JP3365953B2 - Pulsation absorption structure of flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsation absorbing structure of a flow meter used in an electronic gas meter or the like, and particularly to a speculative flow meter for intermittently measuring a flow velocity in a flow path to estimate an integrated flow rate. The present invention relates to a pulsation absorption structure of a flow meter that can reduce the effect of pulsation (pressure fluctuation, flow speed fluctuation).

[0002]

2. Description of the Related Art Conventionally, as an electronic gas meter,
Ultrasonic and fluidic type flow meters are widely used. As shown in FIG. 3, the ultrasonic flow meter 20 has acoustic transducers 21 and 23 arranged in the gas flow path with a certain distance therebetween, and a propagation conduit 22 through which ultrasonic waves propagate. . The acoustic transducers 21, 23 are piezoelectric vibrators and operate at ultrasonic frequencies.

The ultrasonic flow meter 20 first generates an ultrasonic signal from the acoustic transducer 21 on the gas inflow side and causes the acoustic transducer 23 on the gas outflow side to receive the ultrasonic wave signal, so that the acoustic transducers 21 and 23 are connected to each other. The propagation signal t1 in the gas flow direction at is measured. next,
The acoustic transducers 21 and 23 on both sides are switched to generate an ultrasonic signal from the acoustic transducer 23 on the gas outflow side and the acoustic transducer 21 on the gas inflow side.
By receiving the signal, the propagation signal t2, which goes backward in the gas flow direction, is measured.

The flow velocity v of the gas flowing through the propagation conduit 22 is intermittently calculated based on the difference in propagation time between these propagation signals t1 and t2, and the instantaneous flow rate is calculated by multiplying this flow velocity v by the cross-sectional area of the propagation conduit 22. . Then, the ultrasonic flowmeter 20 is configured to calculate the passing flow rate by multiplying the instantaneous flow rate by a sampling time which is a constant measurement time, and display the integrated flow rate obtained by integrating the passing flow rate.

[0005]

By the way, a GHP that consumes fluid such as gas supplied through a flow meter of this type.
Some combustors such as (gas heat pumps) cause pulsation of pressure fluctuation and flow speed fluctuation in the supply gas during use.
For example, as shown in FIG. 4A, the gas pressure fluctuates due to the use of the combustor 30, and the pulsation 25 thereof propagates from the downstream side of the flow meter 20 into the flow meter and causes a measurement error. In particular, as shown in FIG. 4 (b), two flow meters 20A, 20B
, The pulsation 25B from the combustor 30B propagates from the downstream side to the flow meter 20B as described above, and the pulsation 25A from the combustor 30A propagates from the upstream side. A large measurement error occurs at 20B.

That is, as shown in FIG. 5, when a pressure fluctuation or the like occurs, due to this, a pulsating flow in which the gas flow velocity changes with time is generated in the gas flow. When the flow velocity v of the gas flow in which such a pulsating flow is generated is measured at a constant sampling interval Δt by the flowmeter as described above, and the measured flow velocity v is multiplied by the sampling time Δt to obtain the passing flow rate, The part shaded with a middle line becomes an error, and the integrated flow rate obtained by integrating the passing flow rate is an integrated value different from the actual gas usage.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a pulsation absorbing structure of a flow meter capable of reducing the influence of the pulsating flow and performing accurate flow rate measurement.

[0008]

In order to achieve the above-mentioned object, the present invention provides, as claimed in claim 1, a body for measuring the flow rate of a fluid passing through the body. A pulsation absorbing structure of a flowmeter having an inflow port and an outflow port, and an electronic measuring unit arranged between the inflow port and the outflow port, wherein one of the inflow port and the outflow port Having a nozzle member attached to
The nozzle member has a first cylinder portion whose inner surface is tapered toward the upstream side of the fluid, and an outer surface of the nozzle member from the small-diameter edge portion of the first cylinder portion toward the downstream side of the fluid. It is characterized in that it is provided with a formed second cylindrical portion.

Here, the first cylinder portion and the second cylinder portion may have a cone shape in which the opening cross section of an arbitrary shape is gradually reduced, and a cylindrical shape, a rectangular cylinder shape, or the like can be adopted. Also, the first
As the tubular portion and the second tubular portion, for example, the inner surface and the outer surface may be tapered by changing the wall thickness from one end side toward the multi-end side. The first and second cylindrical portions may have different opening shapes at both ends in the longitudinal direction, and appropriate fins or the like may be provided on the outer wall surface or the inner wall surface.

In the pulsation absorbing structure of the flow meter constructed as described above, since the groove having the tapered cross section is formed along the outer surface of the second tubular portion, for example, the pulsation generated from the combustor is directed to the upstream side. Even if the pulsation propagates, the pulsation is guided to the groove bottom along the outer surface of the second tubular portion and is damped. On the other hand, the fluid flowing from the upstream side to the downstream side is guided by the second tubular portion and normally flows. Therefore, in such a pulsation absorbing structure of the flowmeter, the pulsation propagating from the downstream side to the upstream side is effectively buffered, so that the influence of the pulsation can be reduced as compared with the conventional one. By the above, the above-mentioned object is achieved.

Further, in the present invention, as described in claim 2, when the slit is formed in the second cylindrical portion, the fluid pressure and the flow rate of the fluid flowing from the upstream side to the downstream side are temporarily changed. Even if the pulsation increases, the small-diameter edge portion of the second tubular portion does not expand and obstruct the flow, and even if a large pulsation propagates from the downstream side to the upstream side, the second surface pressed against the outer surface The tubular portion reduces the diameter of the small-diameter edge portion so that pulsation is not propagated upstream of the nozzle member.

Further, according to the present invention, as described in claim 3, if the nozzle member has elasticity, the small-diameter edge portion of the second tubular portion is appropriately expanded or reduced in diameter to achieve a desired size. The effect of can be made more remarkable.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment according to the present invention and a sectional view and a perspective view showing a nozzle member, and FIG. 2 is a perspective view and a sectional view showing a modified example of the nozzle member. In addition, in the embodiments described below, the members already described in FIGS. 3 to 5 are denoted by the same or corresponding reference numerals in the drawings to simplify or omit the description.

As shown in FIG. 1 (a), a flow meter 10 according to an embodiment of the present invention has an inlet 12 provided in a main body 11.
And an outlet 13 and an electronic measuring unit 14 arranged between the inlet 12 and the outlet 13. In the measurement unit 14, acoustic transducers 21 and 23 are arranged at both ends of the propagation conduit 22. In this flowmeter 10, nozzle members 15 and 15 are attached to an inlet 12 and an outlet 13, respectively.

As shown in FIGS. 1 (b) and 1 (c), the nozzle member 15 has a first tubular portion 16 and a second tubular portion 17. The first tubular portion 16 is formed into a cylindrical shape having a uniform thickness dimension, and the diameter of one end side 16A (upper end in the figure) of the first tubular portion 16 is the other end side.
The tapered shape is larger than the diameter of 16B (lower end in the figure). The outer surface 16C of the first tubular portion 16 can be brought into close contact with the inflow port 12 and the outflow port 13. Meanwhile, the second
The cylindrical portion 17 is connected to the first cylindrical portion 16 and has a cylindrical shape having a uniform wall thickness. Also has a large tapered shape.

In the nozzle member 15 as described above, the first tubular portion 16 and the second tubular portion 17 are integrally formed of a suitable rubber having gas corrosion resistance and flexibility. Then, these nozzle members 15 are
The tip of the tubular portion 17 is arranged so as to face the inside of the main body 11, and the tip of the second tubular portion 17 is arranged so as to face away from the main body 11 at the outflow port 13.

According to the flow meter 10 as described above, for example, even if the pulsation generated from the combustor propagates toward the main body 11,
Since the nozzle member 15 is arranged at the outflow port 13, the pulsation 25 is guided and buffered between the inner side surface of the first cylindrical portion 16 and the outer side surface of the second cylindrical portion 17, and propagates into the main body 11. The pulsation 25 can be reduced. On the other hand, the normally flowing gas is guided to the second tubular portion 17 because the second tubular portion 17 of the nozzle member 15 arranged at the inlet 12 and the outlet 13 tapers toward the downstream side. .

Further, even if pulsation occurs inside the main body 11, since the nozzle member 15 is arranged at the inflow port 12, the inner surface of the first tubular portion 16 and the outer surface of the second tubular portion 17 are separated from each other. The pulsation is guided and buffered in the meantime, and there is little risk that the pulsation propagates from the main body 11 toward the upstream side. In particular, since the above-mentioned nozzle member 15 has elasticity, the small-diameter edge portion of the second tubular portion 17 is appropriately expanded or reduced in diameter, whereby the desired effect becomes more remarkable.

The present invention is not limited to the above-described embodiments, but can be appropriately modified and improved.
The nozzle member 18 shown in FIG. 2 may be adopted. The nozzle member 18 is basically configured in the same manner as the nozzle member 15 described above, but a plurality of slits 19 are radially formed from the tip of the second tubular portion 17 along the generatrix.

Since the nozzle member 18 is formed with a plurality of slits 19 radially from the tip of the second tubular portion 17,
Even if the fluid pressure and the flow rate of the fluid flowing from the upstream side to the downstream side temporarily increase, the second cylindrical portion 17 does not expand the diameter and obstruct the flow, and a large pulsation from the downstream side to the upstream side. Even when the pulse is transmitted, the second cylinder portion 17 whose outer surface is pressed does not reduce its diameter to propagate the pulsation to the upstream side. According to such a nozzle member 18, a desired effect can be more surely and conspicuously made, whereby the measurement accuracy can be improved.

Further, in the above-mentioned embodiment, the ultrasonic type electronic gas meter is exemplified as the flow meter, but the present invention is also applicable to the fluidic type electronic gas meter, and the fluid is limited to gas. do not do. In addition, the main body, the inlet, and the like illustrated in the above-described embodiment
The material, shape, size, form, number, arrangement position, etc. of the outlet, the measuring part, the nozzle member, the first cylinder part, the second cylinder part, the slit, etc. are arbitrary as long as the present invention can be achieved, and are limited. Not done.

[0022]

As described above, according to the present invention, as described in claim 1, for example, the pulsation generated from the combustor is guided to the outer surface of the second tubular portion and is buffered.
The influence of pulsation can be reduced as compared with the conventional case. Further, according to the present invention, as described in claim 2, even if the fluid pressure and the flow rate of the fluid flowing from the upstream side to the downstream side temporarily increase, the flow of the fluid is not hindered, and the downstream side Even if a large pulsation propagates from the upstream side of the
The tubular portion does not reduce the small-diameter edge portion to propagate pulsation to the upstream side. Further, according to the present invention, as described in claim 3, since the nozzle member has elasticity, the desired effect can be obtained by appropriately expanding or contracting the small-diameter edge portion of the second tubular portion. Can be made more remarkable.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment according to the present invention, and a sectional view and a perspective view showing a nozzle member.

FIG. 2 is a perspective view and a cross-sectional view showing a modified example of a nozzle member.

FIG. 3 is a schematic diagram showing the concept of an electronic gas meter.

FIG. 4 is a schematic diagram showing a conventional problem.

FIG. 5 is a graph showing a measurement error.

[Explanation of symbols]

10 flow meter 11 body 12 Inlet 13 Outlet 14 Measuring section 15, 18 nozzle member 16 First cylinder 17 Second cylinder 19 slits

Claims (3)

(57) [Claims] 1. An electronic measuring unit arranged between an inflow port and an outflow port provided in the main body and an inflow port and the outflow port for measuring a flow rate of a fluid passing through a hollow main body. A pulsation absorbing structure of a flow meter having, having a nozzle member attached to one of the inflow port and the outflow port, wherein the nozzle member has an inner surface facing the upstream side of the fluid. It is characterized by comprising a first cylindrical portion formed in a taper shape, and a second cylindrical portion whose outer surface is formed in a taper shape from a small-diameter edge portion of the first cylindrical portion toward the downstream side of the fluid. Pulsation absorption structure of the flow meter. 2. The pulsation absorbing structure for a flow meter according to claim 1, wherein a slit is formed in the second tubular portion. 3. The pulsation absorbing structure for a flow meter according to claim 1, wherein the nozzle member has elasticity.