk) to rotor pitch (H).

3. Pair of conveyor screws according to claim 1 or 2, characterized in that the flank profile reversing point (q) is within a series, which is characterized by the ratio base diameter (DF): head diameter (Dx) - Nü, as the rotor pitch (H) decreases, increasing to above the pitch circle radius (m) up to a value (qxxx) of maximum r = 1.

4. Pair of conveyor screws according to claim 1, 2 or 3, characterized in that the increase of the flank profile reversing point (q) commences from a minimum value which is greater than the pitch circle radius (m).

5. Pair of conveyor screws according to any one of the preceding claims, characterized in that the profile-related loss gap height (c) in the axis section on the pitch circle, is constant, and lies in the range 0,1% to 1,5%, preferably, 0.1% and 0.8% of the rotor diameter (DK).

6. Pair of conveyor screws according to any one of the preceding claims, characterized in that with multi-stage rotors only the stages nearest the suction side have an optimum loss gap distribution according to any one of the preceding claims.

7. Pair of conveyor screws according to claim 6, characterized in that with a multi-stage rotor the flank profile reversing point (q), up to the stage nearestthe suction side, changes continuously, step-by-step or with multiple discontinuations in the direction of its optimum position.