U.S. patent application number 09/729474 was filed with the patent office on 2001-06-21 for exhaust gas analyzing system.
Invention is credited to Adachi, Masayuki, Inoue, Kaori.
Application Number | 20010003915 09/729474 |
Document ID | / |
Family ID | 18379448 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010003915 |
Kind Code |
A1 |
Inoue, Kaori ; et
al. |
June 21, 2001 |
Exhaust gas analyzing system
Abstract
The present invention provides an exhaust gas analyzing system
utilizing a mini-diluter method in which measurement accuracy of
the exhaust gas analyzing system can be evaluated by the system
itself. In the exhaust gas analyzing system, a sampling flow path
is connected to an exhaust gas flow path through which gas
exhausted from an engine flows to sample a portion of the exhaust
gas. The sampled exhaust gas is diluted with dilution gas
introduced through a dilution gas flow path which is connected in
parallel to the sampling flow path. A portion of the diluted
exhaust gas is stored in a sample bag. The diluted exhaust gas in
the sample bag is analyzed in a gas analyzing portion, wherein flow
rate of the exhaust gas is measured, trace gas with a known
concentration is introduced into the exhaust gas flow path upstream
from a connecting point located between the exhaust gas flow path
and the sampling flow path while monitoring flow rate of the trace
gas, diluted trace gas is analyzed in the gas analyzing portion,
and total mass of the trace gas calculated from a result of the
analysis is compared with total mass of the introduced trace gas to
evaluate measurement itself.
Inventors: |
Inoue, Kaori; (Minami-ku,
JP) ; Adachi, Masayuki; (Minami-ku, JP) |
Correspondence
Address: |
OPPENHEIMER WOLFF & DONNELLY LLP
500 NEWPORT DR
SUITE 700
NEWPORT BEACH
CA
92660
US
|
Family ID: |
18379448 |
Appl. No.: |
09/729474 |
Filed: |
December 4, 2000 |
Current U.S.
Class: |
73/23.2 |
Current CPC
Class: |
G01N 2001/388 20130101;
G01N 1/38 20130101; G01N 33/0018 20130101; G01N 1/2252 20130101;
G01N 2001/2264 20130101 |
Class at
Publication: |
73/23.2 |
International
Class: |
G01N 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 1999 |
JP |
11-345854 |
Claims
What is claimed is:
1. An exhaust gas analyzing system, comprising: a sampling flow
path connected to an exhaust gas flow path through which gas
exhausted from an engine flows to sample a portion of said exhaust
gas; a dilution gas flow path connected in parallel to said
sampling flow path, said dilution gas flow path diluting said
sampled exhaust gas with dilution gas to form a diluted exhaust
gas; a sample bag storing a portion of said diluted exhaust gas; a
gas analyzing portion analyzing said diluted exhaust gas in said
sample bag; wherein flow rate of said exhaust gas is measured; and
a trace gas with a known concentration introduced into said exhaust
flow path while monitoring flow rate of said trace gas, said trace
gas introduced into said exhaust flow path upstream from a first
connecting point, said first connecting point connecting said
exhaust gas flow path to said sampling flow path, said trace gas
forming diluted trace gas when mixed with said diluted exhaust gas
and said dilution gas, said diluted trace gas analyzed in said gas
analyzing portion; wherein total mass of said trace gas calculated
from a result of said analysis in said gas analyzing portion is
compared with total mass of said introduced trace gas to evaluate
said analysis of said diluted trace gas in said gas analyzing
portion.
2. The exhaust gas analyzing system of claim 1, further comprising:
a mini-diluter connected to said sampling flow path, said
mini-diluter comprising: a first critical flow venturi connected to
said sampling flow path; and a second critical flow venturi
connected to said dilution gas flow path.
3. The exhaust gas analyzing system of claim 2, further comprising
a pressure controller connected to said dilution gas flow path,
said pressure controller equalizing pressure on an inlet side of
said first critical venturi with pressure on an inlet side of said
second critical venturi.
4. The exhaust gas analyzing system of claim 3, further comprising:
a suction pump located downstream of said first critical flow
venturi and said second critical flow venturi; wherein said sample
bag is located downstream of said suction pump.
5. The exhaust gas analyzing system of claim 4, further comprising:
a mass-flow controller connected downstream of said suction pump;
and a three-way solenoid valve located downstream of said mass-flow
controller, said three-way solenoid valve located upstream of said
sample bag.
6. The exhaust gas analyzing system of claim 5, further comprising:
an overflow path connected at downstream of said suction pump and
upstream of said mass-flow controller.
7. The exhaust gas analyzing system of claim 6, wherein said gas
analyzing portion is located in a rear stage of said mini-diluter,
said gas analyzing portion having a plurality of gas analyzers in
parallel with each other in a flow path, and said flow path
connected to said three-way solenoid valve.
8. The exhaust gas analyzing system of claim 7, wherein said
plurality of gas analyzers are at least one of non-dispersive
infrared analyzers, chemiluminescent analyzers, and flame
ionization detectors.
9. The exhaust gas analyzing system of claim 8, wherein said
non-dispersive infrared analyzers measure CO and CO.sub.2, said
chemiluminescent analyzers measure NO.sub.x, and said flame
ionization detectors measure total hydrocarbon.
10. The exhaust gas analyzing system of claim 9, further
comprising: a flowmeter located upstream of said first connecting
point; a trace gas introducing path connected to said exhaust gas
flow path at a second connecting point, said second connecting
point located upstream of said first connecting point; a trace gas
source located upstream of said trace gas introducing path; and
another mass-flow controller, said another mass-flow controller
located downstream of said trace gas source, said another mass-flow
controller measuring and controlling flow rate of said trace
gas.
11. The exhaust gas analyzing system of claim 10, further
comprising: an arithmetic controller, said arithmetic controller
controlling said flowmeter, said mass-flow controller, and said
another mass-flow controller.
12. The exhaust gas analyzing system of claim 11, wherein said
arithmetic controller receives and output signal from said
flowmeter.
13. The exhaust gas analyzing system of claim 12, wherein total
mass of said trace gas calculated from a result of said analysis in
said gas analyzing portion is given by
M.sub.x=C.sub.xbag.times.V.sub.ex.times.R.t- imes..rho..sub.x, and
wherein total mass of said introduced trace gas is given by
M.sub.t=C.sub.t.times.V.sub.t.times..rho..sub.t.
14. The exhaust gas analyzing system of claim 9, further
comprising: a trace gas introducing path connected to said exhaust
gas flow path; a trace gas source located upstream of said trace
gas introducing path; and another mass-flow controller, said
another mass-flow controller located downstream of said trace gas
source, said another mass-flow controller measuring and controlling
flow rate of said trace gas; another three-way solenoid valve
having a first valve, a second valve, and a third valve; said first
valve of said another three-way solenoid valve coupled to said
three-way solenoid valve; said second valve of said another
three-way solenoid valve coupled to said exhaust gas flow path at a
third connecting point located upstream of said first connecting
point and downstream of said second connecting point; and said
third valve of said another three-way solenoid valve coupled to
said gas analyzing portion.
15. The exhaust gas analyzing system of claim 14, further
comprising: an arithmetic controller, said arithmetic controller
controlling said mass-flow controller and said another mass-flow
controller.
16. The exhaust gas analyzing system of claim 1, wherein said trace
gas is helium gas.
17. The exhaust gas analyzing system of claim 1, wherein said trace
gas is SF.sub.6.
18. The exhaust gas analyzing system of claim 1, wherein said trace
gas concentration is monitored after mixing with said exhaust gas
to determine flow rate of said exhaust gas for proportionally
controlling flow rate of a mass flow controller to that of said
exhaust gas.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an exhaust gas analyzing
system.
DESCRIPTION OF THE PRIOR ART
[0002] Currently, a CVS method (Constant Volume Sampling) is widely
used as a sampling method to measure mass of components in gas
exhausted from an engine of an automobile. A possibility of
insufficient accuracy is pointed out in measuring exhaust gas of a
ULEV (Ultra Low Emission Vehicle), a SULEV (Super Ultra Low
Emission Vehicle), and like when the CVS method is used.
[0003] A substitute for the above CVS method is a mini-diluter
method. In the mini-diluter method, a portion of the exhaust gas is
sampled instead of diluting the entire quantity of exhaust gas from
the engine. The sampled exhaust gas is diluted at a certain
dilution ratio, the diluted sample gas is gathered in a sample bag
by an amount proportional to a flow rate of the exhaust gas from
the engine, and the diluted sample gas in the sample bag is
analyzed.
[0004] FIG. 3 schematically shows an example of an exhaust gas
analyzing system for which the mini-diluter method is used.
Reference numeral 1 represents an engine of an automobile,
reference numeral 2 represents an exhaust gas flow path connected
to an exhaust pipe connected to the engine 1, and reference numeral
3 represents a flowmeter (digital flowmeter, for example) for
measuring a flow rate of the entire exhaust gas G flowing through
the exhaust gas flow path 2. Reference numeral 4 represents a
sampling flow path that is connected to the exhaust gas flow path 2
at a point 5 downstream from the flowmeter 3. A portion of the
exhaust gas G, which is sample gas S, flows through the sampling
flow path 4.
[0005] Reference numeral 6 represents a mini-diluter which is
coupled to the sampling flow path 4. Reference numeral 4A
represents a sampling flow path in the mini-diluter 6 in which a
CFV (critical flow venturi) 7 for defining flow rate of the sample
gas S flowing through the sampling flow path 4A and a suction pump
8 are provided. Reference numeral 9 represents a dilution gas flow
path provided in parallel with the sampling flow path 4A. A
pressure controller 10 and a CFV 11 is provided in the dilution
flow path for defining a flow rate of the dilution gas D. A
downstream side of the CFV 11 is connected to the CFV 7 by the
sampling flow path 4A at a point 12 which is between the CFV 7 and
the pump 8. The pressure controller 10 equalizes pressure on an
inlet side of the CFV 7 of the flow path 4A with pressure on an
inlet side of the CFV 11 of the dilution gas flow path 9. A
cylinder 13 containing dilution gas (e.g., nitrogen gas) is
provided upstream of the pressure controller 10 (more specifically,
outside the mini-diluter 6).
[0006] Sampling flow path 4A includes a sample bag 16 which is
provided downstream from the suction pump 8. A mass-flow controller
14 (MFC) includes a flow rate measuring portion and a flow rate
control valve. The mass-flow controller 14 measures and controls
the flow rate via a three-way solenoid valve 15 as a selector
valve. Reference numeral 17 represents an overflow flow path, and
the overflow path 17 is connected to a point 18 between the suction
pump 8 of the sampling flow path 4A and the mass-flow controller
14.
[0007] Reference numeral 19 represents a gas analyzing portion
provided in a rear stage of the mini-diluter 6, and a plurality of
gas analyzers 19a to 19n, for example, are provided in parallel
with each other in a flow path 20. The flow path 20 is connected to
the three-way solenoid valve 15. Exemplary gas analyzers 19a to 19n
are NDIR (non-dispersive infrared analyzer) for measuring CO and
CO.sub.2, CLD (chemiluminescent analyzer) for measuring NO.sub.x,
FID (flame ionization detector) for measuring THC (total
hydrocarbon), and the like.
[0008] Furthermore, reference numeral 21 represents an arithmetic
controller having a personal computer, for example. The arithmetic
controller performs computations based on output signals from the
flowmeter 3, mass-flow controller 14, and gas analyzing portion 19
and controls the entire exhaust gas analyzing system based on a
result of the computations.
[0009] For the exhaust gas analyzing system having the above
structure and for which the mini-diluter method is used, the
exhaust gas analysis is carried out as follows. Flow rate of the
exhaust gas G from the engine 1 is measured by the flowmeter 3 and
output from the flowmeter 3 is input into the arithmetic controller
21. Because the suction pump 8 in the mini-diluter 6 is operating,
a portion of the exhaust gas G, wherein a flow rate has been
measured, is taken in the sampling flow path 4 as the sample gas S.
The sample gas S flows through the flow path 4A of the mini-diluter
6 toward the suction pump 8. By operation of the suction pump 8,
the dilution gas D flows through the dilution gas flow path 9
provided in parallel with the flow path 4A.
[0010] In this case, because the dilution gas flow path 9 is
provided with the pressure controller 10 which equalizes the
pressure on the inlet side of the CFV 7 of the flow path 4A with
the pressure on the inlet side of the CFV 11 of the dilution gas
flow path 9 and because the flow path 4A and the dilution gas flow
path 9 are respectively provided with the CFVs 7 and 11 for
defining the flow rates of the gas S and D flowing through the flow
paths 4A and 9, ways of changing flow rates of the gas S and D
flowing through both flow paths 4A and 9 are equalized with each
other and a ratio between the flow rates is always constant. The
gas flows S and D merge with each other at a confluence 12, and the
sample gas S is diluted with the dilution gas D to a certain
consistency.
[0011] The diluted sample gas S flows through the suction pump 8 to
a downstream side of the pump 8, and a portion of the gas S flows
toward the three-way solenoid valve 15. Flow rate of the portion of
the gas S flowing towards the three-way solenoid valve is set by
the mass-flow controller 14 provided in the flow path 4A. Because
the three-way solenoid valve 15 allows the mass-flow controller 14
and the sample bag 16 to communicate with each other when the power
is turned off, the diluted sample gas S which has passed through
the mass-flow controller 14 is gathered in the sample bag 16. The
remainder of the diluted sample gas S is exhausted through the
overflow flow path 17.
[0012] An opening degree of the flow rate control valve of the
mass-flow controller 14 is controlled actively such that the flow
rate of the diluted sample gas S passing through the mass-flow
controller 14 is proportional to a flow rate of the exhaust gas G
flowing through the exhaust gas flow path 2. More specifically,
because the flow rate of the exhaust gas is measured by the
flowmeter 3 and the result of the measurement is input into the
arithmetic controller 21 as described previously, the arithmetic
controller 21 sends a control command to set the opening degree of
the flow rate control valve of the mass-flow controller 14 at a
predetermined value. Thus, the mass-flow controller 14 allows the
sample gas S to flow at a proportional flow rate to the flow rate
of the exhaust gas G.
[0013] When the predetermined sampling ends, power to the three-way
solenoid valve 15 is turned on, the sample bag 16 and the flow path
20 communicate with each other, the diluted sample gas S taken into
the sample bag 16 is supplied to the gas analyzing portion 19, and
concentrations of components to be measured contained in the
diluted sample gas S (e.g., CO, CO.sub.2, NO.sub.x, and THC) are
respectively measured by NDIR, CLD, FID, and the like.
[0014] In this case, mass M.sub.x of a component X before dilution
is given by the following expression (1).
M.sub.x=C.sub.xbag.times.V.sub.ex.times.R.times..rho..sub.x (1)
[0015] Where C.sub.xbag represents a measured concentration of the
component X in the bag, V.sub.ex represents total volume of the
exhaust gas, R.sub.d represents dilution rate, .rho..sub.x density
of the component X.
[0016] The mass M.sub.x of component X in the exhaust gas G before
dilution can be easily obtained because the measured concentration
C.sub.xbag of the component X in the bag, the total flow rate
V.sub.ex of the exhaust gas, the dilution rate R.sub.d, and the
density .rho..sub.x of the component X are respectively known.
According to the exhaust gas analyzing system for which the
mini-diluter method is used, the mass of the low-concentration
exhaust gas component can be accurately measured.
[0017] However, in the exhaust gas analyzing system for which the
mini-diluter method is used, it is essential to measure the flow
rate of the exhaust gas G in real time, and a large error may be
incorporated into the finally obtained mass of the component in the
exhaust gas because it depends on the measurement error of the flow
rate.
[0018] The present invention has been accomplished with the above
circumstances in view, and it is an object of the present invention
to provide an exhaust gas analyzer in which measurement accuracy of
the exhaust gas analyzing system utilizing a mini-diluter method
can be evaluated by the system itself.
SUMMARY OF THE INVENTION
[0019] To achieve the above object, in accordance with the present
invention, an exhaust gas analyzing system is provided. The exhaust
gas analyzing system comprises a sampling flow path connected to an
exhaust gas flow path through which gas exhausted from an engine
flows to sample a part of the exhaust gas. The sampled exhaust gas
is diluted with dilution gas introduced through a dilution gas flow
path connected in parallel to the sampling flow path. A portion of
the diluted exhaust gas is stored in a sample bag. The diluted
exhaust gas in the sample bag is analyzed in a gas analyzing
portion, wherein flow rate of the exhaust gas is measured, trace
gas with a known concentration is introduced into the exhaust gas
flow path on an upstream side from a connecting point between the
exhaust gas flow path and the sampling flow path while monitoring
flow rate of the trace gas. The diluted trace gas is analyzed in
the gas analyzing portion, and total mass of the trace gas
calculated from a result of the analysis is compared with total
mass of the introduced trace gas to evaluate measurement
itself.
[0020] In the exhaust gas analyzing system, the total mass of the
trace gas introduced into the exhaust gas flow is known. It is
possible to evaluate accuracy of the measurement itself by
comparing the total mass of the measured and calculated trace gas
(using the mini-diluter method) with the above known total mass. As
a result, reliability of the exhaust gas analyzing system for which
the mini-diluter method is used and which includes measurement of
the flow rate of the exhaust gas is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 schematically shows an example of a structure of an
exhaust gas analyzing system of the present invention.
[0022] FIG. 2 schematically shows another example of the structure
of the exhaust gas analyzing system of the present invention.
[0023] FIG. 3 schematically shows an example of a structure of an
exhaust gas analyzing system for which a mini-diluter method is
used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Embodiments of the present invention will be described by
reference to the drawings. FIG. 1 shows a first embodiment of an
exhaust gas analyzing system of the present invention. The exhaust
gas analyzing system is significantly different from the prior-art
exhaust gas analyzing system in that proper trace gas T with a
known concentration and a known flow rate is introduced upstream
from a point 5 that is for sampling gas from an exhaust gas flow
path 2 into a mini-diluter 6, diluted trace gas T is analyzed by a
trace gas analyzer provided in a gas analyzing portion 19, and
total mass of the trace gas T calculated from a result of the
analysis is compared with total mass of the above introduced trace
gas T to evaluate measurement itself.
[0025] In FIG. 1, reference numeral 22 represents a trace gas
introducing path for introducing the trace gas T into the exhaust
gas flow path 2. Trace gas introducing path 22 is connected to the
exhaust gas flow path 2 at a point 23. A cylinder 24 of He (helium
gas), which is the trace gas T and a mass-flow controller 25 for
measuring and controlling flow rate of the trace gas T are provided
upstream of the trace introducing path 22. The mass-flow controller
25 is controlled by an arithmetic controller 21, and the mass-flow
controller 25 outputs a detected flow rate measurement to the
arithmetic controller 21.
[0026] In addition to NDIR, CLD, and FID for measuring
concentrations of CO, CO.sub.2, NO.sub.x, and THC, the gas
analyzing portion 19 is provided with a mass spectrometer to
analyze the concentration of the gas (trace gas).
[0027] In the exhaust gas analyzing system with the above
structure, the exhaust gas G from the engine 1 flows through the
exhaust gas flow path 2 and is mixed with the trace gas T
introduced into the exhaust gas flow path 2 through the trace gas
introducing path 22. The flow rate of the trace gas T is controlled
to a constant value by the mass-flow controller 25 disposed in the
trace gas introducing path 22. The flow rate at this time is
monitored by the arithmetic controller 21.
[0028] The exhaust gas G and the trace gas T pass through the
flowmeter 3 and a portion of the exhaust gas G and trace gas T
flows into the sampling flow path 4 and the remainder is exhausted.
Output from the flowmeter 3 is sent to the arithmetic controller
21.
[0029] The sample gas S and the trace gas T that have flowed into
the sampling flow path 4 are diluted with dilution gas D in the
mini-diluter 6 and concentrations (concentrations in the bag) of
respective components after dilution are obtained by NDIR, CLD,
FID, the mass spectrometer, and the like in the gas analyzing
portion 19 similarly to the exhaust gas analyzing system shown in
FIG. 3. In this case, mass of the respective components (and also
the trace gas T) can be also obtained by the above expression
(1).
[0030] On the other hand, mass M.sub.t of the trace gas T
introduced into the exhaust gas flow path 2 through the trace gas
introducing path 22 is given by the following expression (2).
M.sub.t=C.sub.t.times.V.sub.t.times..rho..sub.t (2)
[0031] Where C.sub.t represents a concentration of the trace gas T
in introduction, V.sub.t represents total introduced volume of the
trace gas T, and .rho..sub.t represents density of the trace gas
T.
[0032] In theory, M.sub.x given by the expression (1) and M.sub.t
given by the expression (2) should be the same value with respect
to the trace gas T. Because M.sub.t can be obtained relatively
accurately, a difference between M.sub.x and M.sub.t can be
regarded as an indicator of correctness of the gas analysis for
which the mini-diluter 6 is used.
[0033] In accordance with the exhaust gas analyzing system
described above, the total mass of the trace gas T introduced into
the exhaust gas G is known. By comparing the total mass of the
trace gas T measured and calculated by using the mini-diluter
method with the above known total mass, it is possible to evaluate
accuracy of the measurement itself. As a result, reliability of the
exhaust gas analyzing system for which the mini-diluter method is
used and which includes measurement of the flow rate of the exhaust
gas is improved.
[0034] FIG. 2 shows a second embodiment of the present invention.
In this embodiment, flow rate of gas (mixture of exhaust gas G and
trace gas T) flowing through the exhaust gas flow path 2 is
measured from change from a concentration of the trace gas T before
mixing to the concentration after mixing. The flowmeter 3 is
removed from the exhaust gas flow path 2, one end of a flow path 27
is connected to a point 26 between a connecting point 23 and a
connecting point 5 of the exhaust gas flow path 2, and the other
end of the flow path 27 is connected to a three-way solenoid valve
28 provided in a flow path 20.
[0035] In the structure shown in FIG. 2, sampling into the sample
bag 16 is carried out while the concentration of the trace gas T in
gas sampled from the connecting point 26 is measured in the gas
analyzing portion 19. Flow rate of the exhaust gas G is calculated
from the concentration of the trace gas after mixing in real time
and fed back to the sampling flow rate into the sample bag 16.
After sampling into the sample bag 16 is completed, it is possible
to evaluate measurement accuracy similarly to the above first
embodiment by analyzing components (including the trace gas T) in
diluted gas obtained by the sampling. In other words, because the
trace gas T is used for measuring the flow rate of the exhaust gas
G in the embodiment shown in FIG. 2, it is possible to omit the
flowmeter which measures the flow rate of the exhaust gas G.
[0036] The present invention is not limited to the above respective
embodiments. For example, other chemically stable components such
as SF.sub.6 can be used as the trace gas T. When SF.sub.6 is used
as the trace gas T, an FTIR method gas analyzer using Fourier
transform infrared spectrophotometer, for example, can be used to
analyze the concentration of SF.sub.6 as an alternative to NDIR.
Only by the FTIR method gas analyzer, CO, CO.sub.2, NO, and
H.sub.2O (which are main components of the engine exhaust) and
NO.sub.2, N.sub.2O, NH.sub.3, HCHO, and CH.sub.4 (which are of
great interest) can be measured simultaneously. Furthermore, the
structure of the gas analyzing portion 19 can be simplified.
[0037] The structure for defining the flow path in the mini-diluter
6 is not limited to the CFV, and a flow rate controller such as
mass flow controller can be used.
[0038] As described above, in the exhaust gas analyzing system of
the present invention, because measurement accuracy of the exhaust
gas analyzing system utilizing the mini-diluter method can be
evaluated by the system itself, reliability of the exhaust gas
analyzing system utilizing the mini-diluter method and which
includes measurement of the flow rate of the exhaust gas can be
improved.
* * * * *