JPH1038850A - Measuring instrument for pm in exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain measurement by means of discriminating of a THC concentration and a Soot concentration by collecting samples from gas to be exhausted from a combustion engine, introducing them into a hydrogen frame ion detector(FID), and performing processing corresponding to characteristics of that detection signal. SOLUTION: A part of an exhaust gas G from a diesel engine flowing an air exhaust tube 2 is taken up as a sample gas S in a sample gas flow path 3 via a probe 4 and is introduced into a combustion chamber 21 together with an fuel gas F and an auxiliary combustion air A. When a frame 32 is formed at a tip end of a nozzle 22 by an ignition device 29, ionization of hydrogen carbon is generated by energy of the frame 32. An FID 5 outputs an FID signal having two components proportional to quantities of THC(total hydrogen carbon) and Soot (carbon component) contained in the sample gas S to a signal line 6. The FID signal is inputted to a signal processor 8 via a preamplifier 7, processing corresponding to the characteristics of both components is performed, and both components are separated. With this method, THC and Soot are differentiated from each other, and quantitative analysis is precisely made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring PM in exhaust gas for quantitatively analyzing PM (Particulate Matter, particulate matter such as soot) contained in gas discharged from an internal combustion engine such as a diesel engine.

[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. For the measurement and analysis of PM, for example, Japanese Society of Mechanical Engineers (No. 95-29) training materials ('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 of continuously measuring PM in exhaust gas, there is a carbon balance method. The configuration of the PM measuring apparatus using the carbon balance method will be described with reference to FIG.

In FIG. 9, reference numeral 41 denotes a gas flow path through which exhaust gas (sample gas SG) from a diesel engine (not shown) flows, and is divided into two flow paths 43 and 44 at a point 42 on the downstream side thereof. . One channel 43 is
A filter 46 having a built-in collection filter 45 for collecting PM in the sample gas S and a heating combustion furnace 47 are provided, and are configured as a reference gas flow path.
The other flow path 44 includes a dummy filter 48 having no filter for making the dead volume the same as the reference gas flow path 43, and a heating combustion furnace 49 configured similarly to the heating combustion furnace 47. And is configured as a sample gas flow path.

Numeral 50 denotes a gas analyzer of a fluid modulation type, which comprises a gas analyzer 51, a sample gas SG from a sample gas flow path 44, and a reference gas RG from a reference gas flow path 43 alternately in a predetermined amount. And a gas supply unit 52 that supplies the gas at a time. That is, the gas analyzer 51 arranges the two cells 53 and 54 in parallel, and
The infrared light sources 55 and 56 are arranged on one side of each of the cells 4, and the CO ₂ detector 57 and the H _{2 made of} , for example, a condenser microphone type detector are arranged on the other side of the cells 53 and 54.
_{A 2} O detector 58 is optically arranged in series.

When the reference gas RG is supplied to one of the cells 53 by a partition plate 59 which is rotated by a motor (not shown), the gas supply section 52 comprises, for example, a rotary valve.
Is supplied with the sample gas SG, and one cell 53
When the sample gas SG is supplied to the other cell 54, the reference gas RG is supplied to the other cell 54.
The gas SG and the RG are switched and supplied at a constant cycle.

[0008] The basic principle of the fluid modulation type gas analyzer is described in detail in Japanese Patent Publication No. 56-48822 by the present applicant.

In the PM measuring apparatus having the above structure, a part of the sample gas SG flowing through the gas flow path 41 is divided into a reference gas flow path 43 at a point 42 and
When passing through 6, the contained PM is removed to become a reference gas RG, which is introduced into the heating combustion furnace 47. Then, the remaining sample gas SG is directly introduced into the heating combustion furnace 49 via the Dummy filter 48 as it is.

The insides of the heating furnaces 47 and 49 are heated to, for example, about 1000 ° C., and CO and HC components are oxidized (combusted) to CO ₂ and H ₂ O. After that, the combustion gas in both gas passages 43 and 44 is supplied to the sample gas SG and the reference gas R
G is alternately supplied to the cells 53 and 54 alternately.

A light source 5 is connected to the cells 53 and 54.
By irradiating infrared light from 5, 56, cells 53,
The infrared light passing through 54 receives a predetermined absorption in the cells 53 and 54, and then receives the CO ₂ detector 57 and the H ₂ O detector 5.
8 is incident. At this time, the magnitudes of the signals obtained from the two detectors 57 and 58 are proportional to CO ₂ and H ₂ O in the sample gas SG and the reference gas RG, and are obtained as a difference. That is, the CO ₂ detector 57
And the output of the H ₂ O detector 58 becomes the PM concentration.

[0012]

As described above, according to the carbon balance method, PM contained in exhaust gas from a diesel engine or the like can be continuously determined, but there are the following problems. . That is, the reference gas passage 43 and the sample gas passage 44
It is difficult to measure with high-speed response due to the noise caused by the flow resistance difference in. The measurement of CO ₂ and H ₂ O using infrared light has many interference components and is likely to cause errors. It is necessary to use a detector of hitting lid in order to detect the two components of the CO ₂ and H ₂ O. The coexisting base gas is CO ₂ and H ₂
Since it is the same as O, it is difficult to increase the sensitivity. In order to measure the same sample gas with a plurality of detectors 57 and 58, it is necessary to synchronize the signals. However, it is difficult to eliminate an error caused by the synchronization.

[0013] Conventionally, as a method for quantitatively analyzing HC such as total hydrocarbons (Total Hydro-Carbon, hereinafter referred to as THC) in a sample gas, a flame ionization detector (Flame) shown in FIG.
e Ionization Detector,
FID) 20 are known. That is, in FIG. 6, reference numeral 21 denotes a combustion chamber, in which a nozzle 22 is provided;
A collector electrode 23 is provided. Reference numeral 24 denotes a sample gas supply path for supplying the sample gas S, 2
Reference numeral 5 denotes a fuel gas supply path for supplying a fuel gas F composed of only hydrogen gas or hydrogen gas and another combustible gas. Both gas supply pipes 24 and 25 are integrated with the nozzle 22 on the upstream side of the nozzle 22 and It is connected. Reference numeral 26 denotes an auxiliary gas supply path for supplying auxiliary air A, and an end of the auxiliary gas supply path is opened and connected to an appropriate portion of the combustion chamber 21.

The nozzle 22 is connected to a high-voltage DC power supply (not shown) via a high-voltage wiring 27, and the collector electrode 23 is connected to a signal processing circuit (not shown) via a signal line 28. ing. Reference numeral 29 denotes an ignition device provided above the inside of the combustion chamber 21, reference numeral 30 denotes an exhaust port, and reference numeral 31 denotes an insulating sleeve.

In the FID 20 having the above structure, for example, the sample gas S containing the HC component is introduced into the combustion chamber 21 together with the fuel gas F and the auxiliary air A, and the ignition device 29 generates, for example, a discharge spark. A desired flame 32 is formed at the tip of the nozzle 22, and this flame 32
The thermal energy of HC is generated by the energy of the sample gas S, and a current output proportional to the amount of hydrocarbons HC contained in the sample gas S is output via the signal line 28, whereby the HC concentration in the sample gas S is analyzed. Can be.

As described above, PM contained in exhaust gas from a diesel engine mainly includes SOF, which is mainly a hydrocarbon component (HC), and Soo, which is mainly a carbon component (C). According to the above, it has been described that the carbon component cannot be detected depending on the FID 20.

However, according to the study of the inventor of the present application, the FI which has been conventionally used for the analysis of HC components has been disclosed.
It has been found that not only HC but also C (carbon) can be detected by D20.

FIG. 7 shows the combustion chamber 2 of the FID 20.
1 is a view for explaining a process of generating thermal ions in the nozzle 1, and a high voltage DC power supply 33 provided between the nozzle 22 and the collector electrode 23 supplies, for example, +30 to the nozzle 22.
When a discharge spark is generated by the ignition device 29 in a state where the voltage of 0 V is applied, a high-temperature flame 32 of, for example, 1500 K is formed at the tip of the nozzle 22.

At this time, the present 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 at which graphite is ionized is 4.5 eV (103.7 kcal / m).
ol). Originally, graphite has a specific resistance of 4
× 10 ⁻⁵ Ω · cm, which is a semiconductor, but is considered to be relatively easily charged graphite by receiving energy of the above magnitude. Then, it is presumed that graphite, which is a carbon component, can be detected by collecting electrons emitted by the ionization in the nozzle 22.

FIG. 8 shows an actual measurement example showing the responsiveness of the FID 20 to graphite.

The present invention has been made on the basis of the above-described matters and findings, and is a novel and novel method capable of continuously and accurately quantitatively analyzing PM contained in 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 (hereinafter, simply referred to as a PM measuring device).

[0022]

In order to achieve the above object, a PM measuring apparatus according to the present invention collects a gas discharged from an internal combustion engine as a sample gas, introduces the sample gas into a flame ionization detector, and obtains the sample gas. At this time, by performing signal processing corresponding to the characteristics of the signal obtained from the flame ionization detector, the THC concentration and the soot concentration are obtained separately.

Exhaust gas containing PM is passed through a filter without passing through a filter.
When directly introduced into the ID, the FID can be used as shown in FIG.
An FID signal f including a signal component a corresponding to THC and a signal component b corresponding to Soot as shown in FIG. In the FID signal f, the signal component b is a shot noise-like signal, unlike the signal component a called a trend. Then, both a and b can be discriminated by using a low-pass filter or a comparator.

According to the present invention, the PM concentration in the exhaust gas of a diesel engine or the like is determined by comparing the THC component with the soot.
The measurement can be performed simultaneously and at high speed in a state where the components are distinguished.

In the present invention, only one FID
, The configuration of the entire device is greatly simplified, and unlike the case where a plurality of FIDs are used, there is no need to synchronize signals.

At the time of sampling the exhaust gas, the temperature of the sample gas sampling point is measured. Based on the measured temperature and the measurement results of the THC concentration and the Soot concentration, the tertiary time, temperature, THC concentration and Soot concentration are determined. Original simultaneous measurement data may be obtained. In this case, the responsiveness of the measurement system is improved, and the THC is improved.
The temperature dependence of the amount and the temperature dependence of the soot generation can be measured simultaneously.

[0027]

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

FIG. 1 shows a PM according to a first embodiment of the present invention.
FIG. 1 schematically shows an example of a measuring apparatus, in which 1 is a diesel engine, 2 is an exhaust pipe connected to the diesel engine 1, and 3 is an exhaust gas G flowing through the exhaust pipe 2.
Is a sample gas flow path connected via a probe 4 for collecting a part of the sample gas as a sample gas S. The sample gas flow path 3 including the probe 4 can be controlled in temperature. Reference numeral 5 denotes an FID provided in the sample gas flow path, which is configured to be able to measure the exhaust gas G of the diesel engine 1 without diluting the same, and there is substantially no difference from that shown in FIG. Reference numeral 6 denotes a signal line of the FID 5, which is provided with a preamplifier 7 and an analog signal processing device 8.

The operation of the PM measuring apparatus configured as described above will be described with reference to FIGS. 1, 2 and 6. As shown in FIG. 1, a part of the exhaust gas G from the diesel engine 1 flowing through the exhaust pipe 2 is taken into the sample gas flow path 3 via the probe 4 as the sample gas S. As shown in FIG. 6, the sample gas S is supplied to the combustion chamber 2 together with the fuel gas F and the auxiliary air A.
1, a desired flame 32 is formed at the tip of the nozzle 22 by the ignition device 29, and thermal energy of HC is generated by the energy of the flame 32, and is proportional to the amounts of HC and Soot contained in the sample gas S. Current output (FID)
The signal f is output to the signal line 6.

The FID signal f is appropriately amplified and waveform-shaped by a preamplifier 7 and then processed by a signal processor 8.
Is input to This FID signal f is shown in FIG.
As shown in (A), a shot noise-like signal component b proportional to the amount of Soot is superimposed on a signal component a called a trend proportional to the amount of THC.
Then, in order to separate and discriminate such an FID signal f into two signal components a and b, signal processing corresponding to the characteristics of each of the signal components a and b may be performed.

For example, by providing a low-pass filter and a comparator in the signal processing device 8, the FID signal f can be separated into two signal components a and b. That is, the signal component a corresponding to THC can be distinguished by a low-pass filter having a long time constant, and the signal component b corresponding to Soot is determined to be shot noise based on the rising speed and height thereof. That is, a comparator that can be used is used.

The signal components a and b separated as described above correspond to the amounts of THC and Soot in the sample gas S, respectively, and are multiplied by a predetermined coefficient to obtain THC. And Soot concentrations can be obtained individually and simultaneously.

FIG. 2B shows an FID signal obtained when a filter 9 for trapping PM is provided in a stage preceding (upstream of) the FID 5 in the PM measuring apparatus shown in FIG. At that time, there is no soot and SO
Since a part of F is also collected, the signal component a ′ is smaller than the signal component a shown in FIG.

FIG. 3 shows a PM according to a second embodiment of the present invention.
This shows an example of the configuration of a measuring device. In this embodiment, when exhaust gas G is sampled, the temperature of the gas at the sampling point is measured. That is,
In FIG. 3, reference numeral 10 denotes a thermometer, and its sensor probe 1
1 is arranged in the exhaust pipe 2 near the probe 4. The output of the thermometer 10 is input to the signal processing device 8 via the preamplifier 12.

In the PM measuring apparatus according to the second embodiment, similarly to the PM measuring apparatus according to the first embodiment, the PM concentration in the exhaust gas G is measured simultaneously and at high speed in a state in which it is classified into the THC component and the Soot component. be able to. In addition, as shown schematically in FIG. 4, three-dimensional simultaneous measurement data of time t, temperature T, THC concentration, and soot concentration can be obtained. Therefore, in this embodiment, the response of the measurement system can be improved, and the temperature dependency of the THC amount and the temperature dependency of soot generation can be measured simultaneously.

In each of the above-described embodiments, the exhaust gas G of the diesel engine 1 is not diluted, and a part of the exhaust gas G is introduced into the FID 5 as the sample gas S. Instead, the exhaust gas G is appropriately diluted. Then, a sampling form to be introduced into the FID 5 may be adopted.

FIG. 5 shows an example in which the above-mentioned sampling mode is applied to the first embodiment. In FIG. 5, reference numeral 13 denotes a dilution tunnel connected to an exhaust pipe 14 connected to the diesel engine 1. Then, the dilution air DA is supplied from the upstream side through the filter 15, and the downstream side is provided with a constant flow rate sampling device (Const.
ant Volume Sampler, hereafter CVS
16) are provided. This dilution tunnel 1
3, the exhaust gas G from the diesel engine 1 is diluted at an appropriate magnification and flows at a constant flow rate. 17
Is the exhaust pipe 14 and the CVS 16 for the dilution tunnel 13.
The diluted gas G flows as a sample gas S at a constant flow rate in the sampling flow path connected between

In this case, it goes without saying that the concentrations of THC and Soot finally obtained are multiplied by a predetermined value in accordance with the dilution ratio, thereby obtaining the concentrations of THC and Soot in the exhaust gas G. This configuration may be applied to the second embodiment.

In each of the above embodiments, the signal processing device 8 is configured as an analog system. However, the present invention is not limited to this. The signal processing device 8 may be configured as a digital system. A computer can be used as the signal processing device 8.

[0040]

As described above, claims 1 and 2
In the invention described in the above, the PM concentration in the exhaust gas from an internal combustion engine such as a diesel engine is determined by using THC and Soo.
t, and quantitative analysis can be performed continuously, simultaneously, and accurately. In the present invention, unlike the related art, only one FID needs to be used without using a plurality of cells and detectors or providing a filter or the like in the sample gas flow path. The configuration is greatly simplified, and there is no need to synchronize signals, unlike when using multiple FIDs.

According to the second aspect of the present invention, in addition to the above effects, the response of the measurement system can be improved, and the temperature dependence of the THC amount and the temperature dependence of the soot generation are measured simultaneously. be able to.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory view of the PM measuring device.

FIG. 3 is a diagram schematically showing a configuration of a PM measuring device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an operation of the PM measuring device.

FIG. 5 is a diagram showing another mode of sampling.

FIG. 6 is a diagram showing an example of a flame ionization detector used in the present invention.

FIG. 7 is a diagram for explaining a process of generating thermal ions in a combustion chamber of the flame ionization detector.

FIG. 8 is a view showing an actual measurement example showing responsiveness to graphite in the flame ionization detector.

FIG. 9 is a diagram for explaining a conventional technique.

[Explanation of symbols]

1. Internal combustion engine, 5. Flame ionization detector (FID),
Reference numeral 8: signal processing device, 10: thermometer, G: exhaust gas, S: sample gas, a: THC concentration, b: Soot concentration, f:
FID signal.

Claims (2)

[Claims] 1. A gas discharged from an internal combustion engine is collected as a sample gas, introduced into a flame ionization detector, and signal processing corresponding to a characteristic of a signal obtained from the flame ionization detector is performed at that time. By the way, TH
An apparatus for measuring PM in exhaust gas, wherein a C concentration and a Soot concentration are obtained separately. 2. A gas discharged from an internal combustion engine is collected as a sample gas, a temperature of a sample gas sampling point is measured, and the sample gas is introduced into a flame ionization detector. Performs signal processing corresponding to the features in the signal obtained from
The concentration and the Soot concentration are obtained separately, and the time, temperature, THC concentration and Soh concentration are determined based on the measured temperature and the measurement results of the THC concentration and the Soot concentration.
An apparatus for measuring PM in exhaust gas, wherein three-dimensional simultaneous measurement data of ot concentration is obtained.