Technical Field
The present invention relates to an exhaust gas dilution device that dilutes exhaust
gas discharged from an engine, and a PM measurement system using the exhaust gas dilution
5 device.
!
Background Art
As this sort of exhaust gas dilution device, as disclosed in Patent literature 1, as a
I 10 device that measures particulate matter (PM) contained in exhaust gas discharged from an
engine, there is one that has a dilution tunnel, an exhaust gas introduction pipe for
infroducing the exhaust gas into the dilution tunnel, and an orifice plate that is provided near
an infroduction port of the exhaust gas introduction pipe and formed with an orifice.
15 Also, as disclosed in Patent literature 2, there is an exhaust gas dilution device that is,
by providing a single dilution tunnel with a first exhaust gas introduction pipe for introducing
first exhaust gas and a second exhaust gas infroduction pipe for infroducing second exhaust
gas, and switching between the exhaust gas introduction pipes by a switching valve,
configured to be able to selectively dilute and measure any of the exhaust gases from
W 20 respective engines. In addition, in the exhaust gas dilution device, on a downstream side of
an orifice that mixes the first exhaust gas and dilution air with each other, the second exhaust
gas introduction pipe is connected.
However, the second exhaust gas introduction pipe is connected on the downstream
25 side of the orifice, and therefore in the case of performing PM measurement of the first
exhaust gas, there is a problem that the first exhaust gas diluted by the orifice is retained in
2
opening space of the second exhaust gas introduction pipe or attached on an inner surface
forming the opening space to cause a measurement error in the PM measurement of the first
exhaust gas. That is, on the downstream side of a mixing part where the first exhaust gas
and the dilution gas are mixed, the exhaust gas is cooled by the dilution gas to produce PM.
5 Further, in the case of providing the dead space on the downstream side of such a mixing part,
the PM is attached in the dead space to cause the measurement error. Also, in the case of
performing PM measurement of the second exhaust gas after the end of the PM measurement
of the first exhaust gas, there is a problem that the PM that arises from the first exhaust and is
retained or attached in the opening space of the second exhaust gas introduction pipe may be
10 measured as PM contained in the second exhaust gas, and therefore a measurement error
occurs in the PM measurement of the second exhaust gas.
Citation List
Patent Literature
15
[Patent literature 1 ] JPA 2000-329661
[Patent literature 2] International publication No. WO2010/112286
Summary of Invention
A 20 Technical Problem
Therefore, the present invention is made in order to solve the above problems at
once, and a main intended object thereof is to, in exhaust gas measurement of exhaust gases
respectively discharged from a plurality of engines, reduce an error that is caused by sharing
25 a dilution tunnel and occurs in the exhaust gas measurement such as PM measurement.
3
Solution to Problem
That is, an exhaust gas dilution device according to the present invention is provided
with: a dilution tunnel that is configured to be supplied with dilution air and intended to dilute
exhaust gas from an engine; a first exhaust gas introduction path that is configured to
5 introduce first exhaust gas discharged from a first engine into the dilution tunnel; and a
second diluted exhaust gas introduction path that is configured to introduce second diluted
exhaust gas into the dilution tunnel, the second diluted exhaust gas being gas resulting from
dilution of second exhaust gas discharged from a second engine, wherein: the dilution tunnel
has a gas mixing part that is configured to mix the first exhaust gas introduced by the first
10 exhaust gas introduction path and the dilution air with each other; and the second diluted
i exhaust gas introduction path is configured to introduce the second diluted exhaust gas into
j
an upstream side of the gas mixing part in the dilution tunnel.
If so, the single dilution tunnel can be used to measure the exhaust gases respectively
15 discharged from the first engine and the second engine. This causes cost reduction and
system downsizing to be achieved because, for example, in the case of performing exhaust
gas measurement such as measurement of PM contained in the first exhaust gas and PM
contained in the second diluted exhaust gas, it is not necessary to prepare dedicated dilution
tunnels corresponding to the respective gases. Also, the second diluted exhaust gas
9 20 introduction path introduces the second diluted exhaust gas into the upstream side of the gas
mixing part in the dilution tunnel, and therefore in the first exhaust gas measurement, a PM
measurement error occurring in the case of opening the second diluted exhaust gas ;
introduction path on a downstream side of the gas mixing part can be reduced. For example,
in the PM measurement of the first exhaust gas, the measurement error caused by retention or
25 attachment of a measurement component of the first exhaust gas, such as PM, in opening
space of the second diluted exhaust gas introduction path can be reduced. Also, in the
4
.
exhaust gas measurement of the second diluted exhaust gas, such as PM measurement, the
measurement component that arises from the first exhaust gas and is retained or attached in
the opening space of the second diluted exhaust gas introduction path can be prevented from
being measured as a measurement component contained in the second diluted gasoline
5 exhaust gas, such as PM, and thereby an error in the exhaust gas measurement can be
reduced.
•
In recent years, regulations on PM contained in gasoline exhaust gas discharged
from a gasoline engine such as a direct injection engine has been tightened, and the PM
10 contained in the gasoline exhaust gas has been required to be measured. In order to suitably
cope with such a requirement on the basis of the present invention, it is desirable that the first
engine is a diesel engine, and the second engine is a gasoline engine. If so, it is not necessary
to separately prepare an exhaust gas dilution device that dilutes diesel exhaust gas discharged
from the diesel engine, and an exhaust gas dilution device that dilutes gasoline exhaust gas
15 discharged from the gasoline engine, and therefore cost reduction and system downsizing can
be achieved. Further, a problem of the retention or attachment of the PM and the like in
dead space due to the opening space of the second diluted exhaust gas introduction path
appears more notably in the exhaust gas from the diesel engine, and therefore an effect due to
not providing the dead space on the downstream side of the mixing part for the diluted
f P 20 exhaust gas from the diesel engine is large.
i
It is also possible to introduce the second diluted exhaust gas into the upstream side
of the gas mixing part by opening the second diluted exhaust gas introduction path in a
sidewall of the dilution tunnel; however, by doing so, the measurement component contained
25 in the second diluted exhaust gas, such as the PM, is attached on an inner wall surface of the
dilution tunnel, which becomes a factor of an error in the exhaust gas measurement such as
5
the PM measurement. For this reason, it is desirable that the first exhaust gas introduction
path and the second diluted exhaust gas introduction path join together in the dilution tunnel.
Note that there is common general technical knowledge that, in conventional PM
5 measurement of exhaust gas, between an introduction port of an exhaust gas introduction path
and a gas mixing part, a structure likely to be attached with PM is not provided. For this
reason, by making the first exhaust gas introduction path and the second diluted exhaust gas
introduction path join together to share an introduction port, a configuration that, between the
introduction port of the second diluted exhaust gas introduction path and the gas mixing part,
10 does not have the structure likely to be attached with PM can be realized. Accordingly, the
PM contained in the second diluted exhaust gas can be prevented from being attached on the
inner wall in the dilution tunnel, and thereby a measurement error can be reduced.
In the case of making the first exhaust gas introduction path and the second diluted
I 15 exhaust gas introduction path join together, the measurement component attached to one of
the introduction paths, such as the PM, may be included and mixed when exhaust gas is
introduced from the other introduction path into the dilution tunnel, and if so, this becomes a
factor of a measurement error. In order to solve this problem, it is desirable that the first
exhaust gas introduction path and the second diluted exhaust gas introduction path smoothly
^ 20 join together so as to face in the same direction at a joining point thereof
In order to making a configuration inside the dilution tunnel as simple as possible to
prevent the attachment of the measurement component contained in each of the exhaust gases,
such as the PM, it is desirable that the gas mixing part is formed of an orifice plate that is
25 arranged with an orifice near a gas introduction port of the first exhaust gas introduction path.
6
I!I
Also, a PM measurement system according to the present invention is provided witii:
a dilution tunnel that is configured to be supplied with dilution air and intended to dilute
exhaust gas from an engine; a first exhaust gas introduction path that is configured to
introduce first exhaust gas discharged from a first engine into the dilution tunnel; a second
5 diluted exhaust gas introduction path that is configured to introduce second diluted exhaust
gas into the dilution tunnel, the second diluted exhaust gas being gas resulting from dilution
of second exhaust gas discharged fi-om a second engine; and a diluted exhaust gas sampling
path that is provided on a downstream side in the dilution tunnel and introduces diluted
exhaust gas into a PM measurement device, wherein: the dilution tunnel has a gas mixing part
10 that is configured to mix the first exhaust gas introduced by the first exhaust gas introduction
path and the dilution air with each other; and the second diluted exhaust gas introduction path
is configured to introduce the second diluted exhaust gas into an upstream side of the gas
mixing part in the dilution tunnel.
I 15 Advantageous Effects of Invention
I
According to the present invention configured as described, the single dilution tunnel
can be used to measure the exhaust gases respectively discharged from the first engine and
the second engine, and also the second diluted exhaust gas is prevented from being
9 20 introduced into the downstream side of the gas mixing part, so that an influence of the second
diluted exhaust gas introduction path on the exhaust gas measurement of the first exhaust gas,
such as the PM measurement, can be reduced.
Brief Description of Drawings
25
i
FIG. 1 is a schematic diagram of a PM measurement system using an exhaust gas
7
dilution device of the present embodiment;
FIG. 2 is a schematic diagram illustrating a configuration near a joining point of
respective exhaust gas introduction paths in the same embodiment; and
FIG. 3 is a schematic diagram of a PM measurement system using an exhaust gas
5 dilution device of a variation.
Description of Embodiments
In the following, a PM measurement system using an exhaust gas dilution device
10 according to the present invention is described with reference to the drawings.
A PM measurement system 100 of the present embodiment is one that measures
particulate matter (PM) contained in diesel exhaust gas discharged from a diesel engine DE
or gasoline exhaust gas discharged from a gasoline engine GE.
I 15
Specifically, the PM measurement system 100 is, as illustrated in FIG. 1, provided
with: a dilution tunnel 2 that is supplied with dilution air and intended to dilute exhaust gas
from any of the various types of engines; a first exhaust gas introduction path 3 (hereinafter
referred to as a diesel exhaust gas introduction path 3) that introduces the diesel exhaust gas
9 20 (first exhaust gas) from the diesel engine DE as a first engine into the dilution tunnel 2; a
second diluted exhaust gas introduction path 4 (hereinafter referred to as a gasoline exhaust
gas introduction path 4) that dilutes the gasoline exhaust gas from the gasoline engine GE as
a second engine and introduces the diluted gasoline exhaust gas (second diluted exhaust gas)
into the dilution tunnel 2; and a diluted exhaust gas sampling path 5 that is provided on a
25 downstream side in the dilution tunnel 2 and introduces any of the diluted exhaust gases into
a PM measurement device 6.
8
The dilution tunnel 2 is one that is formed in a substantially cylindrical shape. Also,
on an upstream side in the dilution tunnel 2, a dilution air introduction path 7 for introducing
the dilution air through an air cleaning filter F is connected. Also, on the downstream side
5 in the dilution tunnel 2, a constant volume sampler (CVS) 8 including a venturi flowmeter
(e.g., a critical flow venturi type (CFV)) and a suction pump is connected. In addition, the
dilution air introduction path 7 is provided with an on/off valve 71 that opens/closes the
dilution air introduction path 7, such as a solenoid valve.
10 Also, the inside of the dilution tunnel 2 is provided with a gas mixing part 21 that
mixes the diesel exhaust gas introduced by the diesel exhaust gas introduction path 3 and the
dilution air with each other. The gas mixing part 21 is, as illustrated in FIG. 2, formed of a
cross-sectionally circular-shaped orifice plate 200 that is formed with an orifice 201 for
narrowing down the dilution air introduced from the dilution air introduction path 7. That is,
15 the gas mixing part 21 includes the orifice 201 and a downstream side region of the orifice
201. The orifice plate 200 is provided so as to halve the inside of the dilution tunnel 2.
Also, the orifice 201 causes the dilution air introduced from the dilution air introduction path
7 to form a turbulent flow, and the dilution air is mixed with the diesel exhaust gas introduced
by the diesel exhaust gas introduction path 3 or the diluted gasoline exhaust gas introduced
9 20 by the gasoline exhaust gas introduction path 4.
The diesel exhaust gas introduction path 3 is one that introduces the diesel exhaust
gas from an exhaust pipe connected to the diesel engine DE into the dilution tunnel 2, and at
one end thereof, has a diesel exhaust gas introduction port 31 that introduces the diesel
25 exhaust gas discharged fi"om the exhaust pipe of the diesel engine DE. Also, on a
downstream side of the diesel exhaust introduction path 3, an on/off valve 32 that
9
opens/closes the diesel exhaust gas introduction path 3, such as a solenoid valve, is provided.
Further, an opening (diesel gas introduction port 33) at the other end of the diesel
exhaust gas introduction path 3 in the dilution tunnel 2 is, as illustrated in FIG. 2, opened near
the orifice 201 constituting the gas mixing part 21. That is, the orifice 201 is provided so as
5 to be positioned near the introduction port 33 of the diesel exhaust gas introduction path 3.
Specifically, the orifice 201 and the introduction port 33 are coaxially arranged, and any of
the cases where the introduction port 33 is arranged near an upstream side of the orifice 201,
arranged near a downstream side of the orifice 201, and arranged in the orifice 201 is
possible.
10
\ The gasoline exhaust gas introduction path 4 is one that introduces the gasoline
exhaust gas fi"om an exhaust pipe connected to the gasoline engine GE into the dilution tunnel
2, and at one end thereof, has a gasoline exhaust gas introduction port 41 that introduces the
gasoline exhaust gas discharged from the exhaust pipe of the gasoline engine GE.
15
Also, the gasoline exhaust gas introduction path 4 is connected with a dilution air
introduction path 9 for diluting the gasoline exhaust gas introduced from the gasoline exhaust
gas introduction port 41. As described, by in the gasoline exhaust gas introduction path 4,
diluting the gasoline exhaust gas introduced into the gasoline exhaust gas introduction port 41,
9 20 moisture contained in the gasoline exhaust gas is prevented from condensing in the gasoline
exhaust gas introduction path 4. Further, on a downstream side of the gasoline exhaust gas
introduction path 4, an on/off valve 42 that opens/closes the gasoline exhaust gas introduction
path 4, such as a solenoid valve, is provided. In addition, the dilution air introduction path 9
is provided with an on/off valve 91 that opens/closes the dilution air introduction path 9, such
25 as a solenoid valve. Also, the dilution air introduction path 7 and the dilution air
introduction path 9 join together on upstream sides of the on/off valves 71 and 91, and by
10
switching between an on/off state of the on/off valve 71 and an off/on state of the on/off
valve 91, the present embodiment is configured to be able to select the introduction of the
dilution air into the dilution tunnel 2 or the introduction of the dilution air into the gasoline
exhaust gas introduction path 4.
5
Further, an opening (gasoline exhaust gas introduction port 43) at the other end of
the gasoline exhaust gas introduction path 4 in the dilution tunnel 2 is opened on the upstream i
side of the gas mixing part 21, and the present embodiment is configured to introduce the
diluted gasoline exhaust gas into the upstream side of the gas mixing par 21 of the dilution
10 tunnel 2.
Also, by switching an on/off state of the on/off valve 32 provided in the diesel
exhaust gas introduction path 3 and an off/on state of the on/off valve 42 provided in the
gasoline exhaust gas introduction path 4, the present invention is configured to alternatively
15 perform the PM measurement of the diesel exhaust gas or the PM measurement of the diluted
gasoline exhaust gas.
[
The diluted exhaust gas sampling path 5 is one that introduces the diesel exhaust gas
diluted by the dilution tunnel 2 or the diluted gasoline exhaust gas into the PM measurement
^ 20 device 6. The diluted exhaust gas sampling path 5 of the present embodiment has, at one
end thereof, a sampling port 51 that is opened on the downstream side of the gas mixing part
21 in the dilution tunnel 2, and the other end thereof is branched into two branched paths 52
and 53, which are respectively provided with filters 61 and 62 (PM measurement devices 6)
for collecting PM contained in any of the diluted exhaust gases. One 52 of the branched
25 paths forms a sample gas flow path for flowing sample gas (gas collected through the
sampling port 51) at the time of collecting the PM (at the time of measuring the exhaust gas),
11
and the other branched path 53 forms a bypass flow path for flowing the sample gas at the
time of not collecting the PM (at the time of reference measurement). Further, at
downstream ends of the respective branched paths 52 and 53, suction pumps (e.g., roots
blower pumps) 54 and 55 of which suction capabilities can be varied by rotating speed
5 control are provided.
i f
The suction pump 54 or 55 is adapted to, by being controlled by an unillustrated
control device (PID controller), make a flow rate of gas passing through the filter 61 follow a
gas flow rate in the dilution tunnel 2 with constantly keeping a constant proportional
10 relationship between the gas flow rates. That is, the gas flow rate measured by an
unillustrated flowmeter provided on a downstream side of the diluted exhaust sampling path
5 is subjected to flow rate control with having the constant proportional relationship with the
gas flow rate measured by the constant volume sampler (CVS) 8.
15 Also, as illustrated in FIG. 2, the diesel exhaust gas introduction path 3 and the
gasoline exhaust gas introduction path 4 join together in the dilution tunnel 2, and the
introduction port 33 of the diesel exhaust gas introduction path 3 and the introduction port 43
of the gasoline exhaust gas introduction path 4 are configured to be a shared opening.
^ 20 Specifically, a downstream side of a joining point MP of the respective exhaust gas
introduction paths 3 and 4 is configured to be a linearly-shaped shared fiow path. Also,
upstream sides of the joining point MP in the respective exhaust gas introduction paths 3 and
4 substantially vertically penetrate through a sidewall of the dilution tunnel 2, and are formed
in curved shapes from sidewall sides of the dilution tunnel 2 to the joining point MP,
25 respectively. Further, the two exhaust gas introduction paths 3 and 4 are configured to
smoothly join together so as to face in the same direction toward the joining point MP.
12
Specifically, one of the two exhaust gas introduction paths is configured to join the other
exhaust gas introduction path so as to face in a tangential direction of the other exhaust gas
introduction path. In doing so, in the case of making the diesel exhaust gas introduction
path 3 and the gasoline exhaust gas introduction path 4 join together, and introducing exhaust
5 gas from one of the introduction paths into the dilution tunnel 2, PM attached on an inner
surface of the other introduction path is prevented from being included and mixed. I
Also, in the present embodiment, the two exhaust gas introduction paths 3 and 4 are
configured to have symmetrical shapes in the dilution tunnel 2, respectively, and specifically
10 configured to be symmetrical to a central axis (axis passing through the opening center of the
orifice 201) of the dilution tunnel 2. In doing so, the diesel exhaust gas introduction path 3
and the gasoline exhaust gas introduction path 4 are connected to the sidewall at positions
facing to each other in the dilution tunnel 2, and therefore piping outside the dilution tunnel 2
can be facilitated.
According to the PM measurement system 100 according to the present embodiment
I configured as described, the single dilution tunnel 2 can be used to measure the exhaust gases
respectively discharged from the diesel engine DE and the gasoline engine GE. This causes
cost reduction and system downsizing to be achieved because, for example, in the case of
^k 20 measuring the PM contained in the gasoline exhaust gas and the PM contained in the diesel
exhaust gas, it is not necessary to prepare dedicated dilution tunnels corresponding to the
respective gases.
Also, the gasoline exhaust gas introduction path 4 introduces the diluted gasoline
25 exhaust gas into the upstream side of the gas mixing part 21 in the dilution tunnel 2, and
therefore in the diesel exhaust gas measurement, a PM measurement error occurring in the
13
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j
case of opening the gasoline exhaust gas introduction path 4 on the downstream side of the
gas mixing part 21 can be reduced. For example, in the PM measurement of the diesel
exhaust gas, the measurement error caused by retention or attachment of the PM of the diesel
exhaust gas in the opening space of the gasoline exhaust gas introduction path 4 can be
5 reduced. Also, in the PM measurement of the diluted gasoline exhaust gas, the PM that
arises from the diesel exhaust gas and is retained or attached in the opening space of the
gasoline exhaust gas introduction path 4 can be prevented from being measured as the PM
contained in the diluted gasoline exhaust gas, and thereby a measurement error can be
reduced.
10
The diesel exhaust gas introduction path 3 and the gasoline exhaust gas introduction
path 4 join together in the dilution tunnel 2, and therefore the introduction port 43 of the
gasoline exhaust gas introduction path 4 and the introduction port 33 of the diesel exhaust gas
introduction path 3 can be shared by each other. In doing so, the PM contained in the
15 diluted gasoline exhaust gas can be prevented from being attached on an inner wall on the
upstream side of the gas mixing part 21 inside the dilution tunnel 2, and thereby a
measurement error can be reduced. Also, by making the two exhaust gas introduction paths
3 and 4 join together in the dilution tunnel 2, a shared path part can be made as short as
possible, and therefore mutual interference between the PM and the PM respectively
9 20 contained in the various types of gases can be prevented.
Note that the present invention is not limited to the above-described embodiment. l
For example, the above-described embodiment is one in which the two exhaust gas
25 introduction paths 3 and 4 join together in the dilution tunnel 2; however, the present
invention may be configured to, in the dilution tunnel 2, open the gasoline exhaust gas
14
introduction path 4 at a position different from an opening position of tiie diesel exhaust gas
introduction path 3, or as illustrated in FIG. 3, configured to open them in the sidewall of the
dilution tunnel 2. Besides, the present invention may be configured to make the two exhaust
gas introduction paths 3 and 4 join together outside the dilution tunnel 2, and introduce a
5 combined path resulting from the joining into the dilution tunnel. |
Also, in the above-described embodiment, described is a configuration in which the
one dilution tunnel 2 is provided with the two exhaust gas introduction paths 3 and 4;
however, the present invention may be adapted to provide three or more exhaust gas
10 introduction paths. For example, the present invention may be one that is provide with two
diesel exhaust gas introduction paths 3 and one gasoline exhaust gas introduction path 4.
That is, in the case of using one dilution tunnel to dilute first exhaust gas from a plurality of
first engines, a plurality of first exhaust gas introduction paths respectively corresponding to
the plurality of first engines may be provided to connect the plurality of first exhaust gas
I 15 introduction paths to the dilution tunnel. Alternatively, in the case of using one dilution
tunnel to dilute second diluted exhaust gas from a plurality of second engines, a plurality of
second diluted exhaust gas introduction paths respectively corresponding to the plurality of
second engines may be provided to connect the plurality of second diluted exhaust gas
introduction paths to the dilution tunnel.
9 20
Further, in the above-described embodiment, described is the case where the first
engine is the diesel engine, and the second engine is the gasoline engine; however, both of the
first and second engines may be diesel engines, or gasoline engines.
25 Still further, in the above-described embodiment, the diesel exhaust gas introduction
path 3 and the gasoline exhaust gas introduction path 4 are connected to the dilution tunnel 2
15 I
I
iso
as to face to each other; however, both of the exhaust gas introduction paths 3 and 4 may
be connected to the dilution tunnel 2 from the same direction. In doing so, the two exhaust
gas introduction paths join together with facing in the same direction, and therefore when
exhaust gas is introduced from one of the introduction paths into the dilution tunnel 2, PM
5 attached on an inner surface of the other introduction path can be further prevented from
being included and mixed.
In addition, the gasoline exhaust gas introduction path (second diluted exhaust gas
introduction path) in the above-described embodiment is one that is connected with the
10 dilution air introduction path for diluting the gasoline exhaust gas, and dilutes the gasoline
exhaust gas in the second diluted exhaust gas introduction path; however, besides, the
gasoline exhaust gas introduction path may be one that receives gasoline exhaust gas diluted
by a separately provided dilution device, and introduces the diluted exhaust gas into the
dilution tunnel.
Besides, it should be appreciated that the present invention is not limited to the
above-described embodiment, but can be variously modified without departing from the
scope thereof.
% 20
16
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Reference Signs List
100: PM measurement system
DE: Diesel engine (first engine)
5 GE: Gasoline engine (second engine)
2: Dilution tunnel
21: Gas mixing part I
3: Diesel exhaust gas introduction path (first exhaust gas introduction path)
4: Gasoline exhaust gas introduction path (second diluted exhaust gas introduction path)
10 MP: Joining point
5: Diluted exhaust gas sampling path
6: PM measurement device
i
17

WE CLAIM:
1. An exhaust gas dilution device comprising:
a dilution tunnel (2) that is configured to be supplied with dilution air and intended
to dilute exhaust gas from an engine;
5 a first exhaust gas introduction path (3) that is configured to introduce first exhaust
gas discharged from a first engine (DE) into the dilution tunnel; and
a second diluted exhaust gas introduction path (4) that is configured to introduce
second diluted exhaust gas into the dilution tunnel, the second diluted exhaust gas
being gas resulting from dilution of second exhaust gas discharged from a second
10 engine (GE), wherein:
the dilution tunnel has a gas mixing part (21) that is configured to mix the first
exhaust gas introduced by the first exhaust gas introduction path and the dilution air
with each other; and
the second diluted exhaust gas introduction path (4) is configured to introduce the
15 second diluted exhaust gas into an upstream side of the gas mixing part in the
dilution tunnel.
2. The exhaust gas dilution device as claimed in claim 1, wherein the first exhaust gas
introduction path and the second diluted exhaust gas introduction path join together
f P 20 in the dilution tunnel.
3. The exhaust gas dilution device as claimed in claim 2, wherein the first exhaust gas
introduction path and the second diluted exhaust gas introduction path smoothly join
together at a joining point (MP) thereof
25
4. The exhaust gas dilution device as claimed in claim 1, wherein the gas mixing part is
18
formed of an orifice plate that is arranged with an orifice near a gas introduction
port of the first exhaust gas introduction path.
5. A PM measurement system (100) comprising:
5 a dilution tunnel (2) that is configured to be supplied with dilution air and intended
to dilute exhaust gas from an engine;
a first exhaust gas introduction path (3) that is configured to introduce first exhaust
gas discharged from a first engine into the dilution tunnel;
a second diluted exhaust gas introduction path (4) that is configured to introduce
10 second diluted exhaust gas into the dilution tunnel, the second diluted exhaust gas
being gas resulting fi-om dilution of second exhaust gas discharged from a second
engine; and
a diluted exhaust gas sampling path (5) that is provided on a downstream side in the
dilution tunnel and introduces diluted exhaust gas into a PM measurement device (6),
I 15 wherein:
the dilution tunnel has a gas mixing part (21) that is configured to mix the first
exhaust gas introduced by the first exhaust gas introduction path and the dilution air
with each other; and
the second diluted exhaust gas introduction path is configured to introduce the
V 20 second diluted exhaust gas into an upstream side of the gas mixing part in the
dilution tunnel.