JPH10227676A - Exhaust gas flow-rate measuring apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas flow-rate measuring apparatus for an internal combustion engine for accurately measuring exhaust gas flow rate by effectively mixing exhaust gas with tracing gas. SOLUTION: In the exhaust gas measuring apparatus for measuring flow rate of engine exhaust gas G based on an introducing amount of tracing gas TG and concentration of the gas TG by introducing the gas TG to an exhaust tub 3 connected to the internal combustion engine and measuring the concentration of the gas TG at a downstream side of the introducing point of the gas TG, a cylinder 15 of a polygonal sectional shape connected to an end of the tube 4 of the gas TG is provided in the tube 3, and the gas TG is injected from a hole 16 provided at the cylinder 15 into the gas G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas flow measuring device for an internal combustion engine such as an automobile engine.

[0002]

2. Description of the Related Art For example, in order to transiently characterize gas (hereinafter, referred to as exhaust gas) emitted from an automobile engine, it is necessary to measure the flow rate of exhaust gas in real time. A trace method is one of the techniques for continuously measuring the exhaust gas flow rate. In the tracing method, an inert gas that does not react with components in exhaust gas, for example, helium gas, is introduced into an exhaust pipe connected to an engine, and the concentration of the helium gas is measured by a gas sampling flow connected to the exhaust pipe. The flow rate of the exhaust gas is obtained in real time by measuring with a trace gas analyzer connected to the road and dividing the introduced amount of the helium gas by the concentration of the helium gas.

When the flow rate of exhaust gas is measured by the above-described measurement principle, it is necessary to introduce, for example, helium gas as a trace gas into an exhaust pipe connected to an engine. In addition, for example, a pipe 82 made of, for example, tetrafluoroethylene resin, which is strong against the exhaust gas G and can withstand relatively high temperature, is placed on the exhaust pipe 81 through which the exhaust gas G And a helium gas TG as a trace gas was introduced through the pipe 82.

[0004]

However, in the above-mentioned prior art, the inside diameter of the exhaust pipe 81 is about 100 mm, whereas that of the pipe 82 for introducing helium gas is about 4 mm. Since it is simply inserted into the exhaust pipe 81 so as to be orthogonal to the direction in which the exhaust gas G flows, the exhaust gas G
And the helium gas TG are not always sufficiently mixed, so that an error occurs in the helium gas concentration measurement result by the trace gas analyzer, and therefore, the measurement accuracy of the exhaust gas flow rate is not always sufficient. there were.

The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to accurately measure an exhaust gas flow rate so that the exhaust gas can be surely mixed with a trace gas. It is an object of the present invention to provide an apparatus for measuring the flow rate of exhaust gas of an internal combustion engine.

[0006]

In order to achieve the above object, according to the present invention, a trace gas is introduced into an exhaust pipe connected to an internal combustion engine, and the concentration of the trace gas is measured downstream of the trace gas introduction point. Then, in an apparatus configured to measure the flow rate of the exhaust gas of the internal combustion engine based on the introduced amount of the trace gas and the measured concentration of the trace gas, in the exhaust pipe, connected to the tip of the trace gas introduction pipe, And a cylinder having a polygonal cross section is provided,
The trace gas is blown out into the exhaust gas from the hole provided in the cylindrical body.

In the exhaust gas flow rate measuring device for an internal combustion engine having the above-described structure, an appropriate turbulent flow is generated downstream of the point where the trace gas is introduced into the exhaust pipe, and the exhaust gas and the trace gas are surely and sufficiently mixed. In addition, the exhaust gas flow rate can be accurately measured.

In the exhaust gas flow measuring device for an internal combustion engine, both ends of the cylinder may be in contact with the inner wall of the exhaust pipe, but may be separated from the inner wall by an appropriate distance. In this case, a large turbulence can be generated downstream of the trace gas introduction point while suppressing the pressure loss, and the trace gas and the exhaust gas can be efficiently mixed.

The sectional shape of the cylindrical body in the flow direction of the exhaust gas may be symmetrical, for example, an isosceles triangle. Can generate a large turbulent flow such as a vortex of a Lanchester caused by a pressure difference, so that the trace gas and the exhaust gas can be more efficiently mixed.

Further, the cross-sectional shape of the cylindrical body is not limited to the above-described triangle, but may be a quadrangle or a hexagon. In these cases, an asymmetrical shape may cause a larger turbulent flow. it can.

The internal combustion engine includes an engine of an automobile, an engine, a boiler, and the like.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. First, in FIG. 1, 1 is an automobile, and 2 is its engine. Reference numeral 3 denotes an exhaust pipe connected to a tail pipe connected to the engine 2. Reference numeral 4 denotes a trace gas introduction pipe connected to the exhaust pipe 3. A gas cylinder 5 containing pure helium gas TG as a trace gas is provided on the upstream side of the trace gas introduction pipe 4, and on the downstream side thereof, A mass flow controller 6 having both a function of measuring gas flow and a function of controlling gas flow is provided.

Reference numeral 7 denotes a gas sampling flow path connected to the exhaust pipe 3, which directly samples exhaust gas not diluted with a diluting gas such as air. Equipment and devices are connected. That is, 8 is a filter, 9 is a dehumidifier such as an electronic cooler, and 10 is a suction pump. A plurality of gas analyzers 11 are provided in the gas sampling flow path 7 on the downstream side of the suction pump 10 via branch flow paths 12 which are parallel to each other, and CO, CO ₂ , NO _X
It is configured so that the components contained in the exhaust gas, such as HC and HC, can be appropriately measured.
Is connected to the gas sampling flow path 7 via the capillary 14. The trace gas analyzer 13 uses, for example, a sector field mass spectrometer and measures the concentration of helium gas TG.

FIG. 2 and FIG. 3 show an example of a configuration for introducing a helium gas TG as a trace gas into the exhaust pipe 3. That is, FIG. 2 is a perspective view of the portion, FIG. 3 (A) is a schematic view when viewed from the direction of arrow A in FIG. 2, and FIG. 3 (B) is the direction of arrow B in FIG. FIG. FIG. 4 is a view schematically showing the state of blowing of helium gas TG.

2 and 3, reference numeral 4a denotes a tip portion of the trace gas introduction pipe 4 inserted into the exhaust pipe 3, and the tip is bent into an L shape so as to follow the flow of the exhaust gas G. I have. At the tip 4a, a tubular body 15 for blowing out trace gas having a triangular outer shape and having a gas flow path therein has its longitudinal direction orthogonal to the direction in which the exhaust gas G flows, and both ends thereof It is arranged at a distance from the inner wall of the exhaust pipe 3 as appropriate. Reference numeral 17 denotes a gap between the both ends and the inner wall of the exhaust pipe 3.

As shown in FIGS. 3B and 4, the cylindrical body 15 has an asymmetrical triangular cross section as viewed from the direction of arrow B, and one vertex 15a is located on the upstream side (exhaust gas G).
At the vertex 15a, and a plurality of holes 16 for blowing out trace gas are formed in the longitudinal direction thereof. The distal end portion 4a of the trace gas introduction pipe 4 is connected to one outer surface of the cylindrical body 15 in communication.
The cylindrical body 15 is heated by a heater (not shown), and the temperature of the cylindrical body 15 is adjusted so that the temperature difference between the exhaust pipe 3 and the exhaust gas G falls within a predetermined range.

Output signals from the mass flow controller 6, the gas analyzer 11, and the trace gas analyzer 13 are as follows:
The data is input to an arithmetic control unit such as a microcomputer (not shown).

In the device having the above structure, the exhaust gas from the engine 2 of the automobile 1 reaches the exhaust pipe 3. In response to the exhaust gas, the helium gas TG whose flow rate has been adjusted by the mass flow controller 6 reaches the cylinder 15 via the trace gas introduction pipe 4 on the upstream side of the exhaust pipe 3, and flows out from the outlet 16 of the cylinder 15. It is blown out into the exhaust pipe 3 and is introduced into the exhaust pipe 3. Note that the introduction amount at this time is measured by the mass flow controller 6 and input to the arithmetic and control unit.

In the exhaust pipe 3, a cylindrical body 15 asymmetrical with respect to the flow of the exhaust gas G is provided such that both longitudinal ends thereof do not abut against the inner wall of the exhaust pipe 3. As schematically shown in FIG. 4, turbulence occurs in the exhaust gas G on the downstream side of the cylinder 15, and the helium gas TG blown out to the exhaust pipe 3 through the blowout hole 16 opened on the upstream side of the cylinder 15 is , And is well mixed with the turbulent exhaust gas G. That is, while the helium gas TG is blown out from the blowing hole 16 provided on the upstream side of the cylindrical body 15,
5 is arranged asymmetrically in the flow of the exhaust gas G, the exhaust gas G generates a turbulent flow on the downstream side of the cylinder 15, and the small gap 1 between the cylinder 15 and the exhaust pipe 3.
The exhaust gas G passing through 7 flows toward the center of the exhaust pipe 3, and as shown in FIG. 3A, the vortex 18 is generated, whereby the exhaust gas G and the helium gas TG are sufficiently mixed. In this case, the pressure loss due to the blowing of the helium gas TG is small, and the flow rate of the helium gas TG is small, and the flow rate can be easily controlled.

A part of the exhaust gas G sufficiently mixed with the helium gas TG as described above is taken into the gas sampling channel 7 as the sample gas S. The sample gas S taken into the gas sampling channel 7 is filtered by the filter 8
, To the dehumidifying device 9 where it is dehumidified as appropriate. The sample gas S after the dehumidification process passes through the suction pump 10 and is supplied to the gas analyzer 1
1 and supplied to the trace gas analyzer 13 via the capillary 14.

Then, in the gas analyzer 11, various components contained in the sample gas S are analyzed, and the results are sent to the arithmetic and control unit. Further, in the trace gas analyzer 14, the concentration of the helium gas TG is obtained, and this concentration value is also sent to the arithmetic and control unit.

On the other hand, in the mass flow controller 6, the introduced amount of helium gas TG as a trace gas is obtained and sent to the arithmetic and control unit, so that the introduced amount of helium gas is divided by the helium gas concentration. The exhaust gas flow rate can be obtained in real time.

In the above-described embodiment, the cross-sectional shape of the cylindrical body 15 is an asymmetric triangle, and is provided so as to be asymmetric with respect to the flow of the exhaust gas G. For example, it may be an isosceles triangle, and the tubular body 15 having such a cross-sectional shape may be provided so as to be asymmetric or symmetric with respect to the flow of the exhaust gas G. Further, the position of the blowout hole 16 in the cylindrical body 15 is not limited to the upstream side of the cylindrical body 15 and may be provided at an appropriate position such as a downstream side or a side part.

In the above-described first embodiment, the cross-sectional shape of the cylindrical body 15 is triangular. However, the present invention is not limited to this, and the cylindrical body 15 may be formed in a square or hexagonal shape. Less than,
These will be described with reference to FIGS.

First, FIG. 5 shows a second embodiment. In FIG. 5A, reference numeral 19 denotes a cylinder having an appropriate length, and its cross-sectional shape is a quadrangle, more specifically, a square. Although not shown in detail on one side of the cylindrical body 19,
A plurality of blowout holes 20 are opened in the longitudinal direction. Such a cylindrical body 19 is arranged so as to be symmetrical to the flow of the exhaust gas G such that the side 20a where the blowout hole 20 is formed is located on the upstream side as shown in FIG. In this case, it is preferable that both ends of the cylindrical body 19 be kept out of contact with the inner wall of the exhaust pipe 3.

As described above, the cylindrical body 19 having a square cross section is used.
5B, turbulence occurs in the exhaust gas G on the downstream side of the cylindrical body 19 and is blown out to the exhaust pipe 3 through the blowout hole 20 opened on the upstream side of the cylindrical body 19. The helium gas TG is well mixed with the exhaust gas G in a turbulent state. That is, while the helium gas TG is blown out from the blowing holes 20 provided on the upstream side of the cylinder 19, the exhaust gas G flows downstream of the cylinder 19 by the cylinder 19 being arranged asymmetrically in the flow of the exhaust gas G. As shown in FIG. 3A, turbulence occurs on the side and exhaust gas G passing through a slight gap between the cylinder 19 and the exhaust pipe 3 flows toward the center of the exhaust pipe 3. Is generated, exhaust gas G and helium gas TG are sufficiently mixed. In this case, the pressure loss due to the blowing of the helium gas TG is small, and the flow rate of the helium gas TG is small, and the flow rate can be easily controlled.

Incidentally, also in the second embodiment, the cylinder 1
Needless to say, 9 may be arranged so as to be asymmetrical to the flow of the exhaust gas G. Further, the cross-sectional shape of the cylindrical body 19 may be a rectangle, a trapezoid, or a simple square. When the cross-sectional shape is a rectangular cylinder 19, it is preferable to arrange the cylinder 19 so as to be symmetrical to the flow of the exhaust gas G. Also, the blowout hole 2 in the cylindrical body 19
The position of 0 is not limited to the upstream side of the cylindrical body 19, and may be provided at an appropriate position such as the downstream side or the side.

FIG. 6 shows a third embodiment. In this figure, reference numeral 21 denotes a cylinder 21 having a regular hexagonal cross section. A plurality of blowout holes 22 are formed in one vertex 21a of the cylindrical body 21 in the longitudinal direction. The cylindrical body 21 configured as described above is installed in the exhaust pipe 3 such that the blowout hole 22 is located on the upstream side. The operation and effect in such a case are the same as those in the first and second embodiments, and therefore, detailed description thereof will be omitted. It is needless to say that also in the third embodiment, the cylindrical body 21 may be arranged so as to be asymmetric with respect to the flow of the exhaust gas G. Further, the cross-sectional shape of the cylindrical body 21 may be a simple hexagon. Further, the position of the blowout hole 22 in the cylindrical body 21 is not limited to the upstream side of the cylindrical body 21 and may be provided at an appropriate position such as a downstream side or a side part.

In the first to third embodiments, the sectional shapes of the cylinders 15, 19, and 21 are triangular, quadrangular, and hexagonal, respectively. No. 21 is because its manufacture is easy. In addition, the cross-sectional shape of the cylindrical body may be a polygon of seven or more heptagon, but in such a shape,
As compared with the prior art shown in FIG. 13, turbulence is more likely to occur and the helium gas TG can be sufficiently mixed with the exhaust gas G. However, it is considered that each of the above embodiments has a better mixing effect.

In each of the above embodiments, the cylinder 1
5, 19, and 21 are arranged so that a slight gap is formed between both ends in the longitudinal direction and the inner wall of the exhaust pipe 3. As shown in FIG. The portion may abut on the inner wall of the exhaust pipe 3. In this case, since the vortex of the Lanchester is hardly generated on the inner wall side of the exhaust pipe 3, the turbulence effect is slightly reduced, but the helium gas TG can be sufficiently mixed with the exhaust gas G.

Here, in each of the above embodiments, the exhaust gas G
FIGS. 8 to 12 show the results obtained by simulating the state in which the trace gas TG was mixed therein using a computer.
Shown in In the following, the inner diameter of the exhaust pipe 3 is 53 m
m, the flow rate of the exhaust gas G flowing therethrough is 2000 L / min.
It is assumed that the Reynolds number is constant. In addition, reference numerals a to i in the respective drawings indicate regions divided by the flow velocity, where a indicates the fastest, and hereafter, indicates that the speed gradually decreases.

First, FIG. 8A shows a case where a triangular prism 24 having a length of 40 mm is arranged in a state where both ends are not in contact with the inner wall of the exhaust pipe 3 as shown in FIGS. Is a simulation diagram showing a mixed state of the exhaust gas G and the trace gas TG around the triangular prism 24 in FIG.

FIG. 9 (A) shows a triangular prism 25 having a length of 53 mm as shown in FIGS. 9 (B) and 9 (C) such that both ends thereof are in contact with the inner wall of the exhaust pipe 3 and Exhaust gas G
Is a simulation diagram showing a mixed state of the exhaust gas G and the trace gas TG in the vicinity of the triangular prism 25 when arranged so as to be asymmetric with respect to the flow of the exhaust gas.

FIG. 10 (A) shows a triangular prism 26 having a length of 53 mm and an isosceles triangular cross section as shown in FIG. 10 (B), in which both ends of the triangular prism 26 are brought into contact with the inner wall of the exhaust pipe 3. FIG. 8 is a simulation diagram showing a mixed state of the exhaust gas G and the trace gas TG around the triangular prism 26 when the exhaust gas G is arranged so as to be asymmetric with respect to the flow of the exhaust gas G.

FIG. 11 (A) shows a triangular prism 27 having a length of 53 mm and a regular triangular cross section in which both ends are brought into contact with the inner wall of the exhaust pipe 3 as shown in FIG. 11 (B). FIG. 7 is a simulation diagram showing a mixed state of the exhaust gas G and the trace gas TG in the vicinity of the triangular prism 27 when arranged so as to be symmetrical to the flow of the exhaust gas G.

Further, FIG. 12A shows a case where the length is 53 m.
As shown in FIG. 3B, a square prism 28 having a square cross section of m is arranged so that both ends thereof are in contact with the inner wall of the exhaust pipe 3 and are symmetrical to the flow of the exhaust gas G. FIG. 7 is a simulation diagram showing a mixed state of exhaust gas G and trace gas TG in the vicinity of the quadrangular prism 28 when performing.

8 to 11, the outlet of the trace gas TG is provided at the vertex on the upstream side, and in FIG. 12, it is provided on the side on the upstream side. .

FIGS. 8A and 9B show flow velocity distributions when the cylindrical body 15 is arranged in a non-contact and contact state with the inner wall of the exhaust pipe 3, respectively. From the figure of FIG. 5, the cylindrical body 15 (19,
It can be seen that the arrangement of 21) in a non-contact manner promotes the mixing of the exhaust gas G and the trace gas TG. In addition,
This is presumed to be the same not only in the case where the cross-sectional shape of the cylinder is a triangle, but also in other polygons.

FIGS. 10 (A), 11 (A) and 12 (A) show that the cross-sectional shapes of the cylinders 15 and 19 in the exhaust pipe 3 are symmetric or asymmetric with respect to the flow of the exhaust gas G. These figures show the flow velocity distribution at the time of arrangement, and from these figures, it can be seen that mixing the exhaust gas G and the trace gas TG is more promoted if the cross-sectional shape is asymmetric. A cross section having a square cross section can promote the mixing more than a triangular cross section, but the pressure loss to the upstream side with respect to the flow of the exhaust gas G increases.

The present invention is not limited to the embodiments described above. For example, an inert gas other than helium gas may be used as the trace gas, but helium gas is preferred. This is because the atomic weight of helium is far from the atomic weight of the substance present in the exhaust gas G. Further, as the trace gas analyzer 13, various mass analyzers such as a quadrupole mass analyzer can be used in addition to the sector field mass analyzer.

[0042]

The present invention is embodied in the above-described embodiment and has the following effects.

In the exhaust gas flow measuring device for an internal combustion engine according to the present invention, a cylinder having a polygonal cross section is provided in an exhaust pipe through which exhaust gas flows, and a trace gas is injected into the exhaust gas from a hole provided in the cylinder. As a result, a favorable turbulent flow occurs downstream of the point at which the trace gas is introduced into the exhaust pipe, and the exhaust gas and the trace gas are reliably and sufficiently mixed. Therefore, the flow rate of the exhaust gas can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an entire configuration of an exhaust gas flow rate measuring device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a trace gas introduction part in the exhaust gas flow measuring device for the internal combustion engine.

3A is a schematic diagram when viewed from the direction of arrow A in FIG. 2, and FIG. 3B is a schematic diagram when viewed from the direction of arrow B in FIG. 2;

FIG. 4 is an operation explanatory diagram of the first embodiment.

5A and 5B show a second embodiment, in which FIG.
(B) is an operation explanatory diagram.

FIG. 6 is a sectional view of a main part showing a third embodiment.

FIG. 7 is a view showing another installation mode of the cylindrical body.

FIG. 8A is a simulation diagram showing a mixed state of exhaust gas and trace gas, and FIGS. 8B and 8C are diagrams schematically showing an arrangement state of triangular prisms.

9A is a simulation diagram showing a mixed state of exhaust gas and trace gas, and FIGS. 9B and 9C are diagrams schematically showing an arrangement state of triangular prisms.

10A is a simulation diagram showing a mixed state of an exhaust gas and a trace gas, and FIG. 10B is a diagram schematically showing an arrangement state of a triangular prism.

11A is a simulation diagram showing a mixed state of exhaust gas and trace gas, and FIG. 11B is a diagram schematically showing an arrangement state of triangular prisms.

FIG. 12A is a simulation diagram showing a mixed state of exhaust gas and trace gas, and FIG. 12B is a diagram schematically showing an arrangement state of square pillars.

FIG. 13 is a diagram for explaining a conventional technique.

[Explanation of symbols]

2 ... Engine, 3 ... Exhaust pipe, 4 ... Trace gas introduction pipe,
15, 19, 21, 23 ... cylindrical body, 16, 20, 22 ... blowing hole, G ... exhaust gas, TG ... trace gas.

Claims (4)

[Claims] 1. A trace gas is introduced into an exhaust pipe connected to an internal combustion engine, and the concentration of the trace gas is measured downstream of an introduction point of the trace gas. In the apparatus for measuring the flow rate of the exhaust gas of the internal combustion engine based on the following, in the exhaust pipe, a cylindrical body having a polygonal cross-section connected to the tip of the trace gas introduction pipe is provided, and An exhaust gas flow measuring device for an internal combustion engine, wherein a trace gas is ejected into exhaust gas from a hole provided in a body. 2. The exhaust gas flow measuring device for an internal combustion engine according to claim 1, wherein both ends of the cylindrical body are separated from an inner wall of the exhaust pipe. 3. The exhaust gas flow measurement device for an internal combustion engine according to claim 1, wherein the cross-sectional shape of the cylinder in the flow direction of the exhaust gas is asymmetric. 4. The exhaust gas flow measuring device for an internal combustion engine according to claim 1, wherein the cross-sectional shape of the cylinder is any one of a triangle, a quadrangle, and a hexagon.