JP4155504B2 - Flow meter and its impeller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flowmeter having an inlet and an outlet, and particularly relates to a flowmeter in which an impeller blade rotated by a fluid flow has a twisted shape about its central axis.
[0002]
[Prior art]
As shown in FIG. 18, a conventional flowmeter impeller 100 is a blade 113 having a constant twist angle that maintains the relationship shown in FIG. 18 from the fluid inflow side to the outflow side. By passing through the fluid, the fluid pushes around the blade surface that receives the pressure of the fluid, and the impeller rotates about the rotation axis. Since this rotational speed is proportional to the flow velocity, it has become a mechanism that adds a constant number with a display mechanism in analog form with a gear or the like, or digitally with a sensor or the like, converts it into an integrated flow rate value, and measures it. (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
Japanese Utility Model Publication No. 3-13690
[Problems to be solved by the invention]
However, in such an impeller having blades having a constant twist angle, the rotational force on the inflow side and the rotational force on the outflow side of the fluid are not equal. It acts, and the instrumental difference shows a positive tendency in a certain flow rate region (especially a small flow rate region) in the flow rate-instrument difference curve, that is, it is a cause of the instrumental difference where a peak appears. In addition, since the torsion angle is constant on the opposite surface that is not subjected to fluid pressure, the water flow twisted by the rotation of the blade causes a boundary layer to be generated on the surface of the blade, causing the peak to flow. It was the cause of the difference.
[0005]
This invention makes it a subject to provide the flowmeter which can suppress generation | occurrence | production of the instrument difference in which a peak appears.
[0006]
[Means for Solving the Problems and Effects of the Invention]
The present invention relates to a flow meter which is built in a flow meter having an inlet and an outlet, and is configured such that a blade of an impeller rotated by a fluid flow is twisted about its central axis, and the twist angle of the blade is constant. Rather, the twist angle changes from the middle of the blade so that it smoothly increases in a fixed relationship from the fluid inflow side to the outflow side, and the difference obtained by subtracting the torsion angle from the outflow side to the inflow side is , Characterized in that it comprises an impeller in the range of 4 ° to 7 ° .
[0007]
By doing so, the rotational force on the inflow side and the outflow side of the surface receiving the pressure of the fluid in the impeller is made substantially equal so that the difference in rotational force between the inflow side and the outflow side of the blade is reduced. Prevents or acts as a resistance, and tends to be a flat instrumental error without a peak.
[0008]
Further, the invention is such that the twist angle of the surface of the twisted blade on the side receiving pressure by the fluid is not constant, and the twist angle increases smoothly from the fluid inflow side to the outflow side in a constant relationship. The difference between the blade angle and the twist angle from the outflow side to the inflow side is within the range of 4 ° to 7 ° .
[0009]
Here, the instrumental difference of the peak can be improved by increasing the torsion angle of the surface on the side receiving the fluid pressure within the range of 4 ° to 7 ° .
[0010]
In addition, the twist angle of the surface of the twisted blade on the side opposite to the side that receives pressure by the fluid is not constant, changes from the middle of the blade, and the difference obtained by subtracting the twist angle on the inflow side from the outflow side is It is characterized by comprising an impeller within a range of 4 ° to 7 ° .
[0011]
In this way, by increasing the twist angle in the range of 4 ° to 7 ° only on the opposite surface that is not subjected to fluid pressure, the flow of fluid twisted by the rotation of the blades is not reduced. , Peak instrumental error can be improved.
[0012]
For further reference , the blade twist angle changes from the middle of the blade, and the difference between subtracting the twist angle from the outflow side to the inflow side is within the range of 4 ° to 7 °. It can be a folded impeller.
[0013]
In general, the manufacture of an impeller in which the twist angle of the impeller blade gradually changes from 4 ° to 7 ° from the inflow side and reaches the outflow side twist angle requires considerable man-hours and time, and is easy. is not. Therefore, for the purpose of facilitating the manufacture, the change of the twist angle is not made gradually, but an impeller whose blade changes only once at a certain position, in other words, an impeller in which the blade is bent into a "<" shape. Even when used, the effect of lowering the peak of the instrumental error can be sufficiently obtained.
[0014]
In addition, the twist angle can be changed in multiple stages on the blade, and when the twist angle is increased on the outflow side from the inflow side on the outflow side, the surface on the outflow side on the side receiving the fluid pressure and the opposite side The surface can have the same twist angle or can be different from each other.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the examples shown in the drawings.
FIG. 1 shows an example of a flow meter to which the present invention is applied. The flow meter 1 of this example includes a supplementary pipe 2 located on the upstream side of the water flow, and a lower case 3 combined therewith, and a fluid (generally water) extending from the inlet 4 to the outlet 5 across them. The flow path is formed. In the central part of the lower case 3, there is a rectifier 6 for a water flow guided substantially vertically upward, and a regulator 8 associated therewith, and a measuring chamber 7 is located above them.
[0016]
An impeller 10 is installed in the measuring chamber 7 so as to be rotatable about a vertical axis while being inserted into a vertical pivot shaft 9 fixed to the rectifier 6 with a slight gap from above. . Around the center line of the impeller 10, a plurality of blades 13 twisted with respect to the center line are formed integrally with the boss 12, and the blades 13 are spiral with the center line of the impeller 10 as the center. It is formed so as to be twisted along the surface. The fluid guided upward in the pipe line of the lower case 3 is rectified by the rectifier 6, hits the impeller 10 from below, and rotates the impeller 10 based on the twist of the vane 13, It passes in the axial direction, and then changes direction and flows out from the outlet 5 downstream.
[0017]
In the case of an electronic flow meter, the rotation of the impeller 10 is detected by an MR sensor or the like by a magnet built in the upper portion of the impeller 10 and replaced with an electric signal, and is integrated by an electronic counter 24. . The electronic counter 24 is housed in a water shielding case 20 and covered with an openable lid 18. The rectifier 6 located below the impeller 10 has a plurality of rectifying blades 19 extending radially from the vertical center line, and by adjusting one of these blades by a minute angle with respect to the vertical axis, The adjuster 8 finely adjusts the rotational speed of the impeller 10 by slightly changing the direction of the water flow hitting the blades 13 of the car 10, and is attached to the rectifier 6. In the case of a mechanical flow meter, the rotation of the impeller 10 is counted by a plurality of gears or the like via a mechanical rotation integrator.
[0018]
As shown in FIG. 2, the impeller 10 has a rotating shaft 11 provided with a boss 12 having a diameter larger than that of the rotating shaft 11 and smaller than that of the impeller 10, and the boss 12 has an axis of the rotating shaft 11. A plurality of (for example, six) blades 13 that are twisted with respect to each other are provided at equal intervals. As described above, the flow meter 1 having the impeller 10 receives the force of the water flow from the surface 14 on the side where the fluid of each of the plurality of blades 13 of the impeller 10 receives the force of the water flow. At the same time, it is configured to rotate around its axis, and the passage amount (this flow meter) is measured by adding a constant constant by a display mechanism.
[0019]
The central surface 13c of the plurality of blades 13 of the impeller 10 has a value obtained by subtracting the twist angle α on the inflow side from the twist angle α ′ from the outflow side in a range of 1 ° to 10 °. The twist angle is changed in the middle (see FIG. 2G). Regarding this change, the twist angle smoothly increases from the inflow side toward the outflow side in a constant relationship, and the twist angle increases and decreases to the target twist angle on the outflow side. In this case, a change that increases smoothly in a fixed relationship toward the outflow side disturbs the flow of water. It is desirable because it is not.
[0020]
2 shows a twist angle (both the angle formed with respect to the vertical line is the twist angle) on both the surface 14 on the side receiving the fluid pressure and the surface 15 on the opposite side to the surface receiving the fluid pressure. α)) is increased on the outflow side, the thickness of the blade 13 is constant, and the range of change in the twist angle is 1 ° to 10 °. Preferably, it can be set to 4 to 7 °. If the range of the twist angle is too small, it becomes difficult to obtain the effect of flattening the instrumental error. Conversely, if the range is too large, the component of the force that rotates the impeller 10 becomes too small, and therefore resistance on another side. The above range can be said to be preferable because (such as upward thrust force) is likely to occur.
[0021]
Further, as shown in FIG. 3, the twist angle may be increased in the range of 1 ° to 10 ° only on the surface 14 that receives the fluid pressure. Even in this case, a change that smoothly increases from the inflow side to the outflow side in a constant relationship, a change that increases and decreases the twist angle to the target twist angle on the outflow side, and a smooth change However, in this case, a change that increases smoothly in a fixed relationship toward the outflow side is preferable because it does not disturb the flow of water.
[0022]
Furthermore, as shown in FIG. 4, the twist angle may be increased in the range of 1 ° to 10 ° only on the opposite surface 15 that is not subjected to fluid pressure. In this case as well, a change that smoothly increases from the inflow side to the outflow side in a constant relationship, a change that increases and decreases the twist angle to the target twist angle on the outflow side, and a smooth change However, in this case, a change that increases smoothly in a fixed relationship toward the outflow side is preferable because it does not disturb the flow of water.
[0023]
Further, as shown in FIG. 5, the twist angle of the blade 13 changes from the middle of the blade, and the difference obtained by subtracting the twist angle from the outflow side to the inflow side is within a range of 1 ° to 10 °. It can be an impeller that is bent into the shape of “ku”.
[0024]
In the manufacture of the impeller, it is not easy to manufacture smoothly, so that the effect of the flat instrumental error described above is ensured while the change in the twist angle is made once from the viewpoint of facilitating the manufacture. It is the shape of the letter “ku”. The position where the twist angle is changed is preferably between the middle position from the inflow side to the outflow side of the impeller and the outflow side. Among these, it is good to change between the intermediate position which goes to the outflow side from the inflow side of an impeller to an outflow side.
[0025]
FIG. 6 illustrates a surface 14 (also referred to as a pressure acting surface) on the side of the blade 13 that receives fluid pressure and a surface 15 (also referred to as a non-pressure acting surface) opposite to the surface 14 on the side that receives fluid pressure. In both cases, the torsion angle is made larger on the outflow side than on the inflow side, and the torsion angles of the surfaces 14 and 15 on the outflow side are made different from each other.
[0026]
Further, FIG. 7 conceptually shows a form in which the twist angle on the outflow side is made the same and a form in which the torsion angle is made different in the case of using the “<” shaped blade 13. The change in the twist angle as described above may be formed over the entire length (d) of the radial dimension (protrusion dimension) of the blade, or may be a part of the total length (for example, half on the outer peripheral side). .
[0027]
FIG. 8 shows an example in which the twist angle of the blade 13 is changed to a plurality of stages, such as two stages, instead of a one-step change of the “<” shape.
[0028]
FIG. 9 shows that when the twist angle on the outflow side of the blade 13 is greatly changed from the inflow side, the twist angle between the pressure acting surface 14 and the pressure non-working surface 15 on the outflow side is the same (a), An example is shown in which the former is larger than the latter (b) and the latter is larger than the former (c).
[0029]
By changing the form of the blade 13 of the impeller 10 as described above, for example, as shown in FIG. 2, the instrumental error peak is hardly generated as shown in FIG. FIG. 11 shows changes in instrumental differences corresponding to those in FIG. 3, FIG. 12 in FIG. 4, and FIG. 13 in FIG. 5. The effect of flattening the instrumental differences is recognized to some extent. .
[0030]
The reason why such an effect occurs will be described below. However, this is only an estimation based on the experimental results, and the present invention is not affected by the appropriateness of this inference.
Regarding the rotation control of the impeller, now consider particles (points) P0 on the inflow side of arbitrary blades P0-Ph of an impeller having a height h as shown in FIG. In addition, the impeller assumes an ideal state with no resistance.
[0031]
The fluid particle (point) P0 at this point moves from P0 (0) to P0 (t) after t seconds. Further, the inflow side particle (point) F0 on the blade moves from F0 (0) to F0 (t) after t seconds.
The outflow side fluid particles (points) Ph move from Ph (0) to Ph (t) after t seconds. The outflow side particle (point) Fh on the blade moves from Fh (0) to Fh (t) after t seconds.
In this ideal state, a line connecting P0 (t) and Ph (t) (in this state, a straight line) and a line connecting F0 (t) and Fh (t) (in this state, a straight line) Will overlap. That is, there is no gap between the blade and the fluid after t seconds.
[0032]
Next, a state in which the blades are resistant will be considered in FIG.
Consider the movement of a fluid of a particle (point) Px having a height x from the bottom surface of the blade. The fluid particle Px at this point moves from Px (0) to Px (t) after t seconds. At this time, since the blade has resistance, Px (t) is at a position where the direction is changed by a ° in the opposite direction to the rotation direction. It can be seen that the angle a is a function that increases as x increases. For this reason, the line connecting P0 (t) and Ph (t) and the line connecting F0 (t) and Fh (t) (in this state, a straight line) do not overlap.
That is, a gap in the hatched portion is generated. As shown in FIG. 16, this is a resistance, and the portion that has fallen from the ideal state by the resistance T becomes an instrumental difference curve, so that the meter has a high peak value.
[0033]
Here, if the impeller of FIG. 17 is manufactured in which the twist angle of the blade is increased by b ° in the middle, the gap (hatched portion) is smaller than the blade having a constant twist angle, and the resistance T is small. It can be seen that a flat instrumental difference meter can be manufactured.
[0034]
Next, the surface of the blade on the side not receiving the fluid pressure, the C surface of FIG.
The flow of particles with the direction slightly changed from Px (0) to Px (t) affects the flow between the blades. Similarly, in the C plane, the direction of the flow is largely leftward on the outflow side of the blades. Changed flow.
At this time, if the C surface of the blade is manufactured with a blade having a constant helix angle, a contraction occurs at a portion Z that is zigzag hatched, and this contraction causes resistance and causes a peak. Therefore, a meter having no peak can be manufactured on the surface on which the pressure is not received by similarly changing the twist angle.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a flow meter to which the present invention is applied.
FIG. 2 is a diagram showing an example 1 of an impeller according to the present invention.
FIG. 3 is a diagram showing an example 2 of an impeller according to the present invention.
FIG. 4 is a diagram showing an example 3 of an impeller according to the present invention.
FIG. 5 is a diagram showing an example 4 of an impeller according to the present invention.
FIG. 6 is a diagram showing an example 5 of an impeller according to the present invention.
FIG. 7 is a diagram showing an example 6 of an impeller according to the present invention.
FIG. 8 shows an example 7 of an impeller according to the present invention.
FIG. 9 is a diagram showing an example 8 of an impeller according to the present invention.
FIG. 10 is a graph showing instrumental error when the impeller of FIG. 2 is used in comparison with a conventional one.
11 is a graph showing the instrumental difference when the impeller of FIG. 3 is used in comparison with the conventional one.
12 is a graph showing the instrumental difference when the impeller of FIG. 4 is used in comparison with the conventional one.
13 is a graph showing the instrumental difference when the impeller of FIG. 5 is used in comparison with the conventional one.
FIG. 14 is a diagram illustrating inference of a mechanism given to the fluid of the impeller of the present invention.
FIG. 15 is a view that continues from FIG. 14;
FIG. 16 is also a diagram subsequent to FIG.
FIG. 17 is a view subsequent to FIG. 16;
FIG. 18 is a diagram showing an example of a conventional impeller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flowmeter 4 Inlet 5 Outlet 7 Measuring chamber 9 Pivot shaft 10 Impeller 11 Rotating shaft 12 Boss 13 Blade 14 Pressure acting surface (pressure receiving surface)
15 Pressure non-operation surface (non-pressure-receiving surface)

Claims (4)

In a flow meter having a blade with a twisted shape radially extending from a central axis of an impeller that is built in a flow meter having an inlet and an outlet and rotates by a fluid flow, the twist angle of the blade is not constant, The twist angle changes from the middle of the blade so as to increase smoothly from the fluid inflow side to the outflow side in a constant relationship, and the difference obtained by subtracting the twist angle from the outflow side to the inflow side is 4 °. A flow meter comprising an impeller that is within a range of 7 ° to 7 ° . The twist angle of the surface of the twisted blade that receives pressure by the fluid is not constant, and the twist angle is increased in the middle of the blade so that the twist angle smoothly increases in a constant relationship from the fluid inflow side to the outflow side. A flowmeter characterized by comprising an impeller whose difference is obtained by changing the twist angle from the outflow side to the inflow side within a range of 4 ° to 7 ° . The twist angle of the surface of the twisted blade opposite to the side subjected to pressure by the fluid is not constant, and the twist angle smoothly increases in a constant relationship from the fluid inflow side to the outflow side. A flowmeter characterized by comprising an impeller that changes from the middle of a blade and the difference obtained by reducing the torsion angle from the outflow side to the inflow side is within a range of 4 ° to 7 ° . An impeller built in the flow meter according to any one of claims 1 to 3 .

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