JPS62140025A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To make it possible to measure a mass flow rate with good accuracy without receiving the effect of the pulsating pressure in a measuring fluid or temp. by utilizing the pressure fluctuation generated between pressure guide tubes, by providing the pressure guide tubes to the pipe wall of a pipeline in the upstream and downstream sides of the vortex generator arranged in the pipeline. CONSTITUTION:The titled flowmeter is constituted of the vortex generator 2 provided to a pipeline 1 through which a measuring fluid flows, the pressure guide tube 11 (11, 13) provided to the pipe wall of the pipeline 1 in the upstream (downstream) side of said vortex generator 2 at one end thereof, the vortex flow speed detection part 3 (pressure detection part 4) connected to the other ends of the pressure guide tubes 12, 13 (11, 12) and a dividing part 5 dividing the output of a detection part 4 by the output of a detection pipe 3. When the measuring fluid flows through the pipeline 1, a vortex is generated in the generator 2 to advance along the pipe wall. Pressure fluctuation proportional to vortex generation frequency is generated in the pressure guide tubes 12, 13 and the flow speed of the fluid is measured by the detection part 3. When the vortex is discharged from the vortex generator 2, pressure difference is generated between the upstream and downstream sides of the vortex generator 2 in the pipeline 1. This pressure difference is measured by the detection part 4 through the pressure guide tubes 11, 12 and the output of the detection part 4 is processed by a dividing part to measure a mass flow amount.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mass flowmeter that utilizes the vortex generation frequency and pressure loss caused by the generation of Karman vortices by vortex generators.

<vF, Next Technique) FIG. 6 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, 1 is a conduit through which a fluid to be measured flows, and 2 is a vortex generator disposed perpendicular to the conduit.

When the measuring body flows through the pipe 1 as indicated by the arrow FLOW, the vortex generating body 2 experiences an average drag force as indicated by the arrow FD.

A fluctuating lift force as shown by arrow F is generated, and a pressure loss ΔP is generated between the upstream side and the downstream side of the vortex generator 2.

If the density is ρ and the velocity is V, then the product of the density ρ and the square of the velocity V, that is, ρv
Proportional to 2. By dividing this by the vortex frequency (volume flow rate) fv which is proportional to the speed, the quality fl flow t can be obtained.

Variable lift pLoc±CL÷ρv2 Pressure drop Δpoco dooρv2 ■ Vortex frequency Fv=stT=Kv Here, C9; Average drag coefficient C0; Variable lift coefficient C1: Pressure loss coefficient st; Strohals number d; Diameter of vortex generator (invention However, in the method of measuring the average drag force F and the fluctuating lift force FL, the cessor is installed on the vortex generator, so it is difficult to manufacture due to various restrictions.

The present invention solves this problem.

An object of the present invention is to provide a mass flowmeter with good accuracy that is not affected by pulsating pressure or temperature in a fluid to be measured.

(Means for Solving the Problem) In order to violate this objective, the present application discloses a conduit through which a measurement fluid flows, a vortex generator provided in the core conduit, and a vortex generator provided on the upstream side of the vortex generator. A first pressure impulse pipe having one end provided on the pipe wall of the pipe line, and a second pressure pipe having one end opposite to each other on the pipe wall of the pipe line downstream of the vortex generator. a third impulse pipe; an overflow rate detection section connected to the other end of the third pressure impulse pipe and detecting the vortex generation frequency from the differential pressure between the second and third pressure impulse pipes to detect the flow velocity of the measurement fluid; a pressure detection section connected to the other end of the second pressure impulse tube and detecting the pressure loss of the measurement fluid based on the vortex generator from the pressure of the first and @2 pressure impulse tubes; The mass flowmeter is configured to include a dividing section that divides by the output of the overflow speed detecting section.

(Function) In the above configuration, when the measurement fluid flows through the pipe, a vortex is generated due to the presence of the vortex generator and moves against the pipe wall.

Since the center of the vortex is a negative pressure and the vortices are generated alternately on the left and right sides, pressure fluctuations proportional to the frequency of vortex generation occur in the second and third pressure guiding tubes provided on the pipe wall. Utilizing this, the flow rate of the measured fluid can be determined in the overflow rate detection section.

On the other hand, when a vortex is released from the vortex generator, a pressure difference occurs in the pressure distribution in the pipe between the upstream side and the downstream side of the vortex generator due to pressure loss due to the vortex generator.

This pressure loss is measured by a pressure detection section via the first and second pressure guiding pipes.

The mass flow rate can be measured by dividing the output of the pressure detection section by the output of the overflow detection section using the division section.

Examples will be described below.

(Example) FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is a conduit through which a fluid to be measured flows, and 2 is a vortex generator disposed perpendicular to the conduit. Reference numeral 11 denotes a first pressure impulse pipe having one end provided on the pipe wall of the pipe line 1 on the upstream side of the vortex generator 2 . Reference numerals 12 and 13 refer to second vortex generators having one ends facing each other on the pipe wall of the pipe line 1 on the downstream side of the vortex generator 2. This is the third impulse pipe. 3 is connected to the other ends of the second and third pressure impulse pipes 2 and 3, and detects the vortex generation frequency fv from the differential pressure ΔP2 between the second and third pressure impulse pipes to detect the flow velocity of the measured fluid. This is a flow velocity detection section. 4 is the first. This is a pressure detection unit that detects the pressure loss ΔP1 of the measurement fluid based on the vortex generator 2 from the pressure of the 29th impulse pipe. 5 is a dividing unit that divides the output of the pressure detecting unit 4 by the output of the overflow rate detecting unit 3.

FIG. 2 is a block diagram of one embodiment of the signal processing circuit, and shows an example in which a capacitive sensor is used as the detection sensor.

In the figure, the capacitor C measures the pressure loss ΔP1, and the capacitor C2 measures the fluctuation frequency of the differential pressure ΔP2, that is, the vortex generation frequency fv. 61 is a low-pass filter circuit that receives the signals of capacitors 01 and 02 and absorbs the DC component pressure loss ΔP.
In addition to this, alternating current components such as the vortex generation frequency fV of the alternating current component and the pulsating pressure ΔP of the measured fluid are removed to obtain a direct current voltage E61. 62 is a DC amplifier, and DC voltage E6
A filter circuit 63 removes low frequency or high frequency noise from the signal detected by the capacitor 02 to obtain an AC voltage E63.

64 is an AC amplifier that amplifies the AC' bottom pressure E63 and converts it into an AC voltage E64. 65 is a Schmitt trigger circuit,
The AC voltage B63 is converted into a constant level pulse signal P65. A 66-digit F/V converter converts the pulse signal P65 into a DC voltage E66 proportional to its frequency. 6
7 performs a desired operation on the output E661E6° of the dividing circuit f −F/'V :y7 bar 166 and the Do amplifier 62, and outputs a signal B related to the density or mass flow rate of the fluid.
Take out 67. 68 is a switch circuit, and C amplifier 6
When the AC signal E64 from 4 no longer reaches the set trigger level of the Schmitt circuit 65, the output of the divider circuit 67 is set to 0 by the signal of the comparator 69.

In the above configuration, when the measurement fluid flows through the pipe line 1, a vortex is generated due to the presence of the vortex generator 2, and the fluid flows along the pipe wall. Since the center of the vortex is negative pressure and the vortices are generated alternately on the left and right sides, a differential pressure fluctuation proportional to the vortex generation frequency fv occurs in the second and third pressure guiding holes provided in the tube wall. This differential pressure ΔP
2, the flow velocity of the fluid to be measured can be determined in the eddy flow velocity detecting section 3.

On the other hand, when a vortex is released from the vortex generator 2, the pressure distribution in the pipe line 1 is such that, as shown in FIG. A pressure difference occurs due to the ΔP process. This pressure loss ΔP1 is
The pressure is measured by the pressure detecting section 4 via the pressure guiding pipes 11 and 12 of the . This pressure loss ΔP1 is expressed by the following equation.

The value 0 is a constant determined by the size and shape, and in a streamlined cross-sectional shape that does not generate a vortex, the pressure becomes an extremely small value. Fourth
The figure shows experimental values of pressure loss ΔPs versus flow velocity V in a vortex generator with a trapezoidal cross section.

Now, as shown in FIG. 5, a pulsating pressure ΔPn normally exists in the fluid to be measured, which becomes quite large if the driving source of the fluid to be measured is a pump that makes reciprocating or rotating motion. This pulsating pressure ΔPn propagates within the conduit 1 almost uniformly.

However, the second. Since the signals enter the pressure impulse pipes 12 and 13 of @3 in the same phase, they are canceled and do not pose a problem in the measurement of the differential pressure ΔP2.

In the signal processing circuit shown in FIG. 2, the pressure loss ΔPI is measured at the capacitor 0, and the fluctuation frequency of the differential pressure ΔP, that is, the vortex generation frequency fv is measured at the capacitor 0. A signal of pressure loss ΔP1 detected by capacitor 0 passes through a low-pass filter 61 and is amplified by a Do amplifier 62.

On the other hand, the vortex generation frequency fv detected by the capacitor 02 passes through the filter circuit 63, is amplified by the 0M1a device 63, is converted into a Hals signal of a constant level by the seamit trigger circuit, and is converted into a pulse signal by the F/v converter. is converted into a DC voltage proportional to its frequency.

In the division circuit 67, the signal amplified by the DO amplifier 62 is divided by the signal converted by the F/'V converter 66.

As a result, the mass flow rate of the measurement fluid can be measured.

In this case, in the device of the present application, the senna portion is not in the vortex generator 2 but is located outside the conduit 1, so that it is not directly affected by the fluid to be measured and provides highly reliable temperature characteristics and the like. Moreover, since it is not in the vortex generator 2, there is no dimensional restriction due to the vortex generator 2, so it is easy to manufacture and can be manufactured at low cost.

Furthermore, it has advantages such as not being affected by pulsating pressure. If the pulsating pressure is P=λsinωt (ω=2πf), the maximum value of the pulsating pressure noise applied in the direction of the drag of the vortex generator 2 is 2π
x) There will be 1x-Lx people. Here, h is the length of the pipe line 1 of the vortex generator 2 in the axial direction, as shown in FIG.

Further, since the differential pressure detection part is located outside the pipe line 1, Schilling liquid or the like can be used, so that measurement can be performed even on high-temperature fluids. Although it is necessary to measure the absolute value of the pressure loss ΔP1, since it is measured as a direct current component, damping due to the sealing liquid does not pose a problem.

Moreover, since the differential pressure ΔP2 need only detect the vortex frequency rather than the absolute value, a decrease in the absolute value due to damping does not pose much of a problem. In addition, the differential pressure detection part is heat resistant.
In addition, if the temperature characteristics are poor, it is sufficient to use sealing liquid only on the pressure loss ΔP1 measurement side.

In the above embodiment, a capacitive sensor was used in the differential pressure detection part, but the sensor is not limited to a capacitive sensor, and of course any sensor that can detect differential pressure may be used. be.

(Effects of the Invention) As explained above, the present application includes a pipe line through which a measurement fluid flows, a vortex generator provided in the pipe line, and one end on the pipe wall of the pipe line on the upstream side of the vortex generator. a first impulse pipe provided with;
@2. One ends are provided opposite to each other on the pipe wall of the pipe line on the downstream side of the vortex generator. a third impulse pipe; a vortex flow velocity detection section connected to the other end of the third impulse tube and configured to detect the vortex generation frequency from the differential pressure between the second and third impulse tubes to detect the flow velocity of the measurement fluid; 1st. a pressure detection section that is connected to the other end of the second impulse tube and detects the pressure loss of the measurement fluid based on the vortex generator from the pressure of the first and second impulse tubes; Since the mass flowmeter is configured to include a dividing section that divides by the output of the vortex flow velocity detection section, the senna section is not inside the vortex generator but outside the pipe, so that the measurement fluid is It is not directly affected by temperature, etc., and can have highly eccentric temperature characteristics. Furthermore, it is easy to manufacture and can be manufactured at low cost without being subject to size restrictions due to the vortex generator. Furthermore, it is obtained that is not affected by pulsating pressure. Also, if you use sealing liquid etc.
Furthermore, it becomes possible to measure high-temperature measurement fluids as well.

Therefore, according to the present invention, it is possible to realize a mass flowmeter with good accuracy that is not affected by pulsating pressure or temperature in the fluid to be measured.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIG.
3 to 5 are diagrams illustrating the operation of FIG. 1, and FIG. 6 is a diagram illustrating the configuration of a conventional example that has been generally used. DESCRIPTION OF SYMBOLS 1...Pipe line, 11...1st pressure impulse pipe, 12...2nd pressure impulse pipe, 13...3rd pressure impulse pipe, 2...vortex generator, 3...vortex Flow rate detection section, 4... Pressure detection section, 5...
- Divide unit, 61...Low pass filter, 62...D
o amplifier, 63... filter circuit, 64... AC amplifier, 65... trigger circuit, 66...
F, /'V converter, 67... divider, 68...
Switch circuit, 69... Comparator, ΔP1...
Pressure loss, ΔP2...differential pressure, fv...vortex generation frequency. Figure 5 Figure 6 Figure 3 Figure 4 → Vrrvc.

Claims (1)

[Claims] a conduit through which a measurement fluid flows, a vortex generator provided in the conduit, a first impulse tube having one end provided on a pipe wall of the conduit upstream of the vortex generator, and the vortex generator. second and third ends facing each other on the tube wall of the conduit on the downstream side of the body;
and a vortex which is connected to the other ends of the second and third impulse tubes and detects the vortex generation frequency from the differential pressure between the second and third impulse tubes to detect the flow velocity of the measurement fluid. a flow velocity detecting section; a pressure detecting section connected to the other ends of the first and second impulse tubes and detecting a pressure loss of the measurement fluid based on the vortex generator based on the pressure of the first and second impulse tubes; , a dividing section that divides the output of the pressure detecting section by the output of the vortex velocity detecting section.