JP3179720U - Flow measuring device - Google Patents

Abstract

Provided is a flow rate measuring device capable of simplifying pressure and flow rate measurement of various gases.
A flow measuring device according to the present invention has a conduction path having a static pressure measurement hole for measuring a static pressure of the fluid on a wall surface as the fluid flows, and a downstream area from the static pressure measurement hole of the conduction path. A wake pressure detection tube having a wake pressure hole for measuring the wake pressure of the fluid at a position opposite to the direction facing the fluid flow, and a static pressure measurement hole and a wake pressure detection tube. A flow rate measuring unit that measures and outputs the flow rate value of the fluid based on the reference data for each type of fluid.
[Selection] Figure 1

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of a fluid by a simple method.

  Many types of flow meters such as a differential pressure type, an ultrasonic type, a vortex type, and a float type have been put into practical use and used for fluid flow rate measurement.

  The fluid flow is divided into a laminar flow region where the Reynolds number is 2500 or less and a turbulent region where vortices are generated when the Reynolds number is 10,000 or more. In the vicinity of the boundary where the laminar flow and the turbulent flow change, there is a transition region where the fluid flow becomes unstable. For this reason, when using a differential pressure type flow meter, it is important to perform measurement while avoiding this region.

  By the way, multiple types of gas are used in medical institutions and the like. For example, oxygen gas, nitrous oxide gas (laughing gas), carbon dioxide gas, nitrogen gas and air, or air for suction are used as medical gas in the hospital. These gases are supplied from a supply facility to each hospital room, ICU, operating room, and the like by a medical gas piping facility. At the end of the medical gas pipe, the gas supply is maintained and managed by periodically checking the pressure and flow rate of each gas at the point of use.

  However, the pressure and flow rate of each medical gas is measured by an inspection flow meter for each application (by type), and the burden of loading a large amount of equipment and preparing multiple types of flow meters is significant. It was.

  The present invention has been made in view of such problems, and an object thereof is to provide a flow rate measuring device (flow meter) capable of simplifying the pressure and flow rate measurement of various gases.

  The flow measuring device of the present invention has a flow path through which a fluid flows and a static pressure measurement hole for measuring the static pressure of the fluid in a wall surface, and a downstream area from the static pressure measurement hole of the conduction path, A wake pressure detection tube having a wake pressure hole for measuring the wake pressure of the fluid at a position opposite to the direction facing the fluid flow, and a pressure measured by the static pressure measurement hole and the wake pressure detection tube And a flow rate measuring unit that measures and outputs the flow rate value of the fluid based on the reference data for each type of fluid.

  In the flow measurement device of the present invention, the static pressure measurement hole is formed in the side wall of the conduction path through which the fluid flows, and the wake pressure detection tube passing through the conduction path downstream from the static pressure measurement hole is directed to the fluid flow. A reverse pressure hole for measuring the wake pressure of the fluid is provided at a position opposite to that of the fluid, and by measuring the static pressure and the wake pressure at the static pressure measurement hole and the wake pressure hole, the differential pressure can be accurately determined. It becomes possible to measure. Further, the flow rate measurement unit measures the flow rate using the reference data corresponding to the measurement fluid, thereby measuring the flow rates of a plurality of types of fluids.

  According to the flow measuring device of the present invention, a differential pressure is measured by providing a static pressure measurement hole on the side wall of the conduction path upstream from the penetration position of the wake pressure detection pipe that measures the wake pressure of the fluid flowing through the conduction path. The flow rate value is calculated from the differential pressure and the reference data corresponding to the measurement fluid. This makes it possible to easily measure the flow rates of a plurality of types of fluids with a single flow rate measuring device.

It is the schematic of the flow measuring device concerning one embodiment of the present invention. It is sectional drawing explaining the aperture ratio of the conduction path shown in FIG. It is a characteristic view showing the relationship between differential pressure | voltage and flow volume. It is a block diagram of the flow measuring device shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a flow rate measuring device (flow rate measuring device 1) according to an embodiment of the present invention. FIG. 2 shows a cross-sectional configuration of the conduction path 10 taken along the II broken line shown in FIG. This diversion measuring device 1 is provided with a throttle mechanism in a pipe (here, the conduction path 10), and a differential pressure type that measures the flow rate of fluid flowing through the pipe using a differential pressure (ΔP) before and after the throttle mechanism. It is a flow meter. The flow rate measuring device 1 includes a conduction path 10 through which a fluid flows, a wake pressure detection pipe 20 penetrating the conduction path 10, which corresponds to the above-described throttle mechanism, and a flow rate measurement unit 30. In the present embodiment, the static pressure measurement hole 11 provided in the side wall in the upstream region from the wake pressure detection pipe 20 penetrating the conduction path 10 and the wake pressure hole 21 provided in the wake pressure detection pipe 20. Then, the differential pressure (ΔP) of the fluid is measured, and the flow rate of the fluid flowing in the conduction path 10 is calculated by the flow rate measuring unit 30.

The conduction path 10 is a flow path through which a measurement fluid flows during flow rate measurement. The conducting path 10 has, for example, a cylindrical shape and is made of, for example, metals such as aluminum and brass, or resins. As described above, the static pressure measurement hole 11 is provided on the side wall of the conduction path 10. The static pressure measurement hole 11 is connected to a pressure sensor 31 (see FIG. 4) provided in a flow rate measurement unit 30 described later, and the static pressure (P ₁ ) of the fluid flowing in the conduction path 10 is measured. The shape of the static pressure measurement hole 11 is not particularly limited. The size of the static pressure measurement hole 11 may be any size as long as the static pressure in the conduction path 10 can be accurately measured. For example, when the inner diameter of the conduction path 10 is 10φ, the hole diameter is 2 to 5φ. That's fine.

The wake pressure detection pipe 20 is provided on the side wall of the conduction path 10 so as to pass through the central portion (C ₁ ) of the conduction path 10 in a downstream area from the static pressure measurement hole 11 provided in the conduction path 10. The fitting hole 12 is inserted vertically from the outside to the inside of the side wall. The distance between the static pressure measurement hole 11 and the wake pressure detection tube 20, that is, the distance between the static pressure measurement hole 11 and the fitting hole 12 may be a constant distance in order to accurately measure the static pressure measurement value. Preferably, the distance should just be 0.5-2 mm, for example.

The wake pressure detection tube 20 is made of, for example, a metal such as aluminum or brass, or a resin. The outer shape has a cylindrical shape, and the inside has a cylindrical cavity. The outer diameter of the wake pressure detection tube 20 is preferably 2 to 6φ, for example, when the inner diameter of the conduction path 10 is 10φ. The wake pressure detection tube 20 penetrating the conduction path 10 closes the fluid flow path, and the fluid flow portion in the cross section of the conduction path 10 is blocked by the wake pressure detection pipe 20 as shown in FIG. Can be done on both sides of the stripped part. In the cross section of the conduction path 10, the differential pressure increases when the area blocked by the wake pressure detection tube 20 is large, that is, when the fluid cross-sectional area (S _l ) is narrowed.

In the present embodiment, a wake pressure hole 21 communicating with the internal cavity is provided at the center (C ₂ ) of the cylindrical portion exposed in the conduction path 10 of the wake pressure detection tube 20. The wake pressure hole 21 is formed in the direction opposite to the direction facing the fluid flow. The wake pressure hole 21 is connected to a pressure sensor 31 provided in a flow rate measuring unit 30 (described later) through the inside of the wake pressure detection tube 20, and is connected to the inside of the conduction path 10. The wake pressure (P ₂ ) of the flowing fluid is measured.

Incidentally, the pressure value of the pressure flow in the conductive path 10 when measuring the reverse direction of the fluid, which is measured in the downstream pressure hole 21 (P ₂₎ is measured in the static pressure measurement hole 11 (P ₁ ). In this case, measurement is possible by using a sensor capable of measuring both positive and negative (+ and-) values as the pressure sensor 31 described later.

  The flow rate measurement unit 30 includes, for example, a pressure sensor 31, a memory unit 32, a designation unit 33, and a flow rate value calculation circuit 34.

The pressure sensor 31 outputs a voltage or an electrical signal corresponding to the static pressure (P ₁ ) transmitted from the static pressure measurement hole 11 and the wake pressure (P ₂ ) transmitted from the wake pressure hole 21. FIG. 3 is a characteristic diagram showing the relationship between the differential pressure output from the pressure sensor 31 and the flow rate value (true value Q ₀ ). From FIG. 3, the differential pressure output changes in a quadratic function corresponding to the flow rate value (Q ₀ ). As described above, the differential pressure output and the flow rate have a clear one-to-one correspondence relationship.

The memory unit 32 stores density (ρ ₀ ) or molecular weight values of various fluids in the standard state. The density (ρ ₀ ) of the fluid at rest is used as reference data when calculating a flow value in the flow value calculation circuit 33 described below. In the present embodiment, the static density (ρ ₀ ) (see Table 1) of the fluid to be measured (for example, oxygen, nitrous oxide, etc.) (see Table 1) is input to the memory unit 32 in advance, and the designation unit 33 is used during differential pressure measurement. It is possible to measure a plurality of types of fluids by reading the fluid reference data instructed by.

The flow rate value calculation circuit 34 calculates a flow rate measurement value (Q) based on the following formula (1) based on the differential pressure (ΔP). However, in reality, the density of the fluid when passing through the conduction path 10 is different from the density (ρ ₀ ) when stationary. The following formula (2) is obtained by correcting the fluid density (ρ _m ) when passing through the conduction path 10, and the flow rate measurement value (Q) is calculated using this formula. Specifically, the value (absolute value) of the differential pressure (ΔP) (= P ₂ −P ₁ ) between the static pressure (P ₁ ) and the wake pressure (P ₂ ) obtained based on the output from the pressure sensor 31. 2) (2ΔP) divided by the density (ρ) of the fluid to be measured (2ΔP / ρ) is calculated as a square root √ (2ΔP / ρ). Next, the value of the substantial opening area (S _D −S _d ) obtained by subtracting the cross sectional area (S _d ) blocked by the wake pressure detection pipe 20 from the total cross sectional area (S _D ) as the flow path of the conduction path 10 is obtained. By dividing by the total cross-sectional area S _D , the substantial aperture ratio Kp of the conduction path 10 is multiplied. Subsequently, the fluid density value (ρ ₀ ) at rest is multiplied by the ratio (P ₀ / P _m ) with the static pressure (P ₀ ) of the designed fluid (P ₀ ) and the measured line pressure (P _m ). Thus, the fluid density value (ρ) is corrected. The corrected density value ρ _m is used for the calculation for calculating the flow rate measurement value (Q). Kp is a flow coefficient.

(Equation 1) Q = (1 / Kp) · √ {(P ₀ / P ₁ ) · ΔP / ρ ₀ }) (1)

(Equation 2) Q = Kp · √ {2 (P ₀ / P _m ) · ΔP / ρ ₀ }) (2)

Thus, in the flow rate measuring device according to the present embodiment, the static pressure (P ₁ ) measured in the static pressure measurement hole 11 and the wake pressure (P ₂ ) measured in the wake pressure hole 21. The flow rate value of the fluid is calculated using the differential pressure (ΔP). Specifically, as shown in FIG. 4, the static pressure (P ₁ ) and the wake pressure (P ₂ ) measured in the static pressure measurement hole 11 and the wake pressure hole 21 are transmitted to the pressure sensor 31. The The pressure sensor 31 calculates a differential pressure (ΔP) and outputs an output based on the differential pressure (ΔP) to the flow rate value calculation circuit 34. On the other hand, fluid reference data (fluid density (ρ ₀ ) at rest) instructed by the designation unit 33 is output from the memory unit 32 to the flow rate value calculation circuit 34. The flow rate value calculation circuit 34 calculates the flow velocity value of the fluid flowing through the conduction path 10 based on the differential pressure (ΔP) and the reference data, and outputs the calculation result to a display unit (not shown).

As described above, in the present embodiment, the differential pressure (ΔP) of the fluid flowing through the conduction path 10 is measured with the static pressure (P ₁ ) measured in the static pressure measurement hole 11 provided in the side wall of the conduction path 10 and the static pressure. The wake pressure (P) measured at the wake pressure hole 21 provided at a position opposite to the direction facing the fluid flow of the wake pressure detection pipe 20 penetrating the downstream area from the pressure measurement hole 11. ₂ ) and calculated from. Thereby, the differential pressure (ΔP) of the fluid can be accurately measured. Further, reference data (density (ρ ₀ ) at rest) of various fluids is stored in the memory unit 32 in the flow rate measuring unit 30, and the corresponding reference data is output to the flow rate value calculation circuit 34 by designating the measurement fluid. I tried to do it. Accordingly, it is possible to accurately and easily measure the flow rates of a plurality of types of fluids with a single flow rate measuring device.

  In addition, there is no need to prepare a flow measurement device for each measurement fluid (for example, medical gas; oxygen gas, nitrous oxide gas (laughing gas), carbon dioxide gas, nitrogen gas, air, etc.). The carry-in amount is reduced, and the work time can be shortened.

  Further, by using a sensor (± differential pressure sensor) capable of measuring both positive and negative (+ and-) values as the pressure sensor 31 as described above, it is possible to measure the flow rate of the fluid flowing in the opposite direction. . Specifically, the flow rate of suction air flowing in the direction opposite to the medical gas can also be measured.

  Furthermore, in the present embodiment, the description has been made on the premise that the fluid flowing through the conduction path 10 is a single fluid, but various gases are mixed by calculating the gas density of the mixed fluid to be measured and inputting it to the memory unit 32. The flow rate of the mixed fluid can also be measured. This eliminates the need for actual gas calibration, which has been performed with a conventional mass flow meter, thereby reducing the inspection time and cost.

  Although the present invention has been described with reference to the above embodiment, the present invention is not limited to this, and various modifications can be made.

  DESCRIPTION OF SYMBOLS 1 ... Flow measuring device, 10 ... Conduction path, 11 ... Static pressure measurement hole, 12 ... Fitting hole, 20 ... Backflow pressure detection pipe, 21 ... Backflow pressure hole, 30 ... Flow measurement part, 31 ... Pressure sensor, 32 ... Memory unit, 33 ... Designation unit, 34 ... Flow rate value calculation circuit

Claims (5)

As the fluid flows, a conduction path having a static pressure measurement hole for measuring the static pressure of the fluid on the wall surface;
A wake having a wake pressure hole that measures the wake pressure of the fluid at a position opposite to the direction facing the fluid flow while passing through the downstream area of the conduction path from the static pressure measurement hole. A pressure detection tube;
A flow rate measuring device comprising: a flow rate measuring unit that measures and outputs a flow rate value of the fluid based on reference data for each type of fluid, the pressure measured by the static pressure measurement hole and the wake pressure detection tube.   The flow rate measurement unit includes a pressure sensor that detects a differential pressure between the static pressure and the wake pressure, a memory unit in which the reference data is stored, an output from the pressure sensor, and the reference data. The flow rate measuring device according to claim 1, further comprising a flow rate value calculation circuit that calculates a flow rate value.   The flow rate measurement device according to claim 1, wherein the flow rate measurement unit includes a support unit that specifies a type of the fluid.   The flow rate measuring device according to claim 1, wherein a flow rate of medical gas is measured as the fluid.   The flow rate measuring device according to claim 1, wherein the fluid is oxygen gas, air, nitrous oxide gas, carbon dioxide gas, nitrogen gas, and suction air.