JPS5819451Y2 - Permanent bolus flume flow meter - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of a permanent bowlus flume flow meter that measures the flow rate in an underdrain with a circular cross section. Regarding the structure of a flowmeter.

FIG. 1a is a perspective view of a conventional example of a permanent bowlus flume flowmeter, and the figure is a longitudinal sectional view thereof.

Arrow A indicates the flow direction of the fluid to be measured, and Z is a throat formed in the tube body to narrow the flow path.

The throat 2 consists of a flat bottom plate 2a along the bottom of the tubular body 1, and a pair of opposing side plates 2b that intersect with the bottom plate 2a in the axial direction of the tubular body 1 and are spaced apart from each other toward the top of the bone. Slanted plates 2c and 2c' that gradually reach the tube body 1 are formed on the upstream and downstream sides of the bottom plate 2a in order to reduce friction loss of the fluid to be measured, and similarly, inclined plates 2c and 2c' are formed on the upstream and downstream sides of the side plate 2b. A pair of inclined plates 2d and 2d' are formed respectively.

Here, the upstream inclined plate is at an angle α with respect to the pipe body, inclined plate 2
C/ is arranged at an angle β with respect to the tube body 1, and in general α and β are not equal.

Further, a branch pipe 3 communicating with the pipe body 1 is formed at the upper part of the upstream pipe body of the throw) 2, that is, above the inclined plate 2d, and a level meter such as an ultrasonic level meter is attached to this branch pipe 3. There is.

With the above configuration, when the fluid to be measured flows into the pipe body 1 in the direction of the arrow A, the flow path is constricted at the throat part 2 to create a critical flow, and by measuring the water depth Ha on the upstream side of the throat part 2, the pipe body 1 can be calculated.

However, this method of calculating flow rate by simply measuring the water depth at a single point upstream of the throat is applicable only when the flow at the throat is a free flow (that is, changes in water depth downstream of the throat are not transmitted to the upstream side). It was only when there was no flow.

Therefore, the water depth on the downstream side rises abnormally for some reason,
In a situation where there is almost no difference in the water depth before and after the throat 2, so-called slip-flow conditions, the flow velocity of the fluid flowing through the throat 2 is slower than the wave propagation speed, so it is difficult to simply measure the water depth at a single point on the upstream side. , accurate flow measurement was not possible.

FIG. 2 is a longitudinal cross-sectional view of a partial flume flowmeter that measures the flow rate of a channel having a rectangular cross section.

Traditionally, partial flume flowmeters have been used to measure flow rates in open channels with square cross-sections, and flow rate measurements under underflow conditions have been performed as follows.

That is, the flow rate f (Ha') under free stream conditions, which is calculated from the upstream water depth Ha' by measuring the water depths Ha' and Hb' before and after the throat 2', is a function of the submergence degree Hb'/Ha'. By multiplying by a certain correction coefficient g (Hb7Ha'), the flow rate Q = f (Ha') - g (Hb7
Ha') is calculated.

Figure 3 shows the slippage degree Hb7Ha' and the correction coefficient g (Hb7H
a'), and this correction coefficient g
(Hb'/Ha') is uniquely determined by the size and degree of submergence of the partial flume flowmeter.

However, in the permanent bowlus flume flowmeter, as shown in FIG. It was possible to measure the water depth on the upstream side, but not on the downstream side.

The purpose of this invention is to realize a permanent bowlus flume flowmeter that can measure the flow rate under dipping conditions and when the fluid to be measured flows backward. It has a shape that is symmetrical with respect to a certain plane, and the water depth can be measured at two positions, one on the upstream side of the throat and the other on the downstream side, which are symmetrical with respect to the one plane.

Fig. 4 shows an embodiment of the present invention, and Fig. a is a perspective view thereof, and Fig. 4 is a longitudinal sectional view thereof.

Arrow A indicates the direction in which the fluid to be measured flows.

The throat 21 is a flat bottom plate 21a along the bottom of the tube body 1.
The bottom plate 21a and a pair of opposing side plates 21b intersect in the axial direction of the tube body 1 and are spaced apart from each other toward the top of the bone. In order to reduce the friction loss of the fluid, inclined plates 21C and 21C' that gradually reach the pipe body 1 are formed,
Similarly, a pair of inclined plates 21 d and 21 d' are formed on the upstream and downstream sides of the side plate 21 b, respectively.

In addition, these inclined plates 21C, 21C' and the side plate 21d,
21d' is one plane B- perpendicular to the axial direction of the tube body 1.
The shape of the throat 21 is symmetrical with respect to the plane B--B.

In addition, a pair of branch pipes 3 and 3' communicating with the inside of the pipe body are provided at the upper part of the pipe body on the upstream and downstream sides of the throat 21 on the plane B-B.
It is formed in a symmetrical position with respect to.

In this way, the present invention has two branch pipes 3, 3' on the upstream and downstream sides of the throat 21, and the water depth is measured at two points, making it possible to measure the flow rate under submerged conditions. became.

That is, if the flow rate under free-flow conditions is f (Ha) when the water depth measured by the level meter placed on the upstream side of the throat 21, that is, the branch pipe 3, is Ha, then the flow rate Q under submerged conditions is:
Measure the water depth on the downstream side, that is, the water depth Hb when measured at the 3' part of the branch pipe, multiply f (Ha) by the correction coefficient g (Hb/Ha) based on the degree of sinkage Hb/Ha, and calculate Q = f (Ha). −
It can be calculated as g(Hb/Ha).

In addition, since the shape of the throat 21 is perpendicular to the pipe axis and symmetrical with respect to the -B plane, if the fluid to be measured flows backwards in the direction opposite to arrow A, the water depth Hb measured at the branch pipe 3' The flow rate can be calculated using as the upstream water depth.

As described above, the permanent bowlus flume flowmeter according to the present invention can measure the flow rate not only under underflow conditions but also when the fluid to be measured flows backward.

[Brief explanation of the drawing]

Figure 1 shows a conventional example of a permanent bowlus flume flowmeter, Figure a is its perspective view, figure 2 is its longitudinal cross-sectional view, and Figure 2 is a partial flume flowmeter showing measurement under underflow conditions. FIG. 3 is a graph showing the relationship between the degree of slippage and the correction coefficient, FIG. . 1: Pipe body, 3.3': Branch pipe, 21 Nisthroat.

Claims (1)

[Scope of utility model registration request] In a permanent bowlus flume flowmeter, a throat (throttled portion) is formed in a tube with a circular cross section through which a fluid to be measured flows, and a level meter for measuring the fluid water depth at the throat is attached to the tube. is symmetrical with respect to a plane perpendicular to the pipe axis of the pipe body, and a pair of branch pipes are provided on the pipe body above the throat on the upstream and downstream sides of the throat and communicating with the inside of the pipe body. A permanent bowlus flume flowmeter, characterized in that the flowmeter is formed at symmetrical positions with respect to a plane perpendicular to the pipe axis, and level gauges can be placed in each of these branch pipes.