Multi-stage pumps or turbines for controlling fluids with large variations in gas fraction

Abstract

Multistage hydraulic rotating machines (MSHRMs) maintain near-optimal efficiency over widely varying conditions of use (COS) when controlling fluids with gas volume fractions (GVF) greater than 50% and large variations in volumetric flow rates (VFR) between stages. The MSHRM includes independently controlled stages with at least two different designs encompassing different VFR ranges. Stage impeller differences may include impeller diameter, blade pitch, blade width, blade count, inlet diameter, and outlet diameter. Diffusers may also vary between stages. VFR ranges may be progressively higher or lower in successive stages. Stages may share a common VFR range within which incompressible liquids may be controlled. The MSHRM can function as a pump or turbine and is applicable to energy storage and recovery in "green" energy systems.

Description

Related Applications

[0001] This application claims priority to U.S. Patent Application No. 17 / 880,076 (now U.S. Patent No. 11,655,822), filed August 3, 2022, which is incorporated herein by reference in its entirety for all purposes. [Technical Field]

[0002] The present invention relates to pumps and turbines, and more particularly to multi-stage pumps and turbines required to pump and / or extract energy from multi-phase fluids over a wide range of gas fractions. [Background technology]

[0003] Rotary pumps, turbines, and hybrid pump / turbines, referred to herein as "hydraulic rotary machines" or "HRMs," are typically capable of efficiently controlling process fluids over a finite range of volumetric flow rates (VFRs) and pressure differentials ("heads"). The set of operating conditions or "conditions of use" (COS) at which the efficiency of an HRM is optimized is sometimes referred to as the HRM's "best efficiency point" (BEP).

[0004] If the rotational speed of the HRM is fixed, for example, if the HRM is driven by a synchronous motor operating at line frequency, it is necessary to select or design an HRM whose BEP matches the desired VFR at a particular rotational speed, head, and other particular COS. For example, the impeller diameter, inlet and outlet diameters, impeller blade count, and / or impeller blade inlet and outlet pitch can be selected as needed to provide an HRM with a BEP that matches the desired VFR and head at a particular rotational speed.

[0005] For a variable-speed HRM, the BEP can generally be shifted or "adjusted" over a range of VFR (referred to herein as the "VFR range" of the HRM) simply by adjusting the rotational speed of the HRM. For example, if the COS remains otherwise unchanged, it may be possible to double the VFR of the BEP simply by doubling the rotational speed of the HRM. Of course, in general, the VFR range will be finite, i.e., there will be a minimum VFR and a maximum VFR between which the BEP can be adjusted by changing the rotational speed of the HRM.

[0006] When the head drop or pressure drop required for an application is large, it can be difficult or unfeasible to design a single impeller HRM that can meet the requirements. Instead, it is common to implement a multi-stage HRM (MSHRM), a type of HRM that includes multiple stages. Typically, the stages are substantially identical to one another and are arranged in series with the impellers of the stages all mounted on a common shaft, thereby operating at a common, fixed rotational speed, which is typically determined by the type of drive motor and / or by the frequency of the power grid.

[0007] For an MSHRM, the mass flow rate must be the same for all stages at any given time. If the process fluid is a liquid and remains substantially incompressible as it flows through the MSHRM, the VFR will also be the same for all stages of the HRM. However, if the process fluid has a substantial gas void fraction (GVF) due to gas present in the process fluid upon entering the MSHRM and / or due to a liquid / gas phase transition occurring within the MSHRM, the compressible gas component of the process fluid will lead to changes in GVF between stages, thereby requiring different VFRs in different HRM stages, even if the mass flow rate remains the same for all HRM stages. In some applications, the liquid / gas phase transition within the MSHRM can lead to a gas void fraction of up to 50% or more, even if the process fluid enters the MSHRM as a pure liquid.

[0008] Referring to Figure 1A, one approach is to provide an MSHRM with multiple identical HRM stages 100 with independently controlled variable rotational speeds. Referring to Figure 1B, for some applications, efficient operation of the MSHRM can be achieved with compressible process fluids by adjusting the speed of each of the stages to match the BEP with the VFR required for that stage.

[0009] If the GVF remains low throughout the MSHRM, only minor adjustments to the stage rotational speed are required. In the example of Figure 1B, the BEP of each stage 100 is variable over a VFR range 102, from a minimum VFR 104 of 500 gallons per minute (gpm) at a rotational speed of 1500 rpm to a maximum VFR 106 of 1000 gpm at a rotational speed of 3000 rpm. In the illustrated example, the first stage 108 requires a VFR of approximately 800 gpm, the second stage 110 requires a VFR of approximately 700 gpm, the third stage 112 requires a VFR of approximately 650 gpm, and the fourth stage 114 requires a VFR of approximately 550 gpm. As can be seen, all of these VFR requirements fall within the VFR range of the MSHRM stages 100.

[0010] However, if the process fluid has a large GVF, the VFR may vary greatly between stages, making it difficult to find a mass flow rate at which the BEP of every stage can be matched to the required VFR.

[0011] In general, the VFR range of an HRM depends on the COS (such as the pressure differential (head) across the HRM, fluid temperature, fluid viscosity, and other factors). Some HRM applications require operation over a very wide COS range, which may include large changes in fluid temperature and / or HRM pressure differential (head) and resulting large changes in GVF (such as up to 30%, 50%, or more) due to, for example, pressure-induced and / or temperature-induced changes in the liquid / gas phase transition. COS variations may also include large changes in the mass flow rate required through the MSHRM. As a result, in such applications, stages of the MSHRM may be required to accommodate very large changes in VFR.

[0012] For example, technologies for green energy storage and recovery may require operation of MSHRMs over a particularly wide COS range. MSHRMs are typically used in these technologies for both storing energy (pumping mode) and recovering stored energy (turbine mode). For example, excess energy can be used to pump water from a lower reservoir to a higher reservoir during times of low energy demand, and then a turbine can be used to recover energy when water is allowed to flow from the higher reservoir to the lower reservoir during times of high energy demand.

[0013] Similarly, an MSHRM can be used to pressurize and / or liquefy gas in a storage container when excess energy is available, and then the stored gas can be allowed to vaporize and / or expand during times of high energy demand so that it can be used to operate a turbine. For example, energy can be stored by compressing carbon dioxide to a supercritical liquid state in a storage tank, and then the stored energy can be recovered by vaporizing the carbon dioxide and passing the resulting gas through a turbine.

[0014] As another example, an MSHRM can be used to drive a heat pump cycle that stores energy by heating or cooling a thermal storage medium. In each case, a separate pump and turbine can be implemented, or a dual-mode pump / turbine HRM can be used to meet the requirements of both the energy storage and energy recovery cycles of the energy storage system.

[0015] In such applications, the GVF within each stage of the MSHRM can vary widely. For example, when compressing gas, the pressure differential across the MSHRM can vary significantly, leading to large GVF variations. Furthermore, the energy available to drive the pumping system or the energy required from the turbine system can vary widely depending on the degree of energy surplus or deficit, thereby leading to wide variations in mass flow requirements through the MSHRM.

[0016] For such applications, even if the rotational speeds of the stages were independently controlled, it may not be possible for the MSHRM to maintain efficient operation over the required GVF range.

[0017] Therefore, there is a need for a multi-stage HRM (MSHRM) that can maintain near-optimal operating efficiency when controlling fluids with significant gas volume fractions (GVFs) that can vary widely, resulting in wide variations in volumetric flow rates (VFRs) that can vary significantly over time and substantially between HRM stages. Summary of the Invention

[0018] The present invention is a multi-stage HRM (MSHRM) that can maintain near-optimum operating efficiency when controlling fluids with substantial gas volume fractions (GVFs) that can vary widely, resulting in wide variations in volumetric flow rates (VFRs) that can vary significantly over time and substantially between HRM stages.

[0019] The MSHRM of the present invention comprises multiple HRM stages with independently controlled rotational speeds. Furthermore, the HRM stages include at least two stages with different designs that provide different VFR ranges for the stages. In some embodiments, the impeller diameter differs between at least two of the stages. In other embodiments, the impeller blade pitch, and therefore the impeller width, differs between at least two of the stages. In still other embodiments, the width and / or number of impeller blades, impeller diameter, inlet diameter, outlet diameter, and / or hydraulic passage width differ between different stages. Embodiments include similar differences between the diffusers of the HRM stages.

[0020] While the VFR requirements for various stages of an MSHRM can vary widely, for many applications, it can generally be expected that the required VFR will be higher for certain stages than for others. For example, if an MSHRM functions as a compressor and is required to compress a process fluid with a high GVF, the GVF will generally decrease with each stage as the gas in the process fluid is compressed. Conversely, for an MSHRM functioning as a turbine, the VFR will generally increase with each stage as the gas in the process fluid expands.

[0021] Thus, in many compressor embodiments, the minimum and maximum VFRs of the first stage of the MSHRM are both higher than the corresponding minimum and maximum VFRs of the last stage of the MSHRM. This allows the VFR across the MSHRM to vary from the maximum VFR of the first stage to the minimum VFR of the last stage. Conversely, in many turbine embodiments, the minimum and maximum VFRs of the first stage of the MSHRM are both lower than the corresponding minimum and maximum VFRs of the last stage of the MSHRM. This allows the VFR across the MSHRM to vary from the minimum VFR of the first stage to the maximum VFR of the last stage.

[0022] As a simple hypothetical example, if a steady linear increase in VFR is predicted across multiple stages of an MSHRM of the present invention, the stages may be designed so that their VFR ranges are "zigzag," i.e., so that the VFR ranges are of similar width but offset with respect to their minimum and maximum VFR values.

[0023] In some embodiments, there is a "common" VFR range where the VFR ranges of the stages of the MSHRM overlap. Thus, these embodiments can effectively control pure liquids at VFR values ​​that fall within the common VFR range. In other embodiments that require accommodating a very wide VFR range and do not allow for control of pure liquids, there is no VFR that is common to all VFR ranges of all MSHRM stages. In embodiments, there is some overlap between the VFR ranges of each pair of adjacent stages within the MSHRM.

[0024] The present invention is a multi-stage hydraulic rotary machine (MSHRM) comprising a first stage having a first design and a second stage having a second design different from the first design, the first and second designs comprising corresponding first and second rotatable impellers, respectively, the MSHRM configured to control a process fluid as the process fluid flows sequentially through the first and second stages.

[0025] The MSHRM further includes a rotational speed of the first impeller and a rotational speed of the second impeller that are independently controllable over a first speed range and a second speed range, respectively. The first design has a first best efficiency point (BEP) at which the first stage operates at maximum efficiency, and the first BEP includes 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 rotational speed of the first impeller over a first speed range from a first minimum speed to a first maximum speed.

[0026] The second design has a second BEP at which the second stage operates at maximum efficiency, and the second BEP includes 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 rotational speed of the second impeller over a second speed range from a second minimum speed to a second maximum speed, wherein 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.

[0027] In the embodiment, the first minimum VFR is greater than the second minimum VFR and the first maximum VFR is greater than the second maximum VFR, or the second minimum VFR is greater than the first minimum VFR and the second maximum VFR is greater than the first maximum VFR.

[0028] In any of the above embodiments, the diameter of the first impeller may be different from the diameter of the second impeller.

[0029] In any of the above embodiments, the width of the first impeller may be different from the width of the second impeller.

[0030] In any of the above embodiments, the first impeller may include a different number of impeller blades than the number of impeller blades of the second impeller.

[0031] In any of the above embodiments, the width of the impeller blades of the first impeller may be different from the width of the impeller blades of the second impeller.

[0032] In any of the above embodiments, the inlet diameter of the first stage may be different from the inlet diameter of the second stage.

[0033] In any of the above embodiments, the outlet diameter of the first stage may be different from the outlet diameter of the second stage.

[0034] In any of the above embodiments, the first stage diffuser may be different from the second stage diffuser.

[0035] In any of the above embodiments, the hydraulic line width of the first stage may be different from the hydraulic line width of the second stage.

[0036] In any of the above embodiments, the first and second VFR ranges may overlap such that a common VFR range is included in both the first and second VFR ranges.

[0037] In any of the above embodiments, the MSHRM may be configured to control a process fluid having a gas volume fraction (GVF) of at least 50% in at least one of the first and second stages.

[0038] In any of the above embodiments, the MSHRM may be configured to function as a pump, a turbine, or a hybrid pump / turbine.

[0039] In any of the above embodiments, the MSHRM includes a third stage with a third rotatable impeller, the MSHRM is configured to control the process fluid as it flows sequentially through the first, second, and third stages, the rotational speed of the third impeller is controllable independently from the rotational speeds of the first and second impellers over a third speed range, and the third BEP includes 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 rotational speed of the third impeller over the third speed range from a third minimum speed to a third maximum speed.

[0040] In some of these embodiments, the MSHRM is configured to compress the process fluid, and the third minimum VFR is greater than the second minimum VFR, the third maximum VFR is greater than the second maximum VFR, the second minimum VFR is greater than the first minimum VFR, and the second maximum VFR is greater than the first maximum VFR.

[0041] In any of these embodiments, the MSHRM may be configured to function as a turbine by extracting energy from the process fluid, wherein the third minimum VFR is less than the second minimum VFR, the third maximum VFR is less than the second maximum VFR, the second minimum VFR is less than the first minimum VFR, and the second maximum VFR is less than the first maximum VFR.

[0042] The features and advantages described herein are not all-inclusive, and many additional features and advantages will become apparent to those skilled in the art, especially upon consideration of the drawings, specification, and claims. Furthermore, it should be noted that the terminology used herein has been chosen primarily for ease of reading and guidance purposes, and not to limit the scope of the inventive subject matter. [Brief explanation of the drawings]

[0043] [Figure 1A] FIG. 1 is a cross-sectional view of a prior art MSHRM in which all stages are identical to one another.

[0044] [Figure 1B] 1B is a graph illustrating the rotational speed settings of the MSHRM of FIG. 1A in a hypothetical example.

[0045] [Figure 2] 4 is a graph showing the rotational speed settings of two stages having different designs in a first embodiment of the present invention.

[0046] [Figure 3] 6 is a graph showing the rotational speed settings of two stages having different designs in a second embodiment of the present invention.

[0047] [Figure 4A] FIG. 1 is a cross-sectional view showing a five-stage embodiment of the present invention.

[0048] [Figure 4B] FIG. 4B is an enlarged cross-sectional view of the first stage of the embodiment of FIG. 4A.

[0049] [Figure 4C] FIG. 4B is an enlarged cross-sectional view of the fifth stage of the embodiment of FIG. 4A. DETAILED DESCRIPTION OF THE INVENTION

[0050] The present invention is a multi-stage HRM (MSHRM) that can maintain near-optimum operating efficiency when controlling fluids with significant gas volume fractions (GVF) that can vary widely, resulting in wide variations in volumetric flow rates (VFR) that can vary significantly over time and substantially between HRM stages.

[0051] The MSHRM of the present invention includes multiple HRM stages 100 with independently controlled rotational speeds. Further, referring to FIG. 2 , the HRM stages 100 include at least two stages 100 with different designs (structures) that give the stages different VFR ranges 200, 202. In some embodiments, the impeller diameter differs between at least two of the stages. In the illustrated embodiment, stages 1 and 2 are identical to one another, and stages 3 and 4 are identical to one another, while the impeller blade pitch, and therefore impeller width, differs between stages 1 and 2 and stages 3 and 4. In still other embodiments, the width and / or number of impeller blades, impeller diameter, inlet diameter, outlet diameter, and / or hydraulic passage width differ between different stages. Embodiments include similar differences between the diffusers of the HRM stages.

[0052] While the VFR requirements of the various stages of an MSHRM can vary widely, in many embodiments, it can be expected that certain stages 100 will have higher VFR requirements than other stages. For example, if the MSHRM functions as a compressor and is required to compress a process fluid with a high GVF, the GVF will generally decrease with each stage as the gas in the process fluid is compressed. Conversely, for an MSHRM functioning as a turbine, the VFR will generally increase with each stage as the gas in the process fluid expands.

[0053] 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 210 for the first stage to the minimum VFR 204 for the last stage. In the illustrated example, the first stage operating point 212 is at a VFR of approximately 1450 gpm at a rotational speed of approximately 3000 rpm. The second stage operating point 214 is at a VFR of approximately 1100 gpm at a rotational speed of approximately 2200 rpm. The operating point 216 of the third stage (which has a different design than stages 1 and 2) is about 840 gpm at a rotational speed of about 2750 rpm, and the operating point 218 of the fourth (and final) stage is at a VFR of about 600 gpm at a rotational speed of about 1950 rpm.

[0054] Conversely, in many turbine embodiments, the minimum and maximum VFRs of the first stage of the MSHRM will both be lower than the corresponding minimum and maximum VFRs of the last stage of the MSHRM, allowing the VFR across the MSHRM to vary from the minimum VFR of the first stage to the maximum VFR of the last stage.

[0055] In the embodiment of Figure 2, there is a "common" VFR range 222 where both VFR ranges 200, 202 of the MSHRM stages 100 overlap. Thus, the illustrated embodiment can effectively control pure liquid at VFR values ​​that fall within the common VFR range 222, which in the illustrated embodiment is approximately 700 gpm to 900 gpm.

[0056] 3, in other embodiments that require accommodating a very wide VFR range 300 and do not allow for pure liquid control, there is no VFR that is common to all VFR ranges of all MSHRM stages. Instead, the VFR must vary within the MSHRM over at least a minimum range 302. However, the illustrated embodiment includes some overlap between the VFR ranges of each pair of adjacent stages within the MSHRM.

[0057] 3 shows a simple hypothetical example in which a steady linear increase 304 in BEP VFR is predicted across five stages 100 of an MSHRM as a function of rotational speed. In the illustrated example, the stages are designed so that their VFR ranges 306-314 are "zigzag," i.e., so that the BEP VFR in the ranges 306-314 varies similarly with rotational speed, but the minimum and maximum VFR values ​​in the ranges 306-314 are continuously offset from each other. In the illustrated example, the first stage set point 316 is at approximately 3200 gpm at a rotational speed of approximately 3200 rpm, the second stage set point 318 is at approximately 2500 gpm at a rotational speed of approximately 2700 rpm, the third stage set point 320 is at approximately 1900 gpm at a rotational speed of approximately 2200 rpm, the fourth stage set point 322 is at approximately 1200 gpm at a rotational speed of approximately 1750 rpm, and the fifth stage set point 324 is at approximately 3200 gpm at a rotational speed of approximately 3200 rpm.

[0058] FIG. 4A is a scale cross-sectional view of an MSHRM including five stages 400-408, where the first two stages 400, 402 are identical to one another, the last two stages 406, 408 are identical to one another, and the third stage 404 has a different design than all of the other stages 400-402, 406-408. Thus, the stages 400-408 of the illustrated MSHRM have three different designs. Impeller widths 410-418 are shown in the figure, with the first two impeller widths 410, 412 being the smallest, the last two impeller widths 416, 418 being the largest, and the impeller width 414 of the third stage 404 being midway between the maximum and minimum values. In arbitrary units, the impeller widths are 0.65 for stages 1 and 2, 1.00 for stage 3, and 1.30 for stages 4 and 5.

[0059] FIG. 4B is a close-up of the first stage 400 of FIG. 4A, and FIG. 4C is a close-up of the last stage 408 of FIG. 4A. In these close-ups, the difference between the impeller widths 410, 418 can be seen more clearly. Additionally, the impeller diameters 420, 422 are also shown. It can be seen that the impeller diameter 420 of the first stage 400 is smaller than the impeller diameter 422 of the fifth stage 408. In arbitrary units, the impeller diameters are 5.06 for stages 1 and 2, 5.81 for stage 3, and 8.06 for stage 5.

[0060] The foregoing description of embodiments of the present invention has been presented for purposes of illustration and description. Every page of this submission and all of its contents, however characterized, identified, or numbered, regardless of form or arrangement within this application, is considered a substantial part of this application for all purposes. This application 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.

[0061] Although the present application is presented in a limited number of forms, the scope of the present invention is not limited to these forms and is susceptible to various modifications and variations. The disclosure presented herein does not explicitly disclose all possible combinations of features that are within the scope of the present invention. Features disclosed herein for various embodiments are generally interchangeable and can be combined in any combination that is not self-contradictory without departing from the scope of the present invention. In particular, the limitations presented in the following claims can be combined with their corresponding dependent claims in any number and in any order, as long as the dependent claims are not logically inconsistent with each other, without departing from the scope of the present disclosure.

Claims

1. 1. A multi-stage hydraulic rotating machine (MSHRM), comprising: a first stage having a first design and a second stage having a second design different from the first design; the first and second designs include corresponding first and second rotatable impellers, respectively, and the MSHRM is configured to control the process fluid as it flows sequentially through the first and second stages; the rotational speed of the first impeller and the rotational speed of the second impeller are independently controllable over a first speed range and a second speed range, respectively; the first design has a first best efficiency point (BEP) at which the first stage operates at maximum efficiency, the first BEP including a first BEP volumetric flow rate (VFR) adjustable over a first VFR range from a first minimum VFR to a first maximum VFR by varying the rotational speed of the first impeller over the first speed range from a first minimum speed to a first maximum speed; the second design has a second BEP at which the second stage operates at maximum efficiency, the 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 rotational speed of the second impeller over the second speed range from a second minimum speed to a second maximum speed; 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. 2. The MSHRM of claim 1, wherein the first minimum VFR is greater than the second minimum VFR and the first maximum VFR is greater than the second maximum VFR, or the second minimum VFR is greater than the first minimum VFR and the second maximum VFR is greater than the first maximum VFR.

3. 3. The MSHRM of claim 1 or 2, wherein the diameter of the first impeller is different from the diameter of the second impeller.

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

5. 5. The MSHRM of claim 1, wherein the first impeller comprises a number of impeller blades that differs from the number of impeller blades of the second impeller.

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

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

8. 8. The MSHRM of any one of claims 1 to 7, wherein the outlet diameter of the first stage is different from the outlet diameter of the second stage.

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

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

11. 11. The MSHRM of any one of claims 1 to 10, wherein the first and second VFR ranges overlap such that a common VFR range is included in both the first and second VFR ranges.

12. 12. The MSHRM of any one of claims 1 to 11, wherein the MSHRM is configured to control a process fluid having a gas volume fraction (GVF) of at least 50% in at least one of the first and second stages.

13. 13. The MSHRM of any one of claims 1 to 12, wherein the MSHRM is configured to function as a pump.

14. 13. The MSHRM of any one of claims 1 to 12, wherein the MSHRM is configured to function as a turbine.

15. 15. The MSHRM of any one of claims 1 to 14, wherein the MSHRM is configured to function as a hybrid pump / turbine.

16. 16. A MSHRM according to any one of claims 1 to 15, the MSHRM comprises a third stage comprising a third rotatable impeller; the MSHRM is configured to control the process fluid as it flows sequentially through the first stage, the second stage, and the third stage; the rotational speed of the third impeller is controllable independently from the rotational speeds of the first and second impellers over a third speed range; the MSHRM, wherein the third BEP includes a third BEP VFR adjustable over a third VFR range from a third minimum VFR to a third maximum VFR by varying the rotational speed of the third impeller over the third speed range from a third minimum speed to a third maximum speed.

17. 17. The MSHRM of claim 16, 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; The second minimum VFR is greater than the first minimum VFR, and the second maximum VFR is greater than the first maximum VFR. MSHRM.

18. 17. The MSHRM of claim 16, the MSHRM is configured to function as a turbine by extracting energy from the process fluid; the third minimum VFR is less than the second minimum VFR, and the third maximum VFR is less than the second maximum VFR; The second minimum VFR is less than the first minimum VFR, and the second maximum VFR is less than the first maximum VFR. MSHRM.

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