Note: Descriptions are shown in the official language in which they were submitted.
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MULTIPLE STAGE DRAG AND DYNAMIC TURBIN~ DOWNHOLE MOTOR
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to a multiple stage
turbine for use as a downhole motor on a drilling string, and
more particularly, to a multiple stage turbine downhole motor
which is driven by the drag or shear stress force alone or in
combination with the dynamic or impulse force of the fluid
flowing through the turbine.
De~oription of the Prior Art
Prior art downhole motors for use on drilling strings
convert the kineti¢ energy of a mass of a fluid against the face
surface of turbine blades into power for turning a drill string
and thereby a drill bit attached to the bottom of the drill
string. The turbines rely solely on the dynamic or impulse
force. Prior art downhole motors of this type are generally
required to be relatively long in order to have 6ufficient
turbine blade surface area for generating enough power to turn
the bit at the proper speed with sufficient torque. However,
because the downhole motor itself i5 quite long, it i8 difficult
for the drill string to move through curves and thus it i5 much
more difficult to control the direction of drilling.
Another disadvantage of the dynamic force type
downhole motors, is that maximum power and efficiency occur at
rather high rotational speed ; higher than the range of
operational speed for most mechanical drill bits, like tricone
bits. The reason for this characteristic is that the functions
of power and efficiency, in terms of the velocity of the flow
is proportional to the square of the velocity. The function i5
a parabola in which the apex i~ approximately midway between
zero and runaway or no load speed. -
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Still another disadvantage of prior a~t downhole
turbine motors is that the turbine blades are internal with
respect to the drilling shaft. In order to drive the turbine,
fluid must flow through the internal structure of the drill
string and can cause damage to the bearings, seals and other
internal parts of the downhole motor.
SUMMARY OF THE INVENTION
A helical multiple impulse hydraulic downhole motor
i~ described in my prior U. S. patent application Serial No.
045,822, filed May 4, 1987, now abandoned. This appllcation is
incorporated herein by reference.
It is the primary ob;ect of the present invention to
provide a multiple stage turbine which operates by using the
shear force o~ the ~luid on the edges of the blades of the
turbine either alone or in combination with the impulse force
of the fluid on the surface of the blades.
It i8 another ob~ect of the present invention to
provide a downhole motor for use in turning a drilling string,
and thereby a drill bit on the end of the drill string, which
operates at a relatively 810w speed of 300 - 500 rpm and
produces high torque, with no torque on the plpe of the drill
string itself.
It i8 another object of the present invention to
provide a multiple stage turbine in which the xotor having the
turbine blades, is external to the drilling sha~t and thus the
moviny parts are external to the drilling shaft. Further,
because the blades are attached to an external movable part, the
generated ~orces are farther away from the axis of the turbine,
giving more leverage and hence more torque.
The present invention ~s directed to a multistage
turbine for driving a downhole motor, which is driven by the
flow of a fluid therethrough. The turbine comprises a housing
with a plurality of rims and a shaft positioned in the housing,
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the housing and rims rotating about the longitudinal axis
thereof. A plurality of turbine stages are mounted on the
housing for rotation therewith, each turbine stage including a
rim coaxial with the shaft and a plurality of turbine blades
fixed to each rim. A plurality of flow directing stator~ are
positioned between ad~acent turblne stages, each of the stators
having a wall portion and diverter portion, wherein the wall
portions are perpendicular to the axis of the shaft and the
diverter portions are at an angle of less than 90- with respect
to the axis of the ihaft. At lea3t three of the turbine blades
and the diverter portions form a ~ieal for preventing the flow
from passing therebetween, such that flow through a turbine
stage i8 perpendicular to the axis of the shaft in the space
between adjacent wall portions and wherein the diverter portions
are positioned with respect to said wall means for diverting
flow from the turbine stage to an ad~acent turbine stage.
The turbine blades are positioned between adjacent
stators such that flow between the wall portion of adjacent
sta~ors contacts the edges of the turbine blades, thereby
imparting a drag force on the turbine blades and flow through
ad~acent diverter portions impinges upon the face surface of the
turbine blades, thereby imparting a dynamic force on the turbine
blades ! whereby the turbine blades are rotated by the
combination of the drag forces and dynamia forces thereon.
B~ DESCRT~ION OF TH~ PRAWIN~
Figure l is a sectional view of a downhole motor of
the present invention.
Figure la is an expanded view of a portion of Figure
l.
Figure lb is a sectional view through Section lb-lb
in Figures 1 and la.
Figure 2 i6 a perspective view of the flow through a
turbine of the present invention.
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Figures 3a and 3b are diagrams for analyzing the flow
and forces in a turbine of the present invention.
Figure 4 is a partial sectional view of a turbine of
a first embodlment of the present invention.
Figure 5 i~ a perspective view of a rotor stage of the
present invention.
Figure 6 is a front view of the rotor stage of Figure
5.
Figure 7 is a perspective view of a stator of the
fir~t embodiment of the present invention.
Figure 8 is a perspective view of an alternate
embodiment of a stator of the pre~ent invention.
Figure 9 is a partial layout illustrating the flow of
fluld through a first embodiment of the turblne of the present
invention.
Figure 10 i3 a partial layout illustratlng the flow
of fluid through a second embodiment of the turbine of the
present invention.
Figure 11 is a partial sectional view of a turblne of
a second embodiment of the pres~nt invention.
Figure 12 is a perspective view of the stator of the
~econd embodiment of the present invantion.
Figure 13 i8 a front view of the stator of Figure 12.
Figure 14 is a bottom view of the stator of Figure 12.
Figure 15 is a partia~ layout illustrating the flow
o~ fluid through a third embodiment of the turbine of the
pre~ent invention.
Figure 16 is a partlal layout illustrating the flow
of ~luid through a fourth embodiment of the turblne of the
present inventlon.
Figure 17a iB a partial sectional view of a fifth
embodiment of the turbine of the present invention.
Figure 17b is a partial sectional view of Section 17A-
17A' of Figure 17a.
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Figure 17c i8 a sectional view of Section 17B-17~' of
Figure 17b.
Figure 17d is a perspective view of the turbine rotor
of the fifth embodiment of the present invention.
Figures 18a and 18b are partial layouts illustrating
the intermediate seal for the drag and dynamic embodiment of the
present invention.
DETAILED DE5CRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a multiple stage
turbine which comprises a plurality of single stages, each of
which operates on the principle of the shear stre~s of fluid
flowing in passages or spaces in the stage against the edges of
the turbine blades which generate drag forces either alone or
in combination with impulse forces of the fluid against the
surface of the blades. The volume of ~low is not a factor as
to the drag force or the shear forces on the edges o~ the
turbine blades. The power produced by the drag force i8 a
function of the relative velocity and drag surface, the drag
surface being the edges of the turbine blades, and not the
surface or face of the blade itself. The use of the drag force
results in a higher torque then a conventional turbine rotor of
the same dimensions. This enables the motor of the present
invention to generate sufficient torque using less stages, which
ln turn enables it to be shorter in length than a conventional
turbine motor.
Figure 1 i6 an elevational view o~ a downhole motor
1 which comprises an outer casing 3 and an inner shaft 5. The
motor further includeR a bearing assembly 7 and a turbine
a3sembly 9 having a plurality of stages, each stage having a
stator and rotor assembly. Each stator assembly comprises a
plurality of flow directing stators 11 and each rotor assembly
comprises a plurality of turbine blades 13 which are fixed to
a rotor rim 15.
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A plurallty of turbine rotors 13 are pre-loaded and
held together by means o~ nuts 28 and 29 located at the ends of
the downhole motor. A drill bit (not shown) may be connected
to nut 28. These nuts also hold the bearing assembly 7 in
place. The bearings 7 may be tapered journal bearings or other
types of bearings such as ball bearings. If necessary, nuts for
holding the assembly together can be used as intermediate
portions of the motor. Block 31 provides separation between the
bearlng assembly 7 and the turbine assembly 9 and forms a seal
therebetween. Block 31 can also be used to house a pressure
aompensator for the bearing lubrication system, should such
pres3ure compensation be necessary.
Referring to Figures I, la and lb, fluid, the flow of
which is illustrated by arrows Fl - F7, flows through the
downhole motor 1 as shown. Flow starts at Fl - F3 axially
through the center of shaft 5, between F3 and F4, the fluid
flowe through a plurality of slots 33 in the shaft 5. ~etween
F4 and F5, the fluid flows through the turbine as~embly 9,
rotating the turbine blades 13 and the outer casing 3. End
piece 28 is screw-threaded into outer casing 3 and tightened
against blades 13 to thereby cause the blade 13 to rotate with
the outer casing 3. At F5 - F6, the fluid then flows out of the
turbine assembly 9 and into the Rhaft 5 through additional slots
35, which are the same as slots 33, and then exits from the
downhole motor into the bore hole. As can be seen, the turbine
as~embly is mounted on the outside of the shaft 5, thus, the
moving parts are external to the drill shaft.
Figure 2 shows the flat helical flow path through a
turbine assembly 9. The turbine assembly i8 mounted on a shaft
5. The turbine assembly includes a plurality of flow dire¢ting
stators 11 fixed to the shaft 5, with a plurality of turbine
blades 13 being fixed to the corresponding rotor rim 15 being
positioned to rotate between ad~acent stators 11 ~See Figure 1).
A seal is formed between flow directing portions l9b and l9a and
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the turbine blades 13 so that the flow F is circular in the
channel or space formed between ad~acent stators 11 and then
flows through the channel or space between the flow diverters
17a and 17b and l9a and lsb into an adjacent turbine stage
between the next adjacent stators 11. Thus as can be seen, the
flow follows a ~lat circular path through almost an entire 360-
and then a somewhat helical path diagonally downward into the
next turbine stage. The drag forces and impulse forces applied
to the turbine blades by the flow through the turbine will
depend upon the configuration of the turbine blades 13 and the
stators 11 as will be explained in more detail below.
The turbine of the present invention is driven by the
shear ~tress or drag force in combination with the dynamic or
lmpulse force of the fluid flowing through the turbine. The
drag force is generated by the flow of fluid against thc edges
of the turbine blades. The dynamia for¢e is generated by the
impa¢t of the flow against the surface of the face of the
turbine blades as its flows through the rotor blades at the
entrance and the outlet of each turbine stage.`
The total force acting on the rotor i8:
FT = Fdr ~ Fdy . . . (1)
where:
Fdr = shear force or drag force
Fdy = impulse or dynamic force
The drag force i9 ag follOW8:
Fdr 2 ~ Adr adru(C - u)2/2g . . . (2)
where:
= specific weight of the fluid (Kgf/m3).
Adr = drag coefficient (dimensionless) ~rom
rotor blades and channels geometrical
configuration.
C = mean velocity of the flow through the
drag channels (m/sec).
u = peripheral velocity o~ the rotor (m/sec).
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adr = drag area upon which the shear stress
acts (m).
The dynamic force can be calculated with reference to
Figure 3a which is a section of the rotor blades, transverse to
the axis of rotation wherein: ;
u = tangential velocity of the rotor (m/sec).
wl - relative velooity o~ the flow (m/sec).
~1 = angle of w1 with the direation u (degrees).
C1 - absolute velocity, vectorial addition of
of u and W1.
~1 = angle of c, with the direction of u.
wx1 - component o~ w1 in the direction of movement
The ~ubscript "1" corresponds to the inlet of the flow
for every change of direction through the blade assembly.
20 l~ The subscripts "2" are used to denote the
aorresponding values of the flow at the outlet of every change
of direction, generating a hydraulic impulse.
In order to deduce or obtain the equation for the
dynamic force, referring to Figure 3b, shows the composition of
the triangles of velocities at the inlet and outlet o~ the flow
at every impul~e or change of direction.
According to Newton's Secon~ Law:
Fdy - p Q ~Wxl ~ Wx2)
wherelns
wx1 and WX2 are the components of the relative
veloaltie~ in the direction of the movement.
p - specific mass = y
g
Then:
WX1 = C1 C08~rl u
Wx2 = Cm2 ~ tanP,2 = Cm1 ~ tanfl2. ...
= C1 sin~1 ~ tan~2-
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and
Fdy ~ m p Q[(Clcosal - u) + C1sinul/tan~2] . . (3)
wherein:
m = number of changes of direction or impulses
in each stage.
Referring to Figures 4 - ~, it can be seen that the
blades 13 are fixed to rotor rims 15. Although only four blades
are ~hown, the remaining blades are positioned around the entire
rim 15. When a plurality of rotor assemblies are used as shown
in Figure 1, the rim 15 can have a width equal to the width o~
the turbine blades 13 and a spacer 151 can be positioned
ad~acent to the rim 15. Alternatively, the rim 15 can be made
wider than the blade 13 so that the spacer ~5' is an integral
portion thereof. Figure 6 is an elevation view taken in plane
6-6 of Figure 5 showing the orientation of blades 13 with
respect to rim 15 and the center of rim 15. Although the blades
13 are ~hown in a V-shape cros~-se¢tion, other cross-sectlons
aan be used suoh as a rounded V, offcenter V, a combination of
round and offaentered Vs, etc.
Figure 7 ls a perspective view of a flow directing
stator 11. Stator 11 has wall portions 25 and flow diverting
portions 17a and 17b and l9a and l9b. Flow diverting portions
17a and l9a form seals with ad~acent turbine blades 13, as shown
as ln Figure 2. Although the seal is not a perfect seal ~ince it
is necessary for the turbine blades to rotate, the seal
substantially stops the flow of fluid thereby maintaining the
proper flow path through the turbine assembly as will be
described below. The stator 11 further comprises a hub 21
having a keyway 23 for receiving the key 6 when the stator is
mounted on the sha~t 5. The stator assembly further lncludes
a wall portion 25 integrally formed with the flow directing
portions. As shown in Figure 4, a ~pace 27 is formed between
wall portion 25 and spacer 15'. The space 27 is made very ~mall
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80 that the flow of fluid through the space i8 negligible, but
the space is sufflcient to permit the rotation of rotor 13 with
respect to stator 11.
Figure 8 is an alternative embodiment of the stator
11 in which the hub 21 has a reduced diameter port~on 21a. The
length or angle of the reduced portion will depend upon the
particular flow characteristics but generally will be les~ than
90'. The purpose of the reduced hub radius is to allow the
fluid to flow under the blades 13c, thereby eliminating the
impulse forces on blades 13c and to quickly equalize the flow
on both sides of the blades 13d. If desired, the sharp corners
between surfaces 17a and 17b, and l9a and l9b can be rounded in
order to smooth the flow and reduce turbulence.
Figure 9 is a partial layout illustrating the flow of
fluid through two blade assemblies 13 in a first embodiment of
the turbine of the present invention. The arrows F show the
flow and the arrows D and I illustrate the drag and dynamic
foraes on the turbine blade~ 13. Starting from the right, the
flow F aauses a drag force D on the edges of the turbine blades
13. When the flow reache~ surface 17b, it is diverted downward
as shown, striking the blades 13a and applying a dynamic force
I to the blades 13a. Flow then continues through flow diverters
l9a and l9b into the ad~acent stage of turbine blades and again
dynamic forces I are applied to blades 13a. Flow then continues
towards the left where only drag forces are applied to the edges
of the blades 13.
Figure 10 is a partial layout illustrating the flow
oP fluid through a second embodiment of the turbine of the
present invention in which three impulses are produced in each
stage. The arrows F show the flow and the arrows D and I
illustrate the drag and dynamic on the turbine blades 13.
Starting from the right, the flow F causes a drag force D on
only one edge of the turbine blades 13. In the embodiment of
Figure 8, the turbine blades are configured 80 that the drag
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force is on both edges of the blades. When the flow reaches
surface 17b it is diverted downward, as shown, striking the
blades 13a and applying a dynamic force I to the blades 13a.
The flow then continues through flow diverter~ l9a and l9b into
the ad~acent stage of turbine blades 13 and again dynamic forces
are applied to blades 13a.
In the embodiment of Figure 10, there are three
changes of direction so three impulses are generated in every
stage. In the equation (3), in this case the value of
parameters "m" would be three.
Figures 11 - 15 illustrate a third embodiment of the
turbine of the present invention. In Figure 11, flow directing
stators 111 include diverter portions 117a, and 117b and ll9a
and ll9b and wall portions 125. The turbine blade stages 113
are the same as those described in the embodiment of Figures 4 -
6.
Figure 12 i8 a perspective view of the flow directing
stator 111. The stator 111 comprises a hub 121 with a keyway
123 and a wall portion 125. The wall portion 125 has a
plurality of sections 125a - 125k ~not shown in Figure 12) which
can be seen in Figure 13 which is a full-layout of a plurality
of flow directing stators and turbine blade stages. Figure 13
i8 an elevational view in plane 13-13 of Figure 12, and Figure
14 i3 a side view of Figure 13 in plane 14-14. The surfaces of
diverter portions 117 and wall portions 125 in the correspondin~J
Figures 11 - 15, have been designated by letters A - G.
The flow through the turbine in the embodiment of
Figures 11 - 15 is illustrated by the arrows F in Figure 15.
This flow causes impulse forces on the outer halves 113a of the
turblne blades 113. The inner halves 113b of the turbine blades
113 do not have any significant forces acting thereon, but
rather, act with corresponding diverter wall portions 125a, 125e
and 125i to form a substantial seal therebetween. The seals
ensurs that the flow i3 as indicated by arrows F, rather than
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through the space between the turbine blades and the wall
portions 125a, 12se and 125i. ~he impulse fGrces on the turbine
blades 113a are the same impulse forces described above with
respect to the embodiment of Figures 4 - 9. As can be seen
however, in this embodiment there are no substantial drag forces
on the turbine blades. The lack of substantial drag forces
occurs because centrifugal force on the flow moves the fluid
towards the outside again~t wall portion~ 125c, 125k and 125g
which are away from the edges of the turbine blade~. This
embodiment i8 the limit for the dynamic force, because "m" has
been increased to provide the maximum dynamic force.
Figure 16 shows a fourth embodiment of the turbine of
the present invention. In this embodiment, the blades 213 are
alternately attached to the outside rotor rim (not shown). A
sealing wall members form a seal with one side of blades 213,
and the other side of blades 213 form a seal with stator 211.
Flow i9 in one direction around the annular space and is almost
360' at which point it flows through the outlet into the next
stage. The sinuous path of the flow F produces drag forces D
on the tips or edges of the blades 213 and additionally produces
impulses I on the surface~ of the blades. The drag and dynamic
forces can be calculated in accordance with the equations set
~orth above. However, since the path is not very well defined,
the equations have to be effected by coefficients determined
experimentally.
Instead of blade~, planar or rounded bodies ¢an be
used and attached to the rotor rim to eliminate eddy currents
and turbulence and to enhance impulses on the slanted surfaces
to produce the desired number of smooth changes of direction
along the annular channels.
Figures 17a - 17d illustrate a fifth embodiment of the
turbine of the present invention. In this embodiment, the
turbine is substantially a pure drag turbine which i~ simple,
versatile, has high torque and a comparatively high efficiency.
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Additional turbine blades can be added to produce additional
forces either drag forces or dynamic forces to modify the
performance of the turbine, iP desired.
Referring to Figures 17a - 17d, the flow indicated the
arrow F, flows through the turbine with the intermediate seal
315 at the diagonal entrance of the next stage. The turbine has
blades 313 which contact seals 315. The seal 317a and the
diagonal diverter divert the flow through opening 317 in the
wall of stator 311. The flow channel i~ cylindrical and covers
almost 360~ and is coaxial and parallel with the cylindrical
space covered by the rotor and its blades. In other words, the
flow i8 cylindrical and intermediate between the edges of the
blades and the internal hub, a~ shown in Figure 17c.
The blade length, thickness, angle of inclination, as
well as separation between blades, can be varied. All of these
variables affect the drag coefficient ldr and thus the ultimate
drag foroe, velo¢ity and efficiency.
The drag action in this embodiment of the present
invention i8 generally better than in the other embodiments of
the present invention.
In the fifth embodiment, since the flow through the
ohannels is cylindrical and parallel to the rotor and blades,
the blades do not cross or deviate from the direction of the
flow, to produce an impulse, except in the change of stages.
~he ohange oP direction of the flow from one staqe to the next
is produced by the seal and stator and hence friotion 1088, and
oorrespondingly hydraulio head loss are small.
The following is an explanation of the manner in which
the intermediate seals operate in the present invention.
Considering one stage of the turbine with the drag and dynamic
actions, such as in Figure 18a and 18b, which shows
sohematically a section of the channel with seven changes of
direotion. The rotor i~ shown divided in two portions; one is
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the seal portion in the change of stage, and the other is the
complement portion for the rest of the rotor.
The equilibrium equations for each one of the those
portions are: ~
+ ~ ;
se~l = PlAp + P7Ap - -~Pl - P7)Ap
(seal portion)
P1 and P7 are the pressures at the inlet and outlet of the
stage, and Ap is the area o~ the blades on which the pressures
act.
Fc~ = PlAp-P7Ap + Fdr + Fdy = (Pl-P7)Ap + Fdr + Fdy
(complement portion)
The total force acting on the rotor will be:
FT = ~ Fseal + ~ FC~P
( ~ P7)Ap + (Pl - P7)Ap + Fdr + Fdy
FT ' Fdr + Fdy
Thus, the forces coming from pressure acting on the section
cancel each other.
Although the present invention is shown as a turbine,
the principles o~ the invention can also be used for a pump,
blower or compressor.
The present invention may be embodied in other
speci~ic ~orms without departing from the spirit or essential
oharacteristics thereof. The presently disclosed embodiments
are therefore to ~e considered in all respects as illustrative
and not restrictive, the scope of the invention being indicated
by the appended claims, rather than the foregolng description,
and all changes which come within the meaning and range of
equivalency of the claim3 are, there~ore, to be embraced
therein.
