U.S. patent application number 12/203614 was filed with the patent office on 2009-01-01 for exhaust gas analyzer.
This patent application is currently assigned to HORIBA, LTD.. Invention is credited to Tatsuki Kumagai, Takeshi Kusaka, Kaoru Okada, Akihiro Taniguchi.
Application Number | 20090003125 12/203614 |
Document ID | / |
Family ID | 36129751 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090003125 |
Kind Code |
A1 |
Kusaka; Takeshi ; et
al. |
January 1, 2009 |
EXHAUST GAS ANALYZER
Abstract
An SOF measuring system that can continuously measure SOF and a
soot measuring system that can continuously measure soot are
connected with an exhaust gas line. The soot measuring system
comprises a diluter that selectively dilutes either one of the
exhaust gas and standard gas whose hydrocarbon concentration is
known with diluent gas and extrudes it. A dilution ratio adjusting
device can adjust a dilution ratio of the diluter. A soot detector
continuously detects soot in the exhaust gas or the standard gas
diluted by the diluter. The SOF measuring system can be connected
with the diluter so that an exhaust gas analyzer can measure the
hydrocarbon concentration in the standard gas diluted by the
diluter.
Inventors: |
Kusaka; Takeshi; (Kyoto,
JP) ; Taniguchi; Akihiro; (Kyoto, JP) ; Okada;
Kaoru; (Kyoto, JP) ; Kumagai; Tatsuki; (Kyoto,
JP) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER, TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
HORIBA, LTD.
Kyoto
JP
|
Family ID: |
36129751 |
Appl. No.: |
12/203614 |
Filed: |
September 3, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11288531 |
Nov 29, 2005 |
7434449 |
|
|
12203614 |
|
|
|
|
Current U.S.
Class: |
366/160.1 ;
366/142; 366/163.1 |
Current CPC
Class: |
G01N 2001/2264 20130101;
G01N 33/0018 20130101; G01N 2001/387 20130101; G01N 1/2252
20130101; G01N 33/0022 20130101 |
Class at
Publication: |
366/160.1 ;
366/142; 366/163.1 |
International
Class: |
B01F 5/00 20060101
B01F005/00; B01F 3/02 20060101 B01F003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2004 |
JP |
2004-346236 |
Nov 30, 2004 |
JP |
2004-347018 |
Claims
1. A mixing system comprising: a mixer wherein a narrow part whose
flow path diameter is narrowed and a diffusible part whose flow
path diameter is extended are serially arranged on an internal main
path through which mixing gas passes so as to form a
negative-pressure area that is negative-pressured because the
mixing gas is accelerated and that sucks mixed gas through a
communicating path communicating with the negative-pressure area
and mixes the mixed gas with the mixing gas and then extrudes it;
and a mixing ratio adjusting device that changes a flow amount of
the mixing gas introduced into the mixer within a range where a
flow amount of the mixed gas sucked by the mixer is kept generally
constant by a predetermined operation from outside.
2. The mixing system of claim 1, wherein a gas component detector
is connected with a gas extruding port of the mixer and can
continuously detect a component of the mixed gas.
3. The mixing system of claim 1, wherein the mixing ratio adjusting
device comprises a pressure regulator arranged on a mixing gas line
through which the mixing gas flows, a flow rate of the mixing gas
introduced into the mixer from the mixing gas line is changed by an
operation to adjust pressure of the pressure regulator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
11/288,531, filed Nov. 29, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to an exhaust gas analyzer used for
continuously measuring particulate matters (PM) included in exhaust
gas of a diesel engine of, for example, a vehicle.
[0004] 2. Background Art
[0005] Minute particulate matters (PM) that might cause an adverse
effect on the environment or human health are contained in exhaust
gas of an internal combustion engine such as a diesel engine, and
soot and soluble organic fraction (SOF) or the like are mixed in
the particulate matters.
[0006] In order to improve the internal combustion engine so as to
reduce the particulate matters, it is necessary to measure the PM
emissions accurately. According to a method for measuring exhaust
gas that is publicly specified by the requirement of current laws
and regulations, it is specified that the PM is collected by a
filter and the collected PM is weighted on a microbalance.
[0007] However, since it is impossible for this method to collect
the generating PM dynamically, there is a demand for a simple
measurement instrument that is capable of a real-time continuous PM
measurement in a step of research and development of an internal
combustion engine. Furthermore, recently since the PM emission is
considerably decreasing due to improvement of the internal
combustion engine, a demand for measuring a minute amount of PM
emissions has been increasing in addition to the continuous
measurement.
[0008] Regarding SOF, a method has been developed that can
continuously and accurately measure concentration of liquefied or
solidified particulate hydrocarbon (SOF) in exhaust gas at a
certain reference temperature (47.degree. C..+-.50.degree. C.) by
the use of a detector high-sensitive to hydrocarbon such as a flame
ionization detector (FID).
[0009] Regarding soot, the inventors have been developing a
high-sensitive soot detector that can perform continuous
measurement by making use of a diffusion charge detecting
method.
[0010] This kind of a soot detector requires that the exhaust gas
be diluted to concentration appropriate to the exhaust gas
measurement because it is high sensitive, however, there are the
following problems in diluting the exhaust gas.
[0011] First, it is required to grasp a dilution ratio in order to
calculate the concentration of soot in the original exhaust gas
based on the concentration of soot in the measured diluted exhaust
gas.
[0012] However, in order to obtain the dilution ratio if the soot
detector has an arrangement wherein a flow of the exhaust gas prior
to dilution and a flow of the exhaust gas after dilution are
measured respectively by the use of a venturi meter and the
dilution ratio is calculated based on the flow ratios, the soot
detector becomes large and costly.
[0013] Secondly, it is preferable that the dilution ratio by the
diluter can be changed with ease because the concentration of soot
in the exhaust gas is affected to change by a variety or a state of
the internal combustion engine.
[0014] However, if the exhaust gas as being sample gas or the
diluent gas is forcefully fed or sucked by the use of, for example,
a rotary pump in order for dilution, a bad influence might be
exerted upon soot measurement such that an unexpected portion is
clogged with soot because the fluid path inside the pump is
complicated. In addition, the rotary pump is not suitable for
accurate soot measurement because of pulsation generating in the
diluted exhaust gas.
[0015] On the contrary, an ejector that conducts liquid transfer by
making use of an involute action of fluid blowing out due to
bounded jet has a simple flow path and there is no pulsation
generating. Then the ejector can be used as a diluter that is very
preferable for this kind of measurement.
[0016] However, generally it is considered that the ejector can not
change a dilution ratio arbitrarily (if a lot of diluent gas is
flowed, pressure in a nozzle diffuser part decreases and the flow
volume of the sample gas increases by just this much and
consequently the dilution ratio does not change significantly), the
ejector has a problem with this point. Conversely, the ejector is
often used in a case that the dilution ratio is to be kept to some
extent or in a case that the dilution ratio is not cared at all
(for example, a pump).
[0017] As mentioned, the ejector has a merit that the flow path is
simple and free from pulsation, however, it is considered that it
has a demerit that the dilution ratio can not be adjusted easily
when used as a diluter. As a result, it is difficult to use the
ejector for not only soot measurement but also other use such as
the dilution ratio or the mixing ratio is required to be
adjusted.
SUMMARY OF THE INVENTION
[0018] The present claimed invention intends to solve the
above-mentioned problems concerning dilution in measuring the
exhaust gas, more concretely, desired objects are mainly (1) to
make it possible to obtain a dilution ratio necessary for soot
concentration measurement with a simple and low-cost arrangement by
making use of the SOF measuring system with focusing attention on
that both concentration of SOF and concentration of soot are
measured in measuring diluted particulate matters, (2) to provide
an exhaust gas analyzer that can easily change and adjust a
dilution ratio in case of diluting the exhaust gas conducted at a
time of soot measurement and to provide a superior mixing system
that can be used broadly for diluting and mixing gas. It is not
until the inventor of the present claimed invention found out that
there was an area where flow of sample gas almost never changed
even though flow of the dilution gas was changed as a result of
keen examination that the problem (2) is solved.
[0019] First, regarding the problem (1), an exhaust gas analyzer in
accordance with this present claimed invention comprises the
following requirement.
I. An SOF measuring system that can continuously measure
concentration of SOF in exhaust gas and a soot measuring system
that can continuously measure concentration of soot in the exhaust
gas are connected with an exhaust gas line through which a part or
all of the exhaust gas discharged from an internal combustion
engine flows. II. The soot measuring system comprises [0020] a) a
diluter that selectively dilutes either one of the exhaust gas and
standard gas whose hydrocarbon concentration is known with diluent
gas and extrudes it, [0021] b) a dilution ratio adjusting device
that can adjust a dilution ratio of the diluter, and [0022] c) a
soot detector that detects soot in the exhaust gas or the standard
gas diluted by the diluter. III. The SOF measuring system can
measure hydrocarbon concentration in the standard gas diluted by
the diluter with an arrangement that the SOF measuring system can
be connected with the diluter, and the dilution ratio of the
diluter at this state can be calculated based on the hydrocarbon
concentration in the standard gas after dilution when the dilution
ratio adjusting device is operated by a certain amount.
[0023] In accordance with this arrangement, it is possible to
obtain the dilution ratio of the diluter at a time of soot
measurement by the use of the standard gas at a time prior to or
after soot measurement and to calculate the concentration of soot
in the exhaust gas prior to dilution based on the obtained dilution
ratio and the concentration of soot in the diluted exhaust gas
detected by the soot detector with an arrangement of a simple flow
path wherein the piping is bifurcated from the diluter to be
connected with the existing SOF measuring system, the piping to
connect the standard gas source is connected with the diluter, or
the switch valves are arranged on the piping.
[0024] The diluter might be clogged with soot if a fluid path
inside of the diluter has a complicated arrangement because soot
flows in the diluter. In addition, if there is pulsation generating
in the flow at a time of dilution, the pulsation might be a cause
of an error of measurement by the soot detector. Then in order to
make the diluter that is free from pulsation at a time of dilution
with a simple arrangement, it is preferable that the diluter
comprises a narrow part whose flow path diameter is narrowed and a
diffusible part whose flow path diameter is extended and that is
serially arranged to the narrow part, the diluent gas is
accelerated to be negative-pressured by passing the diluent gas
through the narrow part and the diffusible part, and the exhaust
gas or the standard gas is sucked because the diluent gas is
negative-pressured so that the exhaust gas or the standard gas is
mixed with the diluent gas. It would be further more preferable
from a viewpoint of mixing if a diffusible part is serially
arranged downstream of the narrow part.
[0025] As a concrete embodiment of the dilution ratio adjusting
device represented is a pressure regulator that adjusts pressure of
the diluent gas introduced into the diluter.
[0026] As a soot detector that can high-sensitively and
continuously measure soot represented is the soot detector
comprising an electric charge imparting part that imparts electric
charge to soot and an electric charge measuring part that measures
a quantity of electric charge of soot.
[0027] As the SOF measuring system suitable for soot measurement in
accordance with this invention represented is the SOF measuring
system comprising a bifurcated part that bifurcates the introduced
exhaust gas, a particle component removing line that sets one of
the bifurcated exhaust gas at a measurement reference temperature
for SOF measurement and removes particle component in the exhaust
gas kept at the measurement reference temperature, a passing line
that passes other bifurcated exhaust gas, and hydrocarbon
concentration detectors each of which continuously detects
hydrocarbon concentration in the exhaust gas sent out from the
particle component removing line and the passing line respectively,
and the SOF measuring system is so arranged that the SOF
concentration in the exhaust gas can be calculated based on a
difference between the hydrocarbon concentration detected by one of
the hydrocarbon concentration detectors and the hydrocarbon
concentration detected by the other hydrocarbon concentration
detector. The term here "particle component" is mainly hydrocarbon
particle liquefied or solidified in gas.
[0028] The hydrocarbon concentration detector is especially
preferably a hydrogen flame ionization detector. In case that the
SOF measuring system is arranged by the use of the hydrogen flame
ionization detector, soot is detected in a spike-like peak state,
if an output from the hydrogen flame ionization detector locating
at a side of a passing line is graphed. As a result, it is
possible, for example, to verify the concentration of soot measured
by the soot measuring system.
[0029] In order to measure the concentration of soot in the exhaust
gas by making use of the exhaust gas analyzer in accordance with
this invention, it is preferable that the hydrocarbon concentration
of the diluted standard gas is measured by the SOF measuring
system, the dilution ratio of the diluter is calculated based on a
ratio of the hydrocarbon concentration of the diluted standard gas
to the hydrocarbon concentration of the standard gas prior to
dilution, a correlation between the dilution ratio and an operated
amount is obtained based on the operated amount of the dilution
ratio adjusting device at that time, the dilution ratio is adjusted
so as to become a desired value at a time of soot measurement by
operating the dilution ratio adjusting device by the operated
amount obtained from the correlation, or the dilution ratio is
obtained based on the operated amount of the dilution ratio
adjusting device set at a time of soot measurement and the
correlation, and the concentration of soot in the exhaust gas is
calculated based on the dilution ratio and the measured result by
the soot detector.
[0030] In accordance with this invention, it is possible to obtain
the dilution ratio of the exhaust gas necessary for measuring the
concentration of soot accurately just with the simple flow path by
making use of the SOF measuring system together with the soot
measuring system in case of measuring the particulate matter.
[0031] Next, regarding the problem (2), the exhaust gas analyzer in
accordance with the present claimed invention is so arranged that a
soot measuring system that can measure soot is connected with an
exhaust gas line through which a part or all of exhaust gas
discharged from an internal combustion engine flows, and
characterized by that the soot measuring system comprises a diluter
that dilutes the exhaust gas with diluent gas and extrudes it, a
dilution ratio adjusting device that can adjust the dilution ratio
of the diluter, and a soot detector that detects soot in the
exhaust gas diluted by the diluter, wherein the diluter is so
arranged that a narrow part whose flow path diameter is narrowed
and a diffusible part whose flow path diameter is extended are
serially arranged on an internal main path through which the
diluent gas passes so as to form a negative-pressure area that is
negative-pressured because the diluent gas is accelerated, and the
diluter sucks the exhaust gas through a communicating path
communicating with the negative-pressure area, mixes the exhaust
gas with the diluent gas and then extrudes it, and the dilution
ratio adjusting device changes a flow amount of the diluent gas
introduced into the diluter within a range where a flow amount of
the exhaust gas sucked by the diluter is kept generally constant by
a predetermined operation from outside.
[0032] In accordance with this arrangement, since the dilution
ratio can be easily adjusted by the use of the dilution system so
that concentration of varieties of exhaust gas becomes appropriate
for the soot detection, it is possible to measure the concentration
of soot by the use of the high-precision soot detector. In
addition, a possibility that the fluid path is clogged with soot
can be avoided as much as possible because of a merit of the
diluter of this type, namely the simple fluid path. Furthermore,
the diluted exhaust gas can be sent out to the soot detector in a
stable state without fail because of a merit that the diluter has
no pulsation that prevents the accurate concentration
measurement.
[0033] As a soot detector whose effect can especially be
significant when the present claimed invention is applied
represented is the soot detector comprising an electric charge
imparting part that imparts electric charge to soot and an electric
charge measuring part that measures electric charge of soot.
[0034] In order to simultaneously detect SOF as well as soot
contained in the exhaust gas, it is preferable that an SOF
measuring system that can measure concentration of SOF is further
connected with the exhaust gas line. As the SOF measuring system in
this case, it is preferable that the SOF measuring system comprises
a bifurcated part that bifurcates the introduced exhaust gas, a
particle component removing line that sets one of the bifurcated
exhaust gas at a measurement reference temperature and removes
particle component in the exhaust gas kept at the measurement
reference temperature, a passing line that passes other bifurcated
exhaust gas, and hydrocarbon concentration detectors each of which
continuously detects hydrocarbon concentration in the exhaust gas
sent out from the particle component removing line and the passing
line respectively, and the SOF is so arranged that the SOF
concentration in the exhaust gas can be calculated based on a
difference between the hydrocarbon concentration detected by one of
the hydrocarbon concentration detectors and the hydrocarbon
concentration detected by the other hydrocarbon concentration
detector.
[0035] The term here "particle component" is mainly hydrocarbon
particle liquefied or solidified in gas.
[0036] The hydrocarbon concentration detector is especially
preferably a hydrogen flame ionization detector. In case that the
SOF measuring system is arranged by the use of the hydrogen flame
ionization detector, soot is detected in a spike-like peak state,
if an output from the hydrogen flame ionization detector locating
at a side of a passing line is graphed. As a result, it is
possible, for example, to verify the concentration of soot measured
by the soot measuring system and to set up a standard of an optimum
dilution ratio based on its result.
[0037] Since an object to be measured by the soot detector is the
diluted exhaust gas, it is necessary to grasp a dilution ratio
finally in order to measure the concentration of soot in the
exhaust gas.
[0038] Then in order to make it possible to obtain the dilution
ratio accurately with a simple arrangement by making use of the SOF
measuring system it is preferable that the diluter is arranged to
selectively introduce either one of the exhaust gas and standard
gas whose hydrocarbon concentration is known so that the selected
gas can be diluted, the SOF measuring system can measure
concentration of hydrocarbon in the standard gas diluted by the
diluter with an arrangement that the SOF measuring system can be
connected with the diluter, and the dilution ratio of the diluter
at this state can be calculated based on the concentration of
hydrocarbon in the standard gas after dilution when the dilution
ratio adjusting device is operated by a certain amount.
[0039] In addition, the present claimed invention can be applied
broadly as a gas mixing system including diluting gas without being
limited to the soot measurement. More specifically, the mixing
system in accordance with the present claimed invention comprises a
mixer where a narrow part whose flow path diameter is narrowed and
a diffusible part whose flow path diameter is extended are serially
arranged on an internal main path through which mixing gas as being
gas to mix passes so as to form a negative-pressure area that is
negative-pressured because the mixing gas is accelerated, and the
mixing system sucks mixed gas as being gas to be mixed through a
communicating path communicating with the negative-pressure area,
mixes the mixed gas with the mixing gas and then extrudes it, and a
mixing ratio adjusting device that changes a flow amount of the
mixing gas introduced into the mixer within a range where a flow
amount of the mixed gas sucked by the mixer is kept generally
constant by a predetermined operation from outside.
[0040] In accordance with the mixing system, it is possible to
adjust the mixing ratio easily by the use of the mixing ratio
adjusting device in addition to mix the mixed gas with the mixing
gas in a stable state because the flow path of the mixer is simple
and free from pulsation.
[0041] In order to make this effect further more remarkably, it is
preferable to further comprise a gas component detector that is
connected with a gas extruding port of the mixer and that can
continuously detect a component of the mixed gas.
[0042] As a concrete embodiment of the mixing ratio adjusting
device represented is the mixing ratio adjusting device comprising
a pressure regulator arranged on a mixing gas line through which
the mixing gas flows, and a flow rate of the mixing gas introduced
into the mixer from the mixing gas line is changed by an operation
to adjust the pressure of the pressure regulator.
[0043] In case of using this mixing system as the diluting system,
the diluent gas corresponds to the mixing gas, the exhaust gas
corresponds to the mixed gas, the diluter corresponds to the mixer,
the dilution ratio adjusting device corresponds to the mixing ratio
adjusting device, and the gas component detector corresponds to the
soot detector.
[0044] As mentioned above, in accordance with this invention, it is
possible to change and adjust the dilution (mixing) ratio easily
and to stabilize quality of the diluted (mixed) gas without
pulsation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is an overall fluid circuit diagram of an exhaust gas
analyzer in accordance with one embodiment of the present claimed
invention.
[0046] FIG. 2 is a cross-sectional view showing an internal
structure of a diluter in accordance with this embodiment.
[0047] FIG. 3 is a cross-sectional view of an enlarged portion
mainly showing a nozzle, a diffuser and an orifice of the diluter
in accordance with this embodiment.
[0048] FIG. 4 is a graph showing a characteristic of the diluter in
accordance with this embodiment.
[0049] FIG. 5 is a pattern diagram of a soot detector in accordance
with this embodiment.
[0050] FIG. 6 is a flow chart showing a method for measuring soot
by making use of the exhaust gas analyzer in accordance with this
embodiment.
[0051] FIG. 7 is a flow chart showing a method for measuring soot
by making use of the exhaust gas analyzer in accordance with this
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] An exhaust gas analyzer in accordance with one embodiment of
the present claimed invention will be described in detail with
reference to the accompanying drawings.
(1) Overall Configuration of the Exhaust Gas Analyzer
[0053] The exhaust gas analyzer 1 in accordance with this
embodiment is to measure mass concentration of SOF (soluble organic
fraction) and soot contained in exhaust gas of a diesel engine (not
shown in drawings) as being an internal combustion engine and, as
shown in FIG. 1, comprises an SOF measuring system 2 that can
continuously measure mass concentration of SOF and a soot measuring
system 3 that can continuously measure mass concentration of soot,
each of which is connected in parallel with an exhaust gas line
(not shown in drawings) to which a part or all of the exhaust gas
is discharged from the diesel engine.
(2) SOF Measuring System
[0054] First, the SOF measuring 2 system will be explained.
[0055] The SOF measuring system 2 comprises, as shown in FIG. 1, a
bifurcated part 21 that bifurcates the exhaust gas introduced from
the exhaust gas line, a passing line 22 and a particle composition
removal line 23 into each of which the exhaust gas bifurcated by
the bifurcated part 21 is introduced respectively, and hydrogen
flame ionization detectors 24a, 24b each of which is connected with
each of the passing line 22 and the particle composition removal
line 23 respectively through pumps Pa, Pb.
[0056] The bifurcated part 21 is formed by making use of a manifold
block 25 having a fluid path bifurcating internally, and the
exhaust gas line is connected with a gas introducing port PT1 as
being an introducing port of the manifold block 25 through a
temperature control pipe L such as a hot hose pipe heated to a
predetermined temperature (approximate 191.degree. C.) or a
particulate matter removal filter F. A temperature controller H1
such as a heater that can control temperature is mounted on the
manifold block 25 and the manifold 25 is kept at, for example, the
predetermined temperature (approximate 191.degree. C.).
[0057] The particle composition removal line 23 sets a temperature
of the exhaust gas flowing internally at 47.degree. C..+-.5.degree.
C. as a measurement standard temperature ordained by the 2007 EPA
regulation, removes hydrocarbon (SOF) that liquidized or solidified
at this temperature and extrudes the exhaust gas after the
hydrocarbon is removed to the hydrogen flame ionization detector
24b.
[0058] More concretely, the particle composition removal line 23 is
connected with the gas introducing port PT1 through the manifold
block 25, and comprises a first temperature control pipe L1 heated
to the measurement standard temperature, a filter F1 connected with
a terminal of the first temperature control pipe L1, and a second
temperature control pipe L2 that introduces the gas passing the
filter F1 into the hydrogen flame ionization detector 24b. The
second temperature control pipe L2 is heated to, for example, the
predetermined temperature (approximate 191.degree. C.).
[0059] The passing line 22 extrudes the exhaust gas heated to the
predetermined temperature higher than the measurement standard
temperature, more concretely 191.degree. C. directly to the
hydrogen flame ionization detector 24a, and comprises a third
temperature control pipe L3 connected with the gas introducing port
PT1 through the manifold block 25. The third temperature control
pipe L3 is heated to the predetermined temperature (approximate
191.degree. C.) and connected with the hydrogen flame ionization
detector 24a.
[0060] The hydrogen flame ionization detector 24a, 24b is to
continuously and real-time detect mass concentration of hydrocarbon
contained in sample gas (the exhaust gas in the above case) by
flowing the sample gas. The hydrogen flame ionization detector 24a,
24b ionizes the hydrocarbon in the sample gas by passing the sample
gas (the exhaust gas in this case) through the hydrogen flame and
detects and outputs its ionic current. An output value of the
detecting signal shows the mass concentration of hydrocarbon.
[0061] In accordance with this arrangement, since a base line value
of the detecting signal by the hydrogen flame ionization detector
24a connected with the passing line 22 shows the mass concentration
of hydrocarbon in a vaporized condition at the predetermined
temperature (191.degree. C.) and a base line value of the detecting
signal by the hydrogen flame ionization detector 24b connected with
the particle composition removal line 23 shows mass concentration
of vaporized hydrocarbon at the measurement standard temperature
(47.degree. C..+-.5.degree. C.) is possible to measure the mass
concentration of hydrocarbon condensed from the gaseous body to the
liquid body or to the solid body between (47.degree.
C..+-.5.degree. C.) and 191.degree. C., namely the mass
concentration of SOF in the exhaust gas by obtaining a difference
between the values of the detecting signal by each of the hydrogen
flame ionization detectors 24a, 24b.
[0062] In this embodiment, an information processing unit, not
shown in drawings, receives the hydrocarbon detecting signals from
the hydrogen flame ionization detectors 24a, 24b respectively, and
calculates the mass concentration of SOF by obtaining a difference
between the values shown by the hydrocarbon detecting signals and
outputs the mass concentration of SOF to a display or the like.
(3) Soot Measuring System
[0063] Next, the soot measuring system 3 will be explained.
[0064] The soot measuring system 3 comprises, as shown in FIG. 1, a
diluting system 4A that dilutes the exhaust gas with air as being
diluent gas and sends it out and a soot detector 5 that detects
mass concentration of soot in the diluted gas.
[0065] The diluting system 4A comprises, as shown in FIG. 1 through
FIG. 3, a diluter 4 and a pressure regulator 7 as being a dilution
ratio adjusting device.
[0066] The diluter 4 is an ejector-type, whose detail is shown in
FIG. 2 and FIG. 3, wherein a nozzle 42 as being a narrow part whose
flow path diameter is narrowed along a direction of a gas flow and
a diffuser 43 as being a diffusible part whose flow path diameter
is extended are arranged in this order serially on an internal main
path 41 through which the diluent gas flows so as to form a
negative-pressure area 4S that is negative-pressurized because the
diluent gas is accelerated, and the sample gas is sucked through a
communicating path 44 communicating to the negative-pressure area
4S, mixed with the diluent gas and then sent out. The nozzle is
used as the narrow part and the diffuser is used as the diffusible
part in this embodiment, however, various substitutes such as an
orifice or a venturi tube may be used.
[0067] More specifically, the diluter 4 mainly comprises a piping
block body 4a having the communicating path 44 communicating to the
main path 41 and the negative-pressure area 4S, a nozzle member 42a
that forms the nozzle 42 by being inserted into the main path 41, a
diffuser member 43a that forms the diffuser 43 by being inserted
into the main path 41, an inlet port PT2 as being an inlet of the
main path 41, an outlet port PT3 as being an outlet of the main
path 41, a sample gas introducing port PT4 as being an inlet of the
communicating path 44, and joints for coupling C2, C3, C4 arranged
on the inlet port PT2, the outlet port PT3 and the sample gas
introducing port PT4 respectively.
[0068] A temperature controller H2 such as a heater that can adjust
temperature is mounted on the piping block body 4a and the diluter
4 is heated to the predetermined temperature (approximate
191.degree. C.). This is to volatize SOF or the like (especially
SOF that attaches to soot) contained in the exhaust gas so as to
prevent an adverse effect on soot measurement by a soot detector 5,
to be described later. Since the soot detector 5 is a type
incapable of introducing high-temperature gas, the temperature of
the diluted exhaust gas is lowered during passing through a piping
L4 from the outlet port PT3 of the diluter 4 to the soot detector
5. SOF that has once vaporized will never be separated out again as
a particle that has influence on the measurement because SOF is
diluted even though the temperature of the diluted exhaust gas is
lowered.
[0069] In addition, a portion to be directly connected with the
inlet port PT2 of a diluent gas line 6 is heated to the
predetermined temperature (approximate 191.degree. C.) by the use
of a fourth temperature control pipe L5 so as to stabilize air flow
to be supplied.
[0070] Furthermore, as shown in FIG. 1, the diluent gas line 6
through which the diluent gas passes is connected with the inlet
port PT2 so as to introduce air as being the diluent gas, and the
exhaust gas line is connected with the sample gas introducing port
PT4. In addition, the soot detector 5 is connected with the outlet
port PT3 through the piping L4 so that the diluted gas can be sent
out to the soot detector 5.
[0071] In addition, an orifice ring 44a as being a flow limit
member is exchangeably mounted, as shown in FIG. 3, at least on the
communicating path 44 of the diluter 4 locating in a former
stage.
[0072] A diluent gas source (not shown in drawings) such as a
compressor or a steel bottle is connected with a leading end of the
diluent gas line 6 and the pressure regulator 7 as being a dilution
ratio adjusting device is arranged on the diluent gas line 6 so
that the dilution ratio can be adjusted by controlling pressure of
the air flowing into the inlet port PT2.
[0073] The pressure regulator 7 is arranged on the diluent gas line
6 and controls the pressure of the air flowing into the inlet port
PT2 of the diluter 4 so as to control its air flow.
[0074] However, generally it is not possible for a diluter of
ejector-type to change a dilution ratio arbitrarily. This is based
on a fact that the pressure in the negative-area 4S decreases if a
lot of diluent gas (for example, air) is flowed and therefore the
flow volume of the sample gas increases by just this much. As a
result of this, the dilution ratio does not fluctuate
significantly.
[0075] Then in this embodiment, as shown in FIG. 4, an operation
range of the pressure regulator 7, namely a pressure adjustable
range is restricted to a range where the sucked flow of the sample
gas in the diluter 4 is kept generally constant due to pressure
adjustment even if the flow of the diluent gas introduced into the
diluter 4 changes. More concretely, a range of the air pressure is
between 300 kPa through 500 kPa. It is a matter of course that this
range depends on a shape or a size of the nozzle or the diffuser,
or a diameter of the orifice, however, it is not until this range
is used that the pressure regulator 7 acts as the dilution ratio
adjusting device and the dilution ratio can be changed by the
operation of the pressure setting.
[0076] In this embodiment, in order to broaden a range to adjust
the dilution ratio, the diluters 4 are connected serially in plural
(two) stages. More specifically, the outlet port PT3 of the diluter
4 locating in a former stage is connected with the sample gas
introducing port PT4 of the diluter 4 locating in a later stage so
that dilution can be conducted in plural stages. As a result, the
dilution ratio can be changed in compliance with an order by
selecting which outlet port PT3 is to be used.
[0077] In accordance with the diluting system 4A of this
embodiment, it is possible to adjust the dilution ratio easily so
that the high-precision soot detector can maintain appropriate mass
concentration of soot to exert its performance fully with
maintaining merits of the diluter 4, namely merits wherein the flow
path is prevented from being clogged with soot and free from
pulsation.
[0078] The soot detector 5 comprises, whose pattern diagram is
shown in FIG. 5, an electric charge imparting part 51 that imparts
electric charge to soot contained in the sample gas and an electric
charge measuring part 52 that measures electric charge of soot, and
continuously and real-time measures soot contained in the diluted
exhaust gas introduced as the sample gas.
[0079] The electric charge imparting part 51 is arranged on the
flow path 53 of the introduced diluted exhaust gas, and comprises a
positive electrode 511 and a negative electrode 512, wherein a
potential difference between the positive electrode 511 and the
negative electrode 512 is, for example, several thousands volt
(5000 through 7000 volt). Corona discharge is generated between the
positive electrode 511 and the negative electrode 512 due to its
potential difference and the soot particle in the diluted exhaust
gas is charged in proportion to its surface area as a result that
the diluted exhaust gas passes between the positive electrode 511
and the negative electrode 512. As an example is shown in FIG. 5,
the positive electrode 511 is in a thin shape of a pin type
locating at a center of the flow path 53, and the negative
electrode 512 is a cylindrical cancellous member arranged to
surround the positive electrode 511. The electric charge imparting
part 51 may have other arrangement, for example, the electric
charge is imparted by irradiating ultraviolet rays.
[0080] The electric charge measuring part 52 comprises a capturing
member 521 such as a metal plate arranged downstream of the
electric charge imparting part 51 in the flow path 53 and a current
detector 522 that measures a value of the current that soot
captured by the capturing member 521 flows and outputs soot
detecting signal showing its value. The value of the soot detecting
signal expresses a surface area of the soot particles because the
quantity of electric charge is proportional to a surface area of
the soot particles. In addition, since there is a predetermined
relational expression between the surface area of the soot
particles and the mass of the soot particles, the mass of the soot
particles, consequently concentration of soot in the diluted
exhaust gas can be calculated from the value of the detecting
signal.
[0081] However, what required finally is concentration of soot in
the exhaust gas prior to dilution, and it is necessary to grasp the
dilution ratio by the diluter 4 in addition to measured data of the
concentration of soot in the diluted exhaust gas in order to
measure the concentration of soot in the exhaust gas prior to
dilution.
[0082] Then in this embodiment, as shown in FIG. 1, it is so
arranged that a standard gas line 8 through which standard gas (for
example, air containing C.sub.3H.sub.8) whose hydrocarbon
concentration is known flows and the exhaust gas line can be
switched to be connected with the sample gas introducing port PT4
of the diluter 4, and the outlet port PT3 of the diluter 4 and the
exhaust gas line can be switched to be connected with the gas
introducing port PT1 of the SOF measuring system 2.
[0083] More specifically, connection of the standard gas line 8 and
the exhaust gas line with the sample gas introducing port PT4 can
be switched by providing a switch valve V2 on the piping L6 of the
standard gas line 8 to the sample gas introducing port PT4 of the
diluter 4. A standard gas source (such as a steel bottle) is
connected with an inlet of the standard gas line 8, a pressure
regulator 81 is arranged so that line pressure of downstream the
pressure regulator 81 can be kept at a constant value and a flow
instrument 82 is arranged so that flow of the standard gas
introduced into the sample gas introducing port PT4 can be
monitored.
[0084] A switch valve V3 is arranged on a connection piping L7 from
the outlet port PT3 of the diluter 4 with the gas introducing port
PT1 of the SOF measuring system 2, a switch valve V4 is arranged on
a connection pipe of the exhaust gas line with the gas introducing
port PT1, and either one of the outlet port PT3 of the diluter 4
and the exhaust gas line can be switched to be connected with the
gas introducing port PT1 by alternative selection of the switch
valves V3, V4.
[0085] In accordance with this arrangement, it is possible for
either one of the hydrogen flame ionization detector 24a and the
hydrogen flame ionization detector 24b to measure the hydrocarbon
concentration of the diluted standard gas by making the standard
gas diluted by the diluter 4 flow into the SOF measuring system 2
with an operation of the switch valves V3, V4. Then the dilution
ratio of the diluter 4 at that time can be obtained based on the
measured hydrocarbon concentration of the diluted standard gas and
the known hydrocarbon concentration of the standard gas, and then
the concentration of soot in the exhaust gas can be calculated
based on the dilution ratio and the concentration of soot in the
diluted exhaust gas.
[0086] Furthermore, in this embodiment, an information processing
unit, not shown in drawings, receives the soot detecting signal and
the hydrocarbon detecting signal output by the hydrogen flame
ionization detector 24a (24b) at a time when the diluted standard
gas is flowed, and outputs the concentration of soot automatically
calculated based on these values and the previously memorized known
concentration data of the standard gas to a display or the like. In
addition, each of the switch valves V2, V3, V4 is of an
electromagnetic drive type and driven to open or close by a valve
driving signal output by the information processing unit.
(4) Usage of the Exhaust Gas Analyzer
[0087] Next, one example of a method for measuring the
concentration of soot by making use of the exhaust gas analyzer 1
will be concretely explained. A case that the information
processing unit automatically measures the concentration of soot in
accordance with a program will be explained with reference to FIG.
6 and FIG. 7.
(Drawing Up an Analytical Curve)
[0088] First, the standard gas is introduced into the SOF measuring
system 2 through the diluter 4 by operating each of the switch
valves V2, V3, V4 to open or close with the valve driving signal
output to each of the switch valves V2, V3, V4 (FIG. 6: Step
S1).
[0089] The air introduced into the diluter 4 is kept at a
predetermined pressure by giving a driving signal to the pressure
regulator 7 (Step S2).
[0090] With this state kept, the hydrocarbon concentration in the
diluted standard gas is measured by the hydrogen flame ionization
detector 24a (24b) (Step S3).
[0091] The dilution ratio of the diluter 4 is calculated based on a
ratio of the hydrocarbon concentration in the diluted standard gas
to the hydrocarbon concentration in the standard gas prior to
dilution (Step S4), and the dilution ratio and the air pressure are
recorded in pairs (Step S5).
[0092] Next, a pressure of air introduced into the diluter 4 is
changed to set at a different value by changing a value of the
driving signal to the pressure regulator 7 (Step S6) and the step
S3 through the step S6 are repeated at plural times (n times) (Step
S7, S8).
[0093] An analytical curve between the pressure and the dilution
ratio (relative relationship) is drawn up based on a relationship
between values of the pressure measured at plural points and the
dilution ratio and then stored in a predetermined area of the
memory (Step S9).
(Soot Concentration Measurement)
[0094] First, the exhaust gas is introduced into the soot measuring
system 3 by operating each of the switch valves V2, V3, V4 to open
or close (FIG. 7: Step S10)
[0095] Because the concentration of soot in the exhaust gas is
unknown, the value of the driving signal to the pressure regulator
7 is changed with reference to a value of the soot detecting signal
from the soot detector 5 so that the pressure of the diluent gas
line 6 is set to be suitable for the soot concentration measurement
(Step S11, S12).
[0096] The dilution ratio at that time is calculated based on the
set value of the air pressure and the analytical curve (Step
S13).
[0097] The soot concentration in the diluted exhaust gas is
obtained by applying a predetermined relational expression stored
in the memory to the value of the soot detecting signal (Step
S14).
[0098] Finally, the concentration of soot in the exhaust gas is
calculated based on the concentration of soot in the diluted
exhaust gas and the dilution ratio (Step S15).
[0099] The method for measuring the concentration of soot is
mentioned above, and may be others, for example, the analytical
curve is not drawn up, the dilution ratio at the set value of the
pressure of the diluent gas at that time is calculated by the use
of the standard gas every time the concentration of soot is
measured and the concentration of soot is calculated based on the
dilution ratio.
[0100] In addition, all of the above-mentioned actions may be
operated manually by an operator, or a part of them may be
automatically operated and other may be operated manually.
[0101] As a result, in accordance with the exhaust gas analyzer 1,
it is possible to obtain the dilution ratio of the diluter 4 at a
time of soot measurement by the use of the standard gas at a time
prior to or after soot measurement and to calculate the
concentration of soot in the exhaust gas prior to dilution based on
the obtained dilution ratio and the concentration of soot in the
diluted exhaust gas detected by the soot detector with a simple
arrangement of a flow path wherein the piping is bifurcated from
the diluter 4 to be connected with the existing SOF measuring
system 2, the piping to connect the standard gas source is
connected with the diluter 4, or the switch valves V2, V3, V4 are
arranged on the piping.
[0102] In addition, since the dilution ratio can be easily adjusted
by the use of the dilution system 4A so that concentration of
varieties of exhaust gas becomes appropriate for the soot
detection, it is possible to measure the concentration of soot by
the use of the high-precision soot detector 5. In addition, a
possibility that the fluid path is clogged with soot can be avoided
as much as possible because of a merit of the diluter 4 of this
type, namely the simple fluid path. Furthermore, the diluted
exhaust gas can be sent out to the soot detector in a stable state
without fail because of a merit that the diluter 4 has no pulsation
that prevents the accurate concentration measurement.
[0103] Furthermore, since the hydrogen flame ionization detector
24a, 24b detects soot in a spike-like peak state, it is possible,
for example, to verify the concentration of soot measured by the
soot measuring system and to set up a standard of an optimum
dilution ratio based on its result.
[0104] The present claimed invention is not limited to the
above-mentioned embodiment. For example, the hydrocarbon detector
or the soot detector may utilize other principle, or the exhaust
gas line may introduce exhaust gas diluted by a full tunnel.
[0105] The diluter may have an arrangement of one stage, or of
three or more stages. The diluter is not limited to be of the
ejector type, and may be of other type such as a rotary pump
type.
[0106] Furthermore, the dilution ratio adjusting device may utilize
not only the pressure regulator but also a flow adjusting valve
such as a valve.
[0107] In addition, this diluting system may be used for diluting
or mixing other gas. Other arrangement may be variously modified
without departing from a spirit of the present claimed invention
such as the switch valve may be a three-way valve.
[0108] As mentioned above, the present claimed invention makes it
possible to continuously and high-precisely measure the
concentration of soot in exhaust gas with a simple and compact
arrangement, which facilitates research and development of an
internal combustion engine such as an automobile. In addition, it
is possible to change and adjust the dilution (mixing) ratio easily
as well as to stabilize quality of the diluted (mixed) gas free
from pulsation. As a result, the present claimed invention can be
broadly applied to a usage such as gas continuous measurement.
[0109] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *