JPH0317221Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a turbine-type flowmeter, and particularly to a turbine-type flowmeter that can prevent instrumental error from decreasing over time due to dust adhering to the inner wall of a flow path.

BACKGROUND ART In a conventional turbine flowmeter, for example, an impeller that rotates in accordance with the flow rate of fluid is provided in a flow path, and the flow rate is measured by measuring the rotational speed of the impeller. In the turbine flowmeter that measures the flow rate in this manner, a gap is provided between the tip of the impeller and the inner wall of the flow path so that the tip of the impeller does not come into contact with the inner wall of the flow path. This gap is provided so that there is no problem even if the impeller rotates with slight radial swing due to play in the impeller bearing and machining precision of the impeller, impeller shaft, etc. Further, the fluid passing through this gap does not pass through the blades of the impeller and generates no force to rotate the impeller, resulting in a loss. Therefore, when measuring fluid, the amount of fluid leaking through the gap between the impeller and the inner wall of the flow path is a major factor that affects the instrumental error of the flowmeter.

Another conventional example is to provide an annular groove recessed in the radial direction on the inner wall of the flow path in order to reduce the loss caused by the fluid flowing through the gap between the impeller and the inner wall of the flow path. There is a turbine-type flowmeter configured such that an impeller rotates in accordance with the flow rate flowing in a flow path with the tip of the impeller inserted into the flow path to measure the flow rate. In the case of this flowmeter, fluid flows into the groove when measuring low flow rates, but when measuring medium to high flow rates, the fluid does not flow into the groove and the groove becomes a dead area, and the fluid flow rate is measured without loss.

Problems to be solved by the invention However, in the former case, in the conventional turbine flowmeter with the above configuration, there is a gap between the tip of the impeller and the inner wall of the flow path, and fluid flowing through this gap leaks. The amount was not proportional to the increase/decrease in the fluid flow rate in the channel from low to high flow rate, and the instrumental error varied depending on the flow rate during low flow measurement, medium flow measurement, and high flow measurement. Further, since dust in the fluid adheres to the inner wall of the flow path, if the dust accumulates on the inner wall of the flow path facing the impeller over time, the dust will close the gap between the impeller and the inner wall of the flow path. For this reason,
The amount of fluid leaking through the gap decreases over time. Therefore, there has been a drawback that the instrumental error of the flowmeter gradually changes depending on the amount of accumulated dust, making it difficult to accurately measure the flow rate over a long period of time.

In addition, in the case of the latter of conventional turbine flowmeters,
Since the inside of the groove becomes a dead area when measuring medium and high flow rates, dust tends to adhere to the inside of the groove. Therefore,
The drawback was that when medium to high flow rates were measured over a long period of time, dust would accumulate in the grooves and impede the rotation of the impeller. For this reason, conventional turbine-type flowmeters have disadvantages in that, when used for a long period of time, the instrumental error changes due to the accumulation of dust, making it difficult to measure the flow rate with high precision and resulting in poor durability.

Therefore, an object of the present invention is to provide a turbine flowmeter that eliminates the above-mentioned drawbacks.

Means and Effects for Solving the Problems The present invention provides an annular groove recessed in the radial direction of the flow path on the inner wall of the flow path, and the flow path is provided with a plurality of blades on the circumferential surface. An impeller is rotatably provided coaxially with the flow path so that the tips of the blades protrude into the groove, and the impeller rotates in accordance with the flow rate of the fluid to be measured. In a turbine flow meter that measures the flow rate of a measuring fluid, the groove is formed such that the width of the opening in the flow direction is larger than the width of the inner part thereof, and the inner wall of the flow path is connected to the inner wall of the groove. The upstream and downstream walls are sloped upward and downstream, respectively, to minimize fluctuations in instrumental error that can change over time due to dust adhesion, allowing accurate flow rate measurement over a long period of time. It is.

Embodiment FIG. 1 shows an embodiment of the turbine flowmeter according to the present invention. In FIG. 1, a turbine flowmeter 1 has a cylindrical main body 2. As shown in FIG. The main body 2 has a top flange 2a,
It has flanges 2b at both ends and a flow path 2c.
Upstream and downstream cone members 3 and 4 provided above and downstream of an impeller, which will be described later, are fitted and fixed to the inner periphery of the main body 2. Attached to the upper flange 2a of the downstream cone member 4 is a housing 5 having a count display section (not shown) that counts and displays the flow rate measured by the turbine flow meter 1.

Reference numeral 6 denotes an impeller, which is rotatably supported by a shaft 7 so as to rotate according to the flow rate of the fluid. The shaft 7 is rotatably supported at both ends by bearings 8 and 9. Reference numeral 10 is an oil reservoir chamber in which lubricating oil is stored. The lubricating oil in this oil reservoir chamber 10 is supplied to the bearings 8 and 9 by a lubricating oil supply mechanism 11. A dust prevention member 12 prevents dust in the fluid from entering the inner side of the downstream cone member 4 from the inner peripheral side of the impeller 6.

As shown in FIG. 2, an annular groove 13 recessed in the radial direction is provided on the inner wall 2d of the flow path of the main body 2.
The width of the opening in the flow direction of the groove 13 is the width of the inner part 1.
The upper and downstream wall portions, which are formed to have a width larger than the width of 4 and which connect the inner wall 2d of the flow path with the inner portion 14, are inclined upward and downstream, respectively. That is, the groove portion 13 includes a deep portion 14 and inclined portions 15 and 16 formed in a tapered shape so as to connect the deep portion 14 and the upper and downstream flow path inner walls 2d. Further, the tip portions 6c of the plurality of blades 6b that protrude radially from the hub 6a of the impeller 6 are fitted into the groove 13.

Note that a gap 17 is provided between the tip 6c of the impeller 6 and the inner part 14 of the groove 13 in consideration of the processing accuracy of the shaft 7, the dimensional accuracy of the downstream cone member 4, the looseness of the bearings 8 and 9, etc. It is provided. Further, the inclined portion 15 is located upstream of the impeller 6, and the inclined portion 16 is provided downstream of the impeller 6.

Here, when fluid is supplied from the downstream side, the fluid flows into the main body 2 along the annular channel 2e formed between the upstream cone member 3 and the channel inner wall 2d. Furthermore, the fluid passes through the blades 6b of the impeller 6 from the flow path 2e, flows into the flow path 2f between the downstream cone member 4 and the flow path inner wall 2d, and flows out into the flow path 2c. In addition, a part of the fluid flowing near the inner wall 2d of the channel 2e flows into the groove 13 along the inner wall 2d of the channel and the inclined part 15, and flows between the tip 6c of the impeller 6 and the inner part 14 of the groove 13. The water passes through the gap 17 formed between the two and flows to the downstream inclined portion 16. In this way, the impeller 6 rotates according to the flow rate flowing from the flow path 2e to the flow path 2f. The rotational speed of the impeller 6 is counted, converted into a flow rate, and displayed.

FIG. 3 shows the velocity distribution of the fluid in the flow path 2e and the groove portion 13. In FIG. 3, the velocity distribution A of the fluid in the channel 2e has a high velocity at the center of the channel, and a small velocity near the upstream cone member 3 and the inner wall 2d of the channel, forming a parabolic shape. However, groove 1
Velocity distribution B of the fluid when passing through a flow path having 3
is the central part of the flow path and the cone member 3 on the upstream side of the flow path.
On the side, the velocity distribution is almost the same as A, but the groove part 13
Since the flow path area in the vicinity is larger than the flow path area of the flow path 2e, the velocity of the fluid near the inner part 14 of the groove portion 13 is small.

Therefore, the tip 6c of the impeller 6 and the groove 13
The flow rate of the fluid passing through the gap 17 between the impeller and the inner wall 14 of the flow path is smaller than that of the conventional system (in which the impeller is spaced apart from the inner wall 2d of the flow path). For this reason, the impeller 6
Since the blades 6b rotate under the influence of most of the fluid force of the fluid passing through the flow path 2e, the loss can be reduced and the flow rate can be measured with high accuracy.

Further, the inclined portion 15 becomes a dead area, and dust in the fluid tends to adhere to the inclined portion 15. Therefore, dust in the fluid is less likely to adhere to the inner part 14 of the groove part 13 and the downstream slope part 16. Since dust is difficult to accumulate in the inner part 14, the rotation of the impeller 6 is not hindered by dust. In addition, the inclined portion 15
Since it is spaced apart from the impeller 6, even if dust adheres to the inclined portion 15, it will not close the gap 17.
That is, there is no problem that the flow path area of the gap 17 becomes narrow due to the adhesion of dust, the leakage amount of the fluid passing through the gap 17 decreases, and the instrumental error fluctuates due to changes over time.

Furthermore, even when flow rate measurement is performed over a long period of time, a decrease in instrumental error due to dust accumulating on the inclined portion 15 is prevented, allowing accurate flow rate measurement for a long period of time, and improving durability. .

FIG. 4 shows a comparison between the instrumental error (indicated by a broken line) of the flowmeter described in the conventional example and the instrumental error (indicated by a solid line) of the flowmeter according to the embodiment of the present invention. In Fig. 4, the instrumental error in the case of the flowmeter described as the former conventional example is as shown by the broken line C, when measuring low flow rates, it largely protrudes to the + side, and when measuring medium flow rates, it curves to one side, and when measuring high When measuring the flow rate, it can be seen that the flow rate has increased to the + side again. On the other hand, as in this embodiment, the flow path inner wall 2
In the case of a flowmeter in which a groove 13 into which the tip 6c of the impeller 6 fits is provided at d, and sloped portions 15 and 16 are provided on the downstream side, the instrumental error varies from low flow to high flow as shown by solid line D. It can be seen that the flow rate changes linearly near 0 over the flow rate. Therefore, the flowmeter of the present invention has improved instrumental error compared to conventional flowmeters, and can accurately measure flow rates over the range from low flow rates to high flow rates.

Effects of the Invention As described above, according to the turbine flowmeter of the present invention, the velocity distribution of the fluid passing through the flow path having grooves is different from that in the central portion of the flow path and on the upstream side of the flow path. The velocity distribution is the same as the velocity distribution when passing through a channel that is not tilted, but since the channel area is large at the slope near the groove, the velocity of the fluid passing through the gap between the tip of the blade and the deep part of the groove is It becomes small,
Loss when rotating the impeller can be reduced. Furthermore, the slope becomes a dead zone, making it easier for dust in the fluid to adhere to the slope, reducing dust adhesion to the deep part of the groove, and reducing instrumental error as dust accumulates over time. It has the advantages of being able to suppress this, to be able to accurately measure the flow rate over a long period of time, to prevent shortening of life due to dust adhesion, and to improve reliability.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view for explaining one embodiment of the turbine flowmeter according to the present invention, FIG. 2 is a cross-sectional view for explaining the shape of the groove on the inner wall of the flow path, and FIG. FIG. 4 is a diagram for explaining the velocity distribution of the fluid flowing in the flow path shown in the figure, and FIG. 4 is a diagram for explaining the instrumental difference between the present embodiment and the conventional example based on changes in flow rate. 1...Turbine type flow meter, 2...Main body, 2d...
... Channel inner wall, 2e, 2f... Channel, 3... Upstream cone member, 4... Downstream cone member, 6... Impeller, 6c... Tip, 13... Groove, 14...
Deep part, 15, 16...slanted part, 17... gap.

Claims (1)

[Claim for Utility Model Registration] An annular groove recessed in the radial direction of the flow path is provided on the inner wall of the flow path on a circular pipe, and an impeller with a plurality of blades on the circumferential surface is provided in the first half of the flow path. The tip of the blade is rotatably provided coaxially with the flow path so as to protrude into the groove, and the flow rate of the fluid to be measured is determined based on the rotation of the impeller, which rotates in accordance with the flow rate of the fluid to be measured. In the turbine flowmeter for measurement, the groove is formed such that the width of the opening in the flow direction is larger than the width of the inner part thereof, and the upper and downstream sides connecting the inner part and the inner wall of the flow path. A turbine-type flowmeter characterized by having walls that are sloped upward and downward, respectively.