Measuring and testing – Gas analysis
Reexamination Certificate
2000-12-04
2002-07-02
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
Reexamination Certificate
active
06412333
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an exhaust gas analyzing system.
DESCRIPTION OF THE PRIOR ART
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.
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.
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
.
Reference numeral
6
represents a mini-diluter which is coupled to the sampling flow path
4
. Reference numeral
4
A 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
4
A and a suction pump
8
are provided. Reference numeral
9
represents a dilution gas flow path provided in parallel with the sampling flow path
4
A. 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
4
A 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
4
A 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
).
Sampling flow path
4
A 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
4
A and the mass-flow controller
14
.
Reference numeral
19
represents a gas analyzing portion provided in a rear stage of the mini-diluter
6
, and a plurality of gas analyzers
19
a
to
19
n
, 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
19
a
to
19
n
are NDIR (non-dispersive infrared analyzer) for measuring CO and CO
2
, CLD (chemiluminescent analyzer) for measuring NO
x
, FID (flame ionization detector) for measuring THC (total hydrocarbon), and the like.
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.
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
4
A 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
4
A.
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
4
A with the pressure on the inlet side of the CFV
11
of the dilution gas flow path
9
and because the flow path
4
A 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,
4
A and
9
, ways of changing flow rates of the gas S and D flowing through both flow paths
4
A 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.
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
4
A. 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
.
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.
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
2
, NO
x
, and THC) are respectively measured by NDIR, CLD, FID, and the like.
In this case, mass M
x
of a component X before dilution is given by the following expression (1).
M
x
=C
xbag
×V
ex
×R×&rgr;
x
(1)
Where C
xbag
represents a measured concentration of the component X in the bag, V
ex
represents total volume of the exhaust gas, R
d
represents dilution rate, &rgr;
x
density of the component X.
The mass M
x
Adachi Masayuki
Inoue Kaori
Horiba Ltd.
Oppenheimer Wolff & Donnelly LLP
Wiggins David J.
Williams Hezron
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