CA1250828A - Downhole screw motor - Google Patents
Downhole screw motorInfo
- Publication number
- CA1250828A CA1250828A CA000501759A CA501759A CA1250828A CA 1250828 A CA1250828 A CA 1250828A CA 000501759 A CA000501759 A CA 000501759A CA 501759 A CA501759 A CA 501759A CA 1250828 A CA1250828 A CA 1250828A
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- CA
- Canada
- Prior art keywords
- chamber
- bushing
- nozzle
- flow
- screw motor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
DOWNHOLE SCREW MOTOR
Abstract A downhole screw motor is designed for drilling oil and gas wells.
A downhole screw motor has a stator and a hollow rotor having an axial passage in which is mounted a flow regulat-or having a nozzle. The surface of the nozzle washed with working liquid is made up of two chambers disposed in series in the flow direction: an admission chamber and a delivery chamber, the surfaces of the chambers being conjugated along a break line. A portion of the admission chamber, which is adjacent to the break line, is convex with respect to the direction of flow of working liquid, and the cross-sectional area of the admission chamber at the outlet thereof is smal-ler than the cross-sectional area of the same chamber at the inlet thereof.
Abstract A downhole screw motor is designed for drilling oil and gas wells.
A downhole screw motor has a stator and a hollow rotor having an axial passage in which is mounted a flow regulat-or having a nozzle. The surface of the nozzle washed with working liquid is made up of two chambers disposed in series in the flow direction: an admission chamber and a delivery chamber, the surfaces of the chambers being conjugated along a break line. A portion of the admission chamber, which is adjacent to the break line, is convex with respect to the direction of flow of working liquid, and the cross-sectional area of the admission chamber at the outlet thereof is smal-ler than the cross-sectional area of the same chamber at the inlet thereof.
Description
~2~
DO;,I~OI~ SCRE~ M~TOR
The invention relates to positive displacement hydrau-lic machine~, and in particular, it deal~ with a downhole screw motor~
The invention may be most ef~iciently used in positive-displacement downhole motors used a~ a drive for a rock-~brea~ing tool in drilling oil and ga~ wells.
The inven-tion may al~o be u3ed in turbodrills.
Two radically different methods are used nowadays for drilling wells. ~ne method i8 a rotary drilling method,whe-rein the drive of a rock-breaking-tool - bit - is di~po~ed on the ground level, and the bit is rotated through a strin~
of drill pipes. l'he ~econd method involves the employment of downhole hydraulic machines dispo~ed directly above the bit.
The drill pipe string remain~ stationary in this case. The ~econd method ha~ a number of ObViOUB advantages: there are no energy lo6ses for rotating the drill pipe string; the lo-ad on the drill pipes is lowered, hence, the number of emer-gency situations in the well ~haft i~ reduced.
Downhole screw motors are most wide~pread u~ed amcng all types of àownhole motor~ employed nowadays in practical drilling applications. These motor~ feature ea~y operation and maintenance they are compact and make it pos~ible to work ~ith drilling muds of largely varying density and ViB-cosity (cf. Gusman M.'l'l, Baldenko D.F., et al. Downhole Screw Motors for ~ell Drilling. ~ edra Publishing l~ouse 7 198l)o ~uch hydraulic motors generally compri~e a ca~ing, an output shaft having radial and thrust bearings1 and working members
DO;,I~OI~ SCRE~ M~TOR
The invention relates to positive displacement hydrau-lic machine~, and in particular, it deal~ with a downhole screw motor~
The invention may be most ef~iciently used in positive-displacement downhole motors used a~ a drive for a rock-~brea~ing tool in drilling oil and ga~ wells.
The inven-tion may al~o be u3ed in turbodrills.
Two radically different methods are used nowadays for drilling wells. ~ne method i8 a rotary drilling method,whe-rein the drive of a rock-breaking-tool - bit - is di~po~ed on the ground level, and the bit is rotated through a strin~
of drill pipes. l'he ~econd method involves the employment of downhole hydraulic machines dispo~ed directly above the bit.
The drill pipe string remain~ stationary in this case. The ~econd method ha~ a number of ObViOUB advantages: there are no energy lo6ses for rotating the drill pipe string; the lo-ad on the drill pipes is lowered, hence, the number of emer-gency situations in the well ~haft i~ reduced.
Downhole screw motors are most wide~pread u~ed amcng all types of àownhole motor~ employed nowadays in practical drilling applications. These motor~ feature ea~y operation and maintenance they are compact and make it pos~ible to work ~ith drilling muds of largely varying density and ViB-cosity (cf. Gusman M.'l'l, Baldenko D.F., et al. Downhole Screw Motors for ~ell Drilling. ~ edra Publishing l~ouse 7 198l)o ~uch hydraulic motors generally compri~e a ca~ing, an output shaft having radial and thrust bearings1 and working members
- 2 ~
consistin~ of two elements: an outer rubberized ~leeve or stator having in~ernal helical teeth and a rotor and shaft havin~ outer helical teeth accommodated in the stator. The number of tee-th of the sleeve is greater than the number of teeth of the shaft by unity ~o that the interior of the work-ing members is divided into high and lo~ pressure chambers by their mutual engagerrlent when a liquid is pumped through the working members. Under the action of the resultant pres-sure diff'erence, the rotor starts moving relative to the sta-tor, the a~is of the rotor describing a circle about the ax-is of the stator. 'l'his rotation is tran~mitted to the output shaft of the rotor. Usually a flow of liquid is used as a source of energy for operation of the motor, but the hydrau-lic motor can also f'unction using an aerated li~uid or com-prèssed air.
l~owadays aow~hole motors used for drilling ~ells gene-rally have the whole flow of` liquid passing between the ro-tor and stator.
- One of the main di~advantages of such motors is the dependence of their output parameters on -the inlet flow of workin~ liquid. A9 the production requirements in drilling well~ do not frequently take into account energy capabilities of dov~nhole motors, the latter are often used under unfavour able conditions when speed and pressure differences are too high thus resulting in premature f`ailure of parts and a~serab-lies of the motor.
To elirninate this disadvantage, conoid nozzles are mo unted in the axial passage of the rotor (cf. USSR Inventor's
consistin~ of two elements: an outer rubberized ~leeve or stator having in~ernal helical teeth and a rotor and shaft havin~ outer helical teeth accommodated in the stator. The number of tee-th of the sleeve is greater than the number of teeth of the shaft by unity ~o that the interior of the work-ing members is divided into high and lo~ pressure chambers by their mutual engagerrlent when a liquid is pumped through the working members. Under the action of the resultant pres-sure diff'erence, the rotor starts moving relative to the sta-tor, the a~is of the rotor describing a circle about the ax-is of the stator. 'l'his rotation is tran~mitted to the output shaft of the rotor. Usually a flow of liquid is used as a source of energy for operation of the motor, but the hydrau-lic motor can also f'unction using an aerated li~uid or com-prèssed air.
l~owadays aow~hole motors used for drilling ~ells gene-rally have the whole flow of` liquid passing between the ro-tor and stator.
- One of the main di~advantages of such motors is the dependence of their output parameters on -the inlet flow of workin~ liquid. A9 the production requirements in drilling well~ do not frequently take into account energy capabilities of dov~nhole motors, the latter are often used under unfavour able conditions when speed and pressure differences are too high thus resulting in premature f`ailure of parts and a~serab-lies of the motor.
To elirninate this disadvantage, conoid nozzles are mo unted in the axial passage of the rotor (cf. USSR Inventor's
3 ~ 2~
Certificate lio. 436595~ Clo E 21 B 4/0~, 1972), the flow of working liquid being throttled through the nozzles.
The characteristic of such motore i~ dropping, i.e.
the output shaft speed decrease~ with a growth of the load torque much fa~ter than in hydraulic motors that do not have such nozzles. As the load increases, thi~ result~ in a strong 6peed decrease until the output motor ~haft stops at low load torque values thus resulting in a lower output torque,hence, in a lower efficiency of drilling.
It i9 an object of the invention to improve efficiency of drilling.
Another object of the invention is to improve characte~
ristics of the motor having a nozzle provided in the a~ial passage of the rotor.
Finally, it is an object of the invention to increase the output ~orking torque of a motor having a nozzle in the axial passage of the rotor.
These and other object~ are accompli~hed by that in a downhole motor comprising a ~pindle section and a motor sec-tion comprising working mernbers - a stator and a hollow ro-tor having an axial paseage communicating with a ~orkin~
liquid high-pressure zone and accommodating a flow regulat-or having a nozzle, according to the invention, the nozzle has two chamber~ dieposed in series in the direction of work-ing liquid flow: an admission chamber and a delivery c.hamber, the sur~ace~ o~ the chambers washed with the working liquid being conjugated along a break line, the a~mular portion of the admission chamber~ which is adjMcent to the break-line, being convex with respect to the direction of working liqui~
flo~J, and the cro~s-eectional area of the ~dmiesio~ chsmber at the outlet thereof being smaller than the cro~ss-section~
al area thereof at the inlet.
The invention makes it po~sible to increase torque and speed of the output motor shaft thereby improving efficiency of well drilling. When ~orking liquid enters the nozzle,jete ~tall at the break line to form a powerful vortex in the ad-mission chamber, the vortex energy increa~ing as the pres-~ure difference increases so as to reeult in an increaee in the hydraulic resistance of the nozzle and causing an in-creaee in the flo~ of liquid pa~ing between the rotor and stator.
~ he regulator according to the invention is very com-pact; it can be easily in~talled in any motor and may be re-placed without di~a0sembly of the hydraulic motor.
1~ one embodiment of the inventio~, the nozzle i~ made--up of t~o member~; a buehing and a rod mounted ineide the bushing, the admiesiQn and delivery chamber~ being defi~ed by the surfacee of the bushing and rod and are annular in shape.
In another embodiment, the rod ie cylindrical,and the bushing is internally provided with an annular projectio~ de-fining -the convex portion of the admission chamber surface~
In ~till another embodiment of the invention, the bu~h-ing i~ cylindrical7 and the rod i8 provided with an annular projection defining the convex portion of the admiesion chamber surface.
_ 5 _ ~ ~5 ~
In a further embodim~nt of the inventiorl, the bushin and rod have annular proàections, each projection defining a convex portion of the admission chamber surface.
All embodimentE of the invention make it possible to improYe s~ability of~the motor characteristiG, i~e. to di-minish the dependence of ~peed on the load at the output shaft. This is achieved because liquid jets flowing along the curvilinear surface of the admission chamber stall at the break-line to form a ~pace with an intensive vortical flowO The higher the pressure diff`erence at the working memb-ers (rotor and stator)~ hence at the nozzle, the more in-teIlBiVe i8 mi~ing of liquid jets, the higher is the resist-ance of the nozzle ~nd the greater i8 the amount of liquid that passes through the wor~ing members of the motor. This facility make~ it possible to cau~e a greater amount of li-quid to pass through the helical surfaces of the rotor and stator than in case conoid nozzles are used.
This result, i.e. an increa~e in the flow of liquid through the helical 3urfaces of the rotor and stator upon an increase in the load at the output shaft, can also be obtained using other structural mean~; however, the general idea of the invention will remain unchanged.
In order to lower ~pecific load at the nozzle, several nozzles are preferably provided in the ~xial passage of the rotor. ~peration of the apparatu~ as a whole will in such case remain the same.
Other objects and advanta~es of the invention will be come apparent from the following detailed description of spe-~so~æ~
cific embodiments illustrated in the accompanying drawings,in which:
~ ig. 1 is e lon~itudinal section view of a downhole screw motor having one embodiment o~ a nozzle of a regulat~
or mounted in the axial passage of the rotor;
Fig. 2 i8 a longitudi~al ~ection of a ~low regulator with a nozzle; enlarged Yiew;
Fig. 3 i~ a diagram showing flows of` liquid passing through the noz~le;
Figs. 4,5, 6 show various structural embodiments of nozzles;
~ ig5. 7, 8 show experi~entally obtaine~ energy charac-teristics for prior art and this invention.
A downhole screw motor (~ig. 1) comprises a motor sec-tion 1 and a spindle section 2. 'l'he motor section 1 includes working members: a stator 3 and a hollow rotor 4 mounted therein. The rotor 4 has an a~ial passage 5 communicating with a high-pressure zone of liquid, and a flow regulator 6 is mounted in this axial passage. The rotor 4 is connected, in the lower part thereof`, to a cardan shaft 7 whichg in turn, is connected to an out~ut shaft 8 of -the spindle sec-tion 2. A radial bearin~ 9 and a thrust bearing 10 secured to the shaft 8 are installed in a casin~ 11 of the spindle section ~, between a nipple 12 and a stab sub 13. A sub 14 is provided in the upper part of the mOtor f`or connectin~
to a drill pipe string. A rock breaking tool (not shown in the drawing) is connected to the lower part of` the out-put shaft 8.
- 7 - ~ ~5 ~
The flow regulator 6 (~ig. 2) comprise~ a removable casin~ 15 in which there is mounted a nozzle 16 made e.g.
of a ceramic material. Sealing ring~ 17 and 1~, e.g., of rubber are provided between the casing 15 and rotor 4 and also between the nozzle 16 and ca~ing 15.
~ 'he nozæle 16 i~ made-up of two chambers disposed in ~e-ries in th~ direction of the flow of workin~ liquid; an ad-~ission chamber A and a delivery chamber B~ Surfaces 19 and 20 of the admi~sion chamber A and delivery chamber B, respec-tively, are conjugated along a break line 21. An annular por-tion 22 of the ad~i~sion charnber A, which iB adjacent to the break line 21, is convex with re~pect to the direction of flow of working liquid. ~iameter ~ of the inlet section of the chamber A is greater than diameter d of the outlet sec-tion OI the same chamber A. In other words, the cro~s-sec~
tional area of the admis~ion chamber A a-t the inlet thereo~
i9 larger than the cro~-sectional area at the outlet of the sam~ chamber A.
~ he surface 2ù of the delivery chamber B may have any appropriate confi~uration~ ~owever, it i8 preferred that the shape of the chamber B be such a~ to offer maximum po~sible resistance to the flow of ~orking liquid pas~ing through the nozzle 16. 'l'he ~urface 2û OI the chamber B is formed similar-ly to the surface 19 of the chamber A by rota-tin~ a curve about the axi~ û-û convex with respect to the direction of flow of working liquid.
Both curve~ forming the chambers A and B inter~ect each other in the longitudinal ~ection of the nozzle 1~ at a point which is equivalent to a break point. ~uch points forrn the intersection line 21 in space, which iB equivalent to the break line.
The downhole screw motor functions in the following man-ner.
~ ihen the drill pumps uisposed at the ground level are switched on, drilling Mud i~ supplied through a drill pipe string to the working members of the motor section 1 (see ~ig. 1)~ q;he flow i~ divided directly upstream the working members: the main part of the flow will pas~ between the ~ta-tor 3 and rotor 4 to impart motion to the latter; the other9 smaller part of the flow wiil pas~ throu~h the passage 5 of the ro-tor 4 and flow regulator 6 mounted in the passage 5.
Having pas~ed through the working members, both part~ o~ the flow are again forming a ~ingle flow which gets to the face through the inner hole of the shaft 8 in the ~pindle section 2.
q~orque provided in the motor section 1 is transmitted from the rotor 4, via the cardan shaft 7, to the shaft 8 and further to the rock-breaking tool (bit).
'llhe amount of resis-tance torque overcome by the motor depends on cooperation of the bit and the rock being broken.
During operation of the motor, the motor torque, as well as the load or resistance torque 9 undergo changes.
The torque in motOrs oI such a type i~ known to be pro-portional to the pressure difference at the workin~ members (in the working zone of the Motor characteri~tic) at a con-stant flow of a working liquid. A~ the motor resistance tor-g ~ 2~
que created ùurin~ rotation of the bit increa~es, in theprior art motor the amount of liquid passing between the ro-tor and stator decreases proportionally with ~ P, ~herein P
is the pressure difference at the motor. rl'hus the characte-ristic of the motor becomes dropping~ and the speed of the output shaft 8 materially decrease~.
In the motor accordin~ to the invention; the flow of li-quid gettin& -to the admission chamber A (Fi~. 3) mOVeS in a kind of two flows: the main flow along the axis 0-0 of the nozzle 16 moves from the chamber ~ through the outlet secti-on thereof of the diameter d, which i~ formed by the break line 21; the other, peripheral part of the flow washes the surface 19 of the chamber A. At -the break line 21, this pe-ripheral flow 8tall6 and is intensively mixed ~ith the main central flow. 'lhe peripheral flow will be hereinafter re-ferred to as a resis-tance flow.
Therefore, an inten~ive mi~ing of the main flow and re-sistance flow results in a decrea6e in the energy of flow that gets to the chamber B. The greater the pre~sure di~fe-rence at the working members - stator 3 and rotor 4, and res-pectively, at the nozzle 16, the stronger i9 the mixing of liquid flows, the smaller is the amount of liquid flowing from the chamber A to the chamber B, and the greater is the amount of liquid admitted to the working members.
As ~hown in ~i~. 4, the nozzle 16 i:s made-up of two members: a bushing 23 and a cylindrical rod 24 interconnect-ed by bridges 25. Similarly to the abovedescribed structure, the no~zle 16 ha~ two a~nular chambers disposed in ~eries ~20 1 iJ -in the axial direction: the ad~i~rion chamber A anu the de-livery chamber B having their sur~aces 19 and 2~ washed with wor~ing liquidD The chambers A ar.d ~ are defined by the urfaces of the bushing 23 and rod 24.
The ~urface of the bushing 23 is formed by rotatin2 abo-ut the axis 0-~ a curve which is convex with respect to a ge-nerant of a cylinder of a radius R, wherein R is the minimum distance from the axis 0-0 of the nozzle 16 to a line which is equivalent to the break line 21 formed by intersection of the surface 19 of the ch&mber A with the ~urface 20 of the chamber B. In this case, simil2rly to the abovedescribed embodiment of the invention, the surface 20 of the chamber B is ~ormed by rotating a~ arbitrary curve about the axis An annular projection is provided on the in~er surface of the bushing 23 to form the conve~ portion 22 o~ the ad-mis~ion chamber A.
During operation o~ the embodiment of the regulator, the same IeGUlt i9 obtained a9 in the de~ice 3ho~wn in ~ig.3.
The only difference resides in that the resistance f'low mov--ing from the center away from the cylindrical sur~ace of the rod 24 i~ reflected back to the periphery of the admission chamber A to take part again in mixing with the main flow (~econdary mi~ingj.
Fig. 5 show the nozzle 16 also having the buhing 23 and the rod 24 and two chambers: the admis~ion chamber A
and the deliver~ chamber ~. In this embodiment o~ the nozzle 16, the bushing 23 is cylindrical and the rod 24 is made ~Yith ~2~
an annular projection 27 ~ef`ining the convex portion 22 of the surface 1~ of the admiæsion chamber A. rl'he surface of the bushing 23 washed with wor~ing liquid is c~lindrical, and the surface of the rod 24 in the chamber B is defined by rotating about the axis 0-0 a curve which is convex with reæ-pect to a generant of a cylinder of a radiu~ R, wherein R
is the minimum posæible distance from the axis O-V of the nozzle 16 to the line 21 which is equivalent to a breaking line formed by intersection of the areas of the 6urface of the rod 24 (in the chamber A) and surface of the rod 31 (in the chamber B).
Unlike the motor shown in ~ig. 3, here the resistance flow, which mOVeG along a curvilinear surface away from the center of the nozzle towards its periphery, is reflected from the cylinarical ~urface of the bushing 23 towards the center and again, but with a lower energy, and takes part in the mixing with the main ~low.
The nozzle 16 shown in Fig. 6, similarly to the two above-described embodiments, has two members: the bushing 23 and the rod 24 interconnected by bridges 25. The nozzle also has two chambers disposed in series in ~he axial direc-tion: the admission chamber A and the delivery chamber ~ hav-ing their ~urfaces 19,20 washed with working liquid.The bu-shing 23 has an annular projectlon 28 and the rod 24 has an annular projection 29. Each of the projectionæ 28~29 defines the convex portion 22 of the surface 19 o~ the admiæ-sion chamber A. ~he surfaces of the bushing 23 and rod 24 disposed within the chamber A are formed by rotating about ~ ~5 the axis 0-0 curves each of which is convex with respect to a generant of a cylinder of a radius R, wherein R is the minimum possible distance from the axis 0-0 of the nozzle 16 to a respective line ~Ihich is equi~alent to the break line 21.
Operation of this flo~ regulator is distinguished in the fact that here two resistance flows are formed: one which moves along the curvilinear surface of the bushing 23 from the periphery to~7ards the center of the nozzle 16, and the other which moves alon~ the curvilinear sur~ace of the rod ~4 frorr, the center of the nozzle 16 towards the pe-riphery tnereof. 'i'hese flows intersect one another within a ring defined by radii R and R' so as to contribute to a further mixing of liquid flows.
Therefore, in the abovedescribed er.1bodiments of the mo-tor according to the invention~ with the presence of two parallel flows one of which has its own a~iliary resistance flows the energy of the latter increases with an increase in the pressure difference, i.e. as the motor is loaded with an e~ternal torque, the dependence o~ the amount of liquid passing through the working mernbers and aleo through the nozzle 16 on the motor loading conditions i8 of a complicat-ed character. It can be, however, shown that use in the flow regulator of the nozzles con~tructed as described here will rnake the energy characteristic of the motor stable to a gre-ater ex-tent thus bringing about, quite naturally, an increase in its loading capacity and a very srnall decrease in the mo-tOr output shaft speed.
~25sO~J2B
~ igs. 7 and 8 show energy characteristiCs, i.e. rela-tionships between the relative pressure differential values ~P and rotation f requency ~ of the output shaft 8 ~ arld the relative torque value ~, of a prior art scre~ motor and the screw motor according to the invention.
Study of the characteristics given in the drawins sho~s tllat a zone S of stable operation of the motor in Fi~;. 8 is 18~o larger tnan a zone ~; of stable operation of the motor in Fig. 7 in terms OI ~ orque . Speed decrease in the prior art motor is 57~0 f o- the sarne point anci 50iio for the motor according to the invention. II` the speed decrease is consi~ered for both rr,otors with a?plication of one and the same external torque, the difference ~ill be much great- ¦
er. 'l'his is due to the fact that the motor having a flo~v re- ¦
gulator will be supplied upon an increase in the pressure at the working members an increased amount ( 2S compared to the prior art) of liquid each time so that not only -the s ta-bility of the cnaracteristic is improved, but average values o3` workina ~orque and speed are al~o increa~ed.
Certificate lio. 436595~ Clo E 21 B 4/0~, 1972), the flow of working liquid being throttled through the nozzles.
The characteristic of such motore i~ dropping, i.e.
the output shaft speed decrease~ with a growth of the load torque much fa~ter than in hydraulic motors that do not have such nozzles. As the load increases, thi~ result~ in a strong 6peed decrease until the output motor ~haft stops at low load torque values thus resulting in a lower output torque,hence, in a lower efficiency of drilling.
It i9 an object of the invention to improve efficiency of drilling.
Another object of the invention is to improve characte~
ristics of the motor having a nozzle provided in the a~ial passage of the rotor.
Finally, it is an object of the invention to increase the output ~orking torque of a motor having a nozzle in the axial passage of the rotor.
These and other object~ are accompli~hed by that in a downhole motor comprising a ~pindle section and a motor sec-tion comprising working mernbers - a stator and a hollow ro-tor having an axial paseage communicating with a ~orkin~
liquid high-pressure zone and accommodating a flow regulat-or having a nozzle, according to the invention, the nozzle has two chamber~ dieposed in series in the direction of work-ing liquid flow: an admission chamber and a delivery c.hamber, the sur~ace~ o~ the chambers washed with the working liquid being conjugated along a break line, the a~mular portion of the admission chamber~ which is adjMcent to the break-line, being convex with respect to the direction of working liqui~
flo~J, and the cro~s-eectional area of the ~dmiesio~ chsmber at the outlet thereof being smaller than the cro~ss-section~
al area thereof at the inlet.
The invention makes it po~sible to increase torque and speed of the output motor shaft thereby improving efficiency of well drilling. When ~orking liquid enters the nozzle,jete ~tall at the break line to form a powerful vortex in the ad-mission chamber, the vortex energy increa~ing as the pres-~ure difference increases so as to reeult in an increaee in the hydraulic resistance of the nozzle and causing an in-creaee in the flo~ of liquid pa~ing between the rotor and stator.
~ he regulator according to the invention is very com-pact; it can be easily in~talled in any motor and may be re-placed without di~a0sembly of the hydraulic motor.
1~ one embodiment of the inventio~, the nozzle i~ made--up of t~o member~; a buehing and a rod mounted ineide the bushing, the admiesiQn and delivery chamber~ being defi~ed by the surfacee of the bushing and rod and are annular in shape.
In another embodiment, the rod ie cylindrical,and the bushing is internally provided with an annular projectio~ de-fining -the convex portion of the admission chamber surface~
In ~till another embodiment of the invention, the bu~h-ing i~ cylindrical7 and the rod i8 provided with an annular projection defining the convex portion of the admiesion chamber surface.
_ 5 _ ~ ~5 ~
In a further embodim~nt of the inventiorl, the bushin and rod have annular proàections, each projection defining a convex portion of the admission chamber surface.
All embodimentE of the invention make it possible to improYe s~ability of~the motor characteristiG, i~e. to di-minish the dependence of ~peed on the load at the output shaft. This is achieved because liquid jets flowing along the curvilinear surface of the admission chamber stall at the break-line to form a ~pace with an intensive vortical flowO The higher the pressure diff`erence at the working memb-ers (rotor and stator)~ hence at the nozzle, the more in-teIlBiVe i8 mi~ing of liquid jets, the higher is the resist-ance of the nozzle ~nd the greater i8 the amount of liquid that passes through the wor~ing members of the motor. This facility make~ it possible to cau~e a greater amount of li-quid to pass through the helical surfaces of the rotor and stator than in case conoid nozzles are used.
This result, i.e. an increa~e in the flow of liquid through the helical 3urfaces of the rotor and stator upon an increase in the load at the output shaft, can also be obtained using other structural mean~; however, the general idea of the invention will remain unchanged.
In order to lower ~pecific load at the nozzle, several nozzles are preferably provided in the ~xial passage of the rotor. ~peration of the apparatu~ as a whole will in such case remain the same.
Other objects and advanta~es of the invention will be come apparent from the following detailed description of spe-~so~æ~
cific embodiments illustrated in the accompanying drawings,in which:
~ ig. 1 is e lon~itudinal section view of a downhole screw motor having one embodiment o~ a nozzle of a regulat~
or mounted in the axial passage of the rotor;
Fig. 2 i8 a longitudi~al ~ection of a ~low regulator with a nozzle; enlarged Yiew;
Fig. 3 i~ a diagram showing flows of` liquid passing through the noz~le;
Figs. 4,5, 6 show various structural embodiments of nozzles;
~ ig5. 7, 8 show experi~entally obtaine~ energy charac-teristics for prior art and this invention.
A downhole screw motor (~ig. 1) comprises a motor sec-tion 1 and a spindle section 2. 'l'he motor section 1 includes working members: a stator 3 and a hollow rotor 4 mounted therein. The rotor 4 has an a~ial passage 5 communicating with a high-pressure zone of liquid, and a flow regulator 6 is mounted in this axial passage. The rotor 4 is connected, in the lower part thereof`, to a cardan shaft 7 whichg in turn, is connected to an out~ut shaft 8 of -the spindle sec-tion 2. A radial bearin~ 9 and a thrust bearing 10 secured to the shaft 8 are installed in a casin~ 11 of the spindle section ~, between a nipple 12 and a stab sub 13. A sub 14 is provided in the upper part of the mOtor f`or connectin~
to a drill pipe string. A rock breaking tool (not shown in the drawing) is connected to the lower part of` the out-put shaft 8.
- 7 - ~ ~5 ~
The flow regulator 6 (~ig. 2) comprise~ a removable casin~ 15 in which there is mounted a nozzle 16 made e.g.
of a ceramic material. Sealing ring~ 17 and 1~, e.g., of rubber are provided between the casing 15 and rotor 4 and also between the nozzle 16 and ca~ing 15.
~ 'he nozæle 16 i~ made-up of two chambers disposed in ~e-ries in th~ direction of the flow of workin~ liquid; an ad-~ission chamber A and a delivery chamber B~ Surfaces 19 and 20 of the admi~sion chamber A and delivery chamber B, respec-tively, are conjugated along a break line 21. An annular por-tion 22 of the ad~i~sion charnber A, which iB adjacent to the break line 21, is convex with re~pect to the direction of flow of working liquid. ~iameter ~ of the inlet section of the chamber A is greater than diameter d of the outlet sec-tion OI the same chamber A. In other words, the cro~s-sec~
tional area of the admis~ion chamber A a-t the inlet thereo~
i9 larger than the cro~-sectional area at the outlet of the sam~ chamber A.
~ he surface 2ù of the delivery chamber B may have any appropriate confi~uration~ ~owever, it i8 preferred that the shape of the chamber B be such a~ to offer maximum po~sible resistance to the flow of ~orking liquid pas~ing through the nozzle 16. 'l'he ~urface 2û OI the chamber B is formed similar-ly to the surface 19 of the chamber A by rota-tin~ a curve about the axi~ û-û convex with respect to the direction of flow of working liquid.
Both curve~ forming the chambers A and B inter~ect each other in the longitudinal ~ection of the nozzle 1~ at a point which is equivalent to a break point. ~uch points forrn the intersection line 21 in space, which iB equivalent to the break line.
The downhole screw motor functions in the following man-ner.
~ ihen the drill pumps uisposed at the ground level are switched on, drilling Mud i~ supplied through a drill pipe string to the working members of the motor section 1 (see ~ig. 1)~ q;he flow i~ divided directly upstream the working members: the main part of the flow will pas~ between the ~ta-tor 3 and rotor 4 to impart motion to the latter; the other9 smaller part of the flow wiil pas~ throu~h the passage 5 of the ro-tor 4 and flow regulator 6 mounted in the passage 5.
Having pas~ed through the working members, both part~ o~ the flow are again forming a ~ingle flow which gets to the face through the inner hole of the shaft 8 in the ~pindle section 2.
q~orque provided in the motor section 1 is transmitted from the rotor 4, via the cardan shaft 7, to the shaft 8 and further to the rock-breaking tool (bit).
'llhe amount of resis-tance torque overcome by the motor depends on cooperation of the bit and the rock being broken.
During operation of the motor, the motor torque, as well as the load or resistance torque 9 undergo changes.
The torque in motOrs oI such a type i~ known to be pro-portional to the pressure difference at the workin~ members (in the working zone of the Motor characteri~tic) at a con-stant flow of a working liquid. A~ the motor resistance tor-g ~ 2~
que created ùurin~ rotation of the bit increa~es, in theprior art motor the amount of liquid passing between the ro-tor and stator decreases proportionally with ~ P, ~herein P
is the pressure difference at the motor. rl'hus the characte-ristic of the motor becomes dropping~ and the speed of the output shaft 8 materially decrease~.
In the motor accordin~ to the invention; the flow of li-quid gettin& -to the admission chamber A (Fi~. 3) mOVeS in a kind of two flows: the main flow along the axis 0-0 of the nozzle 16 moves from the chamber ~ through the outlet secti-on thereof of the diameter d, which i~ formed by the break line 21; the other, peripheral part of the flow washes the surface 19 of the chamber A. At -the break line 21, this pe-ripheral flow 8tall6 and is intensively mixed ~ith the main central flow. 'lhe peripheral flow will be hereinafter re-ferred to as a resis-tance flow.
Therefore, an inten~ive mi~ing of the main flow and re-sistance flow results in a decrea6e in the energy of flow that gets to the chamber B. The greater the pre~sure di~fe-rence at the working members - stator 3 and rotor 4, and res-pectively, at the nozzle 16, the stronger i9 the mixing of liquid flows, the smaller is the amount of liquid flowing from the chamber A to the chamber B, and the greater is the amount of liquid admitted to the working members.
As ~hown in ~i~. 4, the nozzle 16 i:s made-up of two members: a bushing 23 and a cylindrical rod 24 interconnect-ed by bridges 25. Similarly to the abovedescribed structure, the no~zle 16 ha~ two a~nular chambers disposed in ~eries ~20 1 iJ -in the axial direction: the ad~i~rion chamber A anu the de-livery chamber B having their sur~aces 19 and 2~ washed with wor~ing liquidD The chambers A ar.d ~ are defined by the urfaces of the bushing 23 and rod 24.
The ~urface of the bushing 23 is formed by rotatin2 abo-ut the axis 0-~ a curve which is convex with respect to a ge-nerant of a cylinder of a radius R, wherein R is the minimum distance from the axis 0-0 of the nozzle 16 to a line which is equivalent to the break line 21 formed by intersection of the surface 19 of the ch&mber A with the ~urface 20 of the chamber B. In this case, simil2rly to the abovedescribed embodiment of the invention, the surface 20 of the chamber B is ~ormed by rotating a~ arbitrary curve about the axis An annular projection is provided on the in~er surface of the bushing 23 to form the conve~ portion 22 o~ the ad-mis~ion chamber A.
During operation o~ the embodiment of the regulator, the same IeGUlt i9 obtained a9 in the de~ice 3ho~wn in ~ig.3.
The only difference resides in that the resistance f'low mov--ing from the center away from the cylindrical sur~ace of the rod 24 i~ reflected back to the periphery of the admission chamber A to take part again in mixing with the main flow (~econdary mi~ingj.
Fig. 5 show the nozzle 16 also having the buhing 23 and the rod 24 and two chambers: the admis~ion chamber A
and the deliver~ chamber ~. In this embodiment o~ the nozzle 16, the bushing 23 is cylindrical and the rod 24 is made ~Yith ~2~
an annular projection 27 ~ef`ining the convex portion 22 of the surface 1~ of the admiæsion chamber A. rl'he surface of the bushing 23 washed with wor~ing liquid is c~lindrical, and the surface of the rod 24 in the chamber B is defined by rotating about the axis 0-0 a curve which is convex with reæ-pect to a generant of a cylinder of a radiu~ R, wherein R
is the minimum posæible distance from the axis O-V of the nozzle 16 to the line 21 which is equivalent to a breaking line formed by intersection of the areas of the 6urface of the rod 24 (in the chamber A) and surface of the rod 31 (in the chamber B).
Unlike the motor shown in ~ig. 3, here the resistance flow, which mOVeG along a curvilinear surface away from the center of the nozzle towards its periphery, is reflected from the cylinarical ~urface of the bushing 23 towards the center and again, but with a lower energy, and takes part in the mixing with the main ~low.
The nozzle 16 shown in Fig. 6, similarly to the two above-described embodiments, has two members: the bushing 23 and the rod 24 interconnected by bridges 25. The nozzle also has two chambers disposed in series in ~he axial direc-tion: the admission chamber A and the delivery chamber ~ hav-ing their ~urfaces 19,20 washed with working liquid.The bu-shing 23 has an annular projectlon 28 and the rod 24 has an annular projection 29. Each of the projectionæ 28~29 defines the convex portion 22 of the surface 19 o~ the admiæ-sion chamber A. ~he surfaces of the bushing 23 and rod 24 disposed within the chamber A are formed by rotating about ~ ~5 the axis 0-0 curves each of which is convex with respect to a generant of a cylinder of a radius R, wherein R is the minimum possible distance from the axis 0-0 of the nozzle 16 to a respective line ~Ihich is equi~alent to the break line 21.
Operation of this flo~ regulator is distinguished in the fact that here two resistance flows are formed: one which moves along the curvilinear surface of the bushing 23 from the periphery to~7ards the center of the nozzle 16, and the other which moves alon~ the curvilinear sur~ace of the rod ~4 frorr, the center of the nozzle 16 towards the pe-riphery tnereof. 'i'hese flows intersect one another within a ring defined by radii R and R' so as to contribute to a further mixing of liquid flows.
Therefore, in the abovedescribed er.1bodiments of the mo-tor according to the invention~ with the presence of two parallel flows one of which has its own a~iliary resistance flows the energy of the latter increases with an increase in the pressure difference, i.e. as the motor is loaded with an e~ternal torque, the dependence o~ the amount of liquid passing through the working mernbers and aleo through the nozzle 16 on the motor loading conditions i8 of a complicat-ed character. It can be, however, shown that use in the flow regulator of the nozzles con~tructed as described here will rnake the energy characteristic of the motor stable to a gre-ater ex-tent thus bringing about, quite naturally, an increase in its loading capacity and a very srnall decrease in the mo-tOr output shaft speed.
~25sO~J2B
~ igs. 7 and 8 show energy characteristiCs, i.e. rela-tionships between the relative pressure differential values ~P and rotation f requency ~ of the output shaft 8 ~ arld the relative torque value ~, of a prior art scre~ motor and the screw motor according to the invention.
Study of the characteristics given in the drawins sho~s tllat a zone S of stable operation of the motor in Fi~;. 8 is 18~o larger tnan a zone ~; of stable operation of the motor in Fig. 7 in terms OI ~ orque . Speed decrease in the prior art motor is 57~0 f o- the sarne point anci 50iio for the motor according to the invention. II` the speed decrease is consi~ered for both rr,otors with a?plication of one and the same external torque, the difference ~ill be much great- ¦
er. 'l'his is due to the fact that the motor having a flo~v re- ¦
gulator will be supplied upon an increase in the pressure at the working members an increased amount ( 2S compared to the prior art) of liquid each time so that not only -the s ta-bility of the cnaracteristic is improved, but average values o3` workina ~orque and speed are al~o increa~ed.
Claims (5)
1. A downhole screw motor, comprising: a motor section and a spindle section mounted coaxially with one another;
a shaft having an axial bearing and a thrust bearing in said spindle section;
working members of said motor section - a stator and a hollow rotor mounted in said motor section; a working liquid flow regulator mounted in said rotor;
a nozzle mounted in said flow regulator;
said nozzle being made-up of two chambers disposed in series in the direction of flow of said working liquid - an admission chamber and a delivery chamber;
the surfaces of said chambers washed with working liqu-id being conjugated along a break line;
a portion of said admission chamber, which is adjacent to said break line, being convex with respect to the direc-tion of flow of working liquid;
the cross-sectional area of said admission chamber at the outlet thereof being smaller than the cross-sectional area of the same chamber at the inlet thereof.
a shaft having an axial bearing and a thrust bearing in said spindle section;
working members of said motor section - a stator and a hollow rotor mounted in said motor section; a working liquid flow regulator mounted in said rotor;
a nozzle mounted in said flow regulator;
said nozzle being made-up of two chambers disposed in series in the direction of flow of said working liquid - an admission chamber and a delivery chamber;
the surfaces of said chambers washed with working liqu-id being conjugated along a break line;
a portion of said admission chamber, which is adjacent to said break line, being convex with respect to the direc-tion of flow of working liquid;
the cross-sectional area of said admission chamber at the outlet thereof being smaller than the cross-sectional area of the same chamber at the inlet thereof.
2. A downhole screw motor according to claim 1, where-in the nozzle is made up of two members: a bushing and a rod mounted inside the bushing, the admission and delivery chamb-ers being defined by the surfaces of the bushing and rod and being annular in shape.
3. A downhole screw motor according to claim 2, where-in the rod is cylindrical and the bushing is internally pro-vided with an annular projection defining the convex portion of the admission chamber.
4. A downhole screw motor according to claim 2, wherein the bushing is cylindrical and the rod has an annular pro-jection defining the convex portion of the surface of the admission chamber.
5. A downhole screw motor according to claim 2, wherein the bushing and rod have annular projections, each project-ion defining the convex portion of the surface of the admis-sion chamber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000501759A CA1250828A (en) | 1986-02-13 | 1986-02-13 | Downhole screw motor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000501759A CA1250828A (en) | 1986-02-13 | 1986-02-13 | Downhole screw motor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1250828A true CA1250828A (en) | 1989-03-07 |
Family
ID=4132467
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000501759A Expired CA1250828A (en) | 1986-02-13 | 1986-02-13 | Downhole screw motor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1250828A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111877979A (en) * | 2020-07-30 | 2020-11-03 | 重庆大学 | Ratchet type hydraulic impactor |
-
1986
- 1986-02-13 CA CA000501759A patent/CA1250828A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111877979A (en) * | 2020-07-30 | 2020-11-03 | 重庆大学 | Ratchet type hydraulic impactor |
| CN111877979B (en) * | 2020-07-30 | 2022-03-29 | 重庆大学 | Ratchet type hydraulic impactor |
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