JP6134899B2 - Flow measurement unit - Google Patents

Description

  The present invention relates to ultrasonic flow measurement for measuring a flow rate of gas or the like.

  A conventional ultrasonic flow rate measurement unit 12 as shown in FIG. 8 has an opening 13 into which a fluid flows, a measurement channel 14 in which a cross section of the channel through which the fluid flows is formed in a rectangular shape, and a measurement channel A pair of ultrasonic transmission sensors 15a and 15b arranged at a predetermined distance in the fluid flow direction, and an ultrasonic signal transmitted from one of the pair of ultrasonic transmission sensors 15a and 15b face the ultrasonic sensor. It is composed of a flow rate calculation unit 16 that measures the flow velocity of the fluid from the propagation time until it is reflected by the wall surface in the measurement flow path 14 and received by the other, and calculates the flow rate based on this flow velocity (for example, , See Patent Document 1).

JP 2011-112377 A

  However, in the conventional configuration, since the fluid flow flows directly into the measurement flow path, if the fluid flowing into the flow rate measurement unit is largely disturbed, the flow tends to be disturbed up to the ultrasonic propagation path. It affected the measurement of propagation time, and had a negative effect on measurement accuracy.

  In order to solve the above-described conventional problems, the flow rate measurement unit of the present invention has a chamber portion provided on the upstream side of the measurement flow channel and an opening on the side surface of the chamber portion in order to allow fluid to flow into the measurement flow channel. It is a configuration.

  As a result, the fluid flowing through the flow rate measurement unit is once rectified through the chamber and enters the measurement flow path, so that stable measurement of the flow can be performed.

  The flow rate measurement unit of the present invention has a flow rectification effect by passing through the chamber portion when fluid flows into the measurement flow path even if there is a turbulence in the flow flowing into the measurement flow path, and the ultrasonic wave It is possible to stabilize the flow in the propagation path, enable stable measurement with little variation in measurement accuracy, and accurately measure the flow velocity.

1 is an external perspective view of a flow rate measurement unit according to Embodiment 1 of the present invention. Sectional drawing of the flow measurement unit in Embodiment 1 of this invention Configuration diagram of a gas meter using a flow rate measurement unit according to Embodiment 1 of the present invention Operation explanatory diagram of ultrasonic flow measurement in Embodiment 1 of the present invention Flow diagram of conventional fluid analysis results Flow diagram of fluid analysis results in Embodiment 1 of the present invention Sectional drawing of the flow measurement unit in Embodiment 2 of this invention Configuration diagram of ultrasonic flowmeter using conventional flow measurement unit

According to a first aspect of the present invention, a measurement channel and a pair of ultrasonic waves arranged on the same wall surface side of the measurement channel and arranged to constitute an ultrasonic propagation path using reflection on the measurement channel wall surface on the opposite side A sound wave sensor, a calculation means for detecting a flow rate based on a propagation time of ultrasonic waves by transmission / reception of the ultrasonic sensor, and an opening provided on the upstream side of the measurement flow path to allow fluid to flow into the measurement flow path A chamber portion having a portion, wherein the chamber portion is configured to be detachable from the measurement channel, and the opening is provided on a side surface of the chamber portion in a direction perpendicular to the flow direction of the measurement channel. As a result, even if turbulence exists in the fluid flow to be measured, the flow is rectified by flowing into the measurement flow path through the chamber, and the flow in the ultrasonic propagation path is stabilized and measured. Small variation in accuracy It can allow stomach stable measurement.

According to a second aspect of the present invention, a measurement channel and a pair of ultrasonic waves disposed on the same wall surface side of the measurement channel and arranged to constitute an ultrasonic propagation path using reflection on the measurement channel wall surface on the opposite side A sound wave sensor, a flow rate calculation means for detecting a flow rate based on a propagation time of ultrasonic waves transmitted and received by the ultrasonic sensor, and an upstream side of the measurement flow path for flowing a fluid into the measurement flow path A chamber portion having an opening, and the chamber portion is configured to be larger than an outer shape of the measurement flow path, and the flow direction of the fluid flowing in the opening is defined as a flow direction of the fluid in the measurement flow path. It is provided outside the measurement channel outer shape so as to be parallel and in the opposite direction and in the direction opposite to the opening direction of the measurement channel . Stabilizes the flow and minimizes variations in measurement accuracy Can stable measurement, it is possible to measure accurately the flow rate.

According to a third aspect of the invention, in particular , in the second aspect of the invention, the chamber portion is configured to be detachable from the measurement flow path, so that in a meter configuration that does not require rectification, the unit can be simplified and piping can be provided. It can also be used by connecting directly to the measurement channel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a perspective view of a flow rate measurement unit according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the flow rate measurement unit shown in FIG.

  1 and 2, a flow rate measurement unit 1 includes a measurement channel 2, a chamber portion 3 provided on the upstream side of the measurement channel, and an opening 4 through which a fluid to be measured provided in the chamber portion 3 flows. Have Further, the sensor mounting portion 5 adjacent to the measurement flow path 2 is provided, and a pair of ultrasonic sensors 6a and 6b is mounted on the sensor mounting portion 5, and a flow rate calculation circuit for calculating a flow rate from the signal of the ultrasonic sensor above the sensor mounting portion 5. 7 (flow rate calculation means) is installed.

  The flow rate calculation circuit 7 may be configured not to be provided integrally with the flow rate measurement unit 1.

Next, the configuration of the gas meter using the flow rate measurement unit 1 will be described with reference to FIG.

  The fluid supply path 8 includes a shut-off valve 9 that is opened and closed by a valve body that is linked to a drive unit that is an electromagnetic device such as a stepping motor. When the valve (not shown) of the shutoff valve 9 is open, gas (fluid) flows out from the fluid supply path 8 into the meter housing 10. The measurement flow path 2 is configured in a rectangular shape in which the cross section of the flow path through which the fluid flows is rectangular, and the fluid filled in the meter housing 10 flows into the measurement flow path 2 and is connected to the downstream side thereof. It flows out of the meter housing 10 through the fluid outflow path 11 formed.

  The shut-off valve 9 is closed when there is an abnormality in the fluid flow rate calculated by the flow rate calculation circuit 7 or when an earthquake occurrence is detected by a seismic device (not shown).

  Next, the flow measurement operation using ultrasonic waves will be described with reference to FIG. As shown in FIGS. 1-3, in this invention, in order to unitize a pair of ultrasonic sensor, it is set as the structure which arrange | positions an ultrasonic sensor on the same surface of the rectangular cross section of a measurement flow path, The propagation path of transmission / reception of an ultrasonic wave Is a propagation path of a V-shaped ultrasonic wave reflected by the opposite surface, and ultrasonic waves are transmitted and received between ultrasonic sensors arranged upstream and downstream.

  First, the propagation time T1 until the ultrasonic wave emitted from the upstream ultrasonic sensor 6a is received by the downstream ultrasonic sensor 6b is measured. On the other hand, the propagation time T2 until the ultrasonic wave emitted from the downstream ultrasonic sensor 6b is received by the upstream ultrasonic sensor 6a is measured.

  Based on the propagation times T1 and T2 measured in this way, the flow rate calculation circuit 7 calculates the flow rate by the following calculation formula.

  If the angle between the flow velocity V of the fluid to be measured in the flow direction of the measurement channel and the ultrasonic propagation path is θ, the distance between the ultrasonic sensors is 2 × L, and the sound velocity of the fluid to be measured is C, the flow velocity V is calculated by the following equation.

Formula (1) T1 = 2 × L / (C + V cos θ)
Formula (2) T2 = 2 × L / (C−V cos θ)
The speed of sound C is eliminated from the equation for subtracting the reciprocal of T2 from the reciprocal of T1. Equation (3) V = (2 × L / 2 cos θ) ((1 / T1) − (1 / T2))
Since θ and L are known, the flow velocity V can be calculated from the values of T1 and T2. Assuming that the air flow rate is measured, assuming that the angle θ = 45 degrees, the distance L = 35 mm, the sound velocity C = 340 m / s, and the flow velocity V = 8 m / s, T1 = 2.0 × 10 ⁻⁴ seconds, T2 = 2.1 × 10 ⁻⁴ seconds, and instantaneous measurement is possible. Thereafter, the flow rate can be obtained by multiplying the obtained flow velocity and the flow path cross-sectional area.

  In the above-described conventional configuration, since the fluid is once filled in the meter housing 10 and then flows into the measurement flow path 2, it is compared with a system in which the fluid is directly connected to the measurement flow path by piping. Depending on the configuration in the meter housing 10, there is a possibility that a drift occurs in the flow flowing into the measurement flow path, and the flow in the measurement flow path is also affected, which may cause measurement errors.

  In this invention, as shown in FIGS. 1-3, the rectification | straightening structure which consists of the chamber part 3 is provided in the fluid inflow side of the measurement flow path 2. As shown in FIG.

Since the opening 4 is provided on the side of the chamber 3 in the direction perpendicular to the flow direction of the measurement flow path 2, the fluid flowing into the measurement flow path 2 is disturbed or drifted in the flow immediately before the flow rate measurement unit 1. Even if it occurs, it does not flow directly into the measurement channel 2, and the turbulence and drift are suppressed by the passage resistance in the chamber 3, and the flow flows into the measurement channel 2 as a uniform flow. In addition, since the flow in the ultrasonic wave propagation path is stabilized, the measurement reception waveform is stabilized, the measurement accuracy is improved, and the measurement logic can be simplified.

  Further, the outer shape of the chamber portion 3 is larger than the outer shape of the measurement channel 2, and the opening 4 of the chamber unit 3 is provided on a surface adjacent to the measurement channel 2, and is larger than the outer shape of the measurement channel 2. By doing so, it is possible to obtain a rectifying effect by securing the channel length to the measurement channel 2.

  FIG. 5 and FIG. 6 show the results of fluid analysis of the flow in the conventional meter shown in FIG. 8 and the meter casing of the present invention shown in FIG.

  In FIG. 5, the turbulent flow in the meter casing flows into the measurement flow path 14 as it is, but in the present invention, the flow in the meter casing bypasses the chamber portion 3 and is measured as shown in FIG. It flows uniformly into the flow path 2.

  In the present invention, the shape of the opening 4 in the chamber 3 has a dimension equal to or smaller than the short side of the rectangular cross section of the measurement channel. The length may be any length different from the short side.

  Moreover, in FIGS. 1-3 which show this invention, although the shape of the chamber part 3 has comprised the rectangular shape, this may be circular arc shape.

(Embodiment 2)
FIG. 7 shows a cross section of the flow rate measurement unit 1 ′ according to the second embodiment of the present invention, so that the opening 4 ′ of the chamber 3 ′ flows in the direction opposite to the flow in the measurement flow path 2 ′. By providing in, the flow is greatly diverted, the rectification action is increased, and the rectification effect in the chamber portion can be further improved.

  Further, in the above-described embodiment, the chamber portions 3 and 3 ′ may not be integrated with the measurement flow paths 2 and 2 ′ but may be removable.

  As described above, the flow rate measurement unit according to the present invention has a rectifying effect on the flow rate measurement unit itself regardless of the flow in the meter housing, so that the measurement performance can be secured only by the flow rate measurement unit. As the degree of freedom in housing design increases, it is possible to accurately measure the flow velocity in any use state, and it is possible to reduce the size and cost, so that it can be applied to various flow meters including gas meters.

DESCRIPTION OF SYMBOLS 1, 1 'Flow measurement unit 2, 2' Measurement flow path 3, 3 'Chamber part 4, 4' Opening part 6a, 6b Ultrasonic sensor 7 Flow rate calculation circuit (flow rate calculation means)

Claims (3)

A measurement channel;
A pair of ultrasonic sensors installed on the same wall surface side of the measurement channel and arranged to constitute an ultrasonic propagation path utilizing reflection on the measurement channel wall surface on the opposite side;
A flow rate calculating means for detecting a flow rate based on a propagation time of ultrasonic waves by transmission and reception of the ultrasonic sensor;
A chamber portion provided on the upstream side of the measurement flow path, and having an opening for flowing fluid into the measurement flow path,
The chamber part is configured to be removable from the measurement channel,
The opening is a flow rate measurement unit provided on a side surface of the chamber portion in a direction perpendicular to the flow direction of the measurement channel. A measurement channel;
A pair of ultrasonic sensors installed on the same wall surface side of the measurement channel and arranged to constitute an ultrasonic propagation path utilizing reflection on the measurement channel wall surface on the opposite side;
A flow rate calculating means for detecting a flow rate based on a propagation time of ultrasonic waves by transmission and reception of the ultrasonic sensor;
A chamber portion provided on the upstream side of the measurement flow path, and having an opening for flowing fluid into the measurement flow path,
The chamber portion is configured to be larger than the outer shape of the measurement channel,
The opening portion is outside the measurement channel outer shape so that the flow direction of the flowing fluid is parallel and opposite to the fluid flow direction of the measurement channel, and the opening direction of the measurement channel Flow rate measurement unit installed in the opposite direction. Flow rate measurement unit of the chamber part is described請Motomeko 2 is a detachable structure from the measurement flow path.