Multi-stage pump or turbine for controlling fluids with significant variations in gas fraction

Abstract

A multi-stage hydraulic rotating machine (MSHRM) maintains near-optimal efficiency over widely varying conditions of service (COS) when controlling a fluid having a gas volume fraction (GVF) greater than 50% and large changes in volumetric flow rate (VFR) between stages. The MSHRM includes separately controlled stages having at least two different designs with different VFR ranges. Stage impellor differences can include impellor diameter, blade pitch, blade width, blade number, inlet diameter, and outlet diameter. Diffusers can differ in similar ways between stages. VFR ranges can be progressively higher or lower in successive stages. The stages can share a common VFR range within which incompressible liquids can be controlled. The MSHRM can function as a pump or turbine, and can be applicable to energy storage and recovery in “green” energy systems.

Claims

1. A multi-stage hydraulic rotating machine (MSHRM) comprising: a first stage having a first design, and a second stage having a second design that is different from the first design, said first and second designs comprising respective first and second rotatable impellors, the MSHRM being configured to control a process fluid as the process fluid flows serially through the first stage and through the second stage; a rotating speed of the first impellor and a rotating speed of the second impellor being independently controllable over a first speed range and a second speed range, respectively; said first design having a first best efficiency point (BEP) at which the first stage operates at maximal efficiency, said first BEP including a first BEP volumetric flow rate (VFR) that is adjustable over a first VFR range from a first minimum VFR to a first maximum VFR by varying the rotating speed of the first impellor over the first speed range from a first minimum speed to a first maximum speed; said second design having a second BEP at which the second stage operates at maximal efficiency, said second BEP including a second BEP VFR that is adjustable over a second VFR range from a second minimum VFR to a second maximum VFR by varying the rotating speed of the second impellor over the second speed range from a second minimum speed to a second maximum speed; and the first minimum VFR is not equal to the second minimum VFR, and/or the first maximum VFR is not equal to the second maximum VFR.

2. The MSHRM of claim 1, wherein said first minimum VFR is greater than said second minimum VFR, and said first maximum VFR is greater than said second maximum VFR, or said second minimum VFR is greater than said first minimum VFR, and said second maximum VFR is greater than said first maximum VFR.

3. The MSHRM of claim 1, wherein a diameter of the first impellor is different from a diameter of the second impellor.

4. The MSHRM of claim 1, wherein a width of the first impellor is different from a width of the second impellor.

5. The MSHRM of claim 1, wherein the first impellor includes a number of impellor blades that is different from a number of impellor blades of the second impellor.

6. The MSHRM of claim 1, wherein a width of impellor blades of the first impellor is different from a width of impellor blades of the second impellor.

7. The MSHRM of claim 1, wherein an inlet diameter of the first stage is different from an inlet diameter of the second stage.

8. The MSHRM of claim 1, wherein an outlet diameter of the first stage is different from an outlet diameter of the second stage.

9. The MSHRM of claim 1, wherein a diffuser of the first stage is different from a diffuser of the second stage.

10. The MSHRM of claim 1, wherein a hydraulic passage width of the first stage is different from a hydraulic passage width of the second stage.

11. The MSHRM of claim 1, wherein the first and second VFR ranges overlap, such that a common VFR range is included in both of the first and second VFR ranges.

12. The MSHRM of claim 1, wherein the MSHRM is configured to control a process fluid having a gas volume fraction (GVF) in at least one of the first and second stages of at least 50%.

13. The MSHRM of claim 1, wherein the MSHRM is configured to function as a pump.

14. The MSHRM of claim 1, wherein the MSHRM is configured to function as a turbine.

15. The MSHRM of claim 1, wherein the MSHRM is configured to function as a hybrid pump/turbine.

16. The MSHRM of claim 1, wherein: the MSHRM includes a third stage comprising a third rotatable impellor; the MSHRM being configured to control the process fluid as the process fluid flows serially through the first stage, through the second stage, and through the third stage; a rotating speed of the third impellor being controllable over a third speed range independently from the rotating speeds of the first and second impellors; and the third BEP including a third BEP VFR that is adjustable over a third VFR range from a third minimum VFR to a third maximum VFR by varying the rotating speed of the third impellor over the third speed range from a third minimum speed to a third maximum speed.

17. The MSHRM of claim 16 wherein: the MSHRM is configured to compress the process fluid; the third minimum VFR is greater than the second minimum VFR and the third maximum VFR is greater than the second maximum VFR; and the second minimum VFR is greater than the first minimum VFR and the second maximum VFR is greater than the first maximum VFR.

18. The MSHRM of claim 16 wherein: the MSHRM is configured to extract energy from the process fluid, thereby functioning as a turbine; the third minimum VFR is less than the second minimum VFR and the third maximum VFR is less than the second maximum VFR; and the second minimum VFR is less than the first minimum VFR and the second maximum VFR is less than the first maximum VFR.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a cross-sectional illustration of an MSHRM of the prior art, in which all stages are identical to each other;

(2) FIG. 1B is a graph that illustrates rotational speed settings of the MSHRM of FIG. 1A in a hypothetical example;

(3) FIG. 2 is a graph that illustrates rotational speed settings for two stages having different design in a first embodiment of the present invention;

(4) FIG. 3 is a graph that illustrates rotational speed settings for two stages having different design in a second embodiment of the present invention;

(5) FIG. 4A is a cross-sectional illustration of a 5-stage embodiment of the present invention;

(6) FIG. 4B is a close-up cross-sectional view of the first stage of the embodiment of FIG. 4A; and

(7) FIG. 4C is a close-up cross-sectional view of the fifth stage of the embodiment of FIG. 4A.

DETAILED DESCRIPTION

(8) The present invention is a multi-stage HRM (MSHRM) that can maintain near-optimal operating efficiency when controlling a fluid having a significant gas volume fraction (GVF) that is widely variable, thereby leading to widely varying volumetric flow rates (VFRs) that can change significantly over time and can vary substantially between the HRM stages.

(9) The MSHRM of the present invention includes a plurality of HRM stages 100 having rotational speeds that are separately controlled. In addition, with reference to FIG. 2, the HRM stages 100 include at least two stages 100 having different designs, causing those stages to have different VFR ranges 200, 202. In some embodiments, the impellor diameters are different between at least two of the stages. In the illustrated embodiment, stages 1 and 2 are identical to each other, and stages 3 and 4 are identical to each other, while the blade pitch, and hence the impellor width, of the impellors is different between stages 1 and 2 and stages 3 and 4. In still other embodiments, the widths and/or number of the impellor blades, the inlet diameter, the outlet diameter, and/or the hydraulic passage widths are different between different stages. Embodiments include similar differences between the diffusers of the HRM stages.

(10) While the VFR requirements for the various stages of an MSHRM can vary widely, in many embodiments it can be expected that the VFR requirements for certain stages 100 will be higher than for other stages. For example, if an MSHRM functions as a compressor and is required to compress a process fluid that includes a high GVF, there will generally be a reduction in the GVF from stage to stage as the gas in the process fluid is compressed. Conversely, for an MSHRM that functions as a turbine, there will generally be an increase in the VFR from stage to stage as the gas in the process fluid expands.

(11) Accordingly, in the compressor embodiment of FIG. 2, the minimum VFR 208 for stages 1 and 2 is greater than the minimum VFR 204 for stages 3 and 4, and the maximum VFR 210 for stages 1 and 2 is greater than the maximum VFR 206 for stages 3 and 4. This allows the VFR across the MSHRM to vary over a VFR range 220 that extends from the maximum VFR of the first stage 210 down to the minimum VFR of the last stage 204. In the illustrated example, the operating point 212 of the first stage is at a VFR of about 1450 gpm, with a rotating speed of about 3000 rpm. The operating point 214 of the second stage is at a VFR of about 1100 gpm, with a rotating speed of about 2200 rpm. The operating point 216 of the third stage (having a different design from stages 1 and 2) is about 840 gpm, with a rotating speed of about 2750 rpm, and the operating point 218 of the fourth (and last) stage is at a VFR of about 600 gpm at a rotating speed of about 1950 rpm.

(12) Conversely, in many turbine embodiments, the minimum and maximum VFRs for the first stage of the MSHRM will both be lower than the corresponding minimum and maximum VFR for the last stage of the MSHRM. This allows the VFR across the MSHRM to vary from the minimum VFR of the first stage up to the maximum VFR of the last stage.

(13) In the embodiment of FIG. 2, there is a “common” VFR range 222 that is overlapped by both of the VFR ranges 200, 202 of the stages 100 of the MSHRM. Accordingly, the illustrated embodiment is able to efficiently control pure liquids at VFR values that lie within the common VFR range 222, which in the illustrated embodiment is about 700 gpm to 900 gpm.

(14) With reference to FIG. 3, in other embodiments that are required to adapt to very wide VFR ranges 300 and do not anticipate controlling a pure liquid, there is no VFR that is common to all of the VFR ranges of all of the MSHRM stages. Instead, the VFR is required to vary within the MSHRM over at least a minimum range 302. The illustrated embodiment does, however, include some overlap between the VFR ranges of each pair of adjacent stages in the MSHRM.

(15) FIG. 3 illustrates a simple, hypothetical example in which a steady, linear increase 304 of the BEP VFR is expected across the five stages 100 of the MSHRM as a function of rotating speed. In the illustrated example, the stages are designed such that their VFR ranges 306-314 are “staggered,” i.e. the BEP VFRs of the ranges 306-314 vary with the rotating speed in a similar manner, but the minimum and maximum VFR values of the ranges 306-314 are successively offset from each other In the illustrated example, the set point 316 of the first stage is at about 3200 gpm at a rotating speed of about 3200 rpm, the set point 318 of the second stage is at about 2500 gpm at a rotating speed of about 2700 rpm, the set point 320 of the third stage is at about 1900 gpm at a rotating speed of about 2200 rpm, the set point 322 of the fourth stage is at about 1200 gpm at a rotating speed of about 1750 rpm, and the set point 324 of the fifth stage is at about 3200 gpm at a rotating speed of about 3200 rpm.

(16) FIG. 4A is a cross-sectional illustration, drawn to scale, of an MSHRM that includes five stages 400-408, of which the first two stages 400, 402 are identical to each other, and the final two stages 406, 408 are identical to each other, the third stage 404 having a design that is different from all of the other stages 400-402, 406-408. The stages 400-408 of the illustrated MSHRM therefore include three different designs. The impellor widths 410-418 are indicated in the figure, and it can be seen that the first two impellor widths 410, 412 are the smallest and the final two impellor widths 416, 418 are the greatest, with the impellor width 414 of the third stage 404 being intermediate between the two extremes. In arbitrary units, the impellor widths are 0.65 for stages 1 and 2, 1.00 for stage 3, and 1.30 for stages 4 and 5.

(17) FIG. 4B is an expanded view of the first stage 400 of FIG. 4A, and FIG. 4C is an expanded view of the final stage 408 of FIG. 4A. In these enlarged views, the differences between the impellor widths 410, 418 can be more clearly seen. In addition, the diameters 420, 422 of the impellors are also indicated. It can be seen that the impellor diameter 420 for the first stage 400 is smaller than the impellor diameter 422 of the fifth stage 408. In arbitrary units, the impellor diameters are 5.06 for stages 1 and 2, 5.81 for stage 3, and 8.06 for stage 5.

(18) The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

(19) Although the present application is shown in a limited number of forms, the scope of the invention is not limited to just these forms, but is amenable to various changes and modifications. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the invention. The features disclosed herein for the various embodiments can generally be interchanged and combined into any combinations that are not self-contradictory without departing from the scope of the invention. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.