Turbine flowmeter

Abstract

The utility model provides a turbine flowmeter. The turbine flowmeter comprises a main body, a rotating shaft, a first turbine and a swirler, an accommodating cavity is formed in the main body; the rotating shaft is positioned in the accommodating cavity and is rotationally connected with the main body; the first turbine is arranged on the rotating shaft, and the first turbine is located in the containing cavity. The swirler is arranged in the containing cavity and located on the side, close to the fluid inlet, of the first turbine. A fluid entering the accommodating cavity from the fluid inlet forms a pre-swirling flow when passing through the swirler; wherein the fluid has a first flow speed, and the pre-rotational flow faces the rotation direction of the first turbine; a pre-swirling flow flows through the first turbine and drives the first turbine to rotate. The utility model has the technical effects that the design is reasonable, and stronger steering force and subsequent turbines can be provided for the first turbine, so that the first turbine and the whole flow meter can still be smoothly started at a lower flow speed.

Description

Technical Field

[0001] The utility model belongs to the technical field of flow measurement, and in particular relates to a turbine flow meter. Background Art

[0002] The turbine flowmeter is a commonly used flow measurement instrument, which uses the relationship between the rotation speed of the turbine in the fluid and the fluid flow rate to measure the volume flow of the fluid. That is, the turbine flowmeter uses the relationship between the rotation speed of the turbine and the flow rate of the fluid to measure the volume flow of the fluid. The speed signal is converted into an electrical signal by the sensor, and processed and displayed by the electronic display instrument. Turbine flowmeters are widely used in the industrial field and have the advantages of wide measurement range, high accuracy and simple structure.

[0003] The current turbine flowmeter has the following technical problems:

[0004] At very low flow rates, the turbine will not start or will start very slowly due to static friction (or inertia). Utility Model Content

[0005] The utility model aims to solve at least one of the technical problems existing in the prior art and provides a new technical solution for a turbine flowmeter.

[0006] According to one aspect of the utility model, a turbine flowmeter is provided, comprising:

[0007] A main body, wherein a receiving cavity is formed inside the main body, and a fluid inlet is provided on the main body;

[0008] A rotating shaft, the rotating shaft is located in the accommodating cavity and is rotatably connected to the main body;

[0009] a first turbine, the first turbine being disposed on the rotating shaft and located in the accommodating chamber;

[0010] A swirler, the swirler is disposed in the accommodating chamber and is located on a side of the first turbine close to the fluid inlet;

[0011] The fluid entering the accommodating chamber from the fluid inlet forms a pre-swirling flow when passing through the swirler; wherein the fluid has a first flow velocity, and the pre-swirling flow is directed toward the rotation direction of the first turbine;

[0012] The pre-swirled flow flows through the first turbine and drives the first turbine to rotate.

[0013] Optionally, the turbine flowmeter further comprises a second turbine;

[0014] The second turbine is disposed on the rotating shaft, the second turbine is located on a side of the first turbine away from the fluid inlet, and there is a preset distance between the first turbine and the second turbine;

[0015] When the pre-swirling flow flows through the first turbine and the second turbine in sequence, the rotation direction of the first turbine is the same as the rotation direction of the second turbine.

[0016] Optionally, the first turbine includes a plurality of first blades spaced apart along the circumferential direction; and the second turbine includes a plurality of second blades spaced apart along the circumferential direction.

[0017] Optionally, the number of the first blades is different from the number of the second blades.

[0018] Optionally, the difference between the number of the first blades and the number of the second blades is at least 1.

[0019] Optionally, the first turbine and the second turbine have the same geometric dimensions.

[0020] Optionally, an outlet metal angle of the first blade is the same as an outlet metal angle of the second blade.

[0021] Optionally, the relative speed between the first turbine and the second turbine is the same.

[0022] Optionally, the number of the first blades and the number of the second blades differ by 1.

[0023] Optionally, when the fluid flows in the accommodating chamber and flows through the first turbine and the second turbine in sequence, each of the first blades and each of the second blades are staggeredly distributed.

[0024] A technical effect of the utility model is:

[0025] In the embodiment of the present application, the cyclone is arranged in the accommodating chamber and is located on the side of the first turbine close to the fluid inlet. The fluid entering the accommodating chamber from the fluid inlet forms a pre-swirling flow when passing through the cyclone; the pre-swirling flow flows through the first turbine and drives the first turbine to rotate.

[0026] Therefore, by arranging a cyclone upstream of the first turbine, the water flow is turned into one direction by the cyclone to enhance the torque of the first turbine and overcome the resistance, thereby providing the first turbine with a stronger turning force so that the first turbine can still be started smoothly at a lower flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of a turbine flowmeter with a single turbine;

[0028] Figure 2It is a cross-sectional schematic diagram of a turbine flowmeter with a single turbine structure;

[0029] Figure 3 It is a velocity triangle schematic diagram of a turbine flowmeter with a single turbine structure;

[0030] Figure 4 It is a schematic diagram of the velocity triangle of a turbine flowmeter with a single turbine structure under the action of a cyclone according to an embodiment of the utility model;

[0031] Figure 5 It is a structural schematic diagram of an existing turbine flowmeter with a counter-rotating twin-turbine structure;

[0032] Figure 6 A schematic diagram of a velocity triangle of an existing turbine flowmeter with a reverse twin-turbine structure under the action of a cyclone;

[0033] Figure 7 It is a structural schematic diagram of a turbine flowmeter with a twin-turbine structure rotating in the same direction according to the second embodiment of the utility model;

[0034] Figure 8 It is a schematic diagram of the velocity triangle of the turbine flowmeter with a co-rotating twin-turbine structure under the action of a cyclone according to the second embodiment of the utility model.

[0035] In the figure: 1, main body; 101, accommodating chamber; 2, rotating shaft; 31, first turbine; 32, second turbine; 33, third turbine. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0037] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0038] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0039] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0040] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] According to one aspect of the present invention, see Figures 1 to 4 , a turbine flowmeter is provided, comprising:

[0042] A main body 1, wherein a receiving cavity 101 is formed inside the main body, and a fluid inlet is provided on the main body 1; the fluid inlet is provided along the axial direction of the main body;

[0043] A rotating shaft 2, the rotating shaft 2 is located in the accommodating cavity 101, and the rotating shaft 2 is rotatably connected to the main body 1;

[0044] A first turbine 31, wherein the first turbine 31 is disposed on the rotating shaft 2 and is located in the accommodating chamber 101;

[0045] a swirler (not shown in the figure), the swirler is arranged in the accommodating chamber 101 and is located on a side of the first turbine 31 close to the fluid inlet;

[0046] The fluid entering the accommodating chamber 101 from the fluid inlet forms a pre-swirling flow when passing through the swirler; wherein the fluid has a first flow velocity, and the pre-swirling flow is oriented in the rotation direction of the first turbine 31, that is, the rotation direction of the pre-swirling flow is opposite to the rotation direction of the first turbine 31;

[0047] The pre-swirled flow flows through the first turbine 31 and drives the first turbine 31 to rotate.

[0048] In the embodiment of the present application, the cyclone is arranged in the accommodating chamber and is located on the side of the first turbine close to the fluid inlet. The fluid entering the accommodating chamber from the fluid inlet forms a pre-swirling flow when passing through the cyclone; the pre-swirling flow flows through the first turbine and drives the first turbine to rotate.

[0049] Therefore, a cyclone is arranged upstream of the first turbine, and the water flow is diverted into one direction by the cyclone to enhance the torque of the first turbine and overcome the resistance, thereby providing a stronger steering force for the first turbine, so that the first turbine can still be started smoothly at a lower flow rate.

[0050] Alternatively, see Figure 7 and Figure 8 , the turbine flowmeter further comprises a second turbine 32;

[0051] The second turbine 32 is disposed on the rotating shaft 2, and the second turbine 32 is located on a side of the first turbine 31 away from the fluid inlet, and there is a preset distance between the first turbine 31 and the second turbine 32;

[0052] When the pre-swirling flow flows through the first turbine 31 and the second turbine 32 in sequence, the rotation direction of the first turbine 31 is the same as the rotation direction of the second turbine 32 .

[0053] In the above embodiment, while the pre-swirl enhances the torque of the first turbine and exceeds the resistance, since the rotation direction of the first turbine is the same as the rotation direction of the second turbine, the turbine flowmeter has lower parasitic losses, thereby improving the measurement accuracy. At the same time, the flow rate flowing into the second turbine is very similar to the flow rate flowing out of the first turbine, and the angle of attack is very small, which avoids the large losses associated with the flow separation of the fluid and also reduces the viscous resistance loss, thereby reducing the loss and helping to further improve the accuracy.

[0054] Optionally, the first turbine 31 includes a plurality of first blades spaced apart along the circumferential direction; and the second turbine 32 includes a plurality of second blades spaced apart along the circumferential direction.

[0055] Optionally, the number of the first blades is different from the number of the second blades.

[0056] In the above embodiment, when the two rotors (i.e., the first turbine and the second turbine) rotate in the same direction, the downstream rotor (second turbine) blades may be submerged in the wake of the upstream rotor (first turbine) blades, which will affect the speed of the rotor of the second turbine. This relative position may produce intermittent acceleration and deceleration of the downstream rotor and cause measurement errors. The difference in the number of the first blades and the number of the second blades can well avoid the above situation, ensure the effectiveness of the turbine flowmeter with a twin-turbine structure rotating in the same direction, and avoid measurement errors.

[0057] Optionally, the difference between the number of the first blades and the number of the second blades is at least 1. This better avoids the possibility that the downstream rotor (second turbine) blades are submerged in the wake of the upstream rotor (first turbine) blades, thereby ensuring the speed of the rotor of the second turbine.

[0058] Optionally, the geometric dimensions of the first turbine 31 and the second turbine 32 are the same, which can better ensure that the losses of the first turbine and the second turbine are the same, and help reduce the losses of the fluid flowing through the first turbine and the second turbine.

[0059] Optionally, an outlet metal angle of the first blade is the same as an outlet metal angle of the second blade.

[0060] In the above embodiment, the outlet metal angle is the fluid flow direction relative to the turbine blade, which usually deviates from the metal angle, depending on the blade characteristics and viscous loss. This deviation is called the deviation angle in turbomachinery and is usually very small. The outlet metal angle of the first blade is the same as the outlet metal angle of the second blade, which helps to further ensure that the first turbine and the second turbine have substantially the same loss, helps to reduce viscous drag loss, and thus further improves accuracy.

[0061] Optionally, the relative speeds of the first turbine 31 and the second turbine 32 are the same, which can effectively reduce the loss of the first turbine and the second turbine and ensure the measurement accuracy.

[0062] Optionally, the number of the first blades and the number of the second blades differ by 1. This can better prevent the downstream rotor (second turbine) blades from being submerged in the wake of the upstream rotor (first turbine) blades, thereby ensuring the speed of the rotor of the second turbine and improving the measurement accuracy.

[0063] Optionally, when the fluid flows in the accommodating chamber 101 and sequentially flows through the first turbine 31 and the second turbine 32 , each of the first blades and each of the second blades are staggeredly distributed.

[0064] In the above embodiment, it is possible to effectively prevent the downstream rotor (second turbine 32) blades from being submerged in the wake of the upstream rotor (first turbine) blades, thereby ensuring the speed of the rotor of the second turbine 32 and reducing measurement errors.

[0065] In the present application, the velocity triangles of a turbine flowmeter with a single turbine structure, a turbine flowmeter with a twin turbine structure rotating in the same direction, and a turbine flowmeter with a twin turbine structure rotating in the opposite direction are analyzed in order to understand why the turbine flowmeter provided in the embodiment of the present application can still successfully start the first turbine at a lower flow rate.

[0066] It should be noted that, for a turbine flowmeter with a single turbine structure and an axial inlet flow, there is a linear relationship between the volume flow and the rotation speed of the rotor (ie, the first turbine).

[0067] In the following analysis, we use the recognized methods and symbols in the field of turbomachinery, and use the concept of velocity triangle to describe the relationship between the turbine rotor and volume flow. Here, we colloquially refer to the turbine as the rotor, blades, or cascades commonly seen in turbomachinery literature.

[0068] The flow rate includes the absolute flow rate seen in a fixed reference frame, and the relative flow rate seen from the turbine blades. It is the relative speed that drives the turbine to move. All variables in this analysis are based on standard SI units. At the same time, the letters in the following formulas are annotated as follows:

[0069] ω: turbine speed;

[0070] R: The radius of the blade from the center of rotation;

[0071] T: torque of the fluid medium acting on the turbine blades;

[0072] The work applied by the turbine to the fluid flow, per unit mass flow rate;

[0073] V: fluid velocity in absolute coordinate system;

[0074] V x : The axial component of V, using the subscript x;

[0075] V t : tangential component of V, using subscript t;

[0076] W: flow velocity relative to the turbine blade cascade;

[0077] U: tangential wheel speed, equal to radius R multiplied by speed w;

[0078] α: absolute fluid velocity angle between the fluid and the axial direction;

[0079] β: relative fluid velocity angle between the fluid and the axial direction;

[0080] 1: represents the flow station at the inlet of a single or first turbine cascade;

[0081] 2: flow station representing a single or first turbine cascade outlet;

[0082] 3: flow station representing the inlet of the second counter-rotating turbine cascade;

[0083] 4: flow station representing the outlet of the second counter-rotating turbine cascade;

[0084] 3′: flow station representing the inlet of the second co-rotating turbine cascade;

[0085] 4': represents the flow station at the outlet of the second co-rotating turbine cascade.

[0086] For turbine flowmeters with a single turbine structure, Figure 2 is the cross section of a single turbine, Figure 3 is the velocity triangle upstream and downstream of the turbine blade in the prior art, Figure 4 is the velocity triangle upstream and downstream of the turbine blade under the action of the swirler. For simplicity, without losing the generality of the principle, we study the cylindrical plane at high AA in the blade, and expand it to a two-dimensional plane, that is, obtain the velocity triangle, see Figure 3 and Figure 4 .

[0087] See also Figure 3 , using a well-known theorem in turbomachinery, it is stated that the action of the fluid medium applied to the turbine can be described by the following "Euler turbine" equation:

[0088]

[0089] In the current model, it is assumed that the turbine cross-sectional radius is constant, R, and the turbine inlet and outlet tangential velocities are the same, then:

[0090] U1=U2=ωRU1=U2=ωR (2)

[0091] In the current analysis, the fluid enters the turbine blade row axially, and the tangential component of the absolute velocity at station 1 is zero. Therefore:

[0092] V 1t =0 (3)

[0093]

[0094] In the above formula, Q is the volume flow rate entering the turbine; A is the cross-sectional area of ​​the fluid flowing in the accommodating cavity.

[0095] For simplicity, without losing the general applicability of the present analysis, we will assume that the flow cross-sectional area A remains constant when entering and leaving the turbine blade row. Then the axial component of the absolute fluid velocity at the turbine outlet should be equal to the axial component at the turbine outlet, then:

[0096]

[0097] Here we consider the ideal case of zero loss and assume that the outflow angle of the turbine blade is the same as the outflow metal flow angle of the turbine blade, then, V 2x 、V 2t The following relationship is formed between ω, R and β:

[0098]

[0099] Combining equations (1) to (6), assuming but:

[0100]

[0101] or,

[0102]

[0103] This is the well-known linear relationship between volume flow and turbine speed.

[0104] It should be noted that formula (1) assumes that the flow into the first turbine is axial. In fact, the structure upstream of the first turbine is usually a flow straightener to ensure that the flow is axial and uniform.

[0105] Further, see Figure 4 Under the action of the swirler, the swirler provides a pre-swirling flow for the first turbine, and the pre-swirling flow provides an enhanced torque for the rotor (ie, the first turbine) to overcome the resistance. Intuitively, the pre-swirling flow should be in the direction of rotation of the first turbine.

[0106] Repeat the above equation, except that V at the first turbine inlet is 1t =-V 1x In addition to tanα1, note that V 1t Relative to V 2t Pointing downwards, we get the following result:

[0107]

[0108] Under the zero loss assumption, then:

[0109]

[0110] Therefore, we can conclude that for the same flow rate Q, the speed ω with pre-swirl is higher than without pre-swirl, as expected. On the contrary, if the pre-swirl direction is opposite, that is, α1 is negative, the speed ω will be slower, making it more difficult for the first turbine to start. In fact, in the special case where α1 = -β, ω will be zero and the first turbine will never move! This is an important conclusion that has implications for twin turbine configurations (counter-rotating or co-rotating).

[0111] Next, the velocity triangle of the turbine flowmeter with reverse twin turbine structure under the action of the cyclone, see Figure 5 and Figure 6 .

[0112] Repeat the turbine Euler equation analysis on turbine II (third turbine 33), assuming zero losses, then:

[0113]

[0114] So:

[0115]

[0116]

[0117] when When:

[0118]

[0119] Therefore, we can conclude that the pre-swirl actually has the opposite effect of starting turbine II (third turbine 33). ΙΙ will be zero.

[0120] In summary, the pre-swirl has opposite effects on the two rotors (ie, the first turbine and the third turbine 33) in a counter-rotating manner. In short, the pre-swirl is not suitable for a counter-rotating dual-rotor design at all.

[0121] For a turbine flowmeter with a twin-turbine structure rotating in the same direction, such as Figure 7 and Figure 8 As shown, the pre-swirl is effective when the turbine II' (second turbine 32) is cross-started, in a manner similar to that of the turbine I (first turbine 31), as shown in FIG. Figure 8 shown.

[0122] Assuming that there are no losses in the fluid flow, we have the following relationship between the flow rate on turbine II' (second turbine 32) and the turbine speed, which is the same as for turbine I (first turbine 31), namely:

[0123]

[0124] Therefore, when the static friction is difficult to overcome, pre-swirl is an effective technical means to quickly start the first turbine rotation at an extremely low flow rate, which is applicable to turbine flowmeters with a single turbine structure and turbine flowmeters with a twin turbine structure rotating in the same direction, but is ineffective for turbine flowmeters with a twin turbine structure rotating in the opposite direction.

[0125] Therefore, the turbine flowmeter provided in the present application is reasonably designed and can provide a stronger steering force for the first turbine so that the first turbine can still be started smoothly at a lower flow rate.

[0126] It should be noted that the above embodiments are merely exemplary embodiments used to illustrate the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A turbine flowmeter, characterized in that: include: A main body, wherein a receiving cavity is formed inside the main body, and a fluid inlet is provided on the main body; A rotating shaft, the rotating shaft is located in the accommodating cavity and is rotatably connected to the main body; a first turbine, the first turbine being disposed on the rotating shaft and located in the accommodating chamber; A swirler, the swirler is disposed in the accommodating chamber and is located on a side of the first turbine close to the fluid inlet; The fluid entering the containing chamber from the fluid inlet forms a pre-swirling flow when passing through the swirler; wherein the fluid has a first flow velocity; The pre-swirled flow flows through the first turbine and drives the first turbine to rotate.

2. The turbine flowmeter according to claim 1, characterized in that: Also included is a second turbine; The second turbine is disposed on the rotating shaft, the second turbine is located on a side of the first turbine away from the fluid inlet, and there is a preset distance between the first turbine and the second turbine; When the pre-swirling flow flows through the first turbine and the second turbine in sequence, the rotation direction of the first turbine is the same as the rotation direction of the second turbine.

3. The turbine flowmeter according to claim 2, characterized in that: The first turbine includes a plurality of first blades spaced apart in a circumferential direction; the second turbine includes a plurality of second blades spaced apart in a circumferential direction.

4. The turbine flowmeter according to claim 3, characterized in that: The number of the first blades is different from the number of the second blades.

5. The turbine flowmeter according to claim 4, characterized in that: The difference between the number of the first blades and the number of the second blades is at least 1.

6. The turbine flowmeter according to claim 5, characterized in that: The first turbine and the second turbine have the same geometrical dimensions.

7. The turbine flowmeter according to claim 6, characterized in that: An outlet metal angle of the first blade is the same as an outlet metal angle of the second blade.

8. The turbine flowmeter according to claim 2, characterized in that: The relative speed between the first turbine and the second turbine is the same.

9. The turbine flowmeter according to claim 3, characterized in that: The number of the first blades and the number of the second blades differ by 1.

10. The turbine flowmeter according to claim 3, characterized in that: When the fluid flows in the accommodating chamber and sequentially flows through the first turbine and the second turbine, each of the first blades and each of the second blades are staggeredly distributed.

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