Systems, methods and apparatus for stabilizing a downhole tool and fluid flow
A centralizer for stabilizing fluid flow through a hollow shaft has a body with an axis, an outer surface and a circumference. Fins extend from the outer surface and include a first pair of fins that are axially aligned with each other and circumferentially spaced from each other. A second pair of fins are axially spaced a first distance from the first pair of fins. The second pair of fins are axially aligned with each other and circumferentially spaced from each other. The first and second pairs of fins are circumferentially offset from each other.
1. A centralizer for stabilizing fluid flow through a hollow shaft, the centralizer comprising:
a body having an axis and an outer surface with an outer diameter and a circumference;
a plurality of fins extending from the body and comprising:
a first pair of fins that are aligned with each other along the axis and circumferentially spaced apart from each other relative to the axis; and
a second pair of fins that are aligned with each other along the axis and circumferentially spaced apart from each other relative to the axis;
the first pair of fins is axially spaced apart from the second pair of fins by an axial space;
the first and second pairs of fins are circumferentially offset from each other;
a second body is coupled to the body with a tapered transition, and the second body comprises a second outer diameter that is smaller than the outer diameter of the body; and
an additional set of fins extending from the second body, and the additional set of fins are aligned with each other along the axis and circumferentially spaced-apart from each other relative to the axis.
2. The centralizer of claim 1 , wherein the first and second pairs of fins are circumferentially offset from each other by about 90 degrees.
3. The centralizer of claim 1 , wherein the first pair of fins are circumferentially spaced apart from each other by about 180 degrees.
4. The centralizer of claim 3 , wherein the second pair of fins are circumferentially spaced apart from each other by about 180 degrees.
5. The centralizer of claim 1 , wherein each fin has a portion that tapers toward the body to form a blended radius that is concave.
6. The centralizer of claim 5 , wherein:
each fin has an axial length defined between an axial leading edge and an axial trailing edge;
each fin has a circumferential width defined in a circumferential direction; and
the axial leading and trailing edges are not symmetric when viewed in a radial direction.
7. The centralizer of claim 5 , wherein the blended radius circumscribes a perimeter of every fin where every fin intersects the body.
8. The centralizer of claim 1 , wherein the axial space is from a trailing edge of the first pair of fins to a leading edge of the second pair of fins, and the axial space is at least about 1 inch and not greater than about 3 inches.
9. The centralizer of claim 1 wherein each fin, when viewed in a radial direction, comprises a teardrop shape having a fin geometry described by a distance from a foil chord line, leading edge to trailing edge, by the equation:
y
T
=
T
0.2
(
a
0
x
0.5
+
a
1
+
a
2
x
2
+
a
3
x
3
+
a
4
x
4
)
where, a 0 -a 4 are coefficients of a desired shape, and T is a maximum desired fin thickness for a fin of chord length=1.
10. The centralizer of claim 1 wherein each fin, when viewed in a radial direction, comprises a boat-like shape or a Kamm tail profile.
11. The centralizer of claim 1 , wherein the body consists of the first and second pairs of fins, such that the body has no other fins.
12. A centralizer for a downhole tool, the centralizer comprising:
a body having an axis and an outer surface with a circumference;
first and second fins extending radially from the body opposite each other relative to the axis, and the first and second fins are aligned with each other along the axis;
third and fourth fins extending radially from the body and, collectively, the third and fourth fins are axially spaced apart from the first and second fins by an axial space;
each fin has an axial leading edge and an axial trailing edge that are not symmetric when viewed in a radial direction; and
the body consists of the first, second, third and fourth fins, such that the body has no other fins; and wherein
each fin, when viewed in a radial direction, comprises a teardrop shape having a fin geometry described by a distance from a foil chord line, leading edge to trailing edge, by the equation:
y
T
=
T
0.2
(
a
0
x
0.5
+
a
1
+
a
2
x
2
+
a
3
x
3
+
a
4
x
4
)
where, a 0 -a 4 are coefficients of a desired shape, and T is a maximum desired fin thickness for a fin of chord length=1.
13. The centralizer of claim 12 , wherein:
the first and second fins are circumferentially spaced apart from each other by about 180 degrees;
the third and fourth fins are circumferentially spaced apart from each other by about 180 degrees; and
the first and second fins are circumferentially offset from the third and fourth fins by about 90 degrees.
14. The centralizer of claim 12 , wherein each fin has a portion that tapers toward the body to form a blended radius that is concave.
15. The centralizer of claim 12 , wherein the axial space is from the axial trailing edge of the first or second fin to the axial leading edge of the third or fourth fin, and the axial space is at least about 1 inch and not greater than about 3 inches.
16. The centralizer of claim 12 wherein each fin, when viewed in a radial direction, comprises a boat-like shape or a Kamm tail profile.
17. The centralizer of claim 12 , wherein the body has an outer diameter, a second body is coupled to the body with a tapered transition, and the second body comprises a second outer diameter that is smaller than the outer diameter of the body.
18. The centralizer of claim 14 , wherein the blended radius circumscribes a perimeter of every fin where every fin intersects the body.