Pressure regulator with multi-stage pressure loss elements

Abstract

A pressure regulator includes a housing including an inlet flow passage and an outlet flow passage, a plunger reciprocally mounted in the housing and defining a plunger flow passage, and a valve seat disposed in the housing between the inlet flow passage and an inlet to the plunger flow passage. The valve seat includes a seat surface and a seat trim. The seat trim is configured to effect multi-stage pressure losses as flow passes the seat trim into the plunger flow passage.

Description

TITLEPRESSURE REGULATOR WITH MULTI-STAGE PRESSURE LOSS ELEMENTSCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 725,270, filed November 26, 2024, the entire content of which is herein incorporated by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] (NOT APPLICABLE)BACKGROUND

[0003] The invention relates to pressure regulators and, more particularly, to pressure regulators for supplying water to irrigation sprinklers and nozzles including modified valve seat geometry to mitigate cavitation.

[0004] Irrigation systems often have several sprinklers and nozzles arranged along an extended water supply pipe. For example, a water supply pipe in a center pivot irrigation system may extend a quarter to half a mile (400 to 800 meters). The water supply pipe may have a diameter of six to ten inches (152 to 254 millimeters) and provide water for over a hundred sprinklers arranged along the pipe. Each sprinkler is typically connected to the water supply pipe by a smaller water pipe that extends vertically and includes a pressure regulator.

[0005] The sprinklers are typically designed to receive water under a relatively low pressure and within a narrow pressure range. Pressure regulators reduce the pressure in the water supply pipe to a pressure suitable for a sprinkler or nozzle. The pressure regulator ensures that the water pressure is within the design range of the sprinkler or nozzle.

[0006] The elevation of the water supply pipe in an irrigation system rises and falls as the pipe travels over the hills and low points of an agricultural field. These changes in elevation vary the pressure in the water supply pipe. The pressure regulators adjust to the changes in pressure such that water flows to the sprinklers and nozzles at a relatively uniform pressure.

[0007] Nelson Irrigation Corporation of Walla Walla, Wash., U.S.A., manufactures and sells flow-through type pressure regulators having a tubular housing with an inlet at one end and an outlet at the other end. Pressure loss through the regulator is controlled by a gap between a valve seat and a tubular plunger in the regulator. The tubular plunger is biased away from the valve seat in a normally open condition by a compression spring. The pressure of the flow at the outlet of the regulator acts on a diaphragm in the regulator. The diaphragm is attached to and moves with the plunger.

[0008] Within a normal operating flow rate range, the spring force balances against the outlet pressure applied to the diaphragm. This balance sets the opening between the valve seat and the plunger to cause the desired pressure loss at the flow rate demanded by the sprinkler. An increase in the inlet pressure will initially increase the pressure at the outlet and thus increase the pressure on the diaphragm. Due to the pressure increase, the diaphragm moves the tubular plunger towards the valve seat to narrow the gap and reduce the pressure at the outlet of the regulator. The counteracting forces of the spring and the outlet flow pressure move the plunger and adjust the gap to achieve a substantially uniform outlet pressure of the flow leaving the pressure regulator.

[0009] Exemplary pressure regulators are described in U.S. Patent No. 7,140,595 and U.S. Patent No. 9,367,070, the contents of which are hereby incorporated by reference.

[0010] It has been discovered that as inlet pressures increase well beyond the design range of existing pressure regulators, a higher required pressure loss across existing pressure loss elements of the regulator is required, which can result in loss of control due to cavitation, flashing and flow instabilities related to mixed phase (entrapped air) fluid flow. Cavitation or flashing occurs when the pressure loss across any single pressure loss element is exceedingly high such that the local pressure drops below thefluid’s vapor pressure, causing vapor bubbles (gaseous phase of fluid) to form.Cavitation makes its way downstream through the plunger and distorts the pressure sensed by the diaphragm, which leads to increases in pressure exiting the regulator. Additionally, air mixed with water causes two-phase flow, which is troublesome for the regulator to handle. Under such conditions, further increases in inlet pressure can cause increased and erratic outlet pressure fluctuations that are difficult to dampen and thus cause corresponding unpredictable sprinkler output.

[0011] One known method of preventing cavitation in other art classes of pressure reducing valves is to control the pressure drop across the valve such that the fluid pressure never drops below its vapor pressure, thereby preventing cavitation. One such method is to split the total pressure drop across the valve using multiple stages.SUMMARY

[0012] It would be desirable to design a pressure regulator with features that function to mitigate cavitation and better maintain pressure regulation with increased inlet pressures. In some embodiments, the seat for the plunger may be provided with geometric details that function to break up pressure losses into multiple elements.

[0013] In some embodiments, the seat for the plunger may be provided with a stepped configuration and / or openings in sidewalls of the seat to effect multi-stage pressure losses and thereby eliminate or reduce the potential for cavitation.

[0014] In an exemplary embodiment, a pressure regulator includes a housing including an inlet flow passage and an outlet flow passage, a plunger reciprocally mounted in the housing and defining a plunger flow passage, and a valve seat disposed in the housing between the inlet flow passage and an inlet to the plunger flow passage. The valve seat including a seat surface and a seat trim. The seat trim is configured to effect multi-stage pressure losses as flow passes the seat trim into the plunger flow passage.

[0015] In some embodiments, the seat trim may extend in a flow direction from the seat surface. The seat trim may be at least part-conical. The seat trim may include an exterior stepped surface. The seat trim may include at least one inlet cut through theexterior stepped surface. The seat trim may include a plurality of inlet cuts through the exterior stepped surface. In this context, the plurality of inlet cuts may be evenly spaced around the seat trim or unevenly spaced around the seat trim. The plurality of inlet cuts may be skewed asymmetrically relative to the valve seat to mitigate onset of vortex shedding.

[0016] In some embodiments, the seat trim may include three inlet cuts through the exterior stepped surface. The three inlet cuts may be spaced 120 degrees apart. The inlet cuts may define passageways for fluid flow into the plunger flow passage. The passageways may be oriented toward a center of the seat trim.

[0017] The at least one inlet cut may be at least part conical.

[0018] The at least one inlet cut may be U-shaped.

[0019] The at least one inlet cut may taper outward from the exterior stepped surface toward an interior of the seat trim.

[0020] The seat trim may include at least one inlet cut through an exterior surface.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] These and other aspects and advantages will be described in detail with reference to the accompanying drawings, in which:

[0022] FIG. 1 is a cross-sectional view of an existing pressure regulator;

[0023] FIG. 2 is a cross-sectional view of a pressure regulator incorporating the valve seat of the described embodiments with the plunger in an open position;

[0024] FIG. 3 is a cross-sectional view of the pressure regulator in FIG. 2 with the plunger in a regulation position;

[0025] FIGS. 4 and 5 are detailed views of the valve seat and seat trim of the described embodiments;

[0026] FIG. 6 is a graph showing outlet pressure as a function of inlet pressure for the prior art design versus the design of the described embodiments;

[0027] FIGS. 7 and 8 show a variation of the pressure regulator with the plunger in an open position and a regulation position, respectively;

[0028] FIG. 9 is a detail view of the valve seat in the variation shown in FIGS. 7 and 8;

[0029] FIG. 10 is a detail view of the valve seat including a step mismatch in the exterior stepped surface of the seat trim;

[0030] FIGS. 11-14 show variations of a drop-in valve seat including V-shaped cuts;

[0031] FIG. 15 shows the drop-in valve seat including the exterior stepped surface and the part-conical inlet cuts;

[0032] FIG. 16 shows a variation including alternative geometries; and

[0033] FIGS. 17 and 18 show the drop-in valve seat with inlet cuts and without the exterior stepped surface.DETAILED DESCRIPTION

[0034] FIG. 1 is a sectional view of an existing fluid pressure regulator. The regulator 10 includes a tubular housing 11 defined by an inlet section 12 and an outlet section 14 secured together by means of fasteners such as screws 16. The pressure regulator 10 is of the flow-through type, with an inlet provided at one end of inlet housing section 12, and an outlet provided at the distal end of the outlet housing section 14. The outlet is defined by an outlet cap 24. The inlet section 12 of the regulator may be threaded internally or externally in any of a number of thread configurations and sized to facilitate attachment to variously sized hoses or other conduits. The outlet section 14 is shown to be internally threaded (but could be exteriorly threaded), and is adapted to receive in a typical arrangement, a rotary impact type sprinkler, a fixed spray head, or other sprinkler device.

[0035] In the following description, any reference to “upper” or “lower” is based on the flow direction from inlet (“upper”) to outlet (“lower”) as shown in FIG. 1 and is not intended to limit the scope of the invention.

[0036] A tubular sleeve / liner 22 is located within the inlet section 12 that permits a piston or plunger 28 to move axially back and forth within the housing 11. The pistonor plunger 28 is provided with a radial piston flange 30 nearer the lower end of the plunger, with a disc-like diaphragm retainer 32 located adjacent and upstream (in a flow direction) of the piston flange 30. A flexible diaphragm 34 extends radially between the housing and the piston or plunger. Specifically, the radially outer end of the diaphragm 34 is clamped between the upper end of the sleeve / liner 22 and the lower end of the cap 24, and the radially inner end of the diaphragm 34 is clamped between the diaphragm retainer 32 and the piston flange 30. This arrangement creates a pressure or diaphragm chamber 36 between the diaphragm 34 and the cap 24 that is subject to regulator outlet pressure via a dampened path from a groove 38 in the lower end along the piston or plunger 28, and past an O-ring 40 located in an annular recess in the outlet cap 24 of housing section 14. The O-ring 40 acts as a means of dampening of outlet pressure feedback as described in U.S. Patent No. 5,257,646, the content of which is hereby incorporated by reference.

[0037] A coil spring 44 is arranged within the sleeve / liner 22 and surrounds the plunger 28. The spring 44 extends axially between a radially oriented upper wall of the sleeve / liner 22 and the diaphragm retainer 32, thus biasing the plunger 28 in a lower or fully open, maximum flow direction.

[0038] The inlet section 12 may include an integral regulator seat 52 at a distal end of a seat arm or strut 50. The regulator seat 52 of the prior art design defines a substantially flat, annular seating surface 60 substantially surrounded by an upstanding peripheral annular flange or wall 61.

[0039] A pair of inner and outer O-rings 82, 84 ensure that fluid flowing through the regulator, in the direction from the inlet section 12 to the outlet section 14 is constrained to flow through the reciprocal plunger 28 and around the seat 52 as described below.

[0040] The lower end of the regulator plunger 28 (below the piston flange 30) slides or reciprocates within the center opening of the outlet cap 24. The outer peripheral surface loosely engages the dampening O-ring 40 as it reciprocates within the housing, and the lower end of the plunger 28 terminates at a free downstream end, and the pistonflange 30 is adapted to engage an annular shoulder of the cap 24, thus providing a stop for downward or opening movement of the plunger 28.

[0041] In use, fluid flows through the regulator from the inlet section 12 around the seat 52 and through the plunger 28 and outlet section 14. Under normal flow pressure conditions, the plunger 28 is biased downstream as shown so that the flow through the regulator is maximized. In the event of a pressure build-up within the line or device downstream of the outlet section 14, the pressure in the chamber 36 will increase, causing the plunger 28 to move in an upstream direction toward the seat surface 60. The diaphragm 34 maintains an effective fluid-tight seal so that no fluid enters the chamber between the plunger 28 and the sleeve / liner 22 in which the spring 44 is located. The chamber is vented to atmosphere, however, by a plurality of notches or grooves, and, therefore, pressure exerted on piston flange 30 must not only overcome the spring 44, but also atmospheric pressure.

[0042] Depending upon the amount of back pressure developed within the regulator 10, the plunger 28 may move upstream so that its tapered annular edge approaches the seat surface 60 to reduce flow through the regulator, or under extreme pressure conditions, nearly seats on the seat surface 60 to thereby drastically prevent flow through the regulator. Upon a subsequent decrease in outlet pressure, the spring 44, along with atmospheric pressure, will serve to overcome whatever outlet pressure is present to move the plunger 28 downstream toward the outlet 14, thereby opening the fluid flow passage between the plunger 28 and the seat surface 60. In this way, the plunger or piston 28 continuously seeks an equilibrium position, insuring uniform pressure at the outlet 14.

[0043] As noted, the described prior art pressure regulator can lose control due to cavitation, flashing and other fluid flow oscillations or instabilities. Cavitation and / or flashing makes its way downstream in the plunger and distorts the pressure sensed by the diaphragm, which leads to increases in pressure exiting the regulator. Additionally, air mixed with water or two-phase flow is troublesome for the regulator to handle. Further increases in inlet pressure can cause increased and erratic outlet pressure fluctuations that are difficult to dampen, which lead to corresponding unpredictable sprinkler output.

[0044] FIGS. 2 and 3 illustrate a variation according to an exemplary embodiment. The general assembly and parts correspond to those in the prior art pressure regulator 10, and a description thereof will not be repeated. According to the exemplary embodiment shown in FIGS. 2 and 3, the valve seat 110 is modified to effect multi-stage pressure losses as flow passes the valve seat 110 into a plunger flow passage 112 inside the plunger 28.

[0045] The valve seat 110 is disposed in the housing 11 between the inlet flow passage 114 and an inlet to the plunger flow passage 112. The valve seat 110 includes a seat surface 60 and a seat trim 116. In some embodiments, the seat trim 116 extends in a flow direction (e.g., to the right in FIG. 2) from the seat surface 60 and may be at least part-conical.

[0046] FIGS. 4 and 5 show details of the valve seat 110. An exterior of the seat trim 116 may be provided with a stepped surface 118. That is, with the at least part- conical seat trim 116 extending in the flow direction, the seat trim 116 defines exterior steps with reducing- sized concentric circles from a base step 118a to a downstream step 118c with one or more intermediate steps 118b between the base step 118a and the downstream step 118c. Although a circular shape is shown for the trim 116, other shapes may be suitable.

[0047] The seat trim 116 may also include at least one inlet cut 122 through the exterior stepped surface 118. In some embodiments, the seat trim 116 includes three inlet cuts 122 that may be spaced 120 degrees apart. Additional inlet cuts 122 may be provided. The inlet cuts 122 may be U-shaped as shown and may taper outward from the exterior stepped surface 118 toward the interior of the seat trim 116. As such, the inlet cuts 122 may themselves be at least part conical, thereby providing a Venturi effect and accompanying pressure recovery thereafter.

[0048] The inlet cuts 122 define passageways 124 for fluid flow into the plunger flow passage 124. In the embodiment utilizing three inlet cuts 122, the passageways 124 may be oriented toward a center of the seat trim 116 such that flows through the inlet cuts 122 and through the passageways 124 impact one another at the center of the seat trim 116 providing a means of pressure recovery. Alternatively, inlet cuts 122 and thepassageways 124 may be oriented offset from the center to direct the fluid flow to one side of the center. Orientating the array of passageways 124 rotationally askew (asymmetrically skewed) relative to the seat’ s strut mitigates the formation of (von Karman) vortex shedding, which can negatively affect the fluid velocity profile as it encounters the nozzle and sprinkler downstream. Vortex street oscillations and accompanying transient instabilities can detrimentally affect a sprinkler’s distribution profile and range as well as contribute to premature pressure regulator wear. Similar constructions can be achieved with two inlet cuts 122 (see. e.g., FIG. 17 discussed below).

[0049] FIG. 6 is a graph showing outlet pressure as a function of inlet pressure for the prior art design versus the design of the described embodiments. With the prior art design, the outlet pressure begins to lose control after inlet pressure increases to 2.4 ATM above the nominal outlet pressure of 0.9 ATM. Line A in FIG. 6 shows the outlet pressure beginning to drop at A2.4 ATM through the regulator. The prior art design continues to lose control with outlet pressure beginning to rise at A4.9 ATM. See Line B in FIG 6. In comparison, with the seat trim 116 of the described embodiments, the pressure regulator maintains control until about A7.3 ATM through the regulator. See Line C in FIG. 6.

[0050] The exterior stepped surface 118 of the seat trim 116 functions to control the pressure drop across the gap between the valve seat 110 and the plunger flow passage 112 by breaking up pressure losses into multiple elements across different geometries. The stepped surface 118 creates multiple edges or “sharps” that disrupt the flow and break up pressure losses. Such features create a more tortuous fluid path than the prior art, causing the fluid to expend more energy as fluid velocities increase through the tortuous path, helping to further reduce pressure. The stepped surface 118 defines multistage pressure loss elements, where multi-step AP, avoids a larger, singular AP where the resulting minimum pressure dips below vapor pressure or, if the pressure does dip below vapor pressure, pressure recovery occurs upstream of outlet pressure sensing area, resulting in better regulation performance across higher inlet pressure realm.

[0051] With the three inlet cuts 122 (if included), in the event that pressure drops below the vapor pressure, which can lead to cavitation, the inlet cuts 122 create multiple jets that shoot inside the valve seat 110 and impact each other such that flow into the plunger flow passage 112 is redeveloped upstream of the diaphragm chamber. For example, the three inlet cuts 122 direct flow to impact itself immediately downstream of the valve seat 110, helping collapse cavitation / flashing back into single-phase liquid flow before it can migrate downstream and distort outlet sensing.

[0052] FIGS. 7-9 show an application of the valve seat 110 in a pressure regulator where the plunger flow passage has an access offset from the axis of the inlet flow passage. This variation is described in the above-referenced U.S. Patent No. 9,367,070. FIG. 7 shows the assembly including the valve seat 110 of the described embodiments with the plunger 28 in a wide-open position, and FIG. 8 shows the plunger 28 in a position closer to the valve seat 110 in a regulation position due to increased inlet pressures. FIG. 9 shows details of an exemplary valve seat 110 with the seat surface 60 and the seat trim 116. The seat trim 116 includes the exterior step surface 118 and at least one inlet cut 122 through the exterior step surface 118.

[0053] FIG. 10 shows a variation incorporating a circumferential mismatch or offset in the exterior step surface 118’. Such mismatch acts to impart additional non-streamwise components of fluid velocity or local turbulence to induce more global pressure loss through the pressure loss elements. The variation shown incorporates three inlet cuts 122 spaced 120 degrees apart, although more or fewer inlet cuts could be used.

[0054] FIGS. 11-14 show variations of a drop-in valve seat 210 for the regulator design of the above-referenced U.S. Patent No. 7,140,595. The inlet cuts 222 in FIG. 11 may be in the form of V-shaped cuts through a top portion of the seat trim 216. FIG. 12 shows a corresponding embodiment including fewer V-shaped inlet cuts 222, and FIG. 13 shows a variation with still fewer V-shaped inlet cuts 222. FIG. 14 shows a variation including notches 223 in the exterior step surface 218 of the seat trim 216. Notches 223 further partition the flow into multiple higher velocity micro jets which swirl though the majority of the flow between the step surface 118 and the inlet of the plunger 28 to encourage the implosion and collapse of cavitation.

[0055] FIG. 15 shows the drop-in valve seat 210 incorporating the exterior step surface 118 and three part-conical inlet cuts 122. FIG. 16 shows a variation of the valve seat 310 including geometrical variations on an outer lip 312 radially outward of the seat surface 60 and geometrical variations of the exterior step surface 318. FIGS. 17 and 18 show variations of the valve seat 410 incorporating inlet cuts 422 but without the exterior step surfaces. FIG. 17 shows two inlet cuts 422 that create multiple jets of flow that impact each other to help pressure recovery. FIG. 18 includes a single inlet cut 422.

[0056] The modified geometry of the valve seat exterior functions to mitigate cavitation and better maintain pressure regulation with increased inlet pressures. The described geometric details break up pressure losses into multiple elements and effect multi-stage pressure losses, which thereby eliminate or reduce the potential for cavitation. Inlet cuts in the valve seat trim create multiple jets that shoot inside the valve seat and come together such that flow into the plunger flow passage is redeveloped from the inside, helping collapse cavitation / flashing back into single-phase liquid flow before it can migrate downstream and distort outlet sensing.

[0057] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

CLAIMS1. A pressure regulator comprising: a housing including an inlet flow passage and an outlet flow passage; a plunger reciprocally mounted in the housing and defining a plunger flow passage; and a valve seat disposed in the housing between the inlet flow passage and an inlet to the plunger flow passage, the valve seat including a seat surface and a seat trim, wherein the seat trim is configured to effect multi-stage pressure losses as flow passes the seat trim into the plunger flow passage.

2. A pressure regulator according to claim 1, wherein the seat trim extends in a flow direction from the seat surface.

3. A pressure regulator according to claim 2, wherein the seat trim is at least part-conical.

4. A pressure regulator according to claim 3, wherein the seat trim comprises an exterior stepped surface.

5. A pressure regulator according to claim 4, wherein the seat trim comprises at least one inlet cut through the exterior stepped surface.

6. A pressure regulator according to claim 5, wherein the seat trim comprises a plurality of inlet cuts through the exterior stepped surface.

7. A pressure regulator according to claim 6, wherein the plurality of inlet cuts are evenly spaced around the seat trim.

8. A pressure regulator according to claim 6, wherein the plurality of inlet cuts are unevenly spaced around the seat trim.

9. A pressure regulator according to claim 6, wherein the plurality of inlet cuts are skewed asymmetrically relative to the valve seat to mitigate onset of vortex shedding.

10. A pressure regulator according to claim 5, wherein the seat trim comprises three inlet cuts through the exterior stepped surface.

11. A pressure regulator according to claim 10, wherein the three inlet cuts are spaced 120 degrees apart.

12. A pressure regulator according to claim 10, wherein the inlet cuts define passageways for fluid flow into the plunger flow passage.

13. A pressure regulator according to claim 12, wherein the passageways are oriented toward a center of the seat trim.

14. A pressure regulator according to claim 5, wherein the at least one inlet cut is at least part conical.

15. A pressure regulator according to claim 5, wherein the at least one inlet cut is U-shaped.

16. A pressure regulator according to claim 5, wherein the at least one inlet cut tapers outward from the exterior stepped surface toward an interior of the seat trim.

17. A pressure regulator according to claim 3, wherein the seat trim comprises at least one inlet cut through an exterior surface.

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