JPS58221116A - Detector for flow rate - Google Patents

Abstract

PURPOSE:To enable the measurement of the flow rate of each flow passage with good accuracy, by determining the differential pressure between the pressure of the orifices disposed in the longitudinal direction of the flow passages with their axial center intersecting orthogonally with flow and the pressure on the upstream side of said orifices. CONSTITUTION:Orifices 10 are inserted in flow passages 7 with the axes thereof directed in the longitudinal sectional direction of said flow passages, and pressure detecting holes 11 open in the direction at right angles to the flow direction. Pressure conduit pipes 12 are connected respectively to the holes 11. The 2nd pressure conduit pipe 13 is provided on the upstream side of the orifices 10 of a duct 1, that is, in a placed where flow passages are not segmented by partition walls 6. The pipes 12 and the 2nd pipe 13 are conducted respectively to a differential pressure gage. Therefore, if the relations between the differential pressure and flow rate intrinsic to the orifices 10 are beforehand calibrated, the flow rates in the passages 7 are determined. The flow rates in the respective flow passages are thus measured with good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the flow rate of a fluid flowing in a fluid.

As a device for measuring the flow rate of fluid flowing inside a rectangular duct, the device shown in FIG. 1 has been proposed and put into practical use.

In Fig. 1, l is a rectangular duct, 2 is a pair of rectangular plates protruding from the side wall of the duct toward the downstream side;
The pressure pipes 3a and 3b are installed to take out the wall pressure on the upstream and downstream sides of the pipe.

Therefore, from the pressure value obtained from impulse pipes 3 and 3b,
However, it is possible to determine the flow rate of the fluid flowing inside the rectangular duct l-1 with extremely high accuracy.

There are cases where it is difficult to apply such a device.

For example, as shown in FIG. 2, there is a case where the amount of air sent to a plurality of wind boxes 5 attached to a combustion furnace 4 of a boiler is measured.

Normal air is. It is sent through a single rectangular duct 1 and separated by a bulkhead 6 just before the wind box 5.
In order to improve the performance of the burner, it is necessary to correctly control the amount of air sent to each wind box 5. Therefore. When trying to measure the flow rate in a channel 7 with a rectangular cross section divided by a partition wall 6 using the device shown in Fig. 1, two plates (reference numeral 2 in Fig. 1)
I have to weld it.

Due to the narrow location of the site, welding distortion may result in poor accuracy and the mounting angle cannot be set accurately.

It also resulted in a lack of accuracy.

The flow rate detection device of the present invention is a device for detecting the flow rate of a fluid flowing in a flow furnace having a rectangular cross section.

an orifice having a cylindrical shape and disposed in the longitudinal direction of the flow path with its axis perpendicular to the flow; a first pressure detection means for detecting pressure acting on the surface of the orifice; and an orifice in the flow path. Since it consists of a second ligature pressure detection means that detects the pressure on the upstream side, it is not only possible to detect the flow rate in a normal flow channel with a rectangular cross section, but also in a very narrow and parallel flow channel as shown in Figure 2. The flow rate of each flow path can be measured with high accuracy when there are many flow paths.

The present invention will now be described with reference to an embodiment of the apparatus shown in FIGS. 3 and 4.

Reference numeral 10 denotes a cylindrical orifice, on the surface of which a plurality of pressure detection holes 11 are opened in a row in the axial direction.

The pressure detection hole 11 communicates with the inside of the OriSwiss 1o, and a pressure guiding pipe 12 is connected to each of the openings 1-9 on the end surface 10a.

Similar to FIG. 2, FIG. 4 shows a part of the duct 1 that sends air to the combustion furnace wind box of the boiler.

The flow path is divided by partition walls 6.

The orifice 1o described above is inserted with its axis facing the longitudinal direction of the cross section of the flow path 7, and the pressure detection hole 11 is opened in a direction perpendicular to the flow direction. Reference numeral 13 denotes a second pressure impulse pipe attached to the upstream side of the orifice 1o of the duct 1, that is, at a location where the flow path is not divided by the partition wall 6.

Incidentally, the pressure impulse pipe 12° attached to the orifice 10 and the second pressure impulse pipe 13 attached to the duct 1 are each grooved by a differential pressure gauge (not shown).

Therefore, the flow rate in each flow path 7 can be determined by calibrating the relationship between the differential pressure unique to the cylindrical orifice 1G and the flow rate (flow velocity) in advance.

5 and 6 show the relationship between the orientation of the pressure detection hole 11 with respect to the flow direction and the resulting differential pressure. As shown in Fig. 5, the inclination of the pressure detection hole 11 with respect to the flow direction is 61.
If the static pressure acting on is P, the pressure at a location sufficiently far from the orifice 10 is Pa, and the velocity of the fluid is, then the differential pressure P - P
.

Then, the ratio of the dynamic pressure pv2/2g changes greatly as shown in FIG.

Therefore, as in the embodiment shown in FIG. 4, when θ=90 degrees, the differential pressure can be extracted with good sensitivity.

Thus, according to an apparatus according to an embodiment of the present invention.

An orifice lO is installed in the flow path 7 of the duct 1 partitioned by the partition wall 6.
The installation work is easy because all that is required is to insert and fix an orifice 10 as shown in FIG. 3 through an opening made in the wall of the duct 1.

However, when there are a large number of flow paths 7 as in this embodiment, it is sufficient to measure the static pressure at only one point on the upstream side of the orifice 10 and find the differential pressure at each point, so the number of pressure guiding pipes can be reduced.

Furthermore, when using a plate orifice as in the past, there was an inconvenience that the pressure pipe had to pass through another flow path, but in this embodiment, the pressure is passed through the inside of the orifice 10. to be transmitted and connected to the impulse line 12 outside the duct 1.

There is no extra material in the flow path, which improves measurement accuracy.

In addition, as described above, the pressure detection hole 11 in the flow direction
The sensitivity of the obtained differential pressure changes depending on the direction O, so
If the obtained differential pressure is too large, the relationship between the differential pressure and the flow rate may be determined by changing 19, thereby expanding the measurable range.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a conventional device, Fig. 2 is a diagram showing an embodiment of a flow path, Fig. 3 is a perspective view of an orifice used in the present invention, and Fig. 4 is a diagram showing an embodiment of the device of the present invention. , FIG. 5 is a diagram showing the relationship between the flow direction and the pressure detection hole, and FIG. 6 is a graph showing the relationship between the angle g and the differential pressure. 1: Talito, 6: Partition, 7: Channel, 10 Niorifice,
11: Pressure detection hole, 12: Impulse tube. 13: Second impulse pipe. Manbun version 2/

Claims (1)

[Claims] This device detects the flow rate of fluid flowing in a flow channel with a rectangular cross section, and includes a cylindrical orifice whose axis is perpendicular to the flow and is arranged in the longitudinal direction of the flow channel, and an orifice on the surface of the orifice. A flow rate detection device comprising a first pressure detection means for detecting the applied pressure and a second pressure detection means for detecting the pressure upstream of the orifice in the flow path.