Flow restrictor for mass flow regulator configured for regulating fluid mass flow

Abstract

The invention relates to a flow restrictor (201) for a mass flow regulator, which is designed to regulate a fluid mass flow, having at least two flow guide elements (214, 215, 216), the flow guiding elements are from the following group: an inlet plate (214) with at least one inlet hole (217), a throttle plate (215) with at least one throttle hole (218), a discharge plate (216) with at least one discharge hole (219), the flow guiding elements (214, 215, 216) are arranged at a distance from one another, and the flow guiding elements (214, 215, 216) are arranged at a distance from one another. The at least one inlet opening (217), the at least one throttle opening (218) and the at least one outlet opening (219) are arranged offset relative to one another in a spatial direction transverse to a central axis (202) of the flow throttle (201).

Description

Technical Field

[0001] The invention relates to a flow restrictor for use as a mass flow regulator for regulating a fluid mass flow. Background Art

[0002] US Pat. No. 8,910,656 discloses a fluid regulator having a carrier unit, a liquid regulating valve, a pressure sensor and a housing, wherein a fluid channel is configured in the housing, and the fluid channel is provided with a flow throttle configured as a laminar flow element for determining the fluid mass flow, and the flow throttle has a defined flow resistance related to the fluid mass flow. The pressure difference caused by the flow throttle is determined by the pressure sensor and can realize the calculation of the fluid mass flow through the fluid channel. Summary of the invention

[0003] The object of the present invention is to provide a flow throttle for use as a mass flow regulator for regulating a fluid mass flow, which flow throttle has a compact design.

[0004] This object is achieved for a flow throttle by means of the following features: the flow throttle has at least two flow guide elements from the group consisting of an inlet plate with at least one inlet opening, a throttle plate with at least one throttle opening, an outlet plate with at least one outlet opening, wherein the flow guide elements are arranged spaced apart from one another, and wherein the at least one inlet opening, the at least one throttle opening and the at least one outlet opening are each arranged offset from one another in a spatial direction transverse to a central axis of the flow throttle. Such a throttle can also be referred to as a turbulence throttle, since multiple flow reversals for the fluid flow are brought about by the flow guide elements and these flow reversals bring about a turbulent fluid flow.

[0005] The use of turbulence restrictors makes it possible to generate a significant pressure difference, which allows precise pressure difference measurement while maintaining a low installation space requirement. This applies in particular when comparing the installation space requirement of a turbulence restrictor with the installation space requirement of a laminar flow element.

[0006] The function of the turbulence restrictor is based on the fact that the fluid flow changes direction several times, in particular at least twice, while passing through the turbulence restrictor and thus undergoes several changes of flow direction, so that a desired significant pressure drop can be achieved across the turbulence restrictor.

[0007] For this purpose, at least two, preferably three, flow guide elements are arranged in the turbulence restrictor, each of which is penetrated by one or more recesses. The recesses of these adjacently arranged flow guide elements are arranged and configured in such a way that it is ensured that in a projection plane oriented transversely to the main flow direction of the fluid mass flow, in particular transversely to the central axis of the turbulence restrictor, there is no overlap between the projections of the recesses of the adjacently arranged flow guide elements.

[0008] According to the design of the flow-guiding element and according to the fluid pressure provided at the supply connection, the fluid flow flows through the recessed portion (entry hole and / or throttling hole and / or outlet hole) of the flow-guiding element (entry plate and / or throttling plate and / or outlet plate) at a speed lower than the speed of sound (subcritical flow mode) or at a speed higher than the speed of sound (supercritical flow mode). Turbulence throttles operating under subcritical flow mode require slightly more installation space. In contrast, turbulence throttles operating under supercritical flow mode can be constructed more compactly. According to the prescribed use of the mass flow regulator (into which the turbulence throttle should be integrated), the following design of the turbulence throttle should be provided, in which either a subcritical flow mode or a supercritical flow mode exists over the entire prescribed mass flow-regulation range.

[0009] For example, such a flow throttle can be arranged in a working channel of a mass flow regulator. In the working channel, the flow throttle causes a pressure drop, which is related to the fluid mass flow and caused by turbulence in the fluid flow, wherein the fluid flow extends between an input connection of the working channel and a working connection of the working channel. By measuring the pressure difference caused by the pressure drop, the mass flow of the fluid flowing through the working channel can be inferred using a suitable calculation model. Optionally, the pressure difference signal generated directly by the pressure sensor assembly can be provided to a control device, in which the fluid mass flow is calculated, or a plurality of discrete pressure signals can be provided to the control device for further processing.

[0010] For example, the task of the control device can be to determine the pressure difference from the sensor signal of the pressure sensor assembly and the absolute pressure and temperature and to infer from this pressure difference the corresponding existing fluid mass flow in the working channel in which the turbulence restrictor arrangement is located, using a mathematical model. The determined fluid mass flow is then compared with a preset (set) fluid mass flow in the control device. From the possibly existing difference between the determined fluid mass flow and the preset fluid mass flow, one or more control signals are generated for a valve module, by means of which the fluid flow in the working channel can be influenced in order to minimize the determined difference.

[0011] Preferably, the control signal provided by the control device is converted in the valve module in such a way that the throttling effect of the valve module is adapted to the required fluid mass flow, wherein a closed control loop is ensured for the fluid mass flow output by the mass flow regulator at the working connection.

[0012] The combination of the valve module, the control device and the working channel equipped with the turbulence restrictor can be referred to as a mass flow regulator. Alternatively, a mass flow sensor designed to determine the mass flow of a fluid can also be realized with a turbulence restrictor without the valve module.

[0013] Depending on the design of the turbulence restrictor, it always has the same throttling characteristics regardless of the flow direction, so that, as an alternative to a fluid source that can provide a pressurized fluid, a fluid source that can provide a negative pressure can also be connected to the supply connection of the mass flow regulator. However, if possible, the valve module may need to be adapted in relation to the fluid source.

[0014] Advantageous developments of the invention are the subject matter of the dependent claims.

[0015] Preferably, the at least one inlet opening, the at least one throttling opening and the at least one outlet opening are arranged offset relative to one another without overlapping in a projection plane oriented transversely to the central axis. This ensures that each gas molecule of the fluid flow inevitably undergoes a plurality of changes in flow direction required to ensure a high measurement accuracy for the differential pressure measurement. Due to the offset arrangement between the at least one inlet opening and the at least one throttling opening or between the at least one throttling opening and the at least one outlet opening, none of the gas molecules can pass through the turbulence restrictor on a flow path oriented parallel to the central axis of the working channel.

[0016] Advantageously, the inlet plate has a plurality of inlet openings which are radially spaced from the center axis and / or the throttle openings of the throttle plate are oriented coaxially to the center axis and / or the outlet plate has a plurality of outlet openings which are radially spaced from the center axis.

[0017] In the improved scheme of the present invention, it is arranged that the total cross-sectional area of ​​the inlet hole is equal to or greater than the cross-sectional area of ​​the throttle hole, and / or the cross-sectional area of ​​the throttle hole is equal to or greater than the total cross-sectional area of ​​the outlet hole. The total cross-sectional area refers to a cross-sectional area obtained by adding all the cross-sectional areas of the inlet hole or the outlet hole, and the cross-sectional area is compared with the cross-sectional area of ​​the throttle hole (preferably a single throttle hole). If the total cross-sectional area of ​​the inlet hole and / or the outlet hole is equal to the cross-sectional area of ​​the throttle hole, under the additional premise that the inlet plate has the same spacing relative to the throttle plate as the spacing of the outlet plate relative to the throttle plate, it can be considered that the throttling effect of the turbulent throttle is independent of the flow direction. If such flow direction independence is not required, it can be arranged that the total cross-sectional area of ​​the inlet hole is larger than the cross-sectional area of ​​the throttle hole. In addition or alternatively, it can be arranged that the total cross-sectional area of ​​the outlet hole is smaller than the cross-sectional area of ​​the throttle hole. Thus, in the case of the same fluid flow, the throttling effect of the turbulent throttle is enhanced compared to the turbulent throttle that is independent of the flow direction and thus the pressure difference is increased.

[0018] In another design of the present invention, it is provided that the throttle plate is constructed as a disk, the disk is penetrated by the throttle hole from the front circular surface to the rear circular surface, and the front annular flange extends in the axial direction from the front circular surface, the front annular flange is constructed for the surface contact of the inlet plate, and / or the rear annular flange extends in the axial direction from the rear circular surface, the rear annular flange is constructed for the surface contact of the outlet plate. Therefore, in addition to the throttling function determined by the throttle hole and its arrangement relative to the inlet hole of the inlet plate and / or the outlet hole of the outlet plate, the throttle plate also has another function, which is to ensure the preset spacing of the inlet plate and / or the outlet plate. For this purpose, the throttle plate has a base body of a disk-shaped structure, which can also be described as a cylindrical section with a throttle hole arranged in the center. The front annular flange can extend in the axial direction from the front circular surface of the base body, and the front annular flange is constructed with an end face facing away from the base body for contact with the inlet plate. The rear annular flange can extend in the axial direction starting from the rear circular surface of the base body, the rear annular flange being configured with an end face facing away from the base body for contact with the outlet plate. Preferably, the inner diameter of the front annular flange and / or the inner diameter of the rear annular flange is selected so that there is no need to worry about a negative influence on the fluid flow between the inlet plate and the throttle plate or between the throttle plate and the outlet plate.

[0019] It is expedient if all inlet openings are formed at the inlet plate at the same angular spacing with the same hole diameter and at the same radial spacing from the central axis, and / or all outlet openings are formed at the outlet plate at the same angular spacing with the same hole diameter and at the same radial spacing from the central axis. A symmetrical distribution of the fluid flow provided at the supply connection with respect to the central axis of the working channel is thereby ensured by the inlet plate and / or the outlet plate, so that a favorable flow behavior for the fluid flow occurs in the turbulence restrictor. Compared to an asymmetrical distribution of the fluid flow provided at the supply connection, a more stable profile for the differential pressure measurement results.

[0020] Preferably, it is provided that the axial extension of the throttle opening along the central axis corresponds to 2 to 10 times the axial extension of the inlet opening and / or 2 to 10 times the axial extension of the outlet opening.

[0021] Advantageously, the turbulence restrictor comprises an inlet plate, a throttle plate and an outlet plate, and the inlet plate, the throttle plate and the outlet plate are arranged in a throttle sleeve having an outer diameter corresponding to the inner diameter of the working channel, thereby forming a single assembly that can be independently manufactured, installed and inspected. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] An advantageous embodiment of the invention is shown in the drawings.

[0023] Figure 1 shows a schematic cross-sectional view of a flow restrictor configured as a turbulence restrictor with an inlet plate, a throttle plate, and a discharge plate;

[0024] Figure 2 Show according to Figure 1 a top view of the access plate; and

[0025] Figure 3 Show according to Figure 1 Top view of the throttle plate. DETAILED DESCRIPTION

[0026] Figure 1 The flow restrictor shown in the figure, called turbulence restrictor 201, is constructed as a separate assembly which can be installed independently and checked for its functionality. The turbulence restrictor 201 comprises a tubular throttling sleeve 203 which is constructed rotationally symmetrically to the central axis 202 and extends along the central axis 202 purely by way of example.

[0027] The outer surface 204 of the throttle sleeve 203 is divided purely by way of example into three sections adjacent to one another along the central axis 202, namely a first guide section 205, a fluid section 206 and a second guide section 207. Here, the first guide section 205 has a first outer diameter 231 and the second guide section 207 has a second outer diameter 232, which are preferably identical. The fluid section 206 arranged between the first guide section 205 and the second guide section 207 has a third outer diameter 233, which is smaller than the outer diameters 231 and 232 of the two guide sections 205, 207.

[0028] When the turbulence throttle 201 is installed in a working channel 241 of a mass flow regulator, not shown in detail, which is only schematically shown and is constructed as a cylindrical hole, the fluid section 206 and the working channel 241 form an annular channel 242, at which the fluid pressure present in the working channel 241 downstream of the turbulence throttle 201 can be determined, for example, by means of a pressure sensor not shown.

[0029] The cutout 208 of the throttle sleeve 203, which is designed rotationally symmetrically to the central axis 202, can be divided into an inflow section 209, a retaining section 210 and an outflow section 211. In this case, the inflow section 209 and the outflow section 211 have a diameter greater than the retaining section 210. Purely by way of example, it is provided that both the inflow section 209 and the outflow section 211 are each designed to widen slightly conically from the retaining section 210 to the inflow opening 212 or to the outflow opening 213. By way of example, the turbulence throttle 201 is provided with a turbulence throttle according to Figure 1 The illustration shows a through-flow of a fluid flowing from left to right, wherein a through-flow in the opposite direction can also be provided.

[0030] A plurality of flow guide elements 214, 215, 216 are arranged in the inflow section 209, by means of which the desired turbulence throttling function can be brought about when a gaseous fluid flows through the turbulence throttling device 201. Starting from the inflow opening 212, an inlet plate 214, a throttle plate 215 directly adjacent to the inlet plate in the axial direction along the center axis 202, and an outlet plate 216 directly adjacent to the throttle plate 215 in the axial direction along the center axis 202 are arranged in the inflow section 209.

[0031] As from Figure 1 and Figure 2As can be seen from the illustration of , the inlet plate 214 is designed in the shape of a disk and as a plane-parallel plate and has a plurality of inlet openings 217 which are arranged purely by way of example at constant angular distances relative to one another on a common pitch circle 220. By way of example, the inlet plate 214 can be made of a metal sheet which is provided with the inlet openings 217 by a laser cutting process or an etching process. Alternatively, the inlet plate can also be produced from a plastic material, in particular by a plastic injection molding process.

[0032] It is preferably provided that the inlet plate 214 and the outlet plate 216 are designed to be identical in structure.

[0033] Compared to the inlet plate 214 and the outlet plate 216, the throttle plate 215 has a significantly greater axial extension along the central axis 202. Functionally, the throttle plate 215 can be divided into a throttle disk 221 and a spacer ring 222 located in front and a spacer ring 223 located behind. The throttle disk 221 is designed in annular shape and has an unindicated outer diameter, which is slightly smaller than the inner diameter of the inflow section 209, which is also not indicated. The throttle disk 221 is provided with exactly one throttle opening 218, which is arranged coaxially with the outer diameter of the throttle disk 221. Purely by way of example, the throttle opening 218 is designed in a circular shape.

[0034] As from Figure 1 As can be seen from the illustration of , the throttle disk 221 has an axial extension along the center axis 202, which corresponds approximately to 7 times the axial extension of the inlet plate 214 or the outlet plate 216. At the mutually opposite axial end faces 224, 225, annularly configured spacer rings 222, 223 respectively protrude from the throttle disk 221, which serve as axial spacers for the inlet plate 214 and the outlet plate 216. The spacer rings 222, 223 each have an unspecified inner diameter, which is selected so that the inlet opening 217 of the inlet plate 214 and the outlet opening 219 of the outlet plate 216 are not covered. On the contrary, the spacer rings 222, 223 are only provided for the spaced arrangement of the inlet plate 214 and the outlet plate 216 and have no significant effect on the throttling effect of the turbulence throttle 201 described in more detail below.

[0035] The task of the retaining section 210 (which has a slightly smaller inner diameter than the subassembly consisting of the inlet plate 214, the throttle plate 215 and the outlet plate 216) is only to axially support the subassembly and also has no significant effect on the throttling effect of the turbulence restrictor 201 described in more detail below.

[0036] The outflow section 211 has substantially the same axial extension along the central axis as the inflow section 209 and serves to calm the fluid flow after passing through the above-mentioned flow guide elements (inlet plate 214 , throttle plate 215 , outlet plate 216 ).

[0037] Furthermore, radial holes 226 are formed in outflow section 211 , which ensure fluid communication between outflow section 211 and the annular channel between fluid section 206 and working channel 241 and thus enable tapping of the fluid pressure present in outflow section 211 for differential pressure measurement.

[0038] As from Figure 2 As can be seen from the diagram of , the projection 227 of the throttle hole 218 onto the inlet plate 214 does not overlap with the inlet hole 217. This ensures that the fluid, in particular the compressed air flow or the process gas flow, flowing through the turbulence restrictor 201 undergoes multiple reversals of its flow direction. This causes the desired turbulent flow in the turbulence restrictor 201.

[0039] The advantage of this turbulent flow is that the compactly designed turbulence restrictor 201 can realize differential pressure measurement, in which the pressure value upstream or before the turbulence restrictor 201, especially the pressure value in the area of ​​the inflow opening 212, can be significantly different from the pressure value downstream or after the turbulence restrictor 201, especially the pressure value at the radial hole 226, so that accurate differential pressure measurement can be realized. From this differential pressure measurement, the fluid mass flow through the turbulence restrictor 201 can be inferred with high accuracy.

Claims

1. A flow throttle (201) for a mass flow regulator, the mass flow regulator being configured for regulating a fluid mass flow, the flow throttle having at least two flow guide elements (214, 215, 216), the flow guide elements being from the following group: an inlet plate (214) with at least one inlet opening (217), a throttle plate (215) with at least one throttle opening (218), an outlet plate (216) with at least one outlet opening (219), wherein: The guide elements (214, 215, 216) are arranged spaced apart from each other, and wherein the at least one inlet opening (217), the at least one throttling opening (218) and the at least one outlet opening (219) are arranged offset from each other in a spatial direction transverse to a central axis (202) of the flow throttle (201).

2. The flow restrictor (201) according to claim 1, characterized in that: The at least one inlet opening (217), the at least one throttle opening (218) and the at least one outlet opening (219) are arranged offset relative to one another without overlapping in a projection plane oriented transversely to the center axis (202).

3. The flow restrictor (201) according to claim 1 or 2, characterized in that: The inlet plate (214) has a plurality of inlet holes (217) which are radially spaced from the center axis (202), and / or the throttle hole (218) of the throttle plate (215) is oriented coaxially with the center axis (202), and / or the outlet plate (216) has a plurality of outlet holes (219) which are radially spaced from the center axis (202).

4. The flow restrictor according to claim 3, characterized in that The total cross-sectional area of ​​the inlet holes (217) is equal to or greater than the cross-sectional area of ​​the throttle holes (218), and / or the cross-sectional area of ​​the throttle holes (218) is equal to or greater than the total cross-sectional area of ​​the outlet holes (219).

5. The flow restrictor according to any one of claims 1 to 4, characterized in that: The throttle plate (215) is constructed as a disk (221), which is penetrated by the throttle hole (218) from the front circular surface (224) to the rear circular surface (225), and a front annular flange (222) extends in the axial direction from the front circular surface (224), the front annular flange is constructed for planar contact with the inlet plate (214), and / or a rear annular flange (223) extends in the axial direction from the rear circular surface (225), the rear annular flange is constructed for planar contact with the outlet plate (216).

6. The flow restrictor (201) according to claim 3 or 4, characterized in that: All inlet holes (217) are configured at the inlet plate (214) at the same angular spacing with the same hole diameter and at the same radial spacing from the center axis (202), and / or all outlet holes (219) are configured at the outlet plate (216) at the same angular spacing with the same hole diameter and at the same radial spacing from the center axis (202).

7. A flow restrictor (201) according to any one of the preceding claims, characterized in that The axial extension of the throttle opening (218) along the center axis (202) corresponds to 2 to 10 times the axial extension of the inlet opening (217) and / or 2 to 10 times the axial extension of the outlet opening (219).

8. A flow restrictor (201) according to any one of the preceding claims, characterized in that The inlet plate (214), the throttle plate (215) and the outlet plate (216) are arranged in a throttle sleeve (203) extending along the central axis (202).

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