JPH0518795A - Flow straightening duct and gas flow measuring device - Google Patents

Abstract

PURPOSE:To heighten the generality-of-use of a flow straightening duct and attain cost reduction by dividing a flow straightening throttle element into the common upstream side and the downstream side replaceable according to a flow meter, and jointing them in such a way as not to generate step difference to the connecting part. CONSTITUTION:Air flow passes a filter 12 held among a bell mouth 4 and meshes 10, 11, a flow assisting part 3 and a flow straightening grid 6, and flows into an upstream side throttle element 1. The air further flows into a downstream side throttle element 2 after passing a flow straightening grid 5 and flows out to a flow meter or the like outside a flow straightening duct. A connecting part between the throttle elements 1, 2, the inlet of the throttle element 1 and the outlet of the throttle element 2 are provided at points or blocks where an angle Q formed by the tangent of the curved inner wall surface and the main flow axial direction is changed continuously so as not to generate fluid separation in the vicinity of the inner wall surface, and connected in such a way that the angle Q at each connecting part is to be zero and the rate-of- change DELTAQ/DELTAX of the angle Q is to be zero. The connecting parts are jointed removably by bolts and nuts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifying duct and a gas flow measuring device, and more particularly to a gas flow meter for an internal combustion engine, which produces a gas flow with little turbulence, which is used when the measurement error is verified. The present invention relates to a rectifying duct and a gas flow rate measuring device suitable for use in air conditioning.

[0002]

2. Description of the Related Art Some conventional rectifying ducts are used as flow path elements in large-scale wind tunnel test equipment. This is used for model experiments and the like, and the cross-sectional area of the measurement part is several square meters or more, the contraction ratio is about 20 at maximum, and the flow velocity distribution is made uniform and disturbed by a maximum of ten or more rectification networks The damping is performed by the viscosity of the flow vortex. Such a rectifying duct has a relatively complicated structure because it was not necessary to manufacture a large number of rectifying ducts of the same type for the purpose of use.
No consideration was given to reduction of manufacturing cost, mass production, and miniaturization.

However, in addition to this, for the rectifying duct, which is used in the inspection process (quality control process) of the gas flow meter manufacturing line, etc. and has a relatively simple application used for the accuracy level verification of the flow meter, There is demand.

In the case of such a quality control process, the accuracy verification of the flow meter is performed under the same condition for each gas flow meter.
It is a task of giving a gas flow having a sufficiently low turbulence level and checking whether or not the dispersion of the measurement values (sampled values of a plurality of samples) of the flowmeter, for example, the standard deviation, is less than or equal to a preset target value. Under the same conditions, a rectifying duct is connected during the test to the inlet of the measured gas of the gas flow meter under test in order to provide a gas flow with a sufficiently low turbulence level.

In the actual verification work, it is necessary to perform this for each manufactured flow meter, and it is necessary to verify the accuracy level of a large number of flow meters within a limited inspection process time.
For this reason, it is important for the operation of the production line to reduce the inspection time per piece. In addition, there are many flowmeters to be inspected that have different intake gas inner diameters of the measurement gas depending on the specifications (measurement range) of the flow rate to be measured. For this reason, in order to prevent turbulence in the gas flow at the connection between the outlet of the rectifying duct and the inlet of the measurement gas of the flowmeter, it is necessary to prevent a step due to the difference in inner diameter at the connection. In this sense, the rectifying duct used in the accuracy verification of the flow meter is required to have versatility that can be applied to a plurality of flow meters having different measurement gas intake inner diameters.

The conditions required for the rectifying duct are as follows when the above conditions are summarized in consideration of the conditions actually used in the production line.

A) Providing a flow with less turbulence.

To prevent fluid separation near the inner wall surface of the duct as much as possible.

To reduce the swirling flow component in the mainstream.

B) To be versatile so as to satisfy a) for flowmeters of different inner diameters with few duct elements.

C) Small size and excellent in detachability and operability.

D) It is open type so that it can be used easily without limiting the place of use.

E) It can be manufactured at low cost, which is advantageous for use in a mass production line of flow meters.

F) Little pressure loss.

It is desirable that the rectifying duct actually used satisfies the above-mentioned conditions and that the turbulence of the gas flow is smaller than a certain prescribed value.

[Example applied to simple rectifying duct] Conventionally commonly used rectifying ducts include:
It is known to use a contraction nozzle composed of a curve of a cone, an arc, an ellipse, etc. Among them, a bell mouth using a quarter circle is often used. Also,
Fluid Mechanics Handbook edited by Japan Society for Fluid Mechanics (sho 62) pp.
As described in 807, it is generally effective to use a single cubic curve represented by the following equation (1) or a cosine curve represented by the equation (2) as a rectifying diaphragm. , And these curves have become relatively easy to process and use with the recent development of numerically controlled lathes.

[0017]

[Equation 1]

In addition, JIS standard Z8762-1988
Flow rate measuring method using throttle mechanism pp. As described in No. 7, from the flow velocity measuring section to the upstream side, 5 to 5
There is a method in which a run-up distance of about 0 times is taken and the flow velocity distribution is made uniform by damping due to the fluid viscosity.

In the rectifying duct actually used, the above-mentioned elements are not used alone, but the rectifying effect of these fluid elements is used in combination.

By the way, these fluid elements have the following features. First, the method of using a contracting nozzle that uses a cone, an arc, an ellipse, etc. as the curve of the throttle, or the bell mouth has the advantage of being relatively easy and inexpensive to process, while it is connected to the downstream It has a drawback that fluid peeling, which is one of the main causes of fluid turbulence, easily occurs at the connection surface with the straight pipe portion. This is because the direction of the streamline of the fluid is sharply bent at this connection because the rate of change in the curvature of the curve that gives the throttle structure is large,
This is because fluid peeling easily occurs. For this reason,
The condition of a) above cannot be satisfied.

Further, in the method of adopting a straight pipe as the rectifying duct, in order to reduce the magnitude of noise generated in the form of minute variations in the flow rate to a sufficient extent, at least 5 of the pipe inner diameter is used. A run-up distance of up to 50 times is required, and the rectifying duct is necessarily large. For this reason,
The condition of c) is not satisfied.

Further, a curved surface obtained by rotating a single cubic curve represented by the equation (1) or a cosine curve represented by the equation (2) around the mainstream axis is used as a diaphragm for rectification. Consider the case. Here, it is specified when the cross-sectional shape perpendicular to the mainstream axis of the throttle is circular, but the following description is that the cross-sectional shape perpendicular to the mainstream axis is rectangular or rectangular, and the cross-sectional shape of each part is similar. The same can be applied to the diaphragm. FIG. 5 is a sectional view showing each parameter when drawing an aperture using these curves. In the figure, the vertically symmetrical curves represent the curves of the formula (1) or the formula (2) and mean the inner wall of the cross section of the throttle channel. The white arrow indicates the flow of gas, and the gas has an inner diameter y.
It flows in from the inlet of i, passes through the entire length L of the throttle in the mainstream flow axis direction, and flows out from the outlet of inner diameter yo. Further, θ represents an angle formed by the tangent line of the inner wall surface of the curve and the mainstream flow axis direction. Hereinafter, the white arrow always indicates the flow of gas.

Due to the geometrical characteristics of the equations (1) and (2), these curves form a local corner portion because the angle θ is always zero at the throttle inlet portion 1a and the throttle outlet portion 1b. Not not. Also, when the above L, yi, and yo are made the same, when these curves are used, the angles at the throttle entrance and the throttle exit are greater than when using curves such as cones, arcs, and ellipses. The change rate of θ is small. For this reason, the streamline direction of the gas flowing near the inlet and outlet of the throttle gradually changes, and turbulence such as fluid separation is unlikely to occur.

As a result, the throttle using the curve of the formula (1) or (2) does not have the drawbacks of the contraction restrictor consisting of a curve of a cone, an arc, an ellipse, etc. This is advantageous in that the inner diameter can be set freely, that is, the contraction ratio (ratio of the inlet cross-sectional area to the outlet cross-sectional area) can be freely set.

Next, it is considered that the above curve is applied to the rectifying duct of the flow rate measuring device in the mass production line of the flow meter. FIG. 6 shows a case where the rectifying throttle 30 manufactured by using the above curve is connected to the downstream pipe 40. In this case, the rectifying diaphragm 3
Since the outlet inner diameter of 0 and the inner diameter of the downstream pipe 40 are equal, no step can be formed in the connection portion 50 between the flow restrictor 30 and the downstream pipe 40, and fluid separation hardly occurs. On the other hand, as shown in FIG. 7, when the inner diameter of the downstream side conduit 41 is not equal to the outlet inner diameter of the rectifying throttle 30, a step is generated at the connecting portion 51 between the rectifying restrictor 30 and the downstream side conduit 41, and fluid separation occurs. 60 occurs,
It causes fluid noise. To prevent this, see FIG.
As shown in FIG. 5, the rectifier throttle 31 whose outlet inner diameter is equal to the inner diameter of the downstream side conduit 41 may be manufactured separately from the rectifier throttle 30 and used. Since a plurality of rectifying diaphragms must be manufactured for each side conduit, the conditions of b) versatility and e) low manufacturing cost cannot be satisfied at the same time.

[0026]

In the above prior art, as shown in FIGS. 6 and 8, a plurality of single throttles having different outlet inner diameters must be manufactured for each of a plurality of downstream side pipelines having different inner diameters. I have to. As described above, in the related art, no consideration is given to the general use of the contraction throttle, and there is a problem that the average manufacturing cost of the rectifying duct increases.

An object of the present invention is to connect a straightening duct to a plurality of downstream side pipelines having different inner diameters without forming a step at the connecting portion.

[0028]

SUMMARY OF THE INVENTION The above-mentioned problem is that the rectifying throttle, which is the main part of the rectifying duct, is constituted by an upstream throttle element and a downstream throttle element detachably connected to the downstream side of the upstream throttle element. The inlet cross-sectional shape of the downstream throttling element and the outlet cross-sectional shape of the upstream throttling element are made to coincide with each other at the connecting portion, and the connecting portion is a tangent line between the plane including the mainstream axis of the rectifying throttle and the rectifying throttle. And is provided at a point or section where the angle θ formed by the mainstream axis direction changes continuously.

Further, the above-mentioned problem is that the rectifying throttle, which is a main part of the rectifying duct, is constituted by an upstream throttle element and a downstream throttle element detachably connected to the downstream side of the upstream throttle element, and the downstream throttle element is provided. The inlet cross-sectional shape of the throttling element and the outlet cross-sectional shape of the upstream throttling element are made to coincide at both connecting portions, and the connecting portion is connected to a plane including the main flow axis of the rectifying throttle and a tangent to the intersection line of the rectifying throttle and the main flow axis. Is provided at a point or section where the angle θ formed by the direction continuously changes, and further, the angle θ is set to zero at the inlet and outlet of the upstream throttle element and the downstream throttle element, and the main flow at the point where the angle θ is zero. Achieved by setting the rate of change of the axial angle θ to zero, sharing the upstream throttle element, and making the downstream throttle element a plurality of throttles whose outlet inner diameter matches the downstream pipe inner diameter at the connection. To be done.

Further, the above-mentioned problem is that the angle θ at the connecting portion between the upstream side throttle element and the downstream side throttle element is zero,
This can also be achieved by setting the rate of change of the angle θ in the mainstream flow axis direction at the point of zero to be zero.

[0031]

As described above, since the rectifying throttle is configured by detachably connecting the upstream throttle element and the downstream throttle element, the inlet inner diameter is the same for one upstream throttle element. It is possible to prepare a plurality of downstream throttling elements having different outlet inner diameters, select a downstream throttling element that matches the inlet inner diameter of the downstream conduit, that is, the gas flow meter, and connect it to the upstream throttling element. Therefore, by exchanging the downstream throttling element having a small inner diameter, the upstream throttling element having a large inner diameter can be commonly used for gas flow meters having different inlet inner diameters.

Since the angle θ continuously changes at the connecting portion between the upstream throttle element and the downstream throttle element, the direction of the streamline flowing near the connecting portion changes continuously and slowly. , Fluid delamination that causes fluid noise near the connection is prevented. Furthermore, if the angle θ at the inlet and the outlet of the rectification throttle is set to zero and the rate of change of the angle θ in the mainstream axis direction at the point where the angle θ is zero is zero,
The gas flow at the inlet and the outlet of the flow restrictor becomes a flow parallel to the main flow axis, and the gas flow flowing into the flow restrictor and / or the gas flow flowing out from the flow restrictor is less likely to be disturbed.
Fluid delamination is also reduced.

As a result, by sharing the upstream throttle element with the fluid noise level kept low,
The average manufacturing cost of the rectifying duct can be reduced.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, there are two types of flow straightening ducts, a circulating type and an open type. In the rectifying duct of the present invention, the open type is adopted so that it can be used easily without limiting the place, but when using the rectifying duct of the open type, it is necessary to consider the following conditions. There is.

First, in the case of an open type rectifying duct, if the atmosphere is allowed to flow into the measuring section as it is, dust contained in the atmosphere may also flow into the measuring section, which may adversely affect the measuring device. Moreover, since the place of use is not limited, it must be usable even if the flow velocity distribution on the upstream side is poor. A particularly bad condition for an open type rectifying duct is when the flow velocity distribution of the fluid has a bias (uneven flow) before flowing into the rectifying duct. In the case where the pipe or the measuring device is located upstream of the pipe, these become obstacles to the flow and cause uneven flow.

In the rectifying duct actually used, it is necessary to consider the measures against the above conditions.

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Rectifying duct 201 shown in FIG.
Is a bell mouth 4 that takes in air, and the bell mouth 4
The run-up portion 3 which is a straight pipe having a constant cross-sectional area, which is detachably connected with the mesh 10, the filter 12, and the mesh 11 interposed therebetween.
And a rectifying diaphragm detachably connected to the run-up portion 3 with the rectifying grid 5 interposed therebetween.

The rectifying throttle includes an upstream throttle element 1 and a downstream throttle element 2 which is detachably connected to the upstream throttle element 1 with a rectifying grid 6 interposed therebetween.

In FIG. 1 and FIG. 2 which is a view taken along the line I--I of FIG. 1, the air flow indicated by the white arrow is a resistor sandwiched by the bell mouth 4, the mesh 10 and the mesh 11. After passing through the filter 12, the run-up portion 3 and the rectifying grid 5, it flows into the upstream throttle element 1. Furthermore, after passing through the flow regulating grid 6, the air flows into the downstream throttle element 2 and flows out of the flow regulating duct. A bell mouth 4 is attached to the entrance of the approach portion 3 by bolting. The bell mouth 4 has a function of suppressing the amount of fluid separation generated at the peripheral portion of the inlet of the flow regulating duct to a low level, and the mesh 1
The mesh 0 and the mesh 11 and the filter 12 sandwiched by the meshes 0 and 3 serve to sandwich and fix the filter 12 and the run-up portion 3.

The filter 12 removes dust in the atmosphere.
Since the filter 12 has resistance to the air flow,
A differential pressure is generated between the upstream side and the downstream side, and this differential pressure is applied to the filter 12. Since dust is accumulated in the filter 12, it needs to be replaced frequently, and an inexpensive one is used. For this reason, non-woven fabrics or papers are often used, but these do not have sufficient strength to withstand the above-mentioned differential pressure. Further, considering that the rectifying duct is used as a test device many times, it is necessary to reinforce the filter 12. Therefore, in this example, in order to reinforce the filter 12, the mesh 10 and the mesh 11 are provided before and after the filter 12. It is provided. Further, when the filter 12 vibrates due to the inflowing air, this disturbs the flow and causes minute vibrations, which causes fluid noise. Mesh 10 and mesh 11
Also plays a role of fixing the filter 12 so as to prevent such a situation.

The filter 12 also serves as a measure against a drift on the upstream side of the rectifying duct. Since the filter 12 has a large resistance, it is possible to flatten the uneven flow generated before flowing into the rectifying duct, so that the uneven flow on the upstream side of the duct hardly affects the inside of the duct.

If the resistance distribution of the filter 12 is non-uniform, or if the drift on the upstream side of the rectifying duct is extremely large,
An uneven pressure distribution occurs in the cross section of the air flow after passing through the filter. If the pressure distribution in the fluid is biased, the fluid particles move toward the lower pressure side and a flow velocity is generated. In this case, there is a bias in the pressure distribution in the cross section perpendicular to the mainstream axis of the duct (hereinafter referred to as the horizontal cross section). Therefore, in the transient state until the bias in the pressure distribution becomes uniform, the fluid flow in the direction perpendicular to the mainstream axis of the duct The movement of particles occurs abruptly, which causes turbulence of the fluid. Therefore, the run-up distance is required until the bias of the pressure distribution becomes uniform. In this embodiment, the run-up portion 3 is formed by connecting a straight pipe portion having a constant cross-sectional area in front of the upstream throttle element 1 with a bolt nut. In order to shorten the length of the rectifying duct in the mainstream flow axis direction, it is desirable that the approach distance be short. In practice, the approach distance is 0.4D to 1.0D, where D is the inlet inner diameter of the upstream throttle element 1. It is enough. In the case of this embodiment, the approach distance is about 0.
4D.

Between the run-up portion 3 and the upstream throttle element 1, a rectifying grid 5 is bonded and fixed to the inlet portion of the upstream throttle element 1 as a fitting structure. The rectifying grid 5 has a function of removing a flow velocity component such as a swirling flow in a direction perpendicular to the main flow axis, and usually has a square shape or a regular hexagonal shape called a honeycomb. In this embodiment, a regular hexagonal duct having good isotropy is used so that the flow velocity distribution and the magnitude of noise do not easily change when the rectifying duct rotates about the mainstream axis.

The upstream throttle element 1 and the downstream throttle element 2 are
A rectifying grid 6 made of honeycomb is sandwiched between them and connected by bolts and nuts to form a two-stage drawing structure. The rectifying grid 6 has a fitting structure at the outlet of the upstream throttle element 1 and is fixedly installed by adhesion.

Upstream throttle element 1 and downstream throttle element 2
Uses the accelerated flow to prevent destabilization of the fluid during passage through the flow path. That is, the dynamic pressure of the fluid is moved from a relatively low state to a high state so as to satisfy the continuity equation and Bernoulli's law, and the flow overcomes the resistance of the wall friction near the inner wall, which causes fluid separation. At the same time as suppressing the occurrence of backflow, the flow velocity component in the direction perpendicular to the mainstream axis direction is converted into a flow in the mainstream axis direction. As a result, vortices, fluid separation, etc. that cause fluid noise are suppressed with a simple mechanism, and bias in the flow velocity distribution in the mainstream flow axis direction is eliminated.

The contraction flow ratio (ratio of the inlet cross-sectional area to the outlet cross-sectional area) to be set depends on the range of the flow rate used, but the Mechanical Engineering Handbook (Sho 61 Japan Society of Mechanical Engineers) Fluid Engineering A5 pp. 182 usually has a relatively large 5 to 20
It is stated that the range is good. In the case of the present embodiment, since it is assumed that the rectifying duct is simply attached and the measurement is performed, when the rectifying duct rotates with respect to the mainstream axis,
Regarding the mounting angle around the mainstream axis, it is necessary to make the fluctuations in the flow velocity distribution and the noise magnitude insensitive. Therefore, the contraction ratio is set to about 8 to 13, which is within the above range.

In general, the curve forming the rectifying diaphragm is
The use of functions such as equations (1) and (2) described above is edited by the Japan Fluid Mechanics Society, Fluid Mechanics Handbook (sho 62) pp. 80
7 and the like, and it has been reported that good results are obtained with respect to the rectification effect. Therefore, in this embodiment as well, the upstream throttle element 1 and the downstream throttle element 2 have the function of the formula (2). Is configured using. As described above, in the curves of the formulas (1) and (2), the angle θ formed by the mainstream axial direction and the tangent line of the mainstream direction of the curve continuously changes, and It is zero near the exit of the aperture. Further, in the present embodiment, as shown in the schematic view of FIG. 3, a connecting portion (point P ₁ ) between the run-up portion 3 and the upstream throttle element 1 and a connecting portion between the upstream throttle element 1 and the downstream throttle element 2. The angle θ and its rate of change Δθ / Δx in the mainstream flow axis direction are zero at (point P ₂ ) and near the outlet of the downstream throttle element 2 (point P ₃ ). For this reason, the direction of the flow line of the fluid flowing in the vicinity changes continuously and gently, and the fluid delamination that causes fluid noise is prevented.

A numerical control lathe is used when actually machining the inner wall surface of the throttle channel using the curves of the formulas (1) and (2). -There are some which can be given as a function, and these support polynomials such as equation (1) or trigonometric functions such as equation (2). For this reason, when using a numerically controlled lathe, if the curve to be machined is represented by an elementary function, it is not necessary to create a program that gives the machining sequence. Helps to reduce

The downstream throttling element 2 functions as a pipe for connection with the downstream pipelines having different inlet inner diameters in addition to the above-described rectifying function. FIG. 4 shows downstream throttle elements 21, 22, 23 having an inlet inner diameter equal to the outlet inner diameter of the upstream throttle element 1 and different outlet inner diameters. The respective outlet inner diameters are matched to the inlet inner diameters of the different downstream conduits.

In this embodiment, the downstream throttle element 2 is composed of a plurality of throttle elements whose inlet inner diameter matches the outlet inner diameter of the upstream throttle element 1 and whose outlet inner diameters are different from each other. , So that they can be connected and exchanged with each other.
When the straightening duct is used, the downstream throttle element 2 having the same outlet inner diameter as each downstream pipe diameter to be connected is selected from the plurality of throttle elements 21, 22, 23, etc., and the selected downstream throttle element is selected. 2 may be used by connecting it to the upstream throttle element 1. As a result, the upstream side throttle element 1 can be commonly used, and the rectifying ducts can be connected to the plurality of downstream side pipelines having different inlet inner diameters without the step of the connecting surface, and the fluid separation due to the step of the connecting surface can be prevented. Moreover, the range of use of the rectifying duct can be expanded.

Further, by constructing the flow path with the two-stage throttle structure in this way, the following advantages in manufacturing cost can be obtained. That is, the upstream throttle element 1 can be shared, and the downstream throttle element 2 is geometrically smaller in diameter than the upstream throttle element 1. Therefore, even if a plurality of downstream throttle elements 2 are prepared, their material cost and Since the processing cost can be kept low, the average manufacturing cost of the rectifying duct can be reduced.

Further, there are the following manufacturing process advantages. That is, when manufacturing the drawing structure by cutting with a lathe, it is necessary to estimate the thermal expansion and deformation of the workpiece due to its own weight to maintain the dimensional accuracy of the inner diameter, but this method maintains the dimensional accuracy of the inner diameter. Inevitably, it becomes more difficult as the inner diameter of the diaphragm increases. Therefore, when a large number of diaphragms are manufactured to reduce the instrumental error, it is easier to reduce the instrumental error when mass-producing a diaphragm element having a relatively small diameter. According to the present embodiment, such a manufacturing method is used. Can be applied.

Similar to the rectifying grid 5, the rectifying grid 6 has a function of removing a flow velocity component in a direction perpendicular to the main flow such as a swirling flow, and the deviation of the connection between the upstream throttle element 1 and the downstream throttle element 2. It acts to prevent the occurrence of fluid peeling that occurs at the stepped portion formed by the above.

In the present embodiment, all the air passages have a circular cross section, but the present invention can be similarly applied even if the air flow paths do not necessarily have a circular cross section.

A second embodiment of the present invention will be described with reference to FIG. 9 and FIG. 10 which is a view taken along the line II-II of FIG. This embodiment is an example in which the length of the flow straightening duct in the mainstream flow axis direction is limited. The difference from the first embodiment is that the flow passage cross-sectional area is constant on the upstream side of the upstream throttle element 1. Instead of bolting the bell mouth via the run-up portion 3, the point at which the bell mouth 7 of the quarter circle is directly connected by the bolt nut and the radius of curvature R of the quarter circle of the bell mouth 7 are A point that is about 1/4 of the inlet inner diameter of the upstream throttle element 1 and is larger than the radius of curvature of the bell mouth 4 of the first embodiment,
Mesh 8 and filter 12, rectifying grid 5 and bell mouth 7
It is a point fixed between the two. The bell mouth 7 rectifies the air flow before the flow flows into the upstream throttle element 1 by the contraction effect, and suppresses the turbulence of the fluid to the same extent as when the run-up portion 3 is installed.

In the case of this embodiment, unlike the first embodiment, the rectifying grid 5 has the function of removing the swirling flow component of the air flow, and instead of the mesh 11 of the first embodiment,
It also has a function of supporting the filter 12. Further, there is a drawback that the inlet outer diameter of the rectifying duct, that is, the outer diameter of the bell mouth 7 must be made larger than that of the first embodiment. However, the length of the bell mouth 7 in the mainstream axis direction is a runway. Since the length can be made shorter than the length of the portion 3, the length of the entire rectifying duct in the mainstream flow axis direction can be shortened.

A third embodiment of the present invention will be described with reference to FIG. The present embodiment is intended to further reduce the influence of the drift on the upstream side of the rectifying duct shown in the first embodiment.
In the straightening duct of this embodiment, instead of connecting the bell mouth 4 to the upstream side of the run-up portion 3 of the first embodiment by bolts, the frustoconical expansion pipe portions 13 and 14 and the straightening duct are used as piping elements. An expansion conduit is constructed by connecting the run-up portion 15 which also serves as a connecting portion used at that time with a bolt and nut. Further, a rectifying grid 16 is provided between the expansion tube portions 13 and 14.
Is a straight pipe with a constant cross-section area
A rectifying grid 17 is fitted and adhered in the middle of each. The other parts are the same as those in the first embodiment, and the same reference numerals are given to omit the description.

The expanded conduit constructed as described above converts the dynamic pressure into static pressure according to Bernoulli's law, and further makes the static pressure uniform, thereby biasing the dynamic pressure, that is,
Acts to eliminate drift. In this case, since the air flow becomes a decelerating flow, fluid separation easily occurs on the inner walls of the expansion tube portions 13 and 14, so that the flow control grids 16 and 17 are provided to prevent the fluid separation.

In the case of the present embodiment, in addition to the upstream side throttle element 1 and the downstream side throttle element 2, the expansion tube portions 13 and 14 and the run-up portion 15 must be further manufactured, which results in a disadvantage of high manufacturing cost. However, the influence of uneven flow generated on the upstream side of the rectifying duct can be further reduced as compared with the case where the approaching section 3 alone is reduced.

The fourth embodiment of the present invention will be described with reference to FIGS.
And FIG. 14 will be described. This embodiment shows an example of another method for realizing the two-stage aperture structure shown in the first embodiment. Also in the present embodiment, similarly to the first embodiment, by the upstream throttle element 1 and the downstream throttle element 20,
The two-stage throttle structure is constituted, and the functions of the downstream side throttle element 20 as a rectifying throttle and a connecting pipe are also the same as in the case of the first embodiment. The downstream throttle element 20 is composed of a plurality of downstream throttle elements 24, 25, 26 and the like having the same inlet inner diameter as the outlet inner diameter of the upstream throttle element 1 but different outlet inner diameters. The fact that they can be connected and exchanged with each other is also the same as in the case of the first embodiment. However, in this embodiment, unlike the first embodiment, arcs are used to form the diaphragm structure.
Further, the downstream throttle element may be constituted by a plurality of downstream throttle elements 27, 28, 29 using straight lines as shown in FIG. Further, in this embodiment, the flow straightening grids 202, 240, 250, 260 for preventing fluid separation at the connection between the outlets of the downstream throttle elements 24, 25, 26, 27, 28, 29 and the downstream pipelines. , 270, 280, 2
90 is fitted and glued into the outlet of the downstream throttling element.

In the case of this embodiment, since arcs or straight lines are used to form the diaphragm structure, the formulas (1) and (2) are used.
Although it has the drawback that fluid peeling is more likely to occur on the inner wall surface of the throttle than when using the formula curve, it has the advantage in manufacturing that it is suitable for mass production because the inner wall of the throttle can be processed relatively easily. To have.

FIG. 15 shows a fifth embodiment of the present invention, in which the rectifying duct 201 of the first embodiment is applied to an air flow measuring device. The illustrated air flow rate measuring device includes an airtight container 600, a partition wall 600c for partitioning the airtight container 600 into a chamber 600a and a chamber 600b, and both of the chambers 600a and 600b installed on the partition wall 600c.
Sonic nozzles 300, 301, 302 communicating with each other,
Chamber 6 of the sonic nozzles 300, 301, 302
Solenoid valves 500, 501 connected to the 00b side,
502, an opening 600d provided on the wall surface forming the chamber 600a of the container 600, a flowmeter mounting seat 600e attached to the opening 600d and connected to the downstream side of the air flowmeter 100 to be measured, and the measurement target Air flow meter 1
00 downstream end 200 connected to the upstream side of 00,
A rectifying duct 201 whose outlet side is connected to the other end of the downstream side pipeline 200, a vacuum pump 400 which is connected to the chamber 600b to decompress the chamber 600b, and the opening and closing of the solenoid valves 500, 501, 502. Vacuum pump 400
And a computer 700 for controlling start and stop of the. The rectifying duct 201 is the one described as the first embodiment. In the figure, white arrows indicate air flow paths.

The operation of the air flow rate measuring device having the above configuration will be described below. Prior to the start of measurement, the air flow meter 100 to be measured is mounted on the flow meter mounting seat 600e,
The downstream end of the downstream pipe line 200 is connected to the upstream side of the air flow meter 100. Next, the outlet side of the downstream throttle element 2 of the rectifying duct 201 is connected to the upstream end of the downstream pipe line 200. First, the air flow rate to be measured is set in the computer 700, and at least one solenoid valve required to generate the set air flow rate is opened. Then compute
The vacuum pump 400 is activated by the motor 700, the pressure inside the chamber 600b is reduced, and a negative pressure is applied to the inside of the chamber 600a. The air passes through the rectification duct 201, is rectified, and then passes through the air flow meter 100, the chamber 600a, and the sonic nozzles 300, 301, 302 that are to be measured and are connected to the opened solenoid valve. do it,
It flows into the chamber 600b. The chamber 600a and the chamber 600b are partitioned by electromagnetic valves 500, 501, 502 whose opening and closing are controlled by the computer 700. At this time, the sonic nozzles 300, 301, 302 are evacuated by evacuating the chamber 600b. A sonic flow with a constant flow rate is generated. As a result, the flow rate of air passing through the rectifying duct and the air flow meter 100 becomes a value determined by the number and combination of the opened solenoid valves.

[0064]

According to the present invention, the rectifying throttle (throttle element) of the rectifying duct is composed of the upstream throttle element and the replaceable downstream throttle element connected to the outlet side of the upstream throttle element. Therefore, match the outlet inner diameter of the downstream throttle element with the smaller diameter to the inlet inner diameter of the gas flow meter, and use the upstream throttle element with the larger diameter into multiple downstream throttle elements with different outlet inner diameters without reducing the rectification effect. It becomes possible to make it common to
The common use range of the flow straightening duct is expanded, and the average manufacturing cost is reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a straightening duct according to a first embodiment of the present invention taken along a plane passing through a mainstream axis.

FIG. 2 is a front view taken along the line II of FIG.

FIG. 3 is an explanatory diagram showing a curve forming the flow regulating duct of the first embodiment of the present invention.

FIG. 4 is a front view and a vertical sectional view showing a plurality of downstream side throttle elements that constitute the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a rectifying throttle curve used in the first embodiment of the present invention.

FIG. 6 is a vertical sectional view showing an application example of a conventional rectifying diaphragm.

FIG. 7 is a vertical cross-sectional view showing an application example of a conventional rectifying diaphragm.

FIG. 8 is a vertical sectional view showing an application example of a conventional rectifying diaphragm.

FIG. 9 is a vertical cross-sectional view showing a rectifying duct of a second embodiment of the present invention cut along a plane passing through a mainstream axis.

10 is a front view taken along the line II-II of FIG.

FIG. 11 is a vertical cross-sectional view showing a rectifying duct of a third embodiment of the present invention cut along a plane passing through a mainstream axis.

FIG. 12 is a vertical cross-sectional view showing a straightening duct of a fourth embodiment of the present invention cut along a plane passing through a mainstream axis.

13A and 13B are a front view and a vertical sectional view showing a first example of a plurality of downstream throttle elements that constitute a fourth embodiment of the present invention.

14A and 14B are a front view and a vertical sectional view showing a second example of a plurality of downstream throttle elements that constitute a fourth embodiment of the present invention.

FIG. 15 is a sectional view showing an air flow rate measuring device according to a fifth embodiment of the present invention.

[Explanation of symbols]

1 upstream side throttle element 1a throttle inlet part 1b throttle outlet part 2 downstream side throttle element 3 runner part 4,7 bellmouth 5,6,16,17 rectifying grid 8,10,11 mesh 12 filter 13,14 expansion tube part 15 Run-up section 20 Downstream-side throttle element 30, 31 Straightening throttle 40, 41 Downstream-side pipeline 50, 51, 52 Connection section 21, 22, 23, 24, 25, 26, 27, 28, 2
9 Downstream Throttle Element 60 Fluid Separation 100 Air Flowmeters 202, 240, 250, 260, 270, 280, 2
90 Rectification grid 300,301,302 Sonic nozzle 400 Vacuum pump 500,501,502 Electromagnetic valve 600 Container 600a Chamber a 600b Chamber b 600c Partition wall 600d Opening 600e Flowmeter mounting seat 700 Computer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Motoyuki Miyagawa             2520, Takaba, Katsuda City, Ibaraki Prefecture             Hitachi, Ltd. Automotive Equipment Division (72) Inventor Hiroshi Onikawa             2520, Takaba, Katsuda City, Ibaraki Prefecture             Hitachi, Ltd. Automotive Equipment Division

Claims (16)

[Claims] 1. A rectifying throttle forming a rectifying duct used for gas flow rectification, wherein the rectifying throttle comprises an upstream throttle element and a downstream throttle element detachably connected to the upstream throttle element, and the downstream throttle element is downstream. The inlet cross-sectional shape of the side throttle element and the outlet cross-sectional shape of the upstream throttle element are the same at the connecting portions of the two, and the connecting portion has a tangent to the plane including the mainstream axis of the rectifying throttle and the tangent line of the rectifying throttle, and the mainstream. The angle θ formed by the axial direction is
A rectifying diaphragm, which is provided at a point or a section that continuously changes. 2. The rectifying diaphragm according to claim 1, wherein the angle θ at the connecting portion is zero. 3. In a rectifying throttle forming a rectifying duct used for gas flow rectification, when an angle formed by a tangent line of a plane including a mainstream axis of the throttle and a tangent line of the rectifying throttle and the mainstream axis direction is θ. , Including at least one section in which the rate of change of the angle θ in the mainstream flow axis direction in the mainstream flow axis direction is zero at the point where the angle θ is zero and the angle θ is zero, and in the mainstream flow axis direction of this section A rectifier diaphragm having a vertical rectifier cross-sectional area larger than an outlet cross-sectional area of the rectifier diaphragm. 4. The angle θ continuously changes between the inlet portion and the outlet portion of the rectifying throttle, the angle θ is zero at the inlet and / or the outlet portion of the rectifying throttle, and the main flow of the angle θ is The rate of change in the axial direction is zero.
The rectifying diaphragm according to any one of 1 to 3. 5. The rectifying grid is installed in a section where the angle θ is zero and the rate of change of the angle θ in the mainstream axis direction at the point where the angle θ is zero is zero. Claim 3
Rectifier diaphragm described in. 6. The rectifying throttle according to claim 1, wherein a rectifying grid is installed at a connecting portion between the upstream throttle element and the downstream throttle element. 7. A rectifying throttle forming a rectifying duct used for gas flow rectification, wherein the rectifying throttle is constituted by an upstream throttle element and a downstream throttle element detachably connected to a downstream side of the upstream throttle element. A rectifying throttle which is configured such that an inlet cross-sectional shape of a downstream throttle element and an outlet cross-sectional shape of an upstream throttle element match at a connecting portion, and a rectifying grid is installed at the connecting portion. 8. The rectifying diaphragm according to claim 1, wherein a line of intersection between the rectifying diaphragm and a plane including a mainstream axis of the rectifying diaphragm is constituted by a cosine curve. 9. The rectifying throttle according to claim 1, an approaching section having a constant cross-sectional area connected to the upstream side of the rectifying element on the upstream side of the rectifying diaphragm with a rectifying grid interposed therebetween, and the approaching run. Rectification duct including a resistor connected to the upstream side of the section. 10. The rectifier throttle according to claim 1, a resistor connected upstream of the upstream throttle element of the rectifier with a rectifying grid interposed therebetween, and an upstream side of the resistor. A rectifying duct including a throttle connected to the. 11. The rectifier throttle according to claim 1, a resistor connected to the upstream side of an upstream throttle element of the rectifier throttle with a rectifying grid interposed therebetween, and an upstream side of the resistor. And a pipe having a passage cross-sectional area that increases in the downstream direction. 12. The flow straightening duct according to claim 9, wherein a conduit whose passage cross-sectional area increases in the downstream direction is connected to the upstream side of the run-up portion. 13. The rectifying duct according to claim 9, wherein the resistor is a dust removing filter. 14. A dust removal filter in which a resistor is sandwiched between an upstream mesh and a downstream mesh, and the thickness of the core wire of the upstream mesh is not larger than the thickness of the core wire of the downstream mesh. The rectifying duct according to any one of claims 9 to 12. 15. The rectifying throttle according to any one of claims 1 to 8 or the rectifying duct according to any one of claims 9 to 14, and a straight section having a constant cross-sectional area on the downstream side of the rectifying throttle or the rectifying duct. A gas flow rate measuring unit configured to include a gas flow meter connected with a downstream side pipe line which is a pipe section interposed therebetween. 16. A gas chamber having at least two compartments, at least one sonic nozzle communicating with the two compartments, a vacuum pump having its inlet side connected to one of the two compartments, and the two 16. The gas flow rate measurement device according to claim 15, wherein the opening is provided in the other of the compartments, the gas flow meter mounting seat is airtightly fixed to the opening, and the gas flow meter mounting seat is airtightly and detachably coupled to the opening. A gas flow rate measuring device including a means.