JP2002139356A - Flow measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow measuring method capable of measuring the flow of a fluid with accuracy. SOLUTION: A variable X is obtained by substituting the propagation time of an ultrasonic waves in equation [1], and a coefficient K and an intercept C equation [2] are selected according to the variable X. The variable X is substituted in the equation [2] whose coefficient K and the intercept C are selected to obtain a flow Qm per designated time: X=(Tg-Tj)/(Tg×Tj)...[1] Qm=KX+C...[2].

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 method for measuring a flow rate of a gas or other fluid using ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the flow rate of a gas or other fluid, a flow rate measurement method using ultrasonic waves is known.

The principle of such a flow rate measuring method will be described below with reference to FIG. In FIG. 4, reference numeral (1) denotes a flow measuring tube as a flow measuring unit in which a fluid such as a gas flows. Ultrasonic vibrators (2) and (3) are arranged in the flow measurement tube (1) at a predetermined distance along the flow direction. The ultrasonic vibrators (2) and (3) are driven by a driving pulse from a driving pulse generating circuit (4) to vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. , Its ultrasonic transducers (3) (2)
The received wave when is vibrated is output from the receiving amplifier circuit (5).

The propagation time Tj until the ultrasonic wave transmitted from the upstream ultrasonic vibrator (2) in the forward direction with respect to the flow is received by the downstream ultrasonic vibrator (3). ,
Per predetermined time based on the propagation time Tg until the ultrasonic wave transmitted from the downstream ultrasonic transducer (3) in the reverse flow direction to the flow is received by the upstream ultrasonic transducer (2). Is obtained. Then, the flow rate Qs per predetermined time is measured every predetermined time, and the flow rate Qs of the entire fluid is obtained by integrating the flow rates Qs per predetermined time.

In FIG. 4, reference numeral (6) denotes a switching circuit for switching the connection between each of the ultrasonic transducers (2) and (3), the drive pulse generating circuit (4) and the receiving amplifier circuit (5). The pulse generation circuit (4) is connected to the ultrasonic vibrator (2), and the ultrasonic vibrator (3) is connected to the receiving amplifier circuit (5) to measure the propagation time Tj in the forward flow direction. )
The drive pulse generating circuit (4) and the ultrasonic vibrator (3), and the ultrasonic vibrator (2) and the receiving amplifier circuit (5) are switched so as to be connected by the operation of (1), and the propagation time Tg in the reverse flow direction is changed. It is meant to be measured.

By the way, the flow rate Qs per predetermined time is
Is, specifically, the propagation time Tj of the ultrasonic wave in the forward flow direction described above.
And the propagation time Tg of the ultrasonic wave in the reverse flow direction are substituted into the following equation [3]. And the following equation [3]
Was always constant regardless of the flow rate of the fluid. Qs = Ks × (Tg−Tj) / (Tg × Tj) + Cs [3] Qs: flow rate per predetermined time Ks: coefficient for unit conversion Cs: intercept for correction Tj: flow of fluid Propagation time of ultrasonic wave in the forward flow direction Tg: Propagation time of ultrasonic wave in the reverse flow direction to the flow of fluid

[0007]

However, since the characteristics of the flow rate measuring device change with the flow rate of the fluid, a uniform calculation in which the coefficient Ks and the intercept Cs are constant as in the above equation [3] is not performed. There is a problem that an error occurs and the flow rate of the fluid cannot be measured with high accuracy.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a flow rate measuring method capable of accurately measuring the flow rate of a fluid.

[0009]

According to the present invention, in order to solve the above-mentioned problems, ultrasonic transducers are arranged in an opposed state along a flow direction of a measurement fluid flowing through a flow rate measuring section, and each of the ultrasonic transducers is disposed. Ultrasonic waves are mutually generated and transmitted from the transducers, the transmitted ultrasonic waves are mutually received, a measured flow rate Qm per predetermined time is obtained based on the propagation time of the ultrasonic waves, and the measured flow rate Qm per predetermined time is calculated. In the flow rate measuring method for obtaining the flow rate Q of the entire fluid by integrating
A variable X is obtained by substituting the propagation time of the ultrasonic wave into the following equation [1], and a coefficient K of the following equation [2] is determined according to the variable X.
And the intercept C are selected, and the flow rate Qm per predetermined time is obtained by substituting the variable X into the following equation [2] in which the coefficient K and the intercept C are selected. X = (Tg−Tj) / (Tg × Tj) [1] Tg: Propagation time of ultrasonic wave in the reverse flow direction to the flow of fluid Tj: Propagation of ultrasonic wave in the forward flow direction to the flow of fluid Time Qm = KX + C ... [2] Qm: Flow rate per predetermined time K: Coefficient for unit conversion C: Intercept for correction According to this, the coefficient of the above equation [2] according to the fluid flow rate K
In addition, since the intercept C is changed, the flow rate of the fluid can be accurately obtained without being affected by the change in the characteristics of the flow measurement device due to the flow rate of the fluid.

Further, the coefficient K and the intercept C are a coefficient and an intercept set in accordance with the range of the variable X.
When selecting from the intercept table, the coefficient and the intercept can be selected easily and reliably.

The coefficient / intercept table is calculated based on the relationship between the variable X and a normal flow rate Qm measured by a reference device having high measurement accuracy, and is transmitted from the reference device side. When setting the coefficient K and the intercept C, the coefficient K and the intercept C can be easily and reliably set in the coefficient / intercept table.

[0012]

FIG. 1 shows a flow rate measuring device for implementing a flow rate measuring method according to an embodiment of the present invention. In FIG. 1, (1) is a flow measuring tube as a flow measuring unit, (2) and (3) are ultrasonic vibrators arranged at a predetermined distance along a flow direction, and (4) generates a driving pulse. (5) is a receiving amplifier circuit that outputs a reception wave when ultrasonic waves are received by the ultrasonic vibrators (2) and (3), and (6) is an ultrasonic vibrator (2) (3) ) And a switching circuit for switching the connection between the driving pulse generating circuit (4) and the receiving amplifier circuit (5), which are the same as those shown in FIG. The direction from the ultrasonic vibrator (2) to the ultrasonic vibrator (3) is a forward flow direction of the fluid, and the direction from the ultrasonic vibrator (3) to the ultrasonic vibrator (2) is the reverse flow direction of the fluid. And

In this embodiment, a coefficient / intercept table (7) in which a coefficient Ki and an intercept Ci described later are set, and a total flow rate storage unit (8) for accumulatively storing a flow rate Qm of the fluid per predetermined time are provided. A CPU (9) for controlling the pulse generating circuit (4), a receiving amplifier circuit (5), a switching circuit (6), a coefficient / intercept table (7), and an overall flow rate storage section (8). Have been.

The CPU (9) is roughly divided into a measurement process for measuring the propagation times Tj and Tg of the ultrasonic wave, a calculation process for calculating the flow rate Qm per predetermined time, and a process for calculating the flow rate Qm per predetermined time. And a function of executing an integrating process for obtaining the flow rate Q of the entire fluid by storing the integrated amount.

More specifically, the measurement process will be described. By controlling the switching circuit (6) by the CPU (9), the drive pulse generation circuit (4), the ultrasonic vibrator (2), and the ultrasonic vibrator ( 3) and the receiving amplifier circuit (5) are connected to each other, and after measuring the propagation time tj in the forward flow direction, the switching circuit (6) is again controlled by the CPU (9), whereby the drive pulse generating circuit (4) And the ultrasonic vibrator (3), and the ultrasonic vibrator (2) and the receiving amplifier circuit (5) are switched so as to be respectively connected, and the propagation time tg in the reverse flow direction is measured. The measurement of the propagation times tj and tg is
The time from when the ultrasonic wave is transmitted to the time when the received wave output from the reception amplifier circuit (5) reaches a predetermined level or after the zero-cross time is used as a reception time using a clock wave or the like. Ask.

More specifically, the arithmetic processing will be described. The propagation time Tj of the ultrasonic wave in the forward flow direction measured in the above-described measurement processing and the propagation time Tg of the ultrasonic wave in the backward flow direction are measured.
Are substituted into the following equation [1] to obtain the variable X
Ask for. X = (Tg−Tj) / (Tg × Tj) [1] Tg: Propagation time of ultrasonic wave in the reverse flow direction to the flow of fluid Tj: Propagation of ultrasonic wave in the forward flow direction to the flow of fluid Time And, according to the variable X obtained by the above equation [1],
The coefficient Ki and the intercept Ci of the following equation [2] are selected. In this embodiment, as shown in Table 1 below, the coefficient Ki and the intercept Ci are selected based on a coefficient / intercept table in which the coefficient and the intercept are set according to the range of the variable X. For example, when the variable X is within the range of X2 ≦ X <X3, the coefficient K2 and the intercept C are determined based on the coefficient / intercept table.
Select 2.

[0017]

[Table 1]

Then, the flow rate Qm per predetermined time is calculated by substituting the variable X into the following equation [2] in which the coefficient Ki and the intercept Ci are selected. Qm = KiXi + Ci [2] Qm: Flow rate per predetermined time Ki: Coefficient for unit conversion Ci: Intercept for correction Ki and Ci in the coefficient / intercept table are used in the manufacturing stage of the flow rate measuring device or In the test phase, the variables Xi
And the relationship between the normal flow rate Qm per predetermined time measured by a highly accurate reference device, and
In the above equation [2], the normal flow rate Qm is set to be an optimal value so that the normal flow rate Qm can be calculated with almost no error from the variable Xi. In particular, the intercept Ci has a meaning of correction when the flow rate is 0, and therefore, a value adjusted by detecting no flow rate is set.

The reason why the flow rate Qm per predetermined time is calculated by the above equation [2] is as follows. That is, the propagation time tj until the ultrasonic wave transmitted from the ultrasonic vibrator (2) is received by the ultrasonic vibrator (3) is tj = L / (c + V) (3) L: measurement Length of tube c: velocity of ultrasonic wave V: velocity of fluid, and propagation time until ultrasonic wave transmitted from ultrasonic vibrator (3) is received by ultrasonic vibrator (2) tg is expressed as tg = L / (c−V) (2). From these equations [1] and [2], the fluid velocity V
V = L / 2 × (Tg−Tj) / (Tj × Tg) (4)

Therefore, the flow rate Qm per predetermined time is as follows: Qm = V × S × t = (L × S × t) / 2 × (Tg−Tj) / (Tj × Tg) (5) Since the flow velocity S: the cross-sectional area of the measuring tube t: a predetermined time (for example, 2 seconds), (L × S × t) / 2 in the above equation [5]
Is a coefficient Ki, and a coefficient Ci for correction is added, whereby the operation equation of the above equation [2] is obtained.

More specifically, the integration process is described in which the flow rate Qm per predetermined time calculated in the above-described calculation process is cumulatively stored in the entire flow rate storage unit (8) every predetermined time.

Next, a flow rate measuring method using the apparatus shown in FIG. 1 will be described with reference to flowcharts shown in FIGS. In the following description and drawings, “step”
Is abbreviated as “S”.

First, in the measurement process of S1, the CPU
By controlling the switching circuit (6) by (9),
The drive pulse generation circuit (4) and the ultrasonic vibrator (2), the ultrasonic vibrator (3) and the receiving amplifier circuit (5) are connected to each other, and the forward flow time tj is measured.
By controlling the switching circuit (6) by U (9), the drive pulse generation circuit (4) and the ultrasonic vibrator (3)
The ultrasonic transducer (2) and the receiving amplifier circuit (5) are switched so as to be connected to each other, the propagation time tg in the reverse flow direction is measured, and the process proceeds to S2. The propagation time tj in the forward flow direction and the propagation time tg in the backward flow direction may be measured one by one, or a plurality of each may be measured and averaged.

In the calculation process of S2, as shown in the flowchart of FIG. 3, in S21, the propagation time tj in the forward flow direction and the propagation time tg in the backward flow direction measured in the above-described measurement process are measured.
To the variable X by substituting
Is calculated, and the process proceeds to S22.

In S22, initialization is performed so that i = 0, and the flow advances to S23.

In S23, it is determined whether or not the variable X satisfies "X <X1".
O), proceed to S24, add 1 to i, return to S23 again, and repeat the processing of S23 and S24 until the variable X satisfies “X <Xi”.

On the other hand, if "X <Xi" is satisfied in S23 (YES in S23), the process proceeds to S25, and Table 1 shown in FIG.
"Xi-1≤X <Xi" from the variable / intercept table shown in FIG.
Then, the coefficient Ki and the intercept Ci are selected, and the process proceeds to S26.

In S26, the flow rate Qm per predetermined time is calculated by substituting the variable X into the above equation [2] in which the coefficient Ki and the intercept Ci are selected, and the flow proceeds to the integration processing in S3.

In the integrating process in S3, the flow rate Qm per predetermined time calculated in the above-described calculating process is integratedly stored in the overall flow rate storage unit (8). The flow rate Q of the entire fluid stored in the total flow rate storage unit (8) is displayed on a display unit (not shown) as necessary.

According to this flow rate measuring method, the coefficient Ki and the intercept Ci of the above equation [2] are changed in accordance with the variable X obtained by the above equation [1]. The flow rate can be determined accurately.

In this embodiment, the coefficient / intercept table is stored separately from the CPU (9).
PU (9) ROM (Read Only Memory)
y: data read-only memory).

The coefficient / intercept table (7)
The coefficient Ki and the intercept Ci, which are calculated based on the relationship between the variable X and the normal flow rate Qm measured by the reference device with high measurement accuracy and transmitted from the reference device, may be set. Good. According to this, the coefficient Ki and the intercept Ci can be easily and reliably set in the coefficient / intercept table.

The coefficient Ki and the intercept Ci of each range of the variable X are calculated by the above equation [2] constituted by the coefficient Ki and the intercept Ci, and the coefficient K of the range of the variable X adjacent thereto.
The above equation [2] composed of i ± 1 and intercept Ci ± 1
Is preferably set so that the boundary portion of the variable X coincides and the above equation [2] in each range of the variable X becomes a continuous polygonal line.

Although the coefficient Ki and the intercept Ci are set stepwise for each range of the variable X, the coefficient Ki and the intercept Ci may be set continuously according to the variable X.

[0035]

According to the first aspect of the present invention, the coefficient and intercept of the above equation [2] are changed according to the variable X obtained by the above equation [1]. The flow rate of the fluid can be accurately determined.

According to the second aspect of the present invention, the coefficient and the intercept can be easily and reliably selected.

According to the third aspect of the present invention, the coefficient K and the intercept C can be easily and reliably set in the coefficient / intercept table.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a flow measuring device for carrying out the present invention.

FIG. 2 is a flowchart showing the overall operation of the flow measuring device of FIG.

FIG. 3 is a flowchart illustrating an operation of a calculation process in FIG. 2;

FIG. 4 is a block diagram showing a conventional flow measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Flow measuring tube 2, 3 ... Ultrasonic transducer 4 ... Pulse generation circuit 5 ... Reception amplification circuit 6 ... Switching circuit 7 ... Coefficient / intercept table 8 ... Whole Flow rate storage unit

Continued on the front page (72) Inventor Tadayuki Minami 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. (72) Inventor Shigeru Tagawa 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Osaka Gas stock Inside the company (72) Inventor Kazuo Eshita 10 Kaneda-machi, Shimogyo-ku, Kyoto-shi Kansai Gas Meter Co., Ltd. (72) Inventor Eiji Nakamura 10 Kanoda-jigada-cho, Shimogyo-ku, Kyoto Kansai Gas Meter Co., Ltd. 72) Inventor: Akio Kono, Kansai Gas Meter Co., Ltd. (10) Kansai Gas Meter Co., Ltd. (10) Kansai Gas Meter Co., Ltd. (72) Inventor Tetsuya Yasuda Tetsuya Kadota Town, Shimogyo Ward, Kyoto City 2F035 DA19 DA22 DA23

Claims (3)

[Claims] An ultrasonic transducer is disposed in an opposed state along a flow direction of a measurement fluid flowing through a flow measuring unit, and ultrasonic waves are generated and transmitted from each ultrasonic transducer, and the transmitted ultrasonic waves are transmitted. Are mutually received, a measured flow rate Qm per predetermined time is obtained based on the propagation times of the ultrasonic waves, and a flow rate measuring method of obtaining the flow rate Q of the entire fluid by integrating the measured flow rate Qm per predetermined time, A variable X is obtained by substituting the propagation time of the ultrasonic wave into the following equation [1], and a coefficient K of the following equation [2] is determined according to the variable X.
A flow rate measuring method for determining the flow rate Qm per predetermined time by substituting the variable X into the following equation [2] in which the coefficient K and the intercept C are selected. X = (Tg−Tj) / (Tg × Tj) [1] Tg: Propagation time of ultrasonic wave in the reverse flow direction to the flow of fluid Tj: Propagation of ultrasonic wave in the forward flow direction to the flow of fluid Time Qm = KX + C ... [2] Qm: Flow rate per predetermined time K: Coefficient for unit conversion C: Intercept for correction 2. The coefficient K and the intercept C are defined by the variable X
The flow rate measuring method according to claim 1, wherein the coefficient and the intercept are selected from a coefficient / intercept table in which the coefficient and the intercept are set according to the range. 3. The coefficient / intercept table stores the variable X
And the normal flow rate Q measured by a standard with high measurement accuracy
The flow rate measuring method according to claim 2, wherein the coefficient K and the intercept C calculated based on the relationship with m and transmitted from the reference device side are set.