JP3322550B2 - Flow measurement device using duct reinforcement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring apparatus utilizing duct reinforcement for measuring a flow rate of a smoke exhaust duct or the like of a boiler for power generation.

[0002]

2. Description of the Related Art As a means for measuring a gas flow rate in a straight pipe portion such as a smoke exhaust duct of a power generation boiler, a flow meter such as a reverse type pitot tube is inserted into the smoke exhaust duct from the outside, and the flow rate is measured while traversing. There is a way to do it. FIG. 7 as an example
8 shows a schematic view of a smoke exhaust duct of the power generation boiler, and FIG. 8 shows a cross-sectional view of the smoke exhaust duct of the power generation boiler, which is a DD section in FIG.

In FIGS. 7 and 8, a plurality of support pipes 02 for reinforcing a duct are arranged in a straight line in a flue gas exhaust duct 01 of a boiler for power generation in a gas flow direction 03. In the figure, reference numeral 04 denotes a flow velocity measurement hole, and the reverse type pitot tube 06 of FIG. 9 is inserted from the flow velocity measurement hole 04 to perform measurement while traversing an arbitrary measurement point 05 as shown in FIG. , And determine the flow rate.

FIG. 9 shows the reverse type pitot tube 0 described above.
6 (a) is a side view, and FIG. 6 (b) is an EE cross-sectional view thereof. In this figure, the reverse-type pitot tube 06 has a pressure bore 07 which directly facing the flow 03 has a pipe for taking out the pressure P _T, the pressure hole 08 of the 180 ° opposite direction, taking the pressure P _S tube And the pressure P
Take out the _T and P _S.

[0005] Pressure P_TAnd pressure P_SIs about 2 of the true dynamic pressure
Pressure P_TAnd pressure P _SMeasuring the difference between
Thus, the true dynamic pressure is known, and the flow velocity is obtained. The pressure
Force P _TAnd pressure P_SThe difference is the apparent dynamic pressure,
Compare with standard Pitot tube (Prandtl type) in
You.

[0006]

The conventional flow rate measurement of a smoke exhaust duct or the like of a boiler for power generation as shown in FIG. 7 is performed at a position where flow is not sufficiently rectified due to disturbance caused by the support pipe 02. , Causing measurement errors.

[0007] As shown in FIG.
There are several places (three places in FIG. 8) per cross section, and it takes a very long time to measure the flow velocity while traversing an arbitrary measurement point 05 (9 points in FIG. 8) from each flow velocity measurement hole 04.

[0008]

The present invention provides the following means (1) and (2) in order to solve such problems.

(1) A flow rate measuring device for measuring a pressure in a smoke exhaust duct of a power generation boiler using a reverse type pitot tube in the smoke exhaust duct and obtaining a flow rate from the pressure.
The reverse-type pitot tube is provided with a front-side pressure hole facing the gas flow and a downstream-side pressure hole facing the gas flow hole at a predetermined position of the reinforcing support pipe in the smoke exhaust duct. A flow measurement device using duct reinforcement, wherein a pre-stream pressure outlet pipe and a wake side pressure outlet pipe connected to the two pressure holes are provided in a pipe and used together with the supporting pipe.

(2) In the above (1), each of the upstream pressure holes and the downstream pressure holes includes a plurality of pressure holes, and the pressure holes are equally divided at a predetermined angle toward the center of the support pipe. A flow rate measuring device utilizing duct reinforcement characterized by being arranged and drilled and connected to the same number of upstream and downstream pressure discharge pipes.

According to the present invention, in the means (1), a support pipe for reinforcing a smoke exhaust duct or the like of a power generation boiler is used in combination with a reverse type pitot tube. The effect of the supporting pipe is reduced. That is, in the conventional measurement, the reverse type pitot tube was inserted into the smoke exhaust duct, and the measurement was performed by traversing the middle of the front and rear support pipes. The effect of the pipe upstream of the measurement point is reduced. Therefore, a sufficiently rectified flow is measured, a measurement error is eliminated, and an accurate flow rate can be measured. In addition, pressure holes can be provided at any positions of the support pipe, and by averaging those pressures, one section can be measured at a time, thereby reducing measurement time and improving accuracy.

In the means (2), since a plurality of pressure holes arranged at a fixed angle at one measurement position are provided, at the beginning of the installation, the upstream and downstream sides at each angular position are provided. Since pressure measurement is performed and the pressure hole showing the maximum value among the measured values can be used for measuring the flow rate at that position, more accurate flow rate measurement is possible.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a smoke exhaust duct of a boiler for power generation to which a flow rate measuring device using duct reinforcement according to an embodiment of the present invention is applied,
FIG. 2 is a view taken in the direction of arrows AA, and schematically shows the support pipe 2 in the smoke exhaust duct viewed from the flow direction 3, and FIG.
FIG. 4 is a schematic view of the support pipe 2 in the smoke exhaust duct as viewed from the downstream side in the arrow view. FIG. 4 shows the details of the support pipe 2,
(A) is a side view, (b) is the CC sectional view.

In FIG. 1, reference numeral 1 denotes a smoke exhaust duct straight pipe portion;
Is a support pipe for reinforcement, and 3 is a flow direction. 14
Is a digital manometer that inputs a measured value of pressure and detects a differential pressure, 15 is an A / D converter, 16 is an arithmetic processor, 17
Is an indicator.

As shown in FIGS. 2 and 3, the support pipes 2 are provided at the four corners and at the center and at the center of the smoke exhaust duct straight pipe section 1 to reinforce the duct, as shown in FIG. 2, the support pipe 2 has 12 measurement positions in the flow direction of 4A to 12A as shown in FIG. 2, and as shown in FIG. Also, the measurement positions on the side facing the 12 flows of 4B to 12B are provided.

In FIG. 4, the support pipe 2 used as a reinforcing material in the straight pipe portion 1 of the smoke exhaust duct has several pressure extraction pipes 13 built therein. The distal end of each pressure extraction pipe 13 has a pressure hole 4A1, 4A2, 4A3 formed on the A side on the upstream side and the B side on the downstream side with respect to the flow direction 3.
4A4, 4A5 and 4B1, 4B2, 4B3, 4B
4, 4B5.

The pressure holes on the A side and the B side respectively extend 10 ° on the circumference toward the center of the support pipe 2 as shown in FIG.
At intervals, + 10 °, + 20 °, -10 °, 0 °
A total of 5 holes are drilled at -20 °. The pressure measurement position within the cross section of the duct is as follows.
At two measurement points on the B side and 12 measurement points from 4B to 12B shown in FIG. 3, five pressure holes are formed in the duct every 10 ° from -20 ° to + 20 ° with reference to 0 °. , Are connected to a pressure extraction pipe 13.

As described above, the pressure difference between the A side and the B side corresponding to each angle is measured as apparent dynamic pressure by the pressure extraction pipes 13 provided at the respective measurement positions, and the pressure difference is initially measured in five directions at different angles. Among the pressure differences measured, the measurement hole showing the maximum is used for flow rate measurement.

FIGS. 5 and 6 show examples of the measured values, and the horizontal axis (θde
g) is the angle (or yaw) around the circumference of the reverse pitot tube.
In this figure, the range is up to ± 20 °, and the vertical axis (pd '
/ pd) indicates the dynamic pressure ratio (or Pitot tube coefficient) between the standard pitot tube and the reverse type.

Maximum point in FIG. 5 (+ 10 ° in this figure)
Will be used as a flow rate measurement hole in the future,
Further, as shown in FIG. 6, even at a position ± 5 ° from the maximum point, a difference in the dynamic pressure ratio is hardly recognized, and it can be seen that the difference can be ignored as an error.

As described above, the flow rate measurement holes are determined at the respective measurement positions, and the pressures on the A side (the upstream side) and the B side (the downstream side) are measured at the positions. Pressure P _T
Taken out an average pressure of 12 points up measurement position 4A~12A for similarly for even pressure P _S of the B side is taken out as each of the average pressure of 12 points up measurement position 4B～12B,
Digital manometer 14 of arithmetic system 20 shown in FIG.
To detect the pressure difference, calculate the flow rate by the arithmetic processing unit 16 via the A / D converter 15, and display it as the flow rate on the indicator 17.

According to the embodiment described above, the supporting pipe 2 for reinforcing the straight pipe portion 1 of the smoke exhaust duct of the boiler for power generation is described.
Drill the pressure holes 4A1 to 4A5 and 4B1 to 4B5
By providing the pressure extraction pipe 13 and using the support pipe 2 and the reverse type pitot pipe together, the measurement point is located rearward as compared with the conventional method of traversing the middle between the front and rear support pipes. The effect of the downstream pipe is reduced.

Further, by providing pressure holes at arbitrary positions of the support pipe 2 and averaging the pressures, it is possible to measure one section at a time, thereby reducing measurement time and improving accuracy.

[0024]

As described above, according to the present invention, a reverse type pitot tube is used in combination with a support pipe for a smoke exhaust duct of a power generation boiler, and a plurality of pressure holes are provided in the support pipe. Are equally arranged at a predetermined angle and connected to a plurality of pressure extraction pipes, respectively, so that the following effects can be obtained.

(1) By using the supporting pipe as a reverse type pitot tube, the measuring point is located behind the conventional type, and the effect of the pipe on the upstream side is reduced, and a sufficiently rectified flow is measured. Measurement error can be eliminated.

(2) In addition, since a pressure hole can be provided at an arbitrary position of the support pipe, the flow velocity can be measured over the entire cross section at a time, and a large time error can be obtained.

(3) The support pipe is provided with a plurality of pressure holes and a pressure extraction pipe, and the pressure hole having the maximum measured value can be used for measurement. However, accurate measurements can be made.

(4) Further, the flow rate can be checked at all times, and the flow rate can be checked at all times, and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram to which a flow rate measuring device utilizing duct reinforcement according to an embodiment of the present invention is applied, showing a smoke exhaust duct of a boiler for power generation and a measuring system.

FIG. 2 is a view taken in the direction of arrows AA in FIG.

FIG. 3 is a view taken in the direction of arrows BB in FIG. 1;

FIG. 4 is a view showing a support pipe, a pressure extraction pipe, and a pressure hole in the flow rate measurement device according to the embodiment of the present invention;
(A) is a side view of a support pipe, (b) is CC sectional drawing.

FIG. 5 is a diagram showing a relationship between a pitot tube coefficient and a yaw angle of a reverse type pitot tube, showing a case where a maximum point is 10 °.

FIG. 6 is a diagram showing a relationship between a pitot tube coefficient and a yaw angle of a reverse type pitot tube, showing a maximum point and an error range.

FIG. 7 is a schematic layout diagram showing a smoke exhaust duct and a measurement hole of a conventional power generation boiler.

8 is a sectional view taken along the line DD in FIG. 7;

9A and 9B show a conventional reverse-type pitot tube, FIG. 9A is a side view, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Smoke exhaust duct straight pipe part 2 Support pipe 3 Flow direction 4A1-4A5 Pressure hole 4B1-4B5 Pressure hole 4A-12A A side (front side) measurement position 4B-12B B side (back side) measurement position 13 Pressure extraction Tube 14 Digital manometer 15 A / D converter 16 Arithmetic processor 17 Indicator 20 Arithmetic system

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-147026 (JP, A) JP-A-50-144466 (JP, A) JP-A-63-246618 (JP, A) 155372 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 1/00-9/02 G01P 5/16-5/165

Claims (2)

(57) [Claims] 1. A flow measuring device for measuring a pressure in a smoke exhaust duct of a power generation boiler using a reverse type pitot tube in the smoke exhaust duct and obtaining a flow rate from the pressure, wherein the reverse type pitot is provided. The pipe is provided with a upstream pressure hole facing the gas flow and a downstream pressure hole facing the gas flow hole at a predetermined position of the reinforcing support pipe in the smoke exhaust duct,
A flow measurement device using duct reinforcement, wherein a pre-stream pressure outlet pipe and a downstream pressure outlet pipe connected to the pressure holes are provided in the support pipe and used together with the support pipe. 2. The upstream pressure hole and the downstream pressure hole,
It is composed of a plurality of pipes, each of which is disposed so as to be equally divided at a predetermined angle toward the center of the support pipe, and is connected to the same number of upstream and downstream pressure discharge pipes. The flow rate measuring device utilizing duct reinforcement according to claim 1, wherein the flow rate measuring device is used.