JPH04343017A - Vortex flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flow meter that measures the flow rate of a fluid based on the cycle of vortex generation in a Karman vortex street.

0002

BACKGROUND OF THE INVENTION Conventionally, a vortex flowmeter has been used as a flowmeter for measuring flow rate. This vortex flow meter generates a so-called Karman vortex street on the downstream side of a vortex generator installed in a pipe, and measures the flow rate of fluid flowing in the pipe based on the cycle of generation of the vortex. . This type of vortex flowmeter includes an ultrasonic transmitter that transmits ultrasonic waves into the fluid downstream of the vortex generator, and a receiver that receives the ultrasonic waves that are transmitted from the ultrasonic transmitter and propagated through the fluid. An ultrasonic receiving element is provided, and the phases of the ultrasonic waves received by the ultrasonic receiving element and the ultrasonic waves emitted from the ultrasonic transmitting element are compared,
It is known to calculate the flow rate of fluid by determining the vortex generation period of the Karman vortex street from the compared data.

0003

[Problems to be Solved by the Invention] In a vortex flowmeter, when fluid flows normally from upstream to downstream, separation occurs alternately on both sides of the vortex generator, causing the vortex generator to A so-called Karman vortex street is generated on the downstream side of the vortex generator, and is detected by the Karman vortex detection section downstream of the vortex generator. However, if the fluid flows in the opposite direction from the downstream side to the upstream side, no Karman vortex street is generated downstream of the vortex generating body and cannot be detected by the Karman vortex detection section. Therefore, when the fluid is flowing in the normal direction, it is possible to determine that the direction of the fluid flow is normal based on the occurrence of a Karman vortex street in the fluid.
When the fluid is flowing in the opposite direction, the direction of the fluid flow cannot be determined because no Karman vortex street is generated.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a vortex flowmeter capable of determining whether the fluid in the pipe has flowed backward.

[0005]

[Means for Solving the Problems] The vortex flowmeter of the present invention has the following features:
A detection means is provided downstream of a vortex generator provided in the duct for detecting fluctuations in the flow of fluid flowing in the duct and outputting the detected data, and based on the detected data, the vortex generator In a vortex flow meter that is provided with a flow rate calculation means that calculates the flow rate of the fluid by determining the generation period of the Karman vortex street generated in the fluid, the direction of the fluid flow is determined by determining the regularity of the detected data. It is characterized in that it is equipped with a forward/reverse discrimination means.

[0006]

[Operation] According to the vortex flow meter of the present invention, when the detection means detects fluctuations in fluid flow and outputs the detected data,
The forward/reverse determining means determines the regularity of the detected data to determine the direction of fluid flow. If it is determined that the fluid is flowing in the normal direction, the flow rate calculation means calculates the generation period of the Karman vortex street and calculates the flow rate of the fluid.

[0007]

[Embodiment] An embodiment of the present invention will be explained below with reference to FIG. In the figure, reference numeral 1 indicates a conduit through which fluid flows. A vortex generating body 2 having a triangular cross section is provided in the pipe line 1 so as to run substantially perpendicular thereto. and,
As the fluid flows in the pipe line 1 in the direction of arrow A in the figure,
Karman vortex rows 3, 3, . . . are generated on the downstream side of the vortex generator 2. Furthermore, on the downstream side of the vortex generator 2, an ultrasonic transmitting element 5 is provided on the side of the conduit 1 to transmit ultrasonic waves 4 to the fluid flowing in the conduit 1. An ultrasonic source 6 is connected to.

[0008] Also, in the conduit 1, an ultrasonic transmitting element 5 is provided.
An ultrasonic receiving element 8 is provided at a position opposite to the ultrasonic wave transmitting element 5 for receiving the ultrasonic wave 4 transmitted from the ultrasonic transmitting element 5 and propagating in the fluid, and outputting a received signal 7 thereof. and,
This ultrasonic receiving element 8 compares the phase of the received signal 7 with the phase of the ultrasonic transmission signal 9 directly inputted from the ultrasonic source 6 to detect a change in the phase of the received ultrasonic wave 4. , a phase comparison circuit (detection means) that outputs the detection data 10
11 are connected. The phase comparison circuit 11 also includes a flow rate calculator (flow rate calculation means) 12 and a forward/reverse discriminator (
Forward/reverse discrimination means) 13 is connected, and the phase comparison circuit 1
Detection data 10 outputted from 1 is inputted respectively. The forward/reverse discriminator 13 outputs a forward/reverse discrimination signal 14 to the flow rate calculation unit 12, and the fluid calculation unit 12 is in a state where the detection data 10 outputted from the phase comparator 11 and the detection data 10 are the same. Based on the forward/reverse discrimination signal 14 outputted from the inverse discriminator 13, the flow rate of the fluid is calculated, and the result of the calculation is output to the terminal 16.

Here, when the fluid in the pipe 1 is flowing normally in the direction of arrow A in the figure, there are Karman vortex streets 3,
3... occurs. Therefore, the phase of the ultrasonic wave 4 is modulated by the Karman vortex rows 3, 3, . . . . Then, when the ultrasonic wave whose phase is modulated by the Karman vortex streets 3, 3... is Fourier-transformed, the power spectrum of the frequency of this ultrasonic wave becomes the frequency at which the Karman vortex streets 3, 3... are generated, as shown in Fig. 2. It will be in a state where it has a peak in the band. On the other hand, when the fluid in the pipe 1 is flowing in the opposite direction (the direction of arrow B in the figure), no Karman vortex street 3, 3, etc. are generated in the fluid, but countless small vortices called turbulents are generated. Occur. Therefore, the phase of the ultrasonic wave 4 is also modulated by the vortex of this turbulent. When the ultrasonic wave whose phase is modulated by the turbulent eddy is Fourier-transformed, the power spectrum of the ultrasonic frequency contains a so-called 1/f characteristic component that is inversely proportional to the frequency, as shown in Figure 3. appear. That is, the forward/reverse discriminator 13 performs peak judgment and 1/1 from the detection data 10.
By determining the regularity of the f characteristic, the modulation characteristic of the frequency of the ultrasonic wave is read, the direction in which the fluid flows is determined, and a forward/reverse discrimination signal 14 is output as a result. Then, the forward/reverse discriminator 13 uses the detected data 1
If it is determined that the fluid is flowing in the normal direction from 0, the normal direction signal 14a is output as the forward/reverse determination signal 14, and if it is determined that the fluid is flowing in the reverse direction, the normal direction signal 14a is output as the forward/reverse determination signal 14. A reverse direction signal 14b is output.

Next, the flow rate measurement operation using the vortex flowmeter having the above configuration will be explained with reference to the flowchart shown in FIG. Step SP1 The ultrasonic wave 4 transmitted from the ultrasonic transmitting element 5 and propagated in the fluid is received by the ultrasonic receiving element 8, and the received signal 7 is output from the ultrasonic receiving element 8. Step SP2 The phase comparator 11 compares the phases of the received signal 7 and the ultrasonic transmission signal 9 directly input from the ultrasonic source 6. Step SP3: Phase modulation of the ultrasonic wave 4 propagated in the fluid is detected by the phase comparator 11, and detection data 10 is output. Step SP4 The forward/reverse discriminator 13 performs peak judgment and 1
By determining the /f characteristic, the modulation characteristic of the frequency of the ultrasonic wave is read and the direction in which the fluid flows is determined. Here, if the forward/reverse discriminator 13 determines from the detection data 10 that the direction of the fluid flow is the normal direction (arrow A direction in FIG. 1), the process moves to step SP5, and the flow direction of the fluid is the reverse direction. (in the direction of arrow B in FIG. 1), the process moves to step SP8.

Step SP5 Normal direction signal 14 is sent from the forward/reverse discriminator 13 to the flow rate calculator 12.
a is output. Step SP6: The flow rate calculator 12 inputs the normal direction signal 14a, calculates the generation period of the Karman vortex streets 3, 3, etc. occurring in the fluid based on the detection data 10, and calculates the flow rate of the fluid. do. Step SP7 The calculation result 15 is output from the flow rate calculator 12, and the terminal 16
The flow rate is displayed on a display (not shown) connected to the flow rate, and the process moves to step SP1. Step SP8 Reverse direction signal 14b from forward/reverse discriminator 13 to flow rate calculator 12
is output. Then, the flow rate calculator 12 outputs the reverse direction signal 1.
4b, the flow rate calculator 12 outputs a display signal, etc., and a display connected to the terminal 16 displays that the fluid is flowing in the opposite direction, and step S
Move to P1.

As described above, according to the vortex flow meter of the above embodiment, in order to calculate the flow rate of the fluid, simple signal processing is performed on the phase modulation of the ultrasonic wave 4 propagated into the fluid, and the flow rate of the fluid is calculated. By providing a forward/reverse discriminator 13 that discriminates the direction,
A vortex flow meter with a forward/reverse discrimination function can be obtained without separately providing a forward/reverse discrimination sensor or the like for determining the direction of fluid flow. Therefore, it is possible to eliminate the cost increase caused by separately providing a new forward/reverse discrimination sensor. Note that the configuration of the vortex flowmeter of the above embodiment is not limited to the embodiment.

[0013]

[Effects of the Invention] As explained above, according to the vortex flowmeter of the present invention, the following effects can be obtained. By providing a forward/reverse discrimination means that can perform forward/reverse discrimination to determine the direction of fluid flow through simple signal processing without separately installing a new sensor, it is extremely easy to do so without increasing costs. It can be a vortex flowmeter with a forward/reverse discrimination function.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a vortex flowmeter for explaining the configuration of the vortex flowmeter of the present invention.

FIG. 2 is a diagram showing the frequency power spectrum of ultrasonic waves when fluid is flowing in a normal direction.

FIG. 3 is a diagram showing the frequency power spectrum of ultrasonic waves when fluid is flowing in the opposite direction.

FIG. 4 is a flowchart illustrating the flow rate measurement operation using the vortex flowmeter of the present invention.

[Explanation of symbols]

1 Pipeline 2 Vortex generator 3 Karman vortex street 10 Detection data 11 Phase comparator (detection means) 12 Flow rate calculator (flow rate calculation means) 13 Forward/reverse discriminator (forward/reverse discriminator)

Claims (1)

[Claims] 1. A detection means for detecting fluctuations in the flow of fluid flowing in the pipe on the downstream side of a vortex generator provided in the pipe and outputting the detected data, In the vortex flowmeter, the vortex flowmeter is provided with a flow rate calculation means for calculating the flow rate of the fluid by determining the generation period of the Karman vortex street generated in the fluid by the vortex generator, and determining the regularity of the detected data to calculate the flow rate of the fluid. A vortex flow meter characterized by comprising a forward/reverse determining means for determining the direction of flow.