JPH0429017A - Method and instrument for measuring flow velocity and flow direction of fluid - Google Patents

Abstract

PURPOSE:To measure the velocity and direction of a flow in a live tube by providing a couple of heating element for detection across a shield member in the axial direction of a fluid supply tube and measuring them with signals from heat-ray type flow velocity sensors corresponding to the heating element for detection. CONSTITUTION:The couple of heating elements 2a and 2b for detection and the shield member 3 are provided in the fluid supply tube 12. The heat of the heating elements 2a and 2b is absorbed by the fluid according to the flow velocity and the elements are cooled, so sensor driving circuits 6a and 6b corresponding to the heating elements 2a and 2b output signals corresponding to the flow velocity of the fluid. The output voltages of the circuits 6a and 6b are compared by a comparator 8; when the fluid flows as shown by an arrow, the output voltage of the circuit 6b becomes higher, the comparator 8 outputs a signal indicating the heating element 2b is on an upstream side, and a changeover switch 9 selects the side of the circuit 6b. Then its output voltage is supplied to a processor 11 through a squaring device 10 to measure the means flow velocity at specific intervals of time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for measuring the flow velocity and flow direction of fluids such as gases and liquids.

(Prior art) For example, as conventional flowmeters used to measure the amount of gas supplied in city gas supply systems, there are various flowmeters such as impeller type, pitot tube type, differential pressure type, and positive displacement type. Each has its own advantages in measurable flow velocity range, measurement accuracy, responsiveness, etc.
It has disadvantages.

(Problems to be Solved by the Invention) The above-mentioned conventional flowmeter must be installed in advance on the fluid supply pipe to be measured, and the flow rate or flow velocity of the fluid flowing into the fluid supply pipe can be controlled at an appropriate location as necessary. However, there is a problem in that it is not possible to measure with live tubes. In addition, for example, in a city gas supply system, there are cases where it is necessary to measure the flow direction of gas, such as when estimating the location of water difference by investigating the distribution of water content in the supply pipe. What is desired is a measuring device that can measure flow direction as well as flow velocity.

The present invention has been made in view of the above points, namely:
It is an object of the present invention to provide a measuring method and a measuring device that can solve the above-mentioned conventional problems and simultaneously measure the flow velocity and flow direction of a fluid using a live tube.

(Means for Solving the Problems) Means for solving the above-mentioned problems will be explained with reference to drawings corresponding to examples. A pair of detection heating elements 2a and 2b, which constitute the components of the sensor, are installed at a predetermined distance apart in the axial direction of the fluid supply pipe 12 to be measured, and a shielding member 3 is installed between them. Detection heating element 2a.

The flow direction of the fluid is detected by comparing the output signals of the hot wire flow velocity sensors corresponding to the hot wire flow velocity sensors 2b, and the flow velocity of the fluid is measured by the output signals of the hot wire flow velocity sensors corresponding to the upstream detection heating elements 2a and 2b. It is something to do.

In the above configuration, the hot wire type flow velocity sensor has a pair of detection heating elements 2a and 2b installed at a predetermined distance apart from one end of the sensor body l, and a shielding member 3 between them. and the detection heating elements 2a, 2
Temperature compensation resistors 4a, 4b are installed closer to one end of the sensor body 1 than b, and the respective detection heating elements 2a,
2b and temperature compensation resistors 4a and 4b into a bridge, and a pair of sensor drive circuits 6a that adjust the bridge voltage so as to make the unbalance of each bridge circuit zero,
6b, the bridge voltage is adjusted by the sensor drive circuits 6a and 6b, and the detection heating element 2a,
2b may be held constant, and the flow velocity of the fluid may be derived from the output signals of the sensor drive circuits 6a, 6b corresponding to the current flowing through the bridge circuit at this time.

Further, the fluid flow velocity and flow direction measuring device of the present invention includes a pair of detection heating elements 2a and 2b installed at a predetermined distance from one end of the sensor body l, and a shielding member disposed between them. 3, and the detection heating element 2a
, temperature compensation resistors 4a and 4b are installed closer to one end of the sensor body 1 than 2b, and the respective detection heating elements 2
a, 2b and a temperature compensation resistor 4a.

4b as a bridge, and a pair of sensor drive circuits 6a and 6b that adjust the bridge voltage so as to make the unbalance of each bridge zero. , 6b, and the sensor drive circuit 6 to be switched and output according to the output signal of the comparator 8.
A detection circuit B consisting of a changeover switch 9 for selecting between a and 6b is provided, and the comparator 8 outputs a signal corresponding to the flow direction, and the changeover switch 9 outputs a signal corresponding to the flow velocity. This is what I did.

In the above method or apparatus, the detection heating element 2a,
2b can be composed of a self-heating semiconductor thermistor. Further, the shielding member may be formed into a plate shape or a rod shape as appropriate.

(Function) In the above configuration, the pair of detection heating elements 2a and 2b installed in the fluid supply pipe 12 to be measured and placed in the flow of fluid are heated by the fluid according to the flow velocity. Therefore, each hot wire flow velocity sensor generates a signal corresponding to the fluid flow velocity with respect to each detection heating element 2a, 2b.

In this case, the detection heating element 2a located on the downstream side of the flow,
Due to the effect of the shielding member 3, the flow velocity of the fluid to the hot wire flow velocity sensor 2b is slower than the flow velocity to the upstream detection heating elements 2a and 2b. By comparing the detection heating element 2a, which corresponds to which hot wire flow velocity sensor,
2b is upstream and thereby the direction of fluid flow can be detected.

On the other hand, the flow velocity of the fluid to each detection heating element 2a, 2b is influenced by the shielding member 3 and becomes slower than the actual value, and therefore the output signal of each hot wire flow velocity sensor also decreases. Regarding the hot wire type flow velocity sensor, although the signal output decreases in this way, the functional system of the correspondence between flow velocity and output does not change, so the fluid flow velocity can be accurately derived from that correspondence. In addition to detecting the upstream side as described above, the flow rate of the fluid can be accurately derived from the output signal of the hot wire type flow rate sensor on the upstream side. The flow rate can be detected from this flow rate and the diameter of the fluid supply pipe 2.

A detection heating element 2a constituting the above hot wire flow rate sensor,
By configuring 2b with a self-heating semiconductor thermistor, the configuration of the hot wire flow rate sensor can be made smaller. That is, in the hot wire flow rate sensor using this self-heating semiconductor thermistor as the detection heating elements 2a, 2b, the detection heating elements 2a, 2b are installed at positions within the fluid supply pipe 12 that are not affected by the shielding member 3. The heating element 2a for detection is assembled into a bridge with the temperature compensation resistors 4a and 4b, and the bridge voltage is adjusted so as to make the unbalance of the bridge zero.

2b is held constant, and from a signal corresponding to the current flowing through the bridge circuit at this time, the detection heating element 2a
The amount of heat taken away from 2b can be detected, and the flow velocity of the fluid can be detected from a signal corresponding to this amount of heat taken away.

The flow direction and flow velocity described above are detected by a comparator 8 that compares the output signals of the sensor drive circuits 6a and 6b.
This can be carried out by a detection circuit B consisting of a changeover switch 9 which switches according to the output signal of the comparator 8 and selects the sensor drive circuit 6a, 6b to be output.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the external appearance of a part of the sensor main body A applied to the present invention, and FIG. 2 is a circuit diagram showing a hot wire flow rate sensor constituting the sensor main body A. In this figure, reference numeral l denotes a sensor body, and a pair of heating elements 2a for detection are located at a predetermined distance from one end of the sensor body l.
, 2b are installed at intervals, and a shielding member 3 is installed between them. These detection heating elements 2a, 2b
consists of a self-heating semiconductor thermistor. Also, code 4a.

4b is a temperature compensating resistor corresponding to each of the detecting heating elements 2a, 2b, and these temperature compensating resistors 4a, 4b are constituted by semiconductor thermistors. is also installed near one end of the sensor body 1 in a position that is not affected by the shielding member 3. The shielding member 3 is configured in a plate shape, and is attached to the side wall 15 of the protective cap 14, and when the protective cap 14 is attached to a predetermined position on the sensor base 1, the pair of heating element 2a for detection,
The configuration is such that it is installed between 2b. The protective cap 14 protects the sensor section by means of the side wall 15 and the top cover 16, and has a structure that does not interfere with the flow in the direction of the arrow indicated by the dotted chain line in the figure. Further, the temperature compensation resistor 4a
, 4b is the detection heating element 2a, which is the opposite of the above-mentioned configuration.

2b can be installed at a position farther from the sensor body 1, and the shielding member 3 is also not plate-shaped as described above.
In this case, the rod-shaped shielding member 3 can be protruded from the sensor body 1 and installed at a predetermined position.

As shown on one side in FIG. 2, each hot wire flow velocity sensor has a detection heating element 2a, 2b and a temperature compensation resistor 4a, 4b assembled into a bridge together with another resistor 5a, 5b. The bridge voltage is adjusted by the sensor drive circuits 6a and 6b so that the unbalance of the bridge becomes zero, and the temperature of the detection heating elements 2a and 2b is kept constant. It is configured to output a voltage corresponding to the flowing current, and the sensor drive circuits 6a and 6b are configured by differential amplifiers.

FIG. 3 shows a detection circuit B together with the sensor body A, and this detection circuit B connects the outputs of the sensor drive circuits 6a and 6b of the hot wire type flow velocity sensor to amplifiers 7a and 7, respectively.
b, and the outputs of these amplifiers 7a and 7b are input to a comparator 8 and a changeover switch 9. The changeover switch 9 performs a switching operation based on the comparison output of the comparator 8, and connects the sensor drive circuits 6a and 6b to output the output.
q) It is configured to make a selection. 6. The symbol IO is a squarer, and this squarer 10 is a function of the 1/4th power of the flow velocity, as will be described later. This is intended to linearize the output voltage of b. Reference numeral 11 is a processing device that performs predetermined processing on the output signals from the comparator 8 and the changeover switch 9 to obtain the flow velocity, flow rate, and flow direction, and this processing device 11 is a device to which a microcomputer is applied. be able to.

In the device of the present invention with the above configuration, for example, the perforation hole 13 is formed in the target fluid supply pipe 12, the sensor body 1 is inserted into the fluid supply pipe 12 from there, and the fluid is supplied by an appropriate method. The detection heating elements 2a, 2b and the shielding member 3 are arranged in the axial direction of the fluid supply pipe 12 so as not to leak from the fluid supply pipe 12, so that the following measurements can be carried out in the live pipe state. It can be performed.

Thus, the pair of detection heating elements 2a, 2 are installed in the fluid supply pipe 12 and placed in the fluid flow.
Since heat is removed by the fluid and cooled according to the flow velocity, the sensor drive circuits 6a, 6b corresponding to the respective detection heating elements 2a, 2b are connected to the respective detection heating elements 2a, 2b.
A signal corresponding to the fluid flow rate with respect to b is output. The rate of cooling due to the flow at this time is expressed by the following King's equation.

H=(a+bU')(T-Ta) ・---・-41
) However, H: dissipated heat amount, U: flow velocity, T: detection heating element 2
a, surface temperature of 2b, Ta: temperature of fluid (gas). Therefore, if the current flowing through the resistors 81 of the detection heating elements 2a and 2b is I, and the voltage at both ends is V, then the following equation holds true.

H=VR=V"/R... Old...
...(2) Therefore, from equations (1) and (2), V' = R(a + b U")(T - Ta) -
---i3J, and the output voltage of the sensor drive circuits 6a, 6b becomes a function of the flow velocity to the 1/4th power.

Figure 4 (a) and (b) show city gas (13A) as the fluid.
) shows the results of measuring the flow rate and flow velocity (wind speed) when flowing through a supply pipe with a pipe diameter of 5oφ.
a) represents the change in the output voltage of the hot wire flow velocity sensor on the upstream and downstream sides of the flow with respect to the change in flow rate, and (b)
) represents the change in the output voltage of the hot-wire flow rate sensor without the shielding member 3 and the output voltage of the upstream hot-wire type flow rate sensor according to the present invention with respect to changes in flow velocity (wind speed). In this measurement, the shielding member 3 has a plate-like configuration as shown in the figure.

As shown in Fig. 4, the output voltage of the sensor drive circuit of the hot-wire type flow velocity sensor corresponding to the detection heating element located on the downstream side of the flow is smaller than the output voltage of the hot-wire type flow rate sensor on the upstream side. By comparing the output voltages with the comparator 8, it is possible to determine which heating element 2 for detection of the hot wire type flow velocity sensor.
a, 2b on the upstream side and thereby the direction of fluid flow can be detected. Furthermore, Fig. 4(a)
It can be seen that in the embodiment shown in , the direction of flow can be detected up to a gas flow rate of about 0.6rd/h.

In this way, the sensor drive circuit 6a of the hot wire flow rate sensor,
By comparing the output voltages of sensor drive circuit 6b with comparator 8, it is found that, for example, when gas is flowing as shown by the arrow in FIG. 3, the output voltage of sensor drive circuit 6b is higher than the others; The device 8 outputs a signal indicating that the detection heating element 2b side is the upstream side, and the output of the comparator 8 causes the changeover switch 9 to select the sensor drive circuit 6b side corresponding to the detection heating element 2b on the upstream side. Then, the switching operation is performed so that the output voltage is output.

As shown in FIG. 4(b), the output voltage of the hot-wire flow velocity sensor corresponding to the upstream detection heating element 2b is lower than the output voltage when there is no shielding member 3; The functional system of voltage correspondences does not change. Therefore, if the correspondence between the flow velocity and the output voltage is stored in advance, the flow velocity or flow rate can be accurately measured for any output voltage.

As mentioned above, since the output voltage of the sensor drive circuits 6a and 6b is a function of the 1/4th power of the flow velocity, it is necessary to linearize this, but this linearization can be performed as appropriate by analog or digital means. be able to.

For example, in the case of the embodiment, the sensor drive circuit 6a.

After roughly linearly correcting the output voltage of 6b in an analog manner using a squarer 10 to obtain an analog output signal as a function of the 1/2 power of the flow velocity, the output signal is sent to the processing device 11 to
The data is digitally corrected using a conversion table or the like and output to a display or the like (not shown). In the case of this embodiment, there are two problems with analog correction: the circuit is complicated and adjustment is required, and digital correction has poor resolution in areas where the flow velocity is large, that is, in areas where the output voltage is high. It is possible to alleviate the problems and take advantage of the characteristics of both. Incidentally, the influence of irregular velocity fluctuations of the fluid in the fluid supply pipe 12 due to vortices, etc. can be alleviated by calculating the average flow velocity at predetermined time intervals by the processing device 11, and stable measurements can be performed. I can do it.

(Effects of the Invention) As described above, the present invention provides a pair of detection heating elements, each of which constitutes a component of a hot-wire flow velocity sensor, installed at a predetermined distance in the axial direction of a fluid supply pipe to be measured, and between them. A shielding member is installed at the
This has the advantage that the direction of the fluid flow can be detected as well as the flow rate and flow rate of the fluid. Furthermore, according to the present invention, the sensor main body can be constructed in a small size, and it can be installed inside the fluid supply pipe, so this installation can be easily done through a punched hole formed in the fluid supply pipe. There is an advantage that the flow velocity, flow rate, and flow direction of the fluid such as the gas mentioned above in the gas supply pipe or the like can be measured in the state of the live pipe.

[Brief explanation of drawings]

Fig. 1 is an explanatory perspective view showing an example of the configuration of a sensor main body A applied to the present invention, Fig. 2 is a circuit diagram showing an example of the configuration of a hot wire flow rate sensor, and Fig. 3 is a measuring device of the present invention. Figure 3 (a) and (b) are system explanatory diagrams showing an example of the overall configuration of the system, and the flow velocity was measured when city gas (13A) was flowed as a fluid through a supply pipe with a pipe diameter of 50φ. The results are shown, and (a) shows the change in output voltage of the hot wire flow velocity sensor on the upstream and downstream sides of the flow in response to the change in flow rate.
In addition, (b) is an explanatory diagram showing changes in the output voltage of the hot wire type flow rate sensor in the case where there is no shielding member and the output voltage of the upstream side hot wire type flow rate sensor according to the present invention with respect to changes in flow rate. . Symbol t...sensor body, 2a, 2b...heating element for detection, 3...shielding member, 4a, 4b...resistance element for temperature compensation, 5a. 5b...Resistor, 6a, 6b...Sensor drive circuit, ? a, 7b...Amplifier, 8...Comparator, 9...
Changeover switch, 10...Squaring device, 11...Processing device, 12...Fluid supply pipe, 13...Drilling hole, 14...
・Protective cap, 15...Side wall, 16...Top wall, A
...sensor body, B...detection circuit. Figure 1 Figure 2 Procedure for writing amendments) 1. Indication of the case Patent Application No. 136138 of 1990 2. Name of the invention Method and device for measuring fluid flow velocity and flow direction 3. Person making the amendment Relationship with the case Patent Applicant Address: 5-20 Kaigan-chome, Minato-ku, Tokyo Name: Tokyo Gas Co., Ltd. Representative: Kunio Anzai 4, Agent Address: 101 (294) 7341~
2 On August 28, 1990, 7, the statement "Fig. 3 (a), (b)" on page 18, line 13 of the specification of contents of the amendment was changed to "Fig. 4 (a), (b)". I will correct the description.”

Claims (9)

[Claims] (1) A pair of detection heating elements, each forming a component of a hot wire flow velocity sensor, are installed a predetermined distance apart in the axial direction of the fluid supply pipe to be measured, and a shielding member is installed between them. The flow direction of the fluid is detected by comparing the output signals of the hot wire type flow velocity sensor corresponding to a pair of detection heating elements, and the fluid flow rate is detected by the output signal of the hot wire type flow velocity sensor corresponding to the upstream detection heating element. A method for measuring the flow velocity and flow direction of a fluid, characterized by measuring (2) The hot wire flow velocity sensor according to claim 1 includes a pair of detection heating elements installed at a predetermined distance apart from one end of the sensor body, a shielding member installed between them, and A temperature compensation resistor is installed closer to one end of the sensor body than the detection heating element, and each detection heating element and temperature compensation resistor are assembled into a bridge, and the unbalance of each bridge circuit is corrected. A pair of sensor drive circuits are provided to adjust the bridge voltage so that the bridge voltage is zero, and the bridge voltage is adjusted by the sensor drive circuit to maintain the temperature of the detection heating element constant, and at this time, the bridge circuit A fluid flow velocity and flow direction measuring method characterized in that the fluid flow velocity is derived from the output signal of a sensor drive circuit corresponding to the current flowing in the fluid. (3) A pair of detection heating elements are installed at a predetermined distance apart from one end of the sensor body, and a shielding member is installed between them, and the sensor A temperature compensation resistor is installed near one end of the body, each detection heating element and temperature compensation resistor are assembled into a bridge, and the bridge voltage is adjusted so that the unbalance of each bridge is zero. a hot-wire type flow velocity sensor configured by providing a sensor drive circuit, a comparator for comparing output signals of the sensor drive circuit, and the sensor drive circuit to switch and output according to the output signal of the comparator. A detection circuit comprising a changeover switch for selecting a flow rate, and a detection circuit configured to output a signal corresponding to the flow direction by the comparator and a signal corresponding to the flow velocity via the changeover switch. flow velocity and flow direction measuring device (4) A method for measuring the flow velocity and flow direction of a fluid, characterized in that the heating element for detection according to claim 1 or 2 is constituted by a self-heating semiconductor thermistor. (5) A method for measuring the flow velocity and flow direction of a fluid, characterized in that the shielding member according to claim 1 or 2 is configured in a plate shape. (6) A method for measuring the flow velocity and flow direction of a fluid, characterized in that the shielding member according to claim 1 or 2 is configured in a rod shape. (7) A fluid flow velocity and flow direction measuring device characterized in that the heating element for detection according to claim 3 is constituted by a self-heating semiconductor thermistor. (8) A fluid flow velocity and flow direction measuring device characterized in that the shielding member according to claim 1 or 2 is configured in a plate shape. (9) A fluid flow velocity and flow direction measuring device characterized in that the shielding member according to claim 1 or 2 is configured in a rod shape.