JPH095299A - Pm measurement device in exhaust gas - Google Patents

Abstract

PURPOSE: To enable high precision measurement for PM(particulate material) in exhaust gas by measuring soot contained in the gas exhausted from an internal combustion engine with a flame ionization detector(FID). CONSTITUTION: Sample gas S taken in a sampling channel 6 of exhaust gas G from a diesel engine 2 is so branched into the first branch gas channel 7 and the second branch gas channel 8 to flow, and then the sample gas S flowing in the first branch gas channel 7 is, through a dummy 12, supplied directly to the first FID 9. Meanwhile, the sample gas S flowing in the second branch gas channel 8 is, through a filter device 10, supplied to the second FID 11 with no PM contained. Analysis is done in the first FID 9 and the second FID 11, and the results are inputted to a calculation part 13. Then concentration of the PM contained in the sample gas S is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to P contained in gas discharged from an internal combustion engine such as a diesel engine.
The present invention relates to a PM measuring device in exhaust gas for quantitatively analyzing M (Particulate Matter, particulate matter such as soot).

[0002] The PM is defined by the filter weight method as follows. That is, the engine exhaust gas is diluted with air to 52 ° C. or lower using a dilution tunnel, cooled, and collected on a filter using a fluorocarbon-coated glass fiber filter or a membrane filter capable of collecting 95% or more of 0.3 μm standard particles. The sum of the solid or liquid particles thus obtained is referred to as PM. And after collection, temperature 25 ℃,
The weight after being left in an atmosphere of 60% humidity for 8 hours or more is referred to as the weight of PM.

[0003] The PM is dissolved in an organic solvent and is mainly a hydrocarbon component such as SOF (Soluble Or).
ganic fraction) and ISF (Insol)
and the ISF includes dry soot (hereinafter, referred to as a carbon component) which is mainly a carbon component.
Soot), sulfate and moisture. Note that, regarding the measurement and analysis of PM, for example, the teaching materials of the Japan Opportunity Society (No. 95-29) workshop ('95.
6.1-2, Tokyo, Measuring technology for improving combustion and emission of internal combustion engines) "Measurement and analysis of particulate matter" [Japan Automotive Research Institute Hitoshi Yamazaki].

[0004]

2. Description of the Related Art By the way, the above-mentioned filter weight method uses P
The filter on which M has been attached and collected is measured using a precision balance, and so-called continuous measurement cannot be performed. On the other hand, as a method for continuously measuring PM in exhaust gas, a microbalance method (TEOM method) that detects a mass change in a filter when collecting PM as a change in bending resonance frequency of a pipe or the like, , CO ₂ laser photoacoustic method (PA
S method) or PM collected on the roll-shaped filter is burned by a CO ₂ laser, and the generated CO ₂ , H ₂ O, and SO ₂ are measured, and SO
A roll-type filter oxidation method for calculating and quantifying F, Soot and SO ₄ and an EDM method for detecting a change in conductivity corresponding to a change in charged Soot particle concentration in an electric field have been proposed.

[0005]

However, in any of the above-mentioned methods, if the difference in fuel or the operating condition changes, the exhaust gas condition changes, so that the correlation with the filter weight method may deteriorate. Problem with PM
At present, the method is not established as a measurement method.

By the way, conventionally, as a quantitative analysis of HC such as total hydrocarbons (Total Hydro-Carbon) in a sample gas, a hydrogen flame ionization detector (Flame Ionizatio) as shown in FIG. 3 has been used.
n Detector (hereinafter, referred to as FID) 30 is known. That is, in FIG. 3, 31 is a combustion chamber in which a nozzle 32 and a collector electrode 33 are provided. Further, 34 is a sample gas supply path for supplying the sample gas S, 35 is a fuel gas supply path for supplying the fuel gas F consisting of only hydrogen gas or hydrogen gas and other combustible gas, both gas supply pipes 34 and 35 are integrally connected to the nozzle 32 on the upstream side of the nozzle 32. Reference numeral 36 denotes an auxiliary combustion gas supply passage for supplying the auxiliary combustion air A, the end of which is open-connected at an appropriate point in the combustion chamber 31.

The nozzle 32 is connected to a high voltage DC power source (not shown) through a high voltage wiring 37, and the collector electrode 3
3 is connected to a signal processing circuit (not shown) via a signal line 38. Reference numeral 39 is an ignition device provided above the interior of the combustion chamber 31, 40 is an exhaust port, and 41 is an insulating sleeve.

In the FID 30 having the above structure, for example, the sample gas S containing the HC component is introduced into the combustion chamber 31 together with the fuel gas F and the auxiliary combustion air A, and the ignition device 39 causes, for example, a discharge spark to be generated. A desired flame 42 is formed at the tip of the nozzle 32.
The chemical ionization of HC is caused by the energy of the gas, and a current output proportional to the amount of hydrocarbon HC contained in the sample gas S is output via the signal line 38, whereby the concentration of HC in the sample gas S is analyzed. You can

By the way, as described above, PM contained in the exhaust gas from the diesel engine is mainly SOF which is a hydrocarbon component and So which is a carbon component.
According to the conventional thinking, the FID30
According to some, it was not possible to detect the carbon component.

However, according to the research conducted by the inventors of the present application, F, which has been conventionally used for the analysis of HC components,
It has been found that ID30 can detect not only HC but also C (carbon).

That is, FIG. 4 shows the combustion chamber 3 of the FID 30.
FIG. 3 is a diagram for explaining a process of generating thermionic ions in the inside of FIG. 1, and the high voltage DC power supply 43 provided between the nozzle 32 and the collector electrode 33 causes +30 to the nozzle 32, for example.
When a discharge spark is generated by the ignition device 39 with a voltage of 0 V applied, a high temperature flame 42 of 1500 K, for example, is formed at the tip of the nozzle 32.

At this time, the inventors presume that the soot contained in the sample gas S containing carbon (graphite) as a main component is detected for the following reason. That is, under the high temperature as described above, the soot emits electrons by thermal energy and thermal ionization may be performed. At this time, the energy for ionizing graphite is 4.5 eV (103.7 kcal /
mol). Originally, graphite has a specific resistance of 4 × 10 ⁻⁵ Ω · cm and is a semiconductor, but it is considered that it is relatively easily charged graphite when it receives energy of the above-mentioned magnitude. It is estimated that the electrons emitted by this ionization are collected in the nozzle 32 so that the graphite as the C component can be detected.

FIG. 5 shows an actual measurement example showing the response of the FID 30 to graphite.

The present invention has been made on the basis of the above-mentioned matters and findings, and is a novel one capable of continuously and accurately quantitatively analyzing PM contained in a gas discharged from an internal combustion engine such as a diesel engine. It is an object of the present invention to provide a useful PM measuring device in exhaust gas.

[0015]

In order to achieve the above object, the PM measuring apparatus for exhaust gas according to the present invention is characterized in that Soot contained in a gas discharged from an internal combustion engine is measured by a hydrogen flame ionization detector. I am trying to.

One of more specific PM measuring devices in exhaust gas is that a sample gas flow path in which gas discharged from an internal combustion engine flows as a sample gas at a constant volume is branched into two parallel gas flow paths. A first hydrogen flame ionization detector is provided in the first branch gas flow channel, a filter device for collecting PM contained in the sample gas is provided in the second branch gas flow channel, and a downstream side of the filter device is provided. Is provided with a second hydrogen flame ionization detector, and the PM concentration in the sample gas is obtained based on the difference between the signals output from the both hydrogen flame ionization detectors.

In another specific PM measuring apparatus for exhaust gas, a sample gas flow path in which a gas discharged from an internal combustion engine flows as a sample gas in a constant volume is formed into three parallel gas flow paths. A first hydrogen flame ionization detector is provided in the first branch gas flow channel, and the second branch gas flow channel and the third branch gas flow channel have characteristics of collecting PM contained in the sample gas. Filter devices different from each other are respectively provided, and a second hydrogen flame ionization detector and a third hydrogen flame ionization detector are respectively provided on the downstream side of these filter devices, and the first hydrogen flame ionization detector and the second hydrogen flame ionization detector are provided.
Sample based on difference between hydrogen flame ionization detector, difference between third flame flame ionization detector and second flame flame ionization detector, difference between first flame flame ionization detector and third flame flame ionization detector It is configured to obtain the PM concentration, the SOF concentration, and the Soot concentration in the gas, respectively.

In the other PM measuring device in exhaust gas, it is necessary to use a plurality of filter devices, and it is necessary to make the PM trapping characteristics different from each other. Different temperatures of the filter devices, b. Different filter materials, c. The roughness of the filter is different, d. This can be realized by changing the speed at which the sample gas S passes through the filter device, or by changing the speed.

[0019]

As described above, in the present invention, a plurality of FIDs can be used to obtain the PM concentration in the sample gas, as well as the SOF concentration and the Soot concentration, based on the difference between the outputs of the two FIDs.

According to the present invention, the PM concentration in exhaust gas from an internal combustion engine such as a diesel engine can be continuously obtained. As shown in FIG. 6, the measurement result according to the present invention has a good correlation with the result measured by the filter weight method, and a highly accurate measurement can be expected.

[0021]

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

FIG. 1 schematically shows the structure of a PM measuring apparatus for exhaust gas according to the first embodiment of the present invention. In this figure, 1 is an exhaust pipe 3 connected to a diesel engine 2. In the dilution tunnel, the dilution air DA is supplied from the upstream side through the filter 4 and the constant flow rate sampling device (CVS) 5 including the suction pump is provided on the downstream side.
Is provided. The exhaust tunnel G for diluting the diesel engine 2 is diluted by the diluting tunnel 1 to an appropriate ratio and flows at a constant flow rate. Reference numeral 6 denotes a sampling flow path connected to the dilution tunnel 1 between the exhaust pipe 3 and the CVS 5, and the diluted gas G flows as a sample gas S at a constant flow rate.

The sampling channel 6 has its downstream side branched into two gas channels 7 and 8. One of the gas flow paths 7 (hereinafter referred to as the first branch gas flow path 7) has the same structure as in
While the FID 9 (hereinafter, referred to as the first FID 9) similar to that shown in FIG. 1 is provided, PM in the sample gas S is collected in the other gas channel 8 (hereinafter, referred to as the second branched gas channel 8). Along with the filter device 10, a FID 11 (hereinafter referred to as a second FID 11) similar to that shown in FIG. 3 is provided on the downstream side of the filter device 10.

The filter device 10 is provided with a filter made of, for example, quartz or fluororesin having a small amount of impurities in the filter holder. The temperature of the filter device 10 is maintained at 52 ° C., for example. Further, 12 is a dummy placed on the first branch gas channel 7 to make the volumes of the first branch gas channel 7 and the second branch gas channel 8 the same, and has the same volume as the filter device 10. Yes, with no built-in filter.

13 is the first FID 9 and the second FID
Signals a and b respectively output from 11 are input, and an arithmetic unit that takes the difference between them is, for example, a microcomputer.

Explaining the operation of the PM measuring apparatus in the exhaust gas having the above-mentioned structure, the exhaust gas G from the diesel engine 2 is appropriately diluted in the dilution tunnel 6, and the diluted gas G is used as the sample gas S in the sampling channel. 6
A constant flow rate is taken in. In this case, the temperature of the sample gas S taken into the sampling channel 6 is adjusted so that its temperature becomes 191 ° C.

The sample gas S taken into the sampling channel 6 branches into the first branch gas channel 7 and the second branch gas channel 7, and flows through the first branch gas channel 7 to the sample gas S. S is the first FID as it is after passing through the dummy 12.
9. On the other hand, the sample gas S flowing through the second branched gas channel 8 passes through the filter device 10 and the second FID1.
However, when passing through the filter device 10, PM contained therein is collected and supplied to the second FID 11 without containing PM.

Then, the first FID 9 and the second FID 1
In No. 1, the analysis is performed in the same manner as the FID 30 shown in FIG. 3, and from the first FID 9, the signal a (= hc + p) which is the total amount of the concentration of HC (hc) and the concentration of PM (pm) is obtained.
m) is output, and the concentration of HC (h
The signal b (= hc) representing only c) is output, and the calculation unit 1
Input to 3. Then, in this calculation unit 13,
By performing the calculation (ab), the sample gas S
The concentration s of PM contained therein can be obtained.

Next, FIG. 2 schematically shows the structure of a PM measuring device in exhaust gas according to the second embodiment of the present invention. In this figure, the same parts as those shown in FIG. Showing the thing. In this embodiment, the downstream side of the sampling flow path 6 is branched into three gas flow paths 7, 8 and 14. The configurations of the first branch gas channel 7 and the second branch gas channel 8 are the same as those in the first embodiment,
In the third branch gas flow passage 14, the filter device 15 and the third F
ID16 is provided in this order.

The filter device 15 has the same structure as that of the filter device 10, but the temperature thereof is adjusted to 191 ° C. Also, the third FI
For D16, an FID having the same configuration as the first FID 9 and the second FID 11 is used.

Explaining the operation of the PM measuring apparatus in the exhaust gas having the above-mentioned structure, the exhaust gas G from the diesel engine 2 is appropriately diluted in the dilution tunnel 6, and the diluted gas G is used as the sample gas S in the sampling flow path. 6
A constant flow rate is taken in. In this case, the temperature of the sample gas S taken into the sampling channel 6 is adjusted so that its temperature becomes 191 ° C.

The sample gas S taken into the sampling channel 6 branches into the first branch gas channel 7, the second branch gas channel 7 and the third branch gas channel 14, and flows into the first branch gas channel 7. The sample gas S flowing through the gas channel 7 is the dummy 1
It is supplied to the first FID 9 through 2 as it is. And
The sample gas S flowing through the second branched gas flow path 8 is supplied to the second FID 11 through the filter device 10. However, when passing through the filter device 10, PM contained therein is collected, and the PM is not contained. It is supplied to the second FID 11. Further, the sample gas S flowing through the third branch gas flow path 14 is supplied to the third FID 16 through the filter device 15, but when passing through the filter device 15, the soot contained therein is collected, and the soot is collected from PM. It is supplied to the third FID 16 in the removed state.

The first FID9, the second FID11 and the third FID16 are analyzed respectively, and from the first FID9, the concentration of HC (hc) and the concentration of PM (p) are calculated.
m) is output as a signal a (= hc + pm), the second FID 11 outputs a signal b (= hc) representing only HC concentration (hc), and the third FID 16 outputs HC concentration (hc). And a signal c (= hc + sof), which is the sum of the SOF concentration (sof), is output, and the calculation unit 13
Is input to

Then, in the arithmetic unit 13, (a-
By performing the calculation b), the concentration s ₁ (= s) of PM contained in the sample gas S can be obtained, and (c
By performing the calculation of −b), the SOF concentration s ₂ contained in the sample gas S can be obtained, and (ac)
The Soot concentration s ₃ can be obtained by performing the following calculation.

In the second embodiment described above, the temperatures of the filter devices 10 and 15 are made different from each other so that the PM trapping characteristics of the filter devices 10 and 15 are made different. Alternatively, the materials of the filters may be different from each other, the roughness of the filters may be different, or the speed at which the sample gas S passes through the filter device may be different.

[0036]

As described above, according to the present invention, the PM concentration in exhaust gas from an internal combustion engine such as a diesel engine can be continuously obtained. Also,
According to the invention of claim 3, P in the exhaust gas
The concentration of M can be continuously obtained by distinguishing between Soot and SOF.

Further, according to the present invention, the correlation with the result measured by the filter weight method is good, and the measurement result with high accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a PM measuring device in exhaust gas according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a PM measuring device in exhaust gas according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an example of a hydrogen flame ionization detector used in the present invention.

FIG. 4 is a diagram for explaining a process of generating hot ions in a combustion chamber of the hydrogen flame ionization detector.

FIG. 5 is a diagram showing an actual measurement example showing the response to graphite in the hydrogen flame ionization detector.

FIG. 6 is a diagram showing a correlation between the measurement result according to the present invention and the result measured by the filter weight method.

[Explanation of symbols]

2 ... Internal combustion engine, 6 ... Sample gas flow path, 7 ... First branch gas flow path, 8 ... Second branch gas flow path, 9 ... First hydrogen flame ionization detector, 10, 15 ... Filter device, 11 ... 2 hydrogen flame ionization detector, 14 ... 3rd branch gas flow path, 16 ... 3rd hydrogen flame ionization detector, G ... Exhaust gas, S ... Sample gas.

Claims (3)

[Claims] 1. An apparatus for measuring PM in exhaust gas, wherein Soot contained in gas discharged from an internal combustion engine is measured by a hydrogen flame ionization detector. 2. A sample gas flow path in which a gas discharged from an internal combustion engine flows as a sample gas in a constant volume is branched into two gas flow paths parallel to each other, and a first hydrogen flame ionization is provided in the first branch gas flow path. A detector is provided, a filter device for collecting PM contained in the sample gas is provided in the second branched gas flow path, and a second hydrogen flame ionization detector is provided downstream of the filter device. An apparatus for measuring PM in exhaust gas, wherein a PM concentration in a sample gas is obtained based on a difference between signals output from hydrogen flame ionization detectors. 3. A sample gas flow passage in which a gas discharged from an internal combustion engine flows as a sample gas at a constant volume is branched into three gas flow passages parallel to each other, and a first hydrogen gas ionization is provided in the first branch gas flow passage. A detector is provided, and filter devices having different characteristics for trapping PM contained in the sample gas are provided in the second branch gas flow path and the third branch gas flow path, respectively, and downstream of these filter devices. A second hydrogen flame ionization detector and a third hydrogen flame ionization detector are respectively provided in the first flame flame ionization detector and the second hydrogen flame ionization detector.
Sample based on difference between hydrogen flame ionization detector, difference between third flame flame ionization detector and second flame flame ionization detector, difference between first flame flame ionization detector and third flame flame ionization detector An apparatus for measuring PM in exhaust gas, wherein PM concentration, SOF concentration, and Soot concentration in gas are respectively obtained.