KR20130058355A - Conical orifice differential pressure type flow measuring apparatus - Google Patents

Abstract

PURPOSE: A conical orifice type differential pressure flow meter is provided to prevent damage to an inner wall of a pipe caused by fluid and to prevent noise and vibration by offsetting cavitation. CONSTITUTION: A conical orifice type differential pressure flow meter comprises a conical part(12). The conical part is formed in the central portion of an orifice plate(11). A plurality of holes is formed in the conical part. A plurality of holes(130) which size is smaller than that of the holes is arranged in the conical part at multiple stages. The holes are formed in a portion where the holes are symmetrical to each other around a center line of the conical part.

Description

CONICAL ORIFICE DIFFERENTIAL PRESSURE TYPE FLOW MEASURING APPARATUS}

The present invention relates to a conical orifice type differential pressure flow meter, and more specifically, to reduce the size and increase the number of holes formed in the conical portion, and to arrange the holes in multiple stages and to form the holes symmetrically. Conical orifice type differential pressure flow measurement device that can reduce vibration and noise by inducing the fluid passing through the hole to proceed along the center line of the conical and offsetting the cavitation without damaging the inner wall surface of the pipe (meta body). It is about.

In general, as a flow meter for measuring the flow rate of fluid (liquid, gas, steam, waste water, sewage, etc.) flowing in a circular pipe, a differential pressure flow meter, an electromagnetic flow meter, an ultrasonic flow meter, a volume flow meter, a vortex flow meter, a turbine flow meter, etc. Branch flow meters are being used.

In particular, the differential pressure flow meter is a flow meter that measures the flow rate by using the differential pressure of the fluid voltage (total pressure) and the fluid static pressure flowing in the pipe (meta body), the production is simple and expensive It is widely used due to its low cost.

Differential pressure flowmeters have been used for a long time because they are relatively simple in structure and can be easily used for flow measurement of almost all kinds of fluids. Therefore, because the flowmeter's characteristics and experimental data are abundant, it is possible to obtain measurement accuracy within several percent without additional calibration if the specification and manufacturing conditions of the specification are followed well. However, outflow coefficients and accuracy are greatly influenced by the type of pipe or the flow state of the fluid. Except for laminar flow meters, the output signal related to the flow rate is not linear but proportional to the square of the flow rate. In comparison, the measurement range is usually limited to 1: 3.

Among the differential pressure flowmeters, the orifice is most frequently used because of its very simple structure. Orifice is installed by orifice plate in pipe (pipe) and decreases the flow area of fluid according to the size of the flow rate to increase the speed, and accordingly the principle of the pressure difference and the pressure generated before and after It is a kind of differential pressure flowmeter device that calculates the flow rate using the relationship.

Thousands of years ago, the attempt to measure the Nile flow for agriculture began with the origins of flow measurement and began the commercialized fluid supply business from the late 19th century to the early 20th century. With the introduction of volumetric, turbine and propeller flowmeters, theories of various flowmeters including tightening flowmeters are essential for mass measurement of various products, commerce of fluids and energy, improvement of plant efficiency, and operation management. Was used.

As the development of mechanical materials, electronic materials, electronic components including microprocessors, and measurement and calculation methods, the functions and performance of the flow meter have been greatly improved, and together with the four elements of industrial measurement, thermometers, pressure gauges and level meters, As occupies an important position.

In recent years, the process of processing semiconductors for high-density electronic circuits and machine parts has been actively researched as a next-generation technology in the field of semiconductor technology, and the differential pressure converter system applying this technology is widely applied. It is becoming.

Orifices can be divided into flow measurement and flow restriction in terms of their use, due to their large differential pressure loss.

Orifice used for flow measurement is generally designed to have a pressure difference of less than 1㎏ / ㎠ and, if possible, a small differential pressure because the orifice tightening ratio (β = d / D) is generally used more than 0.3 in consideration of pressure drop. do.

On the other hand, in the case of a flow restricting orifice, the orifice tightening ratio is usually less than 0.3, and thus the differential pressure is quite large.

Orifice is widely used as a device for the purpose of lowering the pressure on high pressure oil and measuring the flow rate in a nuclear power plant or a thermal power plant. In order to increase the differential pressure by using the orifice, the hole size of the orifice should be made small and the tightening ratio should be made small to reduce the cross-sectional area through which the fluid flows. However, if the tightening ratio is made small in order to increase the pressure drop, the pressure downstream of the orifice drops rapidly below the saturated steam pressure at this temperature, and thus a cavitation phenomenon occurs in which water bubbles are generated. The cavitation generated at this time causes a great damage to piping materials such as piping, pumps, heat exchange, etc., and becomes a very serious factor in a nuclear power plant where stability is important.

The cavitation starts when the pressure in the pipeline in the fluid flow pipeline drops and approaches the vapor pressure of the flowing liquid, and the cavitation begins because the vapor is caused by the boiling of the liquid caused by the pressure drop rather than by the temperature increase. Indicates a state of droplet development. Cavitation results in cavity formation and rupture by steam.

Expansion of the cavitation can destroy pipelines, and the flow is unstable, destroying turbine blades and generating very high noise in turbines.

Therefore, suppression of cavitation is a very important factor in the design of the flow restricting orifice. In addition, the vibrations and noise generated when the bubbles are destroyed should also be considered in the design of the flow restrictor orifice, and the noise recommended by the nuclear power plant should be less than 85 dB at a distance of about 3 feet from the orifice.

In order to suppress cavitation resulting from pressure drop through orifices, many researches have been mainly focused on multi-stage orifices and flat multiple orifices, and now conical orifices are the mainstream. have.

The multi-stage orifice suppressed the occurrence of cavitation by installing several orifices at appropriate intervals according to the resistance coefficient K, pressure recovery and the number of cavitations.

이고, 유량계수(α)는 조임 기구를 설치한 관로에 비압축성 유체를 흘려 실험한 후 아래의 식에 의하여 구하는 값(Cd E)이며, 유출계수(cd)는 실제 유량과 이론 유량의 비이고, 팽창계수(ε)는 물(ε=1)이다.1 is a view for explaining the principle of a general orifice differential pressure flow measuring device, a plate-type tightening mechanism having a concentric hole in the center of the horizontal pipe having a circular cross section at right angles to the flow, the fluid is incompressible If the fluid is unaffected by viscosity, and the flow is flowing into the conduit as a normal flow, the Bernoulli equation and the continuous equation are established between the upper section a of the tightening section and the narrow section b of the downstream stream. Here, the tightening mechanism refers to a mechanism that is installed in the middle of the pipeline and is reduced in cross-sectional area, and the aperture ratio β is a ratio between the hole direct d of the tightening mechanism and the inner diameter D of the upstream pipe of the tightening mechanism (d / D). The differential pressure refers to the difference between the static pressure at the upstream side pressure outlet and the downstream side outlet of the tightening mechanism, and the proximity speed coefficient (E)

The flow rate coefficient α is a value Cd E obtained by the following equation after the experiment of flowing an incompressible fluid into a pipe in which a tightening mechanism is installed, and the discharge coefficient cd is a ratio between the actual flow rate and the theoretical flow rate. The coefficient of expansion ε is water (ε = 1).

Where V is the average velocity, P is the pressure, and ρ is the density of the fluid.

Therefore, the relationship between the volumetric flow rate Q through the tightening mechanism and the differential pressure (P ₁ -P ₂ )

However, since the actual flow rate is different from ideal assumptions such as friction of the fluid and inconsistency of the contraction part, in order to obtain the actual flow rate, the concept of the discharge coefficient described above should be introduced. For the actual fluid, the following equation applies.

In addition, Figure 2 shows a conventional conical orifice differential pressure flow measuring device 10, the conical portion 12 is formed in the central portion of the orifice plate 11, a number of holes in the conical portion 12 (13) is formed.

However, in the conventional conical orifice differential pressure flow measuring apparatus 10, since the hole 13 is large and asymmetrically formed, the cavitation is increased to increase vibration and noise as well as to destroy pipes, pumps, and piping materials. There is a serious problem, and there is a problem that can not measure the accurate flow rate due to the unstable fluid flow.

In order to achieve the above object, the present invention reduces the size of the hole formed in the conical portion, increases the number, arranges the holes in multiple stages, and forms the holes symmetrically so that the fluid passing through the hole is the center of the conical. It is an object of the present invention to provide a conical orifice differential pressure flow measurement device capable of preventing vibration and noise by offsetting cavitation without damaging the inner wall surface of a pipe (meta body) by inducing it to proceed along a line.

Conical orifice type differential pressure flow measurement apparatus according to the present invention in order to achieve the above object is a conventional conical orifice differential pressure of the conical portion is formed in the central portion of the orifice plate, the conical portion is formed with a plurality of holes In a flow rate measuring apparatus, a smaller number and larger number of holes are arranged in a plurality of stages in the conical part, and the holes are symmetrical with respect to the center line of the conical part. It is a structure to be formed.

The cross-sectional area of all of the holes (prior art) and the cross-sectional area of all of the holes (invention) have the same size, the holes are arranged in two stages, and the fluid passing through the hole is the center of the conical By guiding it along the line, it is possible to effectively prevent vibration and noise by offsetting the cavitation without damaging the inner wall surface of the pipe (meta body).

As described above, the present invention forms a relatively small hole size formed in the conical portion, increases the number, arranges the holes in multiple stages, and forms them in a symmetrical manner so that the fluid passing through the holes moves along the conical center line. By inducing the fluid so as not to damage the inner wall surface of the pipe, there is an effect that can prevent the vibration and noise by offsetting the cavitation.

1 is a view showing a typical orifice differential pressure flow measurement device
2 is a view showing a conventional conical orifice differential pressure flow measurement device
Figure 3 is a perspective view showing a conical orifice differential pressure flow measuring apparatus according to the present invention
Fig. 4 is a front view of Fig. 3
Figure 5 is a longitudinal sectional view showing a conical orifice differential pressure flow measurement apparatus according to the present invention
6 is a view illustrating a cavitation suppression and impact prevention structure in the conical orifice differential pressure flow measurement apparatus according to the present invention.
7 is a perspective view showing a modification of the conical orifice differential pressure flow measuring apparatus according to the present invention
8 is a front view of Fig. 7

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the conical orifice differential pressure flow measurement apparatus according to a preferred embodiment of the present invention.

Figure 3 is a perspective view showing a conical orifice differential pressure flow measuring apparatus according to the present invention, Figure 4 is a front view of Figure 3, Figure 5 is a longitudinal sectional view showing a conical orifice differential pressure flow measuring apparatus according to the present invention, and 6 is a view for explaining the cavitation suppression and impact prevention structure in the conical orifice differential pressure flow measurement apparatus according to the present invention.

Referring to the drawings, the conical orifice type differential pressure flow measurement apparatus 100 according to the present invention is a conical part 12 is formed in the central portion of the orifice plate 11, the conical part 12 Holes 130, for example 20 holes 130 and two further holes are formed. The plug P can be fastened to this additional hole.

The holes 130 are formed to be smaller in size and larger in number than the conventional holes 13 (refer to FIG. 2), so that the cross-sectional areas of the holes 13 and the holes 130 are formed to be the same. It is preferable.

The holes 130 are arranged in multiple stages, for example, two stages, in the conical portion 12, and the holes 130 refer to the center line L of the conical portion 12. It is formed in symmetry with each other.

A portion of the holes 130 can be plugged with a plug P for flow rate adjustment, in which case it is configured to block the plugs P in the holes 130 which are symmetrical to one another of the holes 130. .

The fluid passing through the holes 130 does not damage (impact) the inner wall surface of the pipe (meta body) by the symmetrical arrangement of the holes 130 to prevent the pipe damage and the center line (L). Proceeds along the configuration to offset the cavitation to prevent vibration and noise.

6 is a view for explaining a cavitation suppression and impact prevention structure in the conical orifice differential pressure flow measurement apparatus according to the first example of the present invention.

FIG. 6A illustrates a structure 10 in which an asymmetric hole 13 is formed in the conical portion 12 as in the related art, and FIG. 6B illustrates the conical portion 12 of the present invention. The symmetrical hole 130 is formed in FIG. 2, and the structure of the hole 130 is relatively small and arranged in two stages.

In the structure shown in FIG. 6A (prior art), a relatively large flow rate passes through the hole 13, and the fluid is asymmetrically viewed based on the center line L of the conical part 12. As the fluid flows, the fluid may damage the inner wall surface 14a of the pipe (meta body) 14, causing the pipe to be damaged.

On the other hand, in the structure shown in FIG. 6B (the present invention), a relatively small flow rate passes through the hole 130 and is symmetrical with respect to the center line L of the conical part 12. The fluid flows along the center line L so that the fluid does not damage the inner wall surface 14a of the pipe (meta body) 14 to prevent the pipe damage.

In general, in order to increase the differential pressure by using an orifice, the hole size of the orifice should be small to reduce the tightening ratio, and the cross-sectional area where the differential pressure flows through the differential pressure should be reduced. At this temperature, the temperature drops sharply below the saturated steam pressure, which causes a cavitation phenomenon. In the present invention, the size of the holes 130 is reduced, the number is increased, the holes 130 are arranged in multiple stages, and symmetrically. It is formed into a structure that suppresses the generation of cavitation. In other words, by allowing the fluid flowing through the hole 130 to move along the center line L of the conical part 12 to induce the cancellation of cavitation, vibration and noise can be effectively prevented.

On the other hand, Figure 7 is a perspective view showing a modified example of the conical orifice differential pressure flow measuring apparatus according to the present invention, and Figure 8 is a front view of FIG.

As shown in FIG. 7 and FIG. 8, conical portions 12 are formed in the central portion of the orifice plate 11, and a plurality of holes 230 are formed in the conical portions 12. The holes 230 are formed with a smaller size and a larger number than the conventional holes 13 (see FIG. 2), and the holes 230 are arranged in three stages in the conical part 12. The holes 230 may be formed at positions symmetrical with respect to the center line L of the conical part 12.

<Examples>

Experimental conditions: It consists of flow generator (pump), storage tank, test tube, flow rate control, weighing device, and control equipment. The flow generator is composed of two 10Hp pumps and one 40Hp pump for use according to the diameter of the pipe. Each pump is connected to the upper reservoir through the pipe and flows to the test tube. The upper reservoir is installed to stabilize the pulsating water discharged from the pump. The maximum discharge flow rate that can flow in a 4-inch pipeline is about 100 m 3 / h for a 10 Hp pump and about 300 m 3 / h for a 40 Hp pump. Since pumps are used as flow generators, the effects of pulsation due to changes in pump suction head, instability of power frequency, and impeller structure should be minimized.

The storage tank is designed to increase the base area to reduce the change in flow rate during the flow test, so that the water level changes less while the collection tank is filled with fluid, and the proper suction head is maintained even after filling the collection tank to cause pulsating flow. The vortices and swirl flows do not occur, and the total storage tank capacity is 60㎥.

For a conventional conical orifice with 12 asymmetric holes (1),

Reynolds numbers with cavitation were 15000, 6000, and 140000 when the tightening ratios were 0.1, 0.2, and 0.3,

For the conical orifice of the present invention with 20 symmetrical holes (2),

Reynolds number with cavitation is 17000, 62000, 180000 when tightening ratio is 0.1, 0.2, 0.3,

For the conical orifice of the present invention with 20 symmetrical holes (3),

Reynolds numbers with cavitation were measured as 18500, 70000, and 180000 when the tightening ratios were 0.1, 0.2, and 0.3, respectively.

Therefore, it could be confirmed that the more holes, the more cavitation was suppressed.

In addition, the noise generated in the orifice is closely related to the cavitation, in the case of the conical orifice of the present invention having 20 symmetrical holes (2), and in the case of the conical orifice of the present invention having 20 symmetrical holes (3). ) Were measured at 84 ㏈ and 80 각각 respectively. In both cases (1) and (2), the maximum noise measured was below 85 kHz, the recommended maximum noise for nuclear power plant orifices.

As described above, in the present invention, by forming a relatively small hole size formed in the conical portion, increasing the number, arranging the holes in multiple stages, and forming the symmetrical shape, the fluid passing through the hole travels along the conical center line. By inducing the fluid so as not to damage the inner wall surface of the pipe, there is an effect that can prevent the vibration and noise by offsetting the cavitation.

11: orifice plate
12: Conical Division
130: hole
L: Center Line of Conical Division

Claims (5)

In the conventional conical orifice differential pressure flow measuring device having a conical portion 12 is formed in the central portion of the orifice plate 11, the conical portion 12 is formed with a plurality of holes 13,
Smaller numbers and smaller numbers of holes 130 are arranged in the conical part 12 in a plurality of stages, and the holes 130 are conical part 12. Conical orifice differential pressure flow measurement device, characterized in that the structure is formed in a symmetrical position with respect to the center line (L) of the). The method according to claim 1,
Conical orifice differential pressure flow measurement apparatus, characterized in that the cross-sectional area of all of the holes (13) and the cross-sectional area of all of the holes (130) have the same size. The method according to claim 1,
Conical orifice type differential pressure flow measurement apparatus, characterized in that the holes 130 are arranged in two stages. The method according to claim 1,
Conical orifice type differential pressure flow rate, characterized in that when plugging a portion of the holes 130 for flow rate control, plug (P) is blocked in the holes 130 symmetric with each other among the holes (130) Measuring device. The method according to claim 1,
The fluid that has passed through the holes 130 is formed along the center line L without fluid impacting the inner wall surface 14a of the pipe (meta body) 14 by the symmetrical arrangement of the holes 130. Conical orifice type differential pressure flow measurement device characterized in that the structure to prevent the damage to the pipe to proceed.

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