JPH10213464A - System for measuring exhaust gas flow rate of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably measure the flow rate of exhaust gas of an engine to be regulated with respect to the exhaust gas. SOLUTION: An exhaust gas inflow pipe 1, a damper 2 and a spiral flow meter 9 having a commutator 4 are sequentially mounted to the exhaust port of an engine. In order to measure exhaust gas within a flow rate range from an idling time to a full opening time of accelerator, a spiral detector 6 is protected from being influenced by the pulsating pressure of the exhaust gas, the vibration of the engine or the like. Also, the sectional shape of a spiral generator 5 is selected to increase the number of St and enlarge always the spiral frequency larger than the frequency of the pulsating pressure so that the detection of a spiral signal is prevented from being disabled by the interference of the spiral frequency with the pulsating pressure frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas flow measurement system, and more particularly, to an engine exhaust gas flow measurement system for preventing pollution caused by engine exhaust gas without being affected by pulsating pressure of engine exhaust gas or engine vibration. Also, the present invention relates to an engine exhaust gas flow measurement system using a vortex flow meter that stably and accurately measures an exhaust gas flow at an engine speed from an engine idling to an accelerator fully open.

[0002]

2. Description of the Related Art Exhaust gas from automobiles contains suspended particulates such as CO ₂ and NO _X and causes air pollution. In particular, the exhaust gas of diesel engines is subject to exhaust gas regulations because it contains a large amount of suspended particulates, which are indicated to be carcinogenic. In order to develop an engine that passes the exhaust gas regulations, the flow rate of the exhaust gas is measured and the chemical components of the exhaust gas are analyzed, and pollutants in the exhaust gas discharged according to the engine speed are measured. Seeking quantity.

As a flow meter for measuring the flow rate of exhaust gas, there is a vortex flow meter. As is well known, a vortex flowmeter is composed of a measurement tube through which a fluid to be measured flows, a vortex generator having opposite ends or one end fixed to the flow in the measurement tube, and a vortex detector. It is based on the fact that the number of Karman vortices flowing out per unit time (hereinafter referred to as vortex frequency) is proportional to the flow rate in a predetermined Reynolds number (hereinafter referred to as Re number) range regardless of gas or liquid. This proportionality constant is called the Strouhal number (hereinafter referred to as St number).

[0004]

However, the exhaust gas of an automobile engine contains a pulsating pressure proportional to the engine speed and the number of cylinders. The exhaust gas of the engine is usually discharged through a muffler, but keeps a high temperature state and reaches a maximum temperature of 500 ° C. Further, in addition to the above high temperature, it contains fine particles such as moisture and sticky black smoke.

The exhaust gas of the engine is a gas having a high pulsating pressure containing sticky fine particles at a high temperature and high humidity, and it is difficult to measure the flow rate stably and accurately with a conventional vortex flow meter. Further, since the flow rate of the exhaust gas of the engine changes according to the number of revolutions of the engine, a wide flow rate range from idling to full opening of the accelerator, for example, 1: 1
It is required to be measured with a flow range of 00,
Moreover, it must be measured with a low pressure loss that does not affect the characteristics of the engine.

Further, in the vortex flowmeter, in order to measure the flow rate of the exhaust gas of the engine under the above-mentioned conditions, the components of the vortex flowmeter are made of heat-resistant members. Although it is possible to suitably cope with this, the pulsating pressure of the exhaust gas generated in proportion to the engine speed makes the vortex signal at a small flow rate at idling unstable, and furthermore, the pulsating pressure frequency and the vortex pressure When the frequency approaches, the vortex frequency and the pulsating pressure frequency interfere with each other, and the vortex waveform is disturbed. As a result, the vortex cannot be detected accurately, and the measurement error of the flow rate increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and attenuates the pulsating pressure of the exhaust gas of the engine flowing into the vortex flow meter to thereby reduce the SN of the vortex signal at a small flow rate.
The vortex frequency generated by the exhaust gas flowing in proportion to the engine speed is always higher than the pulsating pressure frequency of the exhaust gas generated in proportion to the engine speed, thereby improving the flow rate measurement range. It is an object of the present invention to provide an engine exhaust gas flow rate measuring system capable of detecting a stable vortex in the engine.

[0008]

According to a first aspect of the present invention, there is provided an engine exhaust gas flow rate measuring system for measuring an exhaust gas flow rate of an engine, wherein the pulsating pressure damping means attenuates the pulsating pressure of the exhaust gas; Vibration damping means for damping vibrations generated from the engine and transmitted through the pipe,
A rectifying means for rectifying the flow of the exhaust gas, and a vortex flow meter having a vortex generator for generating a vortex having a frequency always higher than the pulsating pressure frequency of the engine; The damping means, the vibration damping means, the rectifying means, and the vortex flow meter are sequentially connected.

According to a second aspect of the present invention, in the engine exhaust gas flow rate measuring system according to the first aspect, the pulsating pressure damping means and the vibration damping means are integrated.

[0010] The invention of claim 3 is claim 1 or claim 2.
In the engine exhaust gas flow measurement system described in the above, one or more rectification means is further provided between the exhaust port of the engine and the rectification means, in addition to the rectification means.

According to a fourth aspect of the present invention, there is provided an engine exhaust gas flow rate measuring system according to any one of the first to third aspects.
The cross-sectional shape of the vortex generator attached to the vortex flowmeter is an isosceles triangle having a base perpendicular to the flow on the upstream side.

According to a fifth aspect of the present invention, in the engine exhaust gas flow rate measuring system according to any one of the first to third aspects,
The cross-sectional shape of the vortex generator mounted on the vortex flowmeter is a trapezoid having a pair of opposite sides perpendicular to the flow.

According to a sixth aspect of the present invention, there is provided an engine exhaust gas flow rate measuring system according to any one of the first to third aspects,
The cross-sectional shape of the vortex generator attached to the vortex flowmeter is an isosceles triangle having a base perpendicular to the flow on the downstream side.

According to a seventh aspect of the present invention, in the engine exhaust gas flow rate measuring system according to any one of the first to third aspects,
The cross-sectional shape of the vortex generator attached to the vortex flowmeter is a rectangle whose long side is a side perpendicular to the flow.

According to an eighth aspect of the present invention, there is provided an engine exhaust gas flow rate measuring system according to any one of the first to third aspects.
The cross-sectional shape of the vortex generator mounted on the vortex flowmeter is a convex shape having a bottom side perpendicular to the flow on the upstream side and a projection on the downstream side.

According to a ninth aspect of the present invention, in the engine exhaust gas flow rate measuring system according to any one of the first to third aspects,
The vortex generator mounted on the vortex flowmeter has a composite shape in which at least two or more of an isosceles triangle, a trapezoid, a rectangle, or a convex shape are installed at predetermined intervals in the flow direction. .

According to a tenth aspect of the present invention, in the engine exhaust gas flow measurement system according to any one of the first to ninth aspects, the cross section perpendicular to the axial direction of the flow path of the vortex flow meter is rectangular, and the vortex generator Is vertically inserted into one side of the rectangle, and a side perpendicular to one side of the rectangle into which the vortex generator is inserted is defined as a long side of the rectangle.

According to an eleventh aspect of the present invention, in the engine exhaust gas flow measurement system according to any one of the first to tenth aspects, the vortex generator and the vortex detector mounted on the vortex flowmeter are attached to and detached from the vortex flowmeter main body. It has been supported as much as possible.

According to a twelfth aspect of the present invention, in the engine exhaust gas flow measurement system according to any one of the first to tenth aspects, at least one purge hole is provided in the vortex flowmeter main body.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan sectional view in the flow direction of an engine exhaust gas flow rate measuring system for explaining an embodiment of the present invention, wherein 1 is an inlet pipe, and 2 is an attenuation pipe. Reference numeral 3 denotes a vortex flowmeter main body (hereinafter referred to as a main body), 4 denotes a rectifier, 5 denotes a vortex generator, 6 denotes a vortex detector, 7 denotes a converter, 8 denotes a CPU, and 9 denotes a vortex flowmeter.

The engine exhaust gas flow measurement system shown in FIG. 1 has an inflow pipe 1 connected to an engine exhaust port (not shown), one end connected to the inflow pipe 1, and the other end connected to a vortex flowmeter 9. Attenuator 2. The inflow pipe 1 has an enlarged opening 1b, and a rectifier 1a is attached to the enlarged opening 1b. The attenuator 2 is formed of, for example, a flexible tube or the like, and is deformable so as to be able to expand and contract in the axial and radial directions. Further, the vortex flowmeter 9 includes a main body 3 having an enlarged opening 3a to which a rectifier 4 is attached on a side to be joined to the attenuator 2,
A vortex generator 5 and a vortex detector 6 provided on the downstream side of the vortex generator 5; the vortex detector 6 is connected to a converter 7;
Further, it is connected to the CPU 8.

The vortex detector 6 is, for example, connected to a thin metal pressure plate and is connected to the metal pressure plate in order to withstand high temperatures and to detect the fluctuating pressure of the vortex flowing at a small flow rate during idling. It is composed of a piezoelectric element or the like. Since the vortex detector 6 has high sensitivity, there is a risk of detecting noise in response to external vibration of an engine or the like. The attenuator 2 removes these vibrations by its own deformation, and the attenuator 2 forms one volume together with the inflow pipe 1, and the resistance elements of the rectifiers 1 a and 4 filter the π-type filter against the pulsating pressure of the exhaust gas. And effectively removes pulsating pressure. Note that the same effect can be obtained by using the rectifier 4 alone.

FIG. 2 is an exploded perspective view of the vortex flowmeter 9 shown in FIG. 1. In FIG. 2, parts having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

In FIG. 2, the cross-sectional shape of the main body 3 is circular on the rectifier 4 side, and the portion where the vortex generator 5 and the vortex detector 6 are mounted is rectangular, and the enlarged opening 3a has a rectangular cross section from a circular cross section. It has an aperture curve that can be squeezed continuously. The vortex generator 5 has a mounting flange 5a on one end side, and is inserted vertically into the flow path of the main body 3 with respect to the flow, and a bolt 5
b and the like. Similarly, the vortex detector 6 has a mounting flange 6b on one end side, a pressure receiving plate 6a is inserted into the flow path of the main body 3 in parallel with the flow, and is joined by bolts or the like (not shown). Transducer 7 is flange 7a
Are joined through.

FIG. 3 is a diagram for explaining the relationship between the flow velocity of the exhaust gas and the vortex frequency. The cross-sectional shape of the vortex generator 5 is such that the side in the direction perpendicular to the upstream flow is the bottom of width d, Assuming that an isosceles triangle having a height h is provided on the downstream side and the flow velocity of the exhaust gas is V, the vortex frequency f is represented by f = St (v / d) (1). If the St number is a constant when the width d is constant, the vortex frequency f is proportional to the flow velocity v of the exhaust gas.

On the other hand, the pulsating pressure frequency F of the exhaust gas of the engine is F = (１ ／) (N / 60) M (2) where the engine speed is N and the number of cylinders is M in the case of a four-cycle engine. ). The flow velocity v of the exhaust gas is proportional to the engine speed N because the cross-sectional area of the inflow pipe 1 is constant. The vortex frequency f is proportional to the flow velocity v of the exhaust gas and the St number, but at a small flow rate with a small Re number, the St number changes and cannot maintain linearity. Therefore, depending on the value of the St number, the pulsating pressure frequency F of the exhaust gas depends on the value of the St number. And the vortex frequency f approach.

FIG. 4 is a graph showing the relationship between the engine speed N, the pulsating pressure frequency F of the exhaust gas, and the vortex frequency f.
The horizontal axis indicates the engine speed N and the vertical axis indicates the frequency. The relationship between the engine speed N and the pulsating pressure frequency F, the vortex frequency f _A of the vortex flowmeter having the diameter _A , and the vortex having the diameter B (A> B) shows the relationship between vortex frequency f _B of the flowmeter. FIG.
FIG. 3 is a diagram showing a relationship between a vortex waveform and a trigger waveform at an engine speed.

In FIG. 4, the broken lines indicate the maximum and minimum flow rate measurement ranges of the flow meter. Vortex frequency f _A intersects the pulsating pressure frequency 2F of the exhaust gas in terms of the engine rotational speed No. At the position of N = No, as shown in FIG. 5B, the vortex waveform (1) interferes with the pulsating pressure of the exhaust gas and is disturbed. To cause an error. On the other hand, N> No, N shown in FIGS.
In <No>, the vortex waveform (1) and the trigger waveform (2) are output very regularly. On the other hand, the vortex frequency f
_B is always above the pulsating pressure frequencies F and 2F of the exhaust gas within the flow rate measurement range and does not cross each other.

The relationship between the vortex frequency f and the pulsating pressure frequency F of the exhaust gas shown in FIG. 4 is a result obtained by the difference between the bores A and B.
In order to obtain the above, it is necessary to increase the St number without increasing the flow velocity v of the exhaust gas. Therefore, it is important to select the cross-sectional shape of the vortex generator 5. According to the experimental results of the present applicant, it has been found that in the cross-sectional shape of the vortex generator 5, the length h in the flow direction changes the St number with respect to the representative length d perpendicular to the flow.

FIG. 6 is a diagram showing an example of the cross-sectional shape of the vortex generator according to the first to third aspects of the present invention. ), The vortex generator 5B in FIG. 6 (B), and the vortex generator 5C in FIG. 6 (C) are both isosceles triangles having a base perpendicular to the flow on the upstream side. of both at d, height h _A> h _B
> H _C , the vortex generator 5D of FIG. 6 (D), and FIG. 6 (E)
Of the vortex generator 5E, isosceles triangles 5d and 5e both having a base d and a base perpendicular to the flow on the downstream side, and 0.15 to 0.3d on the downstream side of the isosceles triangles 5d and 5e. This is a composite vortex generator combining convex 5d 'and 5e' with projections on the downstream side.

FIG. 7 is a diagram for explaining the experimental results of the St number and Re number characteristics of the vortex generator shown in FIG.
The e number and the vertical axis indicate the St number.

According to the experimental results shown in FIG. 7, in the isosceles triangular vortex generators 5A, 5B and 5C, the lower one of the height h is smaller.
That is, the smaller the base angle, the larger the St number. FIG.
According to this, the St number satisfies 5C>5B> 5A. Further, the St number of the composite vortex generators 5D and 5E is larger than that of the vortex generators 5A, 5B and 5C, which are both isosceles triangles. The vortex generator 5E having a larger St than the vortex generator 5D
It turned out to be a number.

As can be seen from the results of FIGS. 6 and 7, by selecting a vortex generator having a large St number from the cross-sectional shape of the vortex generator 5, the vortex frequency f generated by the flow of the exhaust gas can be reduced. The frequency can always be higher than the pulsating pressure frequency F of the engine. As a result, it is possible to eliminate an error in pulse omission due to interference between the vortex frequency and the pulsating pressure frequency. Although the linearity is degraded by increasing the St number, it is rather convenient because the Strouhal number increases in a small flow rate region where the pulsating pressure frequency and the vortex frequency approach each other, that is, in a region where the Re number is small. In this case, by performing the instrumental difference correction by the CPU 8, a highly accurate flow rate of the exhaust gas can be obtained by the inexpensive vortex flowmeter 9.

FIG. 8 is a view for explaining an embodiment of the invention according to claims 4 to 9, wherein the flow direction is all from left to right as indicated by arrows, and the representative lengths are all d and d. Under the conditions described above, the cross-sectional shape of the vortex generator 5 is shown in FIG. 8 (A) as an isosceles triangle having a base perpendicular to the flow on the upstream side, and FIG. 8 (B) as a trapezoid having a pair of opposite sides perpendicular to the flow. 8 (C) is an isosceles triangle having a base perpendicular to the flow on the downstream side, and FIG. 8 (D).
Is a rectangle having a side perpendicular to the flow as a long side, and FIG. 8 (E) is a convex shape having a bottom side perpendicular to the flow and having a protrusion on the downstream side. It is a thing.

According to the fourth embodiment of the present invention, the vortex generator 5
Is a isosceles triangle having a base perpendicular to the flow on the upstream side as shown in FIG. In the isosceles triangle (FIG. 8A), as described in FIGS. 6 and 7, the St number increases as the base angle decreases, and the St number is such that the base angle is θ ₁ <θ ₂ <θ ₃ . In FIG. 8A, FIG.
(A) The isosceles triangle of 1 is the largest, and FIG.
In FIG.

According to the fifth embodiment of the present invention, the vortex generator 5
As shown in FIG. 8 (B), the cross-sectional shape of
It is a trapezoid with pairs of opposite sides. In this case, the St number increases as the length t in the flow direction decreases, so the St number is
In FIG. 8B in which the length is t ₁ <t ₂ <t ₃ , FIG.
(B) The trapezoid of 1 is the largest, and FIG.
(B) It becomes smaller in the order of 3.

According to the sixth embodiment of the present invention, the vortex generator 5
Is a isosceles triangle having a base perpendicular to the flow on the downstream side, as shown in FIG. 8C. In this case, since the St number increases as the base angle θ increases, the St number is the same as that in FIG. 8C where the base angle is θ ₃ > θ ₂ > θ ₁ in FIG. The equilateral triangle is the largest, and decreases in the order of FIG. 8 (C) 2 and FIG. 8 (C) 3.

According to an embodiment of the present invention, a vortex generator 5 is provided.
As shown in FIG. 8 (D), the cross-sectional shape is a rectangle whose long side is a side perpendicular to the flow. In this case, the St number increases as the length t of the short side decreases, and therefore the St number is the same as that in FIG. 8D in which the length is t ₄ <t ₅ <t ₆ in FIG.
8 is the largest, and becomes smaller in the order of FIG. 8 (D) 2 and FIG. 8 (D) 3.

According to an embodiment of the present invention, a vortex generator 5 is provided.
As shown in FIG. 8 (E), the cross-sectional shape is a convex shape having a bottom side perpendicular to the flow on the upstream side and a projection on the downstream side. In this case, the St number increases as the length h of the protrusion decreases, and the St number is such that the length is h ₁ <h ₂ <h ₃ in FIG.
In FIG. 8E, the convex shape in FIG. 8E1 is the largest, and decreases in the order of FIGS. 8E2 and 8E3.

The ninth embodiment of the present invention will be described with reference to FIG.
8 (E) is a composite type in which at least two or more of the cross-sectional shapes of the vortex generators shown in FIG. 8 (E) are installed at predetermined intervals in the flow direction, for example, as shown in FIGS. 6 (D) and 6 (E). To
The vortex generation of the compound type combining the isosceles triangle of FIG. 8 (C) and the convex shape of FIG. 8 (E) and the compound type combining the isosceles triangle of FIG. 8 (C) and the rectangle of FIG. 8 (D) The body 5 is formed. In this case, as shown in FIG. 7, the St number is larger than that of the vortex generator 5 having only an isosceles triangle.

By selecting the vortex generator 5 having a large St number from the cross-sectional shape of the vortex generator 5 shown in FIG. 8, the vortex frequency f generated by the flow of the exhaust gas is reduced by the pulsation pressure of the engine. By setting the frequency to be always higher than the frequency F, a vortex signal that does not cause pulse omission can be obtained at the engine speed N from the time of idling of the engine to the time when the accelerator is fully opened.

According to an eleventh embodiment of the present invention, as shown in FIG. 2, the vortex generator 5 has a mounting flange 5a at one end.
And inserted vertically into the flow path of the main body 3 and detachably joined by bolts 5b or the like. Similarly, the vortex detector 6
Has a mounting flange 6b on one end side, inserts the pressure receiving plate 6a into the flow path of the main body 3 in parallel to the flow, and removably joins with bolts or the like.

According to an embodiment of the present invention, as shown in FIG. 2, a purge hole 10 for injecting a compressed gas into a flow path of the main body 3 is provided on a side surface of the main body 3, A valve or the like (not shown) is connected to the hole 10.
At the time of exhaust gas measurement, the exhaust gas is prevented from flowing out.

FIG. 9 is a sectional view of a flow path of a vortex flowmeter main body for explaining an embodiment of the present invention, and FIG.
9 is a cross-sectional view of the flow path of the main body of the present invention, and FIG. 9B is a cross-sectional view of the flow path of the conventional main body. Portions that perform the same operations as those in FIG. .

In a vortex flow meter, a stable vortex is released,
In addition, in order to generate a vortex with a good SN ratio, the ratio (d / d) of the length D of the channel width of the main body 3 to the representative length d of the vortex generator 5 is required.
D) is important, and (d / D) = 0.28 is optimal when the cross section of the flow path of the main body 3 is circular. When the flow path cross section of the main body 3 is rectangular, (d / D) = 0.2 is optimal.

On the other hand, the vortex frequency f is determined by the equation (1) and the representative length d of the vortex generator 5 if the flow velocity (V) is constant.
Is inversely proportional to That is, if the St number is constant, f∝1 / d (3). Therefore, the flow rate of the main body 3 shown in FIG. 9A is smaller than that of the conventional flow path cross section of the main body 3 shown in FIG. Like a road section, H
By setting> W, d ₁ <d ₂ (4), and a higher vortex frequency f can be obtained in the flow path cross section of the main body 3 where H> W shown in FIG. 9A.

[0047]

According to the first aspect of the present invention, a pulsating pressure damping means, a vibration damping means, a rectifying means, and the like are provided from an exhaust port of an engine.
Since a vortex flowmeter having a vortex generator that constantly generates a vortex higher than the pulsation pressure frequency of the engine is connected, the pulsation pressure of exhaust gas and external vibration of the engine etc. are attenuated,
The influence of pulsating pressure and external vibration on the vortex detector is reduced, and the SN ratio is increased. Further, since the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, a stable vortex signal is detected in a flow rate range from when the engine is idling to when the accelerator is fully opened. As a result, an inexpensive and high-performance engine exhaust gas measurement system can be provided.

Advantageous Effect Corresponding to Claim 2: In the invention of claim 1, since the pulsating pressure damping means and the vibration damping means are formed as an integrated damper, the pipe length can be shortened.

Effect corresponding to claim 3: In the invention of claim 1 or claim 2, one or more rectifying means is further provided between the exhaust port of the engine and the rectifying means, so that the rectifying effect can be further improved. Can be enhanced.

Advantages Corresponding to Claim 4: Claims 1 to 3
In any one of the inventions, the cross-sectional shape of the vortex generator attached to the vortex flow meter is an isosceles triangle having a base perpendicular to the flow on the upstream side. Is set to an angle at which the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, so that a stable vortex signal can be detected in the entire flow rate range.

Advantages Corresponding to Claim 5: Claims 1 to 3
In any one of the inventions described above, the cross-sectional shape of the vortex generator attached to the vortex flowmeter is a trapezoid having a pair of opposite sides perpendicular to the flow. Since the length in the direction is set to a length at which the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, the same effect as in claim 4 can be obtained.

Advantages Corresponding to Claim 6: Claims 1 to 3
In any one of the inventions, the cross-sectional shape of the vortex generator attached to the vortex flowmeter is an isosceles triangle having a base perpendicular to the flow on the downstream side. Is set to an angle at which the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, so that the same effect as in claim 4 can be obtained.

Effect corresponding to Claim 7: Claims 1 to 3
In any one of the inventions described above, the cross-sectional shape of the vortex generator attached to the vortex flowmeter is a rectangle having a long side perpendicular to the flow, so that the relationship between the St number and the length of the short side is short. Since the side is set to a length at which the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, the same effect as in the fourth aspect can be obtained.

Advantages Corresponding to Claim 8: Claims 1 to 3
In any of the inventions described above, the cross-sectional shape of the vortex generator attached to the vortex flowmeter is a convex shape having a bottom side perpendicular to the flow on the upstream side and a protrusion on the downstream side, so that the St number and the flow of the protrusion Since the length of the projection is set to a length at which the vortex frequency is always higher than the pulsating pressure frequency of the exhaust gas, an effect equivalent to the fourth aspect can be obtained.

Advantages Corresponding to Claim 9: Claims 1 to 3
In any of the inventions described above, the vortex generator mounted on the vortex flowmeter has a cross-sectional shape of at least two of isosceles triangles, trapezoids, rectangles, or projections, and is disposed at predetermined intervals in the flow direction. Because of the composite type, S
The number t increases, and the effect of claim 4 can be further enhanced.

According to the tenth aspect, in any one of the first to ninth aspects, the cross section perpendicular to the axial direction of the flow path of the vortex flowmeter is rectangular, and the vortex generator is one side of the rectangular shape. And the side perpendicular to one side of the rectangle into which the vortex generator is inserted is defined as the long side of the rectangle, so that a high vortex frequency can be obtained.

According to the eleventh aspect, the vortex generator and the vortex detector mounted on the vortex flowmeter are detachably supported on the vortex flowmeter main body. In addition, the vortex generator and the vortex detector can be easily cleaned.

According to the twelfth aspect of the present invention, at least one purge hole is provided in the vortex flowmeter main body, so that the vortex flowmeter is provided from outside the vortex flowmeter main body. By directly performing air purging inside the main body, dirt can be washed while the vortex generator and the vortex detector are mounted on the vortex flowmeter main body.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view in the flow direction of an engine exhaust gas flow rate measuring system for describing an embodiment of the invention of claims 1 to 3;

FIG. 2 is an exploded perspective view of the vortex flowmeter 9 shown in FIG.

FIG. 3 is a diagram for explaining the relationship between the flow rate of exhaust gas and the vortex frequency.

FIG. 4 is a diagram showing a relationship among an engine speed N, a pulsating pressure frequency F of exhaust gas, and a vortex frequency f.

FIG. 5 is a diagram showing a relationship between a vortex waveform and a trigger waveform at an engine speed.

FIG. 6 is a diagram showing an example of a cross-sectional shape of the vortex generator according to the first to third aspects of the present invention.

FIG. 7 is a diagram for explaining experimental results of St number and Re number characteristics of the vortex generator shown in FIG. 6;

FIG. 8 is a diagram for explaining an embodiment of the invention according to claims 4 to 9;

FIG. 9 is a cross-sectional view of a flow path of a vortex flowmeter main body for describing an embodiment of the invention of claim 10;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inflow pipe, 2 ... Attenuator, 3 ... Vortex flowmeter main body, 4 ... Rectifier, 5 ... Vortex generator, 6 ... Vortex detector, 7 ... Converter, 8 ... C
PU, 9: vortex flow meter, 10: purge hole.

Claims (12)

[Claims] An engine exhaust gas flow rate measuring system for measuring a flow rate of an exhaust gas of an engine, wherein a pulsating pressure damping means for attenuating a pulsating pressure of the exhaust gas, and a vibration generated from the engine and transmitted to a pipe. A vortex flow meter having a vortex generator that constantly generates a vortex having a frequency higher than a pulsating pressure frequency of the engine; An exhaust gas flow measurement system for an engine, wherein a pulsating pressure attenuator, a vibration attenuator, a rectifier, and a vortex flowmeter are sequentially connected from an exhaust port of the engine. 2. The system for measuring the flow rate of exhaust gas from an engine according to claim 1, wherein said pulsating pressure damping means and said vibration damping means have an integral structure. 3. The engine according to claim 1, further comprising at least one rectification unit between the exhaust port of the engine and the rectification unit, in addition to the rectification unit. Exhaust gas flow measurement system. 4. The vortex generator mounted on the vortex flowmeter has a cross-sectional shape of an isosceles triangle having a base perpendicular to the flow on the upstream side. Engine exhaust gas flow measurement system. 5. The engine according to claim 1, wherein a cross-sectional shape of the vortex generator mounted on the vortex flowmeter is a trapezoid having a pair of opposite sides perpendicular to the flow. Exhaust gas flow measurement system. 6. The vortex generator mounted on the vortex flowmeter has a cross-sectional shape of an isosceles triangle having a base perpendicular to the flow on the downstream side. Engine exhaust gas flow measurement system. 7. The engine according to claim 1, wherein a cross-sectional shape of the vortex generator mounted on the vortex flowmeter is a rectangle having a long side perpendicular to the flow. Exhaust gas flow measurement system. 8. The vortex generator mounted on the vortex flowmeter has a cross section having a convex shape having a bottom side perpendicular to the flow on the upstream side and a projection on the downstream side. The exhaust gas flow measurement system according to any one of claims 1 to 4. 9. A vortex generator attached to the vortex flowmeter, wherein a cross-sectional shape is selected from an isosceles triangle, a trapezoid, a rectangle, and a convex shape.
The engine exhaust gas flow measurement system according to any one of claims 1 to 3, wherein the system is a composite type in which at least two or more are installed at predetermined intervals in the flow direction. 10. A cross section perpendicular to the axial direction of the flow path of the vortex flowmeter is rectangular, a vortex generator is inserted perpendicular to one side of the rectangle, and the vortex generator is perpendicular to one side of the rectangle into which the vortex generator is inserted. 10. The engine exhaust gas flow rate measurement system according to claim 1, wherein a long side is a long side of the rectangle. 11. The exhaust gas flow rate according to claim 1, wherein the vortex generator and the vortex detector mounted on the vortex flowmeter are detachably supported on the vortex flowmeter body. Measurement system. 12. The exhaust gas flow measurement system according to claim 1, wherein the vortex flowmeter has at least one purge hole in the vortex flowmeter body.