Reduced flow pulsations in a tandem floating cup pump with an odd number of pistons
A method for reducing the flow pulsations in a tandem floating cup pump having an odd number of pistons includes determining a low noise net index angle that produces reduced flow pulsations relative to those produced when the net index angle is either zero or half the separation angle and offsetting a first rotating group relative to a second rotating group by the low noise net index angle. The net index angle is the sum of a piston index angle and the port plate index angle. The piston index angle is the angle between a piston from a first rotating group and an adjacent piston from a second rotating group whereas the port plate index angle is the angle by which a first port plate is offset relative to a second port plate.
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The present disclosure relates to the field of floating cup pumps and more specifically, to tandem floating cup pumps having an odd number of pistons in each of the two rotating groups.
BACKGROUNDLike all other types of pumps, floating cup pumps generate noise during operation. One source of noise is related to flow pulsations. By reducing the flow pulsations of a floating cup pump, noise related to flow pulsations in the pump may be reduced. It is asserted in the art that flow pulsations in tandem floating cup pumps can be reduced by offsetting one rotating group of pistons with respect to the other rotating group of pistons by a net index angle that is half the separation angle between adjacent pistons. Over the past several years, Dr. Peter Achten has published papers regarding the floating cup pump and improvements related to the floating cup pump concept. In one of his earlier papers, Designing the Impossible Pump, Dr. Achten discusses a twenty-four piston tandem floating cup pump that has an even number of pistons in each rotating group. The paper asserts that the floating cup pump offers higher efficiency, extremely low pulsations and low noise levels. Later, Dr. Achten published another paper titled Reducing Flow Pulsation with the Floating Cup Pump: Theoretical Analysis in which he discusses reducing flow pulsations in the twenty-four piston pump by phase shifting one rotating group of pistons relative to the other by half the separation angle. However, the art has yet to recognize that there might even be a difference between tandem floating cup pumps having an odd number of pistons in each rotating group and tandem floating cup pumps with an even number of pistons in each rotating group. The conventional wisdom appears to suggest that a net index angle of half the separation angle in all tandem floating cup pumps reduces flow pulsations and hence, flow pulsations related noise regardless of the number of pistons in each rotating group. The present disclosure is directed to reducing the flow pulsations and consequently, the noise produced by a tandem floating cup pump having an odd number of pistons in each rotating group.
SUMMARYIn one aspect, a method for reducing flow pulsations in a tandem floating cup pump is described. The floating cup pump includes a first and second rotating group, each having the same odd number of pistons. The pistons being spaced equally apart from adjacent pistons on the same rotating group by a separation angle. The method of reducing flow pulsations includes a step of determining a low noise net index angle that corresponds to reduced flow pulsations in comparison to the flow pulsations produced when the net index angle is zero or half the separation angle. A net index angle between the first rotating group and the second rotating group is set to the low noise net index angle.
In another aspect, a floating cup pump includes a rotor, a first barrel plate and a second barrel plate attached to a shaft. A first rotating group includes a first set of an odd number of floating cups, each being swivelly attached to the first barrel plate. The first rotating group also includes a first set of an odd number of pistons and each piston is equally spaced apart from an adjacent piston by a separation angle. Each piston of the first rotating group has a first end and a second end. The first end of each piston is attached to the rotor and the second end of each piston is received by a respective one of the first set of floating cups. A second rotating group includes a second set of the odd number of floating cups, each being swivelly attached to the second barrel plate. The second rotating group also includes a second set of pistons having the same number of pistons as the first rotating group and each piston is equally spaced apart from an adjacent piston by the separation angle. Each piston of the second rotating group has a first end and a second end. The first end of each piston is attached to the rotor and the second end of each piston is received by a respective one of the second set of floating cups. The first rotating group and the second rotating group have a first relative orientation that defines a piston index angle. A first port plate that is adjacent to the first barrel plate defines a bottom dead center position of the first rotating group. A second port plate adjacent to the second barrel plate defines a bottom dead center position of the second rotating group. The bottom dead center of the first rotating group and the bottom dead center of the second rotating group have a second relative orientation that defines a port plate index angle. A low noise net index angle is the sum of the piston index angle and the port plate index angle and the low noise net index angle is different from the zero and half of the separation angle.
In yet another aspect, a floating cup pump includes a rotor, a first barrel plate and a second barrel plate attached to a shaft. A first rotating group includes a first set of an odd number of floating cups, each being swivelly attached to the first barrel plate. The first rotating group also includes a first set of an odd number of pistons and each piston is equally spaced apart from an adjacent piston by a separation angle. Each piston of the first rotating group has a first end and a second end. The first end of each piston is attached to the rotor and the second end of each piston is received by a respective one of the first set of floating cups. A second rotating group includes a second set of the odd number of floating cups, each being swivelly attached to the second barrel plate. The second rotating group also includes a second set of pistons having the same number of pistons as the first rotating group and each piston is equally spaced apart from an adjacent piston by the separation angle. Each piston of the second rotating group has a first end and a second end. The first end of each piston is attached to the rotor and the second end of each piston is received by a respective one of the second set of floating cups. The first rotating group and the second rotating group have a first relative orientation that defines a piston index angle. A first port plate that is adjacent to the first barrel plate defines a bottom dead center position of the first rotating group. A second port plate adjacent to the second barrel plate defines a bottom dead center position of the second rotating group. The bottom dead center of the first rotating group and the bottom dead center of the second rotating group have a second relative orientation that defines a port plate index angle. A net index angle is the sum of the piston index angle and the port plate index angle. The floating cup pump also includes a means, which includes setting the net index angle to a low noise net index angle that is different from zero and half the separation angle, for reducing noise due to flow pulsations.
The problem of reducing flow pulsations in a tandem floating cup pump may have appeared to be solved. However, what Dr. Achten and others in the art failed to recognize is the behavioral differences between tandem floating pumps having an odd number of pistons and an even number of pistons in each rotating group. Although the art suggests that offsetting the rotating groups by half the separation angle will provide the best results for reducing flow pulsations, and inherently, the noise related to flow pulsations, the art is wrong when applied to floating cup pumps with an odd number of pistons. The present disclosure teaches one in the art, the best net index angles and associated ranges that provide reduced flow pulsations compared to the levels of flow pulsations when the net index angle is zero or half the separation angle.
Referring to
In the tandem floating cup pump 10, the two rotating groups 20 and 50 are structurally and functionally similar and therefore describing the first rotating group 20 shall suffice to understand the structure of the second rotating group 50. The floating cup 31 has an inner cylindrical wall 32, which is in contact with the cup end 25 of the piston 23. A bottom end 34 of the floating cup 31 has a hole 33, which allows a fluid to flow in and out of the first barrel plate 26 through the port plate 40 from an inlet port 48 and to an outlet port 49 (not shown in
Referring in addition to
Referring to
Referring to
Referring to
In an exemplary embodiment, a floating cup pump may have a non-zero piston index angle and a zero port plate index angle or a zero piston index angle and a non-zero port plate index angle. In another embodiment, a pump may have a non-zero piston index angle and a non-zero port plate index angle. A low noise net index angle is a net index angle where the noise produced by the floating cup pump is lower than the flow pulsation related noise produced by the floating cup pump when the net index angle is set to either zero or half the separation angle. A best low noise net index angle is a net index angle where the noise related to flow pulsations is at a minimum level for that given pump. Because noise related to flow pulsations is a function of the number of pistons in the pump and the net index angle of the pump, setting the same net index angles in pumps having different number of pistons will produce different amounts of noise. The following table illustrates a first range of net index angles and a second range of net index angles that will produce lower noise related to flow pulsations than the noise produced at a net index angle of zero or half the separation angle for pumps ranging from five to thirty-five pistons in each rotating group. In the following tables, the N represents the number of pistons in each rotating group:
In an exemplary embodiment, a pump 10 having eleven pistons 23 in each rotating group 20 and 50 may have a low noise net index angle set at any angle from 3.93 degrees to 12.44 degrees and from 20.29 degrees to 28.80 degrees. If the net index angle 93 is set within either of these two ranges, the noise produced by the floating cup pump 10 will be less than the noise produced by the same pump 10 when the net index angle is zero or half the separation angle.
In addition to the low noise net index angles ranges, each pump also has a low best low noise net index angle and a high best low noise net index angle. The following table illustrates the angles producing the least amount of noise related to flow pulsations for pistons having five to thirty-five pistons in each rotating group:
In an exemplary embodiment, a pump 10 having eleven pistons 23 in each rotating group 20 and 50 may have two best low noise net index angles where the noise related to flow pulsations produced by the floating cup pump 10 will be less than the noise produced by the same pump 10 at any other net index angle including the zero index angle and half the separation angle. In a twenty-two piston floating cup pump, the two best angles are about 8.2 degrees and about 25 degrees. The term about means that when a number is rounded to a like number of significant digits, the numbers are equal. Thus both 8.15 and 8.24 are equal to 8.2 and 24.5 and 25.4 are equal to 25.
The two tables explained above serve to teach those skilled in the art that the obvious choices of zero or half the separation angle as the net index angle are not the best angles when trying to reduce the noise generated from flow pulsations in tandem floating cup pumps having an odd number of pistons. Further, the tables described above provide those skilled in the art with ranges of low noise index angles as well as best net index angles to choose from.
INDUSTRIAL APPLICABILITYThe present disclosure finds potential application in any tandem floating cup pump having an odd number of pistons. The present disclosure aims to solve the recently recognized issue of noise related to flow pulsations in tandem floating cup pumps having an odd number of pistons is different from similar pumps with even number of pistons.
A floating cup pump 10 displaces fluid by rotating a shaft 18 that may rotate the rotor 12 and the rotating groups 20 and 50. Because the pistons 23 are attached to the rotor 12, the pistons 23 may rotate along with the shaft 18 and the rotor 12. Consequently, the entire first and second rotating groups 20 and 50 rotate along with the first and second barrel plates 26 and 56 also rotate with the shaft 18 at the same speed. Pistons 23 of the first rotating group 20 and the second rotating group 50 perform similar functions as they rotate about the shaft 18. In one cycle of operation, each piston 23 rotates a full circle around the shaft 18, arriving at the same position that the piston 23 started at. At the end of the full circle, each piston 23 displaces a fixed amount of fluid that is equal in all pistons 23. The manner in which a piston 23 displaces fluid may be explained by discussing an exemplary piston's rotational path in
In the floating cup pump 210 shown in
This disclosure describes a floating cup pump that reduces the noise related to flow pulsations produced by a pump relative to the noise related to flow pulsations produced by a pump that has a zero net index angle or a net index angle of half the separation angle. Further, the disclosure discusses two alternate ways of setting the net index angle including setting a piston index angle via a rotor or setting a port plate index angle by offsetting the port plates relative to each other. The disclosure teaches those skilled in the art the best net index angles that will produce the least noise related to flow pulsations in a tandem floating cup pump having an odd number of pistons. The disclosure also provides the associated ranges of net index angles that produce less noise related to flow pulsations than a pump having a zero net index angle or a net index angle of half the separation angle.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.
Claims
1. A method for reducing flow pulsations in a tandem floating cup pump having an odd number of pistons in each of a first and second rotating group, each piston on each rotating group spaced equally apart from an adjacent piston by a separation angle, comprising the steps of:
- determining a low noise net index angle that corresponds to reduced flow pulsations with respect to the flow pulsations produced at a net index angle of zero and the flow pulsations produced at a net index angle of half the separation angle;
- setting a net index angle between a top dead center orientation of the first rotating group relative to a top dead center orientation of the second rotating group to the low noise net index angle.
2. The method of reducing flow pulsations of claim 1 wherein the step of setting the net index angle to the low noise net index angle is performed by offsetting a first port plate relative to a second port plate by the low noise net index angle.
3. The method of reducing flow pulsations of claim 1 wherein the step of setting the net index angle to the low noise net index angle is performed by offsetting the first rotating group relative to the second rotating group by the low noise net index angle via a rotor.
4. The method of reducing flow pulsations of claim 1 wherein the determining step includes the steps of: Net index angle (in Deg) First Range Second Range N Minimum Maximum Minimum Maximum 5 8.64 27.36 44.64 63.36 7 6.17 19.54 31.89 45.26 9 4.80 15.20 24.80 35.20 11 3.93 12.44 20.29 28.80 13 3.32 10.52 17.17 24.37 15 2.88 9.12 14.88 21.12 17 2.54 8.05 13.13 18.64 19 2.27 7.20 11.75 16.67 21 2.06 6.51 10.63 15.09 23 1.88 5.95 9.70 13.77 25 1.73 5.47 8.93 12.67 27 1.60 5.07 8.27 11.73 29 1.49 4.72 7.70 10.92 31 1.39 4.41 7.20 10.22 33 1.31 4.15 6.76 9.60 35 1.23 3.91 6.38 9.05
- selecting the number of pistons on each rotating group;
- determining a net index angle by choosing an angle greater than one of a minimum angle of a first range and a minimum angle of a second range, but less than one of a maximum angle of a first range and a maximum angle of a second range, respectively, that corresponds to the selected number of pistons in each rotating group, using the following table:
- wherein N represents the number of pistons in each rotating group.
5. The method of reducing flow pulsations of claim 4 wherein the determining step includes the steps of: Best Net Index Angle (in degrees) N Low Best High Best 5 18 54 7 13 39 9 10 30 11 8.2 25 13 6.9 21 15 6.0 18 17 5.3 16 19 4.7 14 21 4.3 13 23 3.9 12 25 3.6 11 27 3.3 10 29 3.1 9.3 31 2.9 8.7 33 2.7 8.2 35 2.6 7.7
- selecting the number of pistons on each rotating group;
- determining a net index angle by choosing an angle about equal to one of a low best angle and a high best angle, that corresponds to the selected number of pistons in each rotating group, using the following table:
- wherein N represents the number of pistons in each rotating group.
6. A floating cup pump, comprising:
- a rotor, a first barrel plate and a second barrel plate, attached to a shaft;
- a first rotating group comprising a first set of an odd number of floating cups, each floating cup swivelly attached to the first barrel plate, a first set of an odd number of pistons, each piston being equally spaced apart from an adjacent piston by a separation angle and each piston having a first end and a second end, the first end of each piston attached to the rotor, the second end of each piston received by a respective one of the first set of floating cups;
- a second rotating group comprising a second set of the odd number of floating cups, each floating cup swivelly attached to the second barrel plate, a second set of pistons, having a same number of pistons as the first rotating group, each piston being equally spaced apart from an adjacent piston by the separation angle and each piston having a first end and a second end, the first end of each piston attached to the rotor, the second end of each piston received in a respective one of the second set of floating cups;
- the first rotating group and the second rotating group having a first relative orientation, the first relative orientation defining a piston index angle;
- a first port plate adjacent the first barrel plate defining a bottom dead center position of the first rotating group;
- a second port plate adjacent the second barrel plate defining a bottom dead center position of the second rotating group;
- the bottom dead center of the first rotating group and the bottom dead center of the second rotating group having a second relative orientation, the second relative orientation defining a port plate index angle;
- a low noise net index angle being the sum of the piston index angle and the port plate index angle, wherein the low noise net index angle is different from zero and half of the separation angle.
7. The floating cup pump of claim 6 wherein the low noise net index angle depends on the number of pistons in each rotating group.
8. The floating cup pump of claim 6 wherein the port plate index angle is the low noise net index angle, and the piston index angle is zero.
9. The floating cup pump of claim 6 wherein the piston index angle is the low noise net index angle, and the port plate index angle is zero.
10. The floating cup pump of claim 6 wherein each rotating group has eleven pistons and the low noise net index angle is about equal to one of 8 degrees and 25 degrees.
11. The floating cup pump of claim 6 wherein the low noise net index angle for an odd number of pistons ranging from 5 to 35 pistons in each rotating group is one of the greater than the minimum of the first range and less than the maximum of the first range, and greater than the minimum of the second range and less than the maximum of the second range, respectively, with respect to the following table: Net index angle (in Deg) First Range Second Range N Minimum Maximum Minimum Maximum 5 8.64 27.36 44.64 63.36 7 6.17 19.54 31.89 45.26 9 4.80 15.20 24.80 35.20 11 3.93 12.44 20.29 28.80 13 3.32 10.52 17.17 24.37 15 2.88 9.12 14.88 21.12 17 2.54 8.05 13.13 18.64 19 2.27 7.20 11.75 16.67 21 2.06 6.51 10.63 15.09 23 1.88 5.95 9.70 13.77 25 1.73 5.47 8.93 12.67 27 1.60 5.07 8.27 11.73 29 1.49 4.72 7.70 10.92 31 1.39 4.41 7.20 10.22 33 1.31 4.15 6.76 9.60 35 1.23 3.91 6.38 9.05
- wherein N represents the number of pistons in each rotating group.
12. The floating cup pump of claim 6 wherein the low noise net index angle for an odd number of pistons ranging from 5 to 35 pistons in each rotating group is about equal to one of a low best and a high best, with respect to the following table: Best Net Index Angle (in degrees) N Low Best High Best 5 18 54 7 13 39 9 10 30 11 8.2 25 13 6.9 21 15 6.0 18 17 5.3 16 19 4.7 14 21 4.3 13 23 3.9 12 25 3.6 11 27 3.3 10 29 3.1 9.3 31 2.9 8.7 33 2.7 8.2 35 2.6 7.7
- wherein N represents the number of pistons in each rotating group.
13. A floating cup pump, comprising:
- a rotor, a first barrel plate and a second barrel plate, attached to a shaft;
- a first rotating group comprising a first set of an odd number of floating cups, each floating cup swivelly attached to the first barrel plate, a first set of an odd number of pistons, each piston being equally spaced apart from an adjacent piston by a separation angle and each piston having a first end and a second end, the first end of each piston attached to the rotor, the second end of each piston received by a respective one of the first set of floating cups;
- a second rotating group comprising a second set of the odd number of floating cups, each floating cup swivelly attached to the second barrel plate, a second set of pistons, having a same number of pistons as the first rotating group, each piston being equally spaced apart from an adjacent piston by the separation angle and each piston having a first end and a second end, the first end of each piston attached to the rotor, the second end of each piston received in a respective one of the second set of floating cups;
- the first rotating group and the second rotating group having a first relative orientation, the first relative orientation defining a piston index angle;
- a first port plate adjacent the first barrel plate defining a bottom dead center position of the first rotating group;
- a second port plate adjacent the second barrel plate defining a bottom dead center position of the second rotating group;
- the bottom dead center of the first rotating group and the bottom dead center of the second rotating group having a second relative orientation, the second relative orientation defining a port plate index angle;
- a net index angle being the sum of the piston index angle and the port plate index angle; and
- means, including setting the net index angle to a low noise net index angle different from zero and half the separation angle, for reducing noise due to flow pulsations.
14. The floating cup pump of claim 13 wherein the means for reducing noise due to flow pulsations reduces the noise to lower than the noise produced when the net index angle is zero.
15. The floating cup pump of claim 13 wherein the means for reducing noise due to flow pulsations reduces the noise to lower than the noise produced when the net index angle is half the separation angle.
16. The floating cup pump of claim 13 wherein the port plate index angle is the low noise net index angle, and the piston index angle is zero.
17. The floating cup pump of claim 13 wherein the piston index angle is the low noise net index angle, and the port plate index angle is zero.
18. The floating cup pump of claim 13 wherein each rotating group has eleven pistons and the net index angle is about equal to one of 8 degrees and 25 degrees.
19. The floating cup pump of claim 13 wherein the low noise net index angle for an odd number of pistons ranging from 5 to 35 pistons in each rotating group is one of the greater than the minimum of the first range and less than the maximum of the first range, and greater than the minimum of the second range and less than the maximum of the second range, respectively, with respect to the following table: Net index angle (in Deg) First Range Second Range N Minimum Maximum Minimum Maximum 5 8.64 27.36 44.64 63.36 7 6.17 19.54 31.89 45.26 9 4.80 15.20 24.80 35.20 11 3.93 12.44 20.29 28.80 13 3.32 10.52 17.17 24.37 15 2.88 9.12 14.88 21.12 17 2.54 8.05 13.13 18.64 19 2.27 7.20 11.75 16.67 21 2.06 6.51 10.63 15.09 23 1.88 5.95 9.70 13.77 25 1.73 5.47 8.93 12.67 27 1.60 5.07 8.27 11.73 29 1.49 4.72 7.70 10.92 31 1.39 4.41 7.20 10.22 33 1.31 4.15 6.76 9.60 35 1.23 3.91 6.38 9.05
- wherein N represents the number of pistons in each rotating group.
20. The floating cup pump of claim 13 wherein the low noise net index angle for an odd number of pistons ranging from 5 to 35 pistons in each rotating group is about equal to one of a low best and a high best, with respect to the following table: Best Net Index Angle (in degrees) N Low Best High Best 5 18 54 7 13 39 9 10 30 11 8.2 25 13 6.9 21 15 6.0 18 17 5.3 16 19 4.7 14 21 4.3 13 23 3.9 12 25 3.6 11 27 3.3 10 29 3.1 9.3 31 2.9 8.7 33 2.7 8.2 35 2.6 7.7
- wherein N represents the number of pistons in each rotating group.
Type: Application
Filed: May 23, 2008
Publication Date: Nov 26, 2009
Applicant:
Inventors: Viral S. Mehta (Peoria, IL), Bryan Nelson (Lacon, IL), Kirat Shah (Dunlap, IL)
Application Number: 12/154,514
International Classification: F04B 1/22 (20060101);