JPH11281432A - Pulsation absorbing structure for flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulsation absorbing structure for a flow meter, which is capable of performing accurate flow rate measuring by reducing the influence of a pulsating flow. SOLUTION: In the pulsation absorbing structure of an estimation type flow meter for estimating an integrated flow rate by using a weighing and measuring section 2 to intermittently measure the flow velocities of fluids flowing-in/ flowing-out through an inlet 3/outlet 4, inside at least one of the inlet 3 and the outlet 4, restriction parts 5 and 6 having inner diameters smaller than the inlet 3/outlet 4 are provided in bent parts 7 and 8 in the midway from the inlet 3/outlet 4 to the measuring duct 22 of the weighing and measuring section 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter for measuring a flow rate used in an electronic gas meter or the like, and more particularly, to an estimating equation for estimating an integrated flow rate by intermittently measuring a flow velocity in a flow path. The present invention relates to a flowmeter pulsation absorbing structure for reducing the influence of flowmeter pulsation (pressure fluctuation, flow velocity fluctuation).

[0002]

2. Description of the Related Art Conventionally, as a flow meter used for measuring a flow rate of an electronic gas meter or the like, a flow meter of an ultrasonic type or a fluidic type has been widely used. For example, the basic principle of an ultrasonic gas flow meter will be briefly described. As shown in FIG. 3, the ultrasonic flow meter 20 uses an ultrasonic frequency arranged at a certain distance in a gas flow path. It has two operative acoustic transducers 21, 23, for example made of piezoelectric transducers, and a measuring duct 22, through which ultrasonic waves propagate.

The ultrasonic flow meter 20 first generates an ultrasonic signal from the acoustic transducer 21 on the gas inflow side, receives the ultrasonic signal from the acoustic transducer 23 on the gas outflow side, and converts the ultrasonic signal between the acoustic transducers into a gas. The propagation time t1 in the flow direction is measured. Next, the ultrasonic flow meter 20 switches between the two acoustic transducers to generate an ultrasonic signal from the acoustic transducer 23 on the gas outflow side and cause the acoustic transducer 21 on the gas inflow side to receive the ultrasonic signal. Measures the propagation time t2 in the reverse direction. Further, the ultrasonic flow meter 20 measures the measurement duct 22 based on the difference between the two measured propagation times t1 and t2.
The flow velocity v of the gas flowing inside is obtained intermittently, and the flow velocity v is multiplied by the cross-sectional area of the measurement duct 22 to obtain the instantaneous flow rate. Then, the flow rate is obtained by multiplying the instantaneous flow rate by a sampling time that is a constant measurement interval, and the integrated flow rate obtained by integrating the flow rates is displayed.

[0004]

In a combustor such as a gas heat pump (GHP) that consumes a fluid such as a gas supplied through a flow meter of this type, during operation, pressure fluctuations or fluctuations in the supplied gas occur. Some may cause pulsations such as flow velocity fluctuations. That is, for example, in the installation example of the flow meter shown in FIG. 4A, the gas pressure fluctuates with the operation of the combustor 30, and the pulsation 25 thereof is generated from the downstream side of the flow meter 20.
Propagate inside. This causes a measurement error.

[0005] In the installation example of the flow meter shown in FIG. 4B, of the two flow meters 20A and 20B connected in parallel, the flow meter 20B has a pulsation 25B from the combustor 30B.
Propagates from the downstream side, and pulsation 25A from combustor 30A propagates from the upstream side. Therefore, the flow meter 2
At 0B, a larger measurement error occurs than in the installation example shown in FIG.

More specifically, referring to FIG. 5, when a pressure fluctuation or the like occurs, the gas flow causes a pulsating flow in which the gas flow rate changes with time due to the fluctuation. The flow velocity v of the gas flow having such a pulsating flow is measured at a constant sampling interval Δt by the flow meter as described above, and the passing flow rate is obtained by multiplying the measured flow velocity v by the sampling time Δt. In this case, the hatched portion in the figure becomes an error. Therefore, the integrated flow rate obtained by integrating the passing flow rates is an integrated value different from the actual gas usage amount.

An object of the present invention is to solve the above-mentioned problems, and to provide a pulsation absorbing structure of a flow meter capable of reducing the influence of a pulsating flow and performing accurate flow measurement.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide an estimating method for estimating an integrated flow rate by intermittently measuring the flow velocity in a fluid flowing in or out through an inlet and an outlet by a measuring unit. In the pulsation absorbing structure of the flow meter, a narrowed portion having an inner diameter smaller than the inflow port or the outflow port is provided inside the at least one of the inflow port and the outflow port from the inflow port or the outflow port. The problem is solved by a pulsation absorbing structure of a flow meter, which is provided at a bent portion on the way to a measurement duct of a measurement / measurement unit.

In the pulsation absorbing structure for a flowmeter according to the present invention, a throttle portion having a smaller inside diameter than the inflow port or the outflow port is provided at a bent portion on the way from the inflow port or the outflow port to the measurement duct of the measuring section. Therefore, the pulsating flow propagating from the inflow port or the outflow port can be attenuated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic gas flow meter to which a pulsation absorbing structure of a flow meter according to an embodiment of the present invention is applied will be described in detail with reference to FIGS. FIG.
FIG. 2 is a schematic sectional view showing an ultrasonic gas flow meter to which a pulsation absorbing structure of a flow meter according to an embodiment of the present invention is applied;
FIG. 2 is an enlarged cross-sectional view near a bent portion of the flow meter shown in FIG. 1.

Referring to FIG. 1 and FIG. 2, an ultrasonic gas flow meter 1 measures the flow rate of gas flowing in or out through an inlet 3 and an outlet 4 in a measuring section 2 provided in the main body. measure.

A substantially cylindrical flow path through which a gas flow flows is formed inside the inflow port 3 and the outflow port 4, and the measuring and measuring section 2 provided at an intermediate position of the flow path allows ultrasonic waves to propagate therethrough. A pair of acoustic transducers 21 that operate at an ultrasonic frequency and that are arranged at positions facing each other at a predetermined interval with the measuring duct 22 interposed therebetween,
23. Each acoustic transducer 2
Reference numerals 1 and 23 are piezoelectric vibrators that operate at an ultrasonic frequency.

The pulsation absorbing structure of the flow meter according to the present embodiment is configured such that the measuring duct 2 of the measuring / measuring unit 2 is connected to the inlet 3 or the outlet 4.
At the bent portions 7 and 8 on the way to 2, throttle portions 5 and 6 having smaller inner diameters than the inlet 3 and the outlet 4 are provided.

That is, as shown in FIG.
1, the inner diameter A2 of the throttle portion 5 formed in the bent portion 7 is smaller. In other words, the cross-sectional area of the throttle portion 5 is formed smaller than the cross-sectional area of the flow channel near the inlet 3. In addition, since the gas flow entering through the inlet 3 is formed at the bent portion 7, the flow velocity of the gas flow is increased by the throttle portion 5, and the gas flow is measured at the outlet of the throttle portion 5 with the flow direction being changed by approximately 90 °. Flow into the duct 22.

The measuring procedure of the weighing / measuring unit 2 is the same as the measuring procedure explained in the prior art. That is, an ultrasonic signal is generated from the acoustic transducer 21 on the gas upstream side, and the ultrasonic signal is caused to pass through the inside of the measurement duct 22 and received by the acoustic transducer 23 on the gas downstream side. At this time, the propagation time t1 of the ultrasonic signal in the gas flow direction between the acoustic transducers 21 and 23 is measured.

Next, the weighing / measuring unit 2 switches the two acoustic transducers 21 and 23 to generate an ultrasonic signal from the acoustic transducer 23 on the downstream side of the gas, and passes the ultrasonic signal through the measuring duct 22. Let
The sound is received by the acoustic transducer 21 on the gas upstream side.
At this time, the propagation time t2 in the direction opposite to the gas flow direction is measured.

Next, the weighing / measuring unit 2 calculates the propagation time t1,
On the basis of the propagation time difference of t2, the flow velocity v of the gas flowing in the measurement duct 22 is intermittently obtained.
The instantaneous flow rate is obtained by multiplying the flow rate v by a constant determined by the cross-sectional area of 2 and the temperature, pressure, and gas quality (density, viscosity). Thereafter, a passing flow rate is obtained by multiplying the instantaneous flow rate by a sampling time that is a fixed measurement interval, and the passing flow rate is integrated to obtain an integrated flow rate.

The operation of the present embodiment will be described by taking the inlet side as an example. In the above-described gas flow meter 1 of the present embodiment,
When the pulsating flow 25 propagates from the inflow port 3 to the gas fluid flowing into the main body, pulsation such as pressure fluctuation and flow velocity fluctuation (hereinafter simply referred to as pulsation) is caused by the presence of the throttle unit 5 that changes the flow velocity of the gas fluid. Is attenuated.

That is, as shown in FIG. 2, at the inflow port 3, the pulsating flow 25
Is propagated, but the gas fluid is compressed by the constricted portion 5 formed in the bent portion 7 and the flow velocity is increased. Then, the direction of the flow passage is changed by approximately 90 ° at the outlet of the restricting portion 5, and is expanded again on the upstream side of the measurement duct 22 and flows into the measurement duct 22. Through the compression, expansion and direction change of the gas fluid, the pulsating flow 25 propagating in the gas fluid can be attenuated to a substantially steady flow 26 which does not affect the measured value.

The gas flow after the measurement is the same as that at the above-described inlet side, and the gas flow after the measurement is compressed by the throttle unit 5 to increase the flow velocity. Then, the direction is changed at the outlet of the restricting section 5 and expanded again before the outlet 4. Therefore, it is possible to attenuate the pulsating flow propagating through the gas fluid downstream of the outlet 4 to make it a substantially steady flow that does not affect the measured value.

As described above, according to the pulsation absorbing structure of the flow meter according to the present embodiment, the throttle portions 5 and 6 having smaller inner diameters than the inlet 3 and the outlet 4 are connected to the measuring duct 22 from the inlet 3 and the outlet 4. Are formed at the bent portions 7 and 8 on the way to the slope, for example, pulsation propagating from the upstream side or the downstream side of the gas flow meter 1 can be attenuated near the throttle portions 5 and 6.
Thereby, the influence of the pulsating flow on the gas flow measurement can be reduced, and accurate flow measurement can be performed.
In manufacturing, the pulsating flow can be reduced with a relatively simple configuration, so that the cost can be reduced.

The present invention is not limited to the above embodiment, but can be implemented in other modes by making appropriate changes. For example, in the above embodiment, since it is particularly suitable for the principle and structure of a guess type gas flow meter including an ultrasonic type and a remarkable effect can be expected, as an example of an embodiment applied to an ultrasonic type gas flow meter Although described above, the present invention is not limited to this, and may be applied to a fluidic flow meter or the like that measures a flow velocity by a vortex.

[0023]

As described above, according to the pulsation absorbing structure of the flow meter of the present invention, at least one of the inlet and the outlet has a smaller inner diameter than the inlet or the outlet. A throttle portion is provided at a bent portion on the way from the inflow port or the outflow port to the measurement duct of the measurement and measurement section. Therefore, when measuring the flow rate of the fluid,
The influence of the pulsating flow can be reduced by the throttle section, the error of the integrated flow rate can be reduced based on accurate flow rate measurement, and an inexpensive and highly reliable flow meter can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a pulsation absorbing structure of a flow meter according to the present invention.

FIG. 2 is an enlarged partial cross-sectional view showing a main part of the flow meter shown in FIG.

FIG. 3 is a schematic view showing a conventional gas flow meter.

FIG. 4 is a block diagram showing a relationship between a conventional flow meter and a combustor.

FIG. 5 is a graph showing a change in flow velocity of a conventional gas flow.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow meter (ultrasonic gas flow meter) 2 Metering / measuring part 3 Inlet 4 Outlet 5 Upstream restrictor 6 Downstream restrictor 7 Upstream bend 8 Downstream bend 21 Upstream transducer 22 Measurement duct 23 Downstream transducer

Claims (1)

[Claims] 1. A pulsation absorbing structure of a guess-type flowmeter for estimating an integrated flow rate by intermittently measuring a flow velocity in a fluid flowing in or out through an inlet and an outlet by a measuring unit, Inside at least one of the outlet and the outlet, a narrowed portion having a smaller inner diameter than the inlet or the outlet is bent on the way from the inlet or the outlet to the measurement duct of the measuring unit. A pulsation absorbing structure for a flow meter, which is provided in a section.